恢复力视角下生态型城市植被恢复空间分异及其影响因素——以陕南商洛市为例

植被恢复是建设生态型城市的重要途径,通过明晰植被恢复空间分异与潜在的植被恢复力,有助于指导可持续性生态城市的建设。以商洛市为例,基于MODIS归一化植被指数(NDVI)数据,利用Sen+Mann-Kendall模型和Hurst模型研究2000—2013年商洛市植被恢复趋势及未来持续能力,并采用地理加权回归模型(GWR)分析市域尺度内植被恢复空间分布的影响因素。结果表明:(1)2000—2013年商洛市的植被恢复效果明显,植被覆盖增大的区域占总面积的82.5%,减小的区域占总面积的9.4%;(2)2000—2013年,受城镇的距离及土地集约程度等人文因素的影响,西北部植被恢复略好于东南部。(3)Hurst指数显示,商洛市未来植被恢复的持续性不强。48.0%的区域未来植被覆盖可能会呈现由改善变退化的现象,而持续增大的区域仅占36.7%,植被恢复力仍有待加强。(4)市域尺度上,植被恢复趋势空间差异形成的自然因素包括高程、坡度、坡向、与水体的距离,而人文因素则由距离城镇的距离和土地利用集约度所主导。地理加权回归显示各区县植被恢复趋势的空间影响因素及其强度并不一致,充分说明人地关系变化对植被恢复作用机理的复杂性。

A resilience-based analysis on the spatial heterogeneity of vegetation restoration and its affecting factors in the construction of eco-cities: a case study of Shangluo, Shaanxi

Although China''s economy is rapidly growing, its environmental is experience a dramatic degradation simultaneously, so the construction of eco-cities plays a key role in the restoration of environmental sustainability. As an important part of ecological restoration, vegetation restoration is able to prevent water loss, soil erosion and accompanied soil nutrient loss, so it has been widely incorporated into the construction of eco-cities. Therefore, by analyzing the spatial heterogeneity and the potential ability of vegetation restoration, we can formulate a series of measures to analyze the ecological restoration, aiming to promote the construction of eco-cities sustainably. The normalized difference vegetation index (NDVI) was adopted in this analysis, which can reflect the status of vegetation growth and thus has been widely used in the study of vegetation dynamics. In order to understand vegetation resilience to impacts from the socioeconomic and environmental systems and thus to promote the construction of eco-cities, we build up a set of measurements and choose Shangluo in Shaanxi province as our study area. A combination of the statistical tests, including Theil-Sen, Mann-Kendall, and Hurst is calculated to investigate the vegetation dynamics during the restoration period from 2000 to 2013. Then, the geographically weighted regression (GWR) is adopted to analyze the affecting factors that underlying the spatial distribution of vegetation dynamics during the restoration period. The results show that from 2000 to 2013: (1) The vegetation restoration has contributed to the vegetation increase in Shangluo City, as there was a net increase of NDVI value across the entire region. (2) Due to the influences of anthropogenic factors such as the distance to the town and the intensity of land use, the vegetation restoration in northwest of Shangluo is slightly better than the southeast. (3) The Hurst index reveals that the sustainability of vegetation restoration in Shangluo is not consistent in the future, as the positive sustainability accounted for 44.0% of their region. Furthermore, 48.0% of the entire region may experience degradations in the future, and only 36.7% of the region would keep increasing. So it needs to introduce new managements and policies to enhance and monitor the vegetation recovery. (4) The spatial heterogeneity of the vegetation restoration across the entire Shangluo is mainly determined by the natural factors, including elevation, slope, slope-exposure, and distance to water, where the main anthropogenic factors are the intensity of land use and the distance to the town. The affecting factors of vegetation restoration are different among counties with various degrees at the city scale, which reflects that the mechanism on man-land relationship change with the vegetation restoration is complicated. In the social-ecological system, a single index cannot explain the impact factors of vegetation restoration accurately. The analysis of NDVI changes and their driving forces in Shangluo helps to understand the factors in vegetation restoration such as climate, topography, and the policy (such as the Grain to Green Program). The work provide important implications for the policy-makers and relevant stakeholders in the construction of eco-cities.