Feedback dynamics of grazing lawns: Coupling vegetation change with animal growth

- Authors: B. T. Person, M. P. Herzog, R. W. Ruess, J. S. Sedinger, R. M. Anthony, and C. A. Babock
  
  Date: 2003
  
  Journal: Oecologia
  
  Volume: 135
  
  Number: 4
  
  Pages: 583-592
  
  Summary of Methods: The effects of grazing by Black Brant (Branta bernicla nigricans) geese on plant community zonation and gosling growth were investigated from 1987 and 2000 at the Tutakoke River brant colony (61Ëš 15â€™ N, 165Ëš 30â€™ W) in southwestern Alaska. Plots of C. ramenskii were subjected to four treatments combinations of mowing and grazing (ungrazed control, grazed control, a mowed plot adjacent to the grazed control plot, and a mowed plot 150 m away from the other plots in an ungrazed meadow). In a second experiment, six exclosures within C. subspathacea grazed lawns, and six unfenced control plots were established, with forage quality of vegetation compared throughout the year. Aboveground biomass was measured in June 1994, again in July 1997, and in July 2001. Brant nests on sixty-seven plots were annually searched for from 1985 to 1997.
  
  Article Summary / Main Points: Mowed plots had lower aboveground biomass at all locations. Grazing pressure was lowest on the ungrazed control plots when compared to mowed or grazed plots. In the year after plots were mowed, fecal counts were higher on mowed plots than on control plots across all locations. Aboveground biomass was higher on all mowed plots in 1997 as compared to 1996. In 1996, Carex ramenskii had higher nitrogen and lower C:N ratio compared to control plots. Nutritional quality and aboveground biomass of geese grazed plots of C. subspathacea was similar to mowed plots of C. ramenskii plots. The low nesting success and number of families using brood rearing areas in 1997 decreased 61% compared to 1996. By 2000, the population of brant nesting at Tutakoke had recovered with a net increase over 1996 levels.
  
  Vegetation Types: Riparian and Wetlands
  
  MLRA Ecoregions: Not Applicable
  
  Agrovoc Control Words: Riparian zones Grazing Wildlife
  Article Review Type: Refereed
  
  Article Type: Experimental Research
  
  Keywords: carex, geese, phenotypic plasticity, plant-animal interactions, salt marsh
  
  Annotation: This was a replicated study over two years and is applicable to grazing of salt marshes by geese. The results suggest that if herbivory continues to increase, the area covered by grazing lawns may indicate a numerical increase in black brant geese. Grazing was not controlled by researchers; sites were only classified as grazed or ungrazed. Examination of various levels of grazing intensities on plant community zonation and gosling growth is needed. A previous study by Person et al., (1998, J. Ecology 86:243-259) on forage variation in brood-rearing areas used by Black Brant geese in southwestern Alaska, also available on the RSIS website, can be used as an approach for long-term geese grazing management studies.

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