The response of coarse woody debris decomposition and microbial community to nutrient additions in a subtropical forest

Abstract

Coarse woody debris (CWD) plays an important role in forest C dynamics because it contains a sizeable proportion of total forest C. Understanding the factors controlling CWD decomposition is hence critical to assessing changes in forest C storage. In this study, we conducted a factorial fertilization experiment in a subtropical forest to investigate the influence of phosphorus (P) and nitrogen (N) availability on CWD decomposition of two species (Cryptomeria japonica (CR) and Platycarya strobilacea (PL)). We also characterized the microbial community of each CWD under different fertilization treatments using the method of phospholipid fatty acids (PLFAs). We found that fertilization with N, P, and N + P increased CWD respiration (RCWD) by 51.4–257.4%, and the magnitude of increase was species-specific. Between the two species, the RCWD of PL was significantly higher than that of CR. During the decomposition process, fertilization with P or N + P resulted in a significant accumulation of N and P in the CWD of both studied species. While N + P treatment resulted in the highest microbial growth of the decomposing CWD, especially for fungi and AMF, P treatment resulted in the highest bacterial growth. Our study indicated that P availability was the primary constraint of CWD decomposition, and N addition did not exacerbate P limitation. The balance of fungal and bacterial might also determine the release of additional nutrients during the decomposition period. To determine whether our results are generally applicable to subtropical forests, future studies should test more tree species with their CWDs in different stages of decomposition.