Description

Oaks have dominated much of the central hardwood forest region for thousands of years. However, there have been geographically widespread reports of its failure to regenerate on many types of sites for many decades. Most studies have approached the oak regeneration problem through the examination of direct effects. There are many indirect ecological effects that have not been well studied. Anecdotal evidence suggests that Native Americans may have used fire for many reasons including control of insect predators and/or pathogens. We chose to examine how fire and/ or thinning may directly influence oak seed production and how those treatments may indirectly impact seed quality by influencing the major species of pre-dispersal oak seed predators (curculionid weevils). Weevils have been known to destroy > 90% of a typical acorn crop. Two mixed-oak forests were selected for study in southeastern Ohio. Within each forest, four stands were selected and randomly assigned a control and a treatment: prescribed fire, thinned, thinned & followed by fire. Thinning treatments were executed during the fall-winter of 2000-2001, followed by controlled burns in the spring of 2001. After the treatments were executed, we selected two species for study: black oak (Quercus velutina) and chestnut oak (Q. prinus). We selected nine trees of each species (144 trees total) within each unit and erected two 0.25 m2 seed traps beneath each tree. Traps were sampled monthly throughout the growing season and for a period after leaf drop (August-December) during 2001 and 2002 to collect seeds. Acorns were destructively sampled and scored as sound, aborted, weevil-depredated, or other. Treatments did not appear to strongly influence seed production or predation rates in the first growing season (floral buds had already initiated and treatment effect was likely minimal). However, during the second season, treatment influence was dramatic. Both oak species responded by producing considerably more seeds in the combined thin-burn units. Any unit receiving a burn also produced a significantly greater number of sound acorns (weevil depredation was lowest in burn units). Long-term studies are continuing to help work out the details of how silvicultural treatments may influence periodic seed-producing (masting) species such as oaks.