Spatial variation of organic carbon density in topsoils of a typical subtropical forest, southeastern China

Spatial variation of regional soil organic carbon (SOC) stocks and the effects of environmental factors on SOC in forest soils play an essential part in modeling the global carbon cycle and climatic change. In this study, we analyzed topsoil samples (0-30 cm) from 838 plots in a typical subtropical forest of Zhejiang Province, southeastern China, using Moran's I, geostatistics and geographical information system (GIS) techniques. The results showed that the mean SOC density in the topsoils was 71.15 Mg ha−1 and the total storage in topsoils of Zhejiang Province was 0.47 Pg (Pg = 1015 g). The spatial distribution of SOC density based on kriging interpolation and local Moran's I hotspot analysis showed a decreasing trend from the southwest to northeast area, roughly in line with Zhejiang Province's topographic feature, as well as differences in land use, economic and social development. The results herein revealed that both dominant tree species and altitude (P < 0.01) have markedly affected SOC balance and accumulation in a typical subtropical forest of Zhejiang Province. Therefore, management of SOC should focus on the selection of dominant tree species (broad-leaved species), management of forest stand-age structures and implementation of sustainable practices so that the potential for carbon sequestration in forest soils can be maximized in the future.