Conclusions
Our work documents the water-carbon trade-off response to long-term
experimental manipulation for tree species common to the
boreal-temperate ecotone in North America. Empirically quantifying those
responses across a large number of species in a relatively realistic
experimental context contributes to our understanding of whether and how
stomatal behavior is expected to vary across species and their
hierarchical affiliations (e.g., climate of origin or phylogeny) in
response to climate change. In particular, we found thatg1 was reduced in response to growth conditions
that caused a decline of soil VWC (i.e., rainfall removal and warming).
We also showed that there was a large variation among species intrinsicg1 ; however, their responses to reduced rainfall
and warming did not depend on species identity or grouping. Our study
also provides additional evidence that soil moisture will govern plants’
response to future climate change: when soil moisture is abundant plants
use it to facilitate greater carbon assimilation, but when soil water is
limited plants will have diminished carbon assimilation but more
efficient water use.