北京市中轴线地区林木树冠覆盖特征及影响因素

Urban Tree Canopy Patches Characteristics and Influence Factors: A Case Study of Central Axis Region in Beijing,China

以北京市中轴线地区为研究对象,2013年8—9月以0.5 m分辨率worldview-2卫星影像为基础,利用GIS面向对象的目视解译方法,对树冠斑块覆盖特征分析,从景观生态学角度揭示研究区"城-乡"梯度带城市森林建设现状、存在问题和影响因素。结果表明:(1)研究区树冠覆盖斑块分布不均衡。从城市中心区向远郊区扩展,中轴线北部地区树冠覆盖率呈现先增后减的趋势,南部地区呈现递减的梯度变化。(2)公共绿地是组成树冠覆盖斑块的的主要绿地类型,单位绿地树冠斑块的破碎度最大,是受人为干扰最强的绿地类型。(3)不同等级树冠覆盖斑块分布不均匀,城市中心区以小斑块居多,大型斑块多分布在远郊区。研究区不同区块之间人文特征、城市建设水平和人居环境质量的差异,是造成区域间树冠斑块景观格局差异的主要原因;城市开展的大规模造林运动,是推动局部地区树冠覆盖斑块面积增长的重要驱动力。

Taking the central axis area of Beijing as the research object,based on worldview-2images with a resolution sensing of0.5m in August September2013,the images were interpreted by using the object-oriented interpreting technology plat-form GIS software.We revealed the present situation,existing problems and influence factors in the“urban-suburb”gradi-ent belt from the perspective of landscape ecology.The results showed that the distribution of tree canopy patches in the study area was uneven.From the city central to the suburb,the tree canopy rate showed increased first and then decreased in the northern of the central axis,and the southern part showed decreased gradient.The public greenland was the main land type that constituted the tree canopy patches.The institutions greenland had the largest degree of fragmentation.From a perspective of scale changes on patch size,downtown was dominated by small-sized patches,large-sized patches mostly distributed in the far suburbs.The humanistic characteristics,urban construction level and living environment quality were the main reasons to make forest canopy patches in regions with different landscape patterns.The tree canopy in local areas was driven by the huge urban greening project.