Sustaining oak ecosystems in the central hardwood region: lessons from the past--continuing the history of disturbance

摘要

Oak savannas, woodlands and forests were dominant ecosystems throughout the central hardwood Region (CHR) before European settlement. Today, only 0.02 percent of the original oak savannas present at the time of European settlement remain, and bottomland hardwood forests have been reduced by 70 to 95 percent depending on the watershed (Nuzzo 1986, Sharitz and Mitsch 1993). This deforestation resulted largely from agriculture development. Upland oak/hickory forests are still the major (54 million acres) forest type in the CHR. However, current disturbance regimes are driving forest succession to more shade tolerant species such as the maples and pioneer species such as yellow-poplar, especially on the more productive lands (site index = >60 feet, base age = 50) (Lorimer 1993). However, increased competition from shade tolerant trees and shrubs reduces oak regeneration potential even on drier sites. The inability of oak reproduction to compete and recruit into the overstory is the fundamental causeof oak sustainability problems in forested situations.