Monitoring And Evaluation Of Ecological Rehabilitation Benefits Of The Sanyu Small Watershed

The Sanyu small watershed in the upper stream of Huangqian reservoir was the research site in the dissertation. The ecological benefits, such as changing of vegetation structure, soil improving, water conservation, microclimate were studied and analyzed, using monitoring at fixed sites and by changing vegetation condition, soil property, saving water, protecting soil, and weather as index. The ecological rehabilitation benefits of the saving water and protecting soil in this small watershed was further evaluated by using water balance method, shadow engineering method, and water storage cost method. The research results may provide scientific base and reference for implement of the ecological rehabilitation engineering in this area and the quantity evaluation of benefits. The results as follows:1. The Vegetation types increase in the ecological restoration area, and it tends to be rational in structure.Soil and water conservation forest and economic forest built the comprehensive protective system after implement of ecological rehabilitation in the area. Forest coverage increased significantly from20%to38.7%,.after the rehabilitation. The investigation results from2005to2010showed that the forest and grass coverage increased from47.7%to66.8%after implement of rehabilitation engineering in2010, improved by19.1%. It indicated that the environmental conditions were improved obviously by the implement of rehabilitation measures, such as sealing, breeding, and plating.The mean maximum canopy density of trees, brushes and grasses in broadleaf forest is0.88in closing type forest community after plantation rehabilitation. It’s significantly higher than other type plant community (0.81for coniferous forest). So, it indicated that the enhancing measures of closing and forbidden protection can efficiently increase the canopy density.The great variable of the root density happened among plant communities treated with different rehabilitations. The maximum root density of plant community in broadleaf forest of closing type plantation is8.7kg/m3,5.73kg/m3in replanting type of open forest, and5.6kg/m3in closing type plantation. It indicated that artificial forest method is the efficient measure for increasing biomass of the roots.For the water conserved forest, the growth increment of plant and biomass, which is62812.1kg/hm2,30871.2kg/hm2respectively in the mixed forest, is higher than that of pure stand, which is9286.7kg/hm~2. For the economic forest, the biomass of mixed forest, which is26415.2kg/hm~2, is higher than that of pure stand which is10231.2kg/hm. The results showed that both the water conserved forest and economic forest had higher biomass than that of pure stand. It indicated that the measures of increasing the amount of mixed forests should be taken to build comprehensive structure and biomass, to use efficiently the space of the forest and to increase the capacity of water storage and soil conservation.For the biodiversity index, species richness and biodiversity index of the trees, brushes and grasses in mixed forest of both of the water conserved forest and economic forest are higher than that of pure stand. It showed that the structure of communities was more rational and stable. The species richness, biodiversity, and evenness index of repaired waste slope plantation increased higher than that of the thinned young and supplement plantation.2. The soil structure was significantly improved on the ecological restoration area.All the index of soil physical properties in black locust forest were good, followed by that of walnut forest, the Chinese pine forest, hawthorn forest, Prunus armeniaca forest, and chestnut forest. Each index of soil physical properties in forest is better than that of wasteland.The content of soil colloids and crude fine gravel in forest is higher than that of wasteland24.62%and7.15%respectively. The silt and sand content in forest is lower than that of waste land by19.80%and5.48%respectively. In each vegetation types, the soil silt and colloid content in Chinese pine forest, hawthorn forest, chestnut forest is lower than that of hawthorn forest, Prunus armeniaca forest and walnut forest. Contrarily is the content of soil sand and crude fine gravel.The amount sequence of fractal dimension of soil particles in typical vegetations on research area is hawthorn forest>walnut forest> Prunus armeniaca forest> Chinese pine forest> chestnut forest> black locust>wasteland. The fractal dimension in forest is much more than that of wasteland.There is a linear positive correlation between the fractal dimension of soil particles and the content of soil sand colloids in typical vegetations. The smaller of the soil particles, the higher content of fine gravel, and the much more the fractal dimensions.There is a linear positive correlation between the fractal dimension of soil particles and the soil unevenness index. The fractal dimension of soil particles increased with the raising of the soil unevenness index. Except for waste grass lands, the soil in six types of vegetations is nice soil with unevenness index. The soil particles size distribution of plantation is better, and that of waste grasslands is the worst.3. The benefits of the microclimate on the ecological restoration area. The mean anion content in the air (FCI) in the closing type plantation was0.82. The biggest one is the Chinese arborvitae pure stand with FCI of1.1, and the smallest one is the mixed forest with FCI of0.49. It showed that the canopy density was larger in ecological forest, and the air flowed slower. So, the anion content in the air was lower. FCI in the Chinese arborvitae sparse wood before supplement was only0.26. However, FCI increased to0.84after supplement, improved by238%.In the waste slope plantation, the anion content in the air (FCI) before repair is0.48. After the planting, FCI in the red pine woods reach1.1, and improved by129%. FCI in chestnut forest reach1.96, and improved by308%. The results indicate that the anion content in the air in broadleaf forest increased easily, and increased the FCI concentration.4. The benefits and value of the water retention and storage by typical vegetation are significantly increasedOn the functions of water resources storage, preventing soil erosion and keeping fertility, it was calculated that total annual regulation water is10751085m, total purification water is10751085m3, total water conservation is21502170m3, and the per unit area water conservation is7579.2m~3/hm~2. On Sanyu small watershed, the annual total soil storage is9195.284t, and the keeping fertility amount is40861.476t.The value of annual regulation water by typical vegetation on Sanyu small watershed is6143.17million RMB Yuan. The value of purification water is2246.98million RMB Yuan. The value of total water conservation is8390.15million RMB Yuan. The value of soil storage by typical vegetation on small watershed is44196.97million RMB Yuan. The decreased fertilizer loss value is25832.72million RMB Yuan. Total value of soil protection is25837.13million RMB Yuan.