Search

Water erosion is the principal degradation process of tropical soils, and its effects can be measured by modeling techniques. Erosion models provide a diagnosis of the soil loss intensity and can support the planning of soil conservation practices. Models with low data requirements, such as the Revised Universal Soil Loss Equation (RUSLE) and, more recently, the Erosion Potential Method (EPM), are mainly applied in Brazil. Thus, the objective of this work was to estimate water erosion soil-loss rates using the EPM and RUSLE models on a tropical subbasin, followed by a comparison of their outcomes. The models’ application considered soil physical parameters, edaphoclimatic conditions of the area, land use, and subbasin management practices. The accuracy of the methods was verified using total transported sediment and water discharge data. We compared the models using Pearson's correlation analyses, considering a 5% of significance. We found a predominance of moderate-intensity erosion with average soil loss of 1.17 and 1.46 Mg ha-1 year-1, measured by EPM and RUSLE, respectively. The EPM model underestimated soil losses by 15.27%, and RUSLE overestimated by 19.08%, indicating a higher percentage of areas with high erosion rates (4.60%). The models presented results with a different order of magnitude, but with significant correlations, indicating that both methods pointed out similar zones of intense and light-erosion rates.

O objetivo deste trabalho foi avaliar as perdas de solo provenientes de trechos de estradas de uso florestal inseridas na região de Itaiópolis, Santa Catarina, que apresenta relevo ondulado a fortemente ondulado em dois tipos de solo: Cambissolo Húmico Distrófico típico e Argissolo Vermelho-Amarelo Distrófico típico. A erosividade da chuva foi calculada através de pluviogramas e de dados de pluviosidade da empresa Rigesa - Soluções em Embalagens MeadWestvaco; a erosividade do solo foi calculada em função dos resultados de análises, a declividade e comprimento de rampa foram medidos em campo e os fatores C e P, estipulados através da literatura. A hipótese de similaridade entre os valores reais monitorados pelo período de um ano e os valores estimados pela RUSLE foi evidenciada através de análise estatística, que apresentou alta correlação nos tratamentos avaliados e se manteve dentro do limite crítico proposto pela análise, validando, portanto, essa hipótese.The objective of this work was to evaluate the soil losses from a portion of forest roads located in a region with undulated to heavily undulated relief in two types of soil: Humic Cambissoil, typical Dystrophic and Red-Yellow Argissoil, typical Dystrophic. The rainfall erosivity was calculated using rainfall data through the Rigesa Company, the soil erodibility was calculated based on the results of the analyses, the declivity and the slope length were measured in the field, and Factors C and P were estimated from literature. The similarity hypothesis between the real values monitored over a one year period and the estimated values using the RUSLE were evidenced via statistical analyses that presented high correlations in the evaluated treatments, remaining inside the critical limit considered for the analyses, therefore validating the hypothesis.

En el presente trabajo se cuantificaron las pérdidas de suelo por erosión fluvial (2006-2008) en dos cauces ribereños con cobertura de Haematoxylum campechianum, Dalbergia brownei y Brachiaria mutica en la Reserva de la Biosfera Pantanos de Centla, SE de México. Se evaluó la relación entre la textura, materia orgánica y pH de los suelos con la pérdida de los mismos. Las pérdidas de suelo se estimaron en 18 parcelas con varillas de erosión. La principal tendencia de las pérdidas de suelo por tipo de cobertura vegetal se dio en el orden H. campechianum>B. mutica>D. brownei. El mayor impacto erosivo en sitios con H. campechianum se relacionó con la textura arenosa de los suelos y el grado de perturbación de los sitios (baja densidad de árboles, alta dispersión y falta de asociación con otros tipos de vegetación). Las pérdidas totales de suelo en parcelas con B. mutica al segundo año de estudio pueden relacionarse con la distribución superficial de las raíces de este pasto y con la actividad ganadera. Con este estudio se reconoce la importancia de los matorrales de D. brownei en la retención de suelos ribereños, sin embargo hay que considerar que la sola influencia de un tipo de cobertura vegetal puede no ser tan significativa como el papel de una comunidad vegetal, en la que su composición y densidad, así como su diversificación en morfología tenga un papel importante en la conservación de los suelos.Influence of three types of riparian vegetation on fluvial erosion control in Pantanos de Centla, Mexico. Wetlands constitute very important ecological areas. The aim of this study was to quantify the soil losses due to fluvial erosion from 2006 to 2008 in two riverbanks under three types of vegetal coverage dominated by Haematoxylum campechianum, Dalbergia brownei and Brachiaria mutica, in the Pantanos de Centla Biosphere Reserve, SE Mexico. The relationship between the texture, organic matter and pH of soils and soil losses was evaluated. We used erosion sticks to estimate soil losses in 18 plots (three plots per type, three vegetation types, two riverbanks). Soil loss decreased in this order: H. campechianum>B. mutica>D. brownie indicating that D. brownei scrubland has the most potential to retain soil. The higher erosive impact within H. campechianum sites can be related with the low density of these trees in the study areas, as we ll as the lack of association with other types of vegetation that could reinforce the rooting of the soil profile. Furthermore, soil losses in H. campechianum sites were dependent on soil texture. The soils under this type of vegetal coverage were mainly sandy, which are more vulnerable to the erosive action in comparison with fine textured soils or soils with higher clay content, like the ones found in D. brownei and B. mutica sites. Soil losses of 100 % in the second year ( B. mutica plots) can be attributed to the distribution of roots in the upper soil layer and also to livestock management along riverbanks. This study recognizes the importance of D. brownei scrublands in riverbank soil retention. Nevertheless it is necessary to consider the role of an entire vegetal community in future research. Rev. Biol. Trop. 57 (4): 1153-1163. Epub 2009 December 01.

Os métodos existentes para determinação indireta da erodibilidade não têm se mostrado adequados quando aplicados aos solos tropicais, particularmente no tocante aos latossolos brasileiros. Sendo assim, objetivou-se, com este estudo, desenvolver modelos para a estimativa da erodibilidade desse grupamento de solos, a partir de variáveis morfológicas, físicas, químicas e mineralógicas do solo. Foram feitas em 19 latossolos das várias regiões geográficas brasileiras, 129 determinações (variáveis independentes), cujos resultados foram submetidos à análise de regressão linear múltipla em "backward" utilizando o programa SAS, relacionando-se com a erodibilidade obtida diretamente no campo através de parcelas de perdas de solo (variável dependente). Foi possível desenvolver cinco modelos, com graus crescentes de complexidade e precisão para a estimativa da erodibilidade dos latossolos brasileiros, englobando 37 determinações que apresentam significância.The existent methods for indirect determination of erodibility have not been adequate when applied to tropical soils, mainly in relation to Brazilian (Oxisols). So, this study aimed to develop models for determination of erodibility of this soils group, from morphological, physical, chemical and mineralogical variables of the soil. In this way, using 19 latosols from the various Brazilian geographical regions, 129 determinations (independent variables) were made, whose results were submitted to multiple linear regression analyses in backward using the SAS program, correlating them with the erodibility directly obtained in the field through soil losses plots (dependent variable). It was possible to develop five models, with increasing degrees of complexity and precision, for the estimation of the erodibility of Brazilian latosols, involving 37 determinations that presented significance.