Soil Microbial Community Structure And Enzymatic Activity In Swan Lake Alpine Wetland Of Bayanbulak

As the important components of the soil ecosystem,although soil microorganisms and soil enzymes account for only a small part of the soils,they plays an important role in the process of material circulation and energy flow in the soil ecosystem.Soil microorganisms and soil enzyme activities have often been proposed as primary and sensitive indicators of soil quality changes because they could provide immediate and precise information on small changes in soil organic carbon and other soil properties result from the environment changes.The primary objectives of this study were to investigate the effects of different surface water gradient and degradation gradients on the changes of Soil microorganisms and soil enzyme activities in the Bayanbulak Swan Lake Alpine Wetland.Three surface water treatments including perennial pools zone(A),ephemeral pools zone(B)and perennial dry zone(C)and three land degradation treatments including light degraded zone(L),moderately degraded zone(M)and severe degenerative zone(S)were selected.The basic physical and chemical properties,enzyme activity and microbial community structure at the 0 to 40 cm depth were determined in this study.Results showed that:Firstly,content of soil microbial decreased with the decrease of soil depth,irrespective to different treatments.In wetland soils,content of Gram-negative bacteria and Gram-positive bacteria were the most,while content of fungi and anaerobic bacteria were lower.Soil microbial content is sensitive to changes in wetland water and degradation.The total microbial content decreased by 24.59% and 46.33%,respectively for B and C compared with A.Land degradation enhancing the decrease in microbial content,the total microbial content under M and S decreased by 34.52% and 45.63%,respectively,compared with L.Secondly,responses of soil enzyme activity were sensitive to different water and degradation gradients.Different water gradients: the increase of water will inhibit the activity of soil invertase.The activity of invertase ranged from 7.16 to 35.92 mg/g,and its variation in the subsoil was higher than that in the surface soil.The response of urease activity to water change is notable than other enzymes,and the activity of urease in the dry area is significantly higher than that in other regions.Under different degrees of degradation: Land degradation inhibited the activity of soil invertase,and the activity of inveratse in L zone(33.18-36.01 mg/kg)and M zone(24.79-35.84 mg/kg)was significantly higher than that in S zone(1.46-2.32 mg/kg);the highest value of urease activity was found in moderately degraded area,indicating moderate degradation is beneficial to the improvement of urease activity.As a nitrogen source for higher plants,protease activity not only affected by water change and land degradation,but also affected by vegetation.Thirdly,responses of soil microbial biomass carbon and nitrogen to water changes and land degradation were different under different water change and land degradation levels.Different water gradients: Content of soil microbial biomass carbon under B is the highest and changes trends of soil microbial biomass carbon under A and C were different with the increase of soil depths;Water inhibited the content of soil microbial biomass nitrogen.The content of soil microbial biomass nitrogen in the surface soil was in the order of C(2.23-27.92 mg/kg)> A(5.18-21.88 mg/kg)> B(3.84-16.18 mg/kg).Under different degrees of degradation: higher content of soil microbial biomass carbon were found in the order of L zone(145.70-1 162.80 mg/kg)> M zone(6.84-468.97 mg/kg)> S zone(6.78-334.05 mg/kg);Content of soil microbial biomass nitrogen decreases with the increasing of degradation levels with the values range from 2.64 to55.16 mg/kg.The highest microbial entropy is found in the dry area and the severely degraded area,and the variations in the surface soil was greater with the changes of water and land degradation.Fourthly,the increase of water content is beneficial to the increase of soil carbon and nitrogen content,however land degradation lead to the decrease of soil carbon and nitrogen content.Content of soil total carbon,organic carbon and total nitrogen increased with the increase of water content,and decreased with the increase of degradation degree.