Response of Planted Eastern White Pine (Pinus strobus L.) to Mechanical Release, Competition, and Drought in the Southern Appalachians
Conversion of low-quality, natural mixed pine hardwood ecosystems, containing a mountain laurel (Kalmia latifolia L.) dominated understory, to more productive eastern white pine (Pinus strobus L.)/mixed-hardwood systems is a common prescription on relatively xeric southern Appalachian forest sites. We examined the effects of mechanical release, interspecific competition, and annual precipitation on growth of planted white pine in four 14-yr-old stands in the southern Appalachians. Two stands were mechanically released at age 6. No significant differences in biomass, basal area, or diameter were,found between treatments for all species combined. Radial increment was significantly less during a drought year for both treatments. Height increment was less sensitive to severe moisture limitation than radial increment. Height and radial increment were compared to distance-dependent and distance-independent measures of competition for the nonreleased stands. Indices based on height and heightldistance explained the greatest amount of variation in both radial and height increment. The influence ofpost-release severe drought may have delayed or diminished the response to release. The competitive influence of understory dominant mountain laurel at stand age 14 appears to be slight compared to the influence of other competing hardwood vegetation.