Mechanisms of soil organic carbon accumulation in acidified forest soils

Southern forests contribute more than 50% of soil organic carbon (SOC) in China’s forest ecosystem, and the soil can still accumulate SOC. Deeply developed tropical and subtropical forest soil has undergone severe acidification. Based on the input-output principle, the accumulation of Al toxicity caused by Al³⁺ aggregation, results in a decrease in organic matter input to the soil. Previous studies suggest that ecological function as a carbon sink forest is still present, however, the mechanism of continuous SOC accumulation in deeply acidified forest soil remains unclear.

Based on the long-term simulated acid addition experiment at Dinghushan, we conducted research on the mechanism of SOC accumulation and stabilization in monsoon evergreen broad-leaved forests under acid addition treatment. Our result showed that in terms of carbon composition, acid addition significantly increases the accumulation of particulate organic carbon (POC) and mineral-associated organic carbon (MAOC). Regarding the sources of carbon, acid addition significantly reduced the accumulation of microbial residue carbon, while significantly increased lignin phenol from plant sources. Further analysis revealed that the increase in soil lignin phenol caused by acid addition and the inhibition of soil microbial decomposition promoted the accumulation of POC, while the accumulation of MAOC was mainly attributed to mineral protection by iron-aluminum oxides and metal cations. These results suggest that mineral protection and continuous input of plant-derived carbon have improved SOC accumulation and stabilization with soil acidification. This study emphasizes that forest soil acidification promotes both mineral protection and the accumulation of plant-derived carbon. This finding mechanistically supports the function of continuous carbon sequestration in deeply acidified forest soil.

The study titled "Soil acidification enhanced soil carbon sequestration through increased mineral protection" was published online in Plant and Soil. Mengxiao Yu is the first author of this paper and Professor Junhua Yan is the corresponding author. This study was supported by the National Science Fund for Distinguished Young Scholars, the National Natural Science Foundation of China and Guangdong Basic and Applied Basic Research Foundation. The article link is: https://doi.org/10.1007/s11104-024-06608-8

First author information: Mengxiao Yu: Engineer, Research Center for Ecology and Environmental Sciences, South China Botanical Garden, Chinese Academy of Science, Research field: Forest ecology and soil carbon cycle, E-mail: yumx@scib.ac.cn ; Tel :020-37252720.

Figure 1. A conceptual diagram of the impact of 11-year acid addition on SOC sequestration in subtropical forest