Adding fine woody debris accelerates the turnover of soil carbon pool in high-latitude urban plantations in China

The decomposition and transformation of woody debris (WD) generated during forest growth and management have a significant impact on soil organic carbon (SOC) dynamics and carbon balance. However, our understanding of the impact of WD on SOC in urban plantations remains limited. To fill this gap, we conducted this study.

In this study, we established four treatments involving the addition of fine woody debris (FWD) on the soil of six urban plantations in Harbin, Heilongjiang Province, China, to investigate changes in SOC. The four treatments for adding FWD were as follows: Control, low-dose carbon addition (LC), medium-dose carbon addition (MC), and high-dose carbon addition (HC). The added carbon content in the four treatments was 0 g m⁻², 250 g m⁻², 500 g m⁻²,1000 g m⁻². After 13 months, we measured the dynamic changes of SOC and nitrogen fractions as well as the characteristics of the carbon pool in the 0–10 cm thick soil layer.

The study results indicate that, when compared with the control group, the addition of FWD had a noteworthy impact on basic soil parameters such as soil water content, pH, and total nitrogen. This addition resulted in an augmentation of labile organic carbon fractions, including microbial biomass carbon and easily oxidizable organic carbon. However, no significant effect was observed on the content and storage of SOC. In addition, it is found that adding FWD has a significant positive effect on carbon pool management index (CPMI), while CPMI has a significant negative effect on SOC.

The addition of FWD to urban plantations in Heilongjiang Province, China, for 13 months can increase the turnover of SOC and improve soil quality. However, the increase in SOC storage is limited and a longer decomposition time might be necessary to see a significant SOC sequestration effect.