【作者】 彭丽；

【导师】 周志翔；

【作者基本信息】 华中农业大学 ， 生态学， 2013， 博士

【摘要】 三峡库区是中国生态环境脆弱区之一,库区土层贫瘠,保土保水能力差,随着三峡库区人口的急速增长,库区资源相对不足,环境承载能力逐渐减弱,人地之间的矛盾日益突出,特别是三峡工程建设过程中,大规模的移民和城镇整体搬迁引起三峡库区土地利用利用／覆被发生重大改变。土地利用／覆被变化会引起一系列的生态环境问题,土壤侵蚀、生态系统服务功能的改变等均受到热切关注。本研究在土地利用／覆被变化理论、景观生态学理论、空间分析理论、土地利用优化配置理论及RS、GIS技术的支持下,通过三峡库区TM影像解译及MODIS数据、地形数据、土壤数据、气象数据、森林资源二类清查数据与社会经济数据的数学模拟和地统计分析,研究了三峡库区土地利用／覆被变化特征、景观格局动态与影响因素、生态系统服务功能及土壤侵蚀的土地利用结构控制。主要研究结论如下：(1)基于1988年、2000年、2007年3个时期遥感影像,运用动态度模型、信息熵模型、土地利用综合程度模型和土地利用转移矩阵等研究方法,分析了三峡库区土地利用／覆被动态变化与空间分异特征。结果表明：三峡库区的土地利用特点以林地和耕地为主导类型,两者占库区总面积的85%左右；三峡库区幅员辽阔,区域分异明显,林地空间分布呈现出东部多西南部少的特点,而耕地空间分布与林地相反,呈现出西南部多东部少的特点；19年间,三峡库区土地利用类型发生了较大的变化,林地面积和城镇面积大幅增加,耕地面积明显下降；三峡库区土地利用变化的区域分异明显,西南部地区土地利用类型变化幅度低于东部地区变化幅度。研究期间三峡库区土地利用类型之间的转化模式主要表现为：林地与耕地之间的相互转化；林地和草地之间的相互转化；耕地和草地之间的相互转化。三峡库区土地利用变化过程中,耕地的面积持续减少,而库区人口激增,人均耕地面积迅速减少,随着城镇面积急速扩张,逐渐加大了人-地之间的矛盾；19年间库区土地利用程度逐渐下降,在一定程度上缓解了土地压力；随着林地、水域面积等生态用地面积的持续增加,三峡库区生态环境得到改善。(2)从研究区总体尺度和区域尺度考虑,采用景观指数的研究方法,分析了1988-2007年三峡库区景观格局的变化情况。结果表明：研究期间三峡库区景观格局发生较大变化。在库区整体尺度上,林地平均斑块面积增加,斑块数减少,斑块密度减小,斑块形状逐渐简单。研究期间林地破碎化程度有减缓趋势,林地面积逐步扩张。林地景观在各区域分布不均,库区东部和中南部各指数变化幅度大于西南部地区；耕地斑块数下降,斑块密度增加,平均斑块面积呈明显减小,耕地的破碎化程度呈增加的趋势,耕地景观在各区域分布主要表现为西南部和中北部各指数变化幅度较大。草地景观的斑块数和斑块密度下降明显,平均斑块面积明显增加,可见草地斑块破碎化程度下降,在空间分布上不均衡。城镇景观斑块数明显增加,平均斑块面积和斑块密度显著增大,表明城镇景观的扩张趋势。未利用地和水域斑块数和斑块密度减少,平均斑块面积持续增加,未利用地和水域破碎化程度下降。从三峡库区景观格局整体变化趋势来看,1988-2007年三峡库区景观多样性指数和均匀度指数分别由0.92和0.52增加至1.09和0.61,散布与并列指数由37.01%增加到47.23%,表明三峡库区总体景观结构组成成分的复杂性增加,景观类型向多元化方向发展,各景观类型之间变得彼此邻近,呈镶嵌分布,呈现出多种景观要素密集分布的格局。(3)采用逐步回归模型,通过空间分析,定量分析了土地利用景观格局与影响因子的关系和影响大小。结果表明不同土地景观类型的影响因素互不相同,自然因素是制约林地、草地和未利用地分布的关键因子,城镇的分布主要受到人文因素的影响,而耕地和水域受到自然和人文因素的共同作用,总体上来说,气候(年均气温、年降水量)和地形(坡度、海拔)对三峡库区土地利用类型分布的作用比较明显,是形成三峡库区土地利用景观分布格局的主要因素。(4)基于三峡库区土地利用／覆被变化数据,采用生态系统服务功能评估模型,定量评估了三峡库区生态系统服务功能。结果表明：1988-2007年三峡库区生态系统服务功能价值总量增加了144.04亿元,生态环境质量明显提高,土地利用类型得到改善。从土地利用类型生态系统服务价值来看,林地和耕地类型的经济价值总量占三峡库区生态系统经济价值总量的90%左右,耕地的变化对三峡库区的生态环境质量有负面效应,而林地、草地和水域对生态环境质量起到正面效应。生态系统服务功能价值从区域分布情况来看,地形复杂的东部地区林地面积大,生态系统服务价值较大,以低山丘陵为主的西南部,生态系统服务功能较小。(5)基于降低土壤侵蚀风险评估,对三峡库区土地利用结构进行优化。优化后,三峡库区森林面积增加约5900km2,森林覆盖率提高约10.3%,达到59.13%,耕地和灌草地面积分别下降至33.84%和3.78%。增加的林地主要来源于坡度较大的耕地、坡度较小且海拔较低的灌草丛以及未利用土地。土地利用结构优化后,三峡库区土壤侵蚀模数、土壤侵蚀量平均为2514.741t km-2a-1、145.02×106t,分别减少446.731km-2a-1、25.71×106t,降幅为17.76%。表明优化土地利用结构可使三峡库区土壤侵蚀得到有效控制,库区生态环境明显改善,有利于三峡库区可持续发展。更多还原

【Abstract】 The Three Gorges Reservoir Area (TGRA) lies in the upper reach of Yangtze River Basin in central China. It has attracted worldwide attention because of the largest water conservation project in the world. This attention has not been only for its comprehensive social and economic benefits, but also for the potential security impacts on the natural environment and the potential geological disasters, as well as on the biological diversity imposed on the surrounding reservoir area. With population growth and human activities in the region since1980s, the land use/cover has changes rapidly because of excessive cultivation and over-felling. For example, the woodland area and the diversity of vegetation reduced quickly, which has resulted in forest fragmentation. Such changes have huge impacts on the eco-environment and biodiversity across the region. The objective of this study was to analyze the spatiotemporal pattern of land use and land cover (LUCC) in TGRA during1988-2007a, and therefore provide essential information for decision makers and planners to develop and implement land resources management and ecological environment protection in TGRA.Based on remote sensing, such as GPS and GIS technology;, combining mathematics model and space statisical analysis methods, the land use/land cover change, and land use structure optimization, landscape patern and its influencing factors, and ecosystem services were studied. The main results were listed as following:(1) The digitized stand maps from1988to2007were used to analyze change land use and land cover. The results showed that forest and farmland were the dominant land use and land cover types, which accounted for approximately90%of the study area. Significant increase in woodland and rapid decrease in farmland was observed in the study period. The farmland decreased by30.58%from31950.75km2in1988to22180.05km2in2007, while forest increased by26.91%from22312.08km2in1988to28317.02km2in2007. In the study period, there is a significant regional difference in LUCC and the change in the east was greater than in the southwest. The major patterns of land use change were the conversions of woodland to farmland and grassland, farmland to woodland and grassland, and grassland to woodland. The "’woodland to farmland" and the "woodland to grassland" changes indicated a high rate of deforestation. On the other hand, the "farmland to woodland" and "farmland to grassland" change indicated the land abandonment as well as the regeneration of woodland and grassland in this area. The conversion among farmland, woodland and grassland in this19a period was mainly due to the population expansion and the policy of conversion of farmland to woodland and grassland.(2) The multi-scale evolution of landscape pattern was analyzed. The results showed that in the study period, the spatial pattern of forest varied obviously. The increase in MPS was associated with a decrease in PD and a substantial increase in LPI, showing that the woodland became more clumped and gained land area from other classes of land. In the whole study period, there is a significant regional difference in landscape indices of forest and the changes in the east and middle was greater than in the southwest. Farmland area in the TGRA decreased rapidly. The NP increased from30223to31512between1988and2007. The PD increased from0.149per100ha to0.155per100ha, while the MPS decreased obviously from105.73to70.40ha. These results showed that the farmland became more fragmentation. The patch shapes grew simple and patches distribution concentrated, indicating that exploration and utilization intensity on farmland became much higher than before. The SHDI, SHEI gradually increased from1988to2007, showing that the heterogeneity degree of landscape increased and landscape type had a developing tendency towards complex direction.(3) By using the omprehensive information datebase of land landscape pattern and the regression model, factors influenced the landscape pattern were analyzed. The results show that the factors influencing the landscape type varied from land to land. For these major land use types, climatic and topography are the main factors influencing the landscape pattern.(4) Based on the data of land use/cover change in the three gorges area, the ecosystem service was quantitatively assessed. The results showed that:the ecosystem service value increased by144.04billion Yuan, and the ecological environment land use status were significantly improved from the year1988to2007. Forest land and farm land account for about90%of the ecosystem service value in the TGRA. Decrease in farm land area has significantly adverse impact, while the increase in area of forest land, grass land and water can positively influences on ecological environment. Comparing in different region, the ecosystem service value was much higher in the east part with complicated topography than that in the southwest part with low mountains and hills.(5) In order to lower the risk of soil erosion, the land use structure in TGRA was optimized. After optimization, the area of forest land increased5900Km2, and forest cover increased from10.3%to59.1%. The area of farmland and grassland decreased to33.8%and3.78%, respectively. The increased area of forest land comes from the decreased of farmland with steep slopes, the grassland with low attitudes or unused land with small slopes. Likewise, the soil erosion modulus and soil erosion amount decreased from2514.741km-2a-1,145.02×1061to2068.01t km-2a-1,119.31×106t, respectively. These results showed that soil erosion risk can be significantly decreased and the ecological environment can be substantially promoted after optimization of land use structure, which are benefit to the sustainable development of TGRA.更多还原