基于景观结构和空间统计方法的绿洲区生态风险分析——以石羊河武威、民勤绿洲为例

论文以石羊河流域武威、民勤绿洲为研究区域,在ArcGIS 10.0、ArcView 3.2 软件和景观格局分析软件FRAGSTATS的技术支持下,采用干扰度指数、景观脆弱度指数、优势度指数和破碎度等指数,并通过分析景观格局与生态风险度之间的关系,将各景观指数进行栅格叠置运算,从而构建生态风险度,在此基础上,利用GIS局部空间统计方法研究分析了绿洲区景观结构格局和生态风险的时空变化特征及聚集模式。研究结果表明:① 城乡用地快速扩展的同时,耕地和草地景观有较大幅度的降低,优势景观类型由耕地、草地向耕地和建设用地转变;② 武威绿洲生态风险经历了从较高到中度的转变,生态风险整体趋于好转,而民勤绿洲生态风险从中/较高到较高/高变化,生态风险有所恶化;③ 武威绿洲主要为高于平均值的要素趋于聚集,表现为低生态风险小区高度聚集,且聚集度有上升的趋势,而民勤绿洲则主要为低于平均值的要素趋于聚集,高生态风险小区高度聚集,随着时间的推移呈现面积增大、空间扩展的态势。

Eco-risk Analysis of Oasis Region Based on Landscape Structure and Spatial Statistics Method—A Case Study of Wuwei and Minqin Oases

Eco-risk assessment is a hotspot arising in recent 20 years, due to the spatial heterogeneity and the complexity in assessment, as well as an integrated junction for geography, ecology, and environment risk evaluation. The study of ecological risk is helpful for understanding local ecological environment, reducing ecological risk, and finally improving the interactions between human beings and nature. To reveal the impact of ecological risk of oasis change in the small watershed of the Shiyang River Basin, Wuwei and Minqin oases were chosen as the study area. Landscape information was obtained from satellite remote sensing TM images of 1987, 2000 and 2010. The grid by 4 km×4 km was created as the auxiliary evaluation unit, and the GIS technology was employed as the data integration analysis platform. In order to generate the map of oasis eco-risk in 1987, 2000 and 2010, the spatial overlay method was used to make the index a spatial variable. Besides, the landscape interference index, fragile landscape degree, landscape dominance index and fragmentation index were used to analyze the relationship between landscape pattern and the eco- risk degree through the supporting of ArcGIS 10.0, ArcView 3.2 and FRAGSTATS softwares. Besides, based on the overlay analysis of every netfish of the landscape index, the eco-risk degree was reflected by spatial expression. Meanwhile, the spatial statistic method was also used to analyze the spatio-temporal process of landscape structures and ecological risk. The results showed that: 1) the urban and rural land expanded rapidly from 1987 to 2010. At the same time, the farmland and grassland decreased at a large scale, and the preponderant landscape changed from farmland and grassland to farmland and construction land. 2) The Wuwei oasis ecological risk has experienced the transition from high to moderate change, and the ecological risk as a whole tended to be better while the Minqin oasis eco-risk turned from medium /higher- risk to higher- risk/highest- risk. The ecological risk of the whole study area was deteriorated in the past 20 years. 3) The Wuwei oasis elements mainly tended to cluster and its value was higher than the average. It showed the low eco- risk area was much more clustered, and the trend was increasing. Comparatively, the elements of Minqin oasis that were lower than the average tended to be clustered, the high eco-risk area clustered extremely. It also showed that the cluster characteristics increased in area and expanded in space. Therefore, Wuwei oasis should expand the scale of the facilities of agriculture or high-efficiency water saving. At the same time, the ecological key factors such as forest for conservation of water supply and alpine grassland should be protected. What's more, desertification governance in Minqin oasis is particularly important. Through the grass square, cotton stem, corn straw, drought-tolerant plants can effectively manage desertification, and improve the resistance of eco-environmental change.