Response Of Soil Microorganisms To Nitrogen Deposition In Natural Secondary Forest Of Changbai Mountain

As an important part of terrestrial ecosystem,forest ecosystem has high service function value to human and other organisms.Atmospheric nitrogen deposition affects the nutrient cycling of forest ecosystem,and then has negative effects on it.At present,there are many researches on the influence of nitrogen deposition on terrestrial ecosystem,but there are few studies on temperate secondary forests,and the results of this study can be used as a supplement to this aspect.In Changbai mountain forest as the research object,this study simulated low nitrogen and high nitrogen deposition LN N 25kg?hm²·a?^-1,HN 50 N kg?hm²·a?^-1for the secondary forest soil pH,soil soluble organic matter?DOC/N?soil microbial biomass?MBC/N?,the effect of soil enzymes and soil respiration,the temperate forest biomass and the response of the material circulation of nitrogen deposition.Results:1)the nitrogen deposition significantly reduced the soil pH of the secondary forest in Changbai mountain,the soil total carbon content decreased,and the soil total nitrogen and total phosphorus content increased.2)nitrogen treatment has a certain catalytic effect on the content of DOC.Nitrogen treatment had a certain inhibitory effect on the upper soil,while the lower soil showed HN inhibition,and LN promoted the effect.3)nitrogen deposition has a certain catalytic effect on MBC in autumn?September and October?.LN treatment reduces MBC in the summer months?July and August?.The nitrogen deposition had an inhibitory effect on the upper MBN in the spring months?May and June?,and the LN treatment inhibited the MBN in the summer months,but it had a certain effect on the MBN in autumn.Nitrogen addition,upper soil MBC:N was lower than the first three months after the HN treatment,and the latter three months increased.There is little difference between LN and CK.Lower soil nitrogen treatment may be lower in May and October than in MBC:N decreases and other months increase.4)the nitrogen deposition has a inhibitory effect on peroxidase activity in spring,and LN treatment promotes its effect in autumn,reducing peroxidase activity in July and September.Nitrogen deposition has inhibitory effect on soil sucrase and soil urease activity,and it can promote the activity of soil acid phosphatase.5)LN treatment has a certain catalytic effect on soil respiration.The HN treatment had a positive effect on soil respiration in the first 3 months of the growth season,and was inhibited after 3 months.Nitrogen deposition had a inhibitory effect on soil microbial respiration in the first 3 months,which promoted the soil microbial respiration in autumn.6)Each index is affected by the nitrogen treatment,month,soil depth and its interaction.And the correlation of each index is different under different treatments.