Spatial pattern of carbon stocks in forest ecosystems of a typical subtropical region of southeastern China

Spatial pattern information of carbon (C) density and storage in forest ecosystems plays an important role in the evaluation of C sequestration potential and forest management practices. However, such information related to subtropical forests still remain poorly understood. In this study, we collected forest samples from 838 plots in a typical subtropical forest of Zhejiang Province, southeastern China. The Moran's I, geostatistics and geographical information system (GIS) techniques were applied to reveal the spatial pattern of C stocks in forest ecosystems. The results showed that the mean C density of forest ecosystems in Zhejiang Province was 145.22 Mg ha−1, and the forest vegetation, soil, litter, and dead wood layer C densities were 27.34, 108.89, 1.79, and 1.38 Mg ha−1, respectively. The spatial distribution of forest ecosystems C density 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, forest management, economic and social development. In addition, the C storage of forest ecosystems in Zhejiang Province was approx. 877.19 Tg (1 Tg = 1012 g), with 203.88 Tg in the vegetation layer, 656.20 Tg in the soil layer, 10.84 Tg in the litter layer, and 6.27 Tg in the dead wood layer, accounting for 23.24%, 74.81%, 1.24%, and 0.71% of the total C storage, respectively. These results indicated that the soil layer is the most important contributor to C storage in subtropical forest ecosystems. The young and middle-aged forests with low C densities dominated in the study area. Therefore, in order to enhance the C sequestration potentials, forest management should focus on the selection of tree species, management of stand-age structures and implementation of sustainable afforestation and reforestation practices in the future.