ASSESSING THE IMPACT OF HISTORICAL FIRE REGIMES AND LOGGING ON FOREST COMPOSITION, STRUCTURE, REGENERATION, AND RADIAL GROWTH ON THE MENOMINEE TRIBAL LANDS, MENOMINEE COUNTY, WISCONSIN

Basal cross-sections were cut from 110 eastern white pine (Pinus strobus), 22 red pine (Pinus resinosa), 30 red oak (Quercus rubra), and 14 northern pin oak (Quercus ellipsoidalis) in harvested stands in Menominee County, Wisconsin to reconstruct historical fire occurrence and the effects of climate and logging on annual tree growth. Fire scars were identified and recorded for each sample, and fire return intervals were calculated for the time periods before and during active fire suppression. Mean fire return intervals prior to active fire suppression activities (1935) ranged from 5.5 to 23 years for each stand and increased to 9 to 67 years during active fire suppression. Fire wounding occurred primarily in the dormant season of late autumn to early spring. Tree diameter at time of fire wounding ranged from 1.5 to 101 cm for all fire events, with most averages ranging from 7.1 to 29.7 cm, suggesting most trees survived fire-scarring at relatively small diameters. Superposed epoch analysis (SEA) showed that mean Palmer Drought Severity Index (PDSI) departure values were significantly lower one year prior to the fire years. Annual growth rings were cross-dated, measured, and master chronologies were constructed from detrended annual radial growth for the dominant species in each stand. Northern pin oak yielded the highest annual growth followed by white pine, red oak, and red pine. Percent growth change determined for five years before and five years after fire events showed that species exhibiting a 25% increase in growth following fire occurred entirely in the nineteenth century, while percent growth change in the twentieth century did not increase beyond this threshold, possibly due to differences in stand structure. Circular nested vegetation plots were placed in 14 stands in order to analyze forest composition, structure and regeneration. Importance values show 8 of 14 stands were dominated by white pine, while red oak and red maple (Acer rubrum) each ranked highest in importance value in two stands. Red maple was often recorded as having the highest density of trees sampled per stand. Sapling and seedling layers both consisted primarily of red maple and sugar maple (Acer saccharum). This study suggests that fire was an important factor in the perpetuation of pine and oak species which are dominant throughout Menominee County. As a result of fire suppression activities, forest composition is shifting from species such as pine and oak that thrive in pyrogenic environments, to fire-sensitive species such as maple, beech (Fagus grandifolia), basswood (Tilia Americana), and birch (Betula spp.). Such changes in forest composition could result in decreased flammability of forest fuels and eventually a complete change in the historical fire regime of pine and oak forests of Menominee County.