Submitted to: Ecological Society of America Bulletin
Publication Type: Abstract Only
Publication Acceptance Date: August 2, 1998
Publication Date: N/A
Differences in root morphological and physiological plasticity between contrasting growth forms may contribute to changes in the ecological success of caespitose and rhizomatous grasses along environmental gradients. We hypothesized that caespitose and rhizomatous grasses exhibit greater physiological and morphological plasticity, respectively. Bouteloua gracilis (caespitose) and Agropyron smithii (rhizomatous) were compared at the Central Plains Experimental Range, while Schizachyrium scoparium (caespitose) and Andropogon gerardii (rhizomatous) were studied at Konza Prairie. Morphological plasticity was assessed with root ingrowth cores located between growth forms, and physiological plasticity was determined by 15N uptake. Bouteloua gracilis displayed significantly greater morphological plasticity, but significantly lower physiological plasticity at high 15N concentrations, compared to A. smithii. Conversely, S. scoparium displayed significantly higher physiological plasticity at all 15N concentrations, but a trend toward lower morphological plasticity than A. gerardii. Caespitose and rhizomatous grasses did not exhibit consistent differences in physiological and morphological plasticity at both sites as hypothesized. Rather, root plasticity appears to related more to the environment than grass growth form. These data suggest that both physiological and morphological root plasticity contribute to the ecological success of both caespitose and rhizomatous grasses along environmental gradients by enabling them to effectively forage for heterogeneously distributed soil resources.