This dissertation focuses on two portions of the Clovis lithic assemblage recovered from Excavation Area 8 at the Gault site (41BL323) located in central Texas. Gault is a quarry-camp visited by hunter-gatherer groups for at least 13,000 years, with Paleoindian, Archaic, and Late Prehistoric occupations. Freshwater seep springs, a diverse array of floral and faunal resources, and an abundant outcrop of high-quality toolstone at the site created an ideal location for people who lived a mobile hunting-andgathering way of life. The site is currently the only locale with two stratigraphically separate Clovis components-a lower geologic unit designated 3a and an upper unit designated 3b. Both are represented in Excavation Area 8 where, in the spring of 2000, Texas A&M University (TAMU) excavated 22 1-m2 contiguous units. For this research, 3375 complete flakes were analyzed individually to characterize Clovis debitage as represented at Excavation Area 8 and to establish if there are technological differences between the debitage assemblages recovered from Units 3a and 3b. The two Clovis components are quite similar from a technological standpoint. Minor differences appear to be related to site formation processes and intensity of site use. The second objective was to determine if Clovis debitage has diagnostic technological traits that allow confident assignment to the Clovis era. To test whether Clovis debitage is distinctive, it was compared to debitage recovered from later cultural components at the site. No evidence of a true blade technology was observed in the post- Clovis Paleoindian or Early Archaic debitage assemblages, although biface manufacture continued through time. Technologically, few differences were observed between the Clovis, post-Clovis Paleoindian, and Early Archaic debitage related to biface reduction. While overshot flakes may be diagnostic of Clovis biface technology, biface thinning flakes and other non-distinctive debitage showed few differences between components. During debitage analysis pieces were selected in an attempt to identify edgemodified tools. Low- and high-power usewear analysis was employed to make determinations concerning the cultural modification or use of flakes. This study concluded post-depositional damage affected most of the collection and there was minimal usewear-or minimal observable usewear-on flakes. Taphonomic processes interfered to a great extent with drawing firm inferences on tool use and possibly hindered the identification of tools. Of the 3375 pieces of Clovis debitage originally analyzed, 26 specimens were classified as tools based mainly on invasive, patterned flaking with less reliance on microscopic use indicators. Of these, inference of use was assigned to nine tools.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2006. / Härtill 4 uppsatser.

Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / The integrated crop livestock systems are an important alternative to diversify production, increasing efficiency and autonomy of production systems. However, inadequate management of this stocking system promotes numerous negative consequences, especially on structural properties dependent on soil pore space, which can be limiting for both the development of plants and for system sustainability. However, there are indications that well-managed grazing systems can generate benefits to soil structure, due to the action of the plant root system that is positively stimulated after grazing. The hypothesis of this study is that moderate grazing promotes improvements in soil structural quality in this system. The objective of the study was to evaluate how different grazing levels affect selected soil physical and mechanical properties. The experiment consists of a 15-years old integrated crop livestock system, managed with (Glycine max) in the summer and (Avena strigosa, Schreb) + (Lolium multiflorum Lam.) in winter intended for continuous grazing of beef cattle. The treatments consisted of different grazing intensities, determined by sward height, namely: 0.10 m (heavy grazing), 0.30 m (moderate grazing) and an area as control (without grazing) in an experimental design of randomized blocks with three replications. Preserved-structure samples (volumetric rings) were collected in the 0-0.05, 0.05-0.10, and 0.10-0.20 m layers at the end of each cycle, soybeans and pasture, April and November 2015, respectively. Soil bulk density (Ds), total porosity (Pt), macroporosity (Ma), microporosity (Mi), air permeability (Ka), saturated hydraulic conductivity soil (Ks), preconsolidation pressure (σp), compression ratio (Ic), decompression coefficient (Cd) and soil cyclic loading test were determined. The results indicate that grazing increases the state of compaction of the soil surface, causing negative effects of the physical and mechanical properties. However, there is a mitigation of the effects if evaluated after the summer crop. / Sistemas Integrados de Produção Agropecuária (SIPA) são uma alternativa importante à diversificação da produção, aumentando a eficiência e a autonomia dos sistemas de produção. Porém, o manejo inadequado da lotação animal nesse sistema promove inúmeras consequências negativas, sobretudo às propriedades estruturais do solo dependentes do espaço poroso, as quais podem ser limitantes tanto para o desenvolvimento de plantas quanto para a sustentabilidade do sistema. Contudo, existem indícios de que o pastejo animal bem manejado pode gerar benefícios à estruturação do solo, devido à ação do sistema radicular das plantas de cobertura que é estimulado de forma positiva após o pastejo. Dentro desse contexto, a hipótese deste estudo é de que pastejo moderado promove melhorias na qualidade estrutural no solo em SIPA. O objetivo do estudo foi avaliar como diferentes níveis de pastejo afetam as propriedades físicas e mecânicas do solo. O experimento consistiu em um SIPA com 15 anos de condução, manejado com soja (Glycine max) no verão e aveia preta (Avena strigosa, Schreb) + azevém (Lolium multiflorum, Lam.) no inverno destinadas ao pastejo contínuo de bovinos de corte. Os tratamentos consistiram em diferentes intensidades de pastejo, determinados pela altura da pastagem, sendo: 0,10 m (pastejo intenso), 0,30 m (pastejo moderado) e uma área como testemunha (sem pastejo) em um delineamento experimental de blocos ao acaso com três repetições. Foi realizada a coleta de amostras de estrutura preservada (anéis volumétricos), nas camadas de 0-0,05, 0,05-0,10 e 0,10-0,20 m ao término de cada ciclo, soja e pastagem, abril e novembro de 2015, respectivamente. Foram determinados a densidade do solo (Ds), a porosidade total (Pt), a macroporosidade (Ma), a microporosidade(Mi), a permeabilidade ao ar (Ka), a condutividade hidráulica de solo saturado (Ks), a pressão de preconsolidação (σp), o índice de compressão (Ic), o coeficiente de descompressão (Cd) e a compressibilidade cíclica do solo. Os resultados indicam que o pastejo aumenta o estado de compactação da superfície do solo, causando efeitos negativos nas propriedades físicas e mecânicas. Todavia, há uma atenuação destes efeitos se avaliados após o cultivo de verão.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / With the advance of urbanization towards the coast, this ecosystems have been passing throught anthropic interventions by its intention to offer habitation, turism and recreation. However, this interferences can give birth to changes over the biodiversity of various ecosystems. In face of this situation, this research has, as its objectives: to analyse the impacts provoked by the various levels of urbanization over the population of Ocypode quadrata Fabricius, 1787 (Crustacea: Decapoda, Ocypodidae) and Bledius Leach, 1819 (Insecta: Coleoptera, Staphylinida) along 14 sandy beaches in Sergipe's coastline (Chapter. 1), to appraise the intensity's effect of the recreation (number of visitors) over the O. quadrata e Bledius spp. population at Aruanda's beach (Chapter. 2), also to assess, through experiments with various frequencies of tramplings, the real effect of this activity, diagnosticating the healing power of this population as well (Chapter. 3). Though significant differences have been witnessed in the amount of the crab's burrow's along the 14 beaches, the results did not show precise evidences that corroborate with the hypothesis that the high degree of urbanization leads to a reduction over the abundance of this population. As expected, the number of the visitors was significantly bigger in the "pertubed" sector in all of the months of the research at Aruanda's beach. Nevertheless responding in actual distinct cases, both the O. quadrata crab and coleoptera Bledius pp. has suffered negative effects envolving the tramplings. The numbers of the quantity of O. quadrata 's burrows were significantly lower in the “perturbed” sector before January/2015 carnival, whilst for the Bledius spp., lower numbers were witnessed for the “perturbed” sector during February/2015 and after the carnival period, March/2015 (Chapter 2). Regarding the experiment which took place at Refugio's beach, a relevant reduction in the amount of burrows was verified through the period of the experiment, to both O. quadrata and Bledius spp. The retreat on the numbers of the burrows occured over the "High Frequency" and "Average Frequency" sector. As for the Bledius spp. population, a relevant decline occured in all of the parcels. The recovery effect was observed more clearly to the beetles that for the burrows of crabs. The results obtained in the current research, suggest the investigated populations as ideal indicators for anthropic impactations in beaches. In addition, we propose more experimental researches, to accomplish a clear effect of the various anthropic activities over the benthic populations. / Com o avanço da urbanização em direção às praias, esses ecossistemas têm passado por intervenções antrópicas que tem como intuito, oferecer moradia, turismo e lazer. Entretanto, essas intervenções podem provocar alterações na biodiversidade desses ecossistemas. Mediante essa situação, os estudos tiveram como objetivos, avaliar os impactos provocados pelos diferentes graus de urbanização nas populações de O. quadrata Fabricius, 1787 (Crustacea: Decapoda, Ocypodidae) e Bledius Leach, 1819 (Insecta: Coleoptera, Staphylinidae) ao longo de 14 praias arenosas do litoral de Sergipe (Capítulo 1), avaliar o efeito da intensidade do uso recreativo (número de frequentadores) sobre as populações de O. quadrata e Bledius spp. na praia de Aruanda (Capítulo 2), assim como avaliar através de experimentos com diferentes frequências de pisoteio, o efeito real dessa atividade sobre as populações de Bledius spp. e O. quadrata, diagnosticando também o efeito recuperação dessas populações (Capítulo 3). Embora tenham sido observadas diferenças significativas na abundância de tocas de O. quadrata e Bledius spp. entre as 14 praias analisadas, os resultados obtidos não apresentaram evidências concisas que corroborem com a hipótese de que o elevado grau de urbanização acarreta em uma redução na abundância dessas populações (Capítulo 1). Como esperado, o número de frequentadores foi significativamente maior no setor "perturbado" em todos os meses de estudo na praia de Aruanda. Mesmo respondendo em situações distintas, tanto o caranguejo O. quadrata quanto os estafilinídeos Bledius pp. sofreram efeitos negativos em relação ao pisoteio. Valores de abundância de tocas de O. quadrata foram significativamente menores no setor “perturbado” antes do carnaval (Janeiro/2015), enquanto que para a população de Bledius spp. menores valores de abundância foram observados no setor perturbado, durante (Fevereiro/2015) e após (Março/2015) o período de carnaval (Capítulo 2). O experimento realizado na praia do Refúgio mostrou que houve reduções significativas ao longo dos dias de experimento, tanto na abundância de tocas de O. quadrata quanto na de Bledius spp. A redução nos valores de abundância de tocas aconteceu nas parcelas “Alta Frequência” e “Média Frequência”. Já para a população de Bledius spp. houve uma queda significativa na abundância desses estafilinídeos em todas as parcelas analisadas. O efeito recuperação foi observado com mais clareza para os coleópteros que para as tocas dos caranguejos (Capítulo 3). Os resultados obtidos no presente estudo sugerem a utilização das populações investigadas como bons indicadores de impactos antrópicos em praias. Além disso, sugerimos também a realização de mais abordagens experimentais, para que assim possa ficar claro o efeito real das diferentes atividades antrópicas sobre as populações bentônicas.

Made available in DSpace on 2017-07-10T19:25:02Z (GMT). No. of bitstreams: 1 Veruschka Rocha Medeiros Andreolla.pdf: 1722558 bytes, checksum: bb4f5cea73e94834a80a8b228456a12b (MD5) Previous issue date: 2005-08-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objective of this work was to verify the influence of pasture in side of agriculture-cattle integration on the physical characteristics of the ground, to evaluate the influence of these parameters and the staggered of a planter (connecting rod and record of cut) on the grain yield of the soy and to quantify the energy performance of the planter in ground submitted to the trampling of animals. An experiment in Oxissol, situated was become fulfilled in the Santa Maria Farm, Santa Tereza do Oeste - PR, in the period of April of 2003 the April of 2004. The delineation in subdivided parcels "Split Plot" entirely randomized was used. The main treatments had been composed by pasture with the ground humid or wet, pasture with alone dry and without pasture, with a capacity of 26 U.A. ha 1. The secondary treatments had been composites for the mechanisms staggered of the planter (double connecting rod or records for deposition of the seasoning). Each plot with a area 1600 m2 (50 x 32 m) and the subparcels had dimensions of 20 x 8 m, with area of 160 m2. Physical properties of the ground, parameters of performance of the tractor-planter set and grain yield of the soy had been evaluated. The values gotten in the experiments had shown the effect of the cattle trampling in compacting the ground in the layer until the 10 cm initial. The sharp peak in the resistance to the penetration the 5 cm can be indicating that the maximum mobilization of the resistance of the ground occurred at the depth 5 cm. The root of the soy had promoted the decompaction of the ground, showing a trend of return to the initial structural condition of it. The tension-deformation analysis corroborated the results of the assays of compacting in laboratory, as well as the deformation curve revealed consistent with the profiles of resistance to the penetration in the field. The action of the cattle trampling on the ground modified the density conditions and cone index, however was not enough to intervene with the demand of power in the three studied conditions. The planter with staggered of records had exerted minor power and snatch force and the speed of displacement of the set was about 6,4 % greater in relation to the staggered connecting rod. The grain yield of the soy was not modified significantly by the handling systems, but when the mechanism was used connecting rod in the planter, the production of grains bigger when was compared with the planter equipped with staggered of records. / O objetivo deste trabalho foi verificar a influência do pastejo em área de integração lavoura-pecuária sobre as características físicas do solo, avaliar a influência desses parâmetros e dos elementos sulcadores de uma semeadora (haste e disco de corte) sobre a produtividade da soja e quantificar o desempenho energético da semeadora em solo submetido ao pisoteio do gado. Realizou-se um experimento em LATOSSOLO VERMELHO Eutroférrico, situado na Fazenda Santa Maria, em Santa Tereza do Oeste PR, no período de abril de 2003 a abril de 2004. Foi utilizado o delineamento em parcelas subdivididas Split Plot inteiramente casualizado. Os tratamentos principais foram compostos pelo pastejo com o solo úmido ou molhado, pastejo com solo seco e sem pastejo, com uma lotação de 26 U.A. ha 1 (unidade animal por hectare). Os tratamentos secundários foram compostos pelos elementos sulcadores da semeadora (haste ou discos duplo para deposição do adubo). Cada parcela com um total de 1600 m2 (50 x 32 m) e as subparcelas tinham dimensões de 20 x 8 m, com total de 160 m2. Foram avaliadas propriedades físicas do solo, variáveis de desempenho do conjunto trator-semeadora e rendimentos de grãos da soja. Os valores obtidos nos experimentos mostraram o efeito do pisoteio do gado em compactar o solo na camada até os 10 cm iniciais. O pico pronunciado na resistência à penetração a 5 cm pode ser indicador de que a máxima mobilização da resistência do solo ocorreu à profundidade 5 cm. Os sulcadores de haste promoveram a descompactação do solo conciliando assim com o efeito descompactador das raízes da aveia e da soja, mostrando uma tendência de retorno à condição estrutural inicial do mesmo. A análise tensão-deformação corroborou os resultados dos ensaios de compactação em laboratório, assim como a curva de deformação mostrou-se consistente com os perfis de resistência à penetração no campo. A ação do pisoteio do gado sobre o solo alterou as condições de densidade e resistência à penetração, entretanto não foi suficiente para interferir na demanda de potência nas três condições estudadas. A semeadora com sulcadores de discos exigiu menor força de tração e potência e a velocidade de deslocamento do conjunto foi cerca de 6,4 % maior em relação ao sulcador haste. O rendimentos de grãos da soja não foi alterado significativamente pelos sistemas de manejo, mas quando foi utilizado o elemento haste na semeadora, a produção de grãos foi maior quando comparada com a semeadora equipada com sulcadores de discos.

Made available in DSpace on 2017-05-12T14:48:24Z (GMT). No. of bitstreams: 1 Veruschka Rocha Medeiros Andreolla.pdf: 1722558 bytes, checksum: bb4f5cea73e94834a80a8b228456a12b (MD5) Previous issue date: 2005-08-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objective of this work was to verify the influence of pasture in side of agriculture-cattle integration on the physical characteristics of the ground, to evaluate the influence of these parameters and the staggered of a planter (connecting rod and record of cut) on the grain yield of the soy and to quantify the energy performance of the planter in ground submitted to the trampling of animals. An experiment in Oxissol, situated was become fulfilled in the Santa Maria Farm, Santa Tereza do Oeste - PR, in the period of April of 2003 the April of 2004. The delineation in subdivided parcels "Split Plot" entirely randomized was used. The main treatments had been composed by pasture with the ground humid or wet, pasture with alone dry and without pasture, with a capacity of 26 U.A. ha 1. The secondary treatments had been composites for the mechanisms staggered of the planter (double connecting rod or records for deposition of the seasoning). Each plot with a area 1600 m2 (50 x 32 m) and the subparcels had dimensions of 20 x 8 m, with area of 160 m2. Physical properties of the ground, parameters of performance of the tractor-planter set and grain yield of the soy had been evaluated. The values gotten in the experiments had shown the effect of the cattle trampling in compacting the ground in the layer until the 10 cm initial. The sharp peak in the resistance to the penetration the 5 cm can be indicating that the maximum mobilization of the resistance of the ground occurred at the depth 5 cm. The root of the soy had promoted the decompaction of the ground, showing a trend of return to the initial structural condition of it. The tension-deformation analysis corroborated the results of the assays of compacting in laboratory, as well as the deformation curve revealed consistent with the profiles of resistance to the penetration in the field. The action of the cattle trampling on the ground modified the density conditions and cone index, however was not enough to intervene with the demand of power in the three studied conditions. The planter with staggered of records had exerted minor power and snatch force and the speed of displacement of the set was about 6,4 % greater in relation to the staggered connecting rod. The grain yield of the soy was not modified significantly by the handling systems, but when the mechanism was used connecting rod in the planter, the production of grains bigger when was compared with the planter equipped with staggered of records. / O objetivo deste trabalho foi verificar a influência do pastejo em área de integração lavoura-pecuária sobre as características físicas do solo, avaliar a influência desses parâmetros e dos elementos sulcadores de uma semeadora (haste e disco de corte) sobre a produtividade da soja e quantificar o desempenho energético da semeadora em solo submetido ao pisoteio do gado. Realizou-se um experimento em LATOSSOLO VERMELHO Eutroférrico, situado na Fazenda Santa Maria, em Santa Tereza do Oeste PR, no período de abril de 2003 a abril de 2004. Foi utilizado o delineamento em parcelas subdivididas Split Plot inteiramente casualizado. Os tratamentos principais foram compostos pelo pastejo com o solo úmido ou molhado, pastejo com solo seco e sem pastejo, com uma lotação de 26 U.A. ha 1 (unidade animal por hectare). Os tratamentos secundários foram compostos pelos elementos sulcadores da semeadora (haste ou discos duplo para deposição do adubo). Cada parcela com um total de 1600 m2 (50 x 32 m) e as subparcelas tinham dimensões de 20 x 8 m, com total de 160 m2. Foram avaliadas propriedades físicas do solo, variáveis de desempenho do conjunto trator-semeadora e rendimentos de grãos da soja. Os valores obtidos nos experimentos mostraram o efeito do pisoteio do gado em compactar o solo na camada até os 10 cm iniciais. O pico pronunciado na resistência à penetração a 5 cm pode ser indicador de que a máxima mobilização da resistência do solo ocorreu à profundidade 5 cm. Os sulcadores de haste promoveram a descompactação do solo conciliando assim com o efeito descompactador das raízes da aveia e da soja, mostrando uma tendência de retorno à condição estrutural inicial do mesmo. A análise tensão-deformação corroborou os resultados dos ensaios de compactação em laboratório, assim como a curva de deformação mostrou-se consistente com os perfis de resistência à penetração no campo. A ação do pisoteio do gado sobre o solo alterou as condições de densidade e resistência à penetração, entretanto não foi suficiente para interferir na demanda de potência nas três condições estudadas. A semeadora com sulcadores de discos exigiu menor força de tração e potência e a velocidade de deslocamento do conjunto foi cerca de 6,4 % maior em relação ao sulcador haste. O rendimentos de grãos da soja não foi alterado significativamente pelos sistemas de manejo, mas quando foi utilizado o elemento haste na semeadora, a produção de grãos foi maior quando comparada com a semeadora equipada com sulcadores de discos.

published_or_final_version / Geography and Geology / Master / Master of Philosophy

Extensive drought - and elephant-related dieback of Colophospermum mopane and Acacia tortitis, respectively, offered an opportunity for increasing understanding of the causes of drought-related patch dieback, the factors influencing elephant utilization of woody plants, and the response of woody plants to both aforementioned determinants of savanna structure and function. The dendrochronological analysis of both species was undertaken to estimate potential rates of replacement, following extensive mortality. Areas of discrete dieback were compared with adjacent paired areas of 'healthy' vegetation, which revealed, on average, 87% and 13% loss of basal area by mortality, respectively. 'Live' and 'dead' plots did not differ in soil type, topography or mean slope, but differed in vegetation structure, soil surface condition, and soil chemistry. Although there was evidence of self-thinning, neither inter - nor intra-specific competition explained dieback. 'Dead', by comparison with 'live' plots, had changed from functioning as sinks of sediment and water to sources, were less likely to retain water because of a poor soil surface condition, and were predisposed to drought effects because of a greater proportion of fines, and Na concentration. Dieback resulted from insufficient soil water for survival during a drought owing to the development of a dysfunctional landscape during 50 years of livestock ranching. Spatial heterogeneity within a landscape was suggested to enhance woodland resilience to severe droughts by ensuring the survival of plants in run-on sinks or 'drought refuge' sites. Stem sections were removed from 40 multi-stemmed C. mopane trees and prepared for examination under a dissecting microscope. It was impossible to age C. mopane, owing to a hollow and/or dark heartwood. Nevertheless, the distribution of stem diameters suggested a single recruitment event. Fire scars attributed to the last recorded fire in 1948 could explain the trees' multi-stemmed growth form and indicate that most trees of VLNR were > 50 years of age. Growth rings were identified in 29 A. tortilis trees of unknown age, but were not correlated with annual rainfall records. Growth rates varied between trees; mean ring width ranged from 1.4 to 3.5 mm (overall mean 2.4 ± 0.1 mm). A technique was proposed for predicting growth rate from annual rainfall, using selected data, and several factors potentially influencing ring width in semiarid environs were identified. Permanent ground-based transects were located within riparian (n = 16) and Acacia (n = 5) woodlands to monitor elephant utilization. Elephant had not changed the population structure of the woodlands by 2000, but had reduced stem density from 215.6 stems ha -1 (1996) to 84.4 stems ha -I (2000). Acacia tortitis trees in the woodlands had branches removed, were debarked, uprooted and broken. Acacia tortitis trees in the riverine had lower levels of utilization, whilst Acacia nilotica trees were mostly debarked. The method of elephant feeding varies within and between woody species, provided it is within the mechanical constraints of a certain size or species. Elephant behaviour is concluded to depend on spatiotemporal variation of forage abundance/quality, abundance of a preferred species, and species response (coppice or mortality). Elephant can cause a change of vegetation state, and increase spatial homogeneity of a plant population. The remnant population of woodland trees should provide the potential for recolonization, in which case the system would reflect the stable limit cycle. However, if browsing inhibits seedling recruitment, the system could reflect either a multiple stable state system or an artificial equilibrium imposed on a stable limit cycle. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul / Soil compaction is closed related to agriculture as well as animal production management. Soil quality improvement has not been always achieved with use of soil conservation practice as no-tillage or use of animal production integrated to agriculture management. Agricultural traffic and soil management effects on soil compaction are not well known, specially associated to wet soils, and in many cases, has induced to compaction states which restrict crop growth and productivity, which in turn, has lead farmers to break the compaction using mechanical tools as plow or chisel. To better understand compaction effects and critical values of soil physical properties on black beans growth and productivity four studies were set up out in the field. Another field study were performed in five typical dairy farms in Rio Grande do Sul plateau which use systems with agriculture integrated with animal production, including forage management and time of grazing. The objective of this study was to study animal trampling effects on soil physical properties, bulk density, porosity and soil resistance. The first experiment cultivated black beansi in a clayey Oxisol with the following treatments: a) immediate compaction caused by traffic of 16.6 Mg front buck loader; b) chiseling and; c)residual compaction from six years no-tillage. The additional compaction affected mass-volume relations, soil moisture and resistance, a well as black beans growth and productivity. The other three experiments were carried out in an Alfisol from central depression of Rio Grande do Sul with objectives to compare effects of immediate and residual compaction and soil chiseled on soil physical properties and black beans growth and productivity. The immediate compaction was obtained by traffic of a 9 Mg buck loader on present soil condition and on soil compacted with 10 Mg one year ago. For studied Alfisol the bulk density which restricted crop growth and productivity had value higher than 1.7 Mg m-3. The state of compaction with bulk density higher than 1.8 Mg m-3 and macroporority lower than 0.1 m3 m-3 reduced black beans height, leaf area index and crop productivity in abou 50%. The negative effects of additional compaction were maintained after twelve months and succession of three crops (soybeans, oats and black beans), reducing the black benas productivity in 61.8 %. Breaking compaction of a Oxisol under six no-tillage or Alfisol under twelve years no-tillage by soil chiseling did not improve soil quality which induce significant black benas productivity. The bulk density expressed the increase of soil compaction caused by animal trampling, reaching values of 1.77 Mg m-3, measured immediately after animal trampling and, was more significant at superficial layers where the effects on macroporosity were greater. / A compactação dos solos está intimamente relacionada com o manejo da agricultura e da pecuária na propriedade rural. A adoção de práticas conservacionistas como o plantio direto e a integração pecuária e agricultura não tem refletido em segurança aos agricultores quanto à melhoria permanente de aspectos físicos, químicos e biológicos do solo. O desconhecimento de ideais condições de trafegabilidade e manejo dos solos, associado à umidade inadequada às práticas agrícolas, tem aumentado a compactação do solo, podendo comprometer a produtividade e o desenvolvimento de plantas exigindo a adoção de medidas extremas como a escarificação do solo para melhorar a condição presente. Foram realizados quatro experimentos a campo, onde os efeitos da compactação causada pelo tráfego de máquinas foram avaliados pelos atributos do solo e no crescimento e produtividade da cultura do feijão. Outro estudo, realizado a campo, em cinco propriedades típicas de produção leiteira do planalto riograndense, que adotavam como sistema de produção a integração lavoura e pecuária, com distintos manejos de forrageiras e tempo de permanência dos animais nas glebas, teve por objetivo estudar o impacto do pisoteio animal nos atributos físicos do solo como: densidade, porosidade e resistência do solo a penetração. No primeiro experimento foi cultivado feijão em Latossolo argiloso do Planalto Gaúcho e se estabeleceu comparação entre: a) compactação imediata aplicada por tráfego de máquina com 16,6 Mg, b) compactação residual de 6 anos de plantio direto, e c) escarificação. A compactação adicional afetou as relações massa-volume, a umidade e a resistência do solo à penetração, assim como, a produtividade e o crescimento do feijoeiro. Os outros experimentos foram desenvolvidos em Argissolo da Depressão Central do RS, com o objetivo de comparar estados de compactação imediata, compactação residual aplicada em ano anterior e residual de compactação de 12 anos de plantio direto com a escarificação nas propriedades físicas do solo, na umidade e no crescimento e produtividade do feijoeiro. A compactação imediata foi obtida pelo tráfego de máquina com 9 Mg sobre o solo na condição presente e sobre resíduo de compactação de tráfego de 10 Mg aplicada em ano anterior. No Latossolo a densidade restritiva a produtividade do feijão e do trigo foi de 1,4 a 1,5 Mg m-3. Para o Argissolo, a densidade do solo restritiva a produtividade do feijoeiro foi superior a 1,7 Mg m-3. Os estados de compactação com densidade do solo maior que 1,8 Mg m-3 e macroporosidade menor que 0,1 m3 m-3, reduziram a altura de planta, a área foliar e a produtividade do feijoeiro em torno de 50 %. Os efeitos negativos da compactação adicional mantiveram-se após doze meses e sucessão de três cultivos (soja, aveia e feijão), reduzindo a produtividade de feijão em 61,8 %. O valor da densidade crítica baseada no intervalo hídrico ótimo (IHO) foi de 1,75 Mg m-3. A escarificação não representou ganho em qualidade do solo para áreas com seis anos de plantio direto em Latossolo e doze anos de plantio direto em Argissolo que implicasse em aumento de produtividade. A densidade do solo expressou o aumento da compactação do solo provocada pelo pisoteio animal, atingindo o valor de 1,77 Mg m-3 medida imediatamente após o pisoteio animal e mostrando-se mais significativa nas camadas superficiais do solo e, nessas, os efeitos na macroporosidade foram mais evidentes.

Abstract Plants and soil organisms are closely linked. Plants are the sole source of carbon in the soil and soil organisms are responsible for recycling of nutrients, making them available for plant growth. To understand the function of a system, it is important to understand the interactions between the soil and plants. These interactions have mainly been studied in temperate areas, with few studies in the arctic and subarctic. The aim of this thesis was to investigate the effect of ecological disturbances in sub- and low-arctic grasslands on soil organisms and plant-soil feedback relationships. The effect of removal of vegetation, replanting of a local plant species, and different components of grazing (trampling, defoliation and return of nutrients) on soil decomposer organisms were studied. Whether short term effects of defoliation depended on plant species community was also studied, as well as whether defoliation in the field could create changes in the soil system systems that affect the growth of seedlings. Experiments were conducted under both controlled greenhouse conditions and in field sites. The results showed that physical disturbance (removal of vegetation and trampling) reduced the abundance and diversity of soil biota. Defoliation increased soil decomposer abundance in the short term. Plant species composition did not affect soil biota and only in a few cases did it changes their responses to defoliation. In the long-term, effects of fertilization and defoliation on the soil biota were context-dependent. However, defoliation did create changes in the soil that reduced the growth of seedlings planted into the soil. Furthermore, plant species community and spatial heterogeneity (revealed by blocking) had important effects on the soil communities.