Asynchronous shifts in plant ecological strategies across forest layers during succession on Hengduan mountains

Grime's CSR (C-strategists efficiently acquire resources in productive environments, S-strategists thrive under stressful, low-resource conditions, and R-strategists rapidly exploit disturbance opportunities) theory outlines how plant community ecological strategies evolve during secondary succession. However, its applicability to disturbed forests has not been empirically validated in a comprehensive manner, especially when considering species data in different vegetation layers. By conducting field surveys across five successional stages ranging from grassland to primary forest, we measured the functional traits of 284 plant species, examined shifts in plant ecological strategies at the community level and factors influence these changes during the natural regeneration of subalpine forests in Hengduan Mountains, eastern Tibetan Plateau. Results showed that subalpine forests transition from an R-strategy to an S-strategy throughout succession, though the trajectory of this transition differs across the canopy, shrub, and herbaceous layers. Biotic vegetation factors—including plant diversity, density, vegetation coverage, and community height—alongside abiotic factors like total soil nitrogen, and pH are key influence factors of community ecological strategies evolution, with biotic vegetation factors playing a more dominant role. These findings indicate that restoration management in secondary forests should focus on regulating plant density, optimizing community spatial structure, conserving biodiversity, and maintaining sufficient soil nutrient levels, particularly nitrogen. Overall, our study reinforces the relevance of CSR theory in forest succession and offers a scientific basis for forest restoration in subalpine regions.