Construction of a Soil Core Incubation Method for Measuring Nitrogen Removal in Wetlands and an Application in the Elkhorn Slough, CA, USA
Wetlands play a critical role in removing nitrogen pollution from the surrounding landscape by acting as a reactive zone for nitrogen. In anaerobic wetland soil, microorganisms convert nitrogen to inert di-nitrogen gas. Quantifying nitrogen removal in wetland ecosystems remains challenging, especially for wetlands experiencing regular cycles of wetting and drying. I present a laboratory-based soil core incubation method paired with membrane inlet mass spectrometry to measure total nitrogen removal by denitrification and anammox in wetlands. I applied this method to soils taken from a common pickleweed (Salicornia pacifica) dominated salt marsh delineated into wetland positions by degree of tidal inundation. Results suggest that the salt marsh acted as a total nitrogen sink during winter, with the wetland position inundated most often having the greatest nitrogen removal potential. The dense rhizosphere of S. pacifica may have facilitated nitrogen removal by soil microorganisms, even during plant dormancy.