FIRE HISTORY AND VEGETATION DYNAMICS OF A CHAMAECYPARIS-THYOIDES WETLAND ON CAPE-COD, MASSACHUSETTS

1. Fire history and vegetation change over the past millennium and mod ern successional trends in a Chamaecyparis thyoides (Atlantic white ce dar) wetland on Cape Cod, Massachusetts were investigated using fine-r esolution pollen analysis and stand age-structure analyses. 2. Before European settlement (c. 1650 AD) low cedar pollen percentages correspo nd with abundant charcoal, whereas cedar dominates when charcoal value s are low. Five fires occurred at 100-200-year intervals in prehistori c time. Since settlement, fires have been rare and cedar dominates the pollen profile. 3. During the past two centuries timber cutting has b ecome a significant factor in the vegetation dynamics of this system. In the nineteenth century intensive cutting resulted in the establishm ent of cedar. During the first half of the twentieth century, light ti mber thinnings favoured Acer rubrum (red maple) regeneration. In the p ast few decades, neither cedar nor its principal associate, red maple, have regenerated beneath the undisturbed cedar overstorey. 4. Our res ults indicate that, at this site, vegetation composition and successio nal trends have largely been controlled by allogenic factors in both p re- and post-settlement times. Vegetation changes resulting from autog enic factors are not evident during the 1000-year study period. 5. Age -structure analyses of modern stands in combination with fine-resoluti on pollen analyses are useful in comparing current vegetation dynamics with those of earlier times. In the 600-800 years before establishmen t of the current mature stand, cedar did not persist for more than 100 -200 years without stand-regenerating fires. Thus the survival of the current stand much beyond its present age of c. 150 years would be aty pical compared to the centuries prior to settlement. The present lack of cedar regeneration suggests that a management policy excluding dist urbance would eventually lead to a decline in the importance of cedar. 6. Our results suggest that an understanding of processes that influe nce community composition and structure over long periods of time may indicate conservation objectives and management guidelines different f rom those directed at the preservation of communities that, at a given point in time. appear to be unique on the landscape.