Stand Dynamics Following Gap Scale Exogenous Disturbance in a Single Cohort Mixed Species Stand in Morgan County, Tennessee

Southeastern mixed species stands vary greatly in terms of composition, structure, and disturbance. Limited research has been conducted on the successional processes occurring after small scale exogenous disturbance within second growth mixed species forests of the southeast. During the years of 1998-2002, southern pine beetle (Dendroctonus frontalis Zimmerman) populations reached epidemic proportions, affecting forests throughout the southeastern United States. The southern pine beetle outbreak resulted in the mortality of nearly all overstory Pinus strobus on the study area. Due to the low basal area and relatively even distribution of eastern white pine on the study area, numerous single stem canopy gaps were formed. Management activities conducted in 2003 following this disturbance involved the salvage cutting of easily accessible overstory Pinus strobus stems. The goal of this study is to investigate stand dynamics following gap scale exogenous disturbance within a secondary forest stand during the understory re-initiation stage of development. Differences in composition, structure, and growth under single stem canopy gaps were analyzed under two scenarios, using analysis of variance, where the stem was either removed or left as a standing snag. There were no significant differences in composition and structure of large diameter residual stems within upper canopy strata. Advance reproduction was recruited as a new cohort following the disturbance. Where the stem was removed, the recruitment consisted of eastern white pine (Pinus strobus), yellow-poplar (Liriodendron tulipifera), and red maple (Acer rubrum). Where the stem was left as a standing snag, the advance reproduction recruited as a new cohort was comprised of red maple, American beech (Fagus grandifolia), and oaks (Quercus spp.). The removal of the gap maker provides a pathway to recruit suppressed stems into larger diameter and crown classes. Salvage cutting fostered the growth of stems from intermediate or suppressed crown classes whereas leaving a standing snag favored the growth of adjacent stems within dominant or codominant crown classes.