Abstract: In order to understand soil dissolved organic C (DOC) content along an altitude gradient in mountain area, soils derived from granite along an elevation gradient (179-1573 m) in Daweishan Mountain of Hunan Province were collected. Soil profiles were excavated down to parent material or rock horizon, and the effects of altitude and soil depth on DOC content were investigated. The results showed that DOC content ranged from 9 to 5326 mg·kg^-1, and increased with increasing the altitude both in top soil and subsoil. Soil organic C (SOC) and moisture can well explain the alteration of DOC content along the altitude gradient. DOC to SOC ratio ranged from 0.8% to 34.9%, and was similar at the foot and on the mountain peak. DOC to SOC ratio generally peaked in subsoil. At the same altitude, typical yellow soil with deep B horizon showed higher DOC content and DOC to SOC ratio in subsoil, while yellow soil with indistinct B horizon had lower DOC content and DOC to SOC ratio in subsoil. This study suggests that soil C content and composition varied differently with increasing altitude in top and subsoil. Deep subsoil should be considered in assessing mountain soil C pools.

Key words: radial growth, rapid warming, permafrost, Larix gmelinii, micro-topography