The dynamics in the forest soil carbon pool are extremely important in the global carbon cycle. However, our understanding of soil carbon dynamics is far from sufficient to predict soil carbon vulnerability to intensifying climate and land use change. The objectives of this study were to (1) examine the dynamics of soil organic carbon (SOC) and inorganic carbon (SIC) stocks in topsoils and subsoils, (2) identify the biogeochemical processes that control the changes in SOC and SIC following natural succession from Populus and Quercus forest, and (3) evaluate the effect of historical erosion on soil carbon stocks to understand how biogeochemistry and erosion processes control soil carbon dynamics. We investigated the dynamics of SOC and SIC and its controlling factors in both topsoil and subsoil in two adjacent temperate successional forests by combining the analysis of soil physicochemical properties and the techniques of stable carbon isotope and radiocarbon dating.
Results/Conclusions
We showed that the SOC stock increased in the top 10 cm of the soil but declined in the subsoil, whereas the SIC stock variation was the opposite. The soil total carbon (STC) stock in the 0-100 cm soil profile significantly increased during forest succession. In comparison to the early successional stage, the δ13C values of SOC were insignificantly enriched in the upper soil layers in the forest of the late successional stage. The SOC turnover rate (k) in the top 20 cm of the soil was higher in the late succession forest but it showed opposite trend in the subsoil during succession. Our results indicated that both the biogeochemistry and erosion processes codetermined SOC and SIC dynamics. Soil total nitrogen (TN) was the most important factor affecting SOC, and both SIC and k were mainly determined by SOC. Moreover, the estimated loss of STC because of soil erosion was 62.8 and 90.2 Mg ha-1 in Populus and Quercus forest over the past 10,000 years, respectively.