The impact of the timing of brush management on the nutritional value of woody browse for moose Alces alces.
Abstract
We examined how the removal of above-ground biomass (mechanical brushing) at different times of the year affected the nutritional value of regenerating shoots of Scouler's willow Salix scouleriana for moose for 2 winters after brushing. Brushing trials were conducted throughout the 1996 and 1997 growing seasons in central British Columbia on a 10-year-old regenerating clear-cut replanted in lodgepole pine Pinus contorta var. latifolia. We assessed the nutritional value of the browse in relation to length, diameter, mass, digestible energy, digestible protein, tannin and lignin content of current annual growth shoots in winter, as well as the phenology of plant leafing. One winter after brushing, willows brushed in early July had shoots that were lower in lignin, higher in digestible protein and lower or not different in tannin content compared with shoots from earlier brushed or unbrushed willows. Willows brushed in early July also had long, heavy, shoots that were high in digestible energy and delayed leaf senescence. In the second winter after brushing, willows that were brushed in July had larger shoots that were lower in digestible energy, digestible protein, tannin and lignin content and delayed leaf senescence compared with several other treatments. Willows brushed after July regenerated negligible shoot material in the first year after brushing. Willows brushed in September delayed leaf flush in the first post-brushing spring. To increase the nutritional value of woody browse for cervids, we suggest that brushing should be performed in early to mid-July (mid-summer). Reductions in browse quality and quantity may negatively affect many mammalian species. Therefore, we recommend that the needs of other fauna potentially affected by changes in shrub architecture, shoot morphology and shoot chemistry be considered when planning the timing of brush management activities.