Response Of Extracellular Enzyme Activity In Soil Of Pinus Koraiensis Var. Mongolica Forest To Nitrogen And Water Reduction

Temperate forests are suffering from increasingly severe environmental stresses as atmospheric nitrogen deposition intensifies and global precipitation patterns change.In order to explore the response of the enzyme activity of the temperate forest soil to the increase of atmospheric nitrogen deposition and the decrease of spatial precipitation and the regularity of interannual variation,we take the typical temperate forest-Changbai Mountain coniferous and broad-leaved mixed forest as the research object,set up three groups to carry on the experiment:simulated nitrogen deposition group(50 kg N ha^-1a^-1);reduced precipitation group（³0%）;simulated nitrogen deposition and reduced precipitation interaction group and control group.The main results are as follows:（1）Nitrogen application increased the activities of soil carbon cycle related enzymes and N-acetyl-β-D glucosidase.Water reducing had potential inhibition on carbon cycle enzyme and N-acetyl-β-D glucosidase activity,but this inhibition effect was only shown in nitrogen and water reducing group;（2）For leucine aminopeptidase,nitrogen application inhibits its activity,while water reducing promotes its activity.Meanwhile,the effect of nitrogen and water reducing on the activity of leucine aminopeptidase is not a simple addition and subtraction effect;（3）All treatments had no significant effect on urease and acid phosphatase;（4）All treatments have a significant effect on the activity of peroxidase,and nitrogen and water reducing is the key to the changes in the activity of polyphenol oxidase;（5）The interannual variation trend of soil enzyme activity generally shows that March is the low point of annual enzyme activity,while May is the high point of annual enzyme activity.This is mainly due to the repeated freezing thawing of soil in March,which directly destroys the physiological structure of soil enzymes and leads to the decrease of enzyme activity.In May,the resuscitation of soil microbes and plant roots is the key factor for increasing the activity of soil extracellular enzyme;（6）Redundancy analysis（RDA）showed that the total dissolve carbon in the soil is the best environmental factor to explain the changes of extracellular enzyme activities in soil.