Abstract
A prediction from the herbivore optimization hypothesis is that for every combination of site/habitat type and plant community type there is a grazing intensity that causes a maximum increase in above-ground net primary productivity compared with the ungrazed control. NPP is defined as the rate of change in green, herbaceous biomass per unit time per unit area. We tested this hypothesis in the primary summer range of a growing population of wood bison (Bison bison athabascae) within the Mackenzie Bison Sanctuary, Northwest Territories, Canada. Plots (0.5 × 0.5 m2) in graminoid meadows dominated by awned sedge (Carex atherodes) were either clipped at 3 cm, exposed to wood bison grazing, temporarily protected for 3 weeks, or permanently protected. This resulted in the removal of 100%, 0-79%, 0-79% or 0%, respectively, of shoot tissue available to wood bison. NPP of meadows clipped twice at 3 cm in 1986 was the same as control NPP at 5 study sites. In 1987, only the 2 most productive study sites of 1986 were intensively examined: plots clipped once in early summer increased in NPP by 120% and 133% compared to controls; NPP of meadows grazed by wood bison increased by 200% compared to controls at the most productive site, but remained the same as controls at the less productive site. Therefore, the herbivore optimization hypothesis was accepted at the 2 most productive sites in 1987, but rejected at all 5 study sites in 1986. In 1987, the standing crop of dead material was 258% and 142% higher in controls than in grazed plots at the 2 most productive sites. We think this dead material was responsible for the lower NPP observed in control plots.
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Abbreviations
- NPP:
-
Net Primary Productivity
References
Atmospheric Environment Service. 1985. Environ. Can. Microfiche Ser. 101. Ottawa.
Bazely, D.R. and R.L. Jefferies. 1989. Lesser Snow Geese and the nitrogen economy of a grazed salt marsh. J. Ecol. 77:24–34.
Belsky, A.J. 1986. Does herbivory benefit plants? A review of the evidence. Amer. Natur. 127:870–892.
Briske, D.D. and V.J. Anderson. 1990. Tiller dispersion in populations of the bunchgrass Schizachyrium scoparium: implications for herbivory tolerance. Oikos 59:50–56.
Brown, B.J. and T.F.H. Allen. 1989. The importance of scale in evaluating herbivory impacts. Oikos 54:189–194.
Cargill, S.M. and R.L. Jefferies. 1984. The effects of grazing by Lesser Snow Geese on the vegetation of a sub-arctic salt marsh. J. Appl. Ecol. 21:669–686.
COSEWIC. 2000. Committee on the Status of Endangered Wildlife in Canada. Environment Canada. Government of Canada.
Cronquist, A. 1984. A Classification of Flowering Plants. Columbia Univ. Press, New York.
DeAngelis, D.L. and M.A. Huston. 1993. Further considerations on the debate over herbivore optimization theory. Ecol. Appl. 3:30–31.
Ecoregions Working Group. 1989. Ecoclimatic Regions of Canada. Ecol. Land Classification Ser., No. 23, Sustainable Development Branch, Can. Wildl. Serv., Conserv. and Protection, Environ. Can., Ottawa.
Gates, C.C. and N.C. Larter. 1990. Growth and dispersal of an erupting large herbivore population in northern Canada: The Mackenzie Wood Bison (Bison bison athabascae). Arctic 43:231–238.
Hik, D.S. and R.L. Jefferies. 1990. Increases in the net above-ground primary production of a salt-marsh forage grass: a test of the predictions of the herbivore-optimization model. J. Ecol. 78:180–195.
Hilbert, D.W., D.M. Swift, J.K. Detling and M.I. Dyer. 1981. Relative growth rates and the grazing optimization hypothesis. Oe-cologia 51:14–18.
Lacey, J.R. and H.W. Van Poollen. 1981. Comparison of herbage production on moderately grazed and ungrazed western ranges. J. Range Manage. 34:210–212.
Larter, N.C. and C.C. Gates 1991. Diet and habitat selection of wood bison in relation to seasonal changes in forage quantity and quality. Can. J. Zool. 69:2677–2685.
Levin. R.I. 1981. Statistics for Management. 2nd Edition. Prentice Hall Inc. Englewood Cliffs, N.J.
McNaughton, S.J. 1979. Grassland-herbivore dynamics, p.46–81. In: A.R.E. Sinclair and M. Norton-Griffiths (eds.), Serengeti: Dynamics of an Ecosystem. Univ. Chicago Press, Chicago, Ill.
McNaughton, S.J. 1985. Ecology of a grazing ecosystem: The Serengeti. Ecol. Monogr. 55:259–294.
Painter, E.L. and A.J. Belsky. 1993. Application of herbivore optimization theory to rangelands of the western United States. Ecol. Appl. 3:2–9.
Ritchie, M.E., D. Tillman and J.M.H. Knops. 1998. Herbivore effects on plant nitrogen dynamics in oak savanna. Ecology 79:165–177.
Smith, D.L. 1990. The impacts of Wood Bison (Bison bison athabacae) grazing on a sub-hygric shrub meadow plant community type, Mackenzie Bison Sanctuary, Northwest Territories. M.S. Thesis. Univ. Alberta. Edmonton.
Smith, D.L. 1996. A test of the herbivore optimization hypothesis using muskoxen and a graminoid meadow plant community. Rangifer 16:69–77.
Sokal, R.R. and F.J. Rohlf. 1981. Biometry. The Principles and Practices of Statistics in Biological Research. 2nd Ed. W.H. Freeman and Company, New York, N.Y.
The Wildlife Society. 1994. Research and Management Techniques for Wildife and Habitats. Edited by T.A. Bookhout, 5th edition. 740 p.
Tiffin, P. 2000. Mechanisms of tolerance to herbivore damage: what do we know? Evolutionary Ecology 14: 523–536.
Trlica, M.J., M. Buwai and J.W. Menke. 1977. Effects of rest following defoliations on the recovery of several range species. J. Range Manage. 30:21–27.
Willms, W.D. 1991. Cutting frequency and cutting height effects on rough fescue and Parry oat grass yields. J. Range Manage. 44:82–86.
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Smith, D.L., La Roi, G.H. The response of subhumid mid-boreal graminoids to grazing by wood bison. COMMUNITY ECOLOGY 6, 39–47 (2005). https://doi.org/10.1556/ComEc.6.2005.1.5
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DOI: https://doi.org/10.1556/ComEc.6.2005.1.5