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Title: A comparision of cumulative-germination response of cheatgrass (bromus tectorum) and four perennial bunchgrass species to simulated field-temperature regimes

item Hardegree, Stuart
item Jones, Thomas
item Pierson Jr, Frederick
item Clark, Pat

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/17/2007
Publication Date: 8/17/2007
Citation: Hardegree, S.P., B.A. Roundy, T.A. Jones, F.B. Pierson AND P.E. Clark. 2008. A comparision of cumulative-germination response of cheatgrass (Bromus tectorum) and four perennial bunchgrass species to simulated field-temperature regimes. In: Abstracts of the 61st Annual Meeting, Society for Range Management, Louisville, KY, January 26-31, 2008. (CD-ROM Abstract)

Interpretive Summary:

Technical Abstract: Cheatgrass (Bromus tectorum L.) dominates millions of acres of sagebrush-bunchgrass rangeland in the Intermountain western United States. It has been suggested that rapid germination, particularly at low temperatures in the late fall, winter and early spring, may contribute to the competitive success of this species. The purpose of this study was to compare potential germination response of cheatgrass and several other range grass species under a large number of potential field scenarios. Specific objectives were to assess thermal-germination response of multiple seedlots of each species, and to develop a more ecologically relevant basis for comparison of species. We evaluated thermal-germination response of multiple accessions of cheatgrass, bottlebrush squirreltail [Elymus elymoides (Raf.) Swezey], big squirreltail [Elymus multisetus (J.G. Smith) Burtt-Davy], bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) Löve] basin wildrye [Leymus cinereus (Scribn. and Merr.) A. Löve], thickspike wheatgrass [Elymus lanceolatus (Scribn. and J.G. Smith) Gould] and Sandberg bluegrass (Poa secunda Vasey) over the temperature range of 3 to 38°C. Germination-rate as a function of temperature was estimated for all subpopulations of each seedlot for every hour of a 38-year seedbed-microclimatic simulation. Hourly-rate estimates were summed to predict germination times as a function of subpopulation for 12 simulated planting dates in each year starting on Oct-9 and every 21-days thereafter until 28-May. Relative germination rate of cheatgrass was consistently higher, and basin wildrye consistently lower than the other species under all simulated conditions. Of the other species, bluebunch wheatgrass and big squirreltail exhibited the most rapid germination under cooler temperature regimes. The germination advantage of cheatgrass was greatest for the most rapidly germinating subpopulations of seeds. Thermal and hydrothermal simulation models of the type described in this study provide a more ecologically relevant basis for evaluating relative germination response than static germination indices, or comparison of model coefficients.