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Characteristics of Successful Competitors: An Evaluation of Potential Growth Rate in Two Cold Desert Tussock Grasses

D. M. Eissenstat and M. M. Caldwell
Oecologia
Vol. 71, No. 2 (Jan., 1987), pp. 167-173
Published by: Springer in cooperation with International Association for Ecology
Stable URL: http://www.jstor.org/stable/4218142
Page Count: 7
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Characteristics of Successful Competitors: An Evaluation of Potential Growth Rate in Two Cold Desert Tussock Grasses
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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.

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