A test of grazing compensation and optimization of crested wheatgrass using a simulation model
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Authors: B. E. Olson, R. L. Senft, and J. H. Richards
Date: 1988
Journal: Journal of Range Management
Volume: 42
Number: 6
Pages: 458-467
Summary of Methods: A simulation model was created and verified using data from field experiments, to determine the compensatory growth of crested wheatgrass (Agropyron desertorum) after grazing, at different times during the season, and to determine the combination of grazing time and intensity after wet, dry, and normal winters that would produce maximum regrowth. The model predicted that the greatest crested wheatgrass regrowth would occur after mid to late-May defoliations, due to the morphological stage of the plant and the availability of soil moisture following defoliation. Grazing crested wheatgrass three times at all intensities during the season optimized tiller production, however, greater frequencies or intensities of defoliation generally reduced total biomass production, especially after dry winters. Therefore, the authors concluded that regrowth of crested wheatgrass does vary by timing of grazing and that the productivity of crested wheatgrass pastures will not increase under intensive rotational grazing management.
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: crested wheatgrass, agropyron desertorum, tiller, defoliation, ramets, ramet population model, production model
Annotation: For the model validation methods: Growth and regrowth were simulated for the springs of 1983, 1984, and 1985. Regrowth following defoliation was simulated for 3 dates of defoliation in each growing season, May 15, June 1, and June 15. At each simulated defoliation, 55% of the non defoliated tillers were "grazed" at heights ranging from 47-90 mm. This simulated 50-70% removal of the current season's herbage production. For the grazing compensation simulation, to assess the effects of time of grazing on the degree of compensation, single defoliations from 5-95 days (at 1-day intervals) after spring growth started were simulated. A run with no defoliation was the control. In each trial, 50% of the standing crop was removed. For the grazing optimization simulation, simulated plots were defoliated 1 to 6 times in a 60 day grazing season, May to June. Defoliation intensity was varied from 10-90% of standing herbage. The simulations were repeated for dry, normal, and wet winters (September-May precipitation).
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