Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Gap dynamics in an Ohio Acer-Fagus forest and speculations on the geography of disturbance.

Abstract

A synthesis based on a review of the literature and original studies in 36 gaps monitored for 12 years in an old-growth forest dominated by Acer saccharum and Fagus grandifolia. Most gaps were formed by single tree falls, although some larger ones were created by the deaths of 2 to 4 canopy trees. Gap closure rates suggest that most saplings need the occurrence of more than one gap to reach the canopy. Newer, small-scale disturbances, because of their geometry, occur at high rates near older disturbances. After gaps form, woody vegetation increases in density for 5-10 yr and then decreases in density. The 4 main species of concern in this study show different patterns of response, with optima as follows: small gaps of all ages for Acer; old gaps of all sizes for Fagus; large young gaps for Fraxinus americana; and large gaps of all ages for Liriodendron tulipifera. The presence, size distribution and species composition of saplings immediately preceding gap formation help determine which species will dominate the gap. In general, the processes occurring in gaps are sufficient to maintain the stand at its current canopy composition. A map of disturbances found in different parts of the eastern deciduous forest (USA) suggests that many forests, particularly those located near the centre of the biome, renew themselves primarily by means of gaps.