Decay Dynamics of Coarsewood Habitat in Old-Growth Spruce and Pine Stands in the Rocky Mountain Foothills

In this study, we quantify and compare the relationships among coarsewood decay rates, morphological characteristics, and potential wildlife habitat value for old-growth stands dominated by white spruce (Picea glauca) or lodgepole pine (Pinus contorta) in west-central Alberta. In summer 2008, we sampled five spruce and five pine permanent sample plots, in stands estimated to be at least 160 years old during plot establishment in 1956. In each plot, all snags (standing dead trees) and logs were assessed for species, size, decay class, and morphological and habitat attributes (snags: n=193 for spruce plots, n=120 for pine plots; logs: n=192 for spruce plots, n=212 for pine plots). We used dendrochronological techniques on a stratified random subsample of snags and logs to determine year of death in order to estimate coarsewood decay rates. Decay class was assessed using a nine-class system for snags and a five-class system for logs. Snags with intermediate decay classes (DC 4) were the most abundant: we found a total of 207 snags in DC 4, compared to 46 in DC 3, 60 in DC 5, and 1 in DC 6. Similarly, logs in intermediate decay classes (DC 3) were also most abundant: we found a total of 244 logs in DC 3, compared to 9 in DC 1, 41 in DC 2, 105 in DC 4, and 5 in DC 5. Analysis is ongoing; however, we predict that snags and logs in more advanced stages of decay will have a greater potential to serve as habitat for coarsewood-associated wildlife. These findings will refine parameters for coarsewood models, which are an important tool in developing best management practices for managed forests