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

Background and aims 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 Río Chimbo watershed of Ecuador. Methods Soil carbon content, age, and erosion estimated from ¹³⁷Cs inventories was measured along an elevational transect under annual cropping, natural forest, páramo, pasture, and tree plantations. Results 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. Conclusions The effects of land use on soil loss in the Río Chimbo watershed suggest a loss and/or removal of soil carbon, particularly under annual cropping.