Study on the Suitability Assessment of Reverting Farmland to Forestry and Grassland in Inland River Basins in Arid land in Xinjiang

本文以塔里木河中下游地区的现有耕地为研究对象，对其退耕还林还草的适宜性进行评价。运用遥感手段布设样点，专家打分法与层次分析法筛选参评因子及确定权重，指数和法与最低限制因子评判法用来建立评价模型，累积频数法用来对退耕指数分级，利用地理信息系统软件编制塔里木河中下游适宜退耕区域图。结果表明：在13个影响塔里木河中下游退耕的参评因子中，灌溉水保证率、土壤总盐量对退耕的影响较大。而有机质含量、距离沙漠远近对退耕评价的影响较小；利用建立的评价模型计算出退耕指数，绘制累积频数图，根据图中曲线拐点的位置将退耕指数N划分为三级：适宜退耕N≥0.625，适宜中远期退耕0.475≤N＜0.625，保留耕地N≤0.475；依据退耕指数的分级结果，编制了1:10000。塔里木河中下游适宜退耕区域图，确定了该地区适宜退耕还林还草的面积和退耕地的空间分布，适宜退耕面积为7626．67 hm2，占耕地总面积的11.91％，适宜中远期退耕面积为6646.67hm2，占耕地总面积的10.38％，保留耕地49773.33hm2，占耕地总面积的77.71％。根据还林还草决定因素的综合判定，确定塔河中下游退耕地还林与还草的比例大致为3:2。最终退耕地形成林、草、农田，天然植被与人工植被相互协调的分布格局，即沙漠前沿、绿洲外缘形成天然林草植被与退耕还生态林形成带状绿色生态防护屏障，绿洲内部重盐碱化低产农田退耕还经济林还草与已有经济林共同构成斑块状的人工绿色植被。本论文有如下创新点：首次构建了荒漠平原区退耕评价体系；科学地对塔河中下游地区退耕适宜性进行了评价；将层次分析法（AHP）运用到退耕适宜性评价中，确定了退耕适宜性评价指标的权重；首次构建了退耕指数模型，为定量评价退耕奠定了基础；确定了还林与还草的面积与比例。本研究结果为该地区实施科学的退耕还林还草提供了重要的科学决策依据。This paper aims at the farmland in middle and lower reaches of Tarim River, carry through the suitability assessment of reverting farmland based assessment system. Use remote technical to dispose samples. Use method of scoring by specialist and the Analytic Hierarchy Process (AHP) to confirm indexes and ensure the weight of them. Use integrated evaluation and restricting factors evaluation on modeling. Use cumulating frequency to classes the reverting farmland index. Use Mapgis to draw the suitable reverting farmland sketch map in middle and lower reaches of Tarim River. The result shows: Among the 13 evaluating indexes of the suitability assessment, the guarantee of irrigation and salt content and the manner of irrigation have most importance influence. Organic matter content, distance of desert and days of gale and sand have less impact. Based model to account reverting farmland index and plot out the indexes three classes by the inflexion in the figure of cumulate frequency, over 0.625, from 0.475 to 0.625 and below 0.475. Though the map, ascertain the area and its space distributing of the suitable reverting farmland to forestry and grassland in this region. Suitable reverting farmland area is 7626.67 hm2 and it account of 11.91% of the total area; suitable medium long-dated reverting farmland area is 6646.67 hrn2 and it account of 10.38%; the reserved plough area is 49774. lhm2, and it account of 77.71 % of the total area. According to the synthetically decision, ascertain the proportion is 3:2 between the area of reverting farmland to forestry and grassland. Formed the pattern of forestry, grassland, natural forestry and artificial plant harmonize mutually. Namely in desert edge, outer oasis edge form natural forest and grass with the land of reverting farmland to forestry and grassland shaped strip green zoology shelterbelt barrier. Inner the oasis, after revering farmland, severity soil low yield farmland constitutes economical forest together with spot the artificial green plant. We can achieve these conclusions and innovating point: constitute the assessment system of suitability assessment of reverting farmland for the first time. Evaluate the farmland impersonally in middle and lower reaches of Tarim River by assessment system. Use AHP to ascertain the weight of indexes. Set up the model for evaluate the suitability of reverting. Ascertain the area and proportion of reverting farmland to forestry and grassland