青藏高原高寒牧区聚落用地适宜性评价及其重构——以藏北那曲县为例

本文建立了适用于高寒牧区的聚落布局适宜性评价体系,利用自组织神经网络（SOFM）对青藏高原藏北地区那曲县展开聚落布局适宜性评价,并评估其现状聚落布局的合理性,在此基础上提出其聚落未来重构的思路。结果表明:（1）那曲县对于聚落布局的适宜性整体较低,适宜性水平高于一般适宜的区域零散分布在海拔较低、地势低缓的河谷地区,仅占全县面积的12%。其他适宜性较低的区域占全县面积的88%,分布相对集中。不同乡镇对于聚落布局的适宜性差异显著。（2）那曲县现有的聚落空间占全县总面积的0.47%,为7594 hm²,其中分布在一般适宜及以上等级区的面积占聚落总面积的86.47%,而较不适宜、不适宜和禁建区内的聚落占比高达13.53%。那曲县聚落空间布局倾向于较高级别的适宜区,聚落用地适宜性条件较好的乡镇其布局合理性越高。那曲县局部聚落布局不合理的原因包括:缺失空间布局指引、村级行政区划欠佳、藏民对神山的宗教信仰和历史遗存的地域环境认同。（3）聚落的空间重构可推动生态移民、适度“村庄化”等要素的整合来实现。聚落的经济重构要建设由特色产业为基础的村镇系统、充分利用“点—轴”结构的辐射效应等结构要素的重组来实现。聚落的社会重构需要通过合理安排基础设施、增强藏族社会关系组织程度、提倡藏区优秀文化传承等优化功能的措施来实现。

Land suitability evaluation and reconstruction of settlements in the pastoral area of Tibetan Plateau: A case study of Nagqu county in Northern Tibet

Taking Nagqu county in the alpine pasture of Tibetan Plateau as a case study, this paper built a land suitability evaluation index system of settlements, assessed the suitability of the land for the layout of settlements and its suitability grade in the study area using self-organizing mapping neural network (SOFM), evaluated the land suitability of current settlements, and further explored the paths of settlement reconstruction. The results showed that: (1) Nagqu county had a low level of land suitability for the layout of settlements. Suitable and sub-suitable areas, scattered in valleys with low elevations and flat terrain, only accounted for 12% of the total land area. Other areas of poorer suitability were relatively concentrated, accounting for 88% of the total land area. There were obvious differences among various townships and towns in the land suitability of settlements. (2) The current settlements of Nagqu county covered an area of 75.94 km², accounting for only 0.47% of the total land area. Areas where the suitability level was generally suitable and above accounted for 86.47%. About 13.53% of settlement area was distributed in hardly suitable, unsuitable, or prohibited construction areas. The layout of settlements in various townships and towns tended towards high-grade suitability areas. The better the environmental conditions, the more reasonable the layout of settlements; and vice versa. Lack of planning guidelines, irrational setting of administrative villages, local identification with specific survival spaces, and worshipping of mountains by Tibetans all contributed to the unreasonable layout of settlements in Nagqu county. (3) Ecomigration, "village-oriented" development in suitable areas, and other promotion factors can be integrated to realize the spatial reconstruction of settlements. Through constructing the central villages and towns system supported by characteristic industries and giving full play to the element diffusion role of the "point-axis" system, restructuring can be promoted to achieve the economic restructuring of settlements. By means of improving the allocation of public service facilities, enhancing the degree of social organization, strengthening the inheritance of Tibetan culture, and promoting the optimization of other functions, the social restructuring of settlements will be accomplished.