Blowdown Dynamics in Oak-Hickory Forests of the Missouri Ozarks

REBERTUS, ALAN J. AND ALBERT J. MEIER (School of Natural Resources, University of Missouri, Columbia, MO 65211) Blowdown Dynamics in Oak-Hickory Forests of the Missouri Ozarks. J Torrey Bot. Soc. 128:362369. 2001.-Several studies in the literature have relied on public land survey (PLS) notes from the 1800's to reconstruct historical blowdown rates in eastern deciduous-conifer forests, but assessment of contemporary blowdown regimes in the region has not received much attention. We used an approach similar to the PLS method, and sampled 105 km of transect to determine whether oak (Quercus) dieback led to extensive secondary blowdown of patches 2500 m2 in 50to 100-year-old oak-hickory forests in the Missouri Ozarks. Few studies of wind disturbance have focused on even-aged, second-growth stands, even though such stands predominate in eastern deciduous forests. From 1986-1996, blowdowns 2500 m2 disturbed 1.42% of the landscape; for patches 0.05-2.5 ha, only 0.63% of the landscape was disturbed. Although extensive oak dieback occurred in the 1980's and 90's, most of the decline was distributed diffusely through stands, and coarser patches of windthrow were uncommon. Shade-intolerant scarlet oaks (Quercus coccinea Muenchh.) dominated the pre-disturbance canopy and were the dominant treefalls, but two-thirds of new regeneration in blowdowns consisted of white oaks (Quercus alba L.), hickories (Carya spp. L.), and flowering dogwoods (Cornus florida L.). Blowdowns appeared to leave the understory intact, favoring future dominance by species with intermediate shade tolerance.