Managing forests according to ecological principles requires an understanding of disturbance effects and stand development processes characteristic of a given ecosystem. In ecosystems dominated by jack pine (Pinus banksiana Lamb.) in northern Michigan, stand-replacing wildfires historically created extensive areas of young, even-aged jack pine stands that provided breeding habitat for the Endangered Kirtland’s warbler (Dendroica kirtlandii Baird). Kirtland’s warbler (KW) habitat is currently managed intensively as jack pine plantations, but the success of KW recovery efforts has increased interest in managing jack pine ecosystems for a broader suite of ecological components. As part of a larger effort to understand the natural range of variability in jack pine forest structure and composition, we quantified forest fuel loads and evaluated tree species composition in young (2-4 years post-fire, pre-KW occupancy) and mature (22-38 years post-fire, post-KW occupancy) wildfire-regenerated jack pine stands. Fuels were characterized using the line-intercept methods developed by the USDA Forest Service Forest Inventory and Analysis Program, and tree species composition and basal area were measured in 50-m2fixed radius plots. Differences between age classes (pre- and post-KW occupancy stands) were quantified using t-tests.
Results/Conclusions
Forest litter or duff, woody debris, total dead, and total live+dead fuel did not differ between young and mature stands. Mean total biomass of dead fuels across both age classes was 33.6 ± 0.9 Mg ha-1. Young stands supported 144% greater mass of live fuels than mature stands (p=0.01), whereas tree basal area was 312% greater in mature than young stands (p=0.04). Although all stands were dominated by jack pine compositionally, red pine (P. resinosa Sol.), northern pin oak (Quercus ellipsoidalis E.J. Hill), bigtooth aspen (Populus grandidentata Michx.) and black cherry (Prunus serotina Ehrh.) were also common. Residual mature red pine trees comprised the majority of tree basal area in young jack pine stands. Our research will contribute to an understanding of the heterogeneity in structure and composition of jack pine ecosystems following wildfire in northern Michigan. Data from this project will inform ecological forest management decisions that aim to incorporate natural stand characteristics into habitat treatments, both during preparation for establishing new plantations and for creating more natural patterns in mature, post-KW occupancy plantations.