Evaluation of cultivated land consolidation suitability in Northeast China black soil zone using niche-fitness model: A case study of Gongzhuling City

Cultivated land consolidation is a good protection measure of land resources, while land suitability evaluation forms the prerequisite and basis for cultivated land consolidation. Niche theory is generally used in ecological studies. Niche-fitness can be used to characterize the suitability of species to habitat conditions, which is increasingly applied on landscape studies. Similarly, it can be used to characterize the suitability of cultivated land consolidation index. With Gongzhuling City as the case study, this paper used niche theory and 14 indicators of four index layers (natural condition, infrastructure condition, ecological sustainability and spatial stability) to establish the suitability evaluation index system of cultivated land consolidation, . The Delphi method was then used in combination with Analytic Hierarchy Process (AHP) to determine the index weight. While the actual ecological niche of cultivated land consolidation was defined as the real index value, optimal ecological niche was defined as the ideal index value. Thus the evaluation models for the three index types (positive index, negative index and moderate index) were determined on the basis of the match degree between actual and optimal ecological niche. Based on this approach, the weighted sum of matching degree was calculated as the niche-fitness value of each evaluation unit. Finally, using the Ward method, the suitability of cultivated land consolidation were divided into 4 grades to evaluate cultivated land consolidation regions. Meanwhile, the optimal niche was proposed as a standard of cultivated land consolidation to establish the diagnosis model of obstacle indicators, clarifying the priority and orientation on cultivated land consolidation in different regions, searching countermeasures and valid paths. The results showed that the natural condition of cultivated land in Gongzhuling City was good and that cultivated land consolidation could be prioritized in the Southwest and North. About 13 799.89 hm² of land was highly suitable for cultivated land consolidation, which accounted for 4.16% of the total cultivated land. This area was restricted by farmland shelter belt ratio, road accessibility and the degree of field regularity. About 77 754.36 hm² of land was moderately suitable for cultivated land consolidation, accounting for 23.41% of the total cultivated land. The land was restricted by irrigation condition, road accessibility and farmland shelter belt ratio. About 177 192.38 hm² of land was mildly suitable for cultivated land consolidation, accounting for 53.36% of the total cultivated land. The land was restricted by soil organic matter content, distance from main traffic line and soil pH. The area unsuitable for cultivated land consolidation was 63 325.61 hm², accounting for 19.07% of the total cultivated land area. And the restrictive factors were soil texture, irrigation condition and topsoil thickness. It was suggested that the relevant departments should carry out corresponding measures of cultivated land consolidation in different regions and orderly implement the measures in the future. In conclusion, the application of the niche-fitness model in the evaluation of cultivated land consolidation suitability extended the application range of the theory of ecological niche. This provided the scientific basis for site selection and consolidation direction of cultivated land consolidation projects.