Hydrologic Connectivity to Streams Increases Nitrogen and Phosphorus Inputs and Cycling in Soils of Created and Natural Floodplain Wetlands

Abstract

Greater connectivity to stream surface water may result in greater inputs of allochthonous nutrients that could stimulate internal nitrogen (N) and phosphorus (P) cycling in natural, restored, and created riparian wetlands. This study investigated the effects of hydrologic connectivity to stream water on soil nutrient fluxes in plots ( = 20) located among four created and two natural freshwater wetlands of varying hydrology in the Piedmont physiographic province of Virginia. Surface water was slightly deeper; hydrologic inputs of sediment, sediment-N, and ammonium were greater; and soil net ammonification, N mineralization, and N turnover were greater in plots with stream water classified as their primary water source compared with plots with precipitation or groundwater as their primary water source. Soil water-filled pore space, inputs of nitrate, and soil net nitrification, P mineralization, and denitrification enzyme activity (DEA) were similar among plots. Soil ammonification, N mineralization, and N turnover rates increased with the loading rate of ammonium to the soil surface. Phosphorus mineralization and ammonification also increased with sedimentation and sediment-N loading rate. Nitrification flux and DEA were positively associated in these wetlands. In conclusion, hydrologic connectivity to stream water increased allochthonous inputs that stimulated soil N and P cycling and that likely led to greater retention of sediment and nutrients in created and natural wetlands. Our findings suggest that wetland creation and restoration projects should be designed to allow connectivity with stream water if the goal is to optimize the function of water quality improvement in a watershed.

Contemporary Deposition and Long-Term Accumulation of Sediment and Nutrients by Tidal Freshwater Forested Wetlands Impacted by Sea Level Rise

“…Nutrient inputs from sedimentation are critical to wetland ecosystem dynamics and biogeochemistry (Johnston 1991;Noe and Hupp 2009;Wolf et al 2013). Sediment deposition can be the dominant source of N and P inputs compared to dissolved inorganic nutrient loading to the soil surface; sediment deposition is 90 and 66 % of total nitrogen (N) and phosphorus (P) inputs, respectively, to TFFW and oligohaline wetlands in the southeastern USA this study).…”

“…Long-term N removal by sediment accumulation in freshwater, brackish, and salt marshes (downstream of TFFW) represents from 13 to 32 % of the watershed load of three estuaries (Loomis and Craft 2010). Furthermore, varying inputs of N and P from deposition could change the rates of biogeochemical cycling in TFFW (Hopkinson 1992;Wolf et al 2013). Finally, salinification increases soil N and P mineralization in tidal freshwater wetlands, which could stimulate primary productivity or export nutrients to downriver estuaries (Weston et al 2006;Jun et al 2013;Ardón et al 2013;Noe et al 2013;Gao et al 2014).…”

Nutrient Retention in Restored Streams and Rivers: A Global Review and Synthesis

“…Alternative methods used for evaluating stream and river restoration included: sediment dynamics, plant dynamics, nitrification, stable isotope ratios, dissimilatory nitrate reduction to ammonia (DNRA), anammox, microbial biomass nitrogen (MBN) and potentially mineralizable nitrogen (PMN). Sediment dynamics ranged from measuring concentrations [61] to N sedimentation and turnover rates [62], and experimentally evaluating changes like N release from sediments deposited on the floodplain [63]. Plant dynamics included measurements of biomass, plant uptake, and nutrient utilization efficiency [64,65].…”

EcoScience + Art initiative: Designing a New Paradigm for College Education, Scholarship, and Service

“…When joining GMU in 2003, I launched a long-term study of functional development and design elements for created mitigation wetlands, specifically collaborating with a local company specializing in wetland mitigation. The work includes microtopography and hydrologic connectivity as design elements that can be created and managed to enhance the development of ecological functions in wetlands to restore ecosystem services (Moser et al, 2007(Moser et al, , 2009Wolf et al, 2013), which also involved in working with people from a variety of disciplines, including engineering (e.g., hydrology), landscape architecture, botany, soil sciences, film and media, communication, and/or arts. I have also been interested and practiced in combining teaching and research activities as a college scholar and teacher.…”