Suitability evaluation of unused land as construction land in Huailai based on landscape connectivity theory

It is important to exploit unused land as construction lands under the shortage of construction land space. At the same time, unused land is critical for protecting the ecological environment landscape and easing land supply. To realize rational exploitation of unused land resources, the relationship between exploitation and protection must be properly handled and reduce adverse impacts on landscape ecology during the exploitation and construction of unused lands. Taking Huailai County, a basin in the northwest of Hebei Province as a case study, this research introduced the minimum cumulative resistance (MCR) model, selected 4 groups of indexes (engineering geology, topography, location factors and natural ecosystem) to build resistance surface to evaluate the suitability of unused lands for exploitation and construction. The evaluation result was optimized by established potential rainwater ecological corridors and ecological nodes. The results showed that: 1) the evaluation of suitability for construction of unused lands based on the MCR model emphasized functions of the existing town construction land. The evaluation results showed centralized distribution characters which was beneficial for later exploitation and utilization. 2) According to the evaluation results, the research area was divided into suitable expansion zone, hypo-suitable expansion zone, restrictive expansion zone and prohibitive expansion zone. The respective areas of the zones were 17 064.67 hm², 20 468.30 hm², 9 723.66 hm² and 7 993.82 hm², showing that unused lands in Huailai County had the larger potential for development into construction land. The suitable expansion zone and hypo-suitable expansion zone were distributed mainly in the surroundings of county town and the peripheral of Guanting Reservoir. The regions above had more stable ecological conditions, lower development costs and more convenient traffic conditions, therefore had high potential for future exploitation. The restrictive expansion zone was mainly distributed in the peripheral of the hypo-suitable expansion zone and its engineering geological environment was relatively poor with slopes and the undulating terrain. The ecological environment was also more fragile and rarely influenced by human interference. The prohibitive expansion zone was mainly distributed in the northern and southern mountain regions with poor engineering geological conditions. Its ecological environment was so fragile that it was difficult to recover after destruction, thus the region was not suitable for development into construction lands. 3) In the study, the rainwater ecological corridors and ecological nodes were set as prohibitive expansion zone, and combined with the evaluation results to optimize the regionalization of unused land exploitation suitability. This was beneficial for alleviation of environment stress due to exploitation of unused land. This study further enriched the connotation of suitability evaluation of unused land construction in hilly and mountainous areas, and provided technical support for scientific and reasonable use of regional unused land resources.