Abstract:

The upper reaches of the Minjiang River play a vital role in ecological protection in China. The devastating earthquake on May 12, 2008 had a profound impact on the ecological environment in this region, particularly in the vulnerable arid valley areas that are major human activity zones. To better understand the changes in the ecological environment after the earthquake and explore the driving forces behind ecological vulnerability in this region, this study focuses on the Zagunao River Basin as a case study. Four dimensions, namely “natural environment, geology and landforms, geological hazards, and social environment” were used to select 14 evaluation indicators. Spatial principal component analysis was employed to assess the ecological vulnerability of the area before the earthquake (2001), after the earthquake (2009), and in the current state (2020). Geodetector analysis was used to examine the factors influencing ecological vulnerability, and the ratio of interactive effect variation was calculated to evaluate the individual and interactive effects of driving factors. The results showed that compared to the pre-earthquake and post-earthquake periods, the areas of potential and moderate vulnerability within the region decreased, while the areas of mild, mediumly severe and severe vulnerability increased, indicating an exacerbation of ecological vulnerability. However, over the years of recovery, the areas of potential, mild, and moderate vulnerability increased, while the areas of mediumly severe and severe vulnerability decreased to some extent, indicating a reduction in ecological vulnerability. The regions with the highest ecological vulnerability were the Minshan Mountain and Qionglai Mountain ice erosion and ice edge of the alps and extra-high mountain areas, with mild and severe vulnerable areas accounting for 25.8% and 36.3% of the total area, respectively, indicating a relatively high ecological vulnerability. In the arid valley area, the most widespread distribution was observed in the mild and moderate vulnerability areas, accounting for 46.6% and 33.9% of the total area, respectively, indicating a relatively high ecological vulnerability. In other regions, the potential vulnerability areas accounted for more than 74.5% of the total area, indicating a low ecological vulnerability. Elevation, biological abundance index, vegetation coverage, water conservation index, and drought index were identified as the main driving factors contributing to ecological vulnerability in the region. Among these, elevation had the most direct impact, while vegetation coverage and water conservation index exhibited continuously strengthening indirect impacts on ecological vulnerability. During dry climate periods, the drought index directly influenced ecological vulnerability, and the biological abundance index had a significant direct impact, with its indirect impact on the area's ecological vulnerability increasing after the earthquake. This study provides valuable insights for ecological protection and restoration in the Zagunao River Basin.

Key words: ecological vulnerability assessment, driving factors, interaction effect variation ratio, arid valley area, Geodetector, Zagunao River Basin

摘要：

岷江上游是中国重要的生态屏障，特别是干旱河谷区不但生态环境脆弱，而且是人类活动主要区域。2008年5•12地震对该区域生态环境造成了重大影响。为探索5•12地震前后岷江上游生态环境变化状况，同时探究该区域生态脆弱性驱动机制，以杂谷脑河流域为例，从“自然环境-地质地貌-地质灾害-社会环境”4个维度选取了14个评价指标，基于空间主成分分析对该区域5•12地震震前（2001年）、震后（2009年）及现状（2020年）生态脆弱性进行评价。基于地理探测器分析了生态脆弱性影响因子，并计算交互效应变异比量化了驱动因子的个体效应（直接影响）和交互效应（间接影响）。结果表明，相对于震前震后区域内潜在和轻度脆弱区面积减少，微度、中度和重度脆弱区面积增加，生态脆弱性增强；经多年恢复现今区域内潜在、微度和轻度脆弱区域面积增加，中度、重度脆弱区域面积有不同程度的减少，生态脆弱性降低。岷山、邛崃山冰蚀、冰缘极高山、高山区轻度和重度脆弱区分布最广面积占比分别为25.8%和36.3%，生态脆弱性最高；干旱河谷区微度和轻度脆弱区面积分布最广面积占比分别为46.6%和33.9%，生态脆弱性较高；其他区域主要为潜在脆弱区面积占比均在74.5%以上，生态脆弱性低。高程、生物丰度指数、植被覆盖度、水源涵养指数和干旱指数是区域内生态脆弱性主要驱动因子，其中，高程是最直接的影响因子，而植被覆盖度和水源涵养指数对生态脆弱性间接影响力不断加强，干旱指数在气候干燥时期对生态脆弱性直接影响力增强，生物丰度指数对生态脆弱性直接影响显著，但在震后对研究区生态脆弱性间接影响增强。

关键词: 生态脆弱性评价, 驱动因子, 交互效应变异比, 地理探测器, 干旱河谷区, 杂谷脑河流域