The Research On Ecological Benefit Evaluation Of Conversion From Cropland To Forest In Hongya County Sichuan Province

Conversion from Cropland into Forest Project is one of the six forestry projects and is also the biggest and the most influence and rigorous ecological engineering in china. This paper analyzed ecological benefit of the Conversion from Cropland into Forest Project in Hongya county from the two aspects of macroscopic and microscopic. Macroscopic parts contained the changes of the land use/vegetation dynamic, the changes of vegetation coverage and the changes of soil erosion intensity. Microscopic aspects contained the soil physical and chemical properties, the vegetation community characteristic and the woodland hydrological effects.Then we choosed some indexs that were compliance with local characteristics and typical and worked out a reasonable ecological benefit evaluation system.Finally we calculated and evaluated the ecological value of the Conversion from Cropland into Forest Project in Hongya county.During the period of Conversion from Cropland into Forest from1999-2009in Hongya county, the annual gradient of the Land Use is5.63%and the farmland and forest land had maximum change range.According to the forecast of Markov Model, there was estimated that cultivated land will continue to redvice and forest land will continue to increase by2019.Analysis showed that in these two periods of land use/cover transition process the cultivated land and forest land were always the major transformation types in Hongya county.In the area of Hongya county the vegetation coverage that transfered into dynamic equilibrium state when the vegetation coverage getted up to a relatively stable of50-70%emerged from low to high transfer trend.The largest amount of soil erosion intensity changed were micro-degree erosion and no significant erosion and the soil erosion intensity distribution position had small fluctuation.With the growth of the seven forest species, there were caused a great change of environment in underlying surface of the abandoned lands,which was reducing the soil bulk density,increasing the soil porosity and soil water content, making the clay content of soil mechanical composition higher and higher,making soil structure more and more reasonable and improving the content of soil organic matter and NPK in Hongya county. The undergrowth herb was basic stable.The vegetation types were further positive succession and basicly formed combination with trees and herbs stable community system in Hongya county. The leaves, trunk,herbs and litter of the seven forest species had strong interception effect and also improved soil infiltration very well in hydrological effect.The analysis showed that the better forest species which improved ecological benefit best were Bitter Bamboo and Moso Bamboo.Until2009, the ecological benefit of Conversion from Cropland into Forest project in Hongya county fixed total value of1.748billion yuan for10years. The value of the water resources protection was the largest.Fixing carbon and producing oxygen value was the second smallest and environment purification value was minimum, which were respectively for944million yuan,503million yuan and7.65million yuan and the proportion of the total value respectively accounted for54.02%,25.36%and0.44%.