Riparian forest potential to retain sediment and carbon evaluated by the 137Cs fallout and carbon isotopic ratio techniques

Abstract

Riparian forests can provide an important service for aquatic ecosystems by sequestering hillslope-derived sediments. However, the width of a riparian buffer zone required to filter sediments is not yet well-understood. Here are used two complementary tracers to measure sediment retention. The 137Cs technique and the soil carbon isotopic ratios (δ13C) are utilized to investigate sediment deposition and erosion rates on a slope transect cultivated with sugarcane followed by a secondary riparian forest zone in Iracemápolis, State of São Paulo, Brazil. The 137Cs technique and the δ13C analysis showed that the width of a riparian vegetation in accordance to a Brazilian Environmental Law (N° 4.771/65) was not sufficient in trapping sediments coming from agricultural lands, but indicated the importance of these forests as a conservation measure at the watershed scale. The complementary δ13C analysis together with soil morphology aspects allowed a better interpretation of the sediment redistribution along the sugarcane and riparian forest transects.