Drought tolerance in two perennial bunchgrasses used for restoration in the Intermountain West,USA

An ideal restoration species for the semi-arid Intermountain West, USA would be one that grows rapidly when resources are abundant in the spring, yet tolerates summer’s drought. We compared two perennial C_3, Triticeae Intermountain-native bunchgrasses, the widely occurring Pseudoroegneria spicata and the much less widespread Elymus wawawaiensis, commonly used as a restoration surrogate for P. spicata. Specifically, we evaluated seedlings of multiple populations of each species for biomass production, water use, and morphological and physiological traits that might relate to drought tolerance under three watering frequencies (WFs) in a greenhouse. Shoot biomass of E. wawawaiensis exceeded that of P. spicata regardless of WF. At low WF, E. wawawaiensis displayed 38% greater shoot biomass, 80% greater specific leaf area (SLA), and 32% greater precipitation use efficiency (PUE). One E. wawawaiensis population, E-46, displayed particularly high root biomass and water consumption at high WF. We suggest that such a plant material could be especially effective for restoration of Intermountain rangelands by preempting early-season weeds for spring moisture and also achieving high PUE. Our data explain how E. wawawaiensis has been so successful as a restoration surrogate for P. spicata and highlight the importance of measuring functional traits such as PUE and SLA when characterizing restoration plant materials.