| Loess Plateau is one of the fragile environments. The economic development is restricted seriously by arid and water and soil run off. It has been proved that the recovery and construction of plants in this region is the basic measure of water and soil conversation,environment construct and the development of agriculture, forestry, stock raising,However, the contradictions among forests, plants and soil water are obviously in the process of plants revive because of water shortage. Therefore, how to utilize the water and increase the cover rate of pants is the urgent thing we must be do. This article studied the effects of the main anti-drought techniques on the physiological and ecological mechanism of the survival and growth of seedlings based on the climate and the water disparity and plant demand in Loess Plateau. That the water distribution and the survival and growth of young forest in different site condition of sloping field in Loess Plateau was studied. Covering measures with the plastic film or hasty to improve the soil water condition of root environments and the use of soil water. Catchments in sloping field can improve the use of precipitation. The use of chemical preparation can improve the soil water condition of root environments and the seedlings' bibulous capacity. The result was follows:1．The effects of soil water distribution in different site on the seedlings' survival and growth. The results showed that soil water distribution mainly depend on the gradient,exposure,and slope position. There is different survival of seedlings in different site condition. Seedlings have different strategic growth and biomass allocation in different site condition. The3-year Calophaca korshinskii Kom shoot to total biomass ration is 71.8% in lower shady slope, 67.8% in upper shady position, and 62.3% in solar position . The Locust and Wild Apricot' leaf area index in shady slope are lower than that in solar position; but the leaf water deficit show inverse tendency. Amorpha fruticosa L. total area to stem area ration, and leaf/stem ration are higher in lower shady slope than that in upper shady position. Furthermore, there are different modules in different site condition.2．Terrace made in slope field can improve the use of precipitation to improve survival and growth of seedlings. The result was proven that the terrace has higher mass flow than that of slope; and the smaller row spacing the bigger the effect contributing to mass flow, the seedlings' viability and growth. 3．Comparing the effect of fighting a drought between catchments and coving measures. The research of seedlings' growth and the climate of Loess Plateau prove the fact that the combination of coving and catchments can give the better effect in the afforestation.Because in the first half of the year in Loess Plateau The climate is windy and arid ,coving measure is better than that of catchments ;and the ranginess become convergence in the last half , accordingly,catchment measure is better.4．Chemic preparations exert effect on improving seedlings' ability of fighting a drought.Rooting powder (ABT) and Super Absorbent Polymers can improve the growth of height and diameter of Robinia pseudoacacia and Amorpha fruticosa L) through different ways. Rooting powder (ABT) can improve the throws of plant by facilitating rooting ,especially the side root. Super Absorbent Polymers fulfill it 'function through resisting the water transpiration of leaf .
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