Community Succession, Diversity, and Disturbance in the Central Hardwood Forest

Abstract

During the past two decades, ecologists have voiced increasing concern over the problem of maintaining forest ecosystem integrity and sustainability, not only locally and regionally but also nationally. This concern has grown concurrent with the hard database that has provided new information on succession, stability, and biodiversity. In the central hardwood region, the process of forest succession is characterized by natural fragmentation of the oak-hickory forest overstory as canopy gaps are filled with stems of other hardwood species. The loss of oak and hickory over time will have a major impact on the entire ecosystem because they impart a unique structure and function to the forest community. These species are considered keystone species,which Bond (1994) defines as those that should be conserved because they have a disproportionate effect on the persistence of other species. Oak- and hickory-dominated forests not only produce mast but create environmental conditions required by a variety of understory plants as well as mammals, birds, and insects not found in other forest types. The impact of forest habitat loss on mammals is well known, but our understanding of the impact of fragmentation (i.e., caused by agriculture) on neotropical migrant songbird and cowbird populations is relatively recent (Thompson and Fritzell 1990, Terborgh 1992, Thompson et al. 1992, Martin 1993). Less well studied is the impact of succession on shrub and herbaceous plants. These strata produce seed and support a myriad of insect species that constitute the food supply of many songbirds (Martin et al. 1951). A relatively new concept is that many common herbaceous plants depend on the oak-forest environment and are strongly negatively impacted by succession to shade-tolerant species.