Spatiotemporal trends of terrestrial vegetation activity along the urban development intensity gradient in China's 32 major cities.
Spatiotemporal trends of terrestrial vegetation activity along the urban development intensity gradient in China's 32 major cities.
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DOI：
10.1016/j.scitotenv.2014.04.080
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发表时间：
2014-08
期刊：
影响因子：
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通讯作者：
Decheng Zhou;Shuqing Zhao;Shuguang Liu;Liangxia Zhang
中科院分区：
文献类型：
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作者：
Decheng Zhou;Shuqing Zhao;Shuguang Liu;Liangxia Zhang
陆地植被在城市系统中扮演着重要的角色。然而，人们对城市化对植被的影响知之甚少。利用MODIS增强型植被指数（EVI），研究了2000 - 2012年中国32个主要城市沿着城市发展强度（UDI）梯度的植被活动时空变化趋势。我们还建议使用一组新的概念（即，实际的、理论的和积极的城市化效应），以更好地理解和量化城市化对植被活动的影响。结果表明，随着UDI的上升，32个城市中有28个城市的EVI呈线性、凸状或凹状沿着显著下降（p< 0.05），表明城市化对植被的影响在城市和城市内UDI区之间存在差异。此外，实际的城市化效应比理论估计的要弱得多，因为多种城市环境和人为因素产生了抵消性的积极影响。通过检查各个UDI区域的EVI相对于农村地区的EVI（ΔEVI）的相对变化，有效地消除了气候变率的影响，结果表明，2000年至2012年，郊区约四分之三的城市的ΔEVI显著下降。在城市（0.05 <UDI≤ 0.25）和郊区（0.25 <UDI≤ 0.5），只有一半的城市在市区（0.5 <UDI≤ 0.75）和城市核心区（0.75 <UDI≤ 1）。许多城市的城市和城市核心区的ΔEVI呈稳定甚至上升趋势，这主要归因于城市环境的积极影响以及城市绿色空间管理和维护的改善。需要做更多的工作来机械地量化城市环境因素和管理做法对植被活动的详细负面和正面影响。
Terrestrial vegetation plays many pivotal roles in urban systems. However, the impacts of urbanization on vegetation are poorly understood. Here we examined the spatiotemporal trends of the vegetation activity measured by MODIS Enhanced Vegetation Index (EVI) along Urban Development Intensity (UDI) gradient in 32 major Chinese cities from 2000 to 2012. We also proposed to use a new set of concepts (i.e., actual, theoretical, and positive urbanization effects) to better understand and quantify the impacts of urbanization on vegetation activities. Results showed that the EVI decreased significantly along a rising UDI for 28 of 32 cities (p< 0.05) in linear, convex or concave form, signifying the urbanization impacts on vegetation varied across cities and UDI zones within a city. Further, the actual urbanization effects were much weaker than the theoretical estimates because of the offsetting positive effects generated by multiple urban environmental and anthropogenic factors. Examining the relative changes of EVI in various UDI zones against that in the rural area (ΔEVI), which effectively removed the effects of climate variability, demonstrated that ΔEVI decreased markedly from 2000 to 2012 for about three-quarters of the cities in the exurban (0.05 <UDI≤ 0.25) and suburban (0.25 <UDI≤ 0.5), and only half of the cities in the urban (0.5 <UDI≤ 0.75) and urban core (0.75 <UDI≤ 1). The stable or even increasing tendencies of ΔEVI in the urban and urban core of many cities could primarily be attributed to the importance of positive effects derived from the urban environment and the improvement of management and maintenance of urban green space. More work is needed to quantify mechanistically the detailed negative and positive effects of urban environmental factors and management practices on vegetation activities.