The effect of vegetation on soil and water conservation increases with the increase of planting density. At the same time, the degree of soil drought increases with the increase of planting density, and leads to the decline of vegetation or waste resources and then affects the benefit of vegetation on soil and water conservation. However, there is a few research of high-quality sustainable management of easier degraded soil and water conservation vegetation ecosystems. In this paper, the high-quality sustainable management of soil and water conservation vegetation was reviewed. The results showed that the degree of cover of soil and water conservation vegetation increases with increasing density under other things being equal; the canopy interception increases with stand density but there is a peak value of canopy interception. The surface runoff decreases with increasing density with a logarithm relationship; the sediment charge in the runoff increases with reducing density with a logistic relation. There is a limit of soil and water conservation vegetation, which is the cover degree of soil and water conservation vegetation when the existing plant density of indicator species in a plant community is equal to vegetation carrying capacity. When plant density of indicator species in a plant community is more than vegetation carrying capacity, the cover degree of soil and water conservation vegetation is more than the vegetation restoration limit of soil and water conservation vegetation, the plant resources relationship should be regulated based on vegetation carrying capacity to realize high-quality sustainable management of soil and water conservation vegetation.

The effect of vegetation on soil and water conservation increases with the increase of planting density. At the same time, the degree of soil drought increases with the increase of planting density, and leads to the decline of vegetation or waste resources and then affects the benefit of vegetation on soil and water conservation. However, there is a few research of high-quality sustainable management of easier degraded soil and water conservation vegetation ecosystems. In this paper, the high-quality sustainable management of soil and water conservation vegetation was reviewed. The results showed that the degree of cover of soil and water conservation vegetation increases with increasing density under other things being equal; the canopy interception increases with stand density but there is a peak value of canopy interception. The surface runoff decreases with increasing density with a logarithm relationship; the sediment charge in the runoff increases with reducing density with a logistic relation. There is a limit of soil and water conservation vegetation, which is the cover degree of soil and water conservation vegetation when the existing plant density of indicator species in a plant community is equal to vegetation carrying capacity. When plant density of indicator species in a plant community is more than vegetation carrying capacity, the cover degree of soil and water conservation vegetation is more than the vegetation restoration limit of soil and water conservation vegetation, the plant resources relationship should be regulated based on vegetation carrying capacity to realize high-quality sustainable management of soil and water conservation vegetation.

：Red plum apricot is a deciduous fruit tree and the best cash forest in semiarid loess hilly regions. Since 1995, the distribution area of red plum apricot spreads in the most of the water-limited regions, China. The yield, benefits and plantation area of red plum apricot increase dramatically. But along with the growth of red plum apricot tree, soil drying appeared and sometime become sever,which influence the yield，quality and benefits of red plum apricot. At this time, the relationship between the soil water and red plum apricot growth must be regulated on Soil Water Resource Use Limitation by Plant and Soil Moisture Carrying Capacity for Vegetation. However, there are few studies on the regulation theory. In this study, daily precipitation, soil water suctions at different soil water content were measured, and the maximal infiltration depth and the soil water resource use limitation by red plum apricot was estimated. The results show that wilting coefficient varies with soil depth from 7.98 in surface soil to 7.1% in 240 cm soil depth, and the maximal infiltration depth is 290 cm, and Soil Water Resources use limit by red plum apricot is 212.7 mm. When the soil water resource in the maximal infiltration depth is lower than the limit, the relationship between the soil water and red plum apricot vegetative growth must be regulated in Red Plum Apricot plantation for high quality production of red plum apricot.

In the water-limited regions, there is a limit of vegetation restoration because the short of soil water and people’s big need. However, there are few reports on the limit of vegetation restoration. In this study, non-native perennial Caragana shrublands was selected to establish experimental plots with different densities, and cover degree, basal diameter and plant height growth, soil water and precipitation was investigated, soil water supply and soil water consumption at different planting density was estimated and the relationships between planting density and soil water, soil water carrying capacity for vegetation and the potential for vegetation rehabilitation was analyzed. The results showed that the degree of cover increases with increasing density under other things being equal; the canopy interception increases with stand density and both of them is an exponential relation; the surface runoff decreases with increasing density and the relationship between them is a logarithm relationship; the sediment charge in the runoff increases with reducing density and the relationship between them can be expressed by a logistic equation. Although the canopy closure increases and the effect of the caragana forest on soil and water conservation strengthens with increasing density, but there is a limit of vegetation rehabilitation. When the cover degree of Caragana shrublands is more than the vegetation restoration limit, the water-plant relationship should be regulated based on soil water carrying capacity for vegetation to control soil drying and realize high-quality and sustainable development of soil and water conservation vegetation.

Non-native vegetation with high canopy closure can alter the equilibrium relationship between soil water and plant growth into a non-equilibrium relationship leading to soil degradation, vegetation decline and crop failure in the most part of water- limited regions. There is a need for the application of a novel theory in the assessment and the adjustment of non-equilibrium relationships to facilitate the sustainable management of non-native vegetation in the course of vegetation restoration in such regions. Therefore, a novel theory, Soil Water Resources Use Limit by Plant (SWRULP) has been developed. SWRULP refers to the amount of water stored in the maximum infiltration depth (MID) at which the soil moisture content in each layer is equivalent to the wilting coefficient. The wilting coefficient is expressed by the wilting coefficient of indicator plants in a plant community. SWRULP is an index for assessing plant overuse of soil water resources and the estimation of the starting time to regulate the relationship between soil water and plant growth in addition to the selection of the most suitable tree or plant species for vegetation restoration activities. To better understand SWRULP, in the present study, the SWRULP was assessed in a Caragana shrubland and an alfalfa grassland in semiarid loess hilly region. The results showed that the wilting coefficient varied with soil depth, and the SWRULP changed based on site conditions and vegetation type. When the soil water resources were equivalent to the SWRULP, soil water influenced plant growth considerably and caused the discoloration of sclerophyllous plants, abscission, cessation of growth, and soft leaf plant wilt. Under such conditions, the relationship between soil water and plant growth should be regulated based on soil water carrying capacity for vegetation to achieve sustainable use of soil water resource and sustainable management of forest and grassland and utilization, in addition to sustainable development.