Effects of forest age on soil erosion and nutrient loss in Dianchi watershed, China.

Soil erosion and nutrient loss are important environmental and ecological problems in the Dianchi watershed in southwestern China. Woodlands-the primary land type in the Dianchi watershed-play an important ecological role in controlling soil and water loss. In this study, we compared soil erosion and loss of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) in woodlands of different ages, i.e., young forest, medium forest, and near-mature forest, at the Dongda River catchment in south-western Dianchi watershed. Furthermore, changes in stoichiometries in soil were analyzed. The average degree of erosion of each forest age stage was below moderate. Based on the non-arable soil erosion modulus models of Cs and Pb, the soil erosion rates decreased gradually with the increasing forest age. The forest age affected soil nutrient distribution and loss. The losses of TOC and TP gradually decreased, while the losses of TN first increased and then decreased with the growth of forest age. TOC, TN, and TP were enriched in the topsoil. Forest age affected soil stoichiometry and soil nutrient supply level. In general, the forest can effectively reduce soil erosion and nutrient loss in the red soil area with the forest age increasing.