| Seabuckthorn is a few of tree species that can grow in zones of forest, forest steppe and typical prairie on the Loess Plateau. Seabuckthorn is a main tree species of conserving soil and water, improving ecological environment on the Loess Plateau, especially its semi-arid loess hilly region. However, if the inferior conditions such as lack of soil water, severe loess of soil and water, scurviness ecological environment can restrict the sustainable development of seabuckthorn stand? What is the main pattern of vegetation construction of seabuckthorn in the semi-arid loess hilly region in the future? These are important problems that should be solved in the current construction of ecological environment urgently. Aimed to the above problems, the systematic studies on hydrological effect of seabuckthorn stands in Zhifanggou watershed belonging to semi-arid loess hilly region. The main results are as follows:1. Hydrological effects of canopy and litter layer of seabuckthorn are remarkable. Annual intercepting rate of canopy of 6~10 ages sebuckthorn stands on rainfall is 5.9%, the rate has a power correlation with the age and canopy density. Litter layer of 5~10 ages seabuckthorn stands can hold 0.5 8-1.19mm rainfall, its maximum hold capacity of rainfall has a remarkable power correlation with canopy density and accumulation. Transpiration intensity of seabuckthorn has relationship with soil moisture condition. Daily change of transpiration intensity is single apex curve with enough soil water and double apices curves with lack of soil moisture. Monthly change curve of transpiration intensity in growing season is single apex type and its mean value is 0.658 g/g.h. Consumption of transpiration is the lowest in May and the highest in July in the growing season.2. To cover soil with litter can increase the capability of soil infiltration and soil anti-scourability in horizon. Rate of infiltration of seabuckthorn stand is larger than barren slope, its difference is decreasing with infiltration time. Mean infiltration rate of seabuckthorn stand has relationship with litter layer covering soil and rainfall intensity. Litter coverage of litter layer can increase mean infiltration rate of soil. Soil erosion in. the stands won't occur when the thickness of litter layer covering soil is above 2cm. Soil anti-scourability in seabuckthorn stand is better than barren slope, which has relation with distribution of the root (^Imm). Soil anti-erodibility of seabuckthorn stand in horizon is better than the lower soil layer and it increases with seabuckthorn age.3. seabuckthorn stand has remarkable effect on reducing runoff compared with barren slope. Its effect increases along with seabuckthorn age. The effect on reducingrunoff increases obviously in 4 ages. Runoff is only 2.74t/hm2 and is almost nonexistent in 10 ages seabuckthorn stand. Depth of runoff in seabuckthorn stand has a positive correlation with I30 and rainfall. The stand of seabuckthorn after cutting still has remarkable effect on reducing runoff, which increases gradually along with the years of cut.4. Seabuckthorn stand has remarkable capability on soil and water conservation benefits. The soil erosion modulus is only 20.11 t/knr.a in 4 ages. Slope erosion of the stand will stop after 6 ages. Compared with barren slope vegetation, the mixed stands with seabuckthorn also have remarkable effect on reducing runoff and soil erosion modulus and are lower than that in seabuckthorn stand. Mixed stand of seabuckthorn and little leaf poplar has better soil and water conservaton benefit than mixed stand of seabuckthorn and pine.5. When there is more plentiful rainfall in a year, the change of soil moisture of seabuckthorn stand in the growing season is as follow. Soil moisture of below 100 cm depth is higher in the earlier period (April) of growing season. Soil moisture in deep layer is used more in May and its value is the lowest in the growing season. In period of July to September, soil moisture in the layer of 0-100cm depth has p...
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