The Research On The Interrelationship Between The Vegetation And Water Resource In Ulan Buh Desert

In the present essay the relationship between the plants and water resource was studied based on the characteristics of the main plant physiological ecology, vegetation and water equilibrium in the northeast of Ulan Buh desert in 2003-2005. The main results were as follows:(1) The research indicated that the soil space heterogeneity was less below 20 cm in the soil depth by measuring bulk density of soil and the field capacity, that the saturated hydraulic conductivity of sandy soil (12.85cm/h) was greater than clay (0.43cm/h), and that the relationship between soil water potential and water volume content, and that between the conduct resistance of the soil evaporation and water volume content could be both shown in the equation y=ax^–b.The vegetation coverage of fixed dune, semi-fixed dune and shifting dune was 33.1%,24% and 6.3% separately. The coverage of Nitraria tangutorum, Ammopiptanthus mongolicus,Artemisia ordosica and Haloxylon ammodendron was more than 80% of vegetation coverage. The rootage of the four plants was distributed above 60cm in soil depth, the rootage biomass in proportion to the total biomass of Nitraria tangutorum and Artemisia ordosica were more than that of Ammopiptanthus mongolicus and Haloxylon ammodendron.In the tested area the water resource was poor and it could mainly be used by the plant from rainfall and soil water. The infilatration depth of rainfall was less than 80cm. The relationship between the soil water storage and soil depth was linear, exponent,"s"function and power function. The annual change of soil water content, biomass and leaf area index was less in normal environment condition.(2) The relationships between plant photosynthetic rate, transpiration rate, stomatal conductance, and other physiology indexes and light intensity or water potential could be expressed by the equation y=a+b(1-e^-kx) (y stood for physiology index, x stood for light intensity or water potential). The water potential compensation point (MPa) of net photosynthetic rate of Nitraria tangutorum (-4.07) was more than that of Ammopiptanthus mongolicus (-4.44). The maximum net photosynthetic rate (μmolm^-2s^-1) is Nitraria tangutorum(9.45)>Haloxylon ammodendron(6.38)>Artemisia ordosica(5.29)>Ammopiptanthus mongolicus(4.06); the maximum transpiration rate (mmolm^-2s^-1) Ammopiptanthus mongolicus (6.76) > Nitraria tangutorum (4.43) > Haloxylon...