Old Field Succession
Old field succession has been studied primarily in the eastern United States. The abandonment of agricultural fields in this region coincided with the flowering of ecology as a discipline. The process of old field succession starts on an agricultural field or some other form of anthropogenically denuded area. Propagules, rhizomes, and roots of most native species with the exception of agricultural weeds have largely been eliminated.
After abandonment the field is quickly colonized by the rapid dispersal into the site by a number of extremely prolific annuals and some agricultural weed species that have maintained a propagule or seed bank on site.
Easter red cedar (Juniperus virginiana) is typical of the early arborescent colonists of old fields. It exhibits rapid dispersal, early maturity, and produces numerous small seeds, but exhibits low efficiency under low light conditions.
After 15-20 years the cedars and ash have begun to compete with the grasses and herbs that previously dominated the old field.
At age 36 canopy closure has occurred. Oaks are beginning to compete with the cedars for light and nutrients. The grasses and herbs that dominated the early years of old field succession have largely been eliminated. Lesser densities of poison ivy and virginia creeper now occurr in the shaded understory. Remaining grasses and composites invest less energy in reproduction and more energy in competition for light and nutrients.
