Study On Community Biomass And Species Diversity Of Xilingol Steppe

Community biomass and species diversity are two important indicators that reflect the basic characteristics of plant community,and they are the main ways to understand the material cycle and energy flow of grassland ecosystem.Their change pattern affects the stability of grassland ecosystem and restricts the development of social economy.Xilingol grassland is located in the core of temperate steppe in Eurasia,which can acutely reflect the changes of global ecological environment,and deeply study the changes of community biomass,species diversity and the influencing factors of this change.it can provide basic data and theoretical support for the protective utilization of ecological resources,restoration of degraded grassland and reasonable and scientific grassland management in the study area.In this study,using field survey data,through index calculation,canonical correlation analysis,geographic detector and grey correlation analysis,the community biomass and species diversity of Xilingol grassland in 2013 and 2019 and the relationship between them and environmental factors were studied.The results show that:（1）The community biomass and community coverage of Xilingol grassland showed the order of meadow grassland > typical grassland >desert grassland（P < 0.05）.As time goes on,the desert steppe community biomass increased slightly,but the change was not significant,while the typical steppe and meadow steppe community biomass decreased significantly（P < 0.05）.（2）The main life form functional groups of Xilingol steppe were perennial tufted grasses and perennial miscellaneous grasses.The biomass of the two functional groups was meadow steppe > typical steppe > desert steppe.After 6 years of change,the biomass of perennial tufted grasses in typical steppe and meadow steppe decreased significantly（P < 0.05）,and the biomass of perennial weeds decreased,but not significantly.The main ecotype functional groups of Xilingol steppe were xerophytes and mesoxerophytes,and the biomass of xerophytes was the highest in typical steppe,which decreased significantly in typical steppe after 6 years（P < 0.05）.The biomass of medium xerophytes was the highest in meadow steppe,and decreased significantly in meadow steppe after 6 years（P < 0.05）.（3）The plant species diversity fluctuated with the increase of water and the decrease of temperature from west to east,and the change was not significant in different grassland types and two years.The species richness fluctuated from west to east with the increase of water and the decrease of air temperature.there was no significant difference among different steppe types in 2019.The species richness of meadow steppe was significantly higher than that of desert steppe in 2019（P < 0.05）.There was no significant difference in species richness among different years.The evenness was the highest in desert steppe,which changed but not significantly between different steppe types and two years.Compared with 2013,the community similarity coefficient decreased significantly in2019（P < 0.01）.（4）There was a significant positive correlation between community biomass and dryness and multi-year average precipitation（P < 0.01）,and a significant negative correlation with multi-year average temperature（P< 0.01）.But not significant.With the increase of soil total nitrogen（TN）,soil organic carbon（SOC）,soil available nitrogen（AN）and soil available phosphorus（AP）,the biomass of community increased significantly（P <0.01）.With the increase of soil total phosphorus（TP）and soil available potassium（AK）,there is an increasing trend,but it is not significant.With the increase of soil total potassium（TK）,it decreased,but it was not significant.With the increase of soil pH value,it decreased significantly（P < 0.01）.The order of plant life form functional group biomass affected by 12 environmental factors is as follows: annual average precipitation >dryness > SOC > TN > AN > pH > AP > altitude > multi-year average temperature > TK > TP > AK.Among them,the biomass of perennial weeds was most affected by environmental factors,followed by perennial tufted grasses,and environmental factors had little effect on the biomass of small shrubs,semi-shrubs,perennial rhizomatous grasses and biennial plants.The order of the biomass of plant ecotype functional group biomass affected by 12 environmental factors is as follows: annual average precipitation > dryness > AN > SOC > TN > pH > AP > altitude >multi-year average temperature > TK > TP > AK.Among them,the biomass of mesophytes is most affected by environmental factors,followed by mid-xerophytes,and environmental factors have little effect on the biomass of xerophytes and xerophytes.（5）Through grey correlation analysis,it was found that the diversity and richness were greatly influenced by altitude and water conditions,but had little correlation with the average temperature for many years and soil available nutrients.Evenness is closely related to soil pH,altitude,TK and hydrothermal conditions,but not to other soil nutrients.