Effects Of Nitrogen Deposition On Litter Decomposition Of Different Communities In Changbai Montain Tundra

Based on the increase of nitrogen deposition in high latitude and altitude regions,Rhododendron aureum community,Rhododendron aureum-Deyeuxia angustifolia mixed community and Deyeuxia angustifolia community were selected in tundra of Changbai Mountain.According to the natural nitrogen deposition amount(23.6kg· hm^-2·a^-1)in Changbai mountain,field simulated nitrogen deposition experiment was carry out.Ammonium nitrate（NH₄NO₃）was used as nitrogen source,and three nitrogen levels(0g N·m-2·a-1,10 g N·m^-2·a^-1 and 20 g N·m^-2·a-1)were applied,the effects of nitrogen deposition on the amount,decomposition rate and nutrient release pattern of leaf litter in the Changbai mountain tundra were studied.the main results are as follows:1).The yield of mixed litter in the growing season was significantly higher than that of Deyeuxia angustifolia and Rhododendron aureum litter.Nitrogen application significantly reduced the yield of litter in Rhododendron aureum community;medium nitrogen treatment had no significant effect on the quantity of litter in Rhododendron aureum-Deyeuxia angustifolia mixed community,but high nitrogen treatment significantly reduced the quantity of litter;the litter amount of Deyeuxia angustifolia increased significantly after nitrogen application in the growing season.2).The mass loss rate of Deyeuxia angustifolia and mixed litter was significantly higher than that of Rhododendron aureum.The mass loss of mixed litter increased in the early stage of decomposition and was inhibited in the late stage of decomposition,the effect of medium nitrogen treatment on quality loss of Deyeuxia angustifolia was greater than that of high nitrogen treatment in the last 2 months.3).Nitrogen application did not change the trend of nutrient element changes during litter decomposition,but only changed the range of nutrient element change.The effect of simulated nitrogen deposition on total phosphorus content of litter content of litter was the most significant,and the change of total phosphorus content was positively correlated with nitrogen application level,it also promotes lignin decomposition in mixed litter and Deyeuxia angustifolia.4).The release rate of elements in Deyeuxia angustifolia litter was the fastest,mixed litter was the second,and Rhododendron aureum litter was the slowest.The accumulation-release pattern of total phosphorus in Rhododendron aureum litter was observed after nitrogen application.Total Carbon,total nitrogen and soluble sugar were the direct release patterns,the starch was enriched in 9th month,and the high nitrogen treatment was the largest,and then there was a decreasing trend.