Herbivore effects on plant and nitrogen dynamics in oak savanna
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Authors: M. E. Ritchie, D. Tilman, and J. M. H. Knops
Date: 1998
Journal: Ecology
Volume: 79
Number: 1
Pages: 165-177
Summary of Methods: This study was initiated to determine if herbivores increase or decrease the rate of nutrient cycling in oak savanna plant communities. Plant communities inside of exclosures had more above-ground biomass, which responds positively to increased nutrient availability, and less below-ground biomass than plant communities exposed to deer (Odocoileus virginianus) herbivory. Legumes and woody plants, which can affect N fixation rates and microsite characteristics, were shorter and had lower percent cover in plots exposed to deer herbivory than inside exclosures. The authors results support the hypothesis that herbivores indirectly decelerate N cycling by decreasing the abundance of plant species with nitrogen-rich tissues. However, other factors, such as disturbance from fire, may mediate herbivore effects on long-term changes in N and C pools. Herbivores may therefore indirectly control productivity, N cycling, and succession by consuming nitrogen-fixing and woody plants that have strong effects on plant resources.
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: legumes, herbivores, nitrogen, plants, positive feedback, savanna
Annotation: In June of 1989, 10 plots were placed randomly on existing vegetation within an area. Five of these plots excluded mammalian herbivores with fences, insecticides, and pesticides. The remaining 5 plots were controls that received a window-screen lid during mid-June-late August. Deer browsed, walked, and eliminated wastes in these plots during September-May. They sampled aboveground plant biomass in June and August of 1989 and 1995 by clipping herbaceous vegetation to ground level, but only current annual growth was clipped from woody plants.
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