Effects of simulated nitrogen deposition on soil respiration in a Bambusa pervariabilis×Dendrocala mopsi plantation in Rainy Area of West China

From January 2008 to February 2009,a field experiment was conducted in Rainy Area of West China to understand the effects of nitrogen(N) deposition on the soil respiration in a Bambusa pervariabilis×Dendrocala mopsi plantation.Four treatments were installed,i.e.,no N added(control),5 g N·m-2·a-1(low-N),15 g N·m-2·a-1(medium-N),and 30 g N·m-2·a-1(high-N),and soil respiration rate was determined by infra-red CO2 analyzer.In the plantation,soil respiration rate had an obvious seasonal change,with the maximum in July and the minimum in January.In control plot,the annual cumulative soil respiration was(389±34) g·m-2·a-1.Soil respiration rate had significant positive exponential relationships with soil temperature at 10 cm depth and air temperature,and significant positive linear relationships with soil microbial biomass carbon(MBC) and nitrogen(MBN).Simulated N deposition promoted soil respiration significantly,with significant differences between the low-and medium-N and the control but no significant difference between high-N and the control.In control plot,surface soil(0-20 cm) MBC and MBN were 0.460 and 0.020 mg·g-1,respectively.In N-added plots,both the MBC and the MBN had significant increase.The fine root density in surface soil was 388 g·m-2,which was less affected by simulated N deposition.The soil respiration Q10 value calculated from soil temperature at 10 cm depth and air temperature was 2.66 and 1.87,respectively,and short-term N deposition had lesser effects on the Q10 value.The variation of soil respiration in the plantation was mainly controlled by temperature and soil microbial biomass,and simulated N deposition could increase the CO2 emission via increasing soil microbial biomass.