【作者】 方炫；

【导师】 李壁成；

【作者基本信息】 中国科学院研究生院（教育部水土保持与生态环境研究中心） ， 土壤学， 2011， 博士

【摘要】 黄土高原在我国区域经济发展中具有重要战略地位,而水土流失严重、生态环境恶劣、加之不合理的土地利用加剧了当地土地资源退化和人民生活贫困。宁南山区是黄土高原的典型代表,如何有效恢复生态环境和摆脱落后面貌,是宁南山区乃至整个黄土高原地区的重要课题。在宁南山区开展土地利用格局变化及其生态环境效应研究,提出土地生态功能区规划,是合理利用土地、改善生态环境和人们生活水平的重要途径。宁南山区土地利用相关研究多集中在小流域尺度,开展乡级尺度的土地利用变化研究对于推广验证小流域的土地利用优化成果,弥补小流域在空间尺度上的局限性,形成“村-乡-县”多尺度全面的土地利用动态变化规律,从根本上解决区域性土地合理利用问题有重要理论与现实意义。本文以宁夏自治区固原市河川乡为例,运用“3S”技术,利用早期1:1万地形图与SPOT5遥感影像,在土地资源学与景观生态学理论的指导下,较为全面的研究了乡级尺度的土地利用格局变化及其驱动机制、景观生态效应、土地资源适宜性,提出了生态功能区划方案。论文的主要结果与结论如下:（1）土地利用格局变化分析对河川乡近三十年包括退耕前1982-2002年和退耕后2002-2008年两个时段的土地利用变化进行研究。1982-2002年,土地利用变化以耕地增加与草地减少最明显,2002-2008年林地增加和耕地减少最显著。整个研究时段内,果园持续增加,体现了果园在河川乡农业发展中的重要地位;建设用地持续增加,但数量小速度慢,说明该地区的社会经济落后与发展缓慢;未利用地持续减少;水域面积变化很小。土地利用类型转化的最主要特征为,1982-2002年以草地向耕地转移为主,2002-2008年以耕地向林/草地转移最为显著。河川乡土地利用程度在退耕前由于盲目开垦草地而增加,在退耕后受到退耕还林草作用而有所下降。利用地学信息图谱方法建立了土地利用类型变化图谱、土地利用增减系列图谱,可以从中直观准确地得到不同土地利用的增减状况和转变方式以及它们的空间分布情况。（2）土地利用变化驱动力分析土地利用类型随着地形分布有一定的规律性:耕地多分布在中等海拔、坡度0°-15°的区域分布,灌林地在高海拔、15°-35°分布较多,果园和建设用地都选择在0°-8°地势地平区域分布,草地选择坡度大于25°地段分布。土地利用变化的社会经济驱动力呈现阶段性特征,1982-2002年,耕地增加与草地退化主要驱动力是经济,林地增加主要驱动力是科技与政策,果园增加驱动力是科技、政策与经济;2002-2008年,耕地锐减与灌林地大幅度增加的最主要驱动力是政策,果园增加主要驱动力是经济。（3）土地利用景观格局变化与生态效应评价1982-2008年,河川乡景观格局经历了耕地和草地占共同主导-耕地绝对主导-林地、草地、耕地协调共存的过程,总体上景观优势度下降、多样化提高;景观结构总体上是向可持续方向发展,生态服务价值由1928.43万元增加为3295.61万元。河川乡景观格局与生态服务功能存在地域性,如靠川地分布的骆驼河村、上黄村、明川村和寨洼村景观破碎度、多样性水平、生态服务价值较高。（4）不同土地利用方式下的土壤碳氮特征土地利用方式是土壤碳氮含量分布及碳密度分布的重要因素。不同的土地利用方式下土壤碳氮含量及有机碳密度均表现为:灌木林地与天然草地碳氮水平较高,耕地较低,人工草地与耕地水平相似。不同土地利用方式的平均有机碳密度分别为:灌木林地6.74 kg m^-2,天然草地6.32 kg m^-2,人工草地4.05 kg m^-2,弃耕地5.69 kg m^-2,耕地4.11 kg m^-2,果园4.65 kg m^-2。整个河川乡平均有机碳密度为5.67 kg m^-2,略高于黄土高原平均水平,总碳储量为1148541.66吨。土地利用格局的合理变化对有机碳储量增加有重要意义,灌木林地和天然草地是增加碳汇与控制土壤侵蚀的最有效的土地利用方式,退耕还林对土壤碳储量的增加发挥重要作用。（5）土地资源适宜性评价选取海拔、坡度、坡向、土壤有机质、土壤侵蚀和水源条件六个指标作为土地适宜性评价因子。按照农、林、牧顺序优先选择,将研究区土地资源划分为五类,高度宜农地占总面积的4.86%,中度宜农地占16.73%,宜林地占3.98%,宜林牧地分布最广,占53.77%,宜牧地比例为20.67%。（6）生态功能区划在宁夏“六盘山生态经济圈规划”框架下,结合土地利用格局分析、生态系统服务功能评价和土地资源利用适宜性评价结果,将河川乡划分出北山水土保持生态保护区、川地高效生态农业区和南山旱作农业区三个功能区:北山水土保持生态保护区面积13820.53ha,占河川乡总面积的64.13%,地形破碎、土壤侵蚀严重,土地利用方向是恢复植被、保持水土、涵养水源;川地高效生态农业区面积为4627.91ha,占总面积的21.46%,土地较为平整,水肥条件较好,土地利用方向为高效生态农业;南山旱作农业区面积3110.45ha,占总面积的14.4%,土地发展方向为建设旱作基本农田,保障粮食生产。更多还原

【Abstract】 Loess Plateau has an important strategic position in China’s regional economic development, and it has serious soil erosion, bad ecological environment, and poor land use management which exacerbated the degradation of land resources and the poverty of people living. Southern Ningxia is a typical representative of the Loess Plateau. How to restore the ecological environment and get rid of poverty is an important subject for Southern Ningxia and the whole Loess Plateau. Carrying out the study on land use change and its effect on the ecological environment in Southern Ningxia and proposing the ecological function zoning is crucial for rational use of land and improving the eco-environment and people’s living standards. Studies on land use in Southern Ningxia focused on the small watershed scale. It is of a great thoretical and practical significance to develop the township scale land use change in order to promote and verify the results of optimizating small watershed land use, make up for the limitations of small watershed scale in space, form a law of "Village - Township - County" multi-scale comprehensive land use dynamic changes, and solve the problem of rational use of regional land fundamentally.In this dissertation, taking Hechuan Town in Guyuan City, Ningxia Hui Autonomous Region as an example, using 1:10000 topographic maps and remote sensing image, under the guidance of the technology of GIS and the theory of land resource science and landscape ecology science, and topographic maps, the change of land use pattern, its driving mechanism and ecological effects, suitability and optimized model of land resources, and ecological function zoning at town scale are studied roundly. The main results and conclusions of this paper are as follows:（1） Change of land use pattern Analysis on change of land use pattern was conducted between the time period of 1982 to 2002 and the time period of 2002 to 2008 in Hechuan Town. Results indicated that the most significant change from 1982 to 2002was the increase of arable land and the decrease of grassland, and that the most significant change from 2002 to 2008 was the increase of forest land and the decrease of arable land. Throughout the study period, the orchard was increasing which reflects its important role in agricultural development in Hechuan Town. The residential area was increasing slowly, indicating that the region’s social and economic was poor and its development was slow. In addition, unused land was declining and water area change little. The main types of land use conversion from 1982 to 2002 and from 2002 to 2008 were transferring grassland to arable land and transferring arable land to forest land or grassland, respectively. The degree of land use increased because of the blindfold and excessive grassland reclamation before the Grain for Green project and declined because of the Grain for Green project. With the Geo-informatic Tupu method, the Tupu on land use change and arasing and falling series of land use change was established, from which the characteristics of the increase or decrease of some land use type, the conversion type, and their spatial distribution can be obtained exactly and intuitionisticly.（2） Driving forces of land use changeThe distribution of land use pattern has a certain regularity with topographic change: arable land are located in medium altitude and 0°-15°slope, the shrub land are located at high altitudes, 15°-35°slope, the orchards and residential are located at 0°-8°slope and low altitude, and the grassland are located at slope greater than 25°.The characteristics of the socioeconomic driving forces on land use change: in 1982-2002, the main driving force of the increase of arable land and the grassland degradation was economic, the main driving forces of the increase on forest land were science, policy and technology, the main driving force of increasing orchards were technology, policy and economy. In 2002-2008, the main driving force of the decline of arable land and the increase of shrub land was policy; the main driving force of increasing orchards was economy.（3） Landscape change and its ecological effectsThe landscape pattern of Hechuan Town from 1982 to 2008 experienced an“arable land and grassland dominated - arable land dominated - coordination of forest, grassland, arable land in propotion”process. The landscape dominance declined, and the diversity increased. The landscape structure developed in the direction of sustainability on the whole. The value of ecosystem services increased from 19,284,300 yuan to 32,956,100 yuan. The landscape patterns and the ecosystem services value existed regional differences. For example, the counties distributed by the flat land, such as Luotuohe, Shanghuang, Mingchuan and Zaiwa, had higher landscape fragmentation, diversity and ecological services value.（4） Effect of land use on soil carbon and nitrogenLand use is an important factor on the distribution of soil carbon and nitrogen content and carbon density. The characteristic of soil carbon and nitrogen content and organic carbon density under different land uses are as follows: the carbon and nitrogen under shrub land and natural grassland was significantly greater, the carbon and nitrogen under arable land was significantly lower, and the carbon and nitrogen under grassland and arable land were in same level. The organic carbon density under shrubland, natural grassland, artificial grassland, cropland, abandoned cropland, and orchards were 6.74, 6.32, 4.05, 5.69, 4.11, 4.65 kg m^-2, respectiveily. The organic carbon density in Hechuan Town was 5.67 kg m^-2, slightly higher than the average level of the Loess Plateau, and the total carbon storage was 1,148,541.66 tons. Rational land use pattern change is of a great significance on the increasing soil organic carbon storage. Shrub land and grassland are the most effective land uses to increase carbon sequestration and control soil erosion. The Grain for Green project plays an important role on the increase of soil carbon stocks.（5） Suitability evaluation of land resourcesThe six indicators, including altitude, slope, aspect, soil organic matter, soil erosion and water conditions, were selected as the land suitability evaluation factors. In accordance with the order of agriculture, forestry and stockbreeding, the study area was divided into five categories of land resources, including the land highly suitable for agriculture, the land moderately suitable for agriculture, the land suitable for forestry, the land suitable for both forestry and stockbreeding, and the land suitable for stockbreeding, accounting for 4.86%, 16.73%, 3.98%, 53.77% and 20.67%, respectively.（6） Ecological function zoning of land useUnder the Ecological Economic Zone Liupanshan Planning Framework, according to the land use pattern analysis and the results evaluation of ecosystem services and land use suitability evaluation, Hechuan Town was divided into three functional regions: soil and water conservation eco-environmental protection region in north mountain district, high efficiency ecological agriculture region in flat district, and dry farming region in south mountain district. Soil and water conservation eco-environmental protection region in north mountain district areas 13820.53ha, accounting for 64.13% of total area with broken terrain and severe soil erosion, the direction of land use in this region is to restore the vegetation, conserves the soil and water. High efficiency ecological agriculture region in flat district areas 4627.91ha, accounting for 21.46%. The land is flat with good water and fertilizer conditions. The land use direction is to develop the efficient ecological agriculture. Dry farming region in south mountain district areas 3110.45ha, accounting for 14.4 %. The land use direction is to construct basic dry farming land and ensure the food production.更多还原