| Natural and human disturbance has influenced vegetation structure and composition in eastern North America for millennia. It is essential to understand the effect of disturbance on vegetation in order to properly manage landscape function and structure, This study investigated the response of vegetation and flora of two old-growth forests in southern Illinois to different disturbances. Weaver's Woods, an old-growth upland forest in Union County, experienced windstorm damage in June 1995, This storm damaged approximately 20% of the standing tree basal area and density in the forest, especially on the east-facing slope of the forest which probably received the highest velocity winds. The most dominant tree in the forest, Acer saccharum, was the most heavily damaged species but Carya and Quercus spp. suffered heavy mortality compared to their dominance in the forest. Direct wind damage was most likely to kill a tree. Fungal infection in the oak subgenus Erythrobalanus may have been an important factor in damage to members of this group sustained in the windstorm.; Following windstorm damage, the forest was selectively timber harvested in October 1995. Decreases in tree basal area and density, sapling density, and seedling density and increases in herbaceous species richness and percent cover were the initial responses to this disturbance. The effect of timber harvesting to this forest will likely be the disturbance-mediated succession to a mixed mesophytic forest dominated by Acer saccharum and Fagus grandifolia. This forest has completely changed from a presettlement oak-dominated forest to a mesophyte-dominated forest in approximately 150 years. Non-native species, especially those considered by resource managers to be invasive, have also increased in the forest after these disturbances and will likely be important components in the future forest composition. |
