Elevated atmospheric nitrogen (N) deposition can alter forest biogeochemistry leading to adverse impacts on terrestrial ecosystems. Experimental studies often apply N to the forest understorey at greatly elevated loads, bypassing important canopy interactions. Using a narrow N deposition gradient (0, 5, 10, 15, 20, and 25 kg N·ha−1·year−1), we measured changes in jack pine (Pinus banksiana Lamb.) forest biogeochemistry in the bituminous sands region of northern Alberta, Canada after 5 years of above-canopy N additions. The canopy intercepted approximately 46% of applied N across all treatments, but during the final year, N interception was reduced to 7% in the highest treatment. Nitrogen concentrations in nonvascular organisms increased with treatment and N was also immobilized in decomposing litter in the highest treatment. Otherwise, vascular plant biomass, foliar chemistry, and soil processes exhibited no relationship with treatment over 5 years. This work suggests that jack pine forests in the region have a high capacity to immobilize N inputs over the short-term (5 years), which restricts other biogeochemical responses traditionally associated with elevated N deposition.

Peatlands dominate the landscape of the Hudson Bay Lowlands in Ontario, Canada. Recently, mineral deposits of chromium (Cr), nickel (Ni), and copper (Cu) were discovered in the region and anticipated future industrial mining operations have the potential to impact the environment. Lichens and bryophytes are considered excellent biomonitors and indicators of deposition, deriving their nutrients directly from the atmosphere. Trace element concentrations in lichens and bryophytes have not been reported in the Hudson Bay Lowlands. Here, we seek to determine the baseline trace element concentrations of six non-vascular species (Evernia mesomorpha, Bryoria spp., Cladonia stellaris, Cladonia stygia, Sphagnum fuscum, and Sphagnum capillifolium) common to the region, explore linear relationships of trace elements with iron (Fe) as a signature of particulates with geogenic origin, and calculate trace element enrichment factors. Thalli, foliage, and peat (0–30 cm) were collected from 55 locations between 2013 and 2018 and analyzed for trace elements. Thalli and foliar concentrations are among the lowest reported in the broader literature and differ substantially from peat. Fe concentrations were significantly correlated (Pearson’s r ≥ 0.8) with aluminum (Al), titanium (Ti), and vanadium (V) in all six species. Enrichment factors show some anthropogenic deposition effects non-vascular organism chemistry. Most trace element concentrations in lichens and bryophytes are indicative of long-range atmospheric transport of dust, but some is attributed to industry, with only minimal inclusions from the local area. Epiphytic lichens are well suited for ongoing atmospheric biomonitoring as industrialization commences.

Poly- and perfluoroalkyl substances (PFAS) have become ubiquitous contaminants in the environment. Contamination of the terrestrial ecosystem can occur from the release of aqueous film forming foams (AFFF) used in firefighting operations. Following soil contamination with AFFF, studies report root uptake and translocation of PFAS to other plant organs, typically favouring the short chain moiety. This body of experimental work often focuses on edible organs and generally lacks entire PFAS budgets. Here, we calculate short chain (<= 6 carbons) and long chain (>= 6 or >= 7 carbons) PFAS concentrations and respective budgets for terrestrial multimedia mesocosms (plants, soil and lysimeter) of three common agricultural plants (tomato, lettuce and beet) following irrigation with low level PFAS (<1 mu g L-1) contaminated river water (short chain: 167 ng L-1; long chain 526 ng L-1). Total net recoveries were strong, ranging between 91% and 118% of added PFAS across all media. While soil was the largest receptor of PFAS in general (-70% and 115%), there was considerable mobility to various media, including vegetation (-3% and 20%) and leachate (-1%). Translocation of short chain PFAS to tomato flowers resulted with biomagnified concentrations (maximus >4000 ng g(-1)) and accounted for 1.4% of PFAS additions. While smaller tomato fruits had higher concentrations of short chain PFAS, larger fruit had more total PFAS mass. This work provides a detailed description of the fate of short and long chain PFAS when added to relatively uncontaminated terrestrial agricultural systems. We show low-level PFAS concentrations from real-world irrigation sources can affect various receptors across the multimedia landscape. This is most evident in tomato flowers and fruit where biomagnification and high total masses of short chain PFAS occurred which could have implications for pollinators and consumption, respectively. Crown Copyright (C) 2021 Published by Elsevier Ltd. All rights reserved.

The Athabasca Oil Sands in Alberta, Canada, is one of the largest point sources of nitrogen oxides in Canada. There are concerns that elevated nitrogen (N) deposition will adversely impact forest ecosystems located downwind of emission sources. The role of the forest floor in regulating these potential eutrophication effects was investigated following a 5-year enrichment study in which N was applied as NH4NO3 above the canopy of a jack pine (Pinus banksiana Lamb) stand in northern Alberta close to Fort McMurray at rates ranging from 5 to 25 kg N ha−1 y−1 in addition to background deposition of approximately 2 kg N ha−1 y−1. Chemical analysis of lichen mats revealed that the N concentration in the apical (upper) lichen tissue and necrotic tissue increased with treatment. When expressed as a N pool, the fibric–humic material held the largest quantity of N across all treatments due to its relatively large mass (172–214 kg N ha−1), but there was no significant treatment effect. Soil net N mineralization and net nitrification rates did not differ among N treatments after five years of application. A 15N tracer applied to the forest floor showed that N is initially absorbed by the apical lichen (16.6% recovery), FH material (29.4% recovery), and the foliage of the vascular plant Vaccinium myrtilloides (31.7% recovery) in particular. After 2 years, the FH 15N pool size was elevated and all other measured pools were depleted, indicating a slow transfer of N to the FH material. Applied 15N was not detectable in mineral soil. The microbial functional gene ammonia monooxygenase (amoA) responsible for catalyzing the first step in nitrification was undetectable using PCR screening of mineral soil microbial communities in all treatments, and broad fungal/bacterial qPCR assays revealed a weak treatment effect on fungal: bacterial ratios in mineral soil with decreasing relative fungal abundance under higher N deposition. This work suggests that terricolous lichen mats, which form the majority of ground cover in upland jack pine systems, have a large capacity to effectively retain elevated N deposition in soil humus.

The Athabasca Oil Sands in Alberta, Canada, is one of the largest point sources emitters of NOx and SO2 in Canada, and there have been widespread concerns over potential ecosystem acidification owing to the acid sensitivity of the base-poor sandy soils in the region. In this study we compared soil and vegetation properties at a jack pine (Pinus banksiana Lamb) forest adjacent to one of the largest mines in the region with a jack pine stand located approximately 15 km from the mine. At the site closest to the mine, throughfall deposition of SO4-S and DIN (NO3 + NH4) exceeds 30 and 20 kg ha−1 y−1, respectively, compared with less than 9 kg ha−1 y−1 for SO4-S and less than 2 kg ha−1 y−1 DIN at the distant site. However, on an equivalence basis, base cation (Ca + Mg + Na) deposition in throughfall at both sites exceeded the combined S and N deposition. Total S and N as well as Ca and Mg concentrations in epiphytic lichens and tree bark were significantly higher at the site adjacent to the mine, reflecting the higher acidic and base cation throughfall deposition. The forest floor at the stand close to the mine had a significantly higher pH, exchangeable Ca, Mg, K and total S concentrations compared with the distant site. The chemistry of deeper mineral soil horizons was more consistent between the two sites. Foliar concentrations of S, Ca, Mg, Fe and Al in jack pine, Vaccinium vitis-idaea, Vaccinium myrtilloides and Arctostaphylos uva-ursi were also higher at the site close to the mine, but these differences were not always significant. Coincidental with differences in atmospheric deposition, herbaceous cover and biomass, especially A. uva-ursi, was significantly higher, and terricolous lichen cover was several fold lower at the site closest to the mine. This work indicates that despite high S and N emissions from oil sands activities, forest fertilization and alkalization may be of greater concern than acidification owing to large dust emissions from the mines and the Acid Deposition Management Framework for the region should be modified accordingly.