长三角地区城市森林建设的空间关联及影响因素分析

Analysis of Spatial Correlation and Influencing Factors of Urban Forest Construction in the Yangtze River Delta Region

[目的]构建长三角城市森林建设水平指数,揭示长三角地区城市森林建设的空间关联性及其空间关联的演化特征,突破以往区域间要素互为独立的壁垒,在空间视角下分析各影响因素对长三角城市森林建设长期和短期的直接效应和溢出效应,为差异化城市森林建设、长三角森林城市群统筹建设和长三角生态绿色一体化发展提供参考和决策依据。[方法]基于熵权TOPSIS法构建城市森林建设水平指数,将城市森林建设的生态效益纳入其中,衡量2006—2019年长三角41个地级市的城市森林建设水平,通过地域相邻矩阵等3种空间权重矩阵,利用动态空间杜宾模型分析城市森林建设的空间溢出效应以及城市经济社会发展、创建森林城市等因素对城市森林建设水平长期和短期的间接效应和直接效应。[结果]1)基于空间距离倒数的空间权重矩阵符合长三角城市森林建设的广泛空间关系,长三角地区城市森林建设的全局莫兰指数在0.244 3以上,呈现波动上升走势;2)长三角41个地级市城市森林建设在空间上表现出稳定的空间块状集群异质性特征,“高-高”(H-H)值集聚,均集中在上海、江苏、浙江一带,形成沿海往内陆扩散的发展态势;“低-低”(L-L)值集聚,多集中在安徽省,呈先扩散后收缩的走势;3)长三角城市森林建设的空间溢出效应在0.172左右,短期和长期人均地区生产总值对城市森林建设水平的直接效应分别为-0.014 2和0.091 4;创建森林城市短期直接效应与溢出效应均显著为正,但长期为负;人口密度、旅游人数、第三产业占比对城市森林建设水平的影响存在短期降低、长期提升的差异。[结论]长三角地区城市森林建设存在显著空间关联性,短期内经济发展给长三角地区城市森林建设水平带来压力,长期来看经济发展可带动城市森林发展;人口密度和旅游人数、第三产业占比增加会迫使管理者注重生态保护,以期望获得更大的生态效益;人均道路面积增加短期内可改善该城市的森林建设水平并辐射带动相邻城市,长期来看反而限制城市森林进一步发展的空间;创建森林城市成功后的一段时间内管理者可能进一步提高城市森林建设水平,并对周围城市森林建设产生积极影响,但长期缺乏持续性。

【Objective】By constructing the Yangtze River Delta urban forest construction level index,we reveal the spatial correlation of urban forest construction in the Yangtze River Delta region and the evolutionary characteristics of its spatial correlation,break through the previous barriers of inter-regional elements being independent of each other,and analyze the direct and spillover effects of each influencing factor on the long-term and short-term urban forest construction in the Yangtze River Delta in a spatial perspective.To provide reference and decision-making basis for the construction of differentiated urban forests,the integrated construction of the Yangtze River Delta forest city cluster and the integrated ecological green development of the Yangtze River Delta.【Method】The entropy-weighted TOPSIS method is used to construct a comprehensive urban forest construction index,which incorporates the carbon sequestration benefits of urban vegetation and measures the urban forest construction level of 41 cities in the Yangtze River Delta from 2006 to 2019,and the dynamic spatial Durbin model is used to analyze the spatial spillover effects of urban forest construction and the short-and long-term indirect and direct effects of factors such as urban economic and social development and the creation of forest cities on the urban forest construction level.【Result】1)The spatial weight matrix based on the inverse of spatial distance is consistent with the extensive spatial relationship of urban forest construction in the Yangtze River Delta,and the global Moran index of urban forest construction in the Yangtze River Delta shows a fluctuating upward trend above 0.2443.2)Urban forest construction in 41 cities in the Yangtze River Delta exhibits stable spatially blocky cluster heterogeneity in space.“High-high”(H-H)value clusters,all concentrated in Shanghai,Jiangsu and Zhejiang,forming a development trend of coastal to inland diffusion;the“low-low”(L-L)value clusters are mostly concentrated in Anhui Province,and show a trend of diffusion first and then contraction.3)The spillover effect of urban forest construction in the Yangtze River Delta is around 0.172,and the direct effects of per capita GDP on the construction level of urban forest in the short and long term are-0.0142 and 0.0914,respectively.The direct and spillover effects of creating forest cities are significantly positive in the short term,but negative in the long term.There are differences in the short-term decrease and long-term increase of the effects of population density,tourism,and tertiary industry share on the construction level of urban forest.【Conclusion】There is a significant spatial correlation in the construction of urban forests in the Yangtze River Delta region,economic development puts pressure on the level of urban forest construction in the Yangtze River Delta region in the short term,while economic development drives the development of urban forests in the long term.The increase in population density and tourism and the share of tertiary sector in the long term may force managers to focus on ecological conservation in the hope of obtaining greater ecological benefits.The increase in road area per capita improves the level of forest construction in the city in the short term and radiates to neighboring cities,but in the long term it limits the space for further development of urban forests;after the success of creating a forest city for a period of time managers may further improve the level of urban forest construction and have a positive impact on the forest construction in surrounding cities,but lacks sustainability in the long term.