ABSTRACT Amazonian soils have been suffering severe changes resulting from human activities in the region, causing significant changes in soil attributes that can contribute to greater susceptibility to erosion processes. Therefore, the present work aimed to estimate the erodibility in natural and anthropic environments in the southern region of the Amazon. Eight areas in the region were selected, including areas of native forest, savannah, cerradão, pasture and reforestation, delimiting 32 sampling points per area, with collections at a depth of 0.00-0.20 m, totaling 256 samples. Next, texture analysis and quantification of soil organic carbon were performed, and then erodibility was estimated by indirect prediction methods, Tukey’s test, Pearson’s correlation and factorial analysis of principal components. According to the results obtained, it was observed that the evaluated areas of native forest 1 and 2, cerradão and pasture present high susceptibility to erosion in relation to the cerrado, reforestation with genipap, teak and mixed areas. Therefore, it was noted that the high level of erodibility is associated with a greater predominance of sand fraction, K factor, Ki Kr and low clay content, as well as with the management employed in the areas.

Resumo A erodibilidade é uma característica do solo que representa a susceptibilidade com que suas partículas da camada mais superficial são levadas e transportadas para locais mais baixos por agentes erosivos, causando danos ambientais e econômicos. O objetivo deste trabalho foi estimar a erodibilidade do solo em áreas de pastagens e florestas no município de Porto Velho-Rondônia. Em campo, foram selecionadas três áreas com diferentes tipos de vegetação, uma com braquiária, outra com capim mombaça e uma terceira em floresta nativa. Nas áreas com pastagens, foi delineada uma malha amostral de tamanhos iguais (90 m x 60 m), e na área de floresta uma malha amostral aproximada (90 m x 50 m), com espaçamento regular de 10 m entre os pontos amostrais para ambas as áreas. A amostragem foi realizada nos pontos de cruzamento da malha na profundidade de 0,0-0,2 m, compondo 70 pontos amostrais nas áreas com pastagens e 60 pontos amostrais na área de floresta, totalizando 200 amostras. Em seguida, foram realizadas análises laboratoriais para determinação da textura seguida do fracionamento da areia, e do carbono orgânico seguida da estimativa da matéria orgânica do solo. Os fatores de erodibilidade foram calculados por meio de modelos de predição indireta e, em seguida, foram aplicadas técnicas univariadas, geoestatísticas e multivariadas. Os ambientes de pastagem diferiram do ambiente de floresta. No entanto, a área de capim mombaça funciona como um ambiente intermediário entre a floresta e a braquiária, estando mais próxima do ambiente de floresta.

Abstract “Erodibility” is a characteristic of the soil that represents the susceptibility with which its particles from the most superficial layer are taken and transported to lower places by erosive agents, causing environmental and economic damages. This work estimated soil erodibility in pastures and forest areas in the municipality of Porto Velho-Rondônia. In the field, three areas with different types of vegetation were selected, one with brachiaria, another with mombaça grass, and a third in native forest. In areas with pastures, a sampling mesh of equal sizes was outlined (90 m x 60 m), and in the forested area an approximate sampling mesh (90 m x 50 m), with a regular spacing of 10 m between the samples points for both areas. The sampling was done at the crossing points of the mesh at a depth of 0.0-0.2 m, composing 70 sample points in the areas with pastures and 60 sample points in the forest area, totaling 200 samples. Then, laboratory analyzes were carried out to determine the texture followed by the fractionation of the sand, and the organic carbon followed by the estimate of the organic matter of the soil. The erodibility factors were calculated using indirect prediction models, and then, univariate, geostatistical and multivariate techniques were applied. The pastures’ environments differed from the forest environment. However, the mombaça grass area functions as an intermediate environment between the forest and the brachiaria, being closer to the forest environment.