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Previous issue date: 2008-09-15 === In northeastern semiarid, seasonality on precipitation temporal distribution, high intensity storm events and inadequate management of native vegetation can promote soil erosion. Vegetation removal causes soil surface exposure, reduces soil water storage capacity and can be the source degradation processes. In this context, this approach aims to analyze water and soil erosion processes on a 250 m2 undisturbed experimental plot with native vegetation, slope 2.5% by using 2006 and 2007 monitoring data. The site was instrumented to monitor rainfall, overland flow runoff and erosion by using a 5 m? tank downstream the plot. Soil erosion monitoring was made by transported sediment and organic matter collection after each event. Field infiltration experiments were made at 16 points randomly distributed within the plot area by using a constant head infiltrometer during drought and rainy seasons, respectively. Infiltration data revealed high spatial and temporal variability. It was observed that during the beginning of the rainy period, 77% of the events showed runoff coefficient less than 0.05. As the rainy season began, soil water increase produced annual species germination. High intensity storms resulted in runoff coefficients varying between 0.33 and 0.42. Once the annual species was established, it was observed that approximately 39% of the events produced no runoff, which reflects an increase on soil water retention capacity caused by the vegetation. A gradual runoff reduction during the rainy season emphasizes the effect of vegetative density increase. Soil erosion observed data allowed to fit an empirical relationship involving soil loss and precipitation height, which was used to analyze the plot installation impact on soil erosion. Observed soil loss in 2006 and 2007 was 230 Kg/ha and 54 Kg/ha, respectively === No semi-?rido nordestino, a sazonalidade na distribui??o temporal da precipita??o, a ocorr?ncia de tormentas de alta intensidade e o manejo inadequado da vegeta??o nativa podem intensificar os processos erosivos. A retirada da vegeta??o desprotege a superf?cie do solo, diminui a capacidade de armazenamento de ?gua e d? origem aos processos de degrada??o. Nesse contexto, o objetivo dessa pesquisa ? analisar os processos hidrossedimentol?gicos numa parcela experimental com vegeta??o nativa, protegida, ?rea de 250 m2, declividade 2,5% a partir dos dados de monitoramento durante 2006 e 2007. Foram instalados equipamentos de medi??o e coleta autom?ticos da precipita??o e n?vel da ?gua num reservat?rio de 5 m? situado a jusante da parcela. O monitoramento da perda de solo foi feito atrav?s da coleta de solo e mat?ria org?nica transportada ap?s cada evento. Foram realizados ensaios de infiltra??o utilizando infiltr?metro com carga constante em 16 pontos distribu?dos na ?rea de estudo nas esta??es seca e chuvosa, respectivamente. Os ensaios revelaram alta variabilidade temporal e espacial na capacidade de infiltra??o. Observou-se que no per?odo correspondente ao in?cio das chuvas, 77% dos eventos apresentaram coeficientes de defl?vio menores que 0,05. Ao longo da esta??o chuvosa, o aumento da umidade no solo produziu a germina??o de esp?cies anuais. Tormentas de alta intensidade resultaram em coeficientes variando entre 0,33 e 0,42. Uma vez estabelecida a vegeta??o na parcela, observou-se que aproximadamente 39% dos eventos n?o produziram escoamento superficial, o que reflete o aumento da capacidade de reten??o da ?gua no solo pelas plantas. Uma gradual redu??o no escoamento superficial ao longo da esta??o chuvosa ressalta o efeito do aumento na densidade vegetal. Os dados observados de perda de solo permitiram ajustar uma fun??o emp?rica entre perda de solo e lamina precipitada, onde foi poss?vel observar o impacto causado pela instala??o da parcela. As perdas de solo em 2006 e 2007 totalizaram, respectivamente, 230 Kg/ha e 54 Kg/ha
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