Distribution Of Soil Enzymes And Soil Microorganism In Peatlands From Different Permafrost Regions In Northeast China

Soil enzymes and soil microorganisms participate in soil biogeochemical cycle of carbon,nitrogen,and phosphorus,which can quickly and sensitively indicate the change of soil fertility and other properties,and can be used to evaluate soil quality and functional diversity.Under the background of global climate change,the degradation of permafrost leads to the change of permafrost continuity,which affects the hydrothermal dynamics and physicochemical properties of the soil surface,and thus has important impact on the soil biogeochemical cycle.Therefore,the present study was conducted in the frozen soil regions with different degrees of fragmentation in Da and Xiao Xing'anling Mountains from the upper soil horizon 0-15 cm and 15-30 cm to analyze the spatial distribution characteristics of soil enzymes and soil microorganisms in different types of frozen soil regions,discuss the relationships between soil enzymes,soil microorganisms and soil physicochemical properties,reveal the microbiological mechanism of feedback from peatlands on permafrost degradation in middle-high latitude,and provide a scientific basis for predicting the impact of future climate warming on permafrost environment.The main conclusions of this study are as follows:(1)There were differences in soil enzyme activities and microbial abundances in different types of frozen soil regions.The abundance of fungi in the upper soil(0-15 cm)and lower soil(15-30 cm)in sporadic island permafrost region was significantly higher than that in discontinuous island permafrost region and continuous permafrost region(P<0.05);The abundance of pmo A in the upper soil,the activities of invertase,?-glucosidase,urease,acid phosphatase,and the abundances of bacteria,b-amoA,and nirK in the two soil layers all showed the highest values in discontinuous island permafrost region;The abundance of mcrA in 0-15 cm soil layer and the abundance of nirS in the deeper soil layer were highest in continuous permafrost region;However,there were no significant differences for the abundance of archaea among three different frozen soil regions(P >0.05).(2)In horizontal space,the activities of invertase,?-glucosidase,urease,acid phosphatase and the abundances of bacteria,fungi,archaea,pmoA,nirS,and nirK showed a decreasing trend from upper(0-15 cm)to lower soil layers(15-30 cm);However,the abundance of mcr A in the lower layer was higher than that in the upper layer;The distribution of soil b-amoA in different types of frozen soil regions were different with depth.(3)There were significant correlations between soil enzymes,soil microorganisms and soil physicochemical properties.Specifically,there was a significant positive correlation between soil invertase and soil moisture content,total nitrogen,ammonia nitrogen,and total phosphorus,and significantly negatively correlated with soil nitrate nitrogen(P<0.05);Soil ?-glucosidase,urease,and acid phosphatase were positively correlated with soil moisture content,total carbon,total nitrogen,ammonia nitrogen,and total phosphorus,and significantly negatively correlated with soil nitrate nitrogen(P<0.05);Soil bacteria,b-amo A,and nirK was significantly positively related to soil pH,total nitrogen,ammonia nitrogen,and total phosphorus,and significantly negatively related to soil dissolved organic carbon(P<0.05);Soil fungi was significantly positively correlated with soil dissolved organic carbon,and significantly negatively related to soil pH,total nitrogen,ammonia nitrogen and total phosphorus(P<0.05);Soil archaea,mcrA was significantly positively related to soil moisture,total carbon,dissolved organic carbon,and total nitrogen,and significantly negatively related to soil nitrate nitrogen content(P<0.05);Soil pmoA and nirS was significantly positively related to soil moisture content,total carbon,total nitrogen,ammonia nitrogen,and total phosphorus,and significantly negatively related to soil nitrate nitrogen(P<0.05).(4)The main influencing factors of soil enzymes and microorganisms were different.Soil inorganic nitrogen and moisture contents played the most important roles in changing soil enzyme activities,with soil ammonia nitrogen content explained 41.6%of the variation of soil enzymes,soil moisture content explained 29.6%,and soil nitrate nitrogen content explained 11.0%.Soil ammonia nitrogen,pH,and total nitrogen contents were the most important variables that affected the abundances of soil microorganisms,which explained the variation by 42.5%,15.9%,and 15.3%,respectively.