An aerial view of the shoreline: using remotely piloted aircraft to map vegetation in Netley-Libau Marsh and compare plant assemblages across an exposure gradient

Netley-Libau Marsh has undergone a marked process of degradation during the past century. One of the most noteworthy changes has been a reduction in aquatic vegetation, along with a corresponding increase in open water cover. The shoreline can be understood as a critical zone, where landforms may expand, recede, or remain stable, based on interactions between vegetation and hydrogeomorphic processes. For the first component of my thesis, I developed an accessible method for using a small remotely piloted aircraft (micro-RPA) to map shoreline vegetation in prairie freshwater marshes. This method consists of two manual shoreline surveys at two different altitudes: 120 m and 10 m. The minimal regulations and low cost associated with small RPAs remove many of the barriers to entry for their use in field ecological research. Moreover, this method is likely to be robust from June to October, as it is based primarily on the shape of leaves and stems, rather than colour or spectral signature. This method is also inexpensive, as it can be done using open-source software (WebODM). The second component of my thesis used this method to compare the taxonomic composition of plant assemblages across an exposure gradient. I surveyed 23 km of shoreline between August 17 and August 29, 2020, and produced orthomosaic maps for all shoreline zones. Using data from 150 randomly placed shoreline quadrats, I used a generalized linear model to compare plant community composition along an exposure gradient. Exposure is defined as the total effect of waves on shoreline vegetation. I estimated exposure for each quadrat using an effective fetch model, integrating data on wind directional frequency from 36 compass directions with a spatial raster of the study area within ArcMap. My results indicate that exposure acts as an environmental filter, limiting the growth of Typha spp. in exposed shoreline areas. Typha spp. was less common in exposed locations, and it was also more likely to show visibl