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Burning and Browsing Effects on Willow Growth in Interior Alaska

1978; Wiley; Volume: 42; Issue: 1 Linguagem: Inglês

10.2307/3800700

1937-2817

Jerry O. Wolff,

Ecology and Vegetation Dynamics Studies

Productivity and utilization of browsed and unbrowsed Scouler willow (Salix scouleriana) was measured in a 1971 burn and in an adjacent 70-year-old mature black spruce (Picea mariana) forest. Production of available willow browse in the burn increased from 8 kg/ha in 1973 to 22.6 kg/ha in 1974. The greatest production came from branches which had been browsed the previous winter. In the burn in 1974, an average browsed branch produced 4.0 g of new growth, whereas an unbrowsed branch produced 2.4 g. The available willow browse produced in the control in 1974 was 9.9 kg/ha, with a browsed branch producing 2.8 g and an unbrowsed branch 0.8 g. Willow shrubs are able to compensate for loss of biomass due to overwinter browsing by increased productivity of browse-damaged stems. J. WILDL. MANAGE. 42(1):135-140 During winter, moose (Alces alces) in Alaska feed primarily on shoots and branches of willow (Salix spp.), birch (Betula papyrifera), aspen (Populus tremuloides), and balsam poplar (Populus balsamifera) (LeResche and Davis 1973, Cushwa and Coady 1976). These hardwoods are frequently associated with plant communities characteristic of early successional stages after burning (LeResche et al. 1974, Viereck 1973). Browse production in early seral stage development is high, and the shoots and branches of woody browse species are numerous and within reach of mammalian herbivores (Spencer and Chatelain 1953, Leege 1968). Klein (1970) suggested that quality and digestibility of forage are as important as quantity and availability, and Cowan et al. (1950) and Leege (1969) stated that quality is related to successional stage. Trees and woody shrubs often grow out of reach in later successional stages and thus the number of small twigs and branches available as forage is reduced (LeResche et al. 1974, Spencer and Hakala 1964). During the later 1950's, moose populations appeared to increase throughout interior Alaska (U.S. Fish & Wildlife Service unpubl. reports, Coady 1973) concurrent with an increase in seral range created by wildfires (Hardy and Franks 1963, Barney 1969). Early seral stage communities created by fire can increase the carrying capacity of winter range (Spencer and Chatelain 1953, Leege 1968, 1969). The dominant species in mature forests of interior Alaska is either white spruce (Picea glauca) or black spruce (P. mariana), with woody shrubs present at lower densities (Viereck 1973). The biomass of forage available to moose at various successional stages has not been determined for this region of interior Alaska, though it has been done elsewhere by Bishop (1969) and Milke (1969). I compared current annual growth of browsed and unbrowsed Scouler willow on a burn and on an adjacent mature black spruce forest. The role of fire in improving winter moose habitat through increased production of woody browse was also examined. Data were collected in 1974 and 1975.