Early growing-season precipitation drives radial growth of alpine juniper shrubs in the central Himalayas

Shrubs growing at higher latitudes and altitudes are considered to be highly sensitive to climate warming. In particular, alpine shrubs are potential climate proxies for understanding responses of high-elevation treeless ecosystems to warmer conditions. However, little is known about how alpine shrub radial growth responds to climate variables, specifically temperature and precipitation. This lack of knowledge is particularly notable in the Himalayas where shrubs reach some of their worldwide uppermost limits. Herein, we investigated the climatic response of alpine juniper shrub (Juniperus indica) to climate in two areas (dry Manang valley; wet Everest valley) situated in the central Himalayas. In spite of different sites and elevations, the radial growth of juniper shrub is positively correlated with spring precipitation in both areas, and also with summer precipitation in the dry area. Juniper shrub shares common climatic responses with Himalayan treeline tree populations, whose growth dynamics are also controlled by moisture availability. Thus, radial growth of juniper in the central Himalayas may experience drought stress if climate warming leads to drier conditions. We conclude that alpine shrubs are crucial indicators of the responses of alpine ecosystem to global climate warming.