Effects of Interactions among Two Prescribed Fires, Cover Type, and Canopy Cover on Oak and Red Maple Regeneration in Northern Lower Michigan

Regenerating oak (Quercus spp.) is a problem on most intermediate to high-quality sites throughout the eastern US. Oak is often present in the overstory and abundant in the understory, but is absent from the midstory due to increased competition from less-valuable mesic species such as Liriodendron tulipifera and Acer rubrum. Red maple has expanded its range dramatically since fire suppression began in the 1930s, and is an important competitor of oak. To study relationships between oak and silvicultural treatments, an experiment was initiated in 1990 that included three northern red oak (Quercus rubra)-dominated stands and three red pine (Pinus resinosa) plantations in northern Lower Michigan. Areas of each stand were thinned to four levels of canopy cover in 1991: clearcut, 25% residual canopy, 75% residual canopy, and uncut control, with caged and uncaged northern red oak seedlings planted within each treatment. A thick midstory of red maple developed over the subsequent ten years, hindering development of advance oak regeneration. Low-intensity, early-spring prescribed fires were conducted on all stands in 2002 and 2008 in an effort to control red maple. Heights of planted red oak and naturally occurring red maple and oak regeneration in three size classes were measured before and after each fire with the objectives to: 1) Test the hypothesis that oak sprouts would have greater height growth after the 2008 prescribed burn than after the 2002 prescribed burn; 2) Test the hypotheses that (a) red maple stems would be reduced to a greater degree following the 2008 burn than following the 2002 burn, and that (b) the number of natural oak stems would be increased to a greater degree following the 2008 burn than following the 2002 burn; and 3) Evaluate the relationships between post-burn planted oak sprout height and pre-burn planted oak sprout height, fire temperature, and canopy cover. Following the second fire, planted oak sprouts increased in height rapidly in pine stands, where there was little red maple competition, but grew less rapidly in oak stands. Red maple densities decreased more following the first fire than the second fire. The hypothesis that natural oak regeneration stem densities would increase to a greater degree following the 2008 burn than following the 2007 burn was not supported. Pre-burn planted oak height was the best predictor of post-burn planted oak height