基于格局-过程生态适应性循环三维框架的自然景观生态风险评价——以黄土高原为例

传统的景观生态风险评估侧重于评价景观镶嵌体相对于最优格局的偏离程度,忽视生态系统过程和景观类型内部分异,使得黄土高原景观生态风险评估存在一定的片面性。综合"格局-过程"的生态适应性循环三维框架,构建适合自然生态系统的景观生态风险评价指标体系,对黄土高原2000年、2010年、2017年的景观生态风险进行评估。从空间分异来看,相较于传统的景观格局风险指数法仅在沙漠景观呈现高风险单一结果,本研究结果显示黄土高原景观生态风险由高到低依次为城市和沙漠景观、中部丘陵沟壑区草地景观、西北荒漠草地景观和东南部农田景观、东南部高山林地景观,具有明显空间分异。从时间变化来看,生态工程实施以来黄土高原景观生态风险总体呈现持续下降趋势,平均值由0.410降低到0.385,但2010-2017年下降不明显,生态工程持续实施对景观生态风险持续下降作用变弱。其中,自然景观（林地和草地）受生态工程促进生态风险持续降低,而人工景观（城市和农田）尤其是城市范围的不断扩大促使区域生态风险升高明显,建议加强城市土地集约高效利用,同时限制北部环境恶劣小城镇的发展。此外,中部丘陵沟壑区草地恢复力不足和降水侵蚀力增强也会促使风险升高,建议在生态保护时给予重点考虑。

Natural landscape ecological risk assessment based on the three-dimensional framework of pattern-process ecological adaptability cycle: a case in Loess Plateau

Recent ecological hazards frequently occurred due to natural ecosystems under direct or indirect pressures and stresses from human society with accelerating changes. In 2019, President Jinping Xi stated that the ecological protection and high-quality development for Yellow River Basin, as an important ecological barrier in China, are critical national needs. Additionally, on behalf of the people of different groups, the health of natural environment and sustainable development of ecology attracts full attention. Especially the Loess Plateau, which experienced the heaviest soil erosion in the middle reaches of the Yellow River basin, is an important object of ecological engineering. Therefore, assessing landscape ecological risk in the Loess Plateau lays an important scientific foundation for optimizing regional natural ecosystem security pattern, and serves ecological protection and high-quality development in the Yellow River Basin. However, traditional landscape ecological risk assessment based on evaluating the deviation degree of landscape mosaics from the optimal pattern was biased at Loess Plateau due to underestimating the difference between landscape types and ecosystem processes. Therefore, a landscape ecological risk assessment index system should be further developed based on a comprehensive pattern-process ecological adaptability cycle three-dimensional framework. The landscape ecological risks of the Loess Plateau are then respectively evaluated in 2000, 2010, and 2017. The results of the spatial distribution were significantly different from the simple phenomenon of high risk only in desert landscapes using the traditional landscape pattern risk index method. The ecological risk show descending tendency in the following four regions, urban and desert landscapes, grassland landscapes in the middle of hilly and gully areas, desert grassland landscapes in the northwest, farmland landscapes in the southeast, and alpine woodland landscapes in the southeast. Additionally, the average value of landscape ecological risk has been decreasing from 0.410 to 0.385 whilst implementing the grain for green project between 2000 and 2017. It is worth noting that, the impact of ecological project on the sharp decline of landscape ecological risk becomes weaker in recent years, according to the slightly decrease tendency from 2010 to 2017. Further, although natural landscape units (i.e. woodland and grassland) have been made better by ecological projects, the ecological risks in artificial landscapes (i.e. cultivated field and construction land) have been decreasing due to urban expansion. We strongly suggest to strengthen the intensive and efficient use of urban land and restrict the development of small towns with harsh environments in the north. Serious considerations for ecological protection should also be taken into in hilly and gully region in the central Loess Plateau since insufficient vegetation restoration and increased precipitation erosion at this region will also increase the risk.