关键词: 绵刺, 群落, 生理生态学, 濒危原因

Abstract: Results based on research and investigation showed:(1) Potaninia mongolica Maxim inhabits in the sand and gravel desert area in north of Hexi corridor,where altitude is 1 2001 800 m;precipitation is 6080 mm;and soil is g ray-brown desert soil.The distributing area is about 48 402.74 hm².(2) In Gansu province,Form.Potaninia mongolica Maxim are composed of 48 species that belong to 37 genera and families,and can be divided into 5 types and 15 groups.Among them,the gravelly sandy desert distribution elements are in the ascendant(45.83%);the central Asia distribution grassland elements are in second place(35.42%);the ancient Wed distribution elements also occupied a certain proportion(20.83%).(3) Its water potential is relatively low;fixed water,ratio of fixed water to free water,transpiration rate are all quite small;critical saturation deficiency,water use efficiency are very big;photosynthesis rate is relatively large.For its leaf is thin,ratio of fence tissue to sponge tissue is small,its main veins and vessels are not strong.As above of all,it has quick growth,strong power to absorb water,weak power to resist dehydration and to tolerate drought.The mostly characteristics o f its fighting drought is avoiding drought by dormancy.As a result,it is considered that it is not really evolved in xerophyte,but come of mesophyte.(4) It adapts to drought,endures infertility,and likes partial alkaline environment.In all of ecological factors,it is of most susceptibility and dependence to soil moisture.Meanwhile,it has special requirement for the soil texture,the soil salt content and pH,but not strict to the soil organic and nutrient.(5) Its endangered process may be divided into two phases.The first is the Quaternary,in which violent variance of the natural environment,severe drought of the climate and serious denudations are the most mainly and directly endangered reasons.The second is the modern times and the contemporary age,in which over grazing,overtaking underground water,hewing brushwood are the most mainly endangered reasons.

Key words: Gansu, Potaninia mongolica Maxim, community, physiological ecology, endangered reason