Land use effects on erosion and carbon storage of the Rio Chimbo watershed, Ecuador

Soil carbon storage is an important component of global carbon cycling. Andean Andisols have high carbon content and are vulnerable to erosion because of agricultural intensification and deforestation. This study examines the effects of land use on erosion and soil carbon storage in the Rio Chimbo watershed of Ecuador. Soil carbon content, age, and erosion estimated from Cs-137 inventories was measured along an elevational transect under annual cropping, natural forest, paramo, pasture, and tree plantations. Land use, particularly annual cropping, affected Cs-137 levels in the upper soil layers, but did not have an impact on total carbon storage to a depth of 1 m. Relative erosion rates estimated from Cs-137 inventories at sites under annual cropping averaged 27 t ha(-1) y(-1) over the erosion rate of non-cultivated sites. A linear relationship was observed between soil carbon age (determined by C-14 levels) and Cs-137 levels, where pasture sites had lower Cs-137 and older carbon compared to natural forest sites. The effects of land use on soil loss in the Rio Chimbo watershed suggest a loss and/or removal of soil carbon, particularly under annual cropping.