Understanding the traits mediating species' responses to climate change
is a cornerstone for predicting future community composition and
ecosystem function. Although species' eco-physiological properties
determine their response to environmental change, most trait-based
studies focus on a small subset of easily-measured morphological traits
as proxies for physiology. This choice may limit our ability to predict
the impacts of climate change on species' demography, and obscure the
underlying mechanisms. We conducted a transplantation experiment along a
1000 m Alpine elevation gradient to quantify the degree to which plant
demographic responses to climate were predicted by eco-physiological
performance versus common morphological traits. Although physiological
measurements revealed that warming favored species with a conservative
water use strategy, the predictive power of physiological traits did not
exceed that of morphological traits. Our results show that while
easily-measured morphological traits can successfully predict
demographic responses to climate, eco-physiological approaches are
needed to understand mechanism.