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Tengbeh, G. Tamba. "The effect of grass cover on bank erosion." Thesis, Cranfield University, 1989. http://dspace.lib.cranfield.ac.uk/handle/1826/3620.
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The scour experiments on the bare root-free and root-permeated soils indicated that for each soil, critical tractive force (CTF) linearly increases with both root density and vane shear strength. However, for both soilsq CTF was mainly related to vaneýshear strengthp indicating the potential importance of soil shear strength as an index of scour erodibility of cohesive channel bank materials. The analysis of the relative effects of the grass vegetation parameters on scour resistance confirmed the dominance of vegetation shoots relative to the roots in resisting scour in-non-bending vege- tation. The results showed that it is the initial introduction of vegetation into bare (root-free) bank conditions that produces the greatest increase in scour resistance and that subsequent increases in vegetation density bring about relatively lower increases in scour resistance. However, in all the vegetation densities studied, root- permeated so-ils contributed significantly to scour resistance in low flows especially through low vegetation densities. Compared to root- free soil conditions, sandy clay loam soils permeated with 1.8 g/CM3 of roots increased their scour resistance by more than 400%. Althgouh these results may only be indicative of the low flow depths as would exist in shallow grassed channels commonly used for agricultural run- off drainage, they nevertheless highlight the importance of root density in contributing to the total flow resistance of grassed channel banks. The bank stability analysis indicated that for low channel banks (1.5m high), grass roots can stabilise banks with even vertical slopes against toe and slope vailures. For high (2.25m) and vertical bank conditions, the results indi- cate that the effects of increases in root density may need to be com- plemented by bank shaping in order to achieve stability. The scour and bank stability findings indicate that the three most important charac- teristics for the selection of grass vegetation for bank protection are quick establishmentg the development of a stiff shoot system and a strong root mat.
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Short, Nicolyn. "Implications of green manure amendments on soil seed bank dynamics." University of Western Australia. School of Earth and Geographical Sciences, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0022.
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[Truncated abstract] Weeds are a major limitation to agricultural and horticultural production and the main method of control is the use of herbicides. In addition to the resulting chemical pollution of the environment, the wide spread and continues use of herbicides have resulted in many weeds developing resistance to commonly used herbicides. This study investigated the potential of using green manures as a cultural method of control of weed invasion in agricultural fields. To understand the general mechanisms involved in the suppression of seed germination in green manure amended soils, seeds of crop species with little or no dormancy requirements were used in certain studies. Lettuce (Lactuca sativa) and cress (Lepidium sativum) seeds were sown to a sandy soil amended with green manures of lupin (Lupinus angustifolius), Brassica juncea, or oats (Avena sativa) to determine if the amendments affected seed germination and/or decay. It was hypothesised that the addition of plant material would increase the microbial activity of the soil thereby increasing seed decay, under laboratory and greenhouse conditions. Initial experiments used lettuce, cress and lupin seeds. Lettuce and cress are commonly used as standard test species for seed viability studies. Subsequent experiments used seeds of annual ryegrass (Lolium rigidum), silver grass (Vulpia bromoides), wild radish (Raphanus raphanistrum) and wild oat (Avena fatua) as these weed species are commonly found throughout agricultural regions in Western Australia. Amending the soil with lupin or Brassica green manure was established as treatments capable of developing environments suppressive to seed germination. Lupin residues as green manure showed the strongest inhibition of seed germination and seed decay. The decay of certain seeds was enhanced with changes to soil microbial activity, dissolved organic carbon and carbon and nitrogen amounts in lupin amended soil. Seeds of weed species were decayed in lupin amended soil, but showed varied degree of decay. Annual ryegrass and silver grass were severely decayed and wild oat and wild radish were less decayed, in lupin amended soil.
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Couper, Pauline R. "River bank erosion and the influence of soil particle size." Thesis, Coventry University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327661.
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Schelling, Lisa R. "Soil seed banks in mixed oak forests in Southeastern Ohio." Ohio : Ohio University, 2006. http://www.ohiolink.edu/etd/view.cgi?ohiou1141850222.
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Leiva, Soto Andrea S. "Effects of Soil Balancing Treatments on Soils, Vegetable Crops and Weeds in Organically Managed Farms." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu151514193894181.
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Maighel, Mahmood [Verfasser]. "Effect of Arbuscular mycorrhizal fungi and biochar on soil seed bank viability / Mahmood Maighel." Berlin : Freie Universität Berlin, 2016. http://d-nb.info/1117028453/34.
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Tufekcioglu, Mustafa. "Riparian land-use impacts on stream bank soil and phosphorus losses from grazed pastures." [Ames, Iowa : Iowa State University], 2006.
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Pessoa, Carla Daniela de Sales. "Soil Seed Bank in a Caatinga area in Regeneration, Center for Desertification IrauÃuba, CearÃ." Universidade Federal do CearÃ, 2008. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=9200.
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CoordenaÃÃo de AperfeiÃoamento de NÃvel SuperiorO presente trabalho tem como objetivo conhecer os atributos do banco de sementes no solo e verificar quais desses refletem melhor a regeneraÃÃo da caatinga em Ãreas de desertificaÃÃo. Para tanto, investigou-se o banco de sementes no final da estaÃÃo seca, em uma Ãrea de caatinga em processo de degradaÃÃo/desertificaÃÃo, no municÃpio de IrauÃuba, CearÃ. Foram analisados os atributos densidade, composiÃÃo, diversidade e riqueza de espÃcies e cinÃtica de germinaÃÃo. As coletas foram realizadas em trÃs Ãreas, nas fazendas Formigueiro, Cacimba Salgada I e Cacimba Salgada II. Em cada Ãrea foi amostrado o banco de sementes no solo na parcela experimental (pousio) e na parcela em uso contÃnuo (controle). Cada parcela de cada Ãrea foi subdividida em dezesseis parcelas de 10x10m, das quais foram sorteadas cinco para estudo do banco de sementes no solo. No centro de cada uma das cinco parcelas de 100m2 foi retirada amostra de solo de 0,25m2 de Ãrea. A densidade e a composiÃÃo do banco de sementes no solo foram analisadas atravÃs da tÃcnica de emergÃncia de plÃntulas em casa de vegetaÃÃo. O banco foi composto prioritariamente por terÃfitos. As densidades encontradas foram 592, 1804, 2080 sem/m2 para as parcelas experimentais 1, 2 e 3, respectivamente e 680, 1288 e 1408 sem/m2, para as parcelas controle 1, 2 e 3, respectivamente. No parÃmetro riqueza, foram encontrados iguais valores para as parcelas experimento e controle (8 e 2 para as Ãreas 1 e 2, respectivamente), a Ãrea 3 apresentou maior riqueza na parcela em pousio (15 e 10 para as parcelas controle e experimento, respectivamente). Os valores de equabilidade nas parcelas experimento foram de 0,751, 0,041 e 0,740 para as Ãreas 1, 2 e 3, respectivamente, e de 0,613, 0,054 e 0,603 para as Ãreas 1, 2 e 3 das parcelas controle. Em relaÃÃo à diversidade, os valores para as parcelas experimentais 1, 2 e 3 foram 1,562, 0,028, 2,004, respectivamente, e 1274, 0,038 e 1,388 para as parcelas controle, 1, 2 e 3, respectivamente, o que revela uma maior diversidade nas Ãreas em pousio, com exceÃÃo da Ãrea 2. Os aumentos da diversidade e da densidade demonstram a ocorrÃncia de regeneraÃÃo do componente herbÃceo nas Ãreas em pousio.
The objective of this study is to gather knowledge about the attributes of a seed bank at soil level and to verify which of these attributes reflect the best regeneration of the caatinga in areas of desertification. In order to do that, we investigated the seed bank at the end of the dry season in a area of caatinga suffering the process of degradation/desertification, at the municipality of IrauÃuba, CearÃ. We analysed the attributes of density, composition, diversity and richness of species as well as germination dynamics. The collections were realized in three areas, at Formigueiro, Cacimba Salgada I and Cacimba Salgada II farms. In each area, we sampled a seed bank at soil level in the experimental portion (fallow) and at the continuous use portion (control). Each portion of each area was divided in sixteen portions of 10 x 10 m, from which were drawn five portions for the study of the seed bank at soil level. In the center of each one of the five portions of 100 m2, a soil sample of 0,25 m2 was removed. The density and the composition of the seed bank at the soil level were analysed using the plantule outgrowth in greenhouse. The bank was composed primarily by therophytes. The densities found were 592, 1804, 2080 seeds/m2 for the experimental portions 1, 2 and 3, respectively, and 680, 1288 and 1408 seeds/m2 for the control portions 1, 2 and 3, respectively. Regarding the richness parameter, we found equal values for both the experimental and control portions (8 and 2 for areas 1 and 2, respectively); area 3 presented greater richness in the fallow portion (15 and 10 for the control and experimental portions, respectively). The equability values of the experimental portions were equal to 0,751, 0,041 and 0,740 for areas 1,2 and 3 respectively and of 0,613, 0,054 and 0,603 for areas 1,2 and 3 of the control portions. Regarding diversity, the values for the experimental portions 1, 2 and 3 were 1,562, 0,028 and 2,004, respectively, and 1274, 0,038 and 1,388 for the control portions 1,2 and 3, respectively, which reveals a major diversity for the areas of fallow, with exception of area 2. The raising diversity and density demonstrate the occurrence of regeneration of the herbaceous component in the fallow areas.
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Kellerman, Millicent Johanna Susanna. "Seed bank dynamics of selected vegetation types in Maputaland, South Africa." Diss., Connect to this title online, 2004. http://upetd.up.ac.za/thesis/available/etd-02012005-090837.
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Yehnjong, Petra Seka. "Paleozoic Seed Bank and Their Ecological Significance." Digital Commons @ East Tennessee State University, 2014. https://dc.etsu.edu/etd/2316.
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Soil seed banks are a reservoir of viable seeds present in the soil in plant communities. They have been studied and characterized in various ways in different habitats. However, these studies are limited to modern seed banks. This study extends seed bank studies to the Paleozoic Era. It was hypothesized that size distribution and seed density in Paleozoic seed banks exhibit similar patterns as in modern seed banks. Seed sizes and seed density of fossil seed from Wise Virginia were estimated. Modern seed bank information was obtained from published data. Data were analyzed using one-way ANOVA and Kruskal-Wallis test. The Paleozoic size distribution was predominated by larger seeds and the estimated seed density of 19 200 seeds m-3 falls within the range of modern seed banks but at a higher end of modern seed bank densities. During the Paleozoic they were sufficient to insure regeneration of these economically important forests.
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Rhoades, Erica L. "Quantifying bank erosion on the South River and its importance in assessing mercury contamination." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 82 p, 2008. http://proquest.umi.com/pqdweb?did=1597631421&sid=7&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Bobowski, Benny R. "Identification of Belowground Woody Structures Using Molecular Biomarkers." DigitalCommons@USU, 1997. https://digitalcommons.usu.edu/etd/6540.
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Within the last two decades substantial progress has been made in understanding seed bank dynamics and the contribution of the soil seed bank to a post-disturbance plant community. There has been relatively little progress, however, in understanding perennial bud bank dynamics and the contribution of the soil bud bank to secondary succession. This lack of information is due primarily to the inability to reliably identify roots, rhizomes, and lignotubers that lie dormant beneath the soil surface. This scientific investigation, therefore, addressed the issue of identification of belowground woody structures.
The first objective was to develop a methodology that utilizes molecular tools to reliably identify woody plant species from subsoil tissue samples. The second objective was to create a key in which molecular markers serve as criteria for identification and differentiation of selected tree and shrub species common to the mountains of northeast Oregon and southeast Washington. Application of restricted fragment length polymorphism (RFLP) analysis on polymerase chain reaction (PCR)-amplified rbcL gene products proved to be a reliable method to identify and differentiate 15 plants to the genus level. Two restriction enzymes, DPN II and Hha I, cut (or do not cut) the PCR-rbcL product into one to six fragments. Fragment number and length are used to develop an identification key. Plants not analyzed in this key may share the same banding patterns , resulting in a false-positive identification of unknowns. Future research needs and management implications are discussed.
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Nasermoaddeli, Mohammad Hassan [Verfasser], and Erik [Akademischer Betreuer] Pasche. "Bank erosion in alluvial rivers with non-cohesive soil in unsteady flow / Mohammad Hassan Nasermoaddeli. Betreuer: Erik Pasche." Hamburg-Harburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2012. http://d-nb.info/1048542378/34.
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Solorio, Sanchez Francisco Javier. "Soil fertility and nutrient cycling in pure and mixed fodder bank systems using leguminous and non-leguminous shrubs." Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/14446.
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Nam, Soonkie. "Effects of Reservoir Releases on Slope Stability and Bank Erosion." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/77114.
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Reservoir release patterns are determined by a number of purposes, the most fundamental of which is to manage water resources for human use. Managing our water resources means not only controlling the water in reservoirs but also determining the optimum release rate taking into account factors such as reservoir stability, power generation, water supply for domestic, industrial, and agricultural uses, and the river ecosystem. However, riverbank stability has generally not been considered as a factor, even though release rates may have a significant effect on downstream riverbank stability. Riverbank retreat not only impacts land properties but also damages structures along the river such as roads, bridges and even buildings. Thus, reservoir releases need to also take into account the downstream riverbank stability and erosion issues.
The study presented here investigates the riverbank stability and erosion at five study sites representing straight as well as inside and outside channel meander bends located on the lower Roanoke River near Scotland Neck, North Carolina. Extensive laboratory and field experiments were performed to define the hydraulic and geotechnical properties of the riverbank soils at each site. Specifically, soil water characteristic curves were determined using six different techniques and the results compared to existing mathematical models. Hydraulic conductivity was estimated using both laboratory and in situ tests. Due to the wide range of experimentally obtained values, the values determined by each of the methods was used for transient seepage modeling and the modeling results compared to the actual ground water table measured in the field. The results indicate that although the hydraulic conductivities determined by in situ tests were much larger than those typically reported for the soils by lab tests, numerical predictions of the ground water table using the in situ values provided a good fit for the measured ground water table elevation. Shear strengths of unsaturated soils were determined using multistage suction controlled direct shear tests. The test method was validated, and saturated and unsaturated shear strength parameters determined. These parameters, which were determined on the basis of results from both laboratory and field measurements, and the associated boundary conditions, which took into account representative flow rates and patterns including peaking, drawdown and step-down scenarios, were then utilized for transient seepage analyses and slope stability analyses performed using SLIDE, a software package developed by Rocscience. The analyses confirmed that the riverbanks are stable for all flow conditions, although the presence of lower permeability soils in some areas may create excess pore water pressures, especially during drawdown and step-down events, that result in the slope becoming unstable in those locations. These findings indicate that overall, the current reservoir release patterns do not cause adverse impacts on the downstream riverbanks, although a gradual drawdown after a prolonged high flow event during the wet season would reduce unfavorable conditions that threaten riverbank stability.Ph. D.
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Holmes, P. M. "A comparative study of the seed bank dynamics of two congeneric alien invasive species." Doctoral thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/17724.
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Includes bibliographies.The unique vegetation in the lowlands of the fynbos biome is threatened by alien Acacia encroachment. The seed bank dynamics of the two most widespread invaders in the region, Acacia saligma and A. cyclops, was studied to elucidate those factors contributing most to their invasive success. This information was then used to assist in developing optimal control methods. On the basis of information available prior to this study, it was predicted that both species would have large, persistent seed banks in the so.il, and that seed bank processes would provide the - key to invasive success: namely, high seed longevity and heat-stimulated germination. Seed banks were monitored for several years following clearing of the parent stand, using either sites sampled in an earlier study, or sites providing chronosequences of clearing dates. Concurrently, a demographic study of the species' seed banks, including processes from seed rain through to seedling emergence and survival, was done in dense Acacia stands and in fynbos vegetation. Acacia saligma seed banks conformed to predictions, being large and persistent owing to high percentage viability and water-impermeable dormancy. Seed banks accumulate rapidly under dense stands and are "disturbance-coupled" as they have potentially high longevity unless stimulated to germinate by fire. Although A. cyclops seed banks also may be large and long-lived, they display variable percentage viability and dormancy, with the majority of a seed cohort surviving less than a year. Acacia cyclops seed banks do not respond to heat treatment and appear to be "disturbance-uncoupled".
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Sánchez, F. J. S. "Soil fertility and nutrient cycling in the pure and mixed fodder bank systems using leguminous and non-leguminous shrubs." Thesis, University of Edinburgh, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.662220.
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The overall objective of this thesis work, in the Yucatán peninsula (México), was to establish a system with mixed woody species (leguminous/non-leguminous) to investigate the extent to which they increase nitrogen uptake and growth. The study tested the hypothesis that such mixtures may stimulate of N2 fixation from the atmosphere and the transfer of N from leguminous to non-leguminous plants. Three woody species were selected: Leucaena leucocephala (legume), Moringa oleifera (non-legume) and Guazuma ulmifolia (non-legume). More than 80% of planted seedlings survived and grew rapidly. Total biomass (fodder) production was 1.9-7.7 ton ha-1 for monocrops and 6-9 ton ha-1 for the mixtures. Nitrogen yield in the fodder was higher in the Leucaena+Guazuma mixture (285 kg N ha-1), followed by Leucaena monocrop and Leucaena+Moringa mixture (244 and 183 kg N ha-1, respectively). The δ15 N of samples from non-fixing species ranged from 2.7 to 3.2‰ (mean 3.0 ± 0.45‰). The δ15 N of L. leucocephala (0.8‰) was significantly lower, indicating that nitrogen fixation occurred in the Leucaena plants. The % Ndfa in the Leucaena mixtures ranged from 58 to 72% while in the Leucaena monocrop it was 69%, at 11 months old. Moringa leaves decomposed most rapidly, followed by Leucaena+Moringa, and, was best described by a double exponential model. The combination of Leucaena+Guazuma decomposed more slowly and pure Leucaena leaves decomposed at an intermediate rate. Over 16 weeks, Leucaena+Moringa released 65-75% of the initial N, Leucaena+Guazuma released 46-63%, and Leucaena leaves alone released, on average, 54% of their N. Lignin+polyphenols and tannins had a strong negative correlation with the rate of nitrogen release. The alteration of the decomposition and N release patterns observed when mixing plant materials of different quality provides good prospects for improving synchrony between N availability and plant N uptake.
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Whitaker, Martha Patricia Lee. "Estimating bank storage and evapotranspiration using soil physical and hydrological techniques in a gaining reach of the San Pedro River, Arizona." Diss., The University of Arizona, 2000. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_2000_373_sip1_w.pdf&type=application/pdf.
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McCue, Kimberlie A. "The ecological genetics of rarity : a study of genetic structure, inbreeding and seed bank dynamics in a rare annual plant /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9841324.
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Reinwald, Alexandra D. "Effects of Non-Surface-Disturbing Restoration Treatments on Native Grass Revegetation and Soil Seed Bank Composition in Cheatgrass-Invaded Sagebrush-Steppe Ecosystems." DigitalCommons@USU, 2013. http://digitalcommons.usu.edu/etd/1537.
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The conversion of sagebrush-steppe communities of the Great Basin into cheatgrass-dominated communities is one of the most dramatic ongoing land conversions in North America. Although restoration of these communities is a high priority to landowners and land management agencies, restoration of native vegetation is difficult. Several restoration treatments intended to increase the success of aerially‐seeded perennial grasses in cheatgrass-invaded sagebrush ecosystems were assessed to determine their effects on perennial seedling emergence and soil seed bank density and composition. Assessed restoration treatments were: 1) vegetation manipulation (sagebrush thinning and prescribed burning); 2) imazapic herbicide application; 3) seedbed amendments (aerial seeding with activated carbon addition, aerial seeding with sucrose addition); and 4) seeding frequency. The effects of these treatments were evaluated in two distinct sagebrush shrubland ecosystems in northern Utah. One is characterized as a remnant sagebrush stand with a cheatgrass-dominated understory and the other as a cheatgrass near-monoculture, completely lacking a sagebrush component. In the seed bank study, responses were assessed immediately and 1 year following treatment while in the seedling emergence study, they were assessed 2 and 3 years following treatment. Main effects of vegetation manipulation, herbicide application, and seedbed addition treatments and their interactions on perennial seedling emergence are described in Chapter 2. The effects of seeding frequency on perennial seedling emergence are also described in Chapter 2. Herbicide demonstrated potential for increasing native perennial grass emergence, although this response was delayed and not seen until 3 years post-application. Burning showed potential for increasing the emergence of perennial grasses 2 years post-burn. Results also suggest that potential exists to increase native perennial grass emergence through an increase in seeding frequency. In Chapter 3 I evaluated the effects of vegetation manipulation, herbicide application, and seedbed addition on seed pool dynamics. These results suggest that herbicide and sucrose may be useful tools for reducing exotic species richness in cheatgrass-invaded systems. Herbicide also showed potential for reducing cheatgrass seed bank densities. Additionally, results demonstrated that the reductions in cheatgrass seed bank densities observed immediately after fire are still observed 1 year post-burn.
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Mabuza, Thembisile Veronicah. "Evaluating long term effects of fire frequency on soil seed bank composition and species diversity in a semi-arid , South African savanna." Thesis, University of Fort Hare, 2011. http://hdl.handle.net/10353/346.
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Fire is generally used as a management tool for different vegetation types such as savannas and grasslands in southern Africa. In the False Thornveld of the Eastern Cape, fire is commonly used to control bush encroachment and to increase grass production, as grasses are important source of forage for domestic livestock. At the University of Fort Hare farm in the Eastern Cape, a trial was set up in 1980 to investigate the effect of burning frequency on vegetation. There are six treatments replicated twice in a completely randomized design on a 100 m x 50 m plots. The treatments comprise no burn, annual, biennial, triennial, quadrennial and sexennial burns. From this trial a study was conducted to investigate long term effect of burning frequency on species and soil seed bank diversity. Two 100 m line transects located 25 m apart were laid within each plot, and the herbaceous and woody species were identified and recorded along the line transects. Relative abundances (%) for each species were calculated for each treatment. Soil samples were collected at an interval of 13.3 m along the line transects. The samples were placed in paper bags and kept for use in a germination experiment. The seedling emergence germination method was used in the glasshouse to determine emerging seedlings, pots were filled with Hygromix growth medium and the soils from the fire trials 12 X 6 = 72 were spread on top. Soil from the control plots were also pre-treated with heat, smoke and the combination of heat and smoke. The experiment started in January 2010 and was terminated in April 2010. The Shannon-Weaver Diversity Index was used to determine species diversity for standing vegetation and germinated seedlings. Data were tested for normality and species abundances were transformed. Analysis of Variance (ANOVA) was applied to test treatment effects on geminated seedlings, species abundance and diversity at α = 0.05 significance level. Significant differences between treatment means were determined by post v hoc tests using Fischer‟s Least Significant Difference test at α = 0.05. The Pearson Moment Correlation test was used to test the relationship between vegetation and soil seed banks. Treatments had significant effects on herbaceous, woody species abundance and diversity (P < 0.05), but there was no significant treatment effect on soil seed bank diversity and on pre-germination treatments (P > 0.05). The annual, biennial and triennial burns were dominated by Themeda triandra while the quadrennial, sexennial and the control treatments were dominated by Sporobolus fimbriatus and Melica decumbens. A. karroo dominated the woody component across all treatments, but it did not change in abundance. S. fimbriatus was the most abundant in the soil seed bank across all the treatments and also in all pre-germination treatments. Species diversity was high in standing vegetation in the quadrennial, sexennial and the control treatments. There was no significant correlation between the standing vegetation and soil seed bank diversities (P > 0.05). Based on these findings it is apparent that fire can change vegetation in an area to be dominated by fire tolerant or fire intolerant species. Fire frequency, heat and smoke affects soil seed banks to a lesser extent in the False Thornveld. For the management of the False Thornveld of the Eastern Cape, less frequent burning is recommended as it increases aboveground species diversity.
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Fedrigo, Jean Kássio. "Recuperação de pastagens naturais degradadas por sobrepastejo, por meio do diferimento." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/128120.
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A herbivoria em pastagens naturais apresenta papel de destaque no direcionamento das dinâmicas vegetacionais, determinando modificações na estrutura da vegetação, nos padrões de biodiversidade e na produtividade do sistema. Essas alterações, que de modo geral contribuem para a sustentabilidade dos ecossistemas em níveis moderados de intensidade de pastejo, podem dar origem a processos de degradação ambiental quando a lotação animal utilizada é superior à capacidade de suporte das pastagens. O objetivo do presente trabalho foi avaliar a capacidade de recuperação dos padrões de diversidade, composição botânica, biomassa de forragem, altura do pasto, interceptação luminosa e do banco de sementes de uma pastagem natural degradada por sobrepastejo, por meio do diferimento, tomando como base uma área de referência. Três tratamentos baseados em exclusões estacionais do pastejo (Diferimento de Primavera, Diferimento de Outono e Pastoreio Contínuo) com três repetições foram aplicados simultaneamente em áreas manejadas por um longo período com duas intensidades de pastejo: severa e moderada (utilizada como área de referência). A pastagem manejada com pastejo severo apresentou rápida alteração na composição botânica e nos padrões de diversidade em resposta ao diferimento. Depois de dois anos de exclusões temporárias do pastejo, a composição botânica da vegetação estabelecida e do banco de sementes dessa área sofreu alterações nos grupos funcionais de gramíneas na direção das espécies características da comunidade vegetal sob pastejo moderado. Também foram verificados importantes incrementos na biomassa de forragem, altura e interceptação luminosa. A comunidade vegetal sob pastejo moderado apresentou maior equilíbrio entre diferentes grupos funcionais de plantas, especialmente entre espécies com hábitos de crescimento prostrado e cespitoso. Essa condição favoreceu o aparecimento de estrutura espacial na distribuição das espécies de plantas, maior diversidade, riqueza e melhores condições estruturais do pasto. O diferimento realizado na moderada intensidade de pastejo proporcionou dominância de espécies cespitosas, determinando decréscimo na diversidade e riqueza de plantas. As épocas de diferimento apresentaram padrões de resposta semelhantes dentro de cada intensidade de pastejo, com magnitude superior para o diferimento de primavera. Os resultados revelam a importância do diferimento do pastejo como uma ferramenta para a recuperação de pastagens degradadas por sobrepastejo.The herbivory on natural grasslands has a prominent role in driving vegetation dynamics, determining changes in vegetation structure, biodiversity patterns and primary and secondary productivity. These changes, which generally contribute to the ecosystems sustainability at moderate grazing intensities, can cause environmental degradation when the stocking rate used is higher than the pasture carrying capacity. The objective of this study was to evaluate the efficiency of temporary grazing exclusion to restore diversity, botanical composition, forage biomass, sward height, light interception and soil seed bank from a natural grassland degraded by overgrazing based on a reference area. Three treatments based on seasonal grazing exclusions (spring deferment, autumn deferment and continuous stocking) with three replications were applied simultaneously in areas managed for a long period with two grazing intensities: severe and moderate (used as reference area). The pasture managed under severe grazing showed a rapid change in botanical composition and diversity patterns in response to grazing exclusions. After two years of temporary grazing exclusions, grass functional groups of the established vegetation and soil seed bank from overgrazed pasture changed toward the characteristic species of plant community under moderate grazing. We also verified significant increases in forage biomass, sward height and light interception. The plant community under moderate grazing intensity showed better balance between different functional groups of plants, especially among species with prostrate and cespitose growth habits. This condition favored the spatial structure of appearance in the distribution of plant species, greater diversity, species richness and better structural pasture conditions. The grazing exclusion in moderate intensity grazing provided dominance tussock species, determining decrease in the diversity and richness of plants. The deferment periods showed similar response patterns within each grazing intensity with higher magnitude for spring deferment. These results reveal the importance of grazing exclusion as a tool for the recovery of degraded pastures by overgrazing.
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Sem, Graham. "The soil seed bank in Agathis australis (D. Don) Lindl. (kauri) forests of northern New Zealand and its potential role in secondary successions." Thesis, University of Auckland, 1991. http://hdl.handle.net/2292/2307.
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The soil seed bank in Agathis australis (D. Don) Lindl. (kauri) forests of northern New Zealand is quantified, and its potential role in secondary successions examined. Seed bank data from a number of kauri forest sites stratified by successional time and distance from forest edges are summarized using Detrended Correspondence Analysis (ordination) and linear regression models. A number of issues concerning secondary successions and the soil seed bank are discussed. These include: 1. The relationship between the soil seed bank and extant vegetation. 2. The nature of the soil seed bank and successional time. 3. The nature of the soil seed bank and distance from forest edges. 4. The soil seed bank, canopy gaps and gap regeneration strategies. 5. The nature of the soil seed bank and soil properties. 6. The fruiting phenology, seed rain, and soil seed bank dynamics. The forest sites ranged from 50 years to over 1,000 years old, while distance from forest edges ranged from 0.2 km to 3.5 km. Soil seed bank densities under kauri forests were 134 - 5,388 seeds m-2 with a mean density of 1,320±217 seeds m-2 which is similar to estimates reported for temperate and tropical forest sites elsewhere. The spatial distribution of seeds in the seed bank both within and between sites is highly variable. A total of 6,062 seedlings emerged from the seed bank samples. This represented 62 vascular plant species, 26 (42%) native woody, 19 (30%) native weedy, 16 (26) adventive weedy and 1 (2%) native fern. The species composition of the soil seed bank was not closely related to extant vegetation and only 11%ot canopy and 13% of understorey species were represented in the soil seed bank. Thus, 77% of extant vegetation at any given site is floristically different from that of the soil seed bank. Ordination of the data by detrended correspondence analysis (DCA) suggested that extant vegetation (canopy and understorey) and the soil seed bank contain characteristic floras. The species composition of the seed bank is variable between sites. The viable seed pool is larger under young successional forests than under older mature forests. The number of species also declined with distance from forest edges. Adventive and native weedy species were found in seed banks under mature forests and sites of considerable distances from forest edges. However, the density of the weedy species component of the soil seed bank was at least partly determined by distance from forest edges where such species are common. While buried seed is likely to contribute to the early stages of secondary succession, evidence from canopy gaps suggested that the seedling bank (formerly suppressed understorey component) is more important in gap regeneration than the soil seed bank. DCA analysis revealed that seedling bank species composition of canopy gaps and forest sites were quite different from the soil seed banks, indicating that regeneration stemmed from formerly (suppressed) understorey seedlings. Phenology and seed rain study of a mature forest remnant and a regenerating forest community showed that as little as 5% of the seed input to the forest floor enters the soil seed bank and remains viable for more than one year. Evidence is presented to suggest that in a forest community, secondary succession after large-scale or localised disturbance, is achieved more so by suppressed seedlings and recent seed rain than the soil seed bank. The soil seed bank becomes significant in secondary succession when the subsoil is disturbed by the uprooting of trees or the forest floor is exposed by tree-fall (not covered by tree-fall debris).
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Searle, Allyson B. "Reproductive Success and Soil Seed Bank Characteristics of Astragalus ampullarioides and A. holmgreniorum (Fabaceae): Two Rare Endemics of Southwestern Utah." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/3044.
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Astragalus ampullarioides and A. holmgreniorum are two rare endemics of southwestern Utah. Over two consecutive field seasons (2009-2010) we examined pre-emergent reproductive success, based on F/F and S/O ratios, from populations of both Astragalus ampullarioides and A. holmgreniorum, estimated the density of the soil seed bank of A. holmgreniorum as a measure of potential post-emergent reproductive success, and estimated seed persistence within the soil seed bank. Fruit/flower (F/F) ratios and seed/ovule (S/O) ratios varied significantly between populations and among years in both species, and showed low reproductive output in both taxa. In Astragalus ampullarioides F/F and S/O were 0.06±0.01 and 0.16±0.02, respectively (2009), and 0.14±0.01 and 0.41±0.02, respectively (2010). For Astragalus holmgreniorum F/F and S/O ratios were 0.11±0.01 and 0.38±0.02, respectively (2009), and 0.23±0.01 and 0.66±0.02, respectively (2010). Although Astragalus holmgreniorum exhibited a low soil seed bank density (4.3 seeds m-2), seed persistence data showed low a low percentage of seeds germinated during the first year in the soil seed bank. Seeds remaining in the seed bank maintained high percent viability. Soil seed persistence of Astragalus ampullarioides differed from A. holmgreniorum in that a high percentage of seeds germinated during the first year in the soil seed bank. A high percentage of viability in ungerminated seeds was also maintained in A. ampullarioides. Although these species differ in life histories and dependence on soil seed banks, an understanding of the strategies unique to each species will prove useful in management plans.
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Dairel, Mariana Correa [UNESP]. "Dinâmica do banco de sementes e germinação de gramíneas nativas e invasoras do Cerrado." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/154121.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Espécies invasoras são aquelas capazes de se estabelecer em áreas além de sua ocorrência natural, ultrapassando barreiras geográficas e constituindo novas populações viáveis. A introdução de gramíneas africanas no Cerrado, como Melinis minutiflora P. Beauv e Urochloa brizantha (Stapf) R.D. Webster, pode levar a uma baixa heterogeneidade do sistema, deixando-o mais suscetível a distúrbios ambientais, alterando o equilíbrio da comunidade e os serviços ecossistêmicos. Em sistemas frequentemente perturbados, clareiras são criadas na paisagem e novas espécies são recrutadas para colonizar o espaço aberto, processo esse regido pelo nicho da regeneração. Espera-se que estes nichos se sobressaiam nas espécies invasoras em relação às espécies nativas, conferindo-lhes vantagens adaptativas na colonização desses espaços. Dessa maneira, o objetivo do estudo foi avaliar a dinâmica do banco de sementes de gramíneas em áreas com e sem invasão biológica, além de avaliar diferentes fatores que influenciam a germinação de gramíneas nativas. A área de estudo está inserida na Estação Ecológica de Itirapina, onde até 1998 havia uma plantação de Pinus caribaea, a qual foi removida e desde então a área está sob regeneração natural, sem interferência, com alto grau de invasão por gramíneas africanas. No primeiro capítulo, as amostras de solo foram coletadas nas parcelas experimentais controle do projeto da Profa. Dra. Alessandra Fidelis (FAPESP 2015/06743-0), delineado então parcelas com três tratamentos: dominada por uma das duas espécies invasoras, Melinis minutiflora e Urochloa brizantha, e parcelas com domínio de vegetação nativa (4parcelas/tratamento= 12 unidades amostrais). No segundo capítulo, as sementes de gramíneas nativas foram coletadas na Estação Ecológica de Itirapina e na Reserva Natural Serra do Tombador, triadas em laboratório e submetidas a tratamentos de flutuação de temperatura, simulando a oscilação de temperatura diária sobre a superfície do solo, e choques de temperatura simulando a passagem do fogo. O conhecimento mais detalhado sobre o banco de sementes em áreas invadidas é fundamental para elaboração de práticas de controle e manejo dessas espécies. Além disso, a germinação e viabilidade das sementes de gramíneas nativas são fatores importantes tanto para elucidar a regeneração natural via semente, compreendendo processos ecológicos relacionados à quebra da dormência fisiológica, quanto para aplicação de métodos físicos de restauração do Cerrado, como a semeadura direta.
Invasive species are those capable of establishing themselves in areas beyond its natural occurrence, surpassing geographical barriers and constituting new populations. The introduction of African grasses in Cerrado, Melinis minutiflora P. Beauv and Urochloa brizantha (Stapf) R.D. Webster, may low heterogeneity of the system, making it more susceptible to altering the balance of the community and ecosystems. In frequently disturbed systems, clearings are created in the landscape and new species are recruited to colonize the open space, which is governed by the regeneration niche. These niches are expected to be better in invasive species in relation to native species, giving them adaptive advantages in the colonization of these spaces. In this way, the objective of the study was to evaluate the dynamics of grasslands in areas with and without biological invasion, in addition to evaluating different factors that influence the germination of native grasses. The study area is located in the Estação Ecológica de Itirapina, where until 1998 there was a plantation of Pinus caribaea, which has been removed and since then the area is under natural regeneration, without interference, with a high invasion of Urochloa brizantha and Melinis minutiflora. In the first chapter, the soil samples were collected in the control plots of the project of Profa. Dr. Alessandra Fidelis (FAPESP 2015 / 06743-0), outlined then plots with three treatments: dominated by one of the two invasive species, Urochloa brizantha and Melinis minutiflora, and plots with dominance of native vegetation (4plots / treatment = 12 sample units). In the second chapter, grass seeds were collected at Estação Ecológica de Itirapina and in Reserva Natural Serra do Tombador, triads in the laboratory and submitted to treatments of temperature fluctuation, simulating the daily temperature oscillation on the soil surface, and heat shock simulating the passage of fire. More detailed knowledge about the soil seed bank in invaded areas is fundamental for the elaboration of practices of control and management of these species. In addition, the germination and viability of native grass seeds are important factors both to elucidate the natural regeneration through seed, comprising ecological processes related to break physiological dormancy of seed, and for application of physical methods of restoration of Cerrado, such as direct sowing.
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Navarra, Jennifer J. "Species composition and spatiotemporal pattern of the seed bank and vegetation in native and degraded Florida rosemary scrub." Master's thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4645.
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Due to large pulses of recruitment immediately after fire and population decline with time-since-fire, I predicted seed density with time-since-fire would follow a unimodal function with low density in early and late years post-fire, and highest density at intermediate time-since-fire. I compared seed density data among sites with different time-since-fire: two sites each of three, six, ten and 24 years time-since-fire and three long-unburned sites (greather than]24 years). Variability in seed bank composition and density increased with time-since-fire and only recently burned stands were distinctly different from the other time-since-fire age classes. Some species and functional groups did exhibit a quadratic or cubic association to time-since-fire (ruderal herbs, subshrubs, Ceratiola ericoides, Lechea cernua, Paronychia chartacea, Phyllanthus tenellus); however, timing of the peak in seed density varied depending on life span and age of reproductive maturity. Scrub herbs were the most abundant functional group in the seed bank and showed highest density in the first ten years post-fire. This pattern corresponds to the pattern of aboveground species abundance and suggests abundances above- and belowground are closely linked. Understanding the dynamics of the seed bank in both naturally and anthropogenically disturbed communities in Florida rosemary scrub is important for the restoration of scrub habitat and management of existing populations of endangered and threatened scrub species endemic to the Lake Wales Ridge in central Florida.; The soil seed bank plays a dynamic role in the regeneration of plant communities after natural and anthropogenic disturbance. In this thesis, I addressed how disturbances influence the vegetation and seed bank of Florida rosemary scrub. In Chapter One I evaluated changes in species composition and spatiotemporal pattern of the vegetation and seed bank along a gradient of disturbance. During the summers and winters of 2007-2009 percent ground cover and seed bank species composition were assessed among replicates of three vegetation types subjected to minimal, moderate, and extreme anthropogenic disturbance (native rosemary scrub, degraded scrub, and agriculturally improved pasture, respectively). These vegetation types shared the same soil and topographic characteristics but differed in disturbance history. I found that species composition and spatial pattern varied with disturbance. In pastures the compositional and structural characteristics of rosemary scrub were lost and only native scrub species able to evade herbivory persisted in this community. Native and degraded scrub differed most from each other in species abundances and spatial pattern. Degraded scrub showed highest abundance of subshrubs and a spike moss species, while rosemary scrub was dominated by shrubs. The seed banks of scrub herbs in degraded scrub had a tendency towards a random spatial distribution that lacked association with aboveground cover. Conversely, rosemary scrub seed banks tended to have an aggregated distribution and were associated with occurrence of conspecific species aboveground, litter, and shrub cover. These results indicated a change in the spatial heterogeneity of the seed banks of scrub herbs in degraded scrub. In Chapter Two I evaluated changes in seed bank density with time-since-fire in native rosemary scrub.ID: 028917091; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.)--University of Central Florida, 2010.; Includes bibliographical references (p. 108-123).
M.S.
Masters
Department of Biology
Sciences
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Sima, Sheriff Saihou. "Whose technology counts? : a study of promotion of soil and water conservation and its acceptance by smallholder farmers, with special reference to the North Bank Division, the Gambia." Thesis, University of East Anglia, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393140.
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OLIVEIRA, Rafael Domingos de. "Banco de sementes do solo de três fitofisionomias da Floresta Nacional do Araripe, Ceará, Brasil." Universidade Federal Rural de Pernambuco, 2013. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/5259.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Due to the current degradation of forests, researches have been performed to understand the natural regeneration process of these areas. Regeneration from seeds stored in the soil seed bank is an important strategy on the ecosystems dynamics. Soil seed bank can present different in time and space and vary in relation to the different phytophysiognomies or microhabitats in an area and vary in response to the influence of precipitation in environments with a high seasonality. Therefore, this study aims to detect the influence of variables like different phytophysiognomies, depths of seed deposition in the soil and climatic seasons on the species richness and seed density in the soil seed bank of three phytophysiognomies of Araripe National Forest, Ceará, Brazil. Soil seed bank samples was performed in cerrado sensu strictu, cerradão and semideciduous seasonal forest (humid forest) at the end of the rainy and dry seasons where, in each, it was collected 50 samples of litter and mineral soil (0-5 cm depth). To determine species richness and composition and seed bank density, it was performed the seedling emergence method. GLM was used to verify the influence of phytophysiognomies, depths and seasons on the richness and seed density. To detect differences in the mean values of richness and density it was performed a post-hoc Tukey test (5%). A NMDS was used to compare the seed bank structure between phytophysiognomies and the similarities was verified with ANOSIM test. SIMPER function was used to indicate the contribution percentage of each species for the dissimilarity between samples. It was registered 24, 29 e 30 species and 174, 261 and 399 seeds.m-2 in cerrado, cerradão and humid forest seed banks, respectively. In cerrado and humid forest, both species richness and seed density, is in the litter or in the soil, did not differ among climatic seasons. In cerradão, both species richness and seed density observed in the mineral soil were significantly different among seasons. Depth shows a higher explanatory power on the variation of species richness (50.63%) and seed density (22.73%), followed by phytophysiognomy (8.95% and 4.18%, respectively for the species richness and seed density). Only the variable climatic season in a given year did not allow to predict the seed density variation and their low influence power on the species richness leads to suggest that the occurrence of a seasonal pattern and its interaction with others variables is complex, making it difficult to understand the soil seed bank dynamic in forests.
Devido à atual degradação das formações florestais, pesquisas têm sido realizadas para conhecer os processos naturais de regeneração dessas áreas. A regeneração a partir de sementes armazenadas no banco do solo é um importante artifício na dinâmica dos ecossistemas e pode apresentar-se diferente no tempo e no espaço, podendo variar em relação às diferentes fitofisionomias ou microhabitats existentes em uma determinada área, assim como por influência dos totais pluviométricos, em ambientes com marcada sazonalidade, por exemplo. Desse modo, o presente estudo pretende detectar a influência de variáveis como diferentes fitofisionomias, profundidades de deposição da semente no solo e estações climáticas e suas diferenças sobre a riqueza de espécies e densidade de sementes no banco de sementes do solo em três fitofisionomias da Floresta Nacional do Araripe, Ceará, Brasil. A amostragem do banco de sementes do solo foi realizada em áreas de cerrado sensu stricto, cerradão e floresta estacional semidecidual (mata úmida) no final das estações chuvosa e seca onde, em cada uma delas, foram coletadas 50 amostras de serrapilheira e de solo (0-5 cm de profundidade). Para determinação da riqueza e composição de espécies e densidade do banco de sementes foi realizado o experimento de emergência de plântulas. A influência das fitofisionomias, profundidades e estações sobre a riqueza e densidade de sementes foi verificada através do GLM e para detectar diferenças nos valores médios de riqueza e densidade, foi aplicado o teste de Tukey a posteriori (5%). Para comparar a estrutura do banco de sementes entre fitofisionomias foi realizado um NMDS e a similaridade entre as amostras foi verificada através do teste ANOSIM. A função SIMPER foi utilizada para indicar o percentual de contribuição de cada espécie para a dissimilaridade entre as amostras. Foram registradas 24, 29 e 30 espécies e 174, 261 e 399 sem.m-2 no banco de sementes do cerrado, cerradão e mata úmida, respectivamente. No cerrado e na mata úmida, tanto a riqueza de espécies quanto a densidade de sementes seja na serrapilheira ou no solo não diferiu entre estações climáticas. No cerradão, a riqueza de espécies e a densidade de sementes encontrada no solo foram significativamente diferentes entre as estações. A profundidade exerceu um maior poder de explicação sobre a variação de riqueza de espécies (50,63%) e densidade de sementes (22,73%), seguido da variável fitofisionomia (8,95% e 4,18%, respectivamente para a riqueza de espécies e densidade de sementes). Apenas a variável estação climática em um determinado ano não permitiu predizer a variação da densidade de sementes e o seu baixo poder de influência sobre a riqueza de espécies leva a sugerir que a ocorrência de um padrão sazonal e sua interação com outras variáveis é complexa, dificultando a compreensão sobre a dinâmica do banco de sementes do solo das florestas.
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McEwen, Amiana Marie. "Abundance, Distribution, and Geometry of Naturally Occurring Macropores in Stream Banks." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/95948.
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Preferential flow paths are areas of substantially higher permeability than surrounding media. Macropores and soil pipes are a type of preferential flow path where conduit-like voids in the subsurface are typically greater than three millimeters in diameter. They are known to occur in agricultural and forest soils, often as a result of biological and physical processes. Macropores also exist in stream banks and have the potential to enhance the exchange of water and solutes between the channel and riparian groundwater, yet the geographic distribution of bank macropores is unknown. Here we determined the abundance, distribution, and geometry of naturally occurring surface-connected macropores in the banks of 20 streams across five physiographic provinces in the Eastern United States. We identified a total of 1,748 macropores, which were present in all 20 streams, with 3.8 cm average width, 3.3 cm average height, 11.5 cm average depth, and 27.9 cm average height above water surface elevation. Macropore abundance, distribution and geometry were statistically different between physiographic provinces, stream orders, and soil textures, with the latter being the most important. Macropores tended to be larger and more abundant in soils with a high cohesiveness and a low hydraulic conductivity compared to soils with a low cohesiveness and high hydraulic conductivity. As a result, streams with greater longitudinal heterogeneity of soil texture also had greater heterogeneity of macropore density. However, macropore size and height above baseflow water surface elevation also increased with stream order and therefore stream size. This work represents the first attempt to characterize macropores across a variety of riverine systems and presents evidence that macropores may play an important role in hyporheic exchange within stream banks. These results may have water quality implications, where macropores may enhance hyporheic exchange yet reduce the filtering capacity of riparian buffer zones.MS
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Samhan, Sobhi A. R. [Verfasser], Herbert [Akademischer Betreuer] Poellmann, Kurt [Akademischer Betreuer] Friese, and Heinz [Akademischer Betreuer] Hotzel. "Occurrences and transport of trace metals in wastewater, sediment and soil : case study Al-Qilt catchment, West Bank, Palestine / Sobhi A. R. Samhan. Betreuer: Herbert Poellmann ; Kurt Friese ; Heinz Hotzel." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2013. http://d-nb.info/1035405695/34.
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Andrade, Greice Kelly Oliveira. "Avaliação da regeneração natural em áreas de reflorestamento, no município de Laranjeiras-SE." Universidade Federal de Sergipe, 2015. https://ri.ufs.br/handle/riufs/3004.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESMany researches have been focused on reforestation projects, taking advantages on the self recuperation mechanism of the frorest such as seed rain, soil seed bank and seedling banks. Seed rain is an initial process which develops the dynamic, organization and structuration of the forest. However, the seed bank is one of the most important factors for natural recolonization of affected areas which start the succession process. Through this natural regeneration, a set of individuals are able to be recruited to the upper stages. In this way, the present study was performed aiming to evaluate the plant species establishment strategies through natural regeneration, in an area in the city of Laranjeiras-SE. Thirty plots were installed, and in center of these plots, collectors were installed (1m x 1m) to estimate the seed rain. To characterize the seed bank, was collected from August 2014 (corresponding to the rainy season in the region) to February 2015 (dry season), a soil sample from the center of each subplot (1m x 1m) through a metal jig which was introduced into the soil to remove a 5 cm layer. In the seedling bank evaluation, height and diameter of seedlings were analyzed between August 2014 (rainy season) and Februare 2015 (dry season) in subplots (1m x 1m). In seed rain were found 7,788 seeds, in which Shinus terebinthifollius Raddi (aroeira) presented a higher number of seeds collected with 6,799 samples and its frequency was 87.84% in relation with others species. The autochoric syndrome of dispersion was observed to Centrosema brasilianum (L.) Benth., Fabaceae 2 and Anadenanthera colubrina (Vell.) Brenan, for Asteraceae 1 and Bignoniaceae 1 the dispersion syndrome observed was anemocoric and to Schinus terebinthifollius and Passiflora mansoi (Mart.) Mast, the dispersion syndrome was zoochoric. In the study of seed bank, it was found a total of 171 seeds. The seed bank analyzes by the rainy season and dry season, Schinus terebinthifollius prevailed with more individuals in the rainy season. However, Fabaceae sp prevailed in the dry season. The distribution of species per plot was heterogeneous in both seasons, but presented a better distribution in the rainy season. In the study of seedlings bank, samples were found belonging to seven families and thirteen species. Shinus terebinthifollius represented 28% of total specimen, followed by Genipa Americana L. with 20%. The rainy season showed better seedling distribution along the plots. The processes of natural regeneration at studied area have presented a diversity of species into three regeneration kinds evaluated in different fructification seasons, establishing int this way, a steady supply of seeds, enabling the development of new individuals for future process.
Inúmeras pesquisas têm sido voltadas a projetos de reflorestamentos, aproveitando o próprio mecanismo de recuperação da floresta como chuvas de sementes, bancos de sementes do solo e bancos de plântulas. A chuva de sementes é um processo inicial que desenvolve a dinâmica, organização e estruturação da floresta. No entanto, o banco de sementes é um dos fatores mais importantes para a recolonização natural das áreas afetadas dando início ao processo sucessional. Por meio dessa regeneração natural, um conjunto de indivíduos são capazes de ser recrutados para os estádios superiores. Dessa forma, o presente trabalho foi realizado objetivando avaliar as estratégias de estabelecimentos das espécies vegetais por meio da regeneração natural, numa área em reflorestamento, no município de Laranjeiras-SE. Foram instaladas 30 parcelas, e no centro dessas parcelas foram instalados coletores (1m x 1m) para estimar a chuva de sementes. Para a caracterização do banco de sementes, foi coletada, no mês de agosto de 2014 (correspondente a estação chuvosa na região) e fevereiro de 2015 (estação seca), uma amostra de solo no centro de cada subparcela (1m x 1m), através de um gabarito metálico que foi introduzido no solo para remover uma camada de 5 cm. Na avaliação do banco de plântulas, foram realizadas análises de altura e diâmetro das plântulas, entre agosto de 2014 (estação chuvosa) a fevereiro de 2015 (estação seca), em subparcelas (1m x 1m). Na chuva de sementes foram encontradas 7.788 sementes, dentre as quais a espécie Schinus terebinthifollius Raddi (aroeira) apresentou maior número de sementes coletadas, com 6.799 amostras possuindo frequência de 87,84% em relação as outras espécies. A síndrome de dispersão autocórica foi observada para as espécies Centrosema brasilianum (L.) Benth., Fabaceae 2 e Anadenanthera colubrina (Vell.) Brenan, para Asteraceae 1 e Bignoniaceae 1 a síndrome de dispersão observada foi anemocorórica e para as espécies Schinus terebinthifollius e Passiflora mansoi (Mart.) Mast, a síndrome de dispersão presente foi a zoocórica. No estudo do banco de sementes, foi encontrado um total de 171 sementes. Nas análises por estação chuvosa e seca do banco de sementes, a espécie Schinus terebinthifollius prevaleceu com maior número de indivíduos na estação chuvosa. Contudo, prevaleceu a espécie Fabaceae 1 na estação seca. A distribuição das espécies por parcela foi heterogênea em ambas as estações, porém apresentou uma melhor distribuição no período chuvoso. No estudo do banco de plântulas, foram encontradas amostras pertencentes a sete famílias e treze espécies. A espécie Schinus terebinthifollius representou 28% dos espécimes amostrados, seguida por Genipa americana L. com 20%. Na estação chuvosa houve uma melhor distribuição de plântulas ao longo das parcelas. O processo de regeneração natural da área de estudo apresentou uma diversidade de espécies nas três formas de regeneração avaliadas com diferentes épocas de frutificação, estabelecendo assim, uma constante oferta de sementes, viabilizando o desenvolvimento de novos indivíduos para processos futuros.
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Gervinskas, Vytenis. "Armens apvertimo kampo įtaka vasarinių miežių derlingumui ir piktžolėtumui." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20110603_115306-63046.
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Tyrimo tikslas – nustatyti armens apvertimo kokybės įtaką vasarinių miežių (Hordeum vulgare L.) pasėlio piktžolėtumui modeliniame lauko tyrime. Modelinis lauko tyrimas vykdytas LŽŪU bandymų stotyje 2009-2010. Tirti keturi armens apvertimo variantai: armuo apverstas 135° (kontrolinis variantas), 157,5º ir 180° kampu bei neverčiamas (0°). Įrengti stacionarūs 0,25 m2 modeliniai laukeliai Nustatyta piktžolių vasarinių miežių derliuje, rūšinė sudėtis, biomasė ir skaičius, miežių antžeminės dalies biomasė ir stiebų skaičius, derlius, 1000 grūdų masė ir kiti parametrai. Pasėlio piktžolėtumo ir piktžolių sėklų pasiskirstymo armenyje duomenys vertinami dispersinės analizės metodu, nustatant esminio skirtumo ribą (R05, R01) ir vidurkių vidutinę kvadratinę paklaidą Apibendrinus tyrimo duomenis, gauti rezultatai parodė, kad esant skirtingam armens apvertimo kampui piktžolių biomasė pasėlyje skyrėsi iki 3 kartų. Piktžolių sėklų atsargose dirvoje vyravo trumpaamžės piktžolės, daugiausiai baltoji balanda (Chenopodium album L.). Paviršiniame dirvos sluoksnyje piktžolių sėklų pasiskirstymas tarp variantų buvo nevienodas (skyrėsi kelis kartus) skirtingais metais. Eksperimento rezultatai iš esmės patvirtino hipotezę, kad nuo armens apvertimo kampo priklauso pasėlio piktžolėtumas, tačiau reikėtų atlikti papildomus tyrimus ir nustatyti optimalų armens apvertimo kampą mūsų klimato ir dirvožemių sąlygomis.The aim of the investigation was to estimate the influence of arable soil turnover angle on spring barley (Hordeum vulgare L.) crop yield and weediness in model field experiment. The model field experiment carried out at the Experimental Station of LŽŪU in 2009-2010. Four arable soil turnover angle treatments were investigated: 135° (control treatment), 157.5° and 180° and not overturned (0°). Stationary 0.25 m-2 model fields were equipped. The following parameters were measured: weeds harvested along with barley (weed species composition, weed biomass and number), spring barley density, and stem density, yield, 1000 grain weight and other parameters. Weediness and weed seed distribution in the arable soil layer were assessed by variance method by determining the LSD05, LSD01 and the average SEM Summarized survey data revealed that weed biomass in the spring barley crop differed by three times at the different arable soil turnover angle, short-living weeds dominated in the seed bank, mostly Chenopodium album L., weed seed distribution in top soil layer as well as spring barley yield has been uneven between the treatments (several times) in different years. Experimental results broadly confirmed the hypothesis that the arable soil overturning angle has influence on the crop yield and weediness, but further studies should be carried out to determine the optimum turnover angle for our climate and soil conditions.
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Martins, Andreza Maria. "O processo de regeneração natural e a restauração de ecossistemas em antigas áreas de produção florestal." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/11/11150/tde-18052009-150204/.
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Em empresas florestais que plantam florestas de rápido crescimento voltadas ao abastecimento industrial, é comum, hoje em dia, a existência de áreas de plantios comerciais que devem ser revertidos para áreas de vegetação natural. Entretanto, dependendo das condições locais e do contexto da paisagem, nem sempre os processos naturais de regeneração são suficientes para garantir que a vegetação natural se desenvolva e se auto-sustente nessas áreas. Este estudo avaliou os processos de regeneração natural e a efetividade de algumas técnicas de restauração florestal para indicar a melhor estratégia aplicável em larga escala, em áreas anteriormente manejadas com as culturas de Eucalyptus sp e Pinus sp, que foram abandonadas com o intuito de serem incorporadas como reservas legais. O projeto foi desenvolvido no município de Borebi, SP, em duas fazendas, sendo uma em ecossistema de cerrado latu sensu e outra de floresta estacional semidecidual. Em cada área foi instalado um experimento em blocos ao acaso, com cinco repetições e cinco tratamentos, com parcelas de 30 x 30m. Os tratamentos foram: T1: controle, T2: semeadura direta de dez espécies florestais de rápido crescimento; T3: plantio convencional de 19 espécies florestais de crescimento lento, médio e rápido; T4: condução da regeneração natural através de tratos silviculturais e T5: picagem da cobertura vegetal e revolvimento do solo. A regeneração natural de indivíduos lenhosos existente foi levantada em duas classes: altura a 1,30 m (parcela toda) e altura > que 0,50m e < que 1,30m (em três subparcelas de 1 x 30m ), antes e após (12 meses) a implantação dos tratamentos. O banco de sementes do solo foi amostrado antes da instalação e duas vezes após, e o solo superficial retirado de uma área de 315cm² e profundidade de 5cm, formando duas amostras compostas por parcela. Para a chuva de sementes foram instalados cinco coletores por parcela, com dimensões de 0,50 x 0,50m cada. Tanto o banco como a chuva de sementes apresentaram baixa porcentagem de espécies lenhosas e alta densidade de algumas espécies herbáceas invasoras. A regeneração natural apresentou espécies típicas da fase inicial da sucessão, com predomínio de espécies não constituintes. A maior similaridade na composição das espécies ocorreu na comparação entre a vegetação e a chuva de sementes e a menor na comparação da vegetação com o banco de sementes. O tratamento T4 (condução da regeneração) apresentou efeito significativo na área basal, densidade, número de espécies e diversidade de espécies da regeneração natural, em ambas as áreas, após 12 meses de implantação, mostrando-se mais viável ecologicamente e economicamente em relação aos demais.In Forest Companies that cultivate fast-growing forest species for industrial supply, it has been usual the existence of commercial production areas that need to be converted in protected areas with native vegetation. Nevertheless, depending on local conditions and landscape context, the natural regeneration process is not enough to guarantee the successional development This work aimed at investigating the natural regeneration process and the effectiveness of some forest restoration techniques to be applied in large scale in, former Eucalyptus sp and Pinus sp plantations, which were abandoned to be incorporated as protected areas. The project was developed at Borebi municipality, SP, in two forest farms, one comprising latu sensu savana formations, and the other corresponding to seasonal semideciduous forest. In each experimental area a complete randomized block experiment with five treatments and five replicates was installed, with 30 x 30 m plots. The treatments were: T1: control; T2: direct seeding of 10 fast growing forest species; T3: conventional planting of 19 species with different growth characteristics; T4: management of natural regeneration by silvicultural treatments; T5: tillage of ground vegetation cover and plowing. Natural regeneration was surveyed before and 12 months after the experiment installation, when all woody individuals with height 1.30m were measured; the individuals with height 0.50m and <1.30m were surveyed in three 1 x 30m subplots within each plot. The soil seed bank was sampled before and two times after the treatments, were 315cm² and 5cm depth samples formed 2 composite samples by each plot. Seed rain was studied by five 0,50 x 0,50m litter traps installed in each plot. The soil seed bank and seed rain had a low percentage of woody species and high density of some nonconstituent invasive herbaceous species. The natural regeneration showed a predominance of early successional species, but was dominated by nonconstituent species. The higher similarity in species composition occurred between the natural regeneration and the seed rain, and the smaller between the natural regeneration and the soil seed bank. The regeneration management treatment (T4) showed a significant effect in basal area, density, species diversity and species richness of natural regeneration after 12 months, indicating to be the most viable ecologically and economically in comparison with the other, for the local conditions.
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Small, Christine Jodie. "Herb Layer Dynamics and Disturbance Response in the Mixed Mesophytic Forest Region of Southeastern Ohio." Ohio University / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou994780001.
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Chami, Luciane Belmonte. "VEGETAÇÃO E MECANISMOS DE REGENERAÇÃO NATURAL EM DIFERENTES AMBIENTES DA FLORESTA OMBRÓFILA MISTA NA FLONA DE SÃO FRANCISCO DE PAULA, RS." Universidade Federal de Santa Maria, 2008. http://repositorio.ufsm.br/handle/1/8632.
Full textAbstract:
This study evaluated the phitosociology of the Mixed Rain Forest and its mechanisms of regeneration (seeding banks, seed rain and soil seed bank). The data were collected in six conglomerates, being every one subdivided in 16 parcels of 20m x 20m. In the Chapter I it was studied the adult vegetation, where the tree and shrub species with circumference at the height of the chest equal or bigger than 30 cm were identified and measured. The species were classified in ecological groups and, on the basis
of the density data, it was made an analysis of the grouping using the TWINSPAR method (Two-Way
Indicattor Species Analysis). The groupings were characterized in relation to their horizontal structure.
On the area, they 86 species were identified, being 18 pioneers, 25 secondary initials, 16 secondary delayed, 14 climax, and 13 were classified in more than one group. Three groupings were characterized (G1, G2 nd G3), in which gained special prominence the species Siphoneugena reitzii, Araucaria angustifolia and Sebastiania commersoniana, respectively in environments of hillside, of
emergent trees and humid environments. In the chapter II based in the groupings formed in the adult vegetation, it was evaluated the mechanisms of regeneration. The seed rain was evaluated during the months of January to December of 2007, by means of the disposition of 96 collectors of 1 m2, in which it was observed the significant difference among the three groups in the quantity of seeds dispersed. In the study of the soil seed bank which was held through the collect of 5 cm of ground (taking out the burlap), it was observed that the group G1 showed significant difference in the quantity of storaged
seeds in relation to groups G2 and G3. Seeding banks was showed in 72 showing unities of 2 m x 2 m, in which all the individuals with a size equal or bigger than 20 cm and DAP equal or lesser than 1 cm were identified and counted. The statistic analysis showed that, quantitatively, there was a significant difference among the three groups in relation to numbers of individuals in the seeding bank.
For the joint analyses of the adult vegetation and mechanisms of regeneration, it is concluded, initially
that the seeding bank, for having presented a bigger similarity with the vegetation, it can be the
principal strategy of the maintenance of this forest. The seed rain is a basic strategy to the maintenance of the seeding bank. The seed bank didn´t present a flower potential for substituting the species present in the tree vegetation after alteration of the forest, being an essential strategy to the initial reestablishment of the area., due to the high density of the herbaceous plants. It was considered as tree basic species Araucaria angustifolia, Siphoneugena reitzii, llex brevicuspis, Podocarpus lambertii e Vernonia discolor, in hillside environments; Araucaria angustifolia, Casearia decandra,
Blepharocalyx salicifolius, llex paraguariensis and Sebastiania brasiliensis in emergent tree environments; Araucaria angustifolia, Blepharocalyx salicifolius, Cryptocarya aschersoniana, llex brevicuspis, Sebastiania commersoinana e Siphoneugena reitzii in lands of bigger moistness. Through these informations one gives credit that such species will have greater possibility of stablishment in places with similar environment characteristics.Este estudo avaliou a fitossociologia de Floresta Ombrófila Mista e os seus mecanismos de regeneração (banco de plântulas, chuva de sementes e banco de sementes do solo). Os dados foram coletados em seis conglomerados, sendo cada um subdividido em 16 parcelas de 20 m x 20 m. No Capítulo I, estudou-se a vegetação adulta onde as espécies arbóreas e arbustivas com circunferência à altura do peito (CAP) igual ou maior de 30 cm foram identificadas e medidas. As espécies foram classificadas em grupos ecológicos e, com base nos dados de densidade, foi realizada uma análise de agrupamento utilizando o método TWINSPAN (Two-way Indicator Species Analysis). Os agrupamentos foram caracterizados em relação à sua estrutura horizontal. Na área, foram identificadas 86 espécies, sendo 18 pioneiras, 25 secundárias iniciais, 16 secundárias tardias, 14 clímax, e 13 foram classificadas em mais de um grupo. Foram caracterizados três agrupamentos (G1, G2 e G3), em que se destacaram as espécies Siphoneugena reitzii, Araucaria angustifolia e Sebastiania commersoniana, respectivamente, em ambientes de encosta, de árvores emergentes e úmido. No capítulo II, partindo dos agrupamentos formados na vegetação adulta, foram avaliados os mecanismos de regeneração. A chuva de sementes foi avaliada durante os meses de janeiro a dezembro de 2007 por meio da disposição de 96 coletores de 1 m², na qual foi observada diferença significativa entre os três grupos na quantidade de sementes dispersadas. No estudo do banco de sementes do solo, realizado mediante a coleta de 5 cm de solo (retirando a serapilheira), observou-se que o grupo G1 demonstrou diferença significativa na quantidade de sementes estocadas em relação aos grupos G2 e G3. O banco de plântulas foi amostrado em 72 unidades amostrais de 2 m x 2 m, em que todos os indivíduos com altura igual ou maior que 20 cm e DAP igual ou menor 1 cm foram identificados e contados. A análise estatística mostrou que, quantitativamente, houve diferença significativa entre os três grupos quanto ao número de indivíduos no banco de plântulas. Pela análise conjunta da vegetação adulta e mecanismos de regeneração, conclui-se, inicialmente, que o banco de plântulas, por ter apresentado maior similaridade com a vegetação, pode ser a estratégia principal de manutenção dessa floresta. A chuva de sementes é uma estratégia fundamental à manutenção do banco de plântulas. O banco de sementes não apresentou potencial florístico para substituir as espécies presentes na vegetação arbórea após alteração da floresta, sendo uma estratégia essencial ao restabelecimento inicial da área, dada a elevada densidade de plantas herbáceas. Foram consideradas como espécies arbóreas fundamentais Araucaria angustifolia, Siphoneugena reitzii, Ilex brevicuspis, Podocarpus lambertii e Vernonia discolor, em ambientes de encosta; Araucaria angustifolia, Casearia decandra, Blepharocalyx salicifolius, Ilex paraguariensis e Sebastiania brasiliensis, em ambiente de arvores emergentes; Araucaria angustifolia, Blepharocalyx salicifolius, Cryptocarya aschersoniana, Ilex brevicuspis, Sebastiania commersoniana e Siphoneugena reitzii em terrenos de maior umidade. Por meio dessas informações, acredita-se que tais espécies terão maior chance de estabelecimento em locais com características ambientais semelhantes.
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Sccoti, Marta Silvana Volpato. "MECANISMOS DE REGENERAÇÃO NATURAL EM FLORESTA ESTACIONAL DECIDUAL, SANTA MARIA, RS." Universidade Federal de Santa Maria, 2009. http://repositorio.ufsm.br/handle/1/8644.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorThis study evaluated the mechanisms of natural regeneration represented by seeds rain, seeds bank of the soil and the regeneration vegetation, considering the seedlings bank and the established regeneration, in a fragment of Estacional Decidual Forest. The evaluation was made with 70 randomized samplings in 14 parcels inside four bands, with systematic distribution in the area. The seeds rain was studied using 70 collectors with 1 m x 1 m, the collected material was analyzed monthly, during a year. In the seeds bank was collect 70 samplings using an iron collector (25 x 25 cm) on the soil surface and adjusting the studied samplings to 5 cm of deep. The collected material was taken to the Laboratory of Silvicultura of the Departament of Ciências Florestais of the Federal University of Santa Maria, where it was evaluated during seven months. The seeds bank was evaluated in 70 sampling units of 2 x 2 m where was identified and measured all plants with h ≥ 30 cm and DBH < 1 cm, the natural regeneration in the area was evaluated in 70 sampling units of 5 x 5 m, in which were identified and measured all plants with 1cm ≤ DBH ≤ 5 cm. The regeneration mechanisms were analyzed in groups formed in the adult vegetation. In the seeds rain it was observed the presence of 73 species, mainly trees. The seeds bank of the soil show predominance of herbaceous species, and some trees and bush-like species, pioneer species and secondary species. In the seedlings bank, was observed the presence of light demanding tree species and eciofiles species, while in the established natural regeneration the predominance was of shadow species. The seed bank of the soil and the established natural regeneration show different comportment for the group 1 and 2 in the adult vegetation, while the seeds rain and seedlings bank show uniformity in the forest. The species with the bigger probability to perpetuate in the studied forest reminiscent and in the near areas were Gymnanthes concolor, Soroceae bonplandii, Eugenia rostrifolia, Trichilia claussenii, Trichilia elegans, Myrocarpus frondosus, Cupania vernalis, Nectandra megapotamica and Dasyphylum spinescens, these species can be used to enrichment and recuperation of the forest. The most restricted species were Cordia tricotoma, Luehea divaricata, Sebastiania commersoniana and Syagrus rommanzoffiana, these species may grow in the forest if used the right treatments to their perpetuation. The indicative species in the adult vegetation groups have the seeds rain and the seedlings bank as the main mechanisms for their conservation in the forest reminiscent.
Este estudo avaliou os mecanismos de regeneração natural, representada pela chuva de sementes, banco de sementes do solo, e vegetação em regeneração, considerando banco de plântulas e regeneração natural estabelecida, em remanescente de Floresta Estacional Decidual. A avaliação foi realizada em 70 subparcelas, aleatorizadas em 14 parcelas, dentro de 4 faixas distribuídas sistematicamente, na área. A chuva de sementes foi estudada em 70 coletores de 1 m x 1 m, cujo material era coletado mensalmente para avaliação, no curso de um ano. No banco de sementes do solo foram coletados 70 amostras, a partir de um gabarito de ferro (25 x 25 cm), que colocado sob a superfície do solo permitia a padronização da área para coleta em 5 cm de profundidade. O material coletado foi levado para o Laboratório de Silvicultura do Departamento de Ciência Florestais da Universidade Federal de Santa Maria, onde foi avaliado durante 7 meses. O banco de plântulas foi avaliado em 70 unidades amostrais de 2 x 2 m, onde identificaram-se e mediram-se todos os indivíduos com h ≥ 30 cm e DAP < 1 cm. A regeneração natural estabelecida foi avaliada em 70 unidades amostrais de 5 x 5 m. Nestas, identificaram-se e mediram-se todos os indivíduos com 1cm ≤ DAP < 5 cm. Os mecanismos de regeneração foram analisados em agrupamentos, formados na vegetação adulta. Na chuva de sementes, observou-se a presença de 73 espécies, principalmente, arbóreas. O banco de sementes do solo teve predomínio de espécies herbáceas, além de arbóreas e arbustivas, espécies pioneiras e secundárias iniciais. No banco de plântulas observou-se a presença de espécies heliófilas e eciófilas, enquanto na regeneração natural estabelecida foi verificado o predomínio de espécies de sombra. O banco de sementes do solo e a regeneração natural estabelecida apresentaram comportamento diferente para o grupo 1 e 2 da vegetação adulta, enquanto a chuva de sementes e banco de plântulas apresentaram uniformidade na floresta. As espécies com maior potencialidade para perpetuar no remanescente de floresta estudado foram Gymnanthes concolor, Soroceae bonplandii, Eugenia rostrifolia, Trichilia claussenii, Trichilia elegans e Dasyphylum spinescens, sendo indicadas para enriquecimento. As espécies com maior restrição, foram Cordia tricotoma, Myrocarpus frondosus, Cupania vernalis, Nectandra megapotamica, Luehea divaricata, Sebastiania commersoniana e Syagrus rommanzoffiana, dependendo de tratamentos silviculturais na floresta para garantir sua perpetuação. As espécies indicadoras dos agrupamentos, na vegetação adulta, têm a chuva de sementes e banco de plântulas como principais mecanismos de conservação das espécies no remanescente.
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Ceconi, Denise Ester. "Diagnóstico e recuperação da mata ciliar da Sanga Lagoão do ouro na microbacia hidrográfica do Vacacaí-Mirim, Santa Maria - RS." Universidade Federal de Santa Maria, 2010. http://repositorio.ufsm.br/handle/1/3322.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorThe intensive and disordered use of the soil has been taking many ecosystems to the degradation, besides the ciliary ones that, in spite of they be considered by the legislation as Permanent Preservation Areas, they have been suffering constant antropic pressures and every time larger, and as consequence occur its degradation. In this wey, the present study has as objective evaluate the antropic pressure impacts on the ciliary forest of an urban-rural tributary on the watershed of the Vacacaímirim, Santa Maria - RS, seeking to diagnose the degradation degree and to indicate a subsequent recovery. The study was accomplished on the ciliary forest of the Lagoão do Ouro stream, tributary of 3th order of the Vacacaí-mirim river. The fountain is located in urban area, traveling several towns, the Campus of UFSM, besides an extensive rural area. The predominant soils are classified as: Argissolos Bruno-Acinzentados, Vermelho-Amarelos and Vermelhos , besides Planossolos Háplicos , being these of low natural fertility and quite susceptible to water erosion. Studies of surveying of the degradation were accomplished, in 12 sampling plots of 300 m2 each demarcated along of the margin of the Lagoão do Ouro stream, with the collection of the following information: species floristic surveying of natural occurrence and its regeneration potential, presence of exotic species, evaluation of the bank of soil seeds in two collection times, soil use, soil covering on surface level and by the canopy of the trees and surveying of the erosion (current and potential). The main soil chemical properties (analysis completes of routine) and physics (density, porosity, texture and structure) were appraised also, in each one of the sampling plots. The correlations of the environmental characteristics and antropics with the current erosion and potential erosive were unfolded in direct and indirect effects. After evaluation diagnostic of the degradation, the experiment of recovery of the ciliary ecosystem was preceded, through the revegetation with native species and natural regeneration, besides the soil bioengineering use for erosion control in the stream margin. The floristic surveying showed there to be degradation of the ciliary forest, evidenced by the low number of native species, for the bad distribution of the species in the different strata and for the great presence of exotic species. Just the species that presented larger frequency and that appear in the three floristic strata appraised possess potential of natural regeneration. The bank of soil seeds also showed there to be degradation of the ciliary forest, evidenced by the low number of native arboreal species and for the great number of exotic species and herbaceous invaders. Just the native arboreal species observed in the evaluation and that presented larger frequency possesses potential of regeneration natural through bank of soil seeds. There is correlation of the environmental and antropic factors with the erosion of the soil and with the erosive potential. Antropic interventions are necessary to recovery of the ciliary forest of the Lagoão do Ouro stream, in what concerns to the introduction of species that don't possess potential of natural regeneration and to soil bioengineering works in the margins with erosion more accentuated. The native species used in the recovery of the ciliary forest are appropriate for such an objective, presenting mortality percentage inside of acceptable limits and good initial growth. The soil bioengineering is a cheap and efficient technique in the control of the erosion of the margins of water courses. The experimental methodology of recovery, adopted, can be expanded in the Vacacaí-mirim watershed, mainly in the places where the stream margins are in advanced degradation level.
O uso intensivo e desordenado do solo tem levado muitos ecossistemas à degradação, inclusive os ciliares que, apesar de serem considerados pela legislação como Áreas de Preservação Permanente, têm sofrido pressões antrópicas constantes e cada vez maiores, tendo como consequência a sua degradação. Sendo assim, o presente estudo tem como objetivo avaliar os impactos da pressão antrópica sobre a mata ciliar de um tributário urbano-rural na microbacia hidrográfica do Vacacaímirim, Santa Maria - RS, visando diagnosticar seu grau de degradação e indicar uma posterior recuperação. O estudo foi realizado na mata ciliar da Sanga Lagoão do Ouro, tributário de 3ª ordem do rio Vacacaí-mirim. Sua nascente localiza-se em área urbana, percorrendo várias vilas, o Campus da UFSM, além de uma extensa área rural. Os solos predominantes classificam-se como: Argissolos Bruno-Acinzentados, Vermelho-Amarelos e Vermelhos, além de Planossolos Háplicos, sendo estes de baixa fertilidade natural e bastante suscetíveis a erosão hídrica. Foram realizados estudos de levantamento da degradação, em 12 parcelas de 300 m2 cada, demarcadas ao longo da margem da Sanga Lagoão do Ouro, através da coleta das seguintes informações: levantamento florístico de espécies de ocorrência natural e seu potencial de regeneração, presença de espécies exóticas, avaliação do banco de sementes do solo em duas épocas de coleta, uso do solo, cobertura do solo em nível de superfície e de copada e levantamento da erosão (atual e potencial). Foram também avaliadas as principais propriedades químicas (análise completa de rotina) e físicas (densidade, porosidade, textura e estrutura) do solo, em cada uma das parcelas. As correlações das características ambientais e antrópicas com a erosão atual e potencial erosivo foram desdobradas em efeitos diretos e indiretos. Após avaliação diagnóstica da degradação, procedeu-se com experimento de recuperação do ecossistema ciliar, através da revegetação com espécies nativas e regeneração natural, além do uso de bioengenharia de solos para controle da erosão na margem da sanga. O levantamento florístico mostrou haver degradação da mata ciliar, evidenciada pelo baixo número de espécies nativas, pela má distribuição das espécies nos diferentes estratos e pela grande presença de espécies exóticas. Possuem potencial de regeneração natural apenas as espécies que apresentaram maior frequência e que aparecem nos três estratos florísticos levantados. O banco de sementes do solo também mostrou haver degradação da mata ciliar, evidenciada pelo baixo número de espécies arbóreas nativas e pelo grande número de espécies exóticas e herbáceas invasoras. Possuem potencial de regeneração natural via banco de sementes do solo apenas as espécies arbóreas nativas observadas na avaliação e que apresentaram maior frequência. Há correlação dos fatores ambientais e antrópicos com a erosão do solo e com o potencial erosivo. São necessárias intervenções antrópicas na recuperação da mata ciliar da Sanga Lagoão do Ouro, no que concerne à introdução de espécies que não possuem potencial de regeneração natural e a obras de bioengenharia de solos nas margens com erosão mais acentuada. As espécies nativas usadas na recuperação da mata ciliar são adequadas para tal objetivo, apresentando porcentagem de mortalidade dentro de limites aceitáveis e bom crescimento inicial. A bioengenharia de solo é uma técnica barata e eficiente no controle da erosão das margens de cursos d água. A metodologia experimental de recuperação adotada pode ser expandida na microbacia hidrográfica do Vacacaí-mirim, principalmente nos locais onde as margens da sanga se encontram em estágio avançado de degradação.
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Overduin, P. P. "Soil moisture and soil water solutes during freeze-back at Lake Levinson-Lessing, Taymyr Peninsula, Siberia." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ27369.pdf.
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Gallagher, Robert Sean. "Ecophysiological aspects of phytochrome-mediated germination in soil seed banks /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487933648650464.
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Fleury, Marina Huete. "Interações ecológicas entre plantas e animais: implicações para a conservação e restauração de uma ilha pluvial Atlântica." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/91/91131/tde-26062009-160403/.
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Os ecossistemas de ilhas, continentais ou oceânicas, são considerados os mais sensíveis à perturbação humana. A maioria das ilhas costeiras do Brasil sofreu fortes alterações na fauna e flora silvestre. A Ilha Anchieta (Ubatuba, SP) é uma Área Protegida com um longo histórico de perturbação, tendo sido amplamente desmatada no passado e sofrido a introdução de animais. Sabe-se que a fauna possui um papel chave na composição e estrutura da comunidade vegetal, favorecendo algumas espécies e prejudicando outras. Sendo assim, a perda ou alteração dos processos de interações entre animais e plantas afetam na estrutura e composição de espécies. Este estudo analisa as interações antagônicas entre planta e animais como possíveis fatores limitantes no processo de regeneração natural em três ambientes com distintos estágios sucessionais presentes na Ilha Anchieta: campo aberto (CA) e florestas ombrófilas rala (FOR) e densa (FOD). Para isso foram testados nos três ambientes os processos pós-dispersão de sementes: a predação de sementes pós-dispersas, a germinação do banco de sementes e a herbivoria. A predação de sementes apresentou forte efeito espacial (FOD>FOR>CA) e sazonal, com maiores proporções de predação de sementes no período de escassez de alimento (estação seca). Quantitativamente o banco de sementes não representa um fator limitante, porém foi composto por uma baixa diversidade de espécies lenhosas. A capacidade de germinação do banco de sementes do solo foi similar entre os ambientes florestais apresentando menor emersão de plântulas no campo aberto, provavelmente associado ao intenso escoamento superficial no local. Adicionalmente, a mortalidade de juvenis transplantados foi de 72,27%, sendo superior nas parcelas abertas aos vertebrados para todas as espécies em todos os ambientes, demonstrando um forte efeito negativo dos herbívoros vertebrados na comunidade vegetal. Sendo assim, foram detectados distintos gargalos atuando simultaneamente na regeneração natural nos três ambientes da Ilha Anchieta, sendo necessário o estabelecimento de práticas de manejo visando minimizar os efeitos abióticos no campo aberto e floresta ombrófila rala, favorecendo as interações mutualísticas e inibindo a atividade de animais antagônicos nas florestas ombrófilas rala e densa, acelerando assim o processo de regeneração natural na Ilha Anchieta. Considerar simultaneamente os obstáculos no processo de regeneração nos auxiliará a traçar práticas de restauração e recuperação de áreas degradadas mais efetivas e viáveis economicamente.Island ecosystems, either continental or oceanic, are considered the most sensible to anthropogenic influences. Most Brazilian coastal islands have their original fauna and flora composition altered. The Anchieta Island (southeast Brazil) is a Protected Area that suffered deforestation and introduction of alien species. It is known that the fauna plays a key role in composing and structuring the vegetal community, favoring some species and harming others. Thus, the loss or change of animal-plant interactions affects the framework and composition of species. We simultaneously analyzed the antagonistic animal-plant interactions as possible limiting factors in the natural regeneration on tree successional stages of the Anchieta Island: the old fields (OF), the early secondary forest (ESF) and old growth forest (OGF). Therefore, in each habitat we are evaluating post-dispersal seed predation processes: post-dispersal seed predation, soil seed bank, and the herbivory. We found spatial (OGF>ESF>OF) and temporal effects on seed predation, with highest rates on dry season. Quantitatively, soil seed bank did not represent a limiting factor; but qualitatively, it was composed by few woody species. Our data pointed to the absence of a viable soil seed bank in the OF, probably due to an intense runoff. The forested habitats presented similar soil bank. Moreover, the total mortality of saplings was 72.27%, being higher on the unfenced treatment for all species and in all habitats, showing a very strong negative effect of vertebrate herbivores on the vegetal community. Therefore, we are detecting distinct bottlenecks acting simultaneously in the natural regeneration process in all of the successional stages of the Anchieta Island. Our results showed that management actions are required, aiming to both minimize the abiotic effects on the old fields and in the early secondary forest and to favor the mutual interactions and inhibit the activity of antagonic animals in the old growth and early secondary forests, accelerating, this way, the natural regeneration process of the Anchieta Island. Considering simultaneously the obstacles in the regeneration process will help to define restoration and recuperation procedures of degraded areas more effective and affordable.
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Ouellette, Jeffrey D. "Topics in Remote Sensing of Soil Moisture Using L-Band Radar." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437587673.
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Park, Kee Choon. "Enzymatic activity, microbial diversity, and weed seed banks in soils receiving different organic amendments and the biological fertilizer EM(tm) /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p3164535.
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Thesis (Ph.D.)--University of Missouri-Columbia, 2004.(tm) after EM in title is for Trademark symbol. Typescript. Vita. Includes bibliographical references (leaves 120-142). Also available on the Internet.
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Dimitrov, Marin [Verfasser]. "Interpretation of L-band brightness temperatures of differently tilled bare soil plots / Marin Dimitrov." Bonn : Universitäts- und Landesbibliothek Bonn, 2015. http://d-nb.info/1080591672/34.
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Ben, Khadhra Kais. "Surface Parameter Estimation using Bistatic Polarimetric X-band Measurements." Doctoral thesis, Universitätsbibliothek Chemnitz, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200801439.
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To date only very few bistatic measurements (airborne or in controlled laboratories) have been reported. Therefore most of the current remote sensing methods are still focused on monostatic (backscatter) measurements. These methods, based on theoretical, empirical or semi-empirical models, enable the estimation of soil roughness and the soil humidity (dielectric constant). For the bistatic case only theoretical methods have been developed and tested with monostatic data. Hence, there still remains a vital need to gain of experience and knowledge about bistatic methods and data. The main purpose of this thesis is to estimate the soil moisture and the soil roughness by using full polarimetric bistatic measurements. In the experimental part, bistatic X-band measurements, which have been recorded in the Bistatic Measurement Facility (BMF) at the DLR Oberpfaffenhofen, Microwaves and Radar Institute, will be presented. The bistatic measurement sets are composed of soils with different statistical roughness and different moistures controlled by a TDR (Time Domain Reflectivity) system. The BMF has been calibrated using the Isolated Antenna Calibration Technique (IACT). The validation of the calibration was achieved by measuring the reflectivity of fresh water. In the second part, bistatic surface scattering analyses of the calibrated data set were discussed. Then, the specular algorithm was used to estimate the soil moisture of two surface roughnesses (rough and smooth) has been reported. A new technique using the coherent term of the Integral Equation Method (IEM) to estimate the soil roughness was presented. Also, the sensitivity of phase and reflectivity with regard to moisture variation in the specular direction was evaluated. Finally, the first results and validations of bistatic radar polarimetry for the specular case of surface scattering have been introducedAktuell sind nur sehr wenige Messungen mit bistatischem Radar durchgeführt worden, sei es von Flugzeuggetragenen Systemen oder durch spezielle Aufbauten im Labor. Deshalb basieren die meisten der bekannten Methoden zur Fernerkundung mit Radar auf monostatis-chen Messungen der Rückstreuung des Radarsignals. Diese Methoden, die auf theoretischen, empirischen oder halb-empirischen Modellen basieren, ermöglichen die Schätzung der Oberfächenrauhigkeit und die Bodenfeuchtigkeit (Dielektrizitätskonstante). Im bistatischen Fall wurden bisher nur theoretische Modelle entworfen, die mittels monostatischer Messungen getestet wurden. Aus diesem Grund ist es von großer Bedeutung, Erfahrung und Wissen über die physikalischen Effekte in bistatischen Konfigurationen zu sammeln. Das Hauptziel der vorliegenden Dissertation ist es, anhand vollpolarimetrischer, bistatischer Radarmessungen die Oberfächenrauhigkeit und Bodenfeuchtigkeit zu bestimmen. Im experimentellen Teil der Arbeit werden die Ergebnisse bistatischer Messungen präsentiert, die in der Bistatic Measurement Facility (BMF) des DLR Oberpfaffenhofen aufgenommen wurden. Die Datensätze umfassen Messungen von Böden unterschiedlicher statistischer Rauhigkeit und Feuchtigkeit, die mittels eines Time Domain Reflectivity (TDR) Systems bestimmt werden. Zur Kalibration des BMF wurde die Isolated Antenna Calibration Technique (IACT) verwendet und anhand der Messung der Reflektivität von Wasser überprüft. Im zweiten Teil der vorliegenden Arbeit wird anhand der kalibrierten Daten eine Analyse der Oberflächenstreuung in bistatischen Konfigurationen vorgenommen. Im Anschluss daran wird mittels des Specular Algorithm eine Schätzung der Bodenfeuchte zweier Proben unter- schiedlicher Rauhigkeit (rau und fein) durchgeführt. Ein neues Verfahren zur Schätzung der Oberfächenrauhigkeit, das auf dem kohärenten Term der Integral Equation Method (IEM) basiert, wurde eingeführt. Daneben wird die Empfindlichkeit der Phase sowie der Reflektivität des vorwärtsgestreuten Signals gegenüber Veränderungen der Bodenfeuchtigkeit analysiert. Schließlich werden erste Ergebnisse und Validierungen bistatischer Radarpolarimetrie für den Fall der Vorwärtsstreuung präsentiert
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Jasson, René. "Management of Acacia species seed banks in the Table Mountain National Park, Cape Peninsula, South Africa /." Link to the online version, 2005. http://hdl.handle.net/10019/1059.
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Thomas, Paul B., University of Western Sydney, of Science Technology and Environment College, and School of Environment and Agriculture. "Effects of factors associated with the season of a fire on germination of species forming soil seedbanks in the fire-prone Hawkesbury sandstone region of Sydney, Australia." THESIS_CSTE_EAG_Thomas_P.xml, 2004. http://handle.uws.edu.au:8081/1959.7/697.
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Fire is a recurrent disturbance that removes above ground vegetation in many locations throughout the world, including the Sydney region. Many species in fire-prone locations, and most species in the Sydney region, form soil seedbanks and regenerate through post-fire germination. However, a germination response is determined by the fire regime acting as a selective pressure over a sufficient period of time, rather than a single fire. The components of the fire-regime are intensity, season, type and frequency. The natural fire regime is dominated by warm-season fire, but management burning is conducted in cooler seasons. Cool season burning produces lower levels of germination than warm season fires in a number of locations with Mediterranean-type climate, but the effects of cool season burning on species composition in the relatively aseasonal Sydney region is unknown. An experimental approach was adopted to address this lack of knowledge. Fire can be simulated using heat shock and smoke (fire cues), and the seasonal factors of temperature and water availability can be reproduced in the laboratory. I have investigated the effect of various combinations of heat shock and smoke, of various pre-and post-fire cue temperatures, of prefire cue hydration status, of various post-fire cue water availabilities, and of accelerated aging before application of fire cues on germination of a number of species forming soil seedbanks in the Sydney region. A degree of primary dormancy was overcome in most species by the combination of heat shock and smoke in the current investigation. Fire intensity is expected to influence germination, as germination of most species was increased by the combination of heat shock and smoke within a narrow heat shock range.The interaction between ambient temperature and the level of heat shock may affect germination. Soil water content, and thus seed moisture content at the time of a fire may interact with the level of heat shock to affect both germination and survival of a seed. The age of a seed may also affect its germination response to fire. The above factors are predicted to affect the germination of species differently, and thus season of fire is expected to alter species composition. Such predictions can be readily field-testedDoctor of Philosophy (PhD)
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Carmona, Ricardo. "Factors affecting the efficacy of dormancy-relieving chemicals on weed seed banks in the soil." Thesis, University of Reading, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316108.
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Ben, Khadhra Kais. "Surface Parameter Estimation using Bistatic Polarimetric X-band Measurements." Doctoral thesis, Deutsches Zentrum für Luft- und Raumfahrt e.V. in der Helmholtz-Gemeinschaft, 2007. https://monarch.qucosa.de/id/qucosa%3A18987.
Full textAbstract:
To date only very few bistatic measurements (airborne or in controlled laboratories) have been reported. Therefore most of the current remote sensing methods are still focused on monostatic (backscatter) measurements. These methods, based on theoretical, empirical or semi-empirical models, enable the estimation of soil roughness and the soil humidity (dielectric constant). For the bistatic case only theoretical methods have been developed and tested with monostatic data. Hence, there still remains a vital need to gain of experience and knowledge about bistatic methods and data. The main purpose of this thesis is to estimate the soil moisture and the soil roughness by using full polarimetric bistatic measurements. In the experimental part, bistatic X-band measurements, which have been recorded in the Bistatic Measurement Facility (BMF) at the DLR Oberpfaffenhofen, Microwaves and Radar Institute, will be presented. The bistatic measurement sets are composed of soils with different statistical roughness and different moistures controlled by a TDR (Time Domain Reflectivity) system. The BMF has been calibrated using the Isolated Antenna Calibration Technique (IACT). The validation of the calibration was achieved by measuring the reflectivity of fresh water. In the second part, bistatic surface scattering analyses of the calibrated data set were discussed. Then, the specular algorithm was used to estimate the soil moisture of two surface roughnesses (rough and smooth) has been reported. A new technique using the coherent term of the Integral Equation Method (IEM) to estimate the soil roughness was presented. Also, the sensitivity of phase and reflectivity with regard to moisture variation in the specular direction was evaluated. Finally, the first results and validations of bistatic radar polarimetry for the specular case of surface scattering have been introduced.Aktuell sind nur sehr wenige Messungen mit bistatischem Radar durchgeführt worden, sei es von Flugzeuggetragenen Systemen oder durch spezielle Aufbauten im Labor. Deshalb basieren die meisten der bekannten Methoden zur Fernerkundung mit Radar auf monostatis-chen Messungen der Rückstreuung des Radarsignals. Diese Methoden, die auf theoretischen, empirischen oder halb-empirischen Modellen basieren, ermöglichen die Schätzung der Oberfächenrauhigkeit und die Bodenfeuchtigkeit (Dielektrizitätskonstante). Im bistatischen Fall wurden bisher nur theoretische Modelle entworfen, die mittels monostatischer Messungen getestet wurden. Aus diesem Grund ist es von großer Bedeutung, Erfahrung und Wissen über die physikalischen Effekte in bistatischen Konfigurationen zu sammeln. Das Hauptziel der vorliegenden Dissertation ist es, anhand vollpolarimetrischer, bistatischer Radarmessungen die Oberfächenrauhigkeit und Bodenfeuchtigkeit zu bestimmen. Im experimentellen Teil der Arbeit werden die Ergebnisse bistatischer Messungen präsentiert, die in der Bistatic Measurement Facility (BMF) des DLR Oberpfaffenhofen aufgenommen wurden. Die Datensätze umfassen Messungen von Böden unterschiedlicher statistischer Rauhigkeit und Feuchtigkeit, die mittels eines Time Domain Reflectivity (TDR) Systems bestimmt werden. Zur Kalibration des BMF wurde die Isolated Antenna Calibration Technique (IACT) verwendet und anhand der Messung der Reflektivität von Wasser überprüft. Im zweiten Teil der vorliegenden Arbeit wird anhand der kalibrierten Daten eine Analyse der Oberflächenstreuung in bistatischen Konfigurationen vorgenommen. Im Anschluss daran wird mittels des Specular Algorithm eine Schätzung der Bodenfeuchte zweier Proben unter- schiedlicher Rauhigkeit (rau und fein) durchgeführt. Ein neues Verfahren zur Schätzung der Oberfächenrauhigkeit, das auf dem kohärenten Term der Integral Equation Method (IEM) basiert, wurde eingeführt. Daneben wird die Empfindlichkeit der Phase sowie der Reflektivität des vorwärtsgestreuten Signals gegenüber Veränderungen der Bodenfeuchtigkeit analysiert. Schließlich werden erste Ergebnisse und Validierungen bistatischer Radarpolarimetrie für den Fall der Vorwärtsstreuung präsentiert.
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Morel, Jean-Claude. "Appareil de compression biaxiale et sols renforcés." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10017.
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La mise au point d'un appareil de compression biaxiale, appele biaxial, permettant d'ecraser des materiaux granulaires en deformations planes, sous confinement, a permis de faire l'etude de deux types de materiaux renforces. Pour le micro-renforcement, il s'agit d'un sable renforce par des microgrilles (elements discrets) melangees d'une maniere aleatoire au sable d'hostun rf. Une modelisation de la cinematique de bande de cisaillement est proposee et validee par des essais de cisaillement direct avec une grande boite de cisaillement. L'etude au biaxial a permis de montrer l'influence de la concentration massique en renforcement. L'utilisation de la methode de stereophotogrammetrie a permis de caracteriser la localisation en bande de cisaillement qui intervient a peu pres dans les memes conditions que dans le sable seul, mais qui ne se traduit pas par une chute des contraintes globales dans le materiau, au contraire il y a une augmentation continue de celles-ci jusqu'a la fin de nos essais: les microgrilles sont mobilisees par les bandes de cisaillement. Une etude au triaxial de revolution, sous sollicitations cycliques, montre que le sable renforce presente des tassements plus faibles et une meilleure resistance que le sable seul ; le comportement post cycle du materiau renforce est modifie. Pour le macro-renforcement, le meme sable, renforce par des nappes de geotextiles, non tissees, avec differentes orientations par rapport a l'axe des contraintes principales majeures, est teste au biaxial. La disposition horizontale des nappes est celle qui apporte le plus grand renforcement au materiau alors que des inclinaisons proches de l'inclinaison des plans de glissement du sable seul, diminue la resistance du materiau composite, par rapport au sable seul. Les deformations locales au sein de l'echantillon sont analysees ainsi que les mesures des deplacements relatifs des nappes par rapport au sable grace a une adaptation de la methode stereophotogrammetrique
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Heinken, Thilo, Marcus Schmidt, Goddert von Oheimb, Wolf-Ulrich Kriebitzsch, and Hermann Ellenberg. "Soil seed banks near rubbing trees indicate dispersal of plant species into forests by wild boar." Universität Potsdam, 2006. http://opus.kobv.de/ubp/volltexte/2010/4647/.
Full textAbstract:
Current knowledge about processes that generate long-distance dispersal of plants is still limited despite its importance for persistence of populations and colonization of new potential habitats. Today wild large mammals are presumed to be important vectors for long-distance transport of diaspores within and between European temperate forest patches, and in particular wild boars recently came into focus. Here we use a specific habit of wild boar, i.e. wallowing in mud and subsequent rubbing against trees, to evaluate epizoic dispersal of vascular plant diaspores. We present soil seed bank data from 27 rubbing trees versus 27 control trees from seven forest areas in Germany. The mean number of viable seeds and the plant species number were higher in soil samples near rubbing trees compared with control trees. Ten of the 20 most frequent species were more frequent, and many species exclusively appeared in the soil samples near rubbing trees. The large number of plant species and seeds – approximated > 1000 per tree – in the soils near rubbing trees is difficult to explain unless the majority were dispersed by wild boar. Hooked and bristly diaspores, i.e. those adapted to epizoochory, were more frequent, above that many species with unspecialised diaspores occurred exclusively near rubbing trees. Different to plant species closely tied to forest species which occur both in forest and open vegetation, and non-forest species were more frequent near rubbing trees compared with controls. These findings are consistent with previous studies on diaspore loads in the coats and hooves of shot wild boars. However, our method allows to identify the transport of diaspores from the open landscape into forest stands where they might especially emerge after disturbance, and a clustered distribution of epizoochorically dispersed seeds. Moreover, accumulation of seeds of wetness indicators near rubbing trees demonstrates directed dispersal of plant species inhabiting wet places between remote wallows.Das aktuelle Wissen über Prozesse, die zur Fernausbreitung von Pflanzen führen, ist trotz ihrer Bedeutung für das Überleben von Populationen und die Besiedlung neuer potenzieller Habitate noch immer sehr begrenzt. Wildlebende Großsäuger sind heutzutage vermutlich wichtige Vektoren für den Ferntransport von Diasporen innerhalb und zwischen den einzelnen Waldflächen in Mitteleuropa, und speziell das Wildschwein (Sus scrofa L.) spielt dabei offenbar eine herausragende Rolle. Wir nutzen hier ein spezifisches Verhalten des Wildschweins – Suhlen im Schlamm und nachfolgendes Scheuern an sogenannten Malbäumen – um die epizoochore Ausbreitung von Gefäßpflanzen-Diasporen einzuschätzen. Dargestellt werden die Ergebnisse von Samenbank-Untersuchungen von 27 Malbäumen im Vergleich zu 27 Kontrollbäumen aus sieben Waldgebieten in Deutschland. Sowohl die mittlere Zahl lebensfähiger Samen als auch die Artenzahl waren höher in Bodenproben neben Malbäumen. Zehn der 20 in der Samenbank verbreitetsten Pflanzenarten hatten hier ihren Schwerpunkt, und viele Arten kamen ausschließlich in den neben Malbäumen gewonnenen Proben vor. Die große Zahl von Pflanzenarten und Samen – zumindest > 1000 pro Baum – im Boden an Malbäumen lässt sich nur durch die Aktivität der Wildschweine erklären. Mit Haken oder Borsten ausgestattete, d.h. an Epizoochorie angepasste Diasporen waren häufiger, aber auch viele Arten mit unspezialisierten Diasporen kamen ausschließlich in der Samenbank bei Malbäumen vor. Anders als weitgehend an Wald gebundene Pflanzenarten waren solche, die sowohl im Wald und im Offenland vorkommen, sowie nicht im Wald vorkommende Arten häufiger neben Malbäumen als neben Kontrollbäumen. Diese Befunde stimmen mit denen früherer Untersuchungen von Diasporenladungen im Fell und in den Hufen geschossener Wildschweine überein. Unsere Methode erlaubt darüber hinaus aber die Identifizierung des Diasporentransports aus dem Offenland in die Waldbestände, wo sie insbesondere nach Störungen keimen dürften, sowie einer ungleichmäßigen Verteilung epizoochor ausgebreiteter Diasporen. Außerdem zeigt die Akkumulation von Samen von Nässezeigern neben den Malbäumen eine gezielte Ausbreitung nasse Standorte bewohnender Pflanzenarten zwischen entfernt gelegenen Suhlen.