Effects of Fire Intensity on Competitive Dynamics Between Red and Black Oaks and Mountain Laurel

We investigated the competitive response of oak and mountain laurel to prescribed fire on two sites in northeastern Connecticut. After nearly a decade, the competitive position of oak on moderately burned portions of both sites was little better, and in some respects worse, than on adjacent unburned controls. However, on portions of both sites where fire had killed much of the overstory, oak regrowth was vigorous and had escaped the dense mountain laurel layer. The results suggest hat light understory fires alone are not sufficient for oak regeneration, and that prescribed fire should be used only as part of an integrated strategy involving harvesting of the overstory. Ecologically, the results point to the importance of severe disturbances in maintaining the structure and function of oak ecosystems. North. J. Appl. For. 13(3):119-123. Although oaks form a significant por ion f the overstory across much of their range in North America, successful oak regeneration has remained an elusive silvicultural goal in many ecosystems (Hannah 1987, Crow 1988, Abrams 1992). Fire, which is not a major feature of modem forest landscapes in the northeastern United States, appears to have been an important factor promoting oak dominance in both preand postsettlement forests (Abrams 1992). Despite some disagreement, a broad range of ecological and historical studies suggests early upland forests in the Northeast experienced understory fires with a return period between 1 yr and 15 yr (Day 1953, Buell et al. 1954, Little 1974, Russell 1983), although fire regimes may shift with both cultural changes and changes in the physical climate (Thompson and Smith 1970, Overpeck et al. 1990, 1991). Numerous authors have suggested that an absence of fire limits oak regeneration (Lorimer 1984, Host et al. 1987, Abrams and Nowacki 1992), while other authors have pointed to a broad range of problems NOTE: The authors thank Yale University and the Yale Forest for support during this research. W. Keith Moser's current address is Tall Timbers Research, Inc., Rte. 1, Box 678, Tallahassee, FL 32312. This research was sponsored by the U.S. Department of Energy, Office of Energy Research, Environmental Sciences Division, Office of Health and Environmental Research, under appointment to the Graduate Fellowships for Global Change administered by Oak Ridge Institute for Science and Education. Dr. David M. Smith and two anonymous reviewers provided valuable comments. with shrub competition and the accumulation of shadetolerants in the understory (Hannah 1987, Crow 1988, Lorimer et al. 1994). However, experiences with prescribed fire in northeastern oak forests have been mixed (Niering et al. 1970, Nyland et al. 1982, Wendel and Smith 1986, Boemer et al. 1988). An understory shrub of particular management concern in southern New England is mountain laurel. Mountain laurel's high shade-tolerance and aggressive vegetative growth habit make it a stem competitor for oaks on a variety of sites (Chapman 1950). In this study, we examined the results of two controlled bums on the competitive dynamics between red and black oaks and mountain laurel. The hypothesis driving the bums was that forcing the laurel to resprout from the ground surface would "level the playing field," allowing oak seedlings to gain a height advantage and eventually reach sufficient size to allow successful stand regeneration. Study Area and Methods Two sites were studied, both on the Yale-Myers Forest in northeastern Connecticut. Both sites were approximately 8 ac in size. Before the initial treatment, each site had been a single stand, with a dense understory of large mountain laurel, including numerous stems > 2 in. and over 6 ft in height. Prescribed bums were carried out during the spring on