Prediction Model Of Plateau Pika Population Density Based On Vegetation And Soil Factors In The Qinghai Lake Basin

Plateau pika(Ochotona curzoniae)is considered as one of grassland pests since it can aggravate alpine meadow degradation in the Qinghai-Tibetan Plateau.The plateau pika is usually distributed territorially and patchily in alpine meadows,which indicates that plateau pika can cause disaster risks in some alpine meadow where plateau pika lives in more fitness.Although the climate and terrain can provide the possibility for plateau pika distribution,where the plateau pika can really live is dependent on the vegetation and soil factors of a region.Therefore,it is important to select the key factors from the vegetation indicators and soil indicators to identify whether a given alpine meadow is potential disaster regions caused by plateau pika.A body of studies have focused on relationship between plateau pika presence and vegetation indicators and soil indicators from alpine meadow,however,these previous studies have paid little attention to key factors,which limits the predict model of population density of plateau pika in the area by using the key habitat factors.The alpine meadow in the Qinghai Lake Basin is a natural barrier to spread alpine meadow desertification from west to east,and also is a part of the alpine meadow in the Qinghai-Tibet Plateau.The plateau pika is a common small herbivore in this Lake Basin,and considered as the main biological factor that causes alpine meadow degradation.Therefore,this study is to select the key factors from vegetation indicators and soil indicators by simulating the relationships between the plateau pika population density and vegetation indicators and soil indicators from alpine meadow in Gangcha and Gonghe in the Qinghai Lake Basin,and then this study use selected key factors to establish a prediction model for estimating the plateau pika population density.These will provide a decision-making basis for the ecological control of plateau pika in alpine meadow of the Qinghai Lake Basin,and provide a reference for other regions.The main results are as follows:1.The plateau pika population density was highly correlated with vegetation cover,species diversity index,graminoid biomass,and the ratio of palatable plant biomass.With the increase of plateau pika population density,the vegetation cover,graminoid biomass and the ratio of plateable plant biomass decreased at each site.Shannon-Wiener index,Pielou evenness index and Patrick richness index first increased and then decreased from 359 burrows/hm~2 to 1312 burrows/hm~2 in Gangcha site,whereas they increased from 137 burrows/hm~2 to 597 burrows/hm~2 in Gonghe site.However,the plateau pika population density was not highly correlated with plant community height and forbs biomass at each site.2.The plateau pika population density was highly correlated with soil moisture content,water storage,organic matter,organic carbon,total nitrogen and carbon-nitrogen ratio.With the increase of plateau pika population density,the soil moisture content and soil water storage decreased at each site.soil organic matter,organic carbon,and carbon-nitrogen ratio first increased and then decreased from 359 burrows/hm~2 to1312 burrows/hm~2 in Gangcha site,whereas they increased from 137 burrows/hm~2to 597 burrows/hm~2 in Gonghe site.Soil total nitrogen decreased from 359 burrows/hm~2 to 1312 burrows/hm~2 in Gangcha site and first increased and then decreased from 137 burrows/hm~2 to 597 burrows/hm~2 in Gonghe site.However,the plateau pika population density was not significantly related to soil bulk density and porosity,and there was a significant linear negative correlation with soil pH in Gangcha site.Whereas,the plateau pika population density showed a positive correlation with soil bulk density,a linear negative correlation with soil porosity,and no significant correlation with soil pH in Gonghe site.3.This study selected the vegetation cover,Patrick richness index,total soil nitrogen,and soil carbon-nitrogen ratio as key factors that determine plateau pika population density in alpine meadows of the Qinghai Lake Basin.The results of PCA and MDS showed that the key factors were different between two sites.Soil organic matter and soil pH were the key factors determining the plateau pika population density in Gangcha site,whereas vegetation cover,soil water content,soil organic matter,soil bulk density,soil total nitrogen and soil carbon-nitrogen ratio were the key factors in Gonghe site.However,the overall analysis results of two sites showed that vegetation cover,Patrick richness index,total soil nitrogen,and soil carbon-nitrogen ratio were the key factors that determine the plateau pika population density in the Qinghai Lake Basin.4.This study used the selected key factors to establish the predict model of plateau pika population density in the Qinghai Lake Basin.Patrick richness index was removed in the process of selection model.Such,vegetation cover,soil total nitrogen,and soil carbon-nitrogen ratio were used to establish a prediction model of the plateau pika population density in the Qinghai Lake Basin,and its equation was X=-88.613 Cover-191.144 TN-19.494 C/N+9777.88(R~2=0.837),where X was plateau pika population density,Cover was vegetation cover,TN was soil total nitrogen content,and C/N was soil carbon-nitrogen ratio,which provides a basis for estimating some alpine meadow where is potential disaster-risks caused by plateau in the Qinghai Lake Basin,and also provides a reference for other similar areas.