Simulation of suitable habitats for typical plants and quantification of water carrying capacity of vegetation in the wind-sand region of northern China

The aims of this study were to perform a quantitative analysis of the distribution patterns of suitable habitats for typical sand-fixing plants in the wind-sand region of northern China and the characteristics of vegetation carrying capacity under water resource constraints, to determine the reasonable threshold of planting density, and provide a scientific basis for precise desertification prevention and control. Haloxylon ammodendron and Pinus sylvestris var. mongolica were selected as the research objects. We integrated the MaxEnt model with the classical soil-water carrying capacity model for vegetation. By combining soil moisture data from 2008 to 2018 with climate, soil, and topography data, we analyzed the suitable habitats of the two plants and the dominant environmental factors affecting these habitat, and then calculated the maximum carrying capacity of vegetation based on regional water balance. The results showed that: (1) Suitable habitats for H. ammodendron, which occupy approximately 19% of the total study area, are concentrated in the desert grassland. The distribution of H. ammodendron is primarily governed by the precipitation in the coldest quarter and the mean annual temperature. Suitable habitats for P. sylvestris cover 48% of the total study area, with the eastern Horqin Sandy Land and typical steppe zone comprising the core area, and are limited by extreme precipitation in summer and winter, as well as soil rooting conditions. (2) The water-carrying capacity exhibits significant spatial variation: the carrying capacity of H. ammodendron is greater than 10.0×104 trees·km-2 in the desert grassland west of the Yin Mountains, but less than 7.0×104 trees·km-2 in areas such as the western Horqin Sandy Land and the piedmont plain south of the Da Hinggan Mountains. (3) A zoned planting scheme is proposed: the recommended plant spacing for H. ammodendron in the desert steppe zone is 1.5 m×2.0 m; a spacing of 6.5 m×9.5 m is appropriate for P. sylvestris in the typical steppe zone; however, in restricted areas such as the Horqin Sandy Land, the spacing for P. sylvestris should be reduced to 10.5 m×15.0 m, which shows small deviation from practical applications. This research provides quantitative data to support the ecological restoration in the wind-sand region of northern China in accordance with the principles of “determining greening based on water availability” and “matching species to site conditions”. Future research should focus on interspecific water competition mechanisms in mixed plantations.