Ecophysiology of atlantic coastal shrubs in response to ocean salt

Abstract

Increased greenhouse gases in Earth’s atmosphere are altering the global climate including changes in air temperature and precipitation patterns that are linked to increasing storms and sealevel rise. In coastal regions, more frequent storm surges and high-water levels can increase marine salt exposure on terrestrial ecosystems through waves and sea spray. There is a need to understand the physiological impacts of marine salt on plant species found in coastal habitats such as barrens and forests. These globally distributed habitats are dominated by woody plants, especially shrubs, and they represent a large portion of the Atlantic coast of Canada. Currently, there is a knowledge gap on how shrub species in these habitats are affected by salt stress. To address this gap, leaf and soil samples were collected from two sites: a rock barren, Chebucto Head, and a forest, Taylor Head, in Nova Scotia. This study examined leaf morphological and physiological traits related to salt tolerance and resource use in two dominant shrub species, the Northern Bayberry (<i>Morella pensylvanica</i>) and the Lowbush Blueberry (<i>Vaccinium angustifolium</i>). Individuals were sampled along a salinity gradient within 200 m of the Atlantic Ocean coastline. Traits included stomatal conductance, specific leaf area, leaf thickness, and leaf dry matter content; leaf nutrients included pH, electrical conductivity, sodium, potassium, nitrate, and calcium contents The soil characteristics and leaf traits were compared in relation to their proximity to the shore using three-way analysis of variance (ANOVA), linear regression, and a principal components analysis, providing more information on the differences between habitat, proximity to the shore, and species in response to ocean salt. This study found that there were differences in salt tolerance within the same species between the different habitats as well as a difference between species. In general, plants in the rock barren experienced higher salt loads and displayed more physiological stress than plants in the forest. The Northern Bayberry was more salt tolerant overall than the Lowbush Blueberry. This research has the potential to be applied in coastal restoration projects to inform which species may be most resilient to saltwater exposure and which habitats may be more vulnerable.