Effects of nitrogen addition on microbial respiration and root respiration in a sandy grassland.

Abstract

Soil respiration includes root respiration and microbial respiration. Effects of nitrogen addition on root respiration and microbial respiration may be quite different. We examined the effects of N-addition on the releasing of soil CO2 and the responses of root respiration and microbial respiration in a Keerqin sandy grassland, Northeast China. Results showed that both soil respiration and microbial respiration firstly rose then declined during the growing season (May to October). Microbial respiration was the main contributor of soil respiration, accounting for 82.6%. Contribution rate of root respiration altered with months, peaking in May (49.4%) and August (41.9%), with an average contribution rate of 17.4% during the growing season. Root respiration (with a decrease of 17.7%) was more sensitive to N-addition compared with microbial respiration (with a decrease of 3.9%) at 10 ℃. N-addition increased Q10 values of soil respiration and microbial respiration, and enhanced their sensitivity to soil water content variation.