Factors influencing soil properties and associated ecosystem functions of created marsh habitats in the Fraser River estuary

Globally, many estuarine habitats have been damaged, degraded, or destroyed due to anthropogenic activities. The Fraser River Estuary (FRE) in southern British Columbia, Canada, has not been immune to such habitat loss, having faced upwards of 90% wetland loss since European contact. Documented habitat loss coupled with continued anthropogenic modifications to the FRE has led to the use of tidal marsh creation as a tool to mitigate existing and future losses. Previous research assessing ecosystem functionality at created marsh sites has shown that many sites fail to meet project goals, especially with regard to aboveground vegetation dynamics. However, few studies consider how soil properties and dynamics may be affected in created marshes or assess the factors that may affect the resiliency of these systems. My research aims to address these knowledge gaps within estuary marshes located in the FRE. Specifically, I experimentally evaluated the impact of herbivory from introduced Canada Goose populations (Branta canadensis; CAGO) on created tidal marsh soil properties and aboveground vegetation over a spring-summer growing season. I found that created tidal marsh habitat exhibited less aboveground biomass, poorer nutrient availability, less soil organic matter, and higher bulk density than a natural marsh reference site. Additionally, I found that CAGO herbivory negatively impacted aboveground biomass at the created marsh habitat, but did not appear to have any direct effects on soil properties. These findings suggest that created and natural marshes vary significantly in their properties and functions, which may have significant implications for ongoing management approaches. Additionally, my research supports previous work showing that herbivory from resident CAGO directly and negatively impacts aboveground biomass within the FRE, further highlighting the need for the adoption of a regional CAGO management plan to effectively address this conservation challenge.