Effects Of Simulated Short-term Nitrogen Deposition On The Production And Nutrients Of Urban Forest Litterfall

Urban forest construction is the focus of urban ecological system construction and an important part of ecological civilization construction.Litter plays an important role in forest ecosystem,participating in the material cycle and energy flow of forest ecosystem,and has been the focus of ecological research.The problem of nitrogen deposition caused by human activities such as urbanization has become one of the biggest threats to the global terrestrial ecosystem.With the increase of nitrogen deposition,whether the yield and nutrients of litters will be affected and whether the intensity of nitrogen deposition will reach the nitrogen saturation threshold required by urban forests needs further study.In recent years,the process of urbanization in Hefei has accelerated,and the ecological problems that follow should be paid attention to.In this study,an experimental plot was established in the Zipeng Mountain National Forest Park of Hefei City.Quercus acutissima forest,which is widely distributed in Hefei City,was selected as the research object.Different nitrogen deposition gradients:CK(0 kg N·ha^-1yr^-1),LN(50 kg N·ha^-1yr^-1)and HN(100 kg N·ha^-1yr^-1)were set by simulating short-term nitrogen deposition experiments to study the effects of nitrogen deposition on litter yield and nutrient content of urban forests.This study provides relevant references and scientific basis for the effectively coping with ecological changes caused by urban nitrogen deposition and improving the function of forest ecosystem.The experimental results are as follows:The experimental research results are as follows:(1)The annual yield of forest litter under different nitrogen deposition gradients is:LN(6.035 t·hm^-2)>HN(5.122 t·hm^-2)>CK(4.714t·hm^-2).Simulating short-term nitrogen deposition increases the annual yield of vegetation litter.The annual yield of litter increases with the increase of nitrogen deposition gradient within a certain range of nitrogen deposition intensity.When the nitrogen deposition intensity reaches 50 kg N·ha^-1yr^-1,the annual yield of litter is the largest.If you continue to increase the nitrogen deposition intensity to When 100 kg N·ha^-1yr^-1,the annual litter yield decreased instead.(2)The yield of forest litter under different nitrogen deposition gradients has no obvious difference in vegetation dormancy and growth periods.Nitrogen deposition did not significantly increase the yield of forest litter during the growing season.(3)There are significant differences in N,P,K,Mg element nutrient contents and C/P values under different nitrogen deposition gradients.Within a certain range of nitrogen deposition intensity,with the increase of nitrogen deposition gradient,the nutrient content of N and P elements in litter increases.Within a certain range of nitrogen deposition intensity,as the nitrogen deposition gradient increases,the K element nutrient content and C/P value in the litter decrease accordingly.Within a certain range of nitrogen deposition intensity,the Mg element nutrient content in the litter increased first and then decreased with the increase of the nitrogen deposition gradient.Within a certain range of nitrogen deposition intensity,with the increase of nitrogen deposition gradient,the N/P value of litter first decreases and then increases.(4)There is no significant difference in the content of various nutrient elements in forest litter under different nitrogen deposition gradients during the dormant period and growth period of forest vegetation.Nitrogen deposition did not significantly change the pattern of nutrient content in litter during different growth periods of forest vegetation.