Hydraulic traits govern opposing range shifts of montane trees under warming

Abstract

Montane tree species are undergoing accelerated elevational range shifts in response to climate warming, yet the mechanisms driving interspecific variation remain elusive. Here we show that hydraulic traits predict opposing biogeographic responses of montane trees to warming and drought. By integrating hemispheric-scale dendrochronological records from 45 species (121,743 individuals), global observations of elevational range shifts from 102 species and hydraulic trait data for 11 functional attributes, we demonstrate that climate-sensitive species tended to rapidly track warming into higher elevations, whereas taxa resistant to these stresses were poised to have expanded downslope. In addition, elevational dependencies in drought sensitivity changed over time for nearly one-third of the species, revealing dynamic reorganization of climate–growth relationships across mountain gradients. These findings establish leaf- and stem-level hydraulic traits as a fundamental predictor of range dynamics, providing a mechanistic basis for forecasting the reorganization of montane forests under continued climate change. The authors integrate dendrochronological records with range shifts to show that shifts in montane tree species are tightly linked to tree hydraulic properties. While climate-sensitive species track warming to higher elevations, stress-resistant species expand downslope.