ObjectiveSoil type, soil layer and stand type are considered as major factors affecting the distribution of soil organic carbon. Meanwhile, an altitudinal gradient is a redistribution of hydrothermal conditions at large-scale environments, and often involve the variations of soil and vegetation types at small scale. Therefore, there is an important significance for carbon sequestration management in forest ecosystem to explore the variations of soil organic carbon along an altitudinal gradient (179-1 430 m).

MethodTwenty soil profiles distributed with five soil layers along an altitudinal gradient in Jiulian Moutain were sampled. Moreover, vegetation type, soil type, soil organic carbon content and soil carbon storage were recorded for these soil samples to explore the vertical distribution and influencing factor of soil organic carbon along an altitudinal gradient.

ResultThe organic carbon content of top three soil layers (0-40 cm) increased linearly with the increase of elevation, whereas that of the bottom two layers (40-60 cm and 60-100 cm) decreased linearly with the increase of elevation. The pattern of soil carbon storage with elevations was similar with that of soil organic carbon content. However, there was a "U" shape between total soil carbon storage and elevation; Soil organic carbon content and carbon storage of top three soil layers in meadow soil were generally higher than those in red soil or yellow soil, the organic carbon content and carbon storage of top soil layer (0-20 cm) increased with the altitudinal gradient from red soil, yellow soil to meadow soil, meanwhile there was no significant difference among other layers. Soil organic carbon content and carbon storage of top three soil layers for Rhododendron woods and alpine meadow in high elevation were generally higher than those for the other vegetation types in low elevation, and there was the highest total carbon storage with 0-100 cm in alpine meadow and secondary broadleaved forest.

ConclusionThese results indicate that variations of top soil layer and vegetation types are the major factors to drive the variations of soil organic carbon along an altitudinal gradient in Jiulian Mountain of eastern China. The carbon emission of top soil layers in high elevation may increase with the increase of air temperature under the global warming.