Effects of vegetated buffers on salt marsh plant composition and groundwater nitrogen uptake

Vegetated shoreline buffers are a best management practice to reduce anthropogenic nitrogen influences on estuarine ecology. This study examined the effects of buffers on (1) groundwater chemistry; (2) the salt marsh border plant community (fertilized and control); and (3) Agropyron pungens response to fertilization. All buffer widths (5 to 15 meters) were somewhat effective at removing groundwater nutrients, with greater concentrations of TDN, NO3--N, NH4 +-N, and DOC found in groundwater wells upslope of the buffer. Although on-site manure storage resulted in 30-fold greater groundwater nitrate concentrations (mean 23 mg/L) at the widest buffer, no differences were found in nitrate uptake rates between buffer widths. The manure storage confounded any buffer width effect and indicated potential nitrogen saturation of the widest buffer. Fertilization increased A. pungens leaf N content (N%; p\u3c0.001); yet the response decreased with buffer width (r2 = 0.91). Buffered plots at two sites had greater species richness (+33%) and species diversity index values (+24%) than unbuffered plots. However, the inclusion of more sites in the study found no significant effect of buffer width, plant diversity, species richness or non-native species. Results suggest groundwater nitrogen interacts with buffers but appears to bypass marshes, pointing to greater importance of buffers in protecting estuaries