Effects of water frequency on individual plant performance: Implications for restoration

Seedling establishment is very critical and challenging for rangeland restoration and management. The effect of water frequency on plant seedling development was tested with two native perennial bunchgrasses of the Intermountain sagebrush steppe ecosystems of the northwestern United States. We compared morphological and physiological traits potentially responsible for seedling establishment of the widely occurring Pseudoroegneria spicata [Pursh] A. Löve and its often-used, yet relatively restricted surrogate, Elymus wawawaiensis J. Carlson & Barkworth. In a glasshouse experiment, we exposed seedlings of four populations of P. spicata and two populations of E. wawawaiensis to low, medium, and high watering frequencies. Low watering frequency had a negative impact on shoot and root biomass and stomatal conductance. Regardless of watering frequency, E. wawawaiensis maintained greater values for shoot and root biomass. On average, low watering frequency reduced P. spicata (E. wawawaiensis) shoot biomass by 66.10 % (52.78 %), root biomass 73.2% (73.5%), and stomatal conductance by 50.18 % (67.11 %) relative to high watering frequency. Compared to P. spicata a larger reduction in stomatal conductance for E. wawawaiensis was accompanied by a smaller reduction in biomass. These results suggest a useful protocol for selecting restoration plant materials that perform better under moisture stress.