Effects Of Wet Deposition Of Nitrogen And Phosphorus And Litter Addition On Soil Active Organic Carbon Pool And Nitrogen And Phosphorus In Broad-Leaved Pinus Koraiensis Forest

With the rapid development of global industrialization and the increase of atmospheric nitrogen and phosphorus deposition,forest litter decomposition and nutrient release will be promoted,which will affect the accumulation and release of soil organic carbon.In this study,Pinus koraiensis plantation and broad-leaved Pinus koraiensis forest were taken as the research objects,and the wet deposition of nitrogen and phosphorus(low concentration(5g N·m-2 · a-1,5g P·m-2·a-1),medium concentration(15 g N·m-2·a-1,10 g P·m-2·a-1)were carried out from May to October 2018,litter addition and removal and their superposition on soil active organic carbon pool,nitrogen and phosphorus content,C/N,C/P and N/P were studied.The results are as follows:(1)Effect of wet deposition of nitrogen and phosphorus on suddenly activated organic carbon pool and nitrogen and phosphorusThe content of soil total organic carbon increased with time under the treatment of low and medium concentration in Pinus koraiensis plantation,increased first and then decreased with time under the treatment of medium concentration,decreased with time under the treatment of high concentration,decreased with time under the treatment of low and medium concentration in broad-leaved Pinus koraiensis plantation,increased first and then decreased with time under the treatment of medium and high concentration;In the two forest types,the soil microbial biomass carbon content decreased significantly with the increase of wet deposition concentration;in August and October,the concentrations of nitrogen and phosphorus in the wet deposition of Pinus koraiensis plantation increased significantly,while in October,the concentrations of nitrogen and phosphorus in the wet deposition of Pinus koraiensis plantation decreased,while in broad-leaved Pinus koraiensis plantation,the concentrations of nitrogen and phosphorus in the wet deposition increased;in August,the treatment of low concentration of nitrogen and phosphorus wet deposition significantly increased the content of Soil easily oxidized organic carbon in Pinus koraiensis plantation,while in October,the treatment of low concentration and medium concentration in broad-leaved Pinus koraiensis forest significantly reduced the content of soil easily oxidized organic carbon.The changes of soil total nitrogen content in May and August of the wet deposition treatment of nitrogen and phosphorus in Korean pine plantation were the same,they were first decreased and then increased,in October,the soil total nitrogen content first increased and then decreased,and in May,the soil total nitrogen content in broad-leaved Korean pine forest increased with the increase of the wet deposition concentration of nitrogen and phosphorus.(2)The effect of litter treatment on suddenly activated organic carbon pool and nitrogen and phosphorusThe content of soil total organic carbon was significantly increased by litter addition in August in Pinus koraiensis plantation,decreased by litter removal,increased by litter addition and removal in October,and decreased by litter removal in broad-leaved Pinus koraiensis plantation.In the two forest types,litter removal significantly reduced soil particulate organic carbon;litter addition and removal significantly increased and decreased light fraction carbon content;litter addition and removal significantly increased and decreased microbial biomass carbon content in August;litter addition significantly increased soil dissolved organic carbon content in the two forest types.Litter treatment had no significant effect on soil total nitrogen and phosphorus.(3)Effects of wet deposition of nitrogen and phosphorus and litter treatment on soil active organic carbon poolIn May,the content of total organic carbon and easily oxidized organic carbon in Pinus koraiensis plantation was the highest under the control of nitrogen and phosphorus wet deposition and high concentration litter removal,and the content of particulate organic carbon,light fraction carbon and dissolved organic carbon was the highest under the high concentration and litter addition.The content of total organic carbon and easily oxidized organic carbon in the broad-leaved Pinus koraiensis plantation was the highest in the low and high concentrations of litter removal treatment,and the content of particulate organic carbon,light fraction carbon and dissolved organic carbon was the highest in the nitrogen phosphorus wet deposition control litter addition treatment.In August,the interaction of wet deposition of nitrogen and phosphorus with litter treatment in Pinus koraiensis plantation,the contents of particulate organic carbon,light fraction carbon and easily oxidized organic carbon were litter addition>litter removal>litter control under wet deposition of nitrogen and phosphorus,litter control>litter removal>litter addition under low,medium and high concentrations;the contents of total organic carbon,particulate organic carbon,light fraction carbon,easily oxidized organic carbon,microbial carbon and dissolved organic carbon in broad-leaved Pinus koraiensis plantation were litter removal>litter addition under the control of wet deposition of nitrogen and phosphorus,medium concentration treatment,litter addition>litter removal under the low and high concentration treatment.In October,the content of total organic carbon and dissolved organic carbon in Pinus koraiensis plantation was the highest under the treatment of low,medium and high concentrations of nitrogen and phosphorus litter,while the content of particulate organic carbon,light fraction carbon,easily oxidized organic carbon and microbial biomass carbon was the highest under the treatment of low,medium and high concentrations of nitrogen and phosphorus litter;the content of total organic carbon,light fraction carbon and particulate organic carbon was the highest under the treatment of low,medium and high nitrogen and phosphorus litter removal,while the content of microbial biomass carbon,dissolved organic carbon and easily oxidized organic carbon was the highest under the treatment of low,medium and high nitrogen and phosphorus litter addition in broad-leaved Pinus koraiensis plantation.