Spatial variations of soil organic carbon stocks in a coastal hilly area of China

Quantification of soil organic carbon (SOC) stocks and their spatial variations at regional scales is a foundation to adequately assess plant productivity and soil carbon sequestration potentials so as to establish better practices for land use and land management. This study evaluated the spatial variation of SOC stocks from 1982 to 2012 in Wafangdian, Liaoning Province, China. To map SOC stock, we used geographically weighted regression (GWR) and regression kriging (RK) methods and a large set of soil samples, in which nine topographic and remote sensing variables were observed. The GWR approach performed better than the RK approach as the former has smaller absolute mean errors (AME), mean errors (ME), root mean square errors (RMSE) in comparison with observational data. Our results indicated that SOC stocks have an increasing trend in northeast and southwest mountainous areas in our study periods. Land-use changes caused by returning cultivation land to forest promoted SOC accumulation. The total SOC stocks of cultivation land, grasslands and forests within 0-0.2 m of soils were estimated to be 5.25 and 5.40 Tg in 1982 and 2012, respectively. This study provided important information of spatial variations in SOC stocks to agencies and communities in this region to evaluate soil quality and assess carbon sequestration potentials and carbon credits.