西藏城乡居民点空间分异特征与影响因素

Spatial differentiation characteristics and influencing factors of urban and rural settlements in Tibet,China

西藏地处青藏高原腹地,区内适宜人类生活的空间十分有限,居民点空间分布受多因素制约.为揭示西藏居民点的空间分布特征和主要影响因素,采用高分影像,基于目视与机器解译结合提取西藏城乡居民点斑块数据,运用核密度、空间热点探测、GeoDetector等方法探索其空间分异特征与影响因素,以期为今后高原地区宜居地选址、制定区域经济发展等相关政策提供参考.结果表明:西藏城乡居民点呈聚集分布模式,整体密度分布差异较大;呈以拉萨市为高密度核心,昌都市、林芝市、阿里地区为低密度边缘的"核心-边缘"结构;高密度核心区拉萨市斑块密度多达220 ind·km^-2,而低密度边缘区密度最大仅为5.7 ind·km^-2,两个区域相差43倍.西藏城乡居民点规模高低值聚簇现象显著,大斑块高值数量稀少,小斑块低值数量绝对优势突出;大斑块高值占比仅为3.7%,集中分布于拉萨市和山南市,低值聚簇区占比达到67.2%,主要分布于羌塘高原的阿里地区和那曲市.西藏城乡居民点被划分成6种类型,形成了以"一江两河"地区和"三江流域"为中心的两个圈层结构,由内到外依次为大斑块主导型、中密度团簇型、高密度散点型、低密度散点型和高寒地无人型;拉萨市以中密度团簇型为主,占比为31%,山南市以低密度散点型为主,占比为38%,昌都市以低密度散点型为主,占比高达51%,阿里地区、那曲市和日喀则市均以高寒地无人型为主,其中,在阿里地区占比高达64%.不同影响因子对西藏城乡居民点空间分布的影响程度差异性显著;人口和GDP对城乡居民点的分布均具有很强的决定性;此外,城镇居民点表现出强烈的道路指向性,农村居民点更多地表现为河流指向性.

Located in the hinterland of the Qinghai-Tibet Plateau,Tibet has very limited space suitable for human living.The spatial distribution of settlements in Tibet is restricted by multiple factors.To reveal the spatial distribution characteristics and explore the main influencing factors of settlements in Tibet,we extracted patch data from the high-resolution images of urban and rural settlements in Tibet based on visual interpretation.Methods such as the kernel density analysis,space hotspot detection,Geodetector and others were applied to analyze the spatial differentiation characteristics and influencing factors,with the aim to provide reference for future settlements selection and formulation of relevant policies on regional economic development in the plateau region.The results showed that urban and rural settlements in Tibet had a clustering pattern,with different overall density distribution.Lhasa was a high-density core,and Ngari Prefecture,Qamdo,and Nyingchi were the“core-edge”structures with low-density edges.The settlement density of Lhasa was as high as 220 ind·km-2,while that of Ngari Prefecture,Qamdo and Nyingchi was only 5.7 ind·km-2.The gap between the two regions was more than 43 times.The clustering of high and low value clusters in urban and rural settlements was remarkable.The number of high-value of large plaques was rare,and the number of low-values of small plaques was dominant.The area of high-value cluster accounted for only 3.7%,concentrated in Lhasa and Lhoka.The proportion of low value cluster area reached 67.2%,mainly distributed in Ngari Prefecture and Nagqu on the Qiangtang Plateau.There were six types of urban and rural settlements in Tibet,which formed two circle structures in the“One River and Two Streams”basin and the“Three Rivers”basin.From the inside to the outside,the large plaque-dominated type,medium-density and cluster-like type,high-density and pointscattered type,low-density and point-scattered type and high-altitude and uninhabited type was successively distributed.Lhasa was dominated by medium-density and cluster-like type,accounting for 31%.Lhoka was dominated by low-density and point-scattered type,accounting for 38%.Qamdo was mainly low-density and point-scattered type,accounting for 51%.The Ngari Prefecture,Nagqu and Shigatse were dominated by high-altitude and uninhabited type,and the proportion of the Ngari Prefecture was as high as 64%.The effects of different factors on the spatial distribution of urban and rural settlements in Tibet were distinctly different.The population and GDP were highly decisive for the distribution of urban and rural settlements.In addition,urban settlements showed strong road orientation,while rural settlements were more characterized by river orientation.