Effects of ecological factors on the spatial distribution of food plants in the habitat of Hainan gibbons (Nomascus hainanus): Insights for conservation and habitat restoration

Understanding the availability of food resources is essential for effectively conserving endangered species. This study quantified the distribution of food plants within the Hainan gibbon habitat and assessed the environmental drivers of these distributions to guide targeted habitat restoration efforts. A total of 122 habitat plots were surveyed across five gibbon groups to collect the environment and food plant diversity data. Groups A to D occupied tropical montane rainforests (800–1200 m), while group E inhabited secondary lowland rainforests (500–700 m). Results revealed: 1) Climate and soil factors differed significantly between high- and low-altitude habitats. 2) Food plant species richness was higher in high-altitude habitats, while dry-season foods and preferred foods were more abundant in A and C groups. 3) Elevation, soil C/N ratio, soil alkaline dissolved nitrogen, and soil fast-acting phosphorus significantly affected food plant distribution. Soil content and climate are key drivers, with varying effects across different altitudes and food plant types. These findings indicate that successional low-altitude secondary forests are potential habitats for Hainan gibbons (e.g., group E) but require further restoration in lower quality areas. Our study highlights the need for habitat-specific restoration: in low-altitude forests, improving soil conditions (i.e., introducing native nitrogen-fixing species such as Albizia spp. to reduce C/N ratios and enhance alkaline dissolved nitrogen) can promote key food plant growth. In high-altitude forests, introducing climate-resilient species (e.g., Ficus spp.) can offset temperature and precipitation limitations. Such targeted actions are critical to ensuring food stability and supporting Hainan gibbon conservation.