Characteristics of soil organic carbon mineralization and influence factor analysis of natural Larix olgensis forest at different ages

Abstract

Soil organic carbon (SOC) mineralization is closely related to carbon source or sink of terrestrial ecosystem. Natural stands of Larix olgensis on the Jincang forest farm, Jilin Province were selected to investigate the dynamics of SOC mineralization and its correlations with other soil properties in a young forest and mid-aged forest at soil depths of 0–10, > 10–20, > 20–40 and > 40–60 cm. The results showed that compared with a mid-aged forest, the SOC stock in the young forest was 32% higher. Potentially mineralizable soil carbon (C0) in the young forest was 1.1–2.5 g kg−1, accounting for 5.5–8.1% of total SOC during the 105 days incubation period and 0.3–1.5 g kg−1 in the mid-aged forest at different soil depths, occupying 2.8–3.4% of total SOC. There was a significant difference in C0 among the soil depths. The dynamics of the SOC mineralization was a good fit to a three-pool (labile, intermediate and stable) carbon decomposition kinetic model. The SOC decomposition rate for different stand ages and different soil depths reached high levels for the first 15 days. Correlation analysis revealed that the C0 was significantly positively related with SOC content, soil total N (TN) and readily available K (AK) concentration. The labile soil carbon pool was significantly related to SOC and TN concentration, and significantly negatively correlated with soil bulk density. The intermediate carbon pool was positively associated with TN and AK. The stable carbon pool had negative correlations with SOC, TN and AK.