CLONAL PROPAGATION, LOCAL DISTURBANCE, AND THE STRUCTURE OF VEGETATION - ERICACEOUS SHRUBS IN THE PINE-BARRENS OF NEW-JERSEY

Ericaceous shrubs dominate the upland plant communities of the New Jersey coastal plain, both in terms of species diversity and abundance of individuals. Niches of these species are most clearly separated in the character and vigor of their responses to disturbance, particularly to fire and tree canopy gaps. Gaylussacia baccata resprouts quickly from buried rhizomes after mild ground fires, and is most flexible in taking advantage of canopy gaps. Its co-dominant, Vaccinium vacillans, shows superior survival after severe fires by virtue of a deeper rhizome system, and resprouts with greater vigor than Gaylussacia at very high fire frequencies. In the sympatric sub-shrub Gaultheria procumbens long, infrequently branching rhizomes distribute ramets over large areas, possibly colonizing small gaps in the shrub and herb canopies. Thus, shrub community structure in this high-disturbance ecosystem is maintained by subtle evolutionary variations on a common theme of clonal propagation.