Grain for Green Project
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Abstract&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 土地是非常珍贵的自然资源，不同的土地利用政策对自然环境、生态系统服务甚至是社会经济发展产生深远影响。黄土高原地区属于典型的生态脆弱区，是国家重点扶贫县分布最集中的地区，是生态保护和经济发展的重点区域。1999年以来，中国政府在黄土高原地区实行了退耕还林工程，当地的土地利用/覆被发生了巨大变化。本文以陕北延长县为研究区域，基于1990-2000-2008三期遥感影像数据以及参与式农户调查数据，利用ArcGIS、SPSS等软件分析探讨了自然和人为干扰作用下延长县的土地利用变化；评估了退耕还林前后延长县土壤保持、粮食供给两种服务价值变化；分析了延长县产业结构变化，农民生活现状（包括收支结构、资源利用类型、生活满意度）；通过构建Logistic回归模型，探讨了影响农民生活满意程度的关键因素。主要研究结论如下： <br />1. 1990-2000年，延长县土地利用类型的面积和空间变化不明显。灌木林地分布在延河下游，草地主要位于河谷地带，耕地面积较大且分布分散，东部黄河沿岸地带分布相对集中。2000-2008年，受退耕还林工程的影响，草地空间分布发生明显改变，东部黄河沿岸的大片耕地都被草地所替代。1990-2008年，延长县草地、林地面积增加量分别为38868.5hm2和1664.9hm2；耕地面积则减少40484.6hm2，从占全县土地面积的37.29%降到20.65%。耕地减少的面积与草地和林地增加的面积基本持平。 <br />2. 1990-2008年，延长县土壤侵蚀量持续降低，从2979.53&times;104t/a降低到1812.88&times;104t/a。土壤保持量则经历了先降低后增加的过程，从1990年的4659.25&times;104t/a降低到2000年的3545.90&times;104t/a，至2008年增加为3987.08&times;104t/a，增幅达12.4%。1990-1998年，延长县粮食种植面积从260km2增加到290km2。延长县粮食总产量在3.9&times;104t/a到6.4&times;104t/a之间波动。1999年以后，粮食种植面积大幅度降低，从290 km2下降到约100km2，粮食总产量也迅速下降至3.0&times;104t/a并基本维持在此水平。 <br />3. 随着土地利用方式的变化，1990-2008年延长县经济产业结构发生明显变化，第一产业在全县GDP中所占比重持续降低，二、三产业所占比重迅速增加。47.51%被调查农户年收入在10,000-30,000元之间，75.57%的被调查农户年收入在10,000元以上。通过线性回归分析得到在所有收入类别中，按贡献度排序依次为果园收入＞打工收入＞养殖业收入＞其他收入＞耕地收入＞干部收入＞蔬菜收入＞个体经营收入＞退耕还林补贴。农民支出与收入水平相当，主要开销为生活支出、农业投资、教育和医疗支出。<br />4. 农户对当地环境质量（空气质量、水源质量、水土流失、垃圾处理）、交通状况、居住条件感到满意，而普遍认为耕地面积不足，医疗教育条件、物资丰富度方面亦不尽人意。另外，超过一半的受访者认为当地物价水平比较高，而自己生活水平偏向于贫困。通过构建Logistic回归模型，筛选出影响人们生活满意度的重要指标：居住条件、治安条件、物价和自身感知的贫困度，根据这四个指标构建了回归方程对农民生活满意度进行预测。
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Land resources are very precious all over the world. Land use policies would have profound impacts on the environment, ecosystem services and even the socio-economic development. Loess Plateau is a typical ecologically fragile area as well as the most concentrated place of national key poverty alleviation counties. So it faces the dual pressures of ecosystem conservation and economic development. Sinc<br />e 1999, the Chinese government launched the Grain for Green Project (GGP) in the Loess Plateau which triggered dramatic land use/cover changes. We selected Yanchang County of Shaanxi province as our study area. Based on remote sensing image of 1990, 2000 and 2008 and questionnaire data through Participatory Rural Appraisal, we discussed land use shifts under natural and anthropogenic disturbance and assessed the value of soil conservation and grain production by using ArcGIS. Then we investigated the changes of industrial structure of Yanchang County and explored the key factors which play pivotal role in people&rsquo;s satisfaction of their life. The main results are as follows: <br />1. From 1990 to 2000, the area and spatial variation of land use types of Yanchang County experienced unconspicuous change. Shrubs located along the downstream of Yanhe River and grassland spread in the river valley. The cultivated land appeared quite fragmented and covered vast area especially in the eastern bank area of the Yellow River. From 2000 to 2008, due to the GGP, an obvious change occurred to the distribution of grassland, for example, large tracts of cultivated land of the eastern bank along the Yellow River were replaced by grassland. During the 1990 to 2008 period, the area of grassland and forestland had a persistent increase with 38868.5hm2 and 1664.9hm2, respectively. However, the area of cultivated land decreased with 40484.6hm2, from 37.29% to 20.65% of the whole county area. The reduction area of cultivated land was approximately equal to the increase area of grassland and forestland.<br />2. From 1990 to 2008, the amount of soil erosion kept decline from 2979.53&times;104t/a to 1812.88&times;104t/a. The amount of soil conservation decreased first and then rose up, from 4659.2500&times;104t/a in 1990 to 3545.90&times;104t/a in 2000, and to 3987.08&times;104t/a in 2008 with an increase of 12.4%. From 1990 to 1998, the grain planting area of Yanchang expanded from 260 km2 to 290 km2. The total grainoutput fluctuated between 3.9 &times;104t/a and 6.4 &times;104t/a. Since 1999, the grain planting area has experienced a significant reduction from 290 km2 to approximately 100 km2. The grain production also dropped remarkably to 3&times;104t/a and remained at this level.<br />&nbsp;3. With the changing of land use, the industrial structure of Yanchang County changed observably from 1990 to 2008. The proportion of the primary industry in the county's GDP continued to drop and the proportion of secondary and tertiary industries increased rapidly. For 47.51% of the respondents, the annual incomes ranged from 10,000-30,000 yuan, and the annual incomes for 75.57% of the respondents was more than 10,000 yuan. By linear regression analysis, we sorted the income categories according to the contribution degree and the order should be: orchard income＞migrant work income＞livestock and poultry breeding income＞ other income＞grain cultivation income＞cadre income＞vegetable income self-employed income＞subsidy for GGP. The incomes generally balanced the expenditure and the major items in expenditure were living expenses, investment in agriculture, educational and medical expenses. <br />4. Local people felt satisfied about the environment (air quality, water quality, soil conservation, and refuse disposal), traffic conditions and housing conditions. But most respondents thought that the cultivated land was insufficient to support a whole family and the price was high. Meanwhile the education conditions needed to improve and local supplies were Inadequate. By constructing a Logistic regression model, we picked out the key indicators (housing conditions, security conditions, price and their own perception of the degree of poverty) that affected the degree of people&rsquo;s life satisfaction and based on the factors we constructed an equation to predict the satisfaction degree.