Changes in soil microbial communities induced by warming and N deposition accelerate the CO2 emissions of coarse woody debris

Warming and nitrogen (N) deposition are two important drivers of global climate changes. Coarse woody debris (CWD) contains a large proportion of the carbon (C) in the total global C pool. The composition of soil microbial communities and environmental changes (i.e., N deposition and warming) are the key drivers of CWD decomposition, but the interactive impact between N deposition and warming on the composition of soil microbial communities and CWD decomposition is still unclear. In a laboratory experiment, we study and simulate respiration during decomposition of the CWD (C98) of Cryptomeria japonica (CR) and Platycarya strobilacea (PL) in response to warming and N deposition over 98 days. Resuts show that either warming or N addition significantly accelerated the C98 of the two tree species by altering the soil microbial community (bacterial:fungi and G+:G–). The combined treatment (warming + N) resulted in a decomposition effect equal to the sum of the individual effects. In addition, the species composition of bacteria and fungi was obviously affected by warming. However, N deposition had a remarkable influence on G+:G–. Our results indicated that N deposition and warming will observably alter the composition and growth of the microbial community and thus work synergistically to accelerate CWD decomposition in forest ecosystems. We also present evidence that N deposition and warming influenced the composition and balance of soil microbial communities and biogeochemical cycling of forest ecosystems.