Plant communities interact with the environment to reveal adaptation mechanisms in sandy coastal shelterbelts

Coastal shelterbelts perform significant ecological functions but are harsh and fragile habitats where plant diversity is seriously constrained by environmental stressors. However, the complex interactions among soil environmental conditions, plant communities, and ecosystem stability, as well as the underlying mechanisms, remain poorly understood, limiting the development of effective conservation strategies. To address this, we surveyed 30 representative sandy coastal shelterbelts of Guangdong Province in southern China, identifying 118 vascular plant species, dominated by Casuarina equisetifolia , Bidens pilosa , and Brucea javanica . Based on soil properties, the sites were classified into three distinct environmental groups (G1, G2, and G3). Specifically, G3 exhibited higher salinity and nutrient content than G1 and G2, while G1 showed the highest bulk density and G2 had the highest pH. Habitats with higher nutrient and salinity levels (G3) demonstrated greater species richness (18.67 vs 10.77, 9.36), functional richness (0.046 vs 0.026, 0.020), and community stability (0.30 vs 0.23, 0.21) than G1 and G2. In contrast, nutrient-poor habitats (G1 and G2) exhibited a higher leaf length-to-width ratio (9.91 and 14.27) than G3 (5.07) and favored stress-adaptive traits such as hairless, linear-shaped leaves. Further analysis revealed that soil environmental factors positively influenced functional traits and species diversity, which positively influenced functional diversity and community stability. This study provides new insights into the resource buffering and compensation, stress-adaptive leaf trait selection, and diversity-mediated stability mechanisms in coastal ecosystems. These findings further inform targeted restoration strategies for sandy coastal shelterbelts in Guangdong and offer a valuable framework for their management.