Soil Enzymatic Metrology And Characteristics Of Microbial Nutrient Limitation In The Hailuogou Glacier Retreat Area

The massive emission of greenhouse gases has accelerated the process of global warming,affected the global water cycle and accelerated the melting of glaciers.A large number of primary bare lands will be formed after glaciers melt and retreat,providing living space for microorganisms and pioneer plants,thus affecting the nutrient cycling process in the soil.The primitive bare land formed after glacier retreat provides a unique environment for studying the primary ecological succession.By exploring the limitation of soil microbial nutrients in glacier retreat areas and its key influencing factors,it is helpful to understand the dynamic change characteristics of soil microenvironment after glacier retreat,and can strengthen our response mechanism to predict the response of soil nutrient cycling to environmental changes.Therefore,the Hailuogou glacier retreat area is taken as the research area in this study.Based on the vegetation succession sequence from pioneer vegetation to top plant vegetation,taking soil samples of 8 different soil layers(O layer and A layer)with different shrinking years(T1(0a),T2(8a),T3(20a),T4(38a),T5(48a),T6(60a),T7(88a)and T8(128a)and plant samples of 20 a to 128 A,by measuring environmental variables,soil nutrients,microbial biomass,extracellular enzyme activity indicators,and based on the method of enzyme metrology,the nutrient limitation characteristics of soil microorganisms with different shrinking years were studied.The main research results are as follows:(1)In soil layers O and A,microbial metabolism is mainly limited by carbon and phosphorus.In layer O soil,soil microorganisms were limited by relative carbon at 20 years.From 0a to 128 a,soil microorganisms are limited by relative phosphorus.From 60 a to 128 a,the limit of soil microbial phosphorus increased gradually.In layer A soil,soil microorganism is limited by relative carbon at 60 a.Except for 0a and 60 a,the soil microorganisms in other shrinking zones are all limited by relative phosphorus,and the soil microorganisms are most limited by phosphorus in 20 a.From 60a(60a is not limited by carbon)to 128 a,the limit of soil microbial phosphorus shows an upward trend.Although some carbon is fixed by plants,the limitation of microbial carbon and phosphorus nutrients will cause rapid turnover and loss of soil carbon.(2)In soil layers O and A,the change trend of enzyme activity is similar with theretrogression process.Glucosidase,cellobiohydrolase,acetylglucosaccharase and phosphatase all showed double peaks with the retrogression process,while leucine aminopeptidase showed single peak mode.Moreover,by comparing the extracellular enzyme metrological characteristics of soil microbial cells in the O layer and the A layer,it is found that the difference between the O layer and the A layer in the same recession zone is significant.The results showed that withdrawal years and soil layers had important effects on the metabolic characteristics of microorganisms.In soil of layer o and layer a,microbial c limitation and p limitation are also significantly negatively correlated.(3)Environmental factors such as shrinking years,water content and p H play an important role in limiting soil microbial nutrients.In glacier retreat area,retreat years and soil layers have significant effects on soil p H,soil water content,soil nutrients(except total phosphorus),microbial biomass elements and extracellular enzyme activities.C:N and C:P of plant roots are significantly positively correlated with shrinking years and soil water content,while are significantly negatively correlated with soil p H.There is a significant correlation between plant root nutrient content and soil nutrient,soil microbial biomass and microbial nutrient limitation.The measurement ratio of extracellular enzyme and the element ratio of microbial biomass are greatly influenced by soil p H,soil water content and soil nutrients(except total phosphorus).