Ecology Benefits Analysis And Assessment Of Hedgerow System In The Three Gorges Reservoir Area

On the basis of investigation of the current hedgerow configuration and growth status in the Three Gorges Reservoir Area, this paper analyzed and contrasted the soil physical properties, soil and water conservation properties and soil nutrients content in hedgerow systems and soil in steep-land with no hedgerows. Besides, soil physical properties variance, soil nutrients distribution, soil particle distribution and variance of soil anti-scouribility and anti-erodibility in hedgerow systems were analyzed in hedgerow systems, and further, the ecological benefits mechanism including soil physical properties improvement, soil and water conservation, soil nutrients augment and non-point pollution controlling were discussed. Then, index of hedgerow ecological benefits evaluation were established and ecological benefits of different hedgerow intercropping were evaluated. On the basis of hedgerow ecological benefits evaluation, the contracture and configuration of hedgerow intercropping were confirmed and hedgerow intercropping afforestation models were typically designed. Expected to provide the theories and techniques for hedgerow species selection and afforestation in the Three Gorges Reservoir Area. The main results and conclusion of the paper were indicated as follows:(1)The parameters of soil physical properties presented definite horizontal variation at steep lands within, before, and behind the hedgerows, and between the hedgerows. The coefficient of variation (CV) of soil bulk density, soil porosity, moisture content, saturated conductivity and water stable aggregates content were 11.1%,9.8%,17.9%,51.2% and 16.3%, respectively; Soil nutrients content were became higher from between hedgerow steep-land to under and before hedgerows, and declined to after hedgerows. Soil particle distribution were effected signify by hedgerow intercropping, with soil under hedgerows involving tree, grass and shrub species, clay content became higher (by 18.5%, 26.0% and 16.3%, respectively) than soil between hedgerows, while sand content became higher between the hedgerow by 14.2%,16.3% and 12.0%, respectively. Comparing with soil between hedgerows, soil anti-scouribility under hedgerows with tree, grass and shrub species increased by 121.2%,60.7% and 108.3% respectively, and soil anti-erodibility varied among hedgerow systems.(2)Comparing with soil in steep-land with no hedgerows, the soil porosity, moisture content, saturated conductivity and water stable aggregates content were increased by 9.3%,25.6%,68.4% and 11.5% respectively, while soil bulk density were decreased by 8.3%. Soil anti-scouribility and Anti-erodibility were increased 48.3% and 53.0%. The mean value of soil organic matter, total and exchangeable nitrogen, total and exchangeable potassium, total and exchangeable phosphorus of soil in hedgerows with different species were increased by 31.5%,40.3%,31.2%,7.6%,71.3%,76.4% and 57.3% respectively, cation exchangeable capacity by 23.1%. The hedgerow inter cropping ecological benefits including soil physical properties improvement, soil and water conservation, soil nutrients augment and non-point pollution controlling were performed by increasing organic matter, improvement of soil infiltration, interception of soil particles and soil fixation by hedgerow roots in hedgerow systems.(3) Soil volumetric fractal dimension was significantly correlated with various soil physical properties and soil nutrients concentration, therefore, Soil volumetric fractal dimension can be considered as a potential and accurate evaluating indicator for soil and nutrients loss and capacity of hedgerow intercropping on soil and nutrients conservation in steep land.(4)Soil anti-scouribility was correlated significantly with soil porosity, moisture content, saturated conductivity, water stable aggregates content, soil clay content, soil anti-erodibility, root mass density and soil organic matter. The equation between soil anti-scouribility and above mentioned parameters were established as: AS=-37.099-0.311SP+1.135SVW+0.568SC-0.300WSA-0.114AE+O.858SILT+2.866CLAY+30.004ROOT-0.129SOM(5)Applying analytic hierarchical process theory and combined integrating weight entropy method and expert grade to calculated synthesis weights, the ecological benefits of hedgerow intercropping were evaluated and the results indicated that the shrub hedgerows was performed the best ecological benefit, and the tree species was performed the modest ecological benefit and the grass hedgerows was the poorest one. With different species, hedgerows mixed with Vitex negundo and Ailanthus altissima had the highest value of comprehensive ecological benefits while hedgerows with tephrosia vestita Voge performed best on soil nutrients improvement and hedgerows mixed with gynura bicolo and herba rorippae performed best on non-point pollution controlling.