Soil Extracellular Hydrolase Activities In Typical Vegetation In The Zoige Plateau And Their Response To Controlling Ecological Factors

Soil extracellular enzymes is the floorboard of the catalytic functional protein in soil,which is involve in almost all biochemical processes in the soil and ecosystem carbon,nitrogen,phosphorus and other important restrictive link in material cycle.The activities of extracellular hydrolytic enzymes,such as ?-glycosidase,?-N-acetyl amino glycosidase,?glycosidase and cellulose,can be characterized the decomposition rate of organic matter in soil,with evaluation indicator of soil quality.Therefore,it is of great significance to study the characteristics of soil hydrolytic extracellular enzymes,analyze the relationship between hydrolytic extracellular enzymes and ecological factors,and reveal the influence of vegetation change on soil ecosystem function in the Zoige plateau.Located in the eastern margin of Qinghai-Tibet plateau,the Zoigei plateau is an important marsh area in China and a sensitive area for global climate change.Affected by the natural and human economic production activities,the vegetation degradation and the reverse succession of the swamp occurred in the Zoige plateau,which had an important and adverse effect on the biochemical cycle of the swamp soil.However,there is a few evidences on the change trend of soil extracellular enzyme activities and its response to ecological factors in Zoige alpine wetland ecosystem.Study area in this research was selected the Ruoergai county(Zoige national wetland nature reserve core area,Flower lake),Maqu county(Lanzhou university alpine meadow and wetland ecosystem research station,Azi station).Study area regard the perennial flooded area as the center,the moisture gradient,combine with the typical plant species to determine the ground vegetation types.The typical swamp vegetation of Flower lake(perennial water R1),bog meadow 1(R2),bog meadow 2(R3),meadow(R4)and Azi station swamp(perennial water M1),bog meadow 1(M2),bog meadow 2(M3),meadow(M4)0-20 cm of soil is collected from July to early September,2018.The soil hydrolyz extracellular enzyme activity and soil physical and chemical properties were analysis by conventional methods.The characteristics of soil biomes were analyzed by Illumina MiSeq sequencing technology.The main results are as follows:(1)characteristics of soil hydrolyze extracellular enzymesThe results show that the variation trends of extracellular enzyme hydrolytic activities,?-glucosidase,?-N-Acetylglucosaminidase,?-glucosidase,cellulose in the test area are basically the same.The activities of extracellular hydrolytic enzymes in the Huahu study area show a decreasing trend with the decrease of soil water content.Except for the activities of ?-glucosidase and ?-N-Acetylglucosaminidase in R1.The activities of extracellular hydrolytic enzymes in September is lower than that in July.The activities of extracellular hydrolytic enzymes in Azi station are also decreased with the decrease of soil water content in July.However,The activities of extracellular hydrolytic enzymes in the swamp meadow soil is higher than that in marshes in September,and the activities of ?-glucosidase and ?-N-Acetylglucosaminidase and cellulase in the swamp meadow soil in September are higher than that in July.The results of Two-way ANOVA analysis show that The activities of extracellular hydrolytic enzymes are significantly different among different vegetation types(p<0.05),and it decreased with the change of the evolutionary gradient of marshes > swamp meadow > meadow.(2)effects of major soil ecological factors on soil Extracellular hydrolasesThe results of RDA(Redundancy analysis)show that the activities of extracellular hydrolytic enzymes are significant positive correlate to the relative abundance of Deltaproteobacteria Acidobacteriia Subgroup.22 and KD4.96 and Fibrobacteria belong to soil microbial community.At the same time,the results of linear regression analysis show that the activities of extracellular hydrolytic enzymes are positively correlate with soil organic carbon content(%)and soil total nitrogen content(%).There is also a significant negative correlation with soil bulk density.(3)According to the results of ranking the importance of 11 ecological factors,the most import three factors affecting the activity of ?-glucosidase are soil bulk density,soil organic carbon content(%)and the relative abundance of Fibrobacteria.Soil bulk density,soil organic carbon content(%)and the relative abundance of Acidobacteriia are the most important three factors of the effect on the activity of ?-NAcetylglucosaminidase.The soil organic carbon content,soil total nitrogen content and the relative abundance of Deltaproteobacteria are the most important three factors of the effect on the activity of ?-glucosidase.The most important three factors of the effect on the activity of cellulase are soil organic carbon content,soil bulk density and soil total nitrogen content.In summary,soil bulk density and soil organic carbon content(%)have the greatest impact on soil extracellular hydrolases,followed by the relative abundance of soil microbial community,and the weakest impact of soil eukaryotes community.The results of Partial redundancy analysis(pRDA)show that soil bulk density,soil chemical properties and soil biological factors explained 63.90% of the change of soil hydrolase activities.The main chemical properties,soil biological factors and soil bulk density explained 42.74%,46.24% and 55.45% respectively.And the soil biological factors explained 1.3% together with the soil main chemical properties;soil main chemical properties 11.7% together with soil bulk density;soil biological factors explain 2.8% together with the soil bulk density;three part of the ecological factors co-explain 32.3% of the enzyme activities change.Soil hydrolase activities are mainly affected by soil bulk density and soil chemical properties,while soil biological factors are slightly less affected.