Extending the osmometer method for assessing drought tolerance in herbaceous species
Community-scale surveys of plant drought tolerance are essential for understanding semi-arid ecosystems and community responses to climate change. Thus, there is a need for an accurate and rapid methodology for assessing drought tolerance strategies across plant functional types. The osmometer method for predicting leaf osmotic potential at full turgor (πo), a key metric of leaf-level drought tolerance, has resulted in a 50-fold increase in the measurement speed of this trait; however, the applicability of this method has only been tested in woody species and crops. Here, we assess the osmometer method for use in herbaceous grassland species and test whether πo is an appropriate plant trait for understanding drought strategies of herbaceous species as well as species distributions along climate gradients. Our model for predicting leaf turgor loss point (πTLP) from πo (πTLP = 0.80πo–0.845) is nearly identical to the model previously presented for woody species. Additionally, πo was highly correlated with πTLP for graminoid species (πtlp = 0.944πo–0.611; r2 = 0.96), a plant functional group previously flagged for having the potential to cause erroneous measurements when using an osmometer. We report that πo, measured with an osmometer, is well correlated with other traits linked to drought tolerance (namely, leaf dry matter content and leaf vulnerability to hydraulic failure) as well as climate extremes linked to water availability. The validation of the osmometer method in an herb-dominated ecosystem paves the way for rapid community-scale surveys of drought tolerance across plant functional groups, which could improve trait-based predictions of ecosystem responses to climate change.
KeywordsOsmotic potential Climate change Grasslands Plant traits Drought
We would like to thank Victoria Klimkowski, Daniel Spitzer, Dan LeCain, Julie Bushey, and Mary Carlson for helping with data collection and three anonymous reviewers for providing comments that greatly improved this manuscript. This work was funded by the NSF Emerging Frontiers Macrosystem Biology Program (EF-1137378, EF-1137363, EF-1137342 and EF-1137293).
Author contribution statement
All authors contributed substantially to data collection and the conception of the experiment. RJGN and TWO conducted the analyses and wrote the initial draft of this manuscript; other authors provided editorial advice.
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