高原河谷城镇化对植被覆盖度的影响

以典型的高原河谷城市——西宁市为例,定量分析了2000-2015年研究区景观格局及植被覆盖度的时空演变,揭示了高原河谷地区的城镇建设对植被覆盖度的干扰过程及生态环境质量的影响。结果表明：（1）2000-2015年间,西宁市城镇面积增幅为25.99%,总体城镇化率为4.76%,各区县城镇化水平差异较大;（2）西宁市平均植被覆盖度呈增加趋势但不显著（P < 0.57）。植被覆盖度以中高和高植被覆盖度为主,空间上呈现"东西低-南北高"的分布特征,退耕（牧）还林（草）区的植被覆盖度显著增加（P < 0.01）,说明生态恢复工程效果显著;（3）区县尺度上,城镇化速率与中高覆盖植被面积变化呈显著负相关（P < 0.01）,区县内生态质量有所下降,城镇发展程度和区位条件的差异是影响中高覆盖度植被变化的主要因素;（4）格网尺度上,建成区及其周边区域的低覆盖植被面积呈显著增加趋势（P < 0.01）,表明城镇内部区域生态质量有所改善。研究结果对保护和提高西宁市生态环境质量及合理推进城镇建设等方面具有重要意义。

Impact of urbanization of plateau valley on vegetation coverage

This paper took a typical plateau river valley city - Xining City as an example and quantified the spatiotemporal patterns of urban expansion and vegetation cover from 2000 to 2015. We then analyzed the impact of urban construction on vegetation coverage and the quality of the ecological environment. The results showed that: (1) From 2000 to 2015, the area of build-up lands increased by 25.99%, whereas the urbanization rate was 4.76%. Meanwhile, the urbanization levels of different districts and counties varied widely; (2) There was a slight but insignificant increasing trend in vegetation coverage (P < 0.57). The city was dominated by Medium-High and High vegetation coverage, in which spatially distributed characteristics are "east-west low and north-south high". The vegetation coverage in the area of returning farmland (grazing) to forest (grass) has increased significantly (P < 0.01), suggesting the restoration project achieved significant effects; (3) On the district or county scale, the urbanization change rate and the medium-high coverage vegetation change trend showed a significant negative correlation (P < 0.01). Different degree of urban development and location conditions are the main factors affected the medium-high coverage vegetation; (4) On the grid-scale, the area of low-cover vegetation in the built-up area and its surrounding areas showed a significant increase (P < 0.01), indicating that the quality of the ecological environment in urban areas has improved; The research results are of great significance for protecting and improving the quality of the ecological environment of Xining City and for rationally advancing urban construction.