SPECIES-CLIMATE RELATIONSHIPS OF 10 DESERT PLANT SPECIES AND THEIR ESTIMATED POTENTIAL DISTRIBUTION RANGE IN THE ARID LANDS OF NORTHWESTERN CHINA
西北干旱区10种荒漠植物地理分布与大气候的关系及其可能潜在分布区的估测

We choose the arid land of northwestern China as our study area because of its extensive area, specific geographical location, dry climate, varied topography, vulnerable ecosystems and long-term human disturbance, as well as the existence of current conflicts between economic development and environmental protection. Based on the literature, we choose ten desert species with clear and relatively accurate geographical distribution ranges to model their distributions:Anabasis brevifolia, Atraphaxis frutescens, Calligonum mon-golicum, Ephedra przewalskii, Gymnocarpos przewalskii, Haloxylon ammodendron, Haloxylon persicum, Ka-lidium cuspidatum, Salsola laricifolia, and Sympegma regelii. The quantitative relationship between each species distribution range and climatic factors was analyzed. The central and maximum potential distribution ranges of the 10 species were estimated and compared to their actual geographical distributions. Results showed that the mean value, standard deviation, maximum and minimum Holdridge' s annual biotemperature, annual precipitation and potential evapotranspiration ratio of the 10 desert species reflected typical characteristics of desert climates and were in good agreement. The calculated central distribution ranges were in good agreement with a species' actual distribution range, but there were differences among a species' s maximum potential distribution and actual distribution due to three major factors:1) The uncertainties associated with a species current distribution and lack of accurate climate data restricted the accuracy of the species-climate relationships and human impacts have altered the actual distributions of these desert species;2) The maximum potential dis- tribution area was estimated using the maximum and minimum climate values of species, which is less accurate than the potential central distribution range estimated by the mean climate and standard deviation; and, 3) The estimated potential range was calculated based on species-climate relationships only. Other environmental factors, such as soil, geology and topography, which also influence species distributions, were not considered.