Effects of Nitrogen Deposition on CO₂ Fluxes of Forest Soils in China

Nitrogen (N) deposition could change CO₂ efflux in forest soils,but current experimental results showed a high uncertainty in the direction and magnitude of the effect of N deposition.By combining the in situ monitoring results of N deposition experiments that were conducted in China,the effects of N deposition were assessed on CO₂ efflux in forest soils at national scale.The results showed that N deposition significantly declined 8.7% of the CO₂ efflux in forest soils in China,and this influence was greater for secondary forests and plantations than that for for primary forests.Moreover,N deposition had no significant effects on soil CO₂ efflux in broad-leaved,needle and mixed forests,but significantly decreased the CO₂ efflux in bamboo soils by 36%.However,this influence was significant only when the dose of N fertilization was more than 100 kg N·hm^-2·a^-1,and the effect of ammonium nitrate was greater than urea.The decline in CO₂ efflux in forest soils was due to the decrease of soil microbial activity induced by fertilized N.