PS 49-160 - Leaf and root functional traits of C₃ perennial grasses respond to simultaneous atmospheric and soil drought conditions

Background/Question/Methods

Climate change is altering global mean surface temperatures and precipitation regimes. When this results in drought, drought-sensitive species are sometimes lost and biodiversity is reduced. This combination of global change drivers may be particularly deleterious as biodiversity could help buffer ecosystems against the negative effects of drought. Soil drought can alter root and leaf functional traits as the plants attempt to maintain water status and avoid dehydration. However, past drought studies that only manipulate precipitation inputs into soil (via rainout shelters) may be underestimating the effects of atmospheric drought conditions on plant responses. We examined whether soil and atmospheric drought result in changes to P. secunda functional traits at two levels of plant species richness. We evaluated functional traits of Poa secunda grass grown in a first-of-its-kind atmospheric drought and soil drought manipulation and measured P. secunda functional traits in various drought conditions. We focused on specific leaf area (SLA), leaf area, stomatal density, root:shoot ratio, and fine root:coarse root ratios.

Results/Conclusions

We found that leaf area and overall growth were higher with increased soil water and higher atmospheric moisture in most cases. However, we found that P. secunda grown in atmospheric drought combined with soil drought significantly increased root:shoot ratio when compared with all other experimental manipulations. Plant energy allocation strategy also differed when P. secunda was grown in a combination of soil and atmospheric drought conditions. These results suggest that plant energy allocation strategies may differ depending on the type of drought manipulation applied. Our results indicate that rainout shelters, and other methods that focus purely on soil water inputs, may be imprecisely predicting drought effects in plant communities.