喀斯特山区县域耕地景观生态安全及演变过程

Abstract

为探讨喀斯特山区耕地生态环境变化状况，基于景观生态安全理论，以贵州省赤水市耕地景观为研究对象，选取景观生态安全指数、景观接近度指数、景观类型斑块破碎度、景观类型边界破碎度、景观类型斑块优势度指数、景观分离度指数、景观脆弱度指数等7个景观指数构建喀斯特山区耕地景观生态安全评价模型，分析2000-2014年研究区耕地景观生态安全的演变过程，试探耕地生态安全重心转移方向和驱动因素。结果表明：1）近15年来赤水市耕地景观生态安全重心向西北方向移动，耕地景观斑块密度、分形维数、破碎度下降，斑块形状指数、连接度上升，耕地形状逐渐向复杂状态转变，且分布趋于均匀化，斑块变得越来越群聚。2）耕地面积持续减少、生态安全性不断降低，旱地景观生态安全Ⅰ级区（危险区）向东南部地区扩张，Ⅲ级区（安全区）向Ⅱ级区（相对安全区）转变，Ⅱ级区向Ⅰ级区转变；水田景观生态安全Ⅱ级区由集中呈发散分布，Ⅲ级区向Ⅱ级区、Ⅰ级区转变，旱地和水田景观的生态安全不容乐观。3）通过灰色关联分析得出对研究区旱地景观生态安全演变及重心转移影响最大的因素是农业总产值，其次是粮食产量和农作物播种面积；对水田景观影响最大的是粮食产量，其次是单位化肥施用量和人口密度。;The ‘No. 1 Central Document’ issued in 2016 pushed the ‘three rural issues’ to the cusp. As an important component of the agricultural landscape, the features of the farmland landscape would directly affect the inside ecological processes and productivity of cultivated land, so as to finally decide whether the food problem of the 1.3 billion people in China can be solved or not. In order to investigate changes in the ecological environment of cultivated land in the Karst mountain area on the basis of landscape ecological security theory, the farmland of Chishui City (Guizhou Province, China) was selected as the research object in this essay. Firstly, datas like patch density, patch shape index, patch fractal dimension and patch stability factor were picked out and be used in order to analyse the characteristics of landscape patch evolution and spatial distribution of landscape pattern in the Karst mountain area. Secondly, a landscape ecological security evaluation model for farmland in the Karst mountain area should be constructed to analyze the evolution of the cultivated land's landscape ecological security from 2000 to 2004. In this step, ecological security index, patch proximity index, patch fragmentation, patch boundary fragmentation, landscape type patch dominance index, separation index, and landscape fragile index were used. Thirdly, on this basis of the past two steps, the centroid method commonly used in geography and economics was introduced to calculate the gravity center of the landscape ecological security of cultivated land. In the same time, both the gravity transfer distance model and the moving direction model were used to measure the distance and direction of the ecological safety center of cultivated landscapes. Finally, to explore the driving factors of ecological safety evolution and center of gravity shifts based on regional characteristics, 10 indices were selected, namely, population density, proportion of agricultural population, rate of regional construction land, grain yield, unit of cultivated land fertilizer, arable area, gross output value of agriculture, per capita disposable income of farmers, crop sown area, and number of rural practitioners, and a grey correlation analysis was performed for changes in the indices and changes in the ecological security indices of the cultivated landscape. The results showed as follow. Firstly, in the recent 15 years, the ecological security center of gravity of cultivated land landscape in Chishui moved to the Northwest. Meanwhile the patch density, fractal dimension, and fragmentation decreased, the patch shape index and connection degree increased. The shape of the cultivated land gradually changed to a complex state, and the distribution tended to be homogeneous, whereas the patches became increasingly clustered. Secondly, arable land continued to decline, ecological safety decreased. According to the landscape ecological security index of cultivated land calculated results, it could be seen that the ecological security zone of dry land landscape was expanding to the southeast, and the safe areas was changed to the the relatively safe areas, and the relatively safe areas was changed to the dangerous areas; The relatively safe areas of paddy field landscape changed from a centralized distribution to a divergent distribution, the safe areas transformed the relatively safe areas and hazardous areas. The ecological security of dry land and paddy field landscape was not optimistic. Thirdly, the gray analysis results indicated that the driving factors that affect the evolution of landscape ecological security and the transfer of gravity in dry land of the study area were obtained, and the maximum was the total agricultural output value, followed by grain yield and crop sown area. Grain yield was the most important factor affected by the evolution of landscape ecological security and gravity transfer in paddy fields, followed by the level of fertilizer application and population density.