Browsing Society for Range Management Journal Archives by Authors
Experimental evaluation of the grazing optimization hypothesisWilliamson, S. C.; Detling, J. K.; Dodd, J. L.; Dyer, M. I. (Society for Range Management, 1989-03-01)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.
Nondestructive Estimation of Shortgrass Aerial BiomassWilliamson, S. C.; Detling, J. K.; Dodd, J. L.; Dyer, M. I. (Society for Range Management, 1987-05-01)A nondestructive technique for estimation of aboveground biomass of blue grama [Bouteloua gracilis (H.B.K) Griffiths] was designed for use on small sampling units (<1 m2). The technique combines measures of percent basal cover and mean total blade length per tiller and is recommended for experiments, such as small plot manipulations, that require an accurate and precise sampling method.