Changes in soil carbon and nitrogen stocks and microbial community after forest conversion in a subtropical region

The quantitative understanding of different land use is still limited. We selected typical natural secondary forest (NSF) and Chinese-fir plantation (CPF) in southern China to quantify changes of soil carbon (C) and nitrogen (N) as well as microbial community composition after forest conversion in the soil profile up to 60 cm. The results showed that soil CN stocks and all functional microbial groups in CPF were significantly lower in the topsoil but did not change in the subsoil (10-60 cm) compared to those in NSF after 24 years conversion. Soil C/N ratio did not differ between the two forests for all soil depths. Correlation analysis showed that the abundance of microbial groups in the topsoil was significantly related to soil organic carbon, total nitrogen and forest floor N stock. Redundancy analysis showed that available N, especially NO3--N, was the most dominant factor influencing the microbial community composition. These findings suggest that the plantation could inhibit the accumulation of soil C and N, but the changes are primarily evident in surface soil after conversion. The study improves our understanding of soil C, N and microbial community changes under different land uses and provides insights into sustainable management of Chinese forests.

Automated summary

The study revealed that the conversion to plantations inhibits the accumulation of soil carbon and nitrogen, particularly evident in the surface soil. Available nitrogen, especially NO3--N, plays a key role in influencing the microbial community composition.