Phenological impacts on the dynamics of non-invasive and invasive species communities in mountainous ecosystems

Alien plants are increasingly expanding from low to high elevations, threatening native communities in mountainous ecosystems. Understanding the mechanisms driving these invasions and their ecological impacts is essential for effective management and biodiversity conservation. Plant phenology, a sensitive indicator of environmental change, plays a pivotal role in facilitating plant colonization along environmental gradients. Although phenological niche differentiation between non-invasive and invasive plants has been observed, its impacts on invasion success and native community diversity remain underexplored. In this study, we conducted nine surveys from March to September across 35 plots along an altitudinal gradient in the Tianmu Mountain National Nature Reserve, Zhejiang Province. We recorded species composition, cover, and 10 functional traits to investigate temporal dynamics in community dissimilarity, ecological strategies, diversity and stability. Temporal patterns of non-invasive and invasive groups were compared across high and low elevations to infer the underlying community assembly processes. Our results revealed significant temporal shifts in community components, with diversity following an inverted U-shaped trajectory: non-invasive groups peaked in September, while invasive groups peaked in May. Both non-invasive and invasive groups showed decreasing species turnover over time, with higher community-weighted ruderal scores compared to competitive and stress-tolerant scores at both high and low elevations. Environmental variation between high and low elevations mediated relationships among community components, particularly diversity and stability. Distinct differences in community structure between non-invasive and invasive groups suggest divergent assembly mechanisms. Notably, invasive groups exhibited increasingly clustered phylogenetic patterns over time, decoupled from more divergent functional trait patterns. By integrating multidimensional community variables, this study provides a comprehensive view of annual dynamics and structural differences between non-invasive and invasive groups. It highlights the critical role of environmental change and phenological niche differentiation in shaping community dynamics, offering valuable insights into predicting community reorganization under future scenarios of climate change and alien plant invasion.