Abstract

Soils in floodplain ecosystems are sedimentary and subject to removal, transport, and deposition processes caused mainly by the water cycle, contributing to frequent variations in landscape patterns and continuous transformation of the floodplain environment. Given the constant disturbance caused by flood pulse variability, it is difficult to assess soil properties in floodplain ecosystems. Soil samples were collected at a depth of 0 to 0.10 m at floodplain and upland forest sites between Santarém and Gurupá, Pará State, Brazil. Samples were analyzed for pH H2O, aluminium, calcium, magnesium, potassium, phosphorus, total organic carbon, boron, zinc, copper, iron, manganese, sand, silt, and clay. Potential and effective cation-exchange capacity, sum of bases, base saturation, aluminum saturation, and organic matter were calculated. Data were subjected to descriptive analysis, analysis of variance, correlation analysis, and hierarchical clustering. Chemical and textural parameters differed significantly between floodplain and upland forest soils. Soil properties were highly heterogeneous. Aluminium and aluminium saturation had the highest coefficients of variation among floodplain samples, whereas pH H2O and base saturation had the lowest. It is possible to infer from the results that floodplain forest soils maintain high levels of fertility. However, this environment also shows high acidity and toxic levels of exchangeable aluminium.

Key words: Flood pulse, soil fertility, floodplain ecosystem.