The 2008 Joint Meeting of the Society for Range Management and the America Forage and Grassland Council. |
Wednesday, January 30, 2008 - 8:40 AM
Impacts of Simulated Herbivory on Small Honey Mesquite Plants
Barbara K. Witmore and Derek W. Bailey. Department of Animal and Range Sciences, New Mexico State University, PO Box 30003, MSC 3-I, Las Cruces, NM 88003
Simulated herbivory was used to evaluate the potential of livestock to control honey mesquite (Prosopis glandulosa). In study 1, small honey mesquite plants (< 0.5 m in height) were permanently identified and randomly assigned to multiple defoliation or undefoliated control treatments (n = 70). Over 90% of the leaves were removed 3 times per year by hand plucking for 3 consecutive years. Elliptical volume and leaf cover estimated from digital photographs were used to estimate leaf standing crop of individual plants (R2 = 0.60). Defoliated plants (5.4 ± 2.4 g · plant-1) produced less leaves (P = 0.001) than the undefoliated controls (17.6 ± 2.5 g · plant-1). Mortality of defoliated and control plants was 14% and 6%, respectively. In study 2, effects of single and multiple defoliations of small mesquite plants (n = 80) by hand plucking leaves or clipping stems were evaluated over a 2-year period. Elliptical volume was used to estimate above ground plant biomass for stem clipping treatments (R2 = 0.34). A single defoliation by either hand plucking leaves or clipping 20 or 80% of stem height did not affect leaf standing crop or plant biomass compared to controls (P > 0.20). After hand plucking 4 times, leaf standing crop was less than in controls (P = 0.02). Even after clipping 5 times at 20 or 80% of the original plant height, there was little evidence that plant biomass was reduced (P = 0.07) over controls. Clipping stems may require more time to have an effect on mesquite than leaf removal. Intense levels of herbivory can reduce the growth rate of small mesquite plants but have little effect on mortality. If livestock could be trained to forage on honey mesquite, they could be used to help manage, but not eliminate, this species in rangeland pastures.