Experimental evaluation of the grazing optimization hypothesis

The herbivore grazing optimization hypothesis predicts an increase in aboveground net primary productivity (ANPP) at a moderate grazing intensity. The hypothesis was tested by grazing controlled densities (0 to 145 individuals/m2) of big-headed grasshoppers (Aulocara elliotti Thomas) for short time spans (7 to 13 days) on enclosed swards (0.7 m2) of blue grama [(Bouteloua gracilis) (Willd. ex H.B.K.) Lag. ex Griffiths]. ANPP of each of 257 experimental enclosures was estimated following regrowth by using a standing crop index (the product of mean total blade length per tiller and percent basal cover) after the grazing period and clipping after the regrowth period. ANPP was not significantly reduced by grazing in any of the 5 short-duration grazing experiments. In 2 of the 5 experiments, ANPP increased significantly with grazing. In 1 of the other 3 experiments there was evidence for the grazing optimization hypothesis.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact lbry-journals@email.arizona.edu for further information.Migrated from OJS platform August 202