Submitted to: Plant Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 8, 2009
Publication Date: September 11, 2010
Citation: Mukherjee, J.R., Jones, T.A., Adler, P.B., Monaco, T.A. 2010. Drought tolerance in two perennial bunchgrasses used for restoration in the Intermountain West, USA. Plant Ecology. Interpretive Summary: Drought has constrained native plant establishment in the rangelands of Intermountain West, thus it is important to have plant material selected for functional traits for drought tolerance to enhance restoration success. We compared four genotypes of native bluebunch wheatgrass (Pseudoroegneria spicata cv. Goldar, Anatone germplasm, and P-22 and P-26 experimental populations) and two genotypes of Snake River wheatgrass (Elymus wawawaiensis cv. Secar and E-46 experimental population) for potential drought response in a greenhouse experiment. Snake River wheatgrass grew faster than bluebunch wheatgrass and also produced greater shoot biomass under drought. Functional traits contributing to Snake River wheatgrass's superior performance under drought are its higher specific leaf area, higher specific root length, and greater water use efficiency. Snake River wheatgrass also used more water under the non-drought treatment. Goldar bluebunch wheatgrass showed the best drought tolerance of all bluebunch populations, and it used more water under the non-drought treatment. These data explain why Snake River has become a successful surrogate for bluebunch wheatgrass in the Intermountain West and suggest functional traits that should be considered while developing plant materials of these species with enhanced drought tolerance.
Technical Abstract: An ideal species for restoration in rangelands of the U.S. Intermountain West would tolerate drought and also grow rapidly to successfully compete with invasive winter annuals. However, a trade-off between stress tolerance and high growth rate would complicate the choice of plant material for restoration. We conducted a greenhouse experiment to compare the performance of Pseudoroegneria spicata and Elymus wawawaiensis, two closely related perennial, C-3 Triticeae bunchgrasses native to the Intermountain West, USA, under high, medium, and low watering frequencies. We predicted that E. wawawaiensis would have a higher relative growth rate and higher SLA than P. spicata, while P. spicata would be more drought tolerant. We also expected lower shoot biomass, higher stomatal conductance (SC), lower water use efficiency (WUE) under drought, and higher specific root length (SRL) in E. wawawaiensis compared to P. spicata resulting from a trade-off. Relative to high watering frequency, low watering frequency significantly decreased total (64.1%), shoot (63.2%), and root (71.47%) biomass across species. Elymus wawawaiensis had 27.1% greater shoot biomass, 44.4% greater SLA, 8.1% higher R/S, and 14.5% greater WUE than P. spicata across watering frequencies. Compared to P. spicata, E. wawawaiensis had greater biomass at all watering frequencies and a more favorable physiological response to drought at low watering frequency. These results show no evidence of a trade-off between drought and growth responses between the two species; E. wawawaiensis has greater potential both to maintain high growth rate under non-limiting conditions and to tolerate drought under limiting conditions relative to P. spicata.