The effect of competition on seedling stomatal response to drought
Abstract
Understanding plant hydraulic strategies holds strong promise for predicting forest responses to drought and improving dynamic vegetation models. It has generally been assumed that plants regulate their stomata to maintain a constant marginal water use efficiency, thereby foregoing carbon gains when water is relatively scarce. However, recent studies have suggested that stomatal conductance is regulated to maximize carbon assimilation while also accounting for the risk of hydraulic damage via cavitation and hydraulic failure. This "cost-gain" carbon maximization hypothesis predicts more risky stomatal regulation because unused water can be used by neighboring plants and carbon gains, not water use efficiency, are the priority when competing with neighbors. Distinguishing between these two hypotheses is critical for predicting how plants will change their stomatal behavior in different biotic and abiotic conditions. This study utilized a mechanistic model of stomatal behavior to investigate whether competition causes seedlings to adjust their stomatal strategy with respect to hydraulic risk as predicted by the carbon maximization hypothesis. Three species, quaking aspen (Populus tremuloides), narrowleaf cottonwood (Populus angustifolia), and ponderosa pine (Pinus ponderosa), were grown in solo or competition pots and subjected to three drought treatments in a controlled growth chamber environment. Empirical data were best explained by the carbon-maximization hypothesis, which more closely predicted measured stomatal conductance than the constant water use efficiency hypothesis. In addition, seedlings grown in heterospecifc versus conspecific competition mediated stomatal response to drought indicating a shift in pricing of carbon gain versus risk of hydraulic damage. This experiment provides evidence for the effects of competition on stomatal strategy and highlights the importance of competition on individual and ecosystem responses to drought.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B33F2529Z
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 0466 Modeling;
- BIOGEOSCIENCES;
- 0476 Plant ecology;
- BIOGEOSCIENCES