Using plant physiology to determine drought resistance and resilience in rangeland bunchgrasses

Authors: O'Connor, Rory; Hamerlynck, Erik

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/22/2022
Publication Date: 2/22/2022
Citation: O'Connor, R.C., Hamerlynck, E.P. 2022. Using plant physiology to determine drought resistance and resilience in rangeland bunchgrasses [abstract]. Society for Range Management. Paper No. 813736.

Interpretive Summary: Many rangeland plants have adapted to dry conditions, but how these plants establish, reproduce, and produce viable seed is critical information that is needed to understand how to improve restoration success. We studied the physiological traits of several perennial bunchgrass species (Pseudoroegneria spicata and Elymus elmoides, native bunchgrass; Agropyron cristatum, non-native bunchgrass) to determine water stress thresholds for resiliency as seedlings and in mature plants for seedhead maturation. We found that E. elmoides is extremely resilient to water stress as a seedling unlike P. spicata, but is not as physiologically robust as A. cristatum in seedhead maturation. The need to understand the physiological responses of perennial bunchgrasses used in restoration will be key to help improve material selections for improved restoration success.

Technical Abstract: Rangeland plants are no strangers to dry conditions and have life history strategies that allow them to persist even while water stressed. However, their ability to establish, reproduce and produce viable seed varies immensely by functional group and species. Understanding the mechanisms behind rangeland plants’ survival can be accomplished through measuring physiological traits and then modelling the data to either predict or describe the pattern at larger scales. Here we present two studies in the Great Basin Sagebrush Steppe that address how water stress influences 1) seedling physiology of Elymus elmoides and Pseudoroegneria spicata, two native perennial bunchgrass species, and 2) the reproductive physiology of Elymus elmoides and Agropyron cristatum, one native and one non-native perennial bunchgrass species used in restoration. We found in the first study when water was withheld that both native bunchgrass species took three days to stop photosynthesizing and were extremely stressed based on chlorophyll fluorescence results. After withholding water for 7-days we re-watered all of the seedlings and E. elmoides recovered fully within 2-days, while P. spicata never fully recovered even after a week. In the second experiment, during a naturally occurring drought we found that water improved optimal photochemical yield (Fv/Fm) in both E. elmoides and A. cristatum flag leaves and seedheads. While watering did not improve the light response of either species, A. cristatum always maintained higher electron transport rates at saturating light levels than E. elmoides. These studies highlight the need for understanding the physiological ecology of our perennial bunchgrass species being used for restoration. Too often restoration efforts are unsuccessful because of abiotic stress and we should look for ways to help improve material selections for restoration through physiological metrics.