Dune slack wetlands vegetation monitoring, Cape Cod National Seashore: Floristic changes between 2004 and 2014

Smith, Stephen

At the northern tip of Cape Cod, spanning approximately 1,800 hectares (ha) within the Cape Cod National Seashore (CACO), lies a vast system of dunes and inter-dunal wetlands known as the Province Lands. This part of the Cape Cod peninsula began forming ca. 18,000 years ago as longshore currents transported eroded materials from Atlantic-side beaches in a northward direction. Concurrently, wind carried sand grains inland and the landform gradually assumed its characteristic shape. Although once covered by mature forest, European settlers engaged in clear cutting and grazing practices that by the early 1800s had eliminated much of this community and destabilized the ground surface. The legacy of these activities is a sparsely vegetated landscape of shifting dunes and interdunal depressions. The latter are formed by the scouring action of wind, which can lower ground elevations to the point that they intersect the groundwater table for part of the year. These seasonally flooded wetlands, also known as dune slacks, develop distinctive hydrophytic plant communities and are virtual oases of biodiversity in an otherwise desert-like environment. Dune slacks are one of the last refuges on the outer Cape for species such as the insectivorous sundews (Drosera spp.) and orchids (Calapogon tuberosus, Pogonia ophioglossoides). From a wildlife perspective, they are critical habitat for the reproduction and survival of numerous invetebrates and amphibians such as the spadefoot (Scaphiopus holbrookii) and Fowler’s toad (Bufo fowleri). For larger mammals and birds, dune slacks are an important source of drinking water, succulent forage, and prey. Finally, these areas are very popular with visitors, as they possess aesthetic qualities that are a valued component of the Province Lands scenery.” In total, 524 dune slack wetlands have been mapped and inventoried within CACO. The wetlands occur throughout the entire extent of the Provincetown and Truro dunes (Figure 1). Although signification mapping and inventory work was completed in 2003/2004 and 2009, the main objectives of the 2014 monitoring efforts were to re-survey 26 sites that were originally selected in 2003. This resurvey represents the evaluation of an intensive long-term vegetation monitoring campaign designed to characterize vegetation change on Intensive Survey (IS) sites. Additionally, a subset of 40 randomly-selected wetlands was re-surveyed for vegetation (no transects) cover within the entire wetland complex.

Dune slack wetlands vegetation monitoring, Cape Cod National Seashore: Floristic changes between 2004 and 2014

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