Variation Characteristics Of Soil Enzyme Activity And Microbial Biomass In Different Forest Types In Cold Temperate Zone

Soil and vegetation are ecosystems that interact,influence each other and develop in a coordinated manner,in which soil supplies the necessary materials for vegetation and vegetation improves soil fertility through its own apoplast,dead roots and root secretions.The Daxinganling,located in the cold-temperate zone,is formed in a cold climate with permafrost,and the permafrost environment is vulnerable to climate change and anthropogenic activities.In recent years,as the global temperature rises,the organic matter in the permafrost is released to the outside world in the form of gas,thus accelerating the process of global warming,and in this context,the enzyme activity and microbial biomass in the soil are bound to change.Therefore,in this paper,the soils of Pinus pumila forest,Rhododendron dauricum-Betula platyphylla forest,Rhododendron dauricum-Larix dahurica forest and Ledum palustre-Larix dahurica forest in Daxing'an Mountains in cold temperate forest region were selected as the research objects.The variation of soil enzyme activity and microbial biomass in the growing season(June to September),and the vertical spatial variation characteristics were studied to compare the variability of soil enzyme activity and microbial biomass in different forest types within the study period and the correlation between soil enzyme activity and microbial biomass and soil nutrients in different forest types and correlation with soil nutrient.The main results are as follows:1?There were great differences in the change of soil enzyme activity among the four forest types.Soil urease,protease and asparaginase activity varied from 0.73 mg·g-1·d-1 to 7.49 mg·g-1·d-1,0.32 mg·g-1·d-1 to 1.01mg·g-1·d-1 and 0.05 mg·g-1·d-1 to 0.11 mg·g-1·d-1.2?The change characteristics of soil microbial biomass carbon in Pinus pumila forest,Rhododendron dauricum-Larix dahurica forest and Ledum palustre-Larix dahurica forest showed an inverted "?" pattern,with the peak in August.The change of Rhododendron dauricum-Betula platyphylla forest showed an inverse "N" pattern.The change of soil microbial biomass nitrogen in four forest types was inverse "N" type,and the content in June and August was higher than that in July and September.3?Comparison of the mean values of soil enzyme activity and microbial biomass for the four forest types revealed that soil enzyme activity and microbial biomass decreased with increasing elevation,except for the Rhododendron dauricum-Betula platyphylla forest.4?In the vertical profile,the soil enzyme activity and microbial biomass of the four forest types had obvious "surface aggregation".5?Soil enzyme activity and soil microbial biomass were significantly or very significantly correlated with total organic carbon,total nitrogen,total phosphorus,total potassium,alkali-hydrolyzable nitrogen and pH.Soil fertility showed as follows:Ledum palustre-Larix dahurica forest>Rhododendron dauricum-Betula platyphylla forest>Rhododendron dauricum-Larix dahurica forest>Pinus pumila forest.