Submitted to: Environmental and Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/2007
Publication Date: 3/1/2008
Citation: Hardegree, S.P., Jones, T.A., Pierson Jr, F.B., Clark, P., Flerchinger, G.N. 2008. Dynamic Variability in Thermal-Germination Response of Squirreltail (Elymus elymoides and Elymus multisetus). Environmental and Experimental Botany 62:120-128. Interpretive Summary: Bottlebrush and big squirreltail are two high priority species for fire rehabilitation and restoration of rangelands in the western United States. Seed germination and emergence are critical first processes in establishment of revegetation species in the field. The purpose of this study was to develop new techniques for assessing seedlots for relative suitability for different environmental conditions in the field. We evaluated germination response to temperature of 41 squirreltail seedlots collected from across the western United States. Models constructed from this data were used to simulate potential germination response to temperature for different planting dates under the variety of field conditions estimated to have occurred in the field over a 38-year test period. This provided a more ecologically relevant basis for comparing seedlots than previous methods that were based on single germination indices derived solely from constant-temperature laboratory experimentation. This methodology was successfully used to distinguish between different germination syndromes for these seedlots that may be important in selecting the appropriate plant materials for burn-rehabilitation and restoration projects in the field.
Technical Abstract: Bottlebrush squirreltail (Elymus elymoides) and big squirreltail (Elymus multisetus) have been identified as high-priority species for restoration and rehabilitation of millions of acres of rangeland in the western United States that have been degraded by wildfire and introduced annual weeds. In this study, squirreltail accessions from Idaho, Colorado, Utah, Arizona and New Mexico were grown in a nursery environment to produce seeds in two different years for germination evaluation at 11 constant temperatures. A statistical-gridding model was used to predict cumulative germination rate of each seedlot for 8 simulated planting dates between 1-Jan and 28-May over a 38-year seedbed-microclimatic simulation. Predicted germination response under simulated conditions of field-variable temperatures yielded a broader ecological basis for the relative ranking of thermal response than was obtained from single-value germination indices derived from either constant-temperature experiments, or from analysis of thermal-time coefficients.