TEMPORAL EFFECTS OF MECHANICAL TREATMENT ON WINTER MOOSE BROWSE IN SOUTH-CENTRAL ALASKA

Abstract

Sites containing winter browse species utilized by moose on the Copper River Delta of south-central Alaska were mechanically treated (hydraulic-axed) to counteract possible earthquake-related increases in less-preferred forage species, and to measure treatment effects on biomass, height, nutritional quality (crude protein, lignin, and tannin), utilization, and snow burial on preferred (willow [Salix spp.]) and less-preferred forage species (sweetgale [Myrica gale], cottonwood [Populus trichocarpa], and alder [Alnus viridis sinuata]) within 3 winter scenarios (mild, moderate, and severe). Sites were treated in 4 winters (1990–1992, 2008, 2010, and 2012) within 5 stand types in 20 sites varying from 0.9–63.4 ha. We found few significant differences in biomass, height, nutritional quality, utilization, and snow burial relative to controls. However, our ability to detect differences may have been limited by sample size (n = 1–9), as visual comparison suggests hydraulic-axing may be an effective method for increasing willow biomass while reducing alder biomass without influencing nutritional quality. However, because treated willows were shorter than untreated willows, treatment may result in less preferred forage for moose in severe winters with deep snow. Our results have implications for habitat management of moose but further research is needed to determine incremental and long-term effects of treatment on willow growth and productivity.