基于人居环境特征的青藏高原“无人区”空间界定

Spatial definition of"Unpopulated Areas(UPAs)"based on the characteristics of human settlements in the Qinghai-Tibet Plateau,China

青藏高原独特的高寒环境与自然条件在一定程度上限制了人口的自然分布与有序发展,形成了中国面积大、分布广的"无人区"(UPAs)。然而,当前有关"无人区"面积、分布、特征与区域差异等研究尚无定论。客观、准确界定"无人区"的空间范围,对开展青藏高原资源环境承载力评价、国家公园与生态安全屏障建设等具有重要意义。基于青藏高原居民点分布信息,据其地形、气候、生态、土地利用等要素特征,本文综合表征了居民点的自然—生态—土地利用耦合关系,率定了居民点分布上限的各要素阈值,通过多要素空间叠加构建了"无人区"评价综合模型,并以居民点分布的自然极限、生态(含氧量)下限、土地利用规律为关键阈值界定了青藏高原"无人区"空间范围并分析了其地理分布特征。研究表明:(1)以居民点分布累计比例<0.1%计,确定"无人区"的地形阈值为海拔>5665 m、相对高差>2402 m、地形起伏度>8.59,气候阈值为相对湿度<76.2%、温湿指数<33或>71。(2)根据居民点分布及人体对含氧量耐受情况,确定"无人区"的生态阈值为气压<500 hpa、大气含氧量<40%。(3)青藏高原严格"无人区"面积达1912 km2,其中新疆699 km2、四川413 km2、西藏331 km2、青海291 km2、甘肃178 km2。空间上呈零星分散状,多分布在四川贡嘎山、珠穆朗玛峰附近等极高山地区、可可西里东部—罗布泊地区;以及少部分分布在青海柴达木盆地。

The Qinghai-Tibet Plateau(QTP)has unique features of high-cold environments and natural conditions,which have limited the natural distribution and orderly development of its population,and then has formed a large and widely distributed Unpopulated Areas(UPAs).However,the information of the area size,distribution extent,geographical characteristics and regional differences of the UPAs in this plateau is still not available.Therefore,it is significant to define accurately the spatial extent and geographical distribution of the UPAs for the assessment of resources and environmental carrying capacity and constructing the national parks and ecological security barrier in this plateau.Based on the distribution information of residential areas in the QTP,from the characteristics of topography,climate,ecology(oxygen content),land use and other elements,the study aims to examine the relationship of naturalecological-land use system.Therefore,we developed a comprehensive evaluation model of the"UPAs"through the spatial overlay of multiple elements.The key thresholds determined in the aspects of physical and ecological(oxygen content)limits and land use characteristics,were then used to define the geographical distribution and to examine spatial characteristics of the UPAs in the QTP,China.The results showed that:(1)With the cumulative proportion of residential distribution<0.1%,we defined the topographic thresholds of the UPAs including the elevation>5665 m,relative height difference>2402 m,the relief degree of land surface(RDLS)>8.59,and the climatic thresholds including the relative humidity>76.2%and the temperature humidity index(THI)<33 or>71.(2)According to the distribution of residential areas and oxygen content tolerance of the human being,the oxygen content thresholds of UPAs were determined as air pressure<500 hPa,oxygen content<40%.(3)The resultant UPAs on the QTP covers an area of 1912 km2,including 699 km2 in Xinjiang,413 km2 in Sichuan,331 km2 in Tibet,291 km2 in Qinghai,and 178 km2 in Gansu.The UPAs are scattered sporadically,mostly distributed in Gonggashan Mountain region in Sichuan,the extremely high mountain areas such as Mount Everest in the Himalayas,and the northern Hoh Xil and Lop Nur region,as well as a small part of the UPAs in the Qaidam Basin of Qinghai.