Abstract: The increased nitrogen (N) availability and soil acidification are two important ecological processes undergoing in most terrestrial ecosystems in the background of N deposition and sulfur (S) deposition. The two processes and their coupling actions obviously disturb soil respiration, further exterting important influnces on the carbon budget in forest ecosystems. Here we reviewed the effects and underlying mechanisms of N deposition and S deposition on soil respiration in forest ecosystems, analyzed the coupling effects of N deposition and S deposition, and proposed the main research directions in this field in the future.

Key words: enzyme activity., Chinese fir, PLFA, N-fixing tree species