【作者】 郭建英；

【导师】 孙保平；

【作者基本信息】 北京林业大学 ， 水土保持与荒漠化防治， 2010， 博士

【摘要】 本文在全面分析总结国内外现有退耕还林工程监测与评价研究成果的基础上,以黄土丘陵区的吴起县为研究地点,通过对当地不同类型退耕还林（草）地的植物多样性、群落生产力、土壤理化性状、林地水文效应及退耕还林前后土地利用/覆被变化等进行了系统的研究,揭示了退耕还林后当地生境的演变过程及其特征,并在实地调研与监测的基础上采取层次分析、理论分析、问卷调查、定量与定性分析等相结合的方法,对当地退耕还林工程的生态、经济和社会效益进行了相对客观、全面、科学、准确、系统的分析与评价,确立了符合当地退耕还林（草）工程综合效益评价指标体系,得出退耕还林工程对促进当地生态效益、社会效益、经济效益的贡献率。研究工作所取得的主要认识与结果如下:（1）退耕还林工程改变了土地利用结构。退耕还林10年来,各种土地利用类型之间发生了较为复杂的转化。耕地面积比退耕前减少66.51%,减少的旱地主要转化为灌木林地;林地面积比退耕前增加了212.61%,主要由退耕地和草地造林转化而来;草地总面积变化不大,主要是荒草地、中覆盖度草地转向高覆盖度草地和灌木林地;居民建设地面积比退耕前增加了105.03%,水域用地面积比退耕前减少26.1%,主要是线状水系减少,水库、湖泊面积有所增加。（2）退耕还林工程优化了植物群落结构。退耕还林工程的实施,加速了对当地脆弱环境的修复,造林10年后,地带性植被长芒草、糙隐子草在不同的林地类型中均有分布,且与天然草地的重要值相近,林草群落结构已趋于稳定;从促进林下植被的多样性方面来看,沙棘×山杏混交林是吴起县相对最适合的混交林,对促进植被的恢复效果较佳;不同退耕还林地群落的生物量具有明显的差异,除了油松和山杏纯林的枯落物生物量较小外,其他林地的枯落物生物量均大于天然草地;封育对草地环境的改善较为明显,由以一年生旱生植物为主的草本群落演替为由地带性植被长芒草、达乌里胡枝子为建群种的多年生草本群落,植被覆盖度由20%增加到75%,封育7年后的生物量比未封育草地提高317.89%。（3）退耕还林工程改善了退化的土壤环境。①实施退耕还林后,退耕地土层之间的孔隙度变幅很小,而农耕地和天然草地的非毛管孔隙度锐减很大,不利于下渗过程的持续进行;除了沙棘林地外,其他林地表层土壤容重明显低于下层,在各类型地中农田的上下层差异最大;退耕还林地的土壤主要以粗粉粒为主,退耕地的粘粒总体含量均高于农田;土壤有机质增加明显,不同退耕还林地土壤有机质含量均随土层深度的增加而递减,表现出明显的表聚性;退耕还林地的土壤全量氮、磷、钾在不同林种、林带间、土层的差异均不显著,不同林地间的土壤有效氮、速效磷、速效钾之间的差异不显著,但不同土层间的差异极显著;封育7年后,随封育时间的增加,封育草地的土壤含水量提高、容重不断减小、孔隙度不断增大;土壤养分除全磷、速效磷外,其他养分含量均有不同幅度的增加,且土壤养分表聚性明显。（4）退耕还林工程初步形成了森林水文效应。不同退耕还林地人工林的林冠截留量都较高,变幅在0.07～0.52mm之间,截留量最大的的是柠条林（0.52mm）,截留量最小的是山杏林（0.07mm）;沙棘×山杏混交林的渗透速率最大,为1.72 mm/min,山杏林地的稳渗速率最低,仅0.36mm/min。（5）退耕还林工程产生了显著的生态效应。退耕还林工程实施10年来,林地覆盖率由退耕前的12.3%提高到38.4%;累计涵养水源35405.03万m³、减少土壤侵蚀物质6032.24万t、固定CO₂总量821.88万t、制氧总量276.95万t、吸收SO₂总量5.41万t、滞尘总量0.62万t;退耕还林工程发挥的生态效益经相对支付意愿系数调整后的总价值为58.61亿元,水土保持效益价值所占比例最大,共为52.7%,其中保育土壤价值占生态效益总价值30.4%,保护水资源价值占22.3%、固碳制氧价值占25.3%、保护生物多样性价值占19.1%、净化环境价值占0.3%、改善小气候价值占2.6%。（6）退耕还林工程推动了当地社会经济的发展。退耕还林工程实施10年来,当地取得了较大的直接经济效益,总计9.75亿元,其中林木价值1.79亿元、牧草价值6.41亿元、林果产品价值1.55亿元;退耕还林后有38.2%的劳动力转移到种植业以外的其他行业,2008年农林牧总产值比退耕前1998年增加了97.8%,退耕还林后粮食产量并没有与退耕地面积成同比减少,退耕后人均粮食379 kg,高于我国现在的人均年消费口粮的206 kg,高45.6%,农民人均纯收入平均每年以36.9%速率递增,收入结构多样化,打工经商的收入所占比例较大,占人均收入32.7%。总体来看退耕还林工程不仅具有维护生态安全、促进人与自然和谐的生态功能,而且具有增加农民收入、促进经济发展、社会和谐、推动文明进步等功能。其符合科学发展观的要求,发挥的效益比例得当。所取得的综合效益中,生态效益所占的比例最大,为63.08%,其次为经济效益,其所占比例为21.35%,社会效益的比例最小,为15.57%,与当地的实际情况基本一致。同时说明文章中构建的评价体系是正确的、科学的、可行的、具有可操作性。更多还原

【Abstract】 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.更多还原