title: Characteristics of successful competitors: an evaluation of potential growth rate in two cold desert tussock grasses.
abstract: Within the first few weeks after seedling emergence, Agropyron desertorum, a more competitive tussock grass, had a much higher mean relative growth rate (RGR) than Agropyron spicatum, a very similar, but less competitive species. However, beyond the early seedling stage, the two grasses had a remarkably similar whole-plant RGR in hydroponic culture and aboveground RGR in glasshouse soil, if root temperatures were above approximately 12°C. At soil temperatures between 5 and 12°C, A. desertorum exhibited a 66% greater aboveground RGR than A. spicatum (P<0.05). Both species responded similarly to warming soil temperatures. In the field, however, tiller growth rates were generally similar. Neither species showed marked tiller elongation until a couple of weeks after snowmelt, by which time soil temperatures, at least to a depth of 10 cm, were above 12°C for a significant portion of the day. Aboveground biomass accumulation over a three-year period indicated that both grasses had similar potential growth rates whereas Artemisia tridentata ssp. vaseyana, a common neighbor planted in the same plots, had a much greater potential growth rate. The greater competitive ability of adult A. desertorum, as compared to A. spicatum, cannot be attributed to appreciable differences in potential growth rates.
authors.affiliation: Range Science Dept., Utah State University, 84322-5230, Logan, UT, USA.|the Ecology Center, Utah State University, 84322-5230, Logan, UT, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Eissenstat
authors.affiliation: Range Science Dept., Utah State University, 84322-5230, Logan, UT, USA.|the Ecology Center, Utah State University, 84322-5230, Logan, UT, USA.
authors.forename: M M
authors.initials: MM
authors.lastname: Caldwell
keywords: Agropyron; Artemisia; Competition; Relative growth rate; Tussock grass