Date of Award
2024
Degree Type
Thesis
Degree Name
Master of Science in Biological and Environmental Sciences (MSBES)
Department
Natural Resources Science
First Advisor
Mark H. Stolt
Abstract
Although soils are essential for sustaining ecosystems, they are often overlooked in routine monitoring efforts during restoration projects. This thesis tries to address the interest in and challenges of measuring and monitoring soil biogeochemical properties and processes to evaluate restoration trajectories. In the first part of this thesis (Chapter 1), I monitored tidal marsh vegetation and soil biogeochemical responses to restoration by thin-layer placement (TLP) of dredged sediments in a greenhouse mesocosm study and a parallel field study at an active restoration site in southern RI. In the greenhouse, aboveground plant biomass in mesocosms treated with +5 cm and +10 cm of dredge materials recovered to control levels within one growing season, perhaps accelerated by the planting of seeds, lower porewater salinity, and elevated porewater nutrients. The effect of dredge treatment on soil redox potential was variable, but there were seasonal trends based on elevation and TLP thickness. In the field, soil profiles in the applied dredged sediments exhibited morphological features that aligned with measurements of redox potential. Dark iron monosulfides (FeS) served as an easily identifiable indicator of strongly reducing conditions. In the second part of this thesis (Chapter 2), I evaluated the efficacy of manganese (Mn)-based Indicator of Reduction In Soil (IRIS) devices to serve as inexpensive, passive sensors of soil redox potential (Eh) in riparian soils. After deploying the devices for 7 days, total Mn removal was a significant predictor of redox potential and on its own could account for 54% of variation in soil Eh measured using platinum (Pt)-tipped electrodes. Incorporating information on Fe precipitates on Mn IRIS, water table proximity, pH, and extractable nitrate increased the variation explained in soil Eh to 71%. A threshold of ≥20% Mn removal from a 2-cm contiguous section of Mn IRIS (when soil temps. were ~15.3°C at 30 cm) could potentially be used for short-term documentation of reducing conditions with respect to the Eh-pH threshold of the Hydric Soil Technical Standard (HSTS) at a particular soil depth with high confidence (>95%). There was also a potential weak relationship between Fe precipitates detected on Mn films and the flux of N2O at the soil surface.
Recommended Citation
Loffredo, Joseph Anthony, "SOIL BIOGEOCHEMISTRY IN RIPARIAN AND RESTORED TIDAL WETLANDS: MONITORING AND METHOD EVALUATION" (2024). Open Access Master's Theses. Paper 2560.
https://digitalcommons.uri.edu/theses/2560
