Seventeen original-style SET benchmark posts were permanently installed at 7 Spartina alterniflora-dominated saltmarsh sites within North Inlet. Each SET sampling plot consists of a permanently installed post and a removable arm. The arm has a vertical and a horizontal component. The vertical component fits into the SET benchmark post; the horizontal component reaches out over the experimental subplot and has a square plate at the end through which 9 pins are lowered. Sampling at 3 SET plots has been discontinued due to loss of the SET benchmark post from creekbank erosion.
To measure elevations, the SET arm is locked in place over each subplot, is leveled, and the 9 fiberglass pins are lowered to touch the sediment surface and held in place with a clip. Pin heights are measured from the top of the nut on the plate to the top of the pin, and read into a digital recorder. The recordings are transcribed into one master SET pin height data set. Elevations of the benchmark posts have been surveyed relative to NAVD88 at varying times using RTK. The elevation of the marsh surface can be calculated using the surveyed elevation, the pin height data, and the geometry of the SET. Initial marsh surface elevations are included in this data package.
At 6 sites (Oyster Landing, Debidue Creek, Old Man Creek, Sixty Bass Creek, Bly Creek, and South Town Creek), sampling occurs annually. At the Goat Island site (GI), sampling occurs approximately monthly. Additionally, at GI, triplicate posts were installed in the high marsh (HM) and low marsh (LM), and each of the 6 GI plots, is divided into 3 NP-fertilized subplots and 3 unfertilized control plots. Plots in the HM were fertilized monthly from May 1996 to Aug 2004 and again from May 2017 until present, and in the LM from Jan 2001 until Aug 2004, by burying an aliquot of the appropriate amount of fertilizer in several spots within each plot.