Добірка наукової літератури з теми "Forest and humid savannah ecosystems"

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Статті в журналах з теми "Forest and humid savannah ecosystems":

1

Leach, Melissa, Bernard Bett, M. Said, Salome Bukachi, Rosemary Sang, Neil Anderson, Noreen Machila, et al. "Local disease–ecosystem–livelihood dynamics: reflections from comparative case studies in Africa." Philosophical Transactions of the Royal Society B: Biological Sciences 372, no. 1725 (June 5, 2017): 20160163. http://dx.doi.org/10.1098/rstb.2016.0163.

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This article explores the implications for human health of local interactions between disease, ecosystems and livelihoods. Five interdisciplinary case studies addressed zoonotic diseases in African settings: Rift Valley fever (RVF) in Kenya, human African trypanosomiasis in Zambia and Zimbabwe, Lassa fever in Sierra Leone and henipaviruses in Ghana. Each explored how ecological changes and human–ecosystem interactions affect pathogen dynamics and hence the likelihood of zoonotic spillover and transmission, and how socially differentiated peoples’ interactions with ecosystems and animals affect their exposure to disease. Cross-case analysis highlights how these dynamics vary by ecosystem type, across a range from humid forest to semi-arid savannah; the significance of interacting temporal and spatial scales; and the importance of mosaic and patch dynamics. Ecosystem interactions and services central to different people's livelihoods and well-being include pastoralism and agro-pastoralism, commercial and subsistence crop farming, hunting, collecting food, fuelwood and medicines, and cultural practices. There are synergies, but also tensions and trade-offs, between ecosystem changes that benefit livelihoods and affect disease. Understanding these can inform ‘One Health’ approaches towards managing ecosystems in ways that reduce disease risks and burdens. This article is part of the themed issue ‘One Health for a changing world: zoonoses, ecosystems and human well-being’.
2

Bond, William J., and Guy F. Midgley. "Carbon dioxide and the uneasy interactions of trees and savannah grasses." Philosophical Transactions of the Royal Society B: Biological Sciences 367, no. 1588 (February 19, 2012): 601–12. http://dx.doi.org/10.1098/rstb.2011.0182.

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Savannahs are a mixture of trees and grasses often occurring as alternate states to closed forests. Savannah fires are frequent where grass productivity is high in the wet season. Fires help maintain grassy vegetation where the climate is suitable for woodlands or forests. Saplings in savannahs are particularly vulnerable to topkill of above-ground biomass. Larger trees are more fire-resistant and suffer little damage when burnt. Recruitment to large mature tree size classes depends on sapling growth rates to fire-resistant sizes and the time between fires. Carbon dioxide (CO 2 ) can influence the growth rate of juvenile plants, thereby affecting tree recruitment and the conversion of open savannahs to woodlands. Trees have increased in many savannahs throughout the world, whereas some humid savannahs are being invaded by forests. CO 2 has been implicated in this woody increase but attribution to global drivers has been controversial where changes in grazing and fire have also occurred. We report on diverse tests of the magnitude of CO 2 effects on both ancient and modern ecosystems with a particular focus on African savannahs. Large increases in trees of mesic savannahs in the region cannot easily be explained by land use change but are consistent with experimental and simulation studies of CO 2 effects. Changes in arid savannahs seem less obviously linked to CO 2 effects and may be driven more by overgrazing. Large-scale shifts in the tree–grass balance in the past and the future need to be better understood. They not only have major impacts on the ecology of grassy ecosystems but also on Earth–atmosphere linkages and the global carbon cycle in ways that are still being discovered.
3

Madjima, Soro Nounfro, Ehouman N’guetta Moïse, Toure Mamadou, Ouattara Noufou Doudjo, and Tiho Seydou. "Diversité Et Dynamique Des Communautés De Vers De Terre De Trois Formations Végétales Dans Une Savane Humide De l’Afrique De l’Ouest (Lamto, Côte d’Ivoire)." European Scientific Journal, ESJ 14, no. 27 (September 30, 2018): 281. http://dx.doi.org/10.19044/esj.2018.v14n27p281.

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The maintenance and stability of many terrestrial ecosystems are in part related to the ecosystem functions and services of soil organisms. The present study aims to evaluate the influence of litter biomass produced by three types of vegetation in the Lamto reserve on the dynamics of earthworm community. Each vegetation formations has been subdivided into 3 parcels. These parcels were geo-referenced using a GPS and mapped using QGIS software. For each plot, 25 points were randomly selected using their GPS coordinates. The litters were collected by manual collection to evaluate their biomass. Monoliths of the TSBF (Tropical Soil Biology) type were dug in order to collect the earthworms by direct manual sorting. Also, soil clumps were collected to determine the organic matter levels by the method of lossto-fire. In total, 12 species of earthworms belonging to 3 ecological categories were collected. The forest block had the highest density of earthworms with a predominance of epigeic earthworms followed by grassy savannah with a predominance of endogeic earthworms. The wooded savannah has the lowest density of earthworms with a predominance of anecic earthworms. In terms of species richness, the grassy savannah contained the greatest number of earthworm species followed by the wooded savannah and the forest block that had the same number of species. In the three vegetations formations, it was found that earthworm densities were correlated with litter biomass as well as organic matter levels (correlation between earthworm density and litter biomass: r 2 =0, 75; correlation between density of earthworms and the rate of organic matter: r 2 =0, 93).
4

Burbridge, Rachel E., Francis E. Mayle, and Timothy J. Killeen. "Fifty-thousand-year vegetation and climate history of Noel Kempff Mercado National Park, Bolivian Amazon." Quaternary Research 61, no. 2 (March 2004): 215–30. http://dx.doi.org/10.1016/j.yqres.2003.12.004.

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Pollen and charcoal records from two large, shallow lakes reveal that throughout most of the past 50,000 yr Noel Kempff Mercado National Park, in northeastern lowland Bolivia (southwestern Amazon Basin), was predominantly covered by savannas and seasonally dry semideciduous forests. Lowered atmospheric CO2 concentrations, in combination with a longer dry season, caused expansion of dry forests and savannas during the last glacial period, especially at the last glacial maximum. These ecosystems persisted until the mid-Holocene, although they underwent significant species reassortment. Forest communities containing a mixture of evergreen and semideciduous species began to expand between 6000 and 3000 14C yr B.P. Humid evergreen rain forests expanded to cover most of the area within the past 2000 14C yr B.P. coincident with a reduction in fire frequencies. Comparisons between modern pollen spectra and vegetation reveal that the Moraceae-dominated rain forest pollen spectra likely have a regional source area at least 2–3 km beyond the lake shore, whereas the grass- and sedge-dominated savanna pollen spectra likely have a predominantly local source area. The Holocene vegetation changes are consistent with independent paleoprecipitation records from the Bolivian Altiplano and paleovegetation records from other parts of southwestern Amazonia. The progressive expansion in rain forests through the Holocene can be largely attributed to enhanced convective activity over Amazonia, due to greater seasonality of insolation in the Southern Hemisphere tropics driven by the precession cycle according to the Milankovitch Astronomical Theory.
5

Smith, Richard J., and Francis E. Mayle. "Impact of mid- to late Holocene precipitation changes on vegetation across lowland tropical South America: a paleo-data synthesis." Quaternary Research 89, no. 1 (November 10, 2017): 134–55. http://dx.doi.org/10.1017/qua.2017.89.

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AbstractA multi-proxy paleo-data synthesis of 110 sites is presented, exploring the impact of mid- to late Holocene precipitation changes upon vegetation across Southern Hemisphere tropical South America. We show that the most significant vegetation changes occurred in southwest Amazonia and southeast Brazil, regions reliant on precipitation derived from the South American summer monsoon (SASM). A drier mid-Holocene in these regions, linked to a weaker SASM, favored more open vegetation (savannah/grasslands) than present, while increased late-Holocene precipitation drove expansion of humid forests (e.g., evergreen tropical forest in southwest Amazonia,Araucariaforests in southeast Brazil). The tropical forests of central, western and eastern Amazonia remained largely intact throughout this 6000-year period. Northeastern Brazil’s climate is “antiphased” with the rest of tropical South America, but a lack of paleo-data limits our understanding of how vegetation responded to a wetter (drier) mid-(late) Holocene. From this paleo-data perspective, we conclude that ecotonal forests already close to their climatic thresholds are most vulnerable to predicted future drought, but the forest biome in the core of Amazonia is likely to be more resilient. Of greater concern are widespread deforestation and uncontrolled anthropogenic burning, which will decrease ecosystem resilience, making them more vulnerable than they might be without current anthropogenic pressures.
6

Sulaiman, Muhammad Ikhsan, Rita Andini, Murna Muzaifa, Leni Marlina, Rachman Jaya, Ali M. Muslih, and Heru P. Widayat. "Making biodiversity work for coffee production. A case study of Gayo Arabica coffee in Indonesia." MOJ Ecology & Environmental Sciences 6, no. 4 (August 6, 2021): 156–62. http://dx.doi.org/10.15406/mojes.2021.06.00228.

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Biodiversity is defined as the variety of life encompassing the ‘existing’ variations at all level, starting from the tiny genes within a species up to a broader sense consisted of habitats within ecosystem. It is urgently needed as long as human is still exist on this earth. Therefore, its proper utilization and correct application of biodiversity bring great advantage in tangible and non-tangible benefits. Indonesia is known as the third largest biodiversity hotspots; both its flora and fauna. It has also tremendous diverse ecosystems extended from west to east; with amplitude of variation ranging from humid tropical rain forests until a very dry savannah type at the eastern part of Nusa Tenggara. Furthermore, Indonesia is also known as the fourth world highest producer of coffee; with a total production 11,49 million kg in 2016-2017. The Gayo highlands on the northern tip of Sumatra are known as the major production of arabica coffee. There, up to ten varieties of commercial arabica coffee are planted on the highlands. The origin of coffee is in Ethiopia, which is believed as the center of the commercial coffee species in this world: C. arabica and C. canephora. The objective of this paper is to review the status of coffee, esp. the arabica one from various perspectives, ranging from the biology, history of coffee, the processing of coffee (wet vs. dry methods), and how the component of natural biodiversity can be applied in order to enhance the coffee production, particularly on the Gayo highlands.
7

Galy-Lacaux, C., D. Laouali, L. Descroix, N. Gobron, and C. Liousse. "Long term precipitation chemistry and wet deposition in a remote dry savanna site in Africa (Niger)." Atmospheric Chemistry and Physics 9, no. 5 (March 3, 2009): 1579–95. http://dx.doi.org/10.5194/acp-9-1579-2009.

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Abstract. Long-term precipitation chemistry have been recorded in the rural area of Banizoumbou (Niger), representative of a semi-arid savanna ecosystem. A total of 305 rainfall samples ~90% of the total annual rainfall) were collected from June 1994 to September 2005. From ionic chromatography, pH major inorganic and organic ions were detected. Rainwater chemistry is controlled by soil/dust emissions associated with terrigeneous elements represented by SO42−, Ca2+, Carbonates, K+ and Mg2+. It is found that calcium and carbonates represent ~40% of the total ionic charge. The second highest contribution is nitrogenous, with annual Volume Weighed Mean (VWM) for NO3− and NH4+ concentrations of 11.6 and 18.1 μeq.l−1, respectively. This is the signature of ammonia sources from animals and NOx emissions from savannas soil-particles rain-induced. The mean annual NH3 and NO2 air concentration are of 6 ppbv and 2.6 ppbv, respectively. The annual VWM precipitation concentration of sodium and chloride are both of 8.7 μeq.l−1 which reflects the marine signature of monsoonal and humid air masses. The median pH value is of 6.05. Acidity is neutralized by mineral dust, mainly carbonates, and/or dissolved gases such NH3. High level of organic acidity with 8μeq.l−1 and 5.2 μeq.l−1 of formate and acetate were also found. The analysis of monthly Black Carbon emissions and Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) values show that both biogenic emission from vegetation and biomass burning could explain the rainfall organic acidity content. The interannual variability of the VWM concentrations around the mean (1994–2005) is between ±5% and ±30% and mainly due to variations of sources strength and rainfall spatio-temporal distribution. From 1994 to 2005, the total mean wet deposition flux in the Sahelian region is of 60.1 mmol.m−2.yr−1 ±25%. Finally, Banizoumbou measurements are compared to other long-term measurements of precipitation chemistry in the wet savanna of Lamto (Côte d'Ivoire) and in the forested zone of Zoétélé (Cameroon). The total chemical loading presents a maximum in the dry savanna and a minimum in the forest (from 143.7, 100.2 to 86.6 μeq.l−1), associated with the gradient of terrigeneous sources. The wet deposition fluxes present an opposite trend, with 60.0 mmol.m−2.yr−1 in Banizoumbou, 108.6 mmol.m−2.yr−1 in Lamto and 162.9 mmol.m−2.yr−1 in Zoétélé, controlled by rainfall gradient along the ecosystems transect.
8

Davidson, Eric A., Mercedes M. C. Bustamante, and Alexandre de Siqueira Pinto. "Emissions of Nitrous Oxide and Nitric Oxide from Soils of Native and Exotic Ecosystems of the Amazon and Cerrado Regions of Brazil." Scientific World JOURNAL 1 (2001): 312–19. http://dx.doi.org/10.1100/tsw.2001.261.

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This paper reviews reports of nitrous oxide (N2O) and nitric oxide (NO) emissions from soils of the Amazon and Cerrado regions of Brazil. N2O is a stable greenhouse gas in the troposphere and participates in ozone-destroying reactions in the stratosphere, whereas NO participates in tropospheric photochemical reactions that produce ozone. Tropical forests and savannas are important sources of atmospheric N2O and NO, but rapid land use change could be affecting these soil emissions of N oxide gases. The five published estimates for annual emissions of N2O from soils of mature Amazonian forests are remarkably consistent, ranging from 1.4 to 2.4 kg N ha–1 year–1, with a mean of 2.0 kg N ha–1 year–1. Estimates of annual emissions of NO from Amazonian forests are also remarkably similar, ranging from 1.4 to 1.7 kg N ha–1 year–1, with a mean of 1.5 kg N ha–1 year–1. Although a doubling or tripling of N2O has been observed in some young (<2 years) cattle pastures relative to mature forests, most Amazonian pastures have lower emissions than the forests that they replace, indicating that forest-topasture conversion has, on balance, probably reduced regional emissions slightly (<10%). Secondary forests also have lower soil emissions than mature forests. The same patterns apply for NO emissions in Amazonia. At the only site in Cerrado where vegetation measurements have been made N2O emissions were below detection limits and NO emissions were modest (~0.4 kg N ha–1 year–1). Emissions of NO doubled after fire and increased by a factor of ten after wetting dry soil, but these pulses lasted only a few hours to days. As in Amazonian pastures, NO emissions appear to decline with pasture age. Detectable emissions of N2O have been measured in soybean and corn fields in the Cerrado region, but they are modest relative to fluxes measured in more humid tropical agricultural regions. No measurements of NO from agricultural soils in the Cerrado region have been made, but we speculate that they could be more important than N2O emissions in this relatively dry climate. While a consistent pattern is emerging from these studies in the Amazon region, far too few data exist for the Cerrado region to assess the impact of land use changes on N oxide emissions.
9

Galy-Lacaux, C., D. Laouali, L. Descroix, N. Gobron, and C. Liousse. "Long term precipitation chemistry and wet deposition in a remote dry savanna site in Africa (Niger)." Atmospheric Chemistry and Physics Discussions 8, no. 2 (March 19, 2008): 5761–812. http://dx.doi.org/10.5194/acpd-8-5761-2008.

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Abstract. A long-term measurement of precipitation chemistry has been carried-out in a rural area of Banizoumbou, in the Sahel (Niger), representative of the african semi-arid savanna ecosystem. A total of 305 rainfall samples, representing 90% of the total annual rainfall, were collected with an automatic wet-only rain sampler from June 1994 to September 2005. Using ionic chromatography, pH major inorganic and organic ions were analyzed. Rainwater chemistry at the site is controlled by soil dust emissions associated to a strong terrigeneous contribution represented by SO42–, Ca2+, Carbonates, K+ and Mg2+. Calcium and carbonates represent about 40% of the total ionic charge of precipitation. The second highest contribution is nitrogenous, with annual Volume Weighed Mean (VWM) NO3– and NH4+, concentrations of 11.6 and 18.1 μeq.l−1, respectively. This is thesignature of ammonia sources related to animals and NOx emissions from savannas soils rain-induced, at the beginning of the rainy season. The mean annual NH3 and NO2 air concentration are of 6 ppbv and 2.6 ppbv, respectively. The annual VWM precipitation concentration of sodium and chloride are both of 8.7 μeq.l−1 and reflects the marine signature from the monsoon humid air masses coming from the ocean. The mean pH value, calculated from the VWM of H+, is 5.64. Acidity is neutralized by mineral dust, mainly carbonates, and/or dissolved gases such NH3. High level of organic acidity with 8 μeq.l−1 and 5.2 μeq.l−1 of formate and acetate were found, respectively. The analysis of monthly Black Carbon emissions and FAPAR values show that both biogenic emission from vegetation and biomass burning sources could explain the organic acidity content of the precipitation. The interannual variability of the VWM concentrations around the mean (1994–2005) presents fluctuations between ±5% and ±30% mainly attributed to the variations of sources strength associated with rainfall spatio-temporal distribution. From 1994 to 2005, the total mean wet deposition flux in the Sahelian region is 60.1 mmol.m−2.yr−1 and fluctuates around ±25%. Finally, Banizoumbou measurements, are compared to other long-term measurements of precipitation chemistry in the wet savanna of Lamto (Côte d'Ivoire) and in the forested zone of Zoétélé (Cameroon). The total chemical loadings presents a strong negative gradient from the dry savanna to the forest (143.7, 100.2 to 86.6 μeq.l–1), associated with the gradient of terrigeneous compounds sources. The wet deposition fluxes present an opposite gradient, with 60.0 mmol.m−2.yr−1 in Banizoumbou, 108.6 mmol.m−2.yr–1 in Lamto and 162.9 mmol.m−2.yr−1 in Zoétélé, controlled by the rainfall gradient along the ecosystems transect.
10

Saraiva, Sarah O., Ian D. Rutherfurd, Philip R. Kaufmann, Cecília G. Leal, Diego R. Macedo, and Paulo S. Pompeu. "Wood stock in neotropical streams: Quantifying and comparing instream wood among biomes and regions." PLOS ONE 17, no. 10 (October 5, 2022): e0275464. http://dx.doi.org/10.1371/journal.pone.0275464.

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Instream wood plays important chemical, physical and ecological functions in aquatic systems, benefiting biota directly and indirectly. However, human activities along river corridors have disrupted wood recruitment and retention, usually leading to reductions in the amount of instream wood. In the tropics, where wood is believed to be more transient, the expansion of agriculture and infrastructure might be reducing instream wood stock even more than in the better studied temperate streams. However, research is needed to augment the small amount of information about wood in different biomes and ecosystems of neotropical streams. Here we present the first extensive assessment of instream wood loads and size distributions in streams of the wet-tropical Amazon and semi-humid-tropical Cerrado (the Brazilian savanna). We also compare neotropical wood stocks with those in temperate streams, first comparing against data from the literature, and then from a comparable dataset from temperate biomes in the USA. Contrary to our expectations, Amazon and Cerrado streams carried similar wood loads, which were lower than the world literature average, but similar to those found in comparable temperate forest and savanna streams in the USA. Our results indicate that the field survey methods and the wood metric adopted are highly important when comparing different datasets. But when properly compared, we found that most of the wood in temperate streams is made-up of a small number of large pieces, whereas wood in neotropical streams is made up of a larger number of small pieces that produce similar total volumes. The character of wood volumes among biomes is linked more to the delivery, transport and decomposition mechanisms than to the total number of pieces. Future studies should further investigate the potential instream wood drivers in neotropical catchments in order to better understand the differences and similarities here detected between biomes and climatic regions.

Дисертації з теми "Forest and humid savannah ecosystems":

1

Ouafo, Mendo-Leumbe Marie-Roumy. "Etude de la composition physico-chimique, des sources émettrices et des effets sur la santé humaine des aérosols atmosphériques en zones rurales et urbaines en Afrique tropicale." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30402.

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Ce travail de thèse s'inscrit dans le cadre du programme INDAAF (International Network to study Deposition and Atmospheric chemistry in AFrica). Il a pour objectif d'étudier la physico-chimie des aérosols atmosphériques prélevés sur deux sites ruraux africains peu perturbés et représentatifs des écosystèmes de forêt (site de Nsimi au Cameroun) et de savane humide (site de Djougou au Bénin). Les aérosols prélevés hebdomadairement dans les fractions PM2,5 et PM10 à Nsimi de 2004 à 2009 et à Djougou de 2005 à 2009 ont été analysées, afin de caractériser les variations saisonnières des concentrations des différentes espèces chimiques et d'identifier leurs sources majeures en fonction des saisons. Les résultats obtenus ont permis (1) de mettre en évidence l'impact des paramètres climatiques sur les niveaux de concentration des espèces chimiques, la saison sèche présentant en général les plus importants, (2) d'identifier les sources combustion de biomasse et de biocombustible, terrigène, biogénique et secondaire comme présentes en saison sèche et les sources biogénique, feux domestiques et phénomène de guttation en saison humide, (3) de montrer l'impact de l'écosystème et de la situation géographique sur les émissions des aérosols : la source biogénique et la guttation sont plus importantes en forêt tandis que la source terrigène est plus importante en savane humide. Le second volet de cette thèse s'inscrit dans le cadre du programme POLCA (POLlution des Capitales Africaines). Le but était de caractériser la pollution particulaire à Yaoundé, capitale du Cameroun, et d'étudier son impact toxicologique sur la santé. Ce travail a permis de caractériser à l'échelle saisonnière la chimie de l'aérosol prélevé mensuellement de décembre 2012 à juillet 2013 et d'en déterminer les sources. Ensuite, divers tests de réponses biologiques des cellules épithéliales humaines exposées à ces aérosols ont permis de déterminer leur toxicité dans l'organisme humain en fonction des espèces chimiques les composant. Les résultats obtenus ont montré (1) l'impact de la taille et du nombre des particules de Yaoundé sur la toxicité : les plus fines induisant une plus forte expression de la réponse pro-inflammatoire des cytokines et des enzymes anti-oxydantes, (2) l'impact de la composition chimique sur cette toxicité : les aérosols riches en matières organiques particulaires induisant fortement l'expression des gènes du métabolisme des xénobiotiques, en particulier le CYP1A1
This thesis was a contribution to the INDAAF (International Deposition Network to study and Atmospheric chemistry in Africa) program. It aims was to study the physics and chemistry of atmospheric aerosol collected on two undisturbed African rural sites, representative of forest (Nsimi site Cameroon) and humid savanna (Djougou site Benin) ecosystems. Aerosols collected weekly in the PM2.5 and PM10 fractions at Nsimi, from 2004 to 2009 and at Djougou, from 2005 to 2009 were analyzed in order to characterize the seasonal variations of concentrations of the different chemical species and to identify their major sources according to the seasons. The contribution of each group of species was estimated from the total concentration of the aerosol. The results obtained allowed (1) to highlight the impact of climatic parameters on the concentration levels of the chemical species, with the dry season having the most important impact in general, (2) to identify biomass combustion sources and biofuel, terrigenous, biogenic, secondary as well as predominant in the dry season and biogenic sources, domestic fires and guttation phenomenon in the wet season, (3) to show the impact of the ecosystem and the location on emissions of aerosols: biogenic source and guttation are higher in the forest while terrigenous source is higher in wet savanna. The second part of my thesis is a part of the program POLCA (POLlution African Capitals). The main objective was to characterize particulate pollution in Yaounde, capital of Cameroon, and to study its toxicological impact on the human respiratory system. This work allowed to chemically characterize on a seasonal basis aerosols collected monthly from December 2012 to July 2013 and identify the sources. Furthermore, various tests on biological responses of human epithelial cells exposed to Yaounde aerosols were used to determine their toxicity in humans based on the component chemical species. The results showed (1) the impact of the size and number of Yaounde's particles on toxicity: the finer inducing a stronger expression of the pro-inflammatory cytokine response and anti-oxidant enzymes, (2) the impact of the chemical composition on this toxicity: aerosols with important quantities of particulate organic matter strongly induce gene expression of the metabolism of xenobiotics, especially CYP1A1
2

Gosling, William D. "Characterization of neotropical forest and savannah ecosystems by their modern pollen spectra." Thesis, University of Leicester, 2004. http://hdl.handle.net/2381/30404.

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Controversy surrounds the Quaternary palaeoenvironmental history of Amazonia. It is unclear whether moist evergreen forest, savannah or seasonally dry forest dominated the Amazon basin at the last glacial maximum (c. 21,000 years before present). The main source of information on past vegetation change in Neotropics are fossil pollen records collected from within ancient sediments. In part the controversy surrounding the palaeoenvironmental history of Amazonia stems from a poor understanding of these fossil pollen records. In order to improve interpretations of the fossil pollen record it is essential to better understand the nature of the pollen rain produced by modern ecosystems. Once the characterise pollen spectrum from an ecosystem has been established, it can be sought in the fossil pollen record. However, few such modern pollen-vegetation studies exist from the Neotropics and no one covers all the ecosystems that have controversial palaeoenvironmental histories. In this thesis, the modern pollen rain from the three Neotropical ecosystems with controversial palaeoenvironmental histories are characterised. This is achieved by studying modern pollen rain from the Noel Kempff Mercado National Park area, Bolivia. to identify the characteristic pollen from these ecosystems four factors are considered: i) the spatial variation in the pollen rain, ii) the temporal variations in the pollen rain, iii) the statistically significant pollen types, and iv) the pollen-vegetation relationship. These analyses have revealed a small number of taxa that can be used to characterize these ecosystems. Further analyses have shown that the relative proportions of Didymopanax, Alchornea, Anadenanthera, Melastomataceae/Combretaceae, Moraceae/Urticaceae, Myrtaceae, Palmae, Pteropsidia (trilete), Poaceae and Solanum can be used to differentiate between these ecosystems. These findings have implications for the competing theories of Neotropical vegetation change. In the light of this research a comprehensive reassessment of the fossil pollen records from Amazonia is required.
3

Moreira, Carolina Mathias. "Avaliação de métodos fitossociológicos através de simulações de amostragens numa parcela permanente de cerradão, na Estação Ecológica de Assis, SP." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/11/11150/tde-05062007-134450/.

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Existem vários métodos empregados em estudos fitossociológicos e muitos trabalhos já se propuseram a avaliar o desempenho desses métodos. O primeiro e mais utilizado é o método de parcelas, que sempre é referido nos trabalhos como o melhor e por isso definido como base para comparação com os demais. Por esse motivo, nunca foi avaliado isoladamente. Com o presente trabalho tem-se a oportunidade de avaliar o próprio método de parcelas, comparando seus resultados com os valores paramétricos, uma vez que foi feito um censo da área amostrada e a população estatística é conhecida sem erro amostral. Os dados são de uma parcela permanente instalada em uma área de cerradão (Estação Ecológica de Assis, SP). A parcela possui 10,24 ha e todos seus indivíduos com CAP ≥ 15 cm foram marcados, georreferenciados, medidos e identificados. Foi feita uma tabela de fitossociologia para a parcela que, por se tratar de um censo, representa os valores paramétricos. Foram geradas simulações de levantamentos fitossociológicos por amostragens sistemáticas para quatro tamanhos de parcela quadrada, sendo 10 x 10 m, 20 x 20 m, 50 x 50 m e 100 x 100 m, todas com área total amostrada de 1 ha. Para a parcela de 10 x 10 m foram simuladas mais três intensidades amostrais: 75, 50 e 25 parcelas. Para cada situação de amostragem foram simuladas 1.000 amostras e para cada uma dessas amostras foi elaborada uma tabela de fitossociologia. Foi avaliado o viés das etimativas de densidade e dominância, e a alteração da posição das espécies na tabela de fitossociologia. Foi avaliada também a influência da distribuição espacial das espécies nas etimativas. Por fim, foram feitas algumas análises de atributos de comunidade que são viáveis à partir de levantamentos fitossociológicos, como densidade, área basal, curva de acumulação de espécies, número de espécies amostradas e proporção de espécies e indivíduos por classe de densidade. O método de parcelas de 10 x 10 m foi o que apresentou menor viés para as estimativas, e também menor variação na posição das espécies na tabela de fitossociologia, mas mesmo assim há um alto viés para espécies de baixa densidade e uma grande alteração na posição das espécies na tabela de fitossociologia. Com relação à distribuição espacial, espécies com densidades intermediárias têm suas estimativas mais influenciadas pela distribuição espacial do que aquelas com baixa densidade - que sempre apresentarão viés - e aquelas com alta densidade - que não apresentam viés devido ao alto número de invivíduos na amostra. As análises de tributos de comunidade mostraram que esses atributos podem ser bem estimados, levando-se em consideração apenas detalhes usuais da escolha de método para qualquer amostragem, como o número de unidades amostrais, seu tamanho e sua distribuição pela área de estudo.
Many methodologies are available for phytosociological studies, and many attempts have been made to evaluate them. The most commonly used method employs sample plots. This technique is always referred to in the literature as the basic approach and, as such, is usually defined as the benchmark to which the other methods are compared. For this reason, it has never been evaluated on its own. This work presents the opportunity to evaluate the plot method itself and compare its results with the parametric values available from a full census of a sampling area in which the complete population data is known and contains no sampling error. Data was taken from a permanent plot located in an area of forested savannah (Assis Ecological Station, SP, Brazil), that comprises an area of 10.24 ha, and all trees over 15 cm girth at breat hight were marked, georeferenced, measured and identified. Phytosociological measures were computed with the values of density and basal area for each species in the census and represent the parametric values. Simulations were made of phytosociological surveys by sistematic sampling with four square plot sizes (10 x 10 m, 20 x 20 m, 50 x 50 m, and 100 x 100 m). Additionally, three sampling intensities were simulated for the 10x10m plots (75, 50, and 25 plots). One thousand simulated surveys were performed for each sampling situation, and for each of these surveys phytosociological measures were computed. The bias in the estimates of both density and dominance was evaluated, as well as change in species importance. The influence of spatial pattern on the estimation of phytosociological measures was also evaluated. At last, some analysis of community attributes, that are feasible with phytosociological measures were made, such as density, basal area, species acummulation curves, number of species sampled and propotion of species and individuals per density group. The 10 x 10 m sample plots showed the lowest overall bias and the lowest variation in species importance, but even in this method were observed high bias and high variation. About the spatial distribution, species with very low density showed very large bias, indenpendently of spatial pattern. Spatial pattern had a clear influence on the estimates of intermediate density species, where species with more clustered pattern showed more skewed distribution. And for the species with high density, spatial pattern does not seem to play an importante role. The community attributes analysed can be well estimated with phytosociolocical measures, just taking into consideration some usual methodological details, such as sampling size and plot distributions within the study area.

Частини книг з теми "Forest and humid savannah ecosystems":

1

Godt, Miguel Clüsener, and Malcolm Hadley. "Ecosystem rehabilitation and forest regeneration in the humid tropics: Case studies and management insights." In Restoration of Tropical Forest Ecosystems, 25–36. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-017-2896-6_2.

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2

Kauffman, Sjef, Wim Sombroek, and Stephan Mantel. "Soils of rainforests Characterization and major constraints of dominant forest soils in the humid tropics." In Soils of Tropical Forest Ecosystems, 9–20. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-662-03649-5_1.

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3

Fadairo, Olushola, Samuel Olajuyigbe, Tolulope Osayomi, Olufolake Adelakun, Olanrewaju Olaniyan, Siji Olutegbe, and Oluwaseun Adeleke. "Climate Change, Rural Livelihoods, and Ecosystem Nexus: Forest Communities in Agroecological zones of Nigeria." In African Handbook of Climate Change Adaptation, 1169–92. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-45106-6_155.

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AbstractA top-bottom approach where local problems are treated in isolation has proven ineffective in achieving sustainable development. The need for inclusive approaches to managing the demand for arable lands, forest resources, and the problems of resource exploitation and climate change calls for local understanding of these elements’ interrelationship. Understanding the interrelationships among climate change, agriculture, and the ecosystems in different agroecological zones in Nigeria was the purpose of this chapter. Deforestation and forest degradation analysis approach was utilized. One state and two forest communities from each of the rainforest, savannah, and mangrove agroecological zones were purposively focused in this chapter based on forest distribution and cover. Focus group discussions involving 252 male and female farmers using 30 years as reference were used to garner relevant information. Climate variation caused a slight modification in cropping schedules of farmers due to prolonged dry season, mainly in the savannah region. Farmers engaged in mixed farming and also cultivate more hardy crops like cassava in response to climate uncertainties. Especially in the mangrove and savannah, ecosystem components such as agriculture and population showed increasing trends over the years as forest cover reduces. Downward trend in charcoal production was limited to mangrove and rainforest zones as fishing and hunting becomes vulnerable livelihoods across the zones. The degree and progression of climate change effects on the ecosystem in Nigeria agroecological zones is largely comparable and have both desirable and adverse livelihood outcomes. Affordable insurance policy, credit, agri-inputs, favorable forest regulatory framework, and youth empowerment supports would enhance sustainable adjustment to climate change.
4

Ohsawa, M. "Latitudinal comparison of altitudinal changes in forest structure, leaf-type, and species richness in humid monsoon Asia." In Global change and terrestrial ecosystems in monsoon Asia, 3–10. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0343-5_1.

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5

Aabeyir, Raymond, Kenneth Peprah, and Gervase Kuuwaabong. "Nexus Between Savannah Woodland Degradation and Climate Change in Northern Ghana." In Environmental Sciences. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.107265.

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The Savannah woodland and forest ecosystems are considered as fragile ecosystems in Ghana. They are located in pro-poor areas of the country. They serve as livelihood support systems for the poor in those areas. In the midst of climate change, the same woods are expected to provide mitigation support against climate change. These woodland and forest ecosystems are in a state of dilemma: providing adaptation support to humans and at the same time providing mitigation support against climate change in the midst of climatic and seasonal challenges: low rainfall, excessive heat, harmattan and annual bushfires. The sustainability of these ecosystems depends on the net effect resulting from the pressures of adaptation, efforts of mitigation, resilience of the ecosystems and other natural support systems. This chapter explores the relationship among woodland, adaptation and mitigation activities. In this relationship, the human face has played a central role, thus influencing the direction of the net effects of the pressures on woodland ecosystems. Adaptation is over-emphasised, misunderstood and decoupled from mitigation resulting in maladaptation. This has contributed to the worsening impacts of climate change. Climate change adaptation needs to be re-emphasised to ensure mitigation is considered in every adaptation measure.
6

Paruelo, José María, and Estebán G. Jobbágy. "The Grasslands and Steppes of Patagonia and the Río de la Plata Plains." In The Physical Geography of South America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195313413.003.0022.

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The Patagonian steppes and the Río de la Plata grasslands occupy a vast proportion of the plains, plateaus, and hills of southern South America, and are characterized by the almost absolute absence of trees. Prairies and steppes (grass and low shrubs) are the dominant physiognomic types, and forests are restricted to some riparian corridors. Savannas become important only in the ecotones of these regions, whereas meadows may be locally important under particular topographic or edaphic conditions. The Río de la Plata grasslands (RPG), one of the most important grassland regions in the world, extend between 28°S and 38°S latitude, covering about 700,000 km2 of eastern Argentina, Uruguay, and southern Brazil. The boundaries of these grasslands include the Atlantic coastline to the east, dry temperate forests to the south and west, and subtropical humid forests to the north. Woody vegetation within the region is restricted to small areas near water bodies, such as the gallery forests along the large Paraná and Uruguay rivers and their tributary streams. The Patagonian steppes occupy the southern tip of the continent from approximately 40°S, and are framed by the Andes to the west and the Atlantic coast to the east and south and cover more than 800,000 km2 of Chile and Argentina. Toward the west, the region displays a sharp ecotone with the subantarctic forests, whereas to the north it grades into a broad zone of Monte scrublands in central Argentina. The RPG and the Patagonian steppes are separated by a wide strip of woody vegetation, the Monte and Espinal phytogeographic units (see chapter 10; Cabrera and Willkins, 1973). In this chapter, we describe the heterogeneity and main characteristics of the dominant ecosystems of the Patagonian steppes and the RPG, focusing on environmental controls and human-induced changes. Although numerous criteria have been applied to describe the internal heterogeneity of both regions, we emphasize here the structural and functional attributes of vegetation as integrators of climate, physiography, and land use.
7

"Soil Resources and Human Adaptation in Forest and Agricultural Ecosystems in Humid Asia." In World Soil Resources and Food Security, 67–182. CRC Press, 2016. http://dx.doi.org/10.1201/b11238-8.

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8

Badmaev, Nimazhap Bayarzhapovich, Aleksandr Vladimirovich Bazarov, and Roman Sergeevich Sychev. "Forest Fire Danger Assessment Using Meteorological Trends." In Predicting, Monitoring, and Assessing Forest Fire Dangers and Risks, 183–208. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-1867-0.ch008.

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The chapter presents the results of research in the Republic of Buryatia, where the number and area of fires have increased over the past 20 years due to the rise in temperature and aridity. Most of the fires are registered in the large river valleys where pine forests are formed, which have low soil moisture capacity. Fewer fires occurred on the Eastern Sayans, Khamar-Daban ridges, and the Stanovoye Highlands, where the precipitation maximum falls. A correlation analysis was carried out between meteorological parameters and fires in climate-contrasting forests. The lack of precipitation at the end of the previous summer, combined with the hot and dry spring weather of the current year, have a significant impact on fires in the arid ecosystems of the Transbaikal middle mountains. In the humid coastal climate of the Eastern Baikal region, the high temperature of the air determines the fires, but there is no precipitation.
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Badmaev, Nimazhap Bayarzhapovich, Aleksandr Vladimirovich Bazarov, and Roman Sergeevich Sychev. "Forest Fire Danger Assessment Using Meteorological Trends." In Research Anthology on Ecosystem Conservation and Preserving Biodiversity, 1026–51. IGI Global, 2022. http://dx.doi.org/10.4018/978-1-6684-5678-1.ch051.

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The chapter presents the results of research in the Republic of Buryatia, where the number and area of fires have increased over the past 20 years due to the rise in temperature and aridity. Most of the fires are registered in the large river valleys where pine forests are formed, which have low soil moisture capacity. Fewer fires occurred on the Eastern Sayans, Khamar-Daban ridges, and the Stanovoye Highlands, where the precipitation maximum falls. A correlation analysis was carried out between meteorological parameters and fires in climate-contrasting forests. The lack of precipitation at the end of the previous summer, combined with the hot and dry spring weather of the current year, have a significant impact on fires in the arid ecosystems of the Transbaikal middle mountains. In the humid coastal climate of the Eastern Baikal region, the high temperature of the air determines the fires, but there is no precipitation.
10

Fairhead, James. "Archaeology and Environmental Anthropology: Collaborations in Historical and Political Ecology." In Humans and the Environment. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199590292.003.0027.

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This chapter examines the importance of integrating archaeological perspectives within contemporary environmental anthropology. It does this through exposing key questions raised by environmental anthropologists concerning West African relations with soil and forests that can only be addressed through collaboration with archaeological investigation (see also Balée, Chapter 3 this volume). Environmental anthropological research has been particularly important in revealing the ecological knowledge and environmental practices of land users and how these practices interplay with ecological and economic processes in the shaping of landscapes. This research has systematically undermined a paradigm of environmental reasoning that equates land use with the progressive degradation of otherwise ‘natural’, ‘equilibrial’, or ‘pristine’ environments (whether of soils, forests, or faunal assemblages). Whilst equilibrial ecology is apparently no longer upheld in ecological sciences either, in its shift to non-equilibrium ecology and recognition of path dependency, and whilst nature is no longer so easily configured simply as the absence of people, assumptions rooted in such simplistic ideas of nature still strongly inform and mislead the way West African environments are understood and problematized. Anthropologically derived critiques of the way landscapes are understood have been associated with a rereading of the history of those landscapes. Yet given how oral historical and anthropologically derived historical evidence can so easily be delegitimized and dismissed by apparently ‘harder’ sciences, environmental archaeology becomes a crucial player in these debates. In this brief chapter I shall focus on two key debates which can only be resolved (or reconceptualized) through environmental archaeology. The first of these concerns the degradation (or otherwise) of soils and vegetation linked to farming in West Africa’s Guinea savannah and forest-savannah transition zones. The second concerns the legacy of past land use on current ‘old growth’ forest in the Central and West African humid forest zones. These are not only interesting debates, but are at the heart of sustainable development policy deliberation in West Africa. The continued power of the paradigm in environmental reasoning that equates land use with the progressive degradation of otherwise ‘natural’ or ‘pristine’ environments is visible in the way that landscape features are often interpreted uncritically as ‘relicts’ of that nature.

Тези доповідей конференцій з теми "Forest and humid savannah ecosystems":

1

Wellens, Jane, Andrew K. Millington, France Gerard, and Barry K. Wyatt. "Potential of ATSR-2 satellite imagery for identifying and mapping different humid tropical forest ecosystems." In Satellite Remote Sensing, edited by Eric Mougin, K. Jon Ranson, and James A. Smith. SPIE, 1995. http://dx.doi.org/10.1117/12.200759.

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Звіти організацій з теми "Forest and humid savannah ecosystems":

1

Degrande, A., K. Schreckenberg, C. Mbosso, and C. Mfoumou. Farmer livelihoods in the humid forest and moist savannah zones of Cameroon ICRAF Working Paper no. 47. World Agroforestry Centre (ICRAF), 2007. http://dx.doi.org/10.5716/wp15222.pdf.

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