Abstract: Gymnocarpos przewalskii is an endangered xerophytes distributed in the desert regions of northern China. In this investigation, based on the 2×2 contingency table, 50 quadrats were set in the south and the north district of Anxi Extra-Arid Desert National Nature Reserve respectively. In order to study the community stability and interspecific association between G. przewalskii and its associated species. M.Godron's method, variance ratio (VR), χ²-test, association coefficient (AC), point correlation coefficient (PPC), Ochiai index (OI) and percentage cooccurrence (PC) was employed in this study. The results showed that: positive association between G. przewalskii and its associated species were more pronounced than negative association both in northern (VR>1,W>χ²_(0.05,N)) and southern district (VR>1,W<χ²_(0.05,N)), but only southern district had reached significant level. G. przewalskii is significant positive associated with Ephedra przewalskii, Artemisia desertorum and Zygophyllum xanthoxylon and significant negative associated with Nitraria sphaerocarpa in northern district. However, in southern district, there were no significant negative associated species and Ephedra przewalskii is the only species which significant positive associated with G. przewalskii. The community stability in northern district was better than south though the ratios of cumulative inverse of species number to cumulated relative frequency were distinctly different from 20/80 in both of the two districts, which indicate instability. In conclusion, few species had significant positive association with G. przewalskii in extra-arid region. Therefore, the population of G. przewalskii tend to be independent and the community was still in unstable state.

Key words: Gymnocarpos przewalskii, interspecific association, community stability