Response Of Dominant Species Of Natural Forage To Environmental Factors In Different Soil Types In Xilin River Basin

Grassland ecosystems have been affected by environmental changes,and the problem of grassland degradation has become increasingly serious.Soil,as a carrier of pasture growth,is a factor that cannot be ignored in the study of pasture growth and environmental changes.This article takes the typical steppe in the arid and semi-arid area-Xilinguole grassland as the research object,and uses principal component analysis and drought index(SPI,CI)analysis methods to identify the main environmental factors and drought conditions of forage growth;Identify the main species in the study area and the dominant species in different soil types based on TWINSPAN classification,species diversity,and niche theory;Using redundant analysis(RDA)path analysis and decision coefficient analysis methods,the species diversity,distribution of major species,and growth of dominant species in different soil types(height,density,above-ground biomass)and environmental factors(precipitation,temperature,water vapor pressure,relative humidity,sunlight,altitude,potential evaporation)were studied;In order to understand the response relationship of dominant species of different soil types in arid environment to environmental changes,and provide theoretical support for the rational use of local soil,animal husbandry management,and protection of grassland productivity and diversity.The main findings are as follows:(1)The results of principal component analysis showed that among the meteorological factors that have a greater impact on vegetation growth are precipitation,average water vapor pressure,average relative humidity,sunshine hours,and average temperature,and the cumulative contribution rate of the overall variance has reached 98.59%.In addition,potential evaporation and altitude also play an important role in forage growth.Comparing the analysis of the drought conditions in the study area with the standardized precipitation index SPI and the comprehensive meteorological drought index CI,it is considered that the results obtained by the comprehensive meteorological drought index are more detailed.Drought has eased in the study area in the past 38 years,with light,moderate and severe drought events occurring 101,57 and 11 times respectively;severe drought events are prone to occur in the spring and summer seasons,especially in summer;In the pasture growth period,the frequency of probability events in Tune,July and August is relatively low.In 2018,there was no drought in the early stage of forage growth.During the rapid growth period(June and July),there was moderate drought.At the end of the forage growth period(August),there was mild drought.(2)The distribution of vegetation growth height,growth density,above-ground biomass,and underground biomass in the study area showed a normal distribution to the right,with the lowest variation in underground biomass(CV=6%)and the highest root-shoot ratio(CV=81.9%),the rest are moderate variation,and the vegetation in the watershed is mainly divided into five community types.The Leaching chestnut soil is rich in species,and the individual species account for a larger proportion of the community in Common chestnut soil.The main species in the study area(top ten)are Leymus chinensis,Salsola chinensis,Stipa grandis,Cares korshinskyi,Cleistogenes squarrosas,Chenopodium glaucums,Foxtail grass,Allium tenuifolia,green bristle grass,and Allium bidentatum.The dominant species in leaching chestnut soil are Leymus chinensis,Cleistogenes squarrosas and Chenopodium glaucums.Among them,Leymus chinensis has strong adaptability to the environment and is widely distributed.The dominant species in Common chestnut soil are Stipa grandis,Cleistogenes squarrosas,and Chenopodium glaucums,among which Chenopodium glaucums has a strong adaptability to the environment and is widely distributed.The dominant species in the red soil are Leymus chinensis,Salsola collina,Stipa grandis,and Cleistogenes squarrosas,among which Chenopodium glaucums is more competitive in resources;The dominant species in other soils are Leymus chinensis,Cleistogenes squarrosas,And green bristle grass.(3)In leaching chestnut soil,the growth height and density of Leymus chinensis are greatly affected by potential evaporation.Altitude has a greater contribution to biomass accumulation.Precipitation has a direct effect on the growth of Leymus chinensis,but it has Weakened;the growth density and biomass of Cleistogenes squarrosas are greatly affected by potential evaporation,and the amount of precipitation can promote the growth of Cleistogenes squarrosas;the growth of Chenopodium glaucum relative to the water requirement is relatively minimal,and the temperature Direct effect is greater.In Common chestnut soil,the growth of Stipa grandis is relatively affected by precipitation,altitude,and temperature;the correlation between precipitation and the growth height and density of Cleistogenes squarrosa is greater,and temperature and evaporation have a greater impact on the biomass accumulation process.With a large contribution,the altitude will restrain its density increase;precipitation and humidity have a certain inhibitory effect on the height growth and biomass accumulation of Chenopodium glaucums,and the direct effect of sunshine on its density is greater.In red sand soil,water vapor pressure and humidity have a greater promotion effect on the density and biomass accumulation of Leymus chinensis,and altitude has a greater impact on its height growth;The relationship is relatively close;during the growth process of Chenopodium glaucum and Potentilla arvensis is closely related to precipitation.In other soil types,precipitation can promote the growth of Leymus chinensis,water vapor pressure has a direct effect on its height,and its density is closely related to sunshine;precipitation,potential evaporation and water vapor pressure have a greater contribution to the growth of Cleistogenes squarrosas,Among them,the direct effect of water vapor pressure on it is relatively large;the amount of precipitation has a certain inhibitory effect on the growth of bristlegrass,and its density is closely related to water vapor pressure and air temperature.