Intraspecific variation in functional traits may mediate tree species’ drought resistance, yet it remains unknown if trait variation is due to genotype (G), environment (E), or GxE interactions. Understanding the drivers of intraspecific trait variation and whether variation mediates drought response can improve predictions of species’ response to future drought.

Using populations of quaking aspen spanning a climate gradient, we investigated intraspecific variation in functional traits in the field as well as the influence of G and E among propagules in a common garden. We also tested for trait-mediated trade-offs in growth and drought stress tolerance.

We observed intraspecific trait variation among the populations, yet this variation did not necessarily translate to higher drought stress tolerance in hotter/drier populations. Additionally, plasticity in the common garden was low, especially in propagules derived from the hottest/driest population. We found no growth-drought stress tolerance trade-offs and few traits exhibited significant relationships with mortality in the natural populations, suggesting that intraspecific trait variation among the traits measured did not strongly mediate responses to drought stress.

Our results highlight the limits of trait-mediated responses to drought stress and the complex GxE interactions that may underly drought stress tolerance variation in forests in dry environments.

Data were collected during the summers of 2019, 2020, and 2021. Tree cores were mounted and prepped using standard dendrochronology methods. Many of the functional traits were measured on samples processed in a laboratory.