Abstract: Based on the data of locating observation on desert shrub from 1994 to 2000 in Xilingaole area of Alashan League in Inner Mongolia,the relevance of population densities of five desert shrub species to six water-thermal factors,including average air temperature,average maximum air temperature,average minimum air temperature,precipitation and ground temperature of 0-20cm and 20-80cm,was analyzed by using the gray relevant analysis on six time intervals,such as annual period,growth period,flourishing growth period,last annual period,last growth period and last flourishing growth period.The results showed that: 1).The relevance of the precipitation during the last flourishing growth period to Nitraria sibirica and the relevance of the precipitation during the last growth period to Zygophyllum pterocarpum were more significant,while the relevance of the precipitation during the growth period of the same year to other three species was more significant.2).There existed the following highly significant relevancies: the annual daily average air temperature and annual daily average minimum air temperature of the same year to Reaumures soongorica and Oxytropis aciphylla;the annual average ground temperature(0-20cm)and annual daily minimum air temperature of the same year to Caragana brachpoda;the daily average minimum air temperature and the average ground temperature(0-20cm)during the growth period of the same year to Zygophyllum pterocarpum;and the daily average air temperature during the growth period and the average ground temperature(0-20cm)of the same year to Nitraria sibirica.3).Except for Zygophyllum pterocarpum,the relevance of precipitation to desert shrubs was higher than thermal factors.But daily average minimum air temperature might be a basic climate factor for the fluctuation of desert shrub population,as the desert shrub had a higher minimum temperature threshold for the growth.As one of dominant species of desert shrub,Zygophyllum pterocarpum had a strong adaptability to the arid climate with high temperature and rare precipitation.

Key words: Desert shrub, Desert shrub, Water-thermal factor, Population density, Degree of grey relation