Spatial allocation of tree,shrub and herb plants in hilly area of the Loess Plateau:a case study of Dingxi,Gansu Province
黄土丘陵沟壑区乔灌草植物空间优化配置——以甘肃省定西地区为例

Soil and water loss in hilly area of the Loess Plateau is affected by many environmental factors, such as climate, vegetation, soil, terrain and so on. Severe soil and water loss is also blamed to irrational land-use pattern and infeasible spatial allocation of tree, shrub and herb plants. How to adjust land use structure and how to distribute tree, shrub and herb plants over space is imperative in the Loess Plateau. In present study, four key ecological factors affecting the growth and distribution of plants were chosen, including elevation, slope degree, slope aspect and precipitation, and then a decision table was established for spatial optimum allocation of plant species. The study area was divided into five main groups and eighteen sub-groups based on multi-criterion decision analysis (MCDA) and GIS. In addition, by using cluster analysis and area statistical analysis in GIS, the main and sub-groups were distributed to specific spatial cells, and the area of each group was calculated. This article presents the following viewpoints and conclusions: (1)In order to avoid blindfold artificial plantations and grain-for-green projects, adaptability of species and plant communities to the four ecological factors was analyzed through MCDA and experts knowledge. (2)Under the condition of sticking the principle that the economic benefits, social benefits and ecological benefits are synchronistically improved, economic plants and medicinal plants were allocated to adaptable cells according to their ecological requirements. (3)The decision table showed that land with a slope of more than 15° to be shifted to forest and grassland. Meanwhile, spatial cells for natural restoration were restricted to the area with slope more than 35°, accounting for 9% of the total study area. (4)The results indicated that economic forest/agro-forestry ecosystems and the farmland/courtyard-economy ecosystems should be the two major spatial allocation models, covering 76.02% of the whole area. And the other three models covered about 25% of the whole area. Spatial allocation of plant species is not only beneficial to eco-environmental improvement, but also useful to regional planning in agriculture.