Mapping plant communities and understanding the landscape structure of coastal barrens using an unmanned aerial vehicle

Abstract

Coastal barrens are landscape mosaics - patchworks of plant communities that exist in harsh environmental conditions created by land-sea interactions and shallow soils. Many rare and uncommon species inhabit these ecosystems, making them a high priority for conservation. In Nova Scotia, coastal barrens are abundant along the coastline of the Halifax region. Little is known of the spatial distributions of plant communities that inhabit them and their overall landscape structure. The purpose of this study was to investigate the use of a UAV to map plant communities and to quantify the landscape structure of coastal barrens. First, high-resolution multispectral UAV imagery was evaluated to discriminate plant communities from three classification levels across three coastal barrens sites in Halifax, Nova Scotia: Chebucto Head, Prospect Bay, and Polly’s Cove. All plant communities were discriminated with 95% confidence except for one pair, showing that plant communities in the coastal barrens could be discriminated with a high level of confidence using UAV imagery. Next, UAV imagery was classified to produce detailed maps of plant communities for the three coastal barrens landscapes. Environmental factors, such as elevation, stream networks and wind exposure were also mapped to help understand landscape structure. Sites were dominated by shrublands and dwarf heath; however, many other types of communities co-occurred on these landscapes, including bogs, salt marshes, and tree islands. The most common plant community across the three sites was Gaylussacia baccata shrubland. Plant community patches varied in size, shape, abundance, and spatial distribution from one plant community type to another and in many cases from one site to another. Landscape patterns were driven by various combinations of environmental factors, including slope position, proximity to stream networks, elevation, and distance to coastline. Overall differences in landscape structure could be mostly explained by the degree of topographic heterogeneity of each landscape. UAVs are an excellent tool for mapping plant communities and quantifying landscape structure and this information is critical for informing land managers, conservation planners, and policy makers.