A Study Of Ecological Characteristic Of Eremophytes In Minqin

The Minqin County is a serious desertification region where environment change had undergone large area of water to halophytic meadow by Han dynasty to that late of the time and desert of now. At present, ecological environment will be degrading that large natural vegetation and artificial shrubbery of fixed sand, which was planted in 1960s to 1970s, were largely withered, thin and died. The major types of vegetation were choose to study location vegetation and its action by characteristic of phytocoehosium and that of relationship with environment, niche of the major constructive species, healthiness of dominant species and plant phonological.(1) The climate belongs to the typical desert in Minqin where shrubs are the major role of desert vegetation with coverage of only 5%～15%. It was obvious that canopy of vegetation and itself change and had been degenerating with fluctuant cause of annual precipitation in Minqin. In common years, upside of the shrubs, such as Nitraria tangutorum, Haloxylon ammodendron, Artemisia arenaria etc., must be died away; or died all of them in years of that annual precipitation distributing was exceptional. Therefore, it positively decreased that of the canopy of vegetation and height of shrubs in some years. It was obvious different that the different communities distributed in state of landform and soil. The Nitraria tangutorum existed on mound of Nitraria, with soil moisture content of 1.4～2.0% at layer of 0～30cm. The Ephedra przewalskii distributed only at flat with gravels and far fewer soil moisture content of 0.8% at layer of 0～30cm of soil. The Artemisia arenaria distributed at semi-fixed dunes, shifting dunes and the flat which was covered by moving sands and with the soil moisture content of 0.9～1.7% at layer of 0～30cm. The plants answered the precipitation on change of soil moisture content, which was affected by the dimension of granule of soil, and fine sand sensitively answers precipitation. It was positive relation that height of dominant plants responds precipitation during the last ten-days of July to the last ten-days of September. There was positive relation with the average canopy of herbage and the precipitation in the last ten-day of May to the last ten-days of July. The annual precipitation affected the total canopy of community. Its effect was more obvious which the precipitation in the last ten-day of May to the last ten-day of September compared with annual precipitation.(2) There was a great difference of breadth of ecological niche amount structure plants, and similar proportion of niche was quite small among plants, which was enslaved result in desert habitat, also one of the major characteristics of thin desert vegetation in arid environment. The current niche breadth closely associated annual precipitation, and the soil moisture was the key role among influencing factors, such as landform, soil granule, soil moisture and soil nutrient etc. When underground water table reached to about 20m depth, plants could not use it, which shown water was the major competition item of resource among plants. A larger niche breadth of the same species of plant in different communities, the competition differences plants in varied communities were resulted in niche, relative steady landform, soil conditions and various annual precipitation.(3) An analyzed result of healthy sequence of domination plant shown the healthiness of the same community was better on semi-fixed dune and shift dune than that of on fixed dune. The healthiness condition of community was obviously affected by healthiness of domination plant. The analysis of sensitive degree of healthy sequence was not only used to check security of analyzed conclusion, but also it open out the action and condition of roles who were shown by distinguish indexes in community. It was capable to shown out affected factors that the distinguish index was divided into index of dominant species and auxiliary species, which was more proper to natural characteristics of community, meanwhile the healthiness condition would be studied by first grade analysis standard on the healthy of dominant species and companion species. The analyzed result of weight as sensitive degree of domination plant and auxiliary species for showing the weight communities of Nitraria tangutorurn and Artemisia arenaria was more than 0.65, 0.60 of Tamarix rarnosissirna, and 0.50 of Haloxylon ammodendron, but the healthy sequence was not changed.(4) The 48 participations of plants, which were representations in Minqin region, were selected and comparing with to study phonological characteristic. The first step that 9 phonological types of 48 plants were analyzed by system clustered on phonological data from 1985 to 2004; as well the result was classified by mesophyte, xerophyte, psammophyte. The studying result shown rank changing of many years of the some phonological time increased scope in sequent rank from mesophyte, xerophyte to psammophyte; the rank from mesophyte to xerophyte was bigger than that of mesophyte to psammophyte, and phonological time put up gradually delaying direction. The winter is far longer, as well as a number of days of summer, whereas the autumn is the shortest in location. It is more days that frequency is distributed in the number of phonology in spring and autumn, and with few acting relatively days for plant.