Natural jack pine forest edges are not an earlier warning system than interior forests to detect impacts of atmospheric deposition in the Athabasca Oil Sands Region

The intense industrial development in the Athabasca Oil Sands Region (AOSR) in northern Alberta, Canada, emits gases and particles containing nutrients and trace elements that are deposited to the surrounding landscape (forest, lakes, fens, bogs). Long-term monitoring (at six-year intervals) of jack pine (Pinus banksiana Lamb.) stands within the AOSR, including interior and edge monitoring, aims to detect changes to biological, physical, and chemical indicators in response to this deposition. In this study, we compared edge and interior jack pine sites, assessing their potential roles as early warning systems to detect effects of deposition on jack pine forest in the AOSR, including whether differences might be detected at the edge prior to the interior (i.e., earlier warning system). We quantified foliage chemistry for current-year foliar growth, tree properties (height, diameter at breast height, and live crown ratio), and plant community composition, and the influences of distances from two sources of emissions (upgrader stacks and surface mining) and wind directionality. Understory vegetation was surveyed within established plots. Our results did not show a consistent pattern of edges detecting deposition effects earlier than interior sites. Instead, variables such as proximity to emission sources and wind directionality were more influential in capturing deposition impacts. While atmospheric deposition appears to affect forest sites in the AOSR, monitoring efforts to understand and quantify such effects may be better focused on these broader spatial and temporal factors rather than emphasizing forest edges.