Plant-herbivore dynamics: Wapiti on alfalfa pastures

This study investigated fanned wapiti (Cervus elaphus) interactions with alfalfa (Medicago sativa L.) in Alberta, Canada. The first experiment compared wapitisimulated defoliation (stripping) versus mowing at three heights on mid-vegetative alfalfa. Stripping alfalfa led to quicker recovery to a harvestable stand (p < 0.001), but resulted in less regrowth (p < 0.05), less total biomass (p < 0.001), fewer crown-derived stems (p < 0.05), and lower quality forage (p < 0.05) than mowing. Recovery was three (p < 0.05) and ten (p < 0.001) days quicker for plants defoliated to a 15cm height than 7.5 and 2.5cm, respectively, but total biomass production (p < 0.05) and forage quality (p < 0.01) were lower for the tallest height. Regardless of treatment, the majority of post-treatment biomass was crown-derived rather than from axillary buds. Overall, mowing resulted in greater alfalfa quantity and quality but required longer stand recovery than stripping.; The second experiment focused on soluble root protein levels of alfalfa from April to October under four sward management systems (SMS) utilizing wapiti grazing and/or haying. Root protein levels were not different among SMS (p > 0.05), but differed among sampling dates across SMS (p < 0.001), decreasing during initial spring growth (April to early June), and increasing during late summer-fall (late August to October). Root protein levels were lower in October than April (p < 0.001), but were adequate for subsequent growth initiation and not different (p > 0.05) among SMS.; The third experiment examined wapiti feeding on pure alfalfa versus predominantly bromegrass (Bromus riparius Rehm. cv. Regar) pastures. In grass-dominated stands, estimated dry matter (R2 = 0.41, p < 0.001) and digestible energy (R2 = 0.39, p < 0.01) intake rates of wapiti were asymptotically related to available herbage, and superior to alfalfa-only stands at herbage levels below about 2500kg/ha. On pure alfalfa, dry matter (R2 = 0.81, p < 0.001) and digestible energy (R2 = 0.95, p < 0.001) intake rates fit a third order polynomial indicating wapiti foraging efficiency exceeded grass-dominated stands when herbage exceeded approximately 2500kg/ha.; Results of this study suggest graziers should consider grass:legume mixtures to maximize wapiti intakes over the widest range of available herbage, or, if managing pure alfalfa, consider short durational grazing and/or alternating hay cuts to foster abundant quality regrowth.