Temporal and spatial changes of ecological strategies of native and alien plant assemblages in response to chronic...

Successional theory predicts directional shifts in plant community composition following disturbance. However, the long-term effects of chronic, recurring disturbances on plant ecological strategies at the community level in human-altered landscapes, and how they differ between the assemblages of native and alien species, remain poorly understood.

Using Grime's competitor, stress-tolerator, ruderal (CSR) framework, we examine temporal and spatial changes in plant strategies at the community level in the Three Gorges Reservoir Area, China. Based on repeated plant community surveys in 2012 and 2018 at the same localities, we assess the differences in the assemblages of native and alien strategies in response to chronic disturbances by extreme hydrological fluctuations and intense human activities over time and along a shoreline-to-upland disturbance gradient.

Our results reveal a temporal shift in native assemblages, with a decline in R-score and an increase in C- and S-scores, while alien assemblages maintained a strong R-strategy. Spatial patterns show that native assemblages adopted a mid-elevation peak in C-strategy, with S- and R-strategies dominating at higher and lower elevations, respectively. In contrast, there is no spatial variation in the CSR strategies of alien plant assemblages.

Our findings demonstrate that chronic disturbances (e.g. water fluctuations and human activities) drive a spatiotemporal decoupling of the CSR strategies between native and alien plant assemblages. This divergence requires targeted management by prioritizing suppression of ruderal alien species and promoting competitive and stress-tolerant native species to guide succession dynamics.