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

Abstract

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 137Cs inventories was measured along an elevational transect under annual cropping, natural forest, paramo, pasture, and tree plantations. Land use, particularly annual cropping, affected 137Cs 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 137Cs 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 14C levels) and 137Cs levels, where pasture sites had lower 137Cs 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.