Long-Term Fertilization Plots in Swale Vegetation on Hog Island, VA 2015 -

Nutrient enrichment plots were installed on Hog Island in 2015 (Moulton, 2017) following a modified Nutrient Network (nutnet.org) protocol. Plots followed a randomized design with three plot treatments (N = nitrogen, P = phosphorus, NP = nitrogen + phosphorus, and C = Control), replicated five times per treatment (N = 20 total experimental units, n = 5 per treatment). Each unit was 3 m2 with 1 m walkways. Units were subdivided into four 1 m2 subplots. N, P, and NP are applied in two applications, 30 days apart, at a rate of 10 g m-2 yr-1. N was added in the form of slow release urea (46-0-0) and P in the form of triple phosphate (0-45-0). Aboveground vegetation was harvested to ground level within a 0.1 x 1 m frame and extrapolated to represent plot level productivity (g m-2). Samples were dried for 72 h at 60 C and weighed (g). Species composition was sampled using areal cover estimation (%) of each species, bare ground, and dead plant material, such that total cover of each plot summed to 100%. Species cover was assessed in 1 m2 sub plots that had not previously been used for destructive sampling.