基于GIS的关中地区土地利用变化及土地生态安全动态研究

【作者】 莫宏伟；

【导师】 任志远；

【作者基本信息】 陕西师范大学 ， 地图学与地理信息系统， 2010， 博士

【摘要】 土地是人类生存和发展的基础,随着人口增长以及工业化、城市化推进,土地生态问题日趋严重地影响着人类的安全、制约着社会经济的发展；因此,土地生态安全成为当前的研究前沿和热点问题之一。然而,目前土地生态安全研究的理论和方法都还处在探索阶段,有诸多问题亟待解决。关中地区是西部地区的经济文化中心,涵盖高原、盆地、山地等多个地形区,退耕还林、城市化等全局性的土地利用变化在本区均有典型体现。随着西部开发进程提速,该区的环境、经济、人口压力加大,区域土地生态系统的结构和功能变化加剧。研究这些变化对区域土地生态安全的影响过程和机理,对本区土地资源持续利用及深化土地生态安全研究的理论与方法具有重要意义和作用。本文依托国家自然科学基金项目(编号：40771019),以遥感影像、野外考察数据、气象数据、土壤数据、土地利用数据及各种环境经济统计数据为依据,选择土地生产潜力总量、植被覆盖指数、土地生态系统服务价值、土地生态风险强度指数作为土地生态安全程度的评价指标；以RS和GIS为技术支撑,从栅格、地貌单元、坡度带及行政单元等多个尺度上分析各单项评价指标的时空变化特点；然后运用熵权法、主成分分析法对各单项指标进行加权和去相关处理,再按欧氏距离法合成土地生态安全综合评价指数分布图；最终从多个时空尺度揭示了关中地区的土地生态安全动态特征和趋势。通过研究,本文得到了以下主要结论：1)1986-2007年,关中地区耕地、草地、水域、未利用地减少,林地、建设用地增加,土地利用变化面积占全区总面积的5.70%；耕地转化为林地、草地流转为林地、耕地转变为建设用地等三种变动类型占全区总变动量的81.52%；平原区、黄土台塬区最大的变动是耕地流转为建设用地,而黄土梁峁区、黄土塬区、山地区最大的变动则为耕地向林地转化。研究区景观离散程度增加、破碎化加剧、景观多样性加大。土地利用程度在1986-2000年处于发展时期,在2000-2007年为土地利用程度的调整期。2)1986-2007年,关中地区农用地生产潜力总量减少,土壤潜力总量减幅为1.06%；其中耕地、草地土壤总潜力减少了6.64%、5.20%,林地土壤总潜力增加了12.55%°各地貌单元的农用地生产总潜力减少,平原区减速最快、山地区最慢。0-20°坡度带的各类农用地生产总潜力减少,减量随坡度增加而减少。各地市的农用地各级总潜力都减少,减速排序为：西安市>咸阳市>渭南市>铜川市>宝鸡市。45个区县评价单元中,有5个区县的农用地总潜力略有上升。3)1986-2007年,关中地区林草覆盖率增加了15.25%,2000-2007年段增速约为1986-2000年段的2.60倍；各地貌单元林草覆盖率增幅表现为：山地>黄土梁峁>黄土塬>黄土台塬>平原；各坡度段的林草覆盖率增加,增速随坡度增大而加大。各地市林草覆盖率增速为：西安市>渭南市>咸阳市>铜川市>宝鸡市；所有区县的林草覆盖率均增加。4)1986-2007年,关中地区的土地生态服务价值总量增加了10.09%；2000-2007年段增速约为1986-2000年段的33.65倍。平原区的土地生态系统服务价值量减少,其余四类地貌单元的土地生态系统服务价值量均增加,增速最快的是山地区。0-3°坡度段的土地生态系统服务价值量持续下降,>30段的增加,且增速随坡度的增加而增加。各地市的土地生态系统服务价值量均增加,增速最快的是宝鸡市。有11个区县的土地生态系统服务价值量减少,其它区县均增加。5)1986-2007年,关中地区土地生态风险强度先增后减,总体减少。各地貌单元中,平原区土地生态风险强度持续增加；黄土台塬区土地生态风险强度是先增后减,总体加大；其余三类地貌的土地生态风险强度是先增后减,总体变小。各坡度带中,>30段的土地生态风险强度是先增后减,总体降低；0-3°段则连续增加。各地市土地生态风险强度最大的是渭南市,最小的是宝鸡市；渭南、西安两市的土地生态风险强度是先增后减、总体加大,宝鸡、铜川、咸阳三市则是先增后减、总体变小。所有区县中,有17个区县土地生态风险强度加大。6)1986-2007年,关中地区土地生态安全情况总体改善,且2000-2007年段改善程度比1986-2000年段明显。整个研究期内,各地貌单元、各坡度带、各地市及各区县(西安市区除外)的土地生态安全态势总体上都在向好的方向转化；1986-2000年段,平原区、黄土塬区、0-3°段、咸阳市、渭南市以及22个区县评价单元的土地生态安全情况恶化。研究区的土地生态安全程度的时空变化特点是土地利用／覆被变化的结果,“退耕还林”政策的实施促使了该区土地生态安全态势的总体好转。本文在以下几方面有所创新：1)利用土地利用图和生态服务价值当量因子表获取单位生产力价值当量分布图,然后与植被和坡度修正后的土壤生产潜力分布图进行地图运算,最终比较好地在栅格尺度上解决了土地生态系统服务价值评价的空间异质性问题,弥补了利用生态价值当量因子表评价生态系统服务价值的一个主要缺陷。2)利用土地利用变化图叠加土地生产潜力分布图,得到各类土地的各级潜力的转移图谱,其结果不仅包含了土地利用的数量变化信息而且也包含了质量变化信息,从而解决了土地类型数量变化不能反映优质土地流失的缺陷,为国家耕地占补平衡政策的进一步完善提供了可操作性的方法。3)运用GIS手段,实现了从栅格单元到地貌单元、坡度带以及行政单元等多尺度的时空动态研究,从而对土地生态安全状况在各种尺度上的转换情况有了更深入的了解。4)构建了新的土地生态安全评判指标体系,该指标体系具有简明普适的特点,各项指标意义明确、综合性和代表性强,指标计算方法科学。更多还原

【Abstract】 Land resources are the bases of human survival and development. With the rapid growth of population and the rapid development of industrialization and urbanization, land ecological degradation affects human health and restricts the socio-economic development seriously. Therefore, land ecological security has become one of the research frontiers and hot research topics now. However, at present, the theory and method of land ecological security research are still in the exploratory stage, and many problems need to be resolved. GuanZhong area which including different geomorphologic patterns is the economic and cultural center of western China. Land use changes such as urbanization and replacing farmland with forest are typical in GuanZhong area. With the accelerating of Western development, the pressures loading on the land here increase, and the structure and function of its land ecosystem have been changed violently. Studying the process and mechanism which these changes affect land ecological security here has important significance for keeping land resources of GuanZhong area sustainable and deepening the theory and method of land ecological security.Relying on the National Natural Science Foundation of China(No.40771019), Based on remote sensing images, fieldwork data, climate data, soil data, LUCC data, environmental and economic data, using the theory of geographic information images and supported by RS and GIS, choosing total soil production potential, vegetation cover index, ecosystem services value, and ecological risk intensity index as the evaluation index of land ecological security, the author has analyzed their temporal-spatial changes in different scales such as grid units, terrain units, slope units, and administrative units of GuanZhong area from1986 to 2007. Then assigning the weight for each evaluation index by entropy method and using principal component analysis to remove relevance of the weighted evaluation index, the author synthesized a comprehensive evaluation index of land ecological security by euclidean distance and revealed temporal-spatial changes of land ecological security of GuanZhong area in different scales betweenl986 and 2007. The results show that:1) From 1986 to 2007, the area of cultivated land, grassland, waters and unused land decreased, while the area of construction and forest land increased in GuanZhong area and the change accounts was about 5.70% of the total area. There are 29 categories of changes; and the 3 main kinds of changes whose area was 81.52% of the total changes were the transformation from cultivated land to forest land, from grassland to forest land and from cultivated land to construction. The largest change in plain and loess plateau was cultivated land converted into construction, while largest change in mountains, loess mountain ridge and loess tableland, was cultivated land converted into woodland. Fragmentation, diversity and dispersion degree of the landscape increased. Land use degree belonged to the period of development from1986 to 2000, and the period of adjustment between 2000 and 2007.2) Between 1986 and 2007, it decreased for the total productive potential of agricultural land in GuanZhong area, in which the total soil potential of the cultivated land and grassland decreased by about 6.64% and 5.20% while that of forest land increased by about 12.55%. It declined in general in all geomorphologic patterns for the total productive potential of agricultural land, which shrank the fastest in plain and the slowest in mountains. It decreased in slope zones from 0 to 20 degree for the total productive potential of agricultural land, which reduced with the slope increasing. It declined in all cities of GuanZhong area for the total productive potential of agricultural land, whose deceleration order as follows:Xi’an city>Xianyang city> Weinan city>Tongchuan city> Baoji city. There are five counties whose total potential of the agricultural land increased slightly while the others reduced.3) In 1986-2007, the vegetation coverage of forest and grass in GuanZhong area increased by 15.25%, and the growth rate of the vegetation coverage in 2000-2007 was as about 2.60 times fast as that in 1986-2000. The vegetation coverage in all geomorphologic patterns increased, and the order of the growth rate as follows:mountains> loess mountain ridge> loess tableland> loess plateau >plain. The vegetation coverage in all slope zones increased, whose growth rate expanded with the slope increasing. The vegetation coverage in all cities raised, and the order of the growth rate as follows:Xi’an city>Weinan city>Xianyang city>Tongchuan city> Baoji city. The vegetation coverage in all counties grew.4) From 1986 to 2007, the total ecosystem service value (ESV) of GuanZhong area increase by 10.09%; and the growth rate of the total ESV in 2000-2007 was as approximately 33.65 times fast as that in 1986-2000. Among five geomorphologic units of GuanZhong, the total ESV of plain reduced and the total ESV of the other four geomorphologic units increased, in which both the largest increment and the fastest growing took place in mountains. The total ESV of the slope zones between 0 and 3 degree declined, but the total ESV of the slope zones whose slope was more than 3 degree expanded, and both increment and growth rate increased with the slope raising. The total ESV of all cities of GuanZhong area expanded, and both the largest increment and the fastest growing took place in Baoji city. There are 11 counties whose total ESV increased in GuanZhong area in the research period.5) During 1986-2007, the land ecological risk index (ERI) reduced generally in GuanZhong area. Among five geomorphologic patterns, the land ERI of plain and loess plateau raised; but that of mountains, loess mountain ridge and loess tableland decreased. Among all slope zones, the land ERI of the slope zones between 0 and 3 degree increased, but the land ERI of the slope zones whose slope was more than 3 degree reduced generally. Among all cities, there was biggest land ERI in Weinan city and the smallest in Baoji city, while the land ERI rose generally in Weinan city and Xi’an city, but the land ERI reduced generally in Baoji city, Tongchuan city and Xianyang city. Among all counties, there were 17 counties whose land ERI rose.6) Between 1986 and 2007, the land ecological security situation improved generally in GuanZhong area, and there were more improvement in 2000-2007 than in 1986-2000. The land ecological security situation improved generally in all geomorphologic patterns, slope zones, cities and counties (except Urban area of Xi’an city) of GuanZhong area during 1986-2007,but during 1986-2000, the land ecological security situation deteriorated in plain and loess plateau, slope zones between 0 and 3 degree, Xianyang city and Weinan city, as well as 22 counties. Land use/cover change resulted in the temporal-spatial changes of land ecological security of GuanZhong area, and replacing farmland with forest helped the land ecological security situation here better.There may be following innovative in this research:1) Using land-use map and equivalent value per unit area of ecosystem services in China to obtain distribution map of equivalent value per unit productivity of ecosystem services, and then multiplying it with the distribution map of soil production potential which was revised with slope and vegetation index, by which the spatial heterogeneity issue of land ESV assessment was solved at the grid scale. This method made up a major flaw of land ESV assessment relying on equivalent factor.2) Overlaying the distribution map of land-use changes and the distribution map of land production potential, we can obtain the distribution map of land production potential transfer which includes information about the changes of land quality. This method made up the deficiency that land-use change can not reflect land quality erosion, and offer a workable approach for further improving the dynamic balance policy of arable land quantity.3) Supported by RS and GIS, multi-scale dynamic analysis was done in the research from grid cell to terrain patters, slope zones and administrative units. This method can help us get a deeper understanding on land ecological security situation and its conversion in different scales.4) Established a new evaluation index system of land ecological security. The indicator system is simple and universal. Each indicator means clear and has good comprehensive and representation.更多还原