Fragilidade à perda de solo pelo processo erosivo das chuvas nas áreas rurais do município de Ruropólis, Pará.

Abstract

Among the major degradation by soil erosion, rainwater is the biggest one for tropical soils, impacting food production and water resources. The goal of this study was indetify diferente fraglity of soil for erosive processes, by rainwater, in rural Ruropolis town, Pará. This dissertation has two chapters. The first one is a brief environmental survery of the study area based in Geographic Information Systems (GIS) and field research. The greatest rainfall period is between December to May with monthly averages above 200 mm, with March being the wettest month. The Red-Yellow Argisol (in Brazilian classification) is the most expressive soil type, corresponding to 80.73% of the territory. About 75% of the municipal area is covered by forests and 25% is used in agriculture. The second chapters present estimation of the rainfall erosive potential and the map areas with different classes of fragility for soil loss by rainfall, through the use of three distinct methodologies:(1) the R factor of the Universal Equation of Soil Losses, (2) the empirical analysis of frailty in natural and anthropized environments; and (3) the database elaborated by Embrapa Soils, with spatial clipping of study area. The municipality was classified in high and very high erosivity classes. Regarding potential frailty, the weak (46%) and medium frailty (35%) classes stood out. When analyzing the emerging fragility that considers the land use and land cover, it was noticed the dominance of the very weak and weak classes. When analyzing frailty, with the spatial clipping of data obtained from Embrapa Soils, the results showed that the middle and high potential frailty class were the most expressive in territorial extension, accounting for about 38.81% and 32%, respectively, for each class. It was found that the largest territorial extension classified as emerging frailty was the average with 3.493,65 km2, covering approximately 50% of the study area. In the field, it was observed the development of erosion in furrows and deposition of sediments in areas of pastures with exposed soil, indicating signs of silting of streams. The research is in line with the Sustainable Development Goals, aiming to subsidize knowledge to minimize erosive impacts on soils of Ruropolis town.