Boundary-line growth patterns to determine disturbance history of remnant longleaf pine (Pinus palustris P. Mill.) in mixed forests of southeastern Virginia

BHUTA, A. A. R. AND L. M. KENNEDY (Department of Geography, Virginia Tech, Blacksburg. VA 24061), C. A. COPENHEAVER (Department of Forestry, Virginia Tech, Blacksburg, VA 24061) P. M. SHERIDAN (Meadowview Biological Research Station, Woodford, VA 22580) AND J. B. CAMPBELL (Department of Geography, Virginia Tech, Blacksburg, VA 24061). Boundary-line growth patterns to determine disturbance history of remnant longleaf pine (Pinus palustris P. Mill.) in mixed forests of southeastern Virginia. J. Torrey Bot. Soc. 135: 516-529. 2008.-Removal of canopy dominant trees in temperate closed-canopy forests due to natural or anthropogenic disturbance may allow for the release of co-dominant and sub-canopy trees into the canopy. Historical growth releases of these trees can be reconstructed from the analysis of their annual rings and compared with historical disturbance events to better understand forest dynamics. We applied boundary-fine growth patterns, a method for the reconstruction of-historical release from disturbance, to annual-ring series of co-dominant longleaf pine in two closed-canopy successional forest sites (Everwoods and Seacock Swamp) the Mid-Atlantic Coastal Plain of southeastern Virginia. The somewhat degraded stands were co-dominated by mixed hardwoods and loblolly pine (Pinus taeda L.) after a long fire-free history. Our study documented recruitment patterns through age-class distribution and reconstructed disturbance events (growth releases) using a modified version of the boundary-line growth method. Ages for all cored individuals at Everwoods (n = 37) ranged from 32-184 years ((x) over bar = 53 years), and at Seacock Swamp (n = 32). from 56-175 years ((x) over bar = 94 years). Longleaf pine has failed to recruit over the past two decades at Everwoods, and over the past half-century at Seacock Swamp, probably due to increased competition and habitat decline in the absence of fire. Boundary-line growth patterns revealed moderate and major release events for longleaf pines at both sites that we linked to anthropogenic disturbances, Such as silvicultural operations (1900s to the 1930s) at both sites and logging by the landowner (early 1950s) at Seacock Swamp. We interpreted extremely low growth rates and dramatic growth-change pulses after disturbance as evidence of heavy suppression atypical for this species, which has been conceptualized as shade-intolerant. Our findings fit with other studies that have suggested that longleaf pine may be less shade-tolerant than formerly thought, at least in some areas or sites. Applications of the boundary-line growth patterns method to old-growth and second-growth longleaf pine forests throughout the southeastern U.S. could help to document possible spatial variability in disturbance histories, responses to releases, and suppression patterns.