Climate Warming Drives Himalayan Alpine Plant Growth And Recruitment Dynamics

Understanding how climate influences plant reproduction and growth at contrasting range limits is crucial for predicting how species' ranges may shift in response to ongoing climate change. Trees and shrubs have shown warming-induced increases in performance at upper elevation limits but reduced performance at lower distributional limits due to warming-driven drought limitation. Whether these differential responses are also valid for alpine forbs exposed to accelerated warming remains largely unknown. We examined climate signal recorded in annual growth and recruitment over the past 60 years in the alpine forbPotentilla pamiricain Western Himalayas, and tested whether the responses to recent climate warming differ between dry steppe, wet alpine and cold subnival zone within the species 5,250-5,900 m elevation range. We reconstructed recruitment and growth chronologies from 1,019 individuals spanning 1-73 years, and more than 21,500 annual growth rings. We identified contrasting climatic controls of recruitment and growth at opposite elevation range margins, as well as contrasting demographic trends identified from age distributions. In lower-elevation steppes, recruitment increased with high late-winter snowfall and decreased with high summer temperatures, while growth increased with high summer precipitation. Conversely, warm winters and summers in higher-elevation alpine and subnival zones support growth and recruitment, while snowy winters reduce them, especially at their upper elevation limit. The age distribution revealed greater numbers of younger individuals, indicating healthy growing populations, in the alpine habitat, while evidence of ageing plant populations was observed in steppe and subnival zones. Accelerated warming since the 1990s reduced growth and recruitment in dry steppes while supporting plant performance in the alpine habitat. The recruitment in the subnival zone did not peak during the past warmest decade due to concomitant extreme snowfall events. Synthesis. Our results provide novel information on population-specific climate dependency of plant recruitment, growth and population dynamics, suggesting the high vulnerability of high-elevation Himalayan ecosystems to climate change. This is partly balanced by high species longevity and slow radial growth securing a long-term population persistence. Continuing trends of extreme snowfall events at higher elevations and droughts at lower elevations may lead to species range contraction.