Groundwater depth and topography correlate with vegetation structure of an upland peat swamp, Budderoo Plateau, NSW, Australia

Abstract

Swamps, bogs and fens are diverse wetland ecosystems found worldwide. Within each region, different ecological processes and species dominate them, yet water levels and saturation of sediments appear key to the maintenance of vegetation and the ecosystem as a whole. Consequently, understanding how vegetation responds to water levels in these ecosystems is critical to their future management. This paper describes the floristic patterns observed in an upland swamp on the Budderoo Plateau, Southern Highlands, NSW, and relates the distribution of the vegetation communities to groundwater depth, soil type and site attributes. Three distinct vegetation assemblages were identified associated with (1) the main swamp axis, (2) the swamp margin and (3) the adjacent hillslopes. Elevation above the central swamp axis was the variable most strongly related to vegetation structure. Relative changes in elevation create a drainage gradient that allows higher elevation areas (hillslope and swamp marginal zones) to drain more readily than areas in the main swamp axis. Variation in vegetation was also related to median groundwater depth. Finally, soil organic matter content was a contributing factor with the swamp axis and marginal zones mostly having fibric, highly organic soils in contrast to the sandy, loamy soils on the hillslopes.