MICROTOPOGRAPHY AND VEGETATION IN ATLANTIC WHITE CEDAR SWAMPS - THE EFFECTS OF NATURAL DISTURBANCES

Disturbance may alter patterns of microtopography within wetlands, and may consequently alter the relationship between woody plants and micr otopography. I measured microtopographic relief and the relationship o f shrubs and tree seedling distributions to microrelief in undisturbed Atlantic white cedar (Chamaecyparis thyoides (L.) Mills.)) swamps in the New Jersey Pinelands, and in stands disturbed by blowdowns and fir e. In undisturbed stands, hummock-hollow structures, at a scale of abo ut 1 m, are poorly defined and often obscured by smaller scale and lar ger scale patterns of elevation. The swamp floor is, on average, 25 cm above the lowest hollows, but sites greater than or equal to 100 cm h igh occur in undisturbed swamps and within blowdown gaps. Burned sites tend to lack microsites with high elevations, and have less well-deve loped pattern than undisturbed sites. In blowdowns, there is an increa se in the frequency of high-elevation microsites, and more pronounced hummock-hollow patterning. All woody plant species occupy sites of int ermediate elevation, are absent from the lowest 20% of the forest floo r, and display little evidence of habitat differentiation among specie s along the microtopographic gradient. In disturbed sites, the species ' ranges shift in response to disturbance-induced changes in the avail ability of microsites.