Snag longevity and decay class development in a recent jack pine clearcut in Michigan

Abstract

To better understand the factors that influence the longevity and decay class development of natural and girdled snags in jack pine (Pinus banksiana Lamb.) plantations managed for Kirtland's warbler (Dendroica kirtlandii Baird) breeding habitat in the northern Lower Peninsula of Michigan, we followed the fate of 335 jack pine and oak (Quercus spp.) snags. After 2.5 years, 41% of snags snapped or uprooted, with most snapping or uprooting occurring within the first year. Jack pine snags experienced higher rates of snapping or uprooting than oak or all other snags combined, regardless of whether natural or girdled. Girdling by itself or as an interaction term had no significant effect on snapping or uprooting for either jack pine or oak, but both diameter (P = 0.03) and height (P = 0.01) influenced snapping and uprooting in oak. Thirty months after treatment, the percentage of snags among decay classes differed between species of snag and snag types (natural-girdled), with snag height inversely related to snag decay class development. These results suggest that snag development will occur rapidly in recently clearcut jack pine stands and that higher densities of snags may be needed to be retained or created if management goals are to emulate more natural conditions.