Density- and growth stage-dependent responses to defoliation in two rhizomatous grasses
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Authors: D. C. Hartnett
Date: 1989
Journal: Oecologia
Volume: 80
Number:
Pages: 414-420
Summary of Methods: Hartnett measure the responses of Andropogon gerardii and Panicum virgatum to defoliation under different clipping intensities, plant densities, and plant growth forms. In general, defoliation reduced plant and reproductive biomass and tiller and seed production of plants grown from seed. These negative effects were enhanced when plant densities were increased. Plants competing intraspecifically and those that were initially 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. However, biomass, rhizome and seed production were all enhanced by clipping when Panicum virgatum plants were grown from rhizomes rather than seeds. The results of this study suggest that the negative responses of Andropogon gerardii and Panicum virgatum to clipping are enhanced by competition and may only occur in young plants vulnerable to defoliation.
Article Summary / Main Points: None
Vegetation Types:
MLRA Ecoregions:
Agrovoc Control Words: Riparian zones Rangelands Wildlife
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: andropogon gerardii, panicum virgatum, herbivory, competition, clonal growth, simulated herbivory, plant density
Annotation: Experiments were conducted in a greenhouse. Plant were clipped to a 4-cm stubble height, however, the number and characteristics of defoliated plants varied by treatment. Half of the plants were left undamaged as controls. In the first experiment Andropogon gerardii and Panicum virgatum plants were grown from seed at three densities and defoliated: In pots with a single plant, the plant was clipped to 4-cm. In pots at medium (4 plants/pot) and high (8 plants/pot) density the largest or the smallest plant was clipped. In the second experiment, Panicum virgatum plants were grown from rhizomes were defoliated when ramet density reached 160 stems/m2: All stems were clipped to 4-cm. Half of the stems were clipped to 4-cm.
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