Plant community development in the Byron-Bergen Swamp: marl-bed vegetation

Comparative and Gaussian ordination were used to elucidate vegetational pattern on marl beds in the Byron-Bergen Swamp, Genesee County, NY. The ordinations reflected the physiognomic gradient seen in the field. The gradient consisted of algae in marl pools, short sedges on a low moss mat, tall sedges and short shrubs on low hummocks, and tall shrubs and shrubby trees on larger hummocks. Early invasional patterns are related to the formation of a moss–sedge mat which is further modified through the formation of mounds of various dimensions. Marl sites are invaded by species with differing invasional strategies. Included are mat-forming mosses and sedges which reproduce by rhizomes, seed, and (or) layering. These mats are modified through mound formation by cespitose sedges and by mosses such as Drepanocladus revolvens and Campylium stellatum and through organic matter deposition by all of the higher plants. This results in a general increase in peat depth overlying the marl. Differences exist along the physiognomic gradient from short sedges to tall sedges and short shrubs to tall shrubs and shrubby trees. Carbonate carbon decreases, whereas soil organic matter and cation-exchange capacity increase. There are also increases in the depth to and annual fluctuation in the water table. Stratigraphic cores suggest that this physiognomic gradient is a successional gradient as well. Analyses of these cores indicated significant increases of pH and bulk density with depth as well as decreases in organic matter and cation-exchange capacity, indicating an accumulation of organic matter over the surface of the marl. Tree cores indicate that the surrounding Thuja occidentalis forest is encroaching on the marl beds.