| Water is a key factor to restrict vegetation rehabilitation and reestablish in arid andsemi-arid on Loess plateau .In the condition of limited precipitation, Vegetation community density very strongly affects its normal growth by adjusting soil moisture. Based on the theory of the Soil-Plant -Atmosphere Continuum, individual-tree growth status of different stand densities have been studied to calculate various stand water use considering local weather condition, and to determine rainfall-environment capacity and acceptive stand density for water carrying capacity, and more to provide some reference to adjusting and controlling evapotranspiration measurement. For getting above research intention, some methods were adopted such as fixing position observation, the whole stand investigation, quantitative analyzation etc, the following results as follows:(1) based on the varioust stand growth status, individual-tess growth were analyzed and a regression equation between stand density and stand age was established as V=0.0015xN1-1.0593xT1.2241, V-annual increasing of individual-tree volume, N-stand density, T-stand age(2) rainfall has a direct influence on various growth parameters of stand, during the growth prophrase the tree height increment was greatly infected, the current growth of diameter and volume was closely relation to last year rainfall, and the more stand density, the early stand caducity age.(3) the regression equation on water and individual-tree growth was established .V=0.0012xN-1.07770xp0.0269xt1.23 (4) the individual-tree biomass data was analyzed, the biomass can be well simulated with a quadratic polymonial expression.(5) a water-productivity model was established by individual-tree data of biomass M=Mb+Me=0.071xed+0.023xN~1184xP0.082, d-the annual increasing of individual diameter.(6) relation diagrams of rainfall-stand density that can be used to instruct forestry management on the basis of definite precipitation were established.
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