Research On Monitoring And Benefit Evaluation Of Project For Conversion Of Cropland To Forestry In WuQi County

Based on comprehensive analysis and summarizes the research findings of existing reforestation monitoring and evaluation, taken the WuQi county in loess hilly region as the study site, a systematic studied was made in different types of land with conversion of cropland to forestry from biodiversity, community productivity, soil physical-chemical properties and soil hydrological effect. To reveal the evolution process of habitat and its characteristics after converting cropland to forest, and on the basis of monitoring, by the combining method of theoretical analysis, the questionnaire survey, quantitative and qualitative analysis, a comprehensive, systematic, scientific and accurate analysis and evaluation was made to local forestry project from ecological, economic and social comprehensive benefit. The main research results are as follows:(1) Conversion of cropland to forestry changed area of land use structure. After 10 years reforestation, complex transformation was taking between various types of land use. Compared to the past, cultivated land area reduced by 66.51%, which is transformed into shrub land. Forest area increased by 212.61%, which is transformed by cropland and grassland. The total area of grassland was basically no changes, which is mainly transformed from badlands, moderate coverage grassland to high coverage grassland and shrub land. Residents in construction area increased by 105.03%. The land area of waters decreased by 26.1%, In which the area of linear water system mainly reduced, the water area of reservoir and lake increased.(2) Conversion of cropland to forestry region optimized community strucTure. Viewed from important value change of herbaceous plants in the forests, Stipa bungeana,Cleistogenes squarrosa are distributed in different types of forest , which have similar important value with natural grassland, community structure tend to remained stable. Viewed from promoting the diversity of the undergrowth, Seabuckthorn×ansu apricot mixed forests is relatively suitable forests in WuQi county , which is better to promote the vegetation restoration .Community biomass of different restoring forest has significant difference, but Chinese pine and the ansu apricot pinus pure forest have smaller litter biomass , litter biomass of other woodland is greater than that in the natural grassland Enclosure of the environmental improvements are relatively obvious, Succession from Grass communities with annual xerophytic plants to a community of the perennial herbs with the zonal vegetation of Stipa bungeana,Lespedeza potaninii as build constructive species. Vegetation coverage increased from 20% to 75%. After 7 years, the biomass of enclosure increased by 317.89% compared to biomass of open system.(3) Conversion of cropland to forestry improved regional soil environment. Non-capillary porosity of different forest canopy, porosity and capillary porosity between the channels of reforestation land are significantly different. The non-capillary porosity in the upper layer are greater than that in the down layer in different types of land . The non-capillary porosity of agricultural land and natural grassland declined greatly, which react against the ongoing process of infiltration. Besides seabuckthorn, bulk density in the upper layer was significantly lower than that in the down layer in other woodland forest soil, farmland take the biggest difference among all the land; forest soils in WuQi county are mainly thick powder, the viscous grain content in reforestation land were higher than that in general farmland, Soil organic matter content increased significantly ,with soil depth increased soil organic matter content decreased, it showed significantly top enrichment. Total amount of nitrogen, phosphorus and potassium in different forest type, belts and soil layer have no significantly difference .And the rapidly-available phosphorus and rapidly-available nitrogen, rapidly-available potassium had no significant difference between different forest belts , but that in soil layer had significantly difference, after 7 years enclosure, soil moisture content and porosity in the cultivating grassland improved, volume weight decreased. Except total phosphorus, rapidly-available phosphorus, the contents of soil nutrient are increase to some extent, and the soil nutrient show significantly top enrichment.(4) Conversion of cropland to forestry has promoted the formation of regional forest hydrological benefits. Conversion of cropland to forest plantations in different places had a high canopy interception, whose amplitude was in between 0.07～0.52mm. Interception is the largest in Caragana Lam (0.52mm), interception is the smallest in Siberian Apricot (0.07mm). Infiltration rate of the mixed Seabuckthorn and Apricot is the largest and the value was 1.72 mm / min. A infiltration rate of pricot woodland steady is the lowest, the value was only 0.36mm/min.(5) Conversion of cropland to forestry created significant ecological benefits, implementing the project 10 years later, forest coverage rate increased from 12.3% prior to reforestation to 38.4% after reforestation, the project had accumulated water resource for 354.0503 million cubic meters, reduced soil erosion material for 60.3224 million tons, fixed the total CO₂ for 8.2188 million tons , produced the total oxygen for 276.95tons, absorbed the total SO₂ and the total dust for 54100 tons and 6.2 thousand tons respect. Adjusted by Relative to pay willing index, the total value of eco-efficiency project for returning farmland to forest is 5.861 billion yuan, the largest proportion of the value was of soil and water conservation benefits , totally 52.7%, of which the value of conservation of soil accounted for 30.4%,the value of the conservation of water accounted for 22.3% ,the value of carbon sequestration and oxygen accounted for 25.3% the value of biological diversity accounted for 19.1%, the value of cleaning up the environment accounting for 0.3% and the value of improving the micro-climat accounted for 2.6%.(6) Conversion of cropland to forestry promoted the development of local social and economic benefits. Implemented project for 10 years, the local had get large direct economic benefits, a total of 975 million yuan, of which the value of trees generated by 179 million yuan, the value of pasture generated by 641 million yuan, the value of fruit products generated by 155 million yuan. After returning farmland to forest, there is 38.2% of the workforce transferred from farming to other industries. In 2008, total output value of agriculture-forestry-animal husbandry increased by 97.8% compared to that in 1998. After returning farmland to forests, farmland and food production were not reduced compared to that year on year (about 379 kg of grain per capita) , which is higher than China's current annual per capita grain consumption of 206 kg, with an increase of 45.6%. Rural per capita net income increasing to an average annual rate of 36.9%, revenue structure is diversity, working in business has a larger proportion of income, accounting for 32.7% of per capita income.Overall land conversion projects can mainten ecological safety, promote the harmony between man and the nature, but also increase farmers' income, and promote economic development and social harmony and advance civilized progress etc. At the same time, they meet with the requirement of the scientific development concept, get proper proportion of benefit. Among the comprehensive benefit, ecological benefit is the maximum proportion of 63.08%, followed economic benefits by the proportion of 21.35%, social benefits is the smallest percentage of 15.57%, this accord with local actual condition.Meanwhile,it basically illustrates that evaluation system constructed in this article is correct and scientific and feasible and practical.