| This research based on the achievement of water eco-environment and water eco-physiological characteristics of locust(Robinia pseudoacacia) in the gully area of the Loess Plateau. Using the main tree species-locust in afforestation as materials, this paper deals with water physiology, water condition and productivity of locust under different habitats. Our experiment included out-doors experiment and pot experiment. We studied the variation law of soil water in locust woodland, the relationship between soil water and lateral root system of locust, and water physiological ecology characteristics and growth and productivity conditions of locust under the 4 kinds of typical habitats in the gully area of Loess Plateau. The typical habitats are classified that sunny, shade, semi-shade, semi-sunny hillside. Using the locust seedling as materials, we studied water physiology and growth characteristics of seedling in pot experiment. The following results are obtained on the basis of our data and analyses in out-doors experiment and pot experiment.This paper showed the variation law of soil water in twelve-year locust woodland in different growth stages and different soil depth under different habitats. Soil water content among different habitats was better in general rainfall year than plentiful rainfall year. During different growth stages, soil water content was continued depressing in general rainfall year; and SWC was continued increasing in plentiful rainfall year. The vertical change of SWC in general rainfall year showed the tendency of decreased with soil depth, especially in 0~300cm soil depth, and varied little under 300cm soil depth. The vertical change of SWC in plentiful rainfall year showed the same tendency in 0~300cm soil depth, and semi-sunny and sunny hillside were not obviously as shade and semi-shade hillside in vertical change of soil water under 300cm.2. We studied the distribution of lateral root system of locust under different habitats. Fine roots were well-distributed in 0~400cm soil depth under shade and semi-shade hillside, and yet the distribution of fine roots were concentrated in 0~100cm soil depth under sunny and semi-sunny hillside. The level distribution of lateral root system was extensively with lateral root stretching about 8m in one-way under different habitats. The difference of soil water condition was one of the main reasons which influenced the distribution of fine roots under 4 kinds of habitats. The absorptive roots (fine roots) of locust had markedly effect on soil water under different habitats, at the same time, the distribution of lateral root system especially fine roots had also affect on the seasonal change of soil water. The mean soil water contents of 5m depth were tested in different habitats. There are respectively data of 4 kinds of habitats including shade(8.87%), semi-shade(8.06%), semi-sunny(7.62%), sunny(6.96%). There were significant discrepancy between shade, semi-shade semi-sunny and sunny(α=0.01), the difference between shade, semi-shade and semi-sunny was marked(α=0.05), and difference between semi-sunny and sunny was also marked(α=0.05).There were remarkable relationship between the leaf RWC, WSD of locust and SWC under different habitats. The leaf RWC and water potential of sunny's locust kept lower, but the leaf RWC and water potential of shade's locust were higher. The mean of all day Tr of different habitats was ordered in shade> semi-shade> semi-sunny> sunny hillside. The remarkable difference of Tr appeared at 11:00 and 13:00 under different habitats. Remarkable relationship was found between Tr and light intensity, RH and SWC.All these factors have resulted in diversity of biomass under different habitats, the shade was highest and the sunny was lowest. There were remarkable difference between shade and semi-shade, semi-sunny, sunny(α=0.01). The difference between semi-shade and semi-sunny was marked(α=0.05), and the difference between semi-shade and sunny was also marked(α=0.05).Studies on the water physiology and growth c...
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