Study On Water Relation Of The SPAC System Of Haloxylon Ammodendron In Kubuqi Desert

Discuss on relationship of the water-using mechanics and dynamic metamorphose of plant communities of Haloxylon ammodendron and sustained development of plant communities from the SPAC system. The study are shown that the disturbance including over-grazing, over-cutting and over-reclamation are the main predispose case for desertification expansion and vegetation degeneration, whereas protecting natural vegetation and establishing artificial vegetation are main methods to make desert shrink and to promote vegetation restoration. The plants' progressive succession is beneficial for improving the reversion of desertification process.The temporal and spatial distribution pattern of soil moisture is different in Haloxylon ammodendron plant communities of the research area. From up to down, the spatial distribution of soil water content can be divided into low value layer with lower soil moisture, middle layer that is active soil moisture layer with higher soil moisture and severe fluctuation, relative stable soil moisture layer with highest soil moisture and small fluctuation.The seasonal change of soil moisture can be divided into three periods that are showing as follow: weaken dehydration period (April-May), consumptive period (June-August) and slow restorable period (September-October). The distribution of dry and wet season of the soil is different with dry and wet season of atmosphere precipitation. Soil water movement is mainly influenced by site type, vegetation and atmosphere precipitation.Daily and seasonal variations of dominant plant species transpiration rate are distinct in the research area. Research on seasonal variations rules of daily development of transpiration rate of some plant species, which can be divided into three types shown as following: single-peak type, double-peak type and mixed type. The daily variations are different in different reason, but basically showing as following: the double-peak type appears as the transpiration rate is high and the single-peak appears in other time-interval.Haloxylon ammodendron by man grown two, three and four year and 柠条 are mixed type plant, A.ordosica is double-peak type and Elaeagnusis single-peak type.Study on the transpiration rate and temperature and small stems water content rate of several plant in research area with regression analysis, the results are showing as following: all of these are correlated except the four-year Haloxylon ammodendron, the multiplecorrelation coefficient of A.ordosica with 0.9325 is highest, the next with 0.793 is three-year Haloxylon ammodendron, the correlation of two is up to 0.001. The correlation of two-year Haloxylon ammodendron(except the four-year Haloxylon ammodendron) is 0.426 that is the lowest in these plants and notable in 0.05 level, Elaeagnus and Caragana are both have linear correlation with temperature and have the lowest correlation with small stems water content rate(P>0.05), so it is deleted in regression analysis. The temperature correlation level of Elaeagnus is higher than that of Caragana,on 0.01 level is obvious but Caragana is obvious on 0.05 level.The profit and loss spatial distribution of soil water is correspondence with soil water sever varied layer and root dense distribution, and the seasonal dynamics are closely relative to the plants' phonological season of the vegetation. The soil water profit and loss of every plant communities can be divided into three groups that are high-grade surplus of soil water type (sample a), middle-grade surplus of soil water type (sample b) and low-grade surplus of soil water type (sample c and e).Through the relation of the soil water resource capacity and the stability of vegetation communities, the water stable mechanism of community is clear in the thesis, the evaporating capacity of plant communities in each sample plot is less than precipitation and underground water supply in the same period, which make the soil water keep surplus state in 2004.Therefore, analysis on the stability of vegetation communities and balance of soil water, water as a main eco...