We analyzed the size-class structure of Atlantic white cedar (Chamaecyparis thyoides) swamps established prior to 1930 to determine if there is any evidence that cedar-swamp succession is controlled through replacement by hardwood species such as red maple. The size-class distribution patterns that we observed for cedar in most stands were characteristic of even-aged stands undergoing density-dependent mortality or self-thinning. Hardwoods, including red maple, blackgum, sweetbay, and grey birch, contributed little to total basal area and occurred at low densities. Red maple was the most common hardwood. For this species, large-diameter (≥10 cm) stems, relative density of small (<10 cm) and large (≥10 cm) diameter stems, expressed as a percentage of total small-diameter and large-diameter cedar and maple stems, relative basal area, and canopy cover increased in relation to increasing cedar-stem size and decreasing cedar-stem density. Although these trends suggest that red maple abundance and recruitment may be related to cedar size-class structure, there was no significant difference in the absolute density of < 5 cm diameter maple and cedar stems, and the absolute density of 5-9.9 cm diameter cedar was greater than that of red maple. It is questionable whether red maple or any hardwood species occurred at densities sufficient to allow them to respond quickly to canopy gaps created by the death of overstory trees in the swamps that we studied. Our study indicates that hardwood replacement of cedar in swamps is not a certain outcome of cedar-swamp succession. If Atlantic white cedar is actually replaced by hardwoods as individual trees age and die, the replacement process may take centuries. Even then it may only result in conversion to mixed stands dominated by cedar rather than the complete loss of cedar.
All Science Journal Classification (ASJC) codes
- Ecology, Evolution, Behavior and Systematics
- Plant Science
- Atlantic white cedar
- Chamaecyparis thyoides
- Hardwood recruitment