Habitat characteristics associated with redroot (Lachnanthes caroliniana) in Nova Scotia

Abstract

Redroot (Lachnanthes caroliniana Lam.) is a member of the Atlantic Coastal Plain Flora (ACPF), a group of taxonomically unrelated plants occupying similar habitat types along the eastern coast of North America. These species are typically poor competitors, and thus thrive in very specific nutrient-poor and high-disturbance environments. Redroot has been listed as “threatened” under the Nova Scotia Endangered Species Act and as a COSEWIC Species of Special Concern, and gaining a greater understanding of its habitat is one of the key conservation goals listed in management plans for the species. Therefore, this study examined the shoreline characteristics, vegetation structure, and interspecific interactions associated with redroot. In the summer of 2015, transects and grids were established at seven lakes in southwestern Nova Scotia, measuring the abundance of redroot and other vegetation, as well as substrate type and elevation. Redroot was found to grow in patches along the first 5 m of shorelines, well within the zone of disturbance from periodic flooding, wave action and ice scour. These disturbances limit the encroachment of woody species which would otherwise outcompete redroot. Redroot abundance increased significantly with decreasing lake area, increasing watershed area to lake area ratio, and increasing amounts of gravel on shorelines. Since flowering is rare in Nova Scotia, and the species is limited to asexual reproduction through rhizome fragmentation, lake connectivity is also thought to be a critical habitat component. The covariation of redroot with other species of ACPF was highly variable between sites, but showed that the direction and magnitude of redroot’s interspecific interactions change depending on the spatial scale at which they are examined. This study confirms habitat trends described in the 2010 COSEWIC status report and complements them through an increased understanding of redroot’s habitat characteristics on the microhabitat scale. These findings can be used to determine suitable regions which could be protected in order to prevent the extirpation of the species.