Affecting Factors Of The Population Density Of Rodents In Different Grassland Habitat And The Causes Of Coexistence In The Same Area

Rodents play an important role in the structure and function of grassland ecosystems.The influence of environmental factors on the population of rodents is an important issues of population ecology.The response of rodents to changes in different environmental factors reflects their different options of micro-habitat.The coexistence mechanism between the same domain and different species is an important research content of community ecology.Therefore,this study thoroughly explored the relationship between environmental factors in different grassland areas and rodent population density,as well as the coexistence patterns and causes of rodents in different grassland habitats,and provided information for revealing the influencing factors of rodent population density and the coexistence mechanism between homogenous and heterogeneous species.Reference and enrich the theory of population ecology and community ecology and species coexistence.This study included two experiments:Experiment 1: In May(spring),July(summer)and September(autumn)from 2013 to2019,the climate conditions,soil conditions,vegetation conditions,and rodent species and numbers were monitored in the Alax desert of Inner Mongolia.The geographic detector model was used to analyse the relationship between the number of rodents and environmental factors,and the results showed that:(1)Different species of rodents in desert had different choices of micro-habitats in different seasons.This was because different species have different adaptability and sensitivity to environmental factors,and the influence of environmental factors on different species of rodents varied among seasons.(2)Different rodent species showed similar adaptability to environmental factors.On the one hand,it showed adaptability to moisture factors(precipitation and evapotranspiration)and temperature(average temperature and average temperature extremes),that was,they had a certain degree of adaptability to moisture and temperature.The most suitable range,the population density was the maximum in this range,and this most suitable range differs among different species.On the other hand,the main factor that regulated the population of rodents was its own population density,which was the result of the combined effect of density-dependent factors and density-independent factors.(3)Among the causes of coexistence of rodents in the Alxa desert,abiotic factors were the prerequisite factors that determine the structure of the rodent community,and the composition of the rodent community was the main factor to maintain the coexistence model.The coexistence model was that in order to face the complex relationship of coexisting species and reduce competition,different rodent species had differences in the use of habitat resources,and the selection of micro-habitats had differentiated,and coexistence can be achieved.Experiment 2: In May(spring),July(summer)and September(autumn)from 2013 to2016,the climate conditions,soil conditions,vegetation conditions,and rodent species and density were monitored in the typical steppe of Hulunbuir in Inner Mongolia.The geographic detector model was used to analyse the relationship between the number of rodents and environmental factors,and the results showed that:(1)Different species of rodents in typical steppe had different choices of micro-habitats in different seasons.This was because different species have different adaptability and sensitivity to environmental factors,and the influence of environmental factors on different species of rodents varied among seasons.(2)In typical steppe,different species showed similar adaptability to environmental factors.On the one hand,they were represented by moisture factors(precipitation,evapotranspiration,and average relative humidity),temperature(average temperature and extreme temperature),and soil temperature all affected rodents.But different rodent species had different responses to changes in these factors,that was,they had a certain optimal range for moisture and temperature,within which the population density was the maximum,and this optimal range existed difference among different species.On the other hand,the main factor that regulated the population of rodents was its own population density,which was the result of the combined effect of density-dependent factors and density-indepedent factors.(3)Among the reasons for the coexistence of rodents in the Hulunbuir typical steppe,abiotic factors were the prerequisite factors that determine the structure of the rodent community,and the composition of the rodent community was the main factor to maintain the coexistence mode.The coexistence model was that in order to face the complex relationships of coexisting species and to reduced competition,the choice of micro-habitats had differentiated between different rodent species,and coexistence can be achieved.A comparative analysis of those results of the above two regions,and the conclusions were drawn:(1)In desert areas,the population density of Meriones meridianus was mainly affected by intraspecific competition and interspecific competition with Dipus sagitta;the population of Dipus sagitta was mainly affected by intraspecific competition and interspecific competition with Meriones meridianus;the population of Phodopus roborovskii,Allactaga sibirica and Spermophilus alaschanicus were mainly affected by intraspecific competition.(2)In typical grassland areas,intraspecies competition and interspecific competition with coexisting rodent species were the main reasons for population density changes of Spermophilus dauricus,Phodopus sungorus,Cricetulus barabensis,Ochotona daurica.(3)In desert and typical grassland areas,abiotic factors were the prerequisite factors to determine rodent community structure,and rodent community composition was the main factor to maintain coexistence pattern.The coexistence mode in desert was that in order to face the complex relationship of coexisting species and reduce competition,different species had differences in the use of habitat resources,and the selection of micro-habitats had differentiated,so that coexistence can be achieved.The coexistence pattern in typical steppe was that in order to face the complex relationships of coexisting species and to reduce competition,the choice of micro-habitats had diverged,and coexistence can be achieved.Although the coexistence patterns in the two habitats were all related to the micro-habitat selection of different species of rodents,the species in the desert with more fragile habitat showed more obvious differences in resource utilization.