Dissertations / Theses on the topic 'Soil organic carbon. eng'

Resumo: O sequestro de carbono nos ambientes terrestres, sendo feito de forma natural pelos vegetais através da fotossíntese, cujo processo permite fixar o carbono nos solos e, em forma de matéria lenhosa nas plantas, vem sendo apontado como uma alternativa mitigadora das mudanças climáticas, segundo acordos internacionais como o Protocolo de Kyoto. A retirada da floresta nativa provoca a diminuição significativa da biomassa microbiana e da fertilidade do solo. A reserva de carbono na matéria orgânica do solo é uma importante estratégia para atenuar a concentração de CO2 na atmosfera. Com o reflorestamento dessas áreas ocorre uma recuperação lenta e contínua da quantidade e qualidade da matéria orgânica. O eucalipto é a essência florestal mais plantada no Brasil e essas plantações florestais com eucalipto poderão cumprir o papel de aumentar as concentrações de carbono orgânico no solo, recuperando estruturas perdidas quando da exportação da madeira através da colheita, bem como, provocando mudanças ambientais associadas. Este trabalho objetivou quantificar a fixação de carbono no compartimento do solo de 0 a 60 cm de uma floresta nativa em comparação com plantios de eucalipto com 3 diferentes idades: 0 a 1 ano (área recém implantada); 3 a 4 anos (metade do ciclo) e 6 a 7 anos (época de corte). Foram escolhidos quatro diferentes sítios de amostragem com uma área amostral de 1 ha cada. Foram coletadas amostras de solo no inverno e no verão a diferentes profundidades para que se pudesse conhecer a quantidade de carbono orgânico fixado ao longo do perfil do solo considerando o fator da sazonalidade. Os resultados indicam que o manejo nas áreas interferiu no acúmulo de carbono no solo dos quatro sítios estudados, mostrando também que o fragmento de Cerrado estoca menos carbono que os plantios de eucalipto. Quanto à sazonalidade, houve diferença significativa... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The carbon sequestration in terrestrial environments, by plants through photosynthesis, allows carbon fixing as a woody matter in plants. This process has been identified as an alternative to mitigate climate change, according to Kyoto Protocol, an international environmental agreement. The removal of the native forest causes a significant decrease of microbial biomass and soil fertility. The storage of carbon in soil organic matter is an important strategy to reduce the concentration of CO2 in the atmosphere. With the reforestation of these areas, occurs a slow and continuous recovery of the quantity and quality of organic matter. The eucalyptus is the most planted species in Brazil for industrial supply. These eucalyptus reforestations may fulfill the role of increasing soil organic carbon concentration, recovering some structures lost by wood harvesting and causing associated environmental changes. This study aimed to quantify the carbon fixation within the soil compartment from 0 to 60 cm depth of a native forest formation in comparison with eucalyptus plantations with 3 different ages: 0 to 1 year (newly planted area); 3 to 4 years (half the harvesting cycle) and 6 to 7 years (harvesting time). Four different sites were chosen for sampling, with a sampling area of 1 ha each. Soil samples were collected in winter and summer time, at different depths, to quantify the organic carbon fixed throughout the soil profile, considering the seasonality factor. The results indicate that management in each area interfered in the accumulation of carbon in the soil in the four sites studied. The savanna fragment stored less carbon than the eucalyptus plantations. Regarding seasonality, a significant difference was found between the accumulation of carbon in winter and summer... (Complete abstract click electronic access below)
Orientador: Iraê Amaral Guerrini
Coorientador: Vera Lex Engel
Banca: Dirceu Maximino Fernandes
Banca: Jacob Siva Souto
Mestre

Orientador: José Eduardo Corá
Banca: Álvaro Pires da Silva
Banca: Carolina Fernandes
Resumo: A adaptação do sistema de semeadura direta (SSD) depende da escolha adequada da seqüência de culturas, que devem contribuir para melhorar os atributos solo. O objetivo do presente trabalho foi avaliar o efeito de seqüências de culturas na agregação do solo e no teor de carbono orgânico e polissacarídeos em diferentes classes de agregados estáveis em água de um Latossolo Vermelho eutrófico sob SSD. Um experimento foi implantado em 2002 em Jaboticabal, SP. Os tratamentos foram constituídos pela combinação de quatro seqüências de culturas de verão e sete culturas de inverno. As seqüências de culturas de verão, semeadas em outubro/novembro, foram: monocultura de milho; monocultura de soja; cultivos intercalados ano a ano de soja e milho; seqüência de cultivos de arroz/feijão/algodão/feijão. As culturas de inverno, semeadas em fevereiro/março, repetidas todos os anos nas mesmas parcelas, foram: milho, girassol, nabo forrageiro, milheto, feijão guandu, sorgo granífero e crotalária. A amostragem do solo foi realizada após o quarto ano de condução do experimento, em outubro de 2006. O cultivo de milho em monocultura no verão favoreceu a formação de agregados estáveis em água com diâmetro entre 6,30-2,00 mm e proporcionou o maior teor de COT e PAD nessa classe de tamanho de agregados. Isso indica que a influência das culturas sobre a estabilidade de agregados foi intermediada pelos teores de COT e PAD. Não foi verificada diferença na agregação do solo entre culturas de inverno utilizadas. Os maiores teores de COT, PST e PAD foram verificados nos agregados com diâmetro entre 2,00-1,00 mm e os menores teores nos agregados <0,25 mm.
Abstract: A better performance of the no-tillage system in tropical regions depends on the choice of suitable crop sequences in summer and winter. These crops should contribute to improvement of soil properties. The objective of this work was to assess crop sequences effects on soil aggregation and organic carbon and polysaccharide contents in water-stable aggregate size classes of a Rhodic Oxisol under no-tillage. An experiment was established in Jaboticabal town, São Paulo state, in 2002. Treatments were constituted for a combination of four crop sequences in summer and seven crop sequences in the winter. Crop sequences in the summer were: corn monoculture (CC); soybean monoculture (SS); soybean/corn/soybean/corn sequence (SC) and rice/bean/cotton/bean sequence (RB), seeded in October/November. Winter crops were: corn, sunflower, oilseed radish, millet, pigeonpea, sorghum and sunn hemp, seeded in February/March. Soil sampling took place after forth year after experiment implantation, in October 2006. The MV sequence in summer increased the percentage of 6,30-2,00 mm water-stable aggregates and provided the highest total organic carbon and diluted-acid-extractable polysaccharides contents in the same aggregate size class. These results suggest that crop effects on soil aggregate stability can be mediated by total organic carbon and diluted-acid-extractable polysaccharides. The winter crops do not influence soil aggregation. The highest and lowest total organic carbon, total polysaccharides and diluted-acid-extractable polysaccharides contents was verified, respectively, in 2,00-1,00 mm and <0,25 mm water-aggregate soil size classes.
Mestre

Orientador: Jose Eduardo Cora
Coorientador: Carolina Fernandes
Banca: Isabella Clerici de Maria
Banca: Cimélio Bayer
Banca: Sandro Roberto Brancalião
Banca: Marcílio Vieira Martins Filho
Resumo: O presente trabalho teve como objetivo geral determinar como as plantas influenciam a estabilidade de agregados, a composição de carboidratos, o acúmulo de C orgânico do solo (COS) e de C microbiano em um Latossolo Vermelho. Na primeira parte do estudo, verificou-se que as sequências de culturas com milho (Zea mays L.) no verão e as milheto (Pennisetum glaucum (L.) Leeke) e sorgo granífero (Sorghum bicolor (L.) Moench) no inverno proporcionaram maior diâmetro médio ponderado (DMP) de agregados estáveis do solo. Assim como observado para o DMP, as sequências de culturas envolvendo milho no verão proporcionaram os maiores teores de xilose do solo. A menor proporção de carboidratos de origem microbiana em relação aos de origem vegetal foram observados com o cultivo mais frequente de espécies de monocotiledôneas. Na segunda parte do estudo, notou-se que os maiores valores de C presente como matéria orgânica particulada (C-MOP) do solo foram encontrados sob cultivo de guandu, o qual proporcionou valores 54%, 46% e 48% maiores em relação ao cultivo de milho, girassol e nabo forrageiro, respectivamente. As variações nos teores de C-MOP explicaram o efeito das culturas nos teores de COS. Notou-se um acúmulo conjunto de C-MOP e de resíduos fúngicos e bacterianos no solo. Na terceira parte do estudo, verificou-se que os materiais de monocotiledôneas adicionados ao solo apresentaram as maiores taxas de mineralização do compartimento de C não lábil (k), os maiores teores de pentose do solo e o maior DMP de agregados do solo em comparação à testemunha e às dicotiledôneas, em período posterior de decomposição. Isso sugere que k e teores de pentoses do solo controlam a estabilidade de agregados do Latossolo em período tardio de incubação. O efeito da decomposição dos materiais vegetais na agregação do solo ocorreu independente da variação da quantidade do teor de COS
Abstract: The general aim of this study was to determine how the plants influence the aggregate stability, carbohydrate composition and accumulation of soil organic C and microbial C of an Oxisol. In the first part of this study, it was found that summer crop sequences involving corn (Zea mays L.) and the winter crops millet (Pennisetum glaucum (L.) Leeke) and grain sorghum (Sorghum bicolor (L.) Moench) provided the highest mean weight diameter (MWD) of soil aggregate. The crop sequences involving corn in summer also provided the highest soil xylose contents. The lowest proportions of carbohydrates of microbial origin in relation to those of plant origin were found in soil under most frequent cultivation of plant species from monocots. In second part of this study, it was found that soil organic C content with pigeon pea was 20% higher compared to corn and 18% higher compared to sunflower. Likewise, the highest values of C associated to soil particulate organic matter (C-POM) was found with pigeon pea cultivation, which provided 54%, 46% and 48% higher contents than corn, sunflower and oilseed radish, respectively. The variation in C-POM explained the crop effects on soil organic C content. The results of the present study showed a co-accumulation of C-POM and microbial residues in soil. In the third part of this study, it was found that monocots plant materials presented the highest mineralization rates of non-labile pool of C (k), soil pentose content, plant pentose input and soil aggregate MWD. The results of the present study suggest that non-labile C pool, especially related to pentoses, controls the soil aggregation of an Oxisol in long-term. This effect appears to be independent of the variation in soil organic C content
Doutor

Orientador: Ciro Antonio Rosolem
Banca: Maria Helena Moraes
Banca: Juliano Carlos Calonego
Banca: Sandro Roberto Brancalião
Banca: Sônia Carmela Falcci Dechen
Resumo: O manejo inadequado do solo ocasiona a formação de camadas compactadas que prejudicam o desenvolvimento radicular das plantas, diminuindo a disponibilidade de água e nutrientes, enquanto que o acúmulo de carbono pode melhorar a qualidade do solo. Em sistemas com semeadura direta (SSD), com a menor mobilização do solo, pode-se usar, em rotação, plantas com sistema radicular vigoroso, capaz de crescer em condições adversas. Este trabalho teve como objetivo avaliar a ação de espécies de cobertura, gramíneas e uma leguminosa, em rotação com a cultura da soja, nos atributos físicos de um Latossolo, no acúmulo de carbono, nas diferentes frações da matéria orgânica e na produção da soja, em semeadura direta, ao longo de três anos. O experimento foi conduzido em um Latossolo Vermelho distroférrico de textura argilosa, na Fazenda Experimental Lageado, Unesp/Botucatu, nos anos agrícolas de 2006/2007, 2007/2008 e 2008/2009. No outonoinverno foram estabelecidas parcelas com braquiária (Brachiaria ruziziensis), sorgo granífero (Sorghum bicolor) e sorgo consorciado com braquiária. Na primavera, foram cultivados, em subparcelas, milheto (Pennisetum glaucum), cober crop [Sorghum bicolor (L.) Moench x Sorghum sudanense Piper Stapf], crotalária (Crotalaria juncea) ou pousio. A soja foi cultivada como safra de verão. Em março do primeiro ano foram retiradas amostras para caracterização da área experimental. Após o manejo das espécies cultivadas na primavera, no primeiro e terceiro ano, foram retiradas amostras indeformadas nas camadas de 0-5; 7,5-12,5; 15-20; 27,5-32,5 e 47,5-52,5 cm para determinação da densidade do solo, porosidade e curva de retenção de água no solo. Nas mesmas épocas, a estabilidade de agregados foi avaliada em amostras coletadas nas camadas de 0-5 e 5-10 cm. No terceiro ano do experimento, o intervalo hídrico ótimo (IHO) foi determinado... (resumo completo, clicar acesso eletrônico abaixo)
Abstract: Compacted layers resulting from inappropriate soil management may impair root growth, thus decreasing water and nutrient acquisition by crops. Conversely, soil quality is improved with soil carbon accumulation. In areas under no-till, crop rotation with plants with vigorous root systems may alleviate soil compaction, as well as increase soil carbon. In this experiment the effects of cover crops on soil physical properties, carbon accumulation, organic matter quality and soybean production under no-till in a compacted soil were studied for three years. The experiment was conducted on a clayey Rhodic Ferralsol, Lageado Experimental Farm, Unesp/Botucatu, in 2006/2007, 2007/2008 and 2008/2009. Congo grass (Brachiaria ruziziensis), grain sorghum (Sorghum bicolor) and a mix of both were cropped during fall-winter. Then, in the spring, pear millet (Pennisetum glaucum), cober crop [Sorghum bicolor (L.) Moench x Sorghum sudanense Piper Stapf] and indian hemp (Crotalaria juncea) were cropped and a treatment under fallow was set on sub-plots. Soybean was cropped as a summer crop. In March of the first year, samples were taken for characterization of the area. Right after spring crops were chemically desiccated in 2006 and 2008, undisturbed soil samples were taken from the layers 0-5; 7.5-12.5; 15-20; 27.5-32.5 and 47.5-52.5 cm to determine bulk density, porosity and water retention curve. At the same time, samples taken from the depths 0-5 and 5-10 cm were used to determine aggregate stability. In the third year, least limiting water range (LLWR) was evaluated in the 7.5-12.5 and 27.5-32.5 cm soil layers. Organic matter characterization was done in the third year, in the depths of 0-5 and 5-10 cm. Roots of spring crops were sampled in the layers 0-5; 5-10; 10-20; 20-40 and 40- 60 cm, one day before chemical desiccation in all growing seasons. Soybean roots were sampled in the same depths at R2 each... (Complete abstract click electronic access below)
Doutor

Present organic carbon fluxes from an upland peat catchment were quantified through measurement of in-situ direct and indirect greenhouse gas fluxes. To predict future greenhouse gas (GHG) fluxes, peat from eroded (E) and uneroded (U) site of an upland peat catchment was characterized.Composition of peat from E and U sites at the Crowden Great Brook catchment, Peak District Nation Park, UK that was characterized by Pyrolysis-Gas Chromatography-Mass Spectrometry (Py-GC-MS) at 700 oC. Pyrolysis products of the peat were then classified using the Vancampenhout classification into 6 compound classes - viz. aromatic and polyaromatic (Ar), phenols (Ph), lignin compounds (Lg), soil lipids (Lp), polysaccharide compounds (Ps) and N-compounds (N). There was no significant difference in the composition between the eroded and uneroded sites within the study area or between peats from different depths within each site. Nevertheless, there was a significant difference between sites in the proportions of Sphagnum that had contributed to the peat. Pyrolysis products of the peat were also classified into pedogenic (Pd) and aquagenic (Aq) OC – the mean percentage of Pd in both eroded and uneroded peats was 43.93 ± 4.30 % with the balance of the OC classified as Aq.Greenhouse gas (GHG) fluxes were quantified directly by in-situ continuous measurement of GHG was carried out at the E and U sites of the catchment using a GasClam: mean in-situ gas concentrations of CH4 (1.30 ± 0.04 % v/v (E), 0.59 ± 0.05 % v/v (U) and CO2 (8.83 ± 0.22 % v/v (E), 1.77 ± 0.03 % v/v (U)) were observed, with both the CH4 and CO2 concentrations apparently unrelated to atmospheric pressure and temperature changes. Laboratory measurements of ex-situ gas production - for both CH4 and CO2 this was higher for U site soils than for E site soils. At the U site, maximum production rates of both CH4 (46.11±1.47 mMol t-1 day-1) and CO2 (45.56 ± 10.19 mMol t-1 day-1) were observed for 0-50 cm depth in soils. Increased temperature did not affect gas production, whilst increased oxygen increased gas production. The CH4/CO2 ratios observed in-situ are not similar to those observed in the ex-situ laboratory experiments; suggest that some caution is advised in interpreting the latter. However, the maximum OC loss of 2.3 wt. % observed after 20 weeks of ex-situ incubation is nevertheless consistent with the long-term degradation noted by Bellamy et al (1985) from organic-rich UK soils. Indirect greenhouse gas (GHG) fluxes were quantified through the mass flux of suspended organic carbon (SsOC) drained from studied catchments. The SsOC was quantified by interpolating and rating methods. Unfiltered (UF) organic carbon (OC) fluxes in 2010 were calculated to be 8.86 t/km2/yr for the eroded sub-catchment and 6.74 t/km2/yr for the uneroded sub-catchment. All the rating relationships have a large amount of scatter. Both UF OC and <0.2 µm fraction OC are positively correlated with discharge at the eroded site, whilst there is no discernable relationship with discharge at the uneroded site. SsOC is dominated by Pd type OC (95.23 ± 10.20 % from E; 92.84 ± 5.38 % from U) far more so than in sources of the peats, suggesting slower oxidation of Pd (cf. Aq) OC.

Ово истраживање има за циљ да процени резерве органског угљеника у земљишту и представи његову просторну дистрибуцију у земљиштима Републике Србије, као и да утврди зависност садржаја органског угљеника у земљишту од типа земљишта, температуре, падавина, надморске висине, начина коришћења земљишта и морфогенетских карактеристика рељефа. Резерве органског угљеника у земљишту процењене су за слој 0-30 cm и 0-100 cm дубине на основу резултата из базе података уз коришћење педолошке карте и карте коришћења земљишта. За потребе утврђивања зависности садржаја органског угљеника и типа земљишта педолошка карта Србије је прилагођена WRB класификацији и садржи 15.437 полигона. Примењена методологија за процену резерве органског угљеника за дату дубину је базирана на сумирању резерве органског угљеника по слојевима земљишта која се добија на основу запреминске масе, вредности садржаја органског угљеника и дебљине слоја. Прорачун је урађен за сваки профил посебно, затим је урађена калкулација за сваку референтну групу земљишта на основу резултата средњих вредности садржаја органског угљеника до 30 cm и 100 cm дубине за главне референтне групе и њихових површина. На основу површина референтних група земљишта, површине Републике Србије и вредности садржаја за сваку референтну групу, добијене су укупне резерве органског угљеника до 30 cm дубине које износе 0,71 Pg. Резултати анализе резерве органског угљеника до 100 cm дубине показују вредност 1,16 Pg.На основу Corine Land Cover (CLC) базе података за 2006. годину издвојене су површине главних категорија начина коришћења земљишта. На основу резултата средњих вредности садржаја органског угљеника до 30 и 100 cm дубине и површине коју заузима Corine Land Cover категорија начина коришћења земљишта израчуната је укупна вредност резерве органског угљеника за пољопривредна земљишта, шуме и полуприродна подручја и вештачке површине.Резултати показују да су резерве органског угљеника у оквиру категорије пољопривредних површина 303,22 x 1012g (Tg) до 30 cm дубине и 600,25 x 1012g (Tg) до 100 cm дубине. Категорије шуме и полуприродна подручја имају резерве од основних климатских елемената температуре и падавина и надморске висине показује да постоји средње јака до јака статистичка зависност у оквиру испитивања реализованих до 30 и 100 cm дубине.органског угљеника 345,26 x 1012g (Tg) угљеника до 30 cm и 457,55 x 1012g (Tg) до 100 cm дубине. Резултати показују вредности резерве органског угљеника у категорији вештачке површине која углавном обухватају локалитете у оквиру зелених урбаних подручја и рекреационих површина 19,21 x 1012g (Tg) до 30 cm и 41,50 x 1012g (Tg) до 100 cm дубине.Анализа садржаја резерве органског угљеника према начину коришћења земљишта показује да су вредности садржаја органског угљеника веће у шумама и полуприродним подручјима у односу на пољопривредне површине и то за 40,71 % до 30 cm, односно за 11,43 % до 100 cm дубине. Прорачун губитка резерве органског угљеника у земљишту на подручјима где је извршена пренамена пољопривредних површина, шума и полуприродних подручја у урбано земљиште, без категорије зелена урбана подручја, у периоду 1990-2006. године показује укупну вредности од 0,92 Mt С, односно 1,49 Mt С за дубинe до 30 cm, односно до 100 cm.Утврђивање статистичке зависности садржаја органског угљеника у земљиштуод основних климатских елемената температуре и падавина и надморске висине показује да постоји средње јака до јака статистичка зависност у оквиру испитивања реализованих до 30 и 100 cm дубине.Прорачун садржаја резерве органског угљеника у земљишту у зависности од морфометријских карактеристика рељефа показујe да резерва садржаја органског угљеника у земљишту расте са порастом надморске висине. Највеће средње вредности садржаја измерене су на терену који обухвата планине са надморским висинама од 1.000-2.000 m и који обухвата 11,5 % територије Републике Србије
Ovo istraživanje ima za cilj da proceni rezerve organskog ugljenika u zemljištu i predstavi njegovu prostornu distribuciju u zemljištima Republike Srbije, kao i da utvrdi zavisnost sadržaja organskog ugljenika u zemljištu od tipa zemljišta, temperature, padavina, nadmorske visine, načina korišćenja zemljišta i morfogenetskih karakteristika reljefa. Rezerve organskog ugljenika u zemljištu procenjene su za sloj 0-30 cm i 0-100 cm dubine na osnovu rezultata iz baze podataka uz korišćenje pedološke karte i karte korišćenja zemljišta. Za potrebe utvrđivanja zavisnosti sadržaja organskog ugljenika i tipa zemljišta pedološka karta Srbije je prilagođena WRB klasifikaciji i sadrži 15.437 poligona. Primenjena metodologija za procenu rezerve organskog ugljenika za datu dubinu je bazirana na sumiranju rezerve organskog ugljenika po slojevima zemljišta koja se dobija na osnovu zapreminske mase, vrednosti sadržaja organskog ugljenika i debljine sloja. Proračun je urađen za svaki profil posebno, zatim je urađena kalkulacija za svaku referentnu grupu zemljišta na osnovu rezultata srednjih vrednosti sadržaja organskog ugljenika do 30 cm i 100 cm dubine za glavne referentne grupe i njihovih površina. Na osnovu površina referentnih grupa zemljišta, površine Republike Srbije i vrednosti sadržaja za svaku referentnu grupu, dobijene su ukupne rezerve organskog ugljenika do 30 cm dubine koje iznose 0,71 Pg. Rezultati analize rezerve organskog ugljenika do 100 cm dubine pokazuju vrednost 1,16 Pg.Na osnovu Corine Land Cover (CLC) baze podataka za 2006. godinu izdvojene su površine glavnih kategorija načina korišćenja zemljišta. Na osnovu rezultata srednjih vrednosti sadržaja organskog ugljenika do 30 i 100 cm dubine i površine koju zauzima Corine Land Cover kategorija načina korišćenja zemljišta izračunata je ukupna vrednost rezerve organskog ugljenika za poljoprivredna zemljišta, šume i poluprirodna područja i veštačke površine.Rezultati pokazuju da su rezerve organskog ugljenika u okviru kategorije poljoprivrednih površina 303,22 x 1012g (Tg) do 30 cm dubine i 600,25 x 1012g (Tg) do 100 cm dubine. Kategorije šume i poluprirodna područja imaju rezerve od osnovnih klimatskih elemenata temperature i padavina i nadmorske visine pokazuje da postoji srednje jaka do jaka statistička zavisnost u okviru ispitivanja realizovanih do 30 i 100 cm dubine.organskog ugljenika 345,26 x 1012g (Tg) ugljenika do 30 cm i 457,55 x 1012g (Tg) do 100 cm dubine. Rezultati pokazuju vrednosti rezerve organskog ugljenika u kategoriji veštačke površine koja uglavnom obuhvataju lokalitete u okviru zelenih urbanih područja i rekreacionih površina 19,21 x 1012g (Tg) do 30 cm i 41,50 x 1012g (Tg) do 100 cm dubine.Analiza sadržaja rezerve organskog ugljenika prema načinu korišćenja zemljišta pokazuje da su vrednosti sadržaja organskog ugljenika veće u šumama i poluprirodnim područjima u odnosu na poljoprivredne površine i to za 40,71 % do 30 cm, odnosno za 11,43 % do 100 cm dubine. Proračun gubitka rezerve organskog ugljenika u zemljištu na područjima gde je izvršena prenamena poljoprivrednih površina, šuma i poluprirodnih područja u urbano zemljište, bez kategorije zelena urbana područja, u periodu 1990-2006. godine pokazuje ukupnu vrednosti od 0,92 Mt S, odnosno 1,49 Mt S za dubine do 30 cm, odnosno do 100 cm.Utvrđivanje statističke zavisnosti sadržaja organskog ugljenika u zemljištuod osnovnih klimatskih elemenata temperature i padavina i nadmorske visine pokazuje da postoji srednje jaka do jaka statistička zavisnost u okviru ispitivanja realizovanih do 30 i 100 cm dubine.Proračun sadržaja rezerve organskog ugljenika u zemljištu u zavisnosti od morfometrijskih karakteristika reljefa pokazuje da rezerva sadržaja organskog ugljenika u zemljištu raste sa porastom nadmorske visine. Najveće srednje vrednosti sadržaja izmerene su na terenu koji obuhvata planine sa nadmorskim visinama od 1.000-2.000 m i koji obuhvata 11,5 % teritorije Republike Srbije
The aim of this study was to quantify current SOC stocks and present the spatial distribution of organic carbon (SOC) in the soils of Republic of Serbia. The relation of SOC content to soil type, temperature, precipitation, altitude, land use and topography was investigated. Organic carbon stocks were estimated for soil layers 0-30 cm and 0-100 cm based on the results from a database and using soil and land use maps.To establish the relationship between organic carbon content and soil type, a soil map of Serbia was adapted to the WRB classification and divided into 15,437 polygons (map units). The methodology for SOC stocks estimation was based on bulk density, organic carbon content and thickness of the analyzed soil layers. We calculated the values for each reference soil group based on mean values of SOC at 0-30 and 0-100 cm in the main reference groups and their areas. Based on the size of the reference groups, total area of Republic of Serbia, and the SOC values for each reference group, we calculated the total SOC stocks. The obtained values for the soil layers 0-30 cm and 0-100 cm amounted to 0,71 Pg and 1,16 Pg respectively.Using Corine Land Cover (CLC) database for 2006, we defined areas of the major categories of land use. Based on the obtained mean values of organic carbon content at 0-30 and 0-100 cm and the areas indicated by Corine Land Cover categories of land use, we calculated the organic carbon stocks in agricultural land, forest land, semi-natural areas, and artificial areas. The results showed that the organic carbon stocks in the category of agricultural land were 303.22 x 1012 g (Tg) and 600.25 x 1012 g (Tg) at 0-30 cm and 0-100 cm, respectively. In the category of forests and semi-natural areas, the organic carbon stocks were 345.26 x 1012 g (Tg) and 457.55 x 1012 g (Tg) at 0-30 cm and 0-100 cm, respectively. In the category of artificial areas, which mainly included sites within urban green areas and recreational areas, the organic carbon stocks were 19.21 x 1012 g (Tg) and 41.50 x 1012 g (Tg) at 0-30 cm and 0-100 cm, respectively. The map of organic carbon distribution depending on land use method indicated that organic carbon stocks were higher in forests and semi-natural areas than in agricultural land, up to 40.71% and 11.43% at 0-30 cm and 0-100 cm, respectively.SOC loss amount to 0,92 Mt С at 0-30 cm layer and 1,49 Mt С at 0-100 cm layer in the period 1990-2006 as a results of conversion from agricultural land, forestland and semi-natural areas to artificial areas.For soil layers 0-30 and 0-100 cm, a medium to strong statistical relationship between temperature, precipitation and altitude and amount of organic carbon in soil is indicated. The soil organic carbon density was significantly affected by altitude. SOC content increased with increasing altitude.The highest mean values of organic carbon content were found in the mountainous areas within the elevation of 1000-2000 m, which covers 11,5 % of the territory of the Republic of Serbia.

The European renewable energy directive 2009/28/EC (E.C. 2009) provides a legislative framework for reducing GHG emissions by 20%, while achieving a 20% share of energy from renewable sources by 2020. Perennial energy crops could significantly contribute to limit GHG emissions through replacing equivalent fossil fuels and by sequestering a considerable amount of carbon into the soil through the large amounts of belowground biomass produced. The objective of this study is to evaluate the effects of land use change that perennial energy crops have on croplands (switchgrass) and marginal grasslands (miscanthus). For that purpose above and belowground biomass, SOC variation and Net Ecosystem Exchange were evaluated after five years of growth. At aboveground level both crops produced high biomass under cropland conditions as well as under marginal soils. At belowground level they also produced large amounts of biomass, but no significant influences on SOC in the upper layer (0-30 cm) were found. This is probably because of the "priming effect" that caused fast carbon substitution. In switchgrass only it was found a significant SOC increase in deeper layers (30-60 cm), while in the whole soil profile (0-60 cm) SOC increased from 42 to 51 ha-1. However, the short experimental periods (for both switchgrass and miscanthus), in which land use change was evaluated, do not permit to determine the real capacity of perennial energy crops to accumulate SOC. In conclusion the large amounts of belowground biomass enhanced the SOC dynamic through the priming effect resulting in increased SOC in cropland but not in marginal grassland.

Soils are the largest pool of carbon (C) in terrestrial ecosystems and store 1500 Gt of C in their soil organic matter (SOM). SOM is a dynamic, complex and heterogeneous mixture, which influences soil quality through a wide range of soil properties. Labile SOM comprises a small fraction of total SOM (approximately 5%), but due to its rapid turnover has been suggested to be most vulnerable to loss following soil disturbance. This research was undertaken to examine the consequences of soil disturbance on labile SOM, its availability and protection in soils using the isotopic analysis of soil-respired CO₂ (δ¹³CO₂). A range of soils were incubated in both the short- (minutes) and long-term (months) to assess changes in labile SOM. Shifts in soil-respired δ¹³CO₂ over the course of soil incubations were found to reflect changes in labile substrate utilisation. There was a rapid depletion of δ¹³CO₂ (from a starting range between -22.5 and -23.9‰, to between -25.8 and -27.5‰) immediately after soil sampling. These initial changes in δ¹³CO₂ indicated an increased availability of labile SOM following the disturbance of coring the soil and starting the incubations. Subsequently δ¹³CO₂ reverted back to the initial, relatively enriched starting values, but this took several months and was due to labile SOM pools becoming exhausted. A subsequent study was undertaken to test if soil-respired δ¹³CO₂ values are a direct function of the amount of labile SOM and soil physical conditions. A range of pasture soils were incubated in the short-term (300 minutes), and changes in soil-respired δ¹³CO₂ were measured along with physical and chemical soil properties. Equilibrium soil-respired δ¹³CO₂, observed after the initial rapid depletion and stabilisation, was a function of the amount of labile SOM (measured as hot water extractable C, HWEC), total soil C and soil protection capacity (measured as specific soil surface area, SSA). An independent experimental approach to assess the effect of SSA, where labile SOM was immobilised onto allophane – a clay mineral with large, active surface area – indicated limited availability of labile SOM through more enriched δ¹³CO₂ (in a range between -20.5 and -20.6 ‰) and a significant (up to three times) reduction in HWEC. In the third study, isotopic measurements were coupled with CO₂ evolution rates to directly test whether equilibrium soil-respired δ¹³CO₂ can reflect labile SOM vulnerability to loss. Soils were sampled from an experimental tillage trial with different management treatments (chemical fallow, arable cropping and permanent pasture) with a range of C inputs and soil disturbance regimes. Soils were incubated in the short- (300 minutes) and long-term (600 days) and changes in δ¹³CO₂ and respiration rates measured. Physical and chemical fractionation methods were used to quantify the amount of labile SOM. Pasture soils were characterised by higher labile SOM estimates (HWEC; sand-sized C; labile C respired during long-term incubations) than the other soils. Long-term absence of plant inputs in fallow soils resulted in a significant depletion of labile SOM (close to 50% based on sand-sized C and HWEC estimates) compared with pasture soils. The values of δ¹³CO₂ became more depleted in 13C from fallow to pasture soils (from -26.3 ‰ to -28.1 ‰) and, when standardised (against the isotopic composition of the solid soil material), Δ¹³CO₂ values also showed a decrease from fallow to pasture soils (from -0.3 ‰ to -1.1 ‰). Moreover, these patterns in isotopic measures were in strong agreement with the amount of labile SOM and its availability across the soils, and were best explained by the isotopic values of the labile HWEC fraction. Collectively, these results confirm that labile SOM availability and utilisation change immediately after soil disturbance. Moreover, isotopic analysis of soil-respired CO₂ is a powerful technique, which enables us to probe mechanisms and examine the consequences of soil disturbance on labile SOM by reflecting its availability and the degree of SOM protection.

The Podzols of the world are divided into intra-zonal and zonal according to then location. Zonal Podzols are typical for boreal and taiga zone associated to climate conditions. Intra-zonal podzols are not necessarily limited by climate and are typical for mineral poor substrates. The Intra-zonal Podzols of the Brazilian Amazon cover important surfaces of the upper Amazon basin. Their formation is attributed to perched groundwater associated to organic matter and metals accumulations in reducing/acidic environments. Podzols have a great capacity of storing important amounts of soil organic carbon in deep thick spodic horizons (Bh), in soil depths ranging from 1.5 to 5m. Previous research concerning the soil carbon stock in Amazon soils have not taken into account the deep carbon stock (below 1 m soil depth) of Podzols. Given this, the main goal of this research was to quantify and to map the soil organic carbon stock in the region of Rio Negro basin, considering the carbon stored in the first soil meter as well as the carbon stored in deep soil horizons up to 3m. The amount of soil organic carbon stored in soils of Rio Negro basin was evaluated in different map scales, from local surveys, to the scale of the basin. High spatial and spectral resolution remote sensing images were necessary in order to map the soil types of the studied areas and to estimate the soil carbon stock in local and regional scale. Therefore, a multi-sensor analysis was applied with the aim of generating a series of biophysical attributes that can be indirectly related to lateral variation of soil types. The soil organic carbon stock was also estimated for the area of the Brazilian portion of the Rio Negro basin, based on geostatistical analysis (multiple regression kriging), remote sensing images and legacy data. We observed that Podzols store an average carbon stock of 18 kg C m-2 on the first soil meter. Similar amount was observed in adjacent soils (mainly Ferralsols and Acrisols) with an average carbon stock of 15 kg C m-2. However if we take into account a 3 m soil depth, the amount of carbon stored in Podzols is significantly higher with values ranging from 55 kg C m-2 to 82 kg C m-2, which is higher than the one stored in adjacent soils (18 kg C m-2 to 25 kg C m-2). Given this, the amount of carbon stored in deep soil horizons of Podzols should be considered as an important carbon reservoir, face a scenario of global climate change
Os Espodossolos podem ser divididos em zonais e intrazonais de acordo com área onde ocorrem. Os Espodossolos zonais são típicos de áreas boreais e taiga, delimitados por condições climáticas. Já os intrazonais não são condicionados pelo clima. Os Espodossolo intrazonais brasileiros ocupam uma grande extensão da alta bacia amazônica, tendo sua formação atribuída à ocorrência de lençóis freáticos suspensos associados à acumulação de complexos organometálicos em ambientes ácidos redutores. Esses solos tem a capacidade de estocar grandes quantidades de carbono orgânico em horizontes espódicos profundos (Bh), em profundidades que podem variar de 1,5m a 5m. Pesquisas atuais relacionadas ao estoque de carbono em solos amazônicos, não levam em consideração os estoques encontrados no horizonte Bh (abaixo de 1m de profundidade). Sendo assim, o principal objetivo da presente pesquisa foi quantificar e mapear o estoque de carbono nos solos da bacia do Rio Negro, tendo-se em vista aquele estocado no primeiro metro de solo, bem como o carbono armazenado em até 3m de profundidade. A quantidade de carbono orgânico estocado nos solos da bacia do Rio Negro foi estimada em diferentes escalas de mapeamento, desde mapas locais até a escala da bacia do Rio Negro. Imagens de sensoriamento remoto de alta resolução espacial e espectral foram essenciais para viabilizar o mapeamento dos solos nas áreas estudadas e permitir a estimativa do estoque de carbono. Uma análise multisensor foi adotada buscando-se gerar informações biofísicas indiretamente associadas à variação lateral dos tipos de solo. Após o mapeamento do estoque de carbono em escala regional, partiu-se para a estimativa na escala da bacia do Rio Negro, com base em análise geoestatística (krigagem por regressão linear), imagens de sensoriamento remoto e base de dados de domínio público. Após o mapeamento do estoque de carbono na escala da bacia, constatou-se que os Espodossolos têm um estoque médio de 18 kg C m-2, para 1m de profundidade, valor similar ao observado em solos adjacentes (Latossolos e Argissolos) os quais tem um estoque de 15 kg C m-2. Quando são considerados os estoques profundos, até 3m, a quantidade de carbono dos Espodossolos é superior com valores variando de 55 kg C m-2 a 82 kg C m-2. Estoque relativamente maior que aquele observado em solos adjacentes para esta profundidade (18 kg C m-2 a 25 kg C m-2). Portanto, o estoque de carbono profundo dos Espodossolos, não deve ser negligenciado levando-se em conta cenários futuros de mudanças climáticas

Under the Kyoto Protocol, participating nations are required to reduce National CO₂emissions according to their 'reduction commitment' or 'quantified emissions limitation', over the first commitment period, 2008-2012. One way in which nations could achieve this would be by increasing soil carbon storage through different management practices. Most former estimates of regional scale C sequestration potential have made use of either linear regressions based on long-term experimental data, whilst some have used dynamic soil organic matter (SOM) models linked to spatial databases. Few studies have compared these two methods, and none have compared regressions with two different SOM models. This thesis presents a case study investigation of the potential of different land management practices to sequester carbon in soil in arable land, and preliminary estimates of other potential C savings. Two dynamic SOM models were chosen for this study, RothC (a soil process model) and CENTURY (a general ecosystem model). RothC and CENTURY are the two most widely used and validated SOM models world-wide. Methods were developed to enhance use and comparability of the models in a predictive mode. These methods included a) estimation of the IOM pool for RothC, b) estimation of C inputs to soil, c) investigation of pool size distributions in CENTURY, and d) creation of a program to allow use of C inputs derived from CENTURY with the RothC model. This thesis has also investigated the importance of errors in C inputs to soil for predictive SOM modelling, and performed sensitivity analyses to investigate how errors in setting the size refractory SOM pools might affect predictions of SOC. RothC and CENTURY were compared at the site scale using datasets from seven European long-term experiments, in order to a) verify their ability to predict SOC changes under changes in land use and management relevant to studies of C sequestration potential, b) evaluate model performance under European climatic conditions, and c) compare the performance of the two models. Finally, a Geographic Information System (GIS) containing soil, land use and climate layers, was assembled for a case study region in Central Hungary. GIS interfaces were developed for the RothC and CENTURY models, thus linking them to spatial datasets at the regional level. This allowed a comparison of estimates of the C sequestration potential of different land management practices obtained using the two models and using regression-based estimates. Although estimates obtained by the different approaches were of the same order of magnitude, differences were observed. Encouragingly, some of the land management scenarios studied here showed sufficient C mitigation potential to meet Hungarian CO₂reduction commitments.

Soil organic matter (SOM) models simplify the complex turnover dynamics of organic matter in soils. Stabilization mechanisms are currently thought to play a dominant role in SOM turnover but they are not explicitly accounted for in most SOM models. One study addresses the implementation of an approach to account for the stabilization mechanism of physical protection in the SOC model RothC using 13C abundance measurements in conjunction with soil size fractionation data. SOM models are increasingly used to support policy decisions on carbon (C) mitigation and credibility of model predictions move into the focus of research. A site scale, Monte Carlo based model uncertainty analysis of a SOM model was carried out. One of the major results was that uncertainty and factor importance depend on the combination of external drivers. A different approach was used with the SOM ECOSSE model to estimate uncertainties in soil organic carbon (SOC) stock changes of mineral and organic soils in Scotland. The average statistical model error from site scale evaluation was transferred to regional scale uncertainty to give an indication of the uncertainty in national scale predictions. National scale simulations were carried out subsequently to quantify SOC stock changes differentiating between organic and mineral soils and land use change types. Organic soils turned out to be most vulnerable to SOC losses in the last decades. The final study of this thesis emplyed the RothC model to simulate possible futures of global SOC stock changes under land use change and ten different climate scenarios. Land use change turned out to be of minor importance. The regionally balance between soil C inputs and decomposition leads to a diverse map of regional C gains and losses with different degrees of certainty.

Of the organic matter in soils typically < 1% by weight is dissolved in the soil solution (dissolved organic matter; DOM). DOM is a continuum of molecules of various sizes and chemical structures which has largely been operationally defined as the fraction of total organic carbon in an aqueous solution that passes through a 0.45 µm filter. Although only representing a relatively small proportion, it represents the most mobile part of soil organic carbon and is probably enriched with highly labile compounds. DOM acts as a source of nutrients for both soil and aquatic micro-organisms, influences the fate and transport of organic and inorganic contaminants, presents a potential water treatment problem and may indicate the mobilisation rate of key terrestrial carbon stores. The objective of this research was to ascertain some of the biologically relevant characteristics of soil DOM and specifically to determine: (1) the influence of method and time of extraction of DOM from the soil on its biochemical composition and concentration; (2) the dynamics of DOM biodegradation; and, (3) the effects of repeated applications of trace amounts of DOM on the rate of soil carbon mineralization. To examine the influence of method and time of extraction on the composition and concentration of DOM, soil solution was collected from a raised peat bog in Central Scotland using water extraction, field suction lysimetry, and centrifugation techniques on a bimonthly basis over the period of a year (Aug 2003 – Jun 2004). Samples were analysed for dissolved organic carbon (DOC), dissolved organic nitrogen (DON), protein, carbohydrate and amino acid content. For all of the sampled months except June the biochemical composition of DOC varied with extraction method, suggesting the biological, chemical and/or physical influences on DOC production and loss are different within the differently sized soil pores. Water-extractable DOC generally contained the greatest proportion of carbohydrate, protein and/or amino acid of the three extraction methods. Time of extraction had a significant effect on the composition of water- and suction-extracted DOC: the total % carbohydrate + protein + amino acid C was significantly higher in Oct than Dec, Feb and Jun for water-extracted DOC and significantly greater in Dec than Aug, Apr and Jun for suction-extracted DOC. There was no significant change in the total % carbohydrate + protein + amino acid C of centrifuge-extracted DOC during the sampled year. Time of extraction also had a significant effect on the % protein + amino acid N in water- and centrifuge-extracted DON: Oct levels were significantly higher than Feb for water-extracted DON and significantly higher in Aug and Apr for centrifuge-extracted DON. Concentrations of total DOC and total DON were also found to be dependent on time of extraction. DOC concentrations showed a similar pattern of variation over the year for all methods of extraction, with concentrations relatively constant for most of the year, rising in April to reach a peak in Jun. DON concentrations in water- and centrifuge-extracted DON peaked later, in Aug. There were no significant seasonal changes in the concentration of suction-extracted DON. A lack of correlation between DOC and DON concentrations suggested that DOC and DON production and/or loss are under different controls. Laboratory-based incubation experiments were carried out to examine the dynamics of DOC biodegradation. Over a 70 day incubation period at 20oC, the DOM from two types of peat (raised and blanket) and four samples of a mineral soil (calcaric gleysol), each previously exposed to a different management strategy, were found to be comprised of a rapidly degradable pools (half-life: 3 – 8 days) and a more stable pool (half-life: 0.4 to 6 years). For all soil types/treatments, excepting raised peat, the total net loss of DOC from the culture medium was greater than could be accounted for by the process of mineralization alone. A comparison between net loss of DOC and loss of DOC to CO2 and microbial biomass determined by direct microscopy suggested that at least some of the differences between DOC mineralised and net DOC loss were due to microbial assimilation and release. Changes in the microbial biomass during the decomposition process showed proliferation followed by decline over 15 days. The protein and carbohydrate fractions showed a complex pattern of both degradation and production throughout the incubation. The effects of repeated applications of trace amounts of litter-derived DOC on the rate of carbon mineralization over a 35 day period were investigated in a laboratory based incubation experiment. The addition of trace amounts of litter-derived DOC every 7 and 10.5 days appeared to ‘trigger’ microbial activity causing an increase in CO2 mineralisation such that extra C mineralised exceeded DOC additions by more than 2 fold. Acceleration in the rate of extra C mineralised 7 days after the second addition suggested that either the microbial production of enzymes responsible for biodegradation and/or an increase in microbial biomass, are only initiated once a critical concentration of a specific substrate or substrates has been achieved. The addition of ‘DOC + nutrients’ every 3.5 days had no effect on the total rate of mineralization. To date DOC has tended to be operationally defined according to its chemical and physical properties. An understanding of the composition, production and loss of DOC from a biological perspective is essential if we are to be able to predict the effects of environmental change on the rate of mineralization of soil organic matter. This research has shown that the pools of DOC extracted, using three different methods commonly used in current research, are biochemically distinct and respond differently to the seasons. This suggests some degree of compartmentalisation of biological processes within the soil matrix. The observed similarities between the characteristics of the decomposition dynamics of both peatland and agricultural DOC suggests that either there is little difference in substrate quality between the two systems or that the microbial community have adapted in each case to maximise their utilisation of the available substrate. The dependency of the concentration and biochemical composition of DOC on the seasons requires further work to ascertain which biotic and/or abiotic factors are exerting control. Published research has focussed on factors such as temperature, wet/dry cycles, and freeze/thawing. The effect of the frequency of doses of trace amounts of DOC on increasing the rate of soil organic C mineralization, evident from this research, suggests that the interval between periods of rainfall may be relevant. It also emphasises how it can be useful to use knowledge of a biological process as the starting point in determining which factors may be exerting control on DOC production and loss.

This study was designed to evaluate the status, distribution, spatial variability, controlling factors, storage, and change in the levels of soil organic carbon (SOC) in two major alluviums of Bangladesh. The two alluviums the Brahmaputra and the Ganges were selected because they occupy a large area of Bangladesh with a wide diversity of agro-ecosystems. SOC levels were studied across the four sub-sites in the aforementioned alluviums at 0-30 cm depths to evaluate their spatial and temporal variability. The sub-sites, Delduar and Melandah, are in the Brahmaputra alluvium. The other two sub-sites, Mirpur and Fultala, are in the Ganges alluvium. Additionally, SOC and total nitrogen (TN) distribution were studied across eight soil profiles (0-120 cm depths) under the two alluviums. The results revealed that the SOC contents were very low in all the sites. The classical statistics showed that the variability of the SOC was moderate across the four sub-sites. The SOC distribution was positively skewed across all the sub-sites except Fultala. A semivariogram model showed there was generally a weak spatial correlation (R2 < 0.5) of SOC in the study sites. A relatively large sampling grid (1600m) and intensive soil management were perhaps responsible for the observed weak spatial dependency. SOC variability is lower across the highland (HL) and medium highland (MHL) sites than the medium lowland (MLL) and lowland (LL) sites. Changes in land use and land cover were also more intensive in the HL and MHL sites than the MLL and LL sites. The reason for low SOC in the HL and MHL sites may be due to their lower inundation level, e.g., land levels in relation to flooding depths, together with greater intensity of use. Temporal variability of SOC datasets revealed that SOC has declined across all the sites during the last 20-25 years due to the intensive land use with little or no crop residue inputs. It is plausible that SOC has declined to an equilibrium level, and further decline may not occur unless land use intensity changes further. The findings show that SOC is positively related to the TN and clay contents in the soils. This is not surprising as SOC is a major pool of TN, and soil clay fraction is known to protect SOC degradation. SOC and TN storage is higher in the surface soil horizon (0-20 cm) than the sub surface soils. Topsoil horizon is tilled and receives greater crop residue inputs which are subsequently mineralized resulting in higher accumulation of SOC and TN. It appears that inundation land types and land management practices may be the major driving factors of SOC storage and distribution across the study sites.

Orientador : Dr. Anibal de Moraes, Dr Jeferson Dieckow e Dr. Alan J. Franzluebbers
Tese (doutorado) - Universidade Federal do Paraná, Setor de Ciências Agrárias, Programa de Pós-Graduação em Agronomia. Defesa: Curitiba, 24/10/2016
Inclui referências: f. 47-50;72-77;97-101
Área de concentração: Produção vegetal
Resumo: A disponibilidade de solos e seus recursos está reduzindo com a evolução da humanidade e os impactos negativos, decorrentes do mau uso dos solos, estão afetando o desenvolvimento sustentável da agropecuária mundial. Portanto, se faz necessário o desenvolvimento de alternativas que permitam um uso mais sustentável dos solos, para atender as demandas no setor de produção agropecuária do século 21. O objetivo geral desta tese foi estudar solos de sistemas de produção agropecuária que buscam a intensificação de uso sustentável, ou de ecossistemas naturais, como uma etapa para melhor entender dinâmicas complexas de nutrientes. Foram estudados a composição de fósforo (P) no solo em sistemas integrados de produção agropecuária (SIPA) no subtrópico brasileiro, bem como em ecossistemas naturais em escala global e por fim, a dinâmica do carbono (C) orgânico em um sistema agroflorestal localizado na Carolina do Norte, Estados Unidos da América. O primeiro objetivo específico foi determinar a composição de P no solo de agroecossitemas com baixa e alta complexidade trófica. Especificamente, objetivou-se qualificar e quantificar os componentes orgânicos e inorgânicos de P usando extratos de NaOH-EDTA e espectroscopia de ressonância magnética nuclear, para posteriormente caracterizar a ciclagem de P em resposta ao aumento da complexidade trófica com SIPA no subtrópico brasileiro. A presença do pastejo resultou em maior concentração de ortofosfato total e biodisponível (i.e., Mehlich-I) e também diminuiu a concentração de P orgânico, incluindo os inositol fosfatos. O pastejo aumentou a biodisponibilidade de P e reduziu a concentração de P orgânico recalcitrante (i.e., inositol fosfatos), portanto, concluiu-se que a integração entre lavoura e pecuária pode ser uma alternativa sustentável para aumentar o uso do P nos sistemas de produção no subtrópico brasileiro. O segundo objetivo específico foi analisar com meta-regressão (meta-análise), a dinâmica do P em diferentes texturas de solo e de clima em escala global, relacionando os grupos funcionais de P com o pH, concentração de C, relação CN e relação CP do solo em ecossistemas naturais. A composição de P orgânico teve uma resposta complexa à estas características do solo. A relação de monoesteres para o P orgânico aumentou com o aumento do pH, e diminuiu com o decréscimo da concentração de C, relação CN e relação CP, sem haver resposta particular para os locais e textura do solo. Em contraste, a relação de diesteres para o P orgânico bem como a relação diesteres para monoesteres teve o comportamento inverso, diminuindo com o aumento do pH, e aumentando com o aumento da concentração de C, relação carbono-nitrogênio (CN) e relação carbono-fósforo (CP). Portanto, concluiu-se que o pH, a concentração de C e as relações CN e CP são importantes fatores na determinação das proporções dos grupos funcionais de P orgânico do solo. O terceiro objetivo específico foi determinar a distribuição espacial de atributos do solo (textura e frações de C orgânico do solo) usando a combinação de espectroscopia de reflectância no infravermelho proximal (NIRS) e geoestatística, em um experimento de sistema agroflorestal localizado na Carolina do Norte, Estados Unidos da América. O NIRS foi uma ferramenta útil para predizer a textura do solo e as frações de C do solo. Na fase de calibração e validação do NIRS, o modelo de máquina de vetores de suporte teve uma performance melhor do que o modelo de mínimos quadrados parciais na predição das características do solo. A geoestatística aumentou os erros em relação àquales obtidos somente com o NIRS. Entretanto, a geoestatística possibilitou realizar a exploração das características espaciais da textura do solo e frações de C. A combinação do NIRS com a geoestatística pode ser utilizada para avaliação de atributos do solo deste sistema agroflorestal e de outros sistemas de produção, permitindo assim aumentar a sustentabilidade dos agroecossistemas através do manejo com agricultura de precisão. Palavras chave: integração lavoura-pecuária, plantio direto, ciclagem de nutrientes.
Abstract: Soil resources are narrowing as human evolution occurs and the negative feedbacks resulting from soil misuse are affecting agriculture's sustainable development worldwide. Therefore, alternatives that allow a more sustainable use of soils are necessary, to fill demands of the 21-century agriculture. The general objective of this thesis was to evaluate soils of agricultural systems that pursue sustainable intensification and natural ecosystems as a step to understand complex nutrient dynamics, which knowledge might help to adapt management by agriculture. It was studied the soil phosphorus compounds on integrated crop-livestock systems in Subtropical Brazil and on natural ecosystems across the world and soil organic carbon (C) dynamics in an agroforestry system on a Coastal Plain in United States of America. The first specific objective was to determine soil P composition from agro-ecosystems with low and high trophic complexity. Specifically, we wanted to qualify and quantify soil organic and inorganic P fractions using NaOH-EDTA extraction and nuclear magnetic resonance spectroscopy, and characterize P cycling in response to increasing complexity with integrated crop-livestock systems in subtropical Brazil. Our results were that in these agro-ecosystems, grazing compared with nograzing had greater soil P content as total and bioavailable (i.e., Mehlich-I) orthophosphate and lower soil organic P and fewer monoesters, including inositol phosphates. Grazing increased P bioavailability and reduced recalcitrant organic P (i.e., inositol phosphates) concentration in soil; therefore, we conclude that integrating crop and livestock systems can be a sustainable alternative to improve P use in farming systems of subtropical Brazil. The second specific objective was to analyze through meta-regression, soil organic phosphorus dynamics among different soil textures and locates at global scale, relating its organic functional groups with soil pH, C concentration, carbon-to-nitrogen (CN) ratio and carbon-to-phosphorus (CP) ratio on natural ecosystems. We found that soil organic P composition had a complex response to those soil characteristics. Monoesters-to-organic P ratio increased as pH increased, and decreased as C concentration, CN ratio and CP ratio increased, with no particular response among locates and soil textures. In contrast, diesters-to-organic P ratio as well as diesters-to-monoesters ratio had the opposite behavior, decreasing its concentrations as pH increased, and increasing as soil C concentration, CN ratio and CP ratio increased. Therefore we concluded that soil pH, C concentration, CN ratio and CP ratio are important factors in determining proportions of soil organic P functional groups. The third specific objective was to determine the spatial distribution soil properties (soil texture and organic C fractions) using a combination of near infrared spectroscopy and geostatistics, in an emerging agroforestry system experiment on a Coastal Plain site in North Carolina. Nearinfrared spectroscopy was a useful tool to predict soil texture and soil organic carbon (SOC) fractions. Using chemometrics to calibrate NIRS, a support vector machine model performed better than a partial least squares model to predict soil texture (sand and clay) and SOC fractions (total, particulate, and mineralizable C determined as the flush of CO2-C following rewetting of dried soil). Geostatistics increased errors of soil properties compared to those obtained solely by NIRS prediction. Nonetheless, geostatistics was useful to explore spatial patterns of soil texture and SOC fractions. Combining NIRS and geostatistics can be promoted for soil evaluation of this agroforestry system and in other landscapes to increase sustainability of agroecosystems through field-specific precision management. Key words: mixed crop-livestock, no-tillage, nutrient cycling.

Agricultural productivity, ecosystem health, and wetland restoration rely on soil organic carbon (SOC) as vital for microbial activity and plant health. This study assessed: (1) accuracy of topographic-based non-linear models for predicting SOC; and (2) the effect of analytic strategies and soil condition on performance of spectral-based models for predicting SOC. SOC data came from 28 agriculturally converted Delmarva Bays sampled down to 1 meter. R2 was used as an indicator of model performance. For topographic-based modeling, correlation coefficients and condition indices reduced 50 terrain-related values to three datasets of 16, 11, and 7 variables. Five types of non-linear models were examined: Generalized Linear Mondel (GLM) ridge, GLM LASSO, Generalized Additive Model (GAM) non-penalized, GAM cubic splice, and partial least-squares regression. Carbon stocks varied widely, 50 to 219 Mg/ha, with the average around 93 Mg/ha. Topography shared a weak relationship to SOC with most attributes showing a correlation coefficient less than 0.3. GLM ridge and both GAMs achieved moderate accuracy at least once, usually using the 16 or 11 variable datasets. GAMs consistently performed the best. Prior to carbon analysis, hyperspectral signatures were recorded for the topmost soil horizons under different conditions: moist unground, dry unground, and dry ground. Twenty-four math treatment and smoothing technique combinations were run on each hyperspectral dataset. R2 varied greatly within datasets depending on analytic strategy, but all datasets returned an R2 greater than 0.9 at least twice. Moist unground soil models outperformed the others when comparing the best models among datasets.
Master of Science

Soil is the world’s largest terrestrial carbon (C) sink, and is estimated to contain approximately 1600 Pg of carbon to a depth of one metre. The distribution of soil organic C (SOC) largely follows gradients similar to biomass accumulation, increasing with increasing precipitation and decreasing temperature. As a result, SOC levels are a function of inputs, dominated by plant litter contributions and rhizodeposition, and losses such as leaching, erosion and heterotrophic respiration. Therefore, changes in biomass inputs, or organic matter accumulation, will most likely also alter these levels in soils. Although the soil microbial biomass (SMB) only comprises 1-5% of soil organic matter (SOM), it is critical in organic matter decomposition and can provide an early indicator of SOM dynamics as a whole due to its faster turnover time, and hence, can be used to determine soil C dynamics under changing environmental conditions.¶ Approximately 932 million ha of land worldwide are degraded due to salinity and sodicity, usually coinciding with land available for agriculture, with salinity affecting 23% of arable land while saline-sodic soils affect a further 10%. Soils affected by salinity, that is, those soils high in soluble salts, are characterised by rising watertables and waterlogging of lower-lying areas in the landscape. Sodic soils are high in exchangeable sodium, and slake and disperse upon wetting to form massive hardsetting structures. Upon drying, sodic soils suffer from poor soil-water relations largely related to decreased permeability, low infiltration capacity and the formation of surface crusts. In these degraded areas, SOC levels are likely to be affected by declining vegetation health and hence, decreasing biomass inputs and concomitant lower levels of organic matter accumulation. Moreover, potential SOC losses can also be affected from dispersed aggregates due to sodicity and solubilisation of SOM due to salinity. However, few studies are available that unambiguously demonstrate the effect of increasing salinity and sodicity on C dynamics. This thesis describes a range of laboratory and field investigations on the effects of salinity and sodicity on SOC dynamics.¶ In this research, the effects of a range of salinity and sodicity levels on C dynamics were determined by subjecting a vegetated soil from Bevendale, New South Wales (NSW) to one of six treatments. A low, mid or high salinity solution (EC 0.5, 10 or 30 dS/m) combined with a low or high sodicity solution (SAR 1 or 30) in a factorial design was leached through a non-degraded soil in a controlled environment. Soil respiration and the SMB were measured over a 12-week experimental period. The greatest increases in SMB occurred in treatments of high-salinity high-sodicity, and high-salinity low-sodicity. This was attributed to solubilisation of SOM which provided additional substrate for decomposition for the microbial population. Thus, as salinity and sodicity increase in the field, soil C is likely to be rapidly lost as a result of increased mineralisation.¶ Gypsum is the most commonly-used ameliorant in the rehabilitation of sodic and saline-sodic soils affected by adverse soil environmental conditions. When soils were sampled from two sodic profiles in salt-scalded areas at Bevendale and Young, SMB levels and soil respiration rates measured in the laboratory were found to be low in the sodic soil compared to normal non-degraded soils. When the sodic soils were treated with gypsum, there was no change in the SMB and respiration rates. The low levels of SMB and respiration rates were due to low SOC levels as a result of little or no C input into the soils of these highly degraded landscapes, as the high salinity and high sodicity levels have resulted in vegetation death. However, following the addition of organic material to the scalded soils, in the form of coarsely-ground kangaroo grass, SMB levels and respiration rates increased to levels greater than those found in the non-degraded soil. The addition of gypsum (with organic material) gave no additional increases in the SMB.¶ The level of SOC stocks in salt-scalded, vegetated and revegetated profiles was also determined, so that the amount of SOC lost due to salinisation and sodication, and the increase in SOC following revegetation relative to the amount of SOC in a vegetated profile could be ascertained. Results showed up to three times less SOC in salt-scalded profiles compared to vegetated profiles under native pasture, while revegetation of formerly scalded areas with introduced pasture displayed SOC levels comparable to those under native pasture to a depth of 30 cm. However, SOC stocks can be underestimated in saline and sodic landscapes by setting the lower boundary at 30 cm due to the presence of waterlogging, which commonly occurs at a depth greater than 30 cm in saline and sodic landscapes as a result of the presence of high or perched watertables. These results indicate that successful revegetation of scalded areas has the potential to accumulate SOC stocks similar to those found prior to degradation.¶ The experimental results from this project indicate that in salt-affected landscapes, initial increases in salinity and sodicity result in rapid C mineralisation. Biomass inputs also decrease due to declining vegetation health, followed by further losses as a result of leaching and erosion. The remaining native SOM is then mineralised, until very low SOC stocks remain. However, the C sequestration potential in these degraded areas is high, particularly if rehabilitation efforts are successful in reducing salinity and sodicity. Soil ecosystem functions can then be restored if organic material is available as C stock and for decomposition in the form of either added organic material or inputs from vegetation when these salt-affected landscapes are revegetated.

Global urbanization has resulted in rapidly increased urban land. Soils are the foundation that supports plant growth and human activities in urban areas. Furthermore, urban soils have potential to provide a carbon sink to mitigate greenhouse gas emission and climate change. However, typical urban land development practices including vegetation clearing, topsoil removal, stockpiling, compaction, grading and building result in degraded soils. In this work, we evaluated an urban soil rehabilitation technique that includes compost incorporation to a 60-cm depth via deep tillage followed by more typical topsoil replacement. Our objectives were to assess the change in soil physical characteristics, soil carbon sequestration, greenhouse gas emissions, and stormwater mitigation after both typical urban land development practices and post-development rehabilitation. We found typical urban land development practices altered soil properties dramatically including increasing bulk density, decreasing aggregation and decreasing soil permeability. In the surface soils, construction activities broke macroaggregates into smaller fractions leading to carbon loss, even in the most stable mineral-bound carbon pool. We evaluated the effects of the soil rehabilitation technique under study, profile rebuilding, on soils exposed to these typical land development practices. Profile rebuilding incorporates compost amendment and deep tillage to address subsoil compaction. In the subsurface soils, profile rebuilding increased carbon storage in available and aggregate-protected carbon pools and microbial biomass which could partially offset soil carbon loss resulting from land development. Yet, urban soil rehabilitation increased greenhouse gas emissions while typical land development resulted in similar greenhouse gas emissions compared to undisturbed soils. Additionally, rehabilitated soils had higher saturated soil hydraulic conductivity in subsurface soils compared to other practices which could help mitigate stormwater runoff in urban areas. In our study, we found urban soil management practices can have a significant impact on urban ecosystem service provision. However, broader study integrating urban soil management practices with other ecosystem elements, such as vegetation, will help further develop effective strategies for sustainable cities.
Ph. D.

In the past years considerable attention has been given to soil organic carbon (SOC) stored in permafrost-affected soils in periglacial terrain. Studies have shown that these soils store around half the global SOC pool, making them a key component of the global carbon cycle. Much of the SOC presently stored in these soils has accumulated since the Pleistocene and is protected from decomposition and erosion by low temperatures close to or below the freezing point. This makes it vulnerable to remobilization under a warming climate. This thesis provides new data on SOC storage in three study areas in Siberian periglacial terrain. A high-resolution land cover classification (LCC) for each study area is used to perform detailed vertical and spatial partitioning of SOC. The results show that the vast majority (>86%) of the ecosystem carbon is stored in the top meter of soil. Low relative storage of carbon in plant phytomass indicates limited uptake potential by vegetation and emphasises the vulnerability of the SOC pool to geomorphic changes. Peat formation as well as cryoturbation are identified as the two main pedogenic processes leading to accumulation of SOC. Presence or absence of ice-rich Yedoma deposits determine soil formation and SOC storage at landscape scale. At local scale, periglacial landforms dominate SOC allocation in the tundra, while forest ecosystem dynamics and catenary position control SOC storage in the taiga. A large diversity of soil types is found in these environments and soil properties within pedons can be highly variable with depth. High-resolution satellite imagery allows upscaling of the SOC storage at unprecedented detail, but replication of soil pedons is a limiting factor for mapping of SOC in remote periglacial regions. Future research must look beyond traditional LCC approaches and investigate additional data-sources such as digital elevation models. The concept of state factors of soil formation is advocated as a framework to investigate present day and future SOC allocation in periglacial terrain.

Soils in permafrost regions hold substantial amounts of carbon, much of which has accumulated due to processes that are related to cold temperatures. A warming climate will alter the dynamics governing the fluxes of carbon within a system and consequently the pools of carbon therein. Of particular concern is whether previously stored carbon will be released to the atmosphere contributing to the pool of greenhouse gases and creating a feedback effect. At the moment the International Panel of Climate Change (IPCC) does not include carbon dynamics of the Arctic in their forecast models due to a lack of adequate scientific understanding in the area. Understanding the controls which govern the fluxes of carbon between the land, the atmosphere and the aquatic systems is important in evaluating the transient state of the carbon cycle. This study investigates the potential relationship between terrestrial soil organic carbon (SOC) pools and the dissolved organic carbon (DOC) concentrations in streams observed at the beginning of August 2012 in the Abiskojokka catchment in the sub-arctic region of northern Sweden. The results show that soil organic carbon pools could tentatively explain between 24 % and 44 % of the variation in DOC concentrations in streams. This is only a fraction of the variation explained compared to regions where peatlands are the single most important indicator of DOC concentrations. In the absence of peatland, which covers less than 2 % of the Abiskojokka catchment area, heath vegetation and the associated soil forming processes were shown to be an important indicator of stream water DOC concentrations.

It is well documented that increases in soil organic matter (SOM) improve soil physical properties and increase the overall fertility and sustainability of the soil. Research in SOM storage has recently amplified following the proposal that agricultural soils may provide a significant carbon (C) sink that may aid in the mitigation of increasing atmospheric carbon dioxide. Observed differences in lint yield and nitrogen response from a cotton performance study at the Texas A&M University Experimental Farm near College Station, TX prompted us to examine the effects of tillage and rotation on soil organic C (SOC), soil microbial biomass C (SMBC), 38-day cumulative C mineralization (38-day CMIN), hot-water extractable organic C (hot-WEOC), carbohydrate C, and total glomalin. The treatments examined included conventional-till continuous cotton (CT), reduced-till continuous cotton (RT), and conventional-till cotton after corn rotation (CC) treatments. In pre-plant soil samples, SOC, SMBC, and 38-day CMIN in the top 5 cm were 33, 58, and 79 % greater in RT and 29, 32, and 36 % greater in CC vs. CT. Comparable differences were observed for hot-WEOC and carbohydrate C. Little seasonal variation was observed for labile-C pools throughout the growing season, suggesting minimal C input from cotton roots. Water-stable aggregation was not significantly affected by management, and did not correlate with labile-C pools or total glomalin. Labile-C pools were generally more responsive to management vs. SOC and were strongly correlated with one another. Carbohydrate C of hot-water extracts exhibited the strongest relationships with SMBC and 38-day CMIN, even though it comprised only 3 and 5 % of these pools, respectively. Our data suggest that increasing SOC in Texas cotton-cropping systems through conservation management is possible. Long-term data are still needed to fully address SOC storage potentials in Texas, but increases in labile-C pools resulting from conservation management are attainable and have the potential to positively impact soil fertility.

Eine biochemische Indikation des Anteils exogener organischer Kohlenstoffquellen (EOC), der nach dem Eintrag potenziell im Boden verbleibt (Cpot) wurde entwickelt. Haupthypothese dieser Studie war, dass der Abbau von EOC durch die biochemische Zusammensetzung vorhergesagt werden kann, welche bei Pflanzenrückständen von der Kulturart, dem Pflanzenrückstandstyp sowie dem Anbausystem und im Allgemeinen vom Ausgangssubstrat organischer Düngestoffe und der EOC-Kategorie (pyrogen , mikrobiell und pflanzlich) beeinflusst wird. Zunächst wurden Pflanzenrückstände im Energiepflanzenanbau zur Biogasgewinnung (Restpflanze / Stroh, Stoppeln, Grobwurzeln, Feinwurzeln, natürlicher Bestandsabfall) von Mais, Sorghum, Sudangras, Wintergetreide, Hafer, Erbse in Einzel-, Zwei- und Mischkultursystemen betrachtet. In einem zweiten Schritt wurden Pflanzenrückstände im Allgemeinen mit organischen Düngern, Komposten, Rückständen aus anaerober Vergärung in der Biogasproduktion (Gärrückstände) und Biokohlen verglichen. Die biochemische Zusammensetzung von EOC wurde durch die Konzentrationen von Kohlenstoff- (C), Stickstoff (N), wasserlöslicher Kohlehydrate (WSC), Hemizellulose (HEM), Zellulose (CEL) und Lignin (LIC) in g pro kg Trockenmasse dargestellt. In Inkubationsversuchen wurde EOC gleichmäßig mit Boden vermischt und über 310 Tage die Zugabe-induzierte Kohlendioxid-Freisetzung gemessen. Cpot wurde als Grenzwert der Modellschätzung für die Inkubationsdaten bestimmt. Die Beziehung zwischen biochemischer Zusammensetzung und Cpot wurde durch die Partial-Least-Squares-Regression-Methode abgeleitet. Cpot unterschied sich stärker zwischen verschiedenen organischen Düngestoffen, als speziell zwischen verschiedenen Pflanzenrückständen und konnte durch die biochemische Zusammensetzung vorhergesagt werden. Der Indikator für Cpot (in g C pro kg EOC) wurde als Ipot = 269 + 13 N – 0.5 WSC + 0.7 CEL + 1.5 LIC für Pflanzenrückstände und im Allgemeinen als Ipot = 924 – 1.9 C + 2.0 LIC vorgeschlagen.
A biochemical indication for the fraction of exogenous organic carbon (EOC), potentially remaining in soil after application (Cpot) has been developed. Main hypothesis of this study was that decomposition of EOC can be predicted by the biochemical composition, which in case of plant residues is influenced by the crop residue type, crop species and agricultural management and in general depends on the original substrate and category (pyrogen, microbial, and plant-derived EOC) of organic materials. A first set of EOC was created, containing plant residues in energy crop cultivation for biogas production (shoot / straw, stubble, coarse root, fine root, and litter) of maize, sorghum, sudan grass, winter cereal, pea, and oats in single-, double- and intercropping systems. In a second set of EOC, plant residues in general were compared with other organic fertilisers, urban composts, residues of anaerobic fermentation in biogas production (digestates), and biochar. The biochemical composition of EOC was characterised by the concentrations of carbon (C), nitrogen (N), water-soluble carbohydrates (WSC), hemicelluloses (HEM), cellulose (CEL), and lignin (LIC) in g per kg dry matter. In incubation experiments, EOC was homogeneously incorporated into soil and EOC-induced carbon dioxide-release was measured for 310 d. Cpot was determined as modelled limit for the incubation results. Finally, the relation between biochemical composition and Cpot of EOC was evaluated by the partial least squares regression method. Cpot largely varied between different types and categories of EOC, while less variation was obtained between different plant residues. The biochemical composition was predictive for Cpot (expressed as g C per kg EOC), proposing the biochemical indicator as Ipot = 269 + 13 N – 0.5 WSC + 0.7 CEL + 1.5 LIC specifically for plant residues and as Ipot = 924 – 1.9 C + 2.0 LIC for EOC in general.

Sugarcane cropping is an important component of the Brazil´s economy. As the main feedstock used to produce ethanol, the area occupied with this crop has meaningfully increased in the last years and continues to expand in order to attend to the national and international demand of this biofuel. Despite that it has been demonstrated that land-use transition into sugarcane can negatively impact the soil carbon (C) dynamics, little is known about the effect of those land use changes (LUC) processes on the distribution of soil organic carbon (SOC) within particle-size classes, and how management practices in sugarcane can contribute to the C restoration. In this sense the main objective of this study was to evaluate through a modelling application the SOC dynamics in the sugarcane crop in response to LUC and different management scenarios. For a better understanding of LUC impact on C content in both particulate organic matter and mineral-associated fraction, we performed physical soil C fractionation in 34 study areas involving the three major land-use systems affected by sugarcane expansion. Also, biometric measurements were executed in sugarcane plant and ratoon crop in order to use those data in the model parameterization as well as to recalculate the payback time of the C debt through C conversion ratio reported in the literature. Finally, we parameterized and validate the CENTURY ecosystem model for sugarcane, pastures and annual cropland by using a data-set previously collected by the Laboratório de Biogeoquímica Ambiental (CENA-USP); then different scenarios of sugarcane management were simulated: i) SC1 - Green harvesting; ii) SC2 - Green harvesting plus organic amendments and iii) Green harvesting + low N inputs. Our results showed that the C content depletion for conversion from native vegetation and pastures to sugarcane is caused by C losses in the labile fraction (37%) as wells as in the stabilized pool associated to the mineral fraction (30%). Above and belowground biomass quantification indicated a total sugarcane carbon inputs ranging from 29.6 Mg C ha-1 to 30.6 Mg C ha-1. Considering a C retention rate of 13% we estimated net carbon changes of 0.58 to 0.6 Mg C ha-1 year-1, which contribute to reduce the payback times for sugarcane biofuel carbon debts in 3.3 and 1.2 years for Cerrado wooded and pasture conversions into sugarcane respectively. The modelling study supported the Century model as a tool to access the SOC dynamics following land-use conversion and different soil management in in sugarcane. Long-term simulations suggested that changes in the sugarcane harvest from burning to green harvesting increase the soil C stock in an average of 0.21 Mg ha-1 year-1; however the potential of C accumulation is still higher when organic amendments as vinasse and filter cake are add to the soil, with mean values varying between 0.34 and 0.37 Mg ha-1 year-1 in SC2 and SC1 respectively. By analyzing the SOC dynamic at each scenario simulated, we estimated a time span of 17 and 24 years for soil C restoration in clay and sandy soils under pastures with priority suitability (SC3). The number of years was projected to be higher in clay soils with regular suitability (40 years).
A cultura da cana-de-açúcar é uma comodity importante para a economia no Brasil. Como a principal matéria prima para a produção de etanol, a área plantada com esta cultura tem incrementado significativamente nos últimos anos e a tendência é de continuar se expandindo para atender a demanda nacional e internacional deste biocombustível. Embora tenha sido demostrado que a mudança de uso da terra (MUT) para cana-de-açúcar pode afetar negativamente a dinâmica do carbono (C) no solo, há pouca informação disponível acerca do impacto dessa MUT na distribuição do C nas frações da matéria orgânica do solo, e como as praticas de manejo da cana-de-açúcar podem contribuir para o acumulo de C no solo. Nesse contexto o principal objetivo desta pesquisa foi avaliar, através da modelagem matemática, a dinâmica do carbono orgânico do solo (COS) na cultura da cana-de-açúcar em resposta a mudança de uso da terra e diferentes cenários de manejo agrícola. Fracionamento físico para separar o C associado à matéria orgânica partícula (POM) do C ligado à fração mineral do solo (<53 um) foi realizado em amostras de solo de 34 áreas de estudo envolvendo os três principais sistemas de uso da terra afetados pela expansão da cana-de-açúcar. Adicionalmente, foram realizadas avaliações biométricas da cana-de-açúcar (cana planta e soca) que objetivaram a parametrização do modelo matemático assim como recalcular o tempo de reposição do debito de C gerado. Finalmente, o modelo CENTURY foi parametrizado e devidamente validado, para posteriormente proceder à simulação de diferentes cenários futuros de manejo da cana de açúcar: i) SC1 - Colheita de cana crua (sem queima); ii) SC2 - Colheita de cana crua e adição de adubos orgânicos (vinhaça e torta de filtro); iii) Colheita de cana crua e redução da adubação nitrogenada. Os resultados indicaram que a redução do conteúdo de C devido à conversão de vegetação nativa e pastagem para cana-de-açúcar foi causada pela perda de C tanto na fração lábil (37%) quanto na fração mais estável associada a fração mineral do solo (30%). A quantificação da biomassa aérea e radicular indicou entradas de C variando de 29,6 Mg C ha-1 a 30,6 Mg C ha-1, os quais resultariam em uma taxa de acumulo liquido de 0,58 a 0,6 Mg C ha-1 ano-1, que quando considerado contribui a redução do \"payback time\" do debito de C do etanol causado pela conversão de Cerrado e pastagem em 3,3 e 2 anos respectivamente. Os resultados obtidos no estudo de modelagem matemática suportaram o uso do modelo CENTURY como uma ferramenta para avaliar a influencia da MUT e das práticas de manejo na dinâmica do COS. As simulações em longo prazo sugeriram que a supressão da queima na colheita incrementa o estoque de C em 0,21 Mg ha-1 ano-1. No entanto o potencial de acúmulo de C é ainda maior quando adubação orgânica é realizada, com valores entre 0,34 e 0,37 Mg ha-1 ano-1 respectivamente. A análise da dinâmica do COS em cada cenário de manejo simulado permitiu estimar o tempo médio de recuperação do C do solo perdido pela MUT em áreas de pastagens. Os resultados indicaram um período de 17 anos para condições de cultivo sob solos argilosos e 24 anos para solos arenosos (SC3) em áreas de alta aptidão para expansão. O modelo projetou um maior número de anos em solo argiloso sob áreas de pastagem com aptidão média (40 anos).

Cette thèse aborde un point clé du couplage entre ces cycles: la dynamique des molécules azotées (AAs) des matières organiques du sol (MOS). Par des expériences d'incubation, nous avons estimé que les flux de biosynthèse des AAs par les micro-organismes du sol lors du processus de décomposition sont de l'ordre de 25% de la biomasse nouvellement formée. Le profil des AAs individuels biosynthétisés de novo est plus dépendant du type de sol que de la nature du substrat. Dans chaque sol, il est très similaire à celui des AAs des MOS. La biodégradation de matériaux végétaux marqués en 13C a révélé la transformation rapide des protéines végétales en matériaux microbiens. Ces résultats montrent que les AAs des MOS sont d'origine microbienne. Nous avons mesuré le renouvellement du C des AAs à long terme dans les horizons de surface de neuf sites présentant des végétations, climats et types de sol variés, en utilisant la technique de traçage par les abondances naturelles en 13C. L'âge moyen du carbone des AAs varie de 50 à 200 ans. Un modèle simple permet de discuter les hypothèses du recyclage des AAs des MOS par les micro-organismes. Les rapports isotopiques stables des AAs individuels ont été mesurés par chromatographie en phase gazeuse couplée à la spectrométrie de masse isotopique. À cette fin, nous avons développé une méthode d'étalonnage générique pour la détermination du rapport isotopique des composés spécifiques, par analyse de cultures microbiennes uniformément marquées. Au-delà des résultats présentés, l'étude apporte un large ensemble de données des AAs et examine les variations de l'abondance naturelle en 13C entre les AAs individuels
We analyzed the coupled dynamics of C and N in Soil Organic Matter (SOM) through the dynamics of N-containing soil organic compounds (amino acids (AAs)) by tracing their carbon atoms. Stable isotope ratios of individual amino acids were measured by gas chromatography coupled with isotope ratio mass spectrometry. For this purpose, we developed a generic calibration method for compound-specific stable isotope ratio analysis, based on the analysis of uniformly labelled microbial cultures. We quantified the biosynthesis of AAs associated with the biodegradation process in four contrasted topsoils through short-term incubation experiments of 13C-labelled substrates. Amino acids-C accounts for ca. 25% of the newly-formed microbial biomass-C. The composition of the de novo biosynthesized individual amino acids was dependent on the soil type, and in each soil was similar to that of SOM amino acids. Biodegradation of 13C-labelled plant materials revealed the rapid conversion of plant proteins into microbial materials. These results together demonstrate that SOM amino acids are of microbial origin. We measured the dynamics of amino acids-C on the long term (decades to centuries) in nine sites using the natural 13C-labelling technique. On average, the age of AAs was equal or slightly inferior to that of bulk soil organic carbon, with mean ages ranging from 50 to 200 years. We built a conceptual model of AAs dynamics to discuss various hypotheses of AAs stabilization. Beyond these perspectives on C and N coupling in soil processes, the overall study brings a broad dataset of amino acids, as well as discuses variations of 13C natural abundance (δ13C) in-between individual amino acids

La compréhension du cycle de la matière organique du sol (MOS) est un outil majeur dans la lutte contre le réchauffement climatique, la préservation de la biodiversité ainsi que dans la consolidation de la sécurité alimentaire. Dans ce contexte, cette thèse porte sur la modélisation et l'analyse mathématique de modèles de la dynamique du carbone organique dans le sol.Dans le chapitre 2, nous avons étudié la robustesse et les propriétés mathématiques d'un modèle non linéaire (MOMOS). Nous avons montré que si les données sont périodiques nous obtenons l'existence d'une solution périodique attractive. Le chapitre3 est consacré à la validation mathématique d'un modèle spatialisé basé sur les équations de MOMOS, auxquels nous avons ajouté des opérateurs de diffusion et de transport. L'effet de l'hétérogénéité spatiale sur ce modèle est étudié dans le chapitre4 en utilisant des techniques d'homogénéisation. Suivant la méthodologie de Bosattaet Agren, nous dérivons un autre modèle à qualité continue, qui prend en compte l'effet de l'âge sur la décomposition de la MOS. Le chapitre 5 contient la validation mathématique et expérimentale du modèle. Enfin, nous considérons dans les chapitres6 et 7, un modèle incluant l'effet de la chemotaxie. Nous montrons l'existence, la positivité et l'unicité des solutions dans des domaines suffisamment réguliers de dimension inférieure ou égale à 3
Understanding the soil organic matter (SOM) cycle is a major tool in the effort toreduce global warming, to preserve biodiversity and to improve food safety strategies.In this context, this thesis is about modelling and mathematical analysis of thedynamics of the organic carbon in soil.In chapter 2, we validate mathematically a nonlinear soil organic carbon model(MOMOS) and we prove that, if data is periodic, then there is a unique attractiveperiodic solution. In chapter 3, we focus on the mathematical validation of a spatialmodel derived from MOMOS and where we used diffusion and transport operators.We prove also the existence of a periodic solution. In addition, the effect of soilheterogeneities on the model is studied in chapter 4 using homogenization techniques.Moreover, following the Bosatta and Agren methodology, we derive a continuousquality model taking in consideration the effect of age on the quality of SOM. Wevalidate the model mathematically and experimentally in chapter 5. Finally, weconsider in chapters 6 and 7 another model that takes into account the chemotaxismovement of soil microorganisms. We prove mainly the existence and uniqueness of apositive solution in a regular spatial domain of dimension less or equal to 3

Soil organic matter (SOM) is a well known indicator of soil quality due to its direct influence on soil properties such as structure, soil stability, water availability, cation exchange capacity, nutrient cycling, and pH buffering and amelioration. Study sites were selected in the Valley region of Virginia with the study objectives to: i) compare the efficiency of density solutions used in recovering free-light fraction (FLF) organic matter; ii) compare different soil organic fractions as sensitive indices of short-term changes in SOM due to management practices; iii) investigate on-farm effects of tillage management on soil organic carbon (SOC) and soil organic nitrogen (SON) stocks; and iv) evaluate the role of SOM in controlling soil available nitrogen (N) for corn uptake. The efficiency of the density solutions sodium iodide (NaI) and sodium polytungstate (SPT) in recovering FLF was the same at densities of 1.6 and 1.8 g cm⁻³, with both chemicals presenting less variability at 1.8 g cm⁻³. The sensitivity of SOM fractions in response to crop and soil management depended on the variable tested with particulate organic matter (POM) being the most sensitive when only tillage was tested, and FLF being the most sensitive when crop rotation and cover crop management were added. The on-farm investigation of tillage management on stocks of SOC and total soil N (TSN) indicated significant increases at 0–15 cm depth by increasing the duration (0 to 10 years) of no-tillage (NT) management (0.59 ± 0.14 Mg C ha⁻¹ yr⁻¹ and 0.05 ± 0.02 Mg N ha⁻¹ yr⁻¹). However, duration of NT had no significant effect on SOC and TSN stocks at 0–60 cm depth. Soil available N as controlled by SOM was modeled using corn (Zea mays L.) plant uptake as response and several soil N fractions as explanatory variables. The final model developed for 0–30 cm depth had 6 regressors representing the different SOM pools (active, intermediate, and stable) and a 𝑅² value of 65%. In summary, this study provides information about on-farm management affects on SOM levels; measurement of such effects in the short-term; and estimation of soil available N as related to different soil organic fractions.
Ph. D.

Thesis (M.S.) -- University of Maryland, College Park, 2005.
Thesis research directed by: Dept. of Natural Resource Sciences and Landscape Architecture. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Resolving uncertainties about the cycling of organic carbon in the world's oceans is particularly crucial in the Arctic because it is the locus of deep water formation, as well as rapid environmental change. The specific goal of this thesis was to quantify the flux of soil organic carbon (SOC) to the Arctic Ocean due to erosion along the Yukon Coastal Plain. Ground ice and SOC within coastal sediments, and the current and future fluxes of carbon were examined in detail.
An evaluation of the volume of ground ice showed it to be a significant constituent of coastal bluffs. The amount of it was related to surficial material and geomorphic history, being lowest in coarse-grained marine deposits and highest in lacustrine materials. It made up almost half the soil volume in formerly glaciated areas where bluffs are high, but only one third the volume in unglaciated portions with low bluffs.
Overlooking ground ice resulted in overestimates of SOC and mineral sediment of up to 20%. Corrections were especially important in the upper ice-rich soil layers. Organic carbon contents were related to surficial material and bluff height, and 57% of carbon was located at depths greater than 1 m. SOC fluxes were up to three times higher than previously thought, but comparable to other parts of the Arctic. Eleven per cent of the carbon eroded annually was buried in nearshore sediments, and the carbon in those sediments was overwhelmingly terrigenous.
A morphodynamic model of coastal evolution was used to evaluate future coastal retreat. Low bluffs will retreat more rapidly than higher ones. Ground ice controls the amount of sediment in coastal bluffs and therefore the retreat rates, since bluffs with high ice contents have a lower effective cliff height. SOC fluxes from low coastal bluffs will increase by 29%, but will be offset by a 13% decrease from high bluffs. Regions of low cliffs could become sources of carbon flux to the atmosphere.
By providing insight into the origins and fate of organic matter in a sensitive section of the Arctic coastal system, this study offers valuable input for both current and future studies of regional carbon dynamics.
LES FLUX DE CARBONE ORGANIQUE DU SOL PROVENANT DE L'ÉROSION DES CÔTES PERGÉLISOLÉES, MER DE BEAUFORT CANADIEN
Le cycle du carbone organique dans les océans est d'une importance primordiale, spécialement dans l'Arctique puisqu'ils sont le lieu de formation des eaux abyssales et subissent des changements environnementaux rapides. L'objectif de cette thèse est de quantifier le flux de carbone organique du sol (COS), provoqué par l'érosion, entre la plaine côtière du Yukon et l'Océan arctique. Cette étude examine en détail la teneur en glace et en COS des sédiments côtiers, ainsi que les flux de carbone actuels et projetés.
Une évaluation du volume de la glace de sol révèle qu'elle est une composante importante des falaises côtières. La teneur en glace est liée à la géologie des dépôts de surface et à l'histoire géomorphologique de la région. En effet, cette teneur est plus basse dans les dépôts marins à grain grossier et plus élevée dans les matériaux lacustres. La glace de sol représente presque la moitié du volume du sol dans les zones de hautes falaises antérieurement englacées, mais seulement un tiers du volume dans les régions qui n'ont jamais été englacées et où les falaises sont plus basses.
Le fait de ne pas tenir compte de la glace de sol entraîne des surestimations de la quantité de COS et de sédiment minéral qui atteignent jusqu'à 20%. Les corrections relatives à la glace de sol sont particulièrement importantes, surtout dans les couches riches en glace près de la surface. La teneur en carbone organique dépend de la géologie des dépôts de surface et de la hauteur des falaises. Les résultats montrent que 57% du carbone est situé à des profondeurs supérieures à 1 m. Le flux de carbone organique est trois fois plus élevé que ce qui avait été estimé antérieurement, mais est toutefois comparable aux valeurs calculées pour d'autres régions de l'Arctique. Onze pourcent de la matière organique érodée annuellement est enfouie dans les sédiments marins littoraux et le carbone retrouvé dans ceux-ci est d'origine principalement terrigène.
L`érosion côtière future a été évaluée à l'aide d'un modèle d`évolution côtière morphodynamique. Le modèle démontre que les falaises basses reculeront plus rapidement que celles qui sont plus hautes. Puisque les falaises qui possèdent une teneur en glace de sol élevée ont une hauteur effective moindre, cette glace de sol a un impact sur le montant de sédiment et sur le taux de recul des falaises. Le flux de COS des falaises basses augmentera de 29%, mais sera atténué par une baisse de 13% dans le flux de COS des falaises hautes. Les régions où les falaises sont basses pourraient devenir des sources de dioxyde de carbone pour l'atmosphère.
Cette recherche apporte une contribution importante aux études actuelles et futures de la dynamique régionale du carbone; elle offre de nouvelles perspectives sur les origines et le sort de la matière organique dans une région sensible du système côtier arctique.

Soil carbon (C) and nitrogen (N) are predominantly in organic form. Proteins/ peptides, as an important organic form of N, constitute a substantial part of soil organic matter. On one hand, proteins/peptides are an important N source for plants and microorganisms, particularly in soils where inorganic N is limited. On the other hand, their stabilization in soils by forming organo-mineral associates or macromolecule complex reduces the C loss as CO2 into the atmosphere. Therefore, studies on the turnover, abundance, composition, and stability of proteins/peptides are of crucial importance to agricultural productivity and environmental sustainability. In the first part of this study, the bioavailability and distribution of amino acids, (building block of proteins/peptides), were investigated, in soils across the North-South and West-East transects of continental United States. The second part of this study aimed to understand the variations of organic C speciation in soils of continental United States. Previous investigations of the interactions between soil minerals and proteins/peptides were mostly limited to batch sorption experiments in labs, seldom of which gave the details at the molecular scales. Therefore, in the third part of this study, the molecular orientation of self-assembled oligopeptides on mineral surfaces was investigated by employing synchrotron based polarization-dependent Near Edge X-ray Adsorption Fine Structure Spectroscopy (NEXAFS) techniques. Specific aims of this study were: 1) to assess potentially bioavailable pool of proteinaceous compounds and the immediately bioavailable pool of free amino acids in surface and subsurface soils of various ecosystems; 2) to evaluate the relationship between environmental factors and levels/composition of the two pools; 3) to investigate the organic C speciation in soils of various land use; and 4) to understand molecular level surface organization of small peptides on mineral surfaces. The levels of free amino acids and hydrolysable amino acids which represent the potentially bioavailable pool of proteinaceous compounds in A-horizon soils were significantly high than in C-horizon soils due to the accumulation of organic matter in surface. On average, free amino acids accounted for less than 4 % of hydrolysable amino acids which represent the total proteinaceous compounds in soils. The composition of free amino acids was significantly different between surface soil and subsurface soil and was significantly influenced by mean annual temperature and precipitation. A relatively uniform composition of hydrolysable amino acids was observed irrespective of a wide range of land use. Significant variations were observed for the levels of free and hydrolysable amino acids along mean annual temperature and precipitation gradients, as well as among vegetation types of continental USA, suggesting levels of free and hydrolysable amino acids were associated with the above-ground biomass and root distribution. Organic C speciation investigation revealed the presence of carboxylic-C (38%), aliphatic-C (~ 22%), aromatic-C (~ 18%), O/N-alkyl-C (~ 16%), and phenolic-C (< 6%). Factors such as temperature and vegetation cover were revealed in this study to account for the fluctuations of the proportions of aromatic-C and phenolic-C, in particular. Phenolic-C may serve as a good indicator for the effect of temperature or vegetation on the composition of SOC. The average composition of soil organic C, over the continental scale, was relatively uniform over various soil ecosystems and between two soil horizons irrespective of surface organic C content. Polarization dependent NEXAFS analysis showed the oligopeptides tend to orient on mineral surface with an average tilt angle of 40 ° between the molecular chain and the mineral surface.
Ph. D.

Management practices that may increase soil organic matter (SOM) storage include conservation tillage, especially no till (NT), enhanced cropping intensity, and fertilization. My objectives were to evaluate management effects on labile [soil microbial biomass (SMB) and mineralizable, particulate organic matter (POM), and hydrolyzable SOM] and slow (mineral-associated and resistant organic) C and N pools and turnover in continuous sorghum [Sorghum bicolor (L.) Moench.], wheat (Triticum aestivum L.), and soybean [Glycine max (L.) Merr.], sorghum-wheat/soybean, and wheat/soybean sequences under convent ional tillage (CT) and NT with and without N fertilization. A Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochepts) in southern central Texas was sampled at three depth increments to a 30-cm depth after wheat, sorghum, and soybean harvesting. Soil organic C and total N showed similar responses to tillage, cropping sequence, and N fertilization following wheat, sorghum, and soybean. Most effects were observed in surface soils. NT significantly increased SOC. Nitrogen fertilization significantly increased SOC only under NT. Compared to NT or N addition, enhanced cropping intensity only slightly increased SOC. Estimates of C sequestration rates under NT indicated that SOC would reach a new equilibrium after 20 yr or less of imposition of this treatment. Labile pools were all significantly greater with NT than CT at 0 to 5 cm and decreased with depth. SMB, mineralizable C and N, POM, and hydrolyzable C were highly correlated with each other and SOC, but their slopes were significantly different, being lowest in mineralizable C and highest in hydrolyzable C. These results indicated that different methods determined various fractions of total SOC. Results from soil physical fractionation and 13C concentrations further supported these observations. Carbon turnover rates increased in the sequence: ROC < silt- and clayassociated C < microaggregate-C < POM-C. Long-term incubation showed that 4 to 5% of SOC was in active pools with mean residence time (MRT) of about 50 days, 50% of SOC was in slow pools with an average MRT of 12 years, and the remainder was in resistant pools with an assumed MRT of over 500 years.

Thesis (M.S.)--West Virginia University, 2002.
Title from document title page. Document formatted into pages; contains x, 282 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

ABSTRACT M.Sc.Amanda D. BambrickNatural Resource Sciences Tree-based intercropping (TBI) is an agroforestry system where a crop, generally an annual, is planted between established tree rows. TBI systems have a greater potential for carbon storage than conventional cropping systems because carbon is stored in the biomass of growing trees and trees provide additional carbon inputs (leaves, roots) that contribute to the soil organic carbon (SOC) pool. Differences in the litter quality and amount of litter deposited in the tree row versus the intercropped space are expected to generate spatial heterogeneity in the SOC pool. The objectives of this work were to evaluate the spatial variability of the SOC pool in TBI systems, to compare SOC stocks in the TBI system with a nearby conventional agroecosystem, and to describe the SOC dynamics in a TBI system using the ecosys model. Research sites included in this study were 4-year old TBI sites at St. Paulin and St. Edouard (Quebec, Canada), an 8-year old TBI site in St. Remi, Quebec, and a 21 year old TBI site in Guelph, Ontario, Canada. Spatial heterogeneity in SOC pools due to the presence of trees was observed in two of the four sites, but obscured by field variability at one site and even distribution of leaf litter associated with large trees at the oldest TBI site. The SOC pool increased in older TBI sites, relative to the nearby conventional agroecosystem, but the magnitude of SOC change was affected by the land use history. A simulation of changes in SOC using the ecosys environmental model predicted a 5.0% decrease in SOC pools twenty-one years after the site was converted to TBI, while field experiments showed a 12% increase in the SOC pool compared to the conventional agroecosystem. A spatial algorithm that describes the distribution of trees and crops in TBI systems would improve ecosys model predictions. Overall, field results suggest that the trees growing in TBI systems will increase SOC levels after a n
RESUMÉM.Sc.Amanda D. BambrickSciences de ResourcesNaturellesUn système de culture intercalaire (SCI) est un système d’agrosylviculture où une récolte, généralement annuelle, est établie entre les rangées d'arbres plantées. Le SCI a un potentiel important pour être adoptés dans les régions tempérées dû aux avantages environnementaux liés à ces systèmes. Un tel avantage environnemental fourni par SCI est le stockage accru de carbone dans les sols et la biomasse des plantes. Le SCI a un potentiel important pour le stockage de carbone (C) car il contienne de carbone dans la biomasse des arbres croissants, et l’ajout au sol des résides d’arbres (feuilles, racines) contribuent au C organique du sol (SOC). On s'attend à ce que des différences dans la qualité et la quantité des résides organiques déposées dans la rangée d'arbre contre l'espace intercalaire produisent de l'hétérogénéité spatiale de SOC. Les objectifs de cette thèse étaient i) d'évaluer la variabilité spatiale de SOC dans le SCI, ii) comparer des stocks de SOC dans le SCI à un agro-écosystème conventionnel, et iii) décrire la dynamique de SOC dans le SCI utilisant le model ecosys. Les sites expérimentaux incluant dans cette étude étaient des emplacements de quatre ans à St. Paulin et St. Édouard (Québec, Canada), de huit ans à St. Rémi, Québec et de 21 ans à Guelph (Ontario, Canada). L'hétérogénéité spatiale au SOC due à la présence des arbres a été observée dans deux des quatre sites, mais obscurcie par la variabilité de terrain a un site et par la distribution égale de feuillage liée à de grands arbres à l'emplacement de SCI le plus ancien. Le stock de SOC accrue dans des sites de SCI le plus anciens, relativement à l'agro-écosystème conventionnel, mais l'importance de changement de SOC a été affectée par l'histoire d'utilisation de la terre. Une simulation des changements du SOC utilisant le modèle ecosys a prévu une diminut

Arctic soils contain a large fraction of our planets terrestrial carbon (C) pool. When tundra soils become warmer and permafrost thaws, non-native geoengineering earthworms can enter these soils and ingest organic matter accumulated over long timescales. Previous studies have found that earthworms increase mineralization rates of soil organic matter into carbon dioxide (CO2) when introduced. Yet, this initial mineralization boost seems transient with time and it has been hypothesized that earthworms stimulate the formation of persistent C forms. In this study, I investigated how non-native, geoengineering earthworms affected the relative proportions of seven carbon forms in the O and A1 horizon of tundra soil and if their effect induced a change in pH. I used Nuclear Magnetic Resonance (NMR) spectroscopy to understand what happens to soil carbon compounds in two different tundra vegetation types (heath and meadow), that had been subjected to earthworm treatment for three summers. I found that O-aromatic C increased from 7.22% ± 0.24 (mean ± stderr) in the meadow soil lacking earthworms to 8.98% ± 0.30 in the meadow exposed to earthworms, and that aromatic C increased from 8.71% ± 0.23 to 9.93% ± 0.25. In similar, the result suggested that alkyl C decreased in this vegetation type from 20.43% ± 0.38 to 18.70% ± 0.25 due to earthworm activities. I found no effect on the chemical properties in the heath. I conclude that geoengineering earthworms affect the two vegetation types differently and that earthworms seem to enhance the accumulation of recalcitrant aromatic C forms.

Soil carbon storage in tropical ecosystems is important in the global carbon cycle, yet consensus is lacking on how soil organic carbon stocks are altered under anthropogenic land-use change. This thesis seeks to quantify soil carbon stocks, the associated soil carbon emissions and explores the drivers of soil respiration in managed tropical Andean lands over a 2600 m elevation gradient. It investigates: grazing and burning on high altitude montane grasslands, burning in montane forests and agriculture in premontane forests. Changes among land-uses were quantified using belowground carbon stocks, the carbon distribution among density fractions, soil carbon emissions and environmental drivers of soil respiration. Soil respiration was a good proxy of soil carbon loss in premontane pastures and montane grassland soils. The total carbon stocks on some land-uses appeared to be unaffected but the distribution of carbon within the soil had changed and even when there were no net changes in soil carbon emissions, the drivers of respiration were different. The synergistic effect of burning and grazing in montane grasslands was the most detrimental to soil carbon stocks, whereas montane forests were unaffected. In the premontane elevation, soil carbon loss was dependent on the type of agricultural practice but the succession of secondary forest allowed soil carbon to recover to similar levels measured in the mature forest. These findings highlight the fact that although land-use does not always appear to have an obvious effect on total soil carbon stocks, the loss of carbon from short-term labile pools can cause higher carbon emissions and dominate soil-atmospheric feedbacks. Furthermore, the drivers of soil respiration and the synergistic relationship between soil moisture and temperature alter under different land uses. These factors should be taken into consideration with regards to predictions of regional temperature/precipitation climate change and soil carbon management policy in order to arrive at more realistic decisions.

Soil organic carbon represents the largest constituent of the global C pool and carbon budgets are studied by researchers and modelers in C cycling, global climate change, and soil quality studies. Pedon and soil interpretation record databases are used with soil and ecological maps to estimate regional SOC even though these databases are rarely complete for surface litter and mineral subsurface horizons. The first main objective of the project is to improve the ability to produce soil organic carbon estimates from existing spatial soils datasets, such as STATSGO. All records in the STATSGO Layer table that were incomplete or appeared to be incorrectly filled with a null or zero value were considered invalid. Data sorting procedures and texture lookup tables were used to identify exiting correct (valid) data entries that were used to substitute invalid records. STATSGO soil property data were grouped by soil order, MLRA, layer number, and texture to produce replacement values for all invalid data used to calculate mass SOC. Grouping criteria was specific to each variable and was based on texture designations. The resulting filled and unfilled tables were used with procedures assuming Normal and Lognormal distribution of parameters in order to analyze variation of mass SOC estimates caused by using different computation techniques. We estimated mass SOC to 2 m in Maine and Minnesota using filled and unfilled STATSGO data tables. Up to 54% of the records in Maine and up to 80% of the records in Minnesota contained null or zero values (mostly in fields related to rock fragments) that were replaced. After filling, the database resulted in 1.5 times higher area-weighted SOC. SOC calculated using the Normal distribution assumption were 1.2 to 1.5 times higher than those using the Lognormal transformation. SOC maps using the filled tables had more logical geographic SOC distribution than those using unfilled tables. The USDA Forest Service collects and maintains detailed inventory data for the condition and trends of all forested lands in the United States. A wide range of researchers and landowners use the resulting Forest Inventory and Analysis (FIA) database for analytical and decision making tasks. FIA data is available to the public in transformed or aggregate format in order to ensure confidentiality of data suppliers. The second main objective of this project was to compute SOC (kg m-2) results by FIA forest type and forest type group for three depth categories (25 cm, 1 m, and 2 m) at a regional scale for the 48 contiguous United States. There were four sets of results derived from the filled STATSGO and FIA datasets for each depth class by region: (1) SOC computed by the Lognormal distribution approach for (1a) all soil orders, (1b) without Histosols; and (2) SOC computed by the Normal distribution approach for (2a) all soil orders, (2b) without Histosols. Two spatial forest cover datasets were relevant to this project, FIA and AVHRR. We investigated the effects of FIA inventory data masking for Maine and Minnesota, such as plot coordinates rounding to the nearest 100 arc-second, and the use of 1 km resolution satellite-derived forest cover classes from AVHRR data, on SOC estimates to 2 m by forest type group. SOC estimates by soil mapping unit were derived from fixed STATSGO database tables and were computed by the Lognormal distribution approach including all soil orders. The methods in this study can be used for a variety of ecological and resource inventory assessments and the automated procedures can be easily updated and improved for future uses. The procedures in this study point out areas that could benefit the most during future revisions of STATSGO. The resulting SOC maps are dynamic and can be rapidly redrawn using GIS whenever STATSGO spatial or tabular data undergo updating. Use of pedon data to define representative values for all properties in all STATSGO layers and correlation of STATSGO layers to soil horizons will lead to vast improvement of the STATSGO Layer table and promote its use for mass SOC estimation over large regions.
Master of Science

Permafrost regions in the Northern Hemisphere store large amounts of organic carbon and are vulnerable to climate change. Due to a sustained warming of the climate, strongest in the northern high latitudes, permafrost thaws and organic carbon could be released in significant amounts which should not be neglected. This study investigates the soil organic carbon (SOC) storage in the Tarfala Valley (600 – 2’100 m a.s.l.), Northern Sweden, and aims to give a first estimation of the total  carbon stock in a sub-arctic high alpine permafrost environment. Further the study describes the actual extent of permafrost in the Tarfala Valley. To achieve these aims, two field studies were carried out, one in summer to collect soil samples and one in winter to measure the bottom temperature of snow (BTS). In addition, the soil samples were analysed in the laboratory for bulk density, loss on ignition and elemental analyses. The estimated total SOC in the Tarfala catchment area of 31.2 km2 is 23.0 kt C for 0 – 30 cm and 28.2 kt C for 0 – 100 cm, which is on average 0.9 kg C m-2 for the upper meter of soil in the study area. Even though the soil organic carbon values are relatively low, these results  contribute to the on-going soil organic carbon inventories in the circum-arctic. In Tarfala Valley, permafrost can be considered as continuous at an altitude above 1’561 m a.s.l., discontinuous above 1’218 m a.s.l. and sporadic above 875 m a.s.l. based on a logistic regression model with the altitude as single independent variable. This implies that most of the permafrost affected ground is at an altitude where only sparse or no vegetation is present and only low amounts of organic carbon is stored. In brief, Tarfala Valley cannot be considered as a permafrost carbon hotspot, because this sub-arctic alpine environment does not have the potential to release large amounts of carbon as a result of climate warming and permafrost thawing.
Permafrost regioner i norra halvklotet lagrar stora mängder av organiskt kol och är känsliga för klimatförändringar. På grund av en pågående klimatuppvärmning, som är starkast i nordliga höga breddgrader, kan permafrosten tina och frisläppa stora mängder av organiskt kol som skulle kunna ha oförutsedda konsekvenser. Denna studie undersöker organiskt kol lagring i marken i Tarfaladalen (600 – 2’100 m.ö.h.), i norra Lappland i Sverige och försöker att beräkna den totala mängden av organiskt kol lagrad i denna subarktiska högalpina miljö. Denna studie beskriver ytterligare den aktuella permafrostutbredningen i Tarfaladalen. Hela  examensarbetet är baserat på två fältstudier varav en genomfördes på sommaren för att samla in jordprover och den andra genomfördes på vintern för att mäta bottentemperaturen av snön. Jordprover analyserades i laboratorium för bulk density, loss on ignition och elemental analysis metoderna. Det totalt beräknade organiskt kol i marken i 31.2 km2 stor Tarfaladalen omfattas 23.0 kt C för 0 – 30 cm och 28.2 kt C för 0 – 100 cm, som resulterar i ett medelvärde av 0.9 kg C m-2 för första övre metern av marken. Även om de beräknade mängderna av organiskt kol är ganska små, så bidrar denna studie till de pågående undersökningarna kring organiskt kol i  permafrostmarken runt arktis. Permafrostförekomsten i Tarfaladalen betraktas som kontinuerlig över 1’561 m.ö.h. och diskontinuerlig mellan 1’218 och 1’561 m.ö.h. Mellan 875 och 1’218 m.ö.h. betraktas permafrosten som sporadisk. Dessa värden baseras på en logistisk regressionsmodell med höjden som enda variabel men visar att den stora delen av permafrostmarken ligger på hög altitud, vilket innebär att det bara finns lite eller ingen vegetation och inga stora mängder av organiskt kol i permafrostmarken. Slutligen kan man säga att Tarfaladalen inte är någon hotspot för organiskt kol eftersom det där området inte har någon stor potential att släppa fri stora mängder av organiskt kol under ett varmare klimat och tinande  permafrosten.

Developed countries' growing awareness of greenhouse gas (CO2, CH4, N2O) emissions from agricultural soils has led to an increased interest in the management of soil organic matter (SOM), which now extends to developing countries, including Bangladesh. Bangladeshi agriculture follows a largely rice-based cropping rotation, for which insufficient site-specific information regarding gas emissions exists to identify temporal variability of SOM content. The objective of this study was to evaluate the applicability of the 'Denitrification-Decomposition' model (DNDC, version 9.3) as a tool to better understand SOC trends in tropical agriculture. DNDC was used to simulate gas emissions from 1948 to 1969 and 1981 to 2007, under farm management practices prevalent in the Dinajpur district of Bangladesh. Forty-nine years of historical daily precipitation and temperature data were used for simulation with DNDC, such that both aerobic and anaerobic conditions were experienced in any given year. A "summer rice - monsoon rice - wheat" cropping pattern was used. As the input parameters of annual precipitation and flooding duration would likely affect DNDC-simulated results, model outputs were categorized on the basis of the magnitude of these parameters. In each categorization scheme the output data were sorted either based on (i) mean, (ii) probability of exceedance, or (iii) standard deviation of annual precipitation or flooding duration. An analysis was then conducted of correlations among input and output variables. Relationships between simulated variables like CO2 emissions, CH4 emissions, and change in SOC content, and input variables such as annual precipitation and flooding duration were generally similar under both of categorization schemes. In high precipitation years changes in SOC content showed a negative correlation (r = 0.90, P ≤ 0.05) with CO2 emissions, and a positive correlation with CH4 emissions (r = 0.85, P ≤ 0.05), highlighting the importance of studying gas emissions as part of the net C balance embedded in DNDC. When categorized according to annual precipitation, CO2 and CH4 emissions were negatively correlated; however, no significant relationship existed when emissions data were categorized on the basis of flooding duration. This discrepancy might arise from the way in which DNDC computes the soil's net C balance. In physical systems, CH4 emissions from paddy fields have an important effect on SOC; however, DNDC calculates CH4 emissions based on available organic C generated by the decomposition sub-model, but the net change in SOC is only balanced according to the CO2 gas emissions calculated by decomposition sub-model. Thus, the CH4 emission calculated by the fermentation sub-model is not included as a loss of SOC in the C balance. The consequence of this in the output data was a steadily increasing SOC associated with the increase in CH4 emissions from the simulated soil system. In order to more accurately model the soil carbon balance in tropical agricultural systems with flooded soils, DNDC should be modified to take into consideration C lost through CH4 emissions in addition to those lost as CO2. DNDC might then be used in sensitivity analysis for different farm management practices under paddy-based cropping systems. Physical experimental analysis is also important for validation of the modelling work. This study showed that DNDC can serve as a rough tool to represent change in the SOC content under Bangladeshi agricultural practices. Some modifications of DNDC, however, would be desirable to make it better suited for future work of this kind.
La plus grande prise de conscience des pays développés quant aux émissions de gaz à effet de serre (CO2, CH4, N2O) provenant de sols agricoles a mené à un intérêt accru pour une gestion durable de la matière organique du sol (MOS). Cet intérêt s'étend maintenant à plusieurs pays en voie de développement, dont le Bangladesh. L'objectif de cette étude fut d'évaluer l'applicabilité du modèle informatique 'Dénitrification-Décomposition' (DNDC, version 9.3) comme outil permettant de mieux comprendre les tendances en MOS dans le contexte de l'agriculture des tropiques. Le DNDC servit à simuler les émissions de gaz à effet de serre de 1948 à 1969 et de 1981 à 2007, selon les modes de gestion agricole prévalent dans le district de Dinajpur, au Bangladesh. Une historique de précipitations et températures quotidiennes de 49 ans servit à alimenter les simulations avec DNDC, de façon à ce que des conditions aérobies et anaérobies aient lieu en toute année donnée. Une rotation de cultures "riz d'été - riz mousson - blé" fut employée. Comme les paramètres d'entrée (précipitation annuelle et durée d'inondations) auraient probablement un effet sur les résultats simulés par DNDC, les variables de sortie furent triées selon l'échelle de chacun des paramètres d'entrée. Pour chaque mode de catégorisation les variables de sortie furent triées selon soit (i) la moyenne, (ii) la probabilité de dépassement, or (iii) et l'écart type de la précipitation annuelle ou de la durée annuelle d'inondations. Une analyse fut ensuite conduite des corrélations entre les variables d'entrée et de sortie. Le type de corrélation existant entre les variables de sortie simulées (émissions de CO2, émissions de CH4, et variation en MOS) et les variables d'entrée (précipitation annuelle, durée d'inondations) fut généralement semblable pour les deux critères de tri. Lors d'années de précipitation élevée la variation en MOS fut inversement corrélée (r = 0.90, P ≤ 0.05) aux émissions de CO2, et directement corrélée aux émissions de CH4 émissions (r = 0.85, P ≤ 0.05), soulignant l'importance qu'il y a d'étudier les émissions de gaz par l'entremise du module de bilan global en C de DNDC. Lorsque trié selon la précipitation annuelle, les émissions de CO2 and CH4 furent inversement corrélées, tandis que lorsque le tri se fit selon la durée des inondations aucune corrélation significative n'apparut. Cette divergence s'avère peut-être le résultat de la façon par laquelle DNDC calcul le bilan en C du sol. Dans le monde réel, les émissions de CH4 provenant de rizières submergées ont un important effet sur la MOS. Cependant, DNDC calcule les émissions de CH4 selon le carbone organique disponible calculé par le module de décomposition, mais le bilan global en MOS n'est ajusté que pour le CO2 émis par le module de décomposition. Ainsi, les émissions de CH4 calculées par le module de fermentation ne sont pas prises en compte comme une perte en MOS dans le bilan de C. Par conséquence les données de sortie indiquèrent une augmentation progressive en MOS, associée à une augmentation en émissions de CH4 provenant du sol simulé. Afin de modeler plus précisément le bilan en C du sol dans les systèmes agricoles des tropiques à sols inondés, DNDC devrait être modifié afin de prendre en compte les pertes en C sous forme d'émissions de CH4 en plus de celles sous forme de CO2. Le DNDC pourrait alors servir à une analyse de sensibilité qui examinerait différentes pratiques de gestion agricole pour les rizières. Une analyse physique d'expériences sur le terrain s'avèrerait utile à une validation des travaux de modélisation. Cette étude démontra que DNDC peut servir d'outil approximatif pour représenter les variations en MOS advenant des pratiques agricoles courantes au Bangladesh. Cependant, il serait souhaitable que certaines modifications soient faites au modèle DNDC, pour qu'il soit mieux adapté à de futures utilisations de ce genre.