1976-2016年青藏高原地区通达性空间格局演变

青藏高原地区是地球上最独特的地理—生态—人口—交通单元,区域内交通网络的发展特征及规律是人地关系协同发展的一个重要切入点,对青藏高原地区交通网络开展研究具有重要意义。据此,分析1976-2016年青藏高原地区交通网络演化特征,并以省会、地级市、县级市和县城为节点,采用网络分析的时间距离计算模型探讨其通达性演变过程。研究表明：① 青藏高原地区交通网络复杂性、区域连通性增强,初步形成格状交通网络;② 青藏高原地区中心城市、县城之间的平均最短通达时间已极大缩短至11.89 h、18.84 h,呈自东向西逐渐增大的空间格局,时空收敛效应显著,通达性变化程度与其初始值有关;③ 中心城市为该地区的发展极,其与周围城市通达状况有极大提高,可达时间平均值下降到16.49 h;④ 中心城市和县城交通圈演变过程一致,青藏高原地区各地到最近城市、县城的通达时间不断缩小,沿重要交通干线已形成中心城市4 h、县城2 h短时交通圈连片分布格局,湟水河谷地、一江两河地区逐渐形成交通廊道,乡镇对外交通联系得到改善。

Evolution of accessibility spatial pattern of the Qinghai-Tibet Plateau in 1976-2016

The Qinghai-Tibet Plateau is a unique geography-ecology-population-traffic region on the earth. The characteristics and regularities of the transport network development are an important breakthrough for the coordinated development of man-land relationship, which is of great significance to the research in the Qinghai-Tibet Plateau. Accordingly, this paper analyzes the evolution of transport network in this region between 1976 and 2016, and explores its accessibility using a temporal distance calculation model based on network analysis by taking provincial capitals, prefecture-level cities and counties as transport nodes. Results suggest that, first, transport network is more complex and the regional connectivity is gradually enhanced in the plateau, preliminarily forming a grid-like transport network; second, the average minimum accessibility time between anchor cities and between counties has been vastly reduced to 11.89 hours and 18.84 hours, manifesting a gradually growing spatial pattern from east to west and remarkable effects of time-space convergence; third, anchor cities are the poles of regional development, with average accessibility time to around cities reduced to 16.49 hours, indicating that anchor cities tied with others have been improved; fourth, the traffic circles of anchor cities and counties are evolving consistently, accessibility time from various places in the study area to their nearest cities or counties are decreasing, presenting a contiguous pattern of short-time traffic circle with 4-hour access to central cities and 2-hour access to counties along important arterial roads, thus improving external transport connection of towns. And traffic corridors are gradually formed in the Huangshui River Valley, and the Middle Region of "One River and Two Streams" in Tibet.