Abstract: Ammopiptanthus is a genus of flowing plants in the legume family, a typical is evergreen broadleaf shrub in the deserts of Central Asia. It is comprised of two species: A.mongolicus and A.nanus. Both are half endemic and relict species in China. In the past decades, most researches were focus on A.mongolicus, studying about its flora distribution, physiology and ecological characteristics, resistance mechanism, while few studies on large-scale comparative of two kinds of range geographic distribution, habitat characteristics are available. Knowing the Ammopiptanthus distribution and habitat characteristics comprehensively and systematically is useful for itsbiological diversity conservation and sustainable utilization. In this study, literature data and field survey data were used to complete Ammopiptanthus geographical distribution, using one-way Analysis of Variance(one-way ANOVA)method to compare the two species of Ammopiptanthus habitat differences, including topography, climate and soil characteristics; The Principal Component Analysis(PCA)method was used to analysis the main factors which affecting Ammopiptanthus distribution. The main conclusions are as follows:(1) A.nanus only grew in Kizilsu Kirghiz Autonomous Prefecture of Xingjiang, and the distribution range was 38°55'-40°9' N, 74° 42'-76°43'E. A.mongolicus mainly distributed in the western of Inner Mongolia, northern of Gansu and Ningxia, and the distribution range was 36°27'-42°01' N, 102°36'-108°49' E. Both of them were discontinuous in geographical distribution, showing strip or block mode.(2)In the growing areas of A.nanus, the altitude range was from 2 100 to 2 700 m, the slope was from 5 to 45 degree, the average annual temperature was from 3.9 to 6.4 ℃, the average annual precipitation was from 148 to 168 mm, the Holdridge biological temperature was 7.7 ℃; the soil was slightly alkaline and the types included rocky soil salinity soil, gypsum brown desert soil, light lime meadow soil and light brown soil. In the growing areas of A.mongolicus, the altitude range was from 990 to 1 900 m, the slope was 3 to 40 degree, the average annual temperature was from 5.2 to 8.8 ℃, the average annual precipitation was from 53 to 252 mm, the Holdridge biological temperature was 9.7 ℃; the soil was alkaline and the types included calcium earth, wind sand, calcareous gray desert soil, gray-brown desert soil, rocky soil and rocky soil salinity. The analysis of PCA showed that the limiting factors of A.nanus distribution were heat indicators, pH, total salt and phosphorus content, while the A.mongolicus are water, humidity, organic matter and total nitrogen content.

Key words: Ammopiptanthus nanus, Ammopiptanthus monogolicus, geographical distribution, habitat characteristics