BayCEER Workshop 2016

Mechanisms of drought tolerance in temperate grassland species

P 3.6 in Water and the environment: From biosphere to geosphere

Introduction

While the importance of drought in grasslands worldwide is well-established, our understanding of the mechanisms underlying differential species responses to drought, and how that shapes community composition and resilience remains surprisingly limited. To date, few studies have rigorously linked mechanistically promising traits to drought responses or habitat associations of grassland species, and available knowledge comes from woody species.

Methods

We comparatively quantify 12 physiological and morphological traits known or hypothesized to be important in plant water relations in 41 grassland species. We test their relative importance for plant differential drought tolerance through directly linking them to comparative whole-plant drought tolerance quantified in a field experiment (see poster Jung et al. ).

Results

Survival under drought conditions in a common garden experiment increased with increasing turgor loss point, maximum photosynthesis capacity and minor vein density, and decreasing major vein density and diameter for all species, and decreasing minimum leaf conductance but only for forbs. Meanwhile, survival increased with increasing midday leaf water potential under drought, indicating that plants with higher survival were better able to avoid desiccation.

Conclusions

Our results support the idea that a desiccation avoidance rather than a desiccation tolerance strategy is important for species to deal with drought. We are currently assessing a suite of additional traits, such as critical leaf water potential at stomatal closure, rooting depth, biomass allocation, xylem diameter and stomatal density to further evaluate the importance of traits for drought tolerance of grassland species. Our results further indicate that the drought tolerance of temperate grassland species can be successfully predicted from their traits, and that herbaceous grassland species and woody species have fundamentally different strategies to cope with drought.

Keywords: drought tolerance, functional traits