02496nas a2200133 4500008004100000245009100041210006900132300001300201490000700214520198100221653002202202100001902224856011902243 1989 eng d00aDensity and growth stage-dependent responses to defoliation in two rhizomatous grasses0 aDensity and growth stagedependent responses to defoliation in tw a414 -4200 v803 a
Responses to defoliation were studied in two tallgrass prairie perennials (Andropogon gerardii and Panicum virgatum) established from seed at three densities. P. virgatum was also grown from transplanted rhizomes of established clones. Plants of both species displayed a continuum of responses to defoliation, from large reductions in biomass, tillering and seed production to significant increases in one or more performance measures. In crowded populations, defoliation shifted plants into subordinate positions within the competitive hierachy. Plants competing inrtaspecifically and those that were initally small suffered more from defoliation than either plants grown at low density or those that were larger than their neighbors. At the highest plant density, the effects of defoliation or initial plant size were overshadowed by the effects of crowding. When defoliated and grown at similar densities, P. virgatum and A. gerardii grown from seed showed large reductions in biomass, seed production, and new rhizome production, but established P. virgatum ramets grown from rhizomes showed increases in these performance measures. Thus herbivory may be particularly detrimental to P. virgatum during juvenile stages before perennating organs have developed. Overcompensation of P. virgatum clones in reaponse to defoliation only occurred if all ramets within the clone were defoliated. In clones containing both defoliated and undamaged ramets, there were no differences in their performance, suggesting that genets are capable of integrating the effects of differential defoliation among shoots. Defoliated P. virgatum clones allocated a smaller fraction of their total biomass to new rhizomes, indicating that the short-term regrowth response following defoliation may incur a longer-term cost associated with gradual reduction in biomass of the perennating organs and reduced genet success. Key words: Herbivory, Competition, Clonal growth, Panicum, Andropogon
10atallgrass prairie1 aHartnett, D.C. uhttp://lter.konza.ksu.edu/content/density-and-growth-stage-dependent-responses-defoliation-two-rhizomatous-grasses