Interactive effects of elevated temperature and drought on plant carbon metabolism: A meta‐analysis

Elevated temperature (Te) and drought often co-occur and interactively
affect plant carbon (C) metabolism and thus the ecosystem C cycling, but
the magnitude of their interaction is unclear, making the projection of
global change impacts challenging. Here, we compiled 107 journal articles
in which temperature and water availability were jointly manipulated and
performed a meta-analysis of interactive effects of Te and drought on leaf
photosynthesis (Agrowth) and respiration (Rgrowth) at growth temperature,
nonstructural carbohydrates and biomass of plants, and their dependencies
on experimental and biological moderators (e.g., treatment intensity,
plant functional type). Our results showed that, overall, there was no
significant interaction of Te and drought on Agrowth. Te accelerated
Rgrowth under well-watered conditions rather than under drought
conditions. The Te × drought interaction on leaf soluble sugar and starch
concentrations were neutral and negative, respectively. The effect of Te
and drought on plant biomass displayed a negative interaction, with Te
deteriorating the drought impacts. Drought induced an increase in
root-to-shoot ratio at ambient temperature but not at Te. The magnitudes
of Te and drought negatively modulated the Te drought interactions on
Agrowth. Root biomass of woody plants was more vulnerable to drought than
that of herbaceous plants at ambient temperature, but this difference
diminished at Te. Perennial herbs exhibited a stronger amplifying effect
of Te on plant biomass in response to drought than did annual herbs. Te
exacerbated the responses of Agrowth and stomatal conductance to drought
for evergreen broadleaf trees rather than for deciduous broadleaf and
evergreen coniferous trees. A negative Te × drought interaction on plant
biomass was observed on the species level rather than on the community
level. Collectively, our findings provide a mechanistic understanding of
the interactive effects of Te and drought on plant C metabolism, which
would improve the prediction of climate change impacts.