Declining growth resilience to drought of alpine juniper shrub along an east-west precipitation gradient in the central Himalayas

Understanding resilience of alpine ecosystem to climatic extremes such as droughts is a key to predict its functioning and vulnerability under changing climate. However, the growth resilience of alpine woody plants to warming-induced moisture stress in the Himalayas remains poorly understood. To address this knowledge gap, we used annual growth rings of alpine juniper shrubs from 17 sites across five mountain valleys, along an east-west gradient of decreasing precipitation in the central Himalayas. Through a comprehensive analysis of the climate-growth relationships, we identified distinct responses of shrub growth to drought events. We found that low moisture availability in spring is a critical constraint of juniper growth, being more pronounced in the drier western sites. A clear gradient in resilience was observed, with a higher resistance to drought and a lower recovery period in the wetter eastern sites. In addition, shrub growth resilience significantly decreased along the east-west (wet-to-dry) precipitation gradient. The analyses also revealed an association between aridity and resilience in response to drought. In conclusion, as drought events are expected to be more frequent with future warming, alpine juniper shrubs in drier sites of the central Himalayas likely face higher vulnerability. Such an aridification tendency may disrupt the functioning of alpine ecosystems and impair some of their services. This study emphasized the need for targeted conservation and management strategies to buffer the impacts of climate change on sensitive alpine shrubland ecosystems.