Stomatal behavior moderates water cost of CO 2 acquisition for 21 boreal
and temperate species under experimental climate change
Abstract
The linkage of stomatal behavior with photosynthetic processes is
critical to understanding water and carbon cycles under global change.
The slope ( g1) of stomatal conductance (
gs) versus CO 2 assimilation (
Anet) serves as a proxy of the marginal water
cost of carbon acquisition and the trade-off between carbon gain and
water loss. Here we use g1 to assess species
differences in the response of stomatal behavior to experimental climate
change manipulations, asking whether generalizable patterns exist across
species and climate contexts. A total of 17,727
Anet- gs measurements made
in a long-term open-air experiment under ambient and +3.3°C warming, and
ambient and ~40% summer rainfall reduction provided
> 2,700 estimates of g1 across 21
boreal and temperate tree species. All species became more conservative
in their water use (lower g1) in warming and/or
reduced rainfall treatments because of lower soil moisture. In contrast
to these phenotypic responses, species from warmer and drier habitats
tended to have slightly higher g1 and to be the
least sensitive to the decrease in soil water. Overall, both warming and
rainfall reduction consistently made stomatal behavior more conservative
in terms of water loss per unit carbon gain across 21 species and a
decade of experimental observation.