Distribution of trace and major elements in subarctic ecosystem soils: Sources and influence of vegetation

Inorganic nitrogen and organic matter jointly regulate ectomycorrhizal fungi-mediated iron acquisition

Ectomycorrhizal fungi (EMF) play a crucial role in facilitating plant nutrient uptake from the soil although inorganic nitrogen (N) can potentially diminish this role. However, the effect of inorganic N availability and organic matter on shaping EMF-mediated plant iron (Fe) uptake remains unclear. To explore this, we performed a microcosm study on Pinus taeda roots inoculated with Suillus cothurnatus treated with +/-Fe-coated sand, +/-organic matter, and a gradient of NH4NO3 concentrations. Mycorrhiza formation was most favorable under conditions with organic matter, without inorganic N. Synchrotron X-ray microfluorescence imaging on ectomycorrhizal cross-sections suggested that the effect of inorganic N on mycorrhizal Fe acquisition largely depended on organic matter supply. With organic matter, mycorrhizal Fe concentration was significantly decreased as inorganic N levels increased. Conversely, an opposite trend was observed when organic matter was absent. Spatial distribution analysis showed that Fe, zinc, calcium, and copper predominantly accumulated in the fungal mantle across all conditions, highlighting the mantle's critical role in nutrient accumulation and regulation of nutrient transfer to internal compartments. Our work illustrated that the liberation of soil mineral Fe and the EMF-mediated plant Fe acquisition are jointly regulated by inorganic N and organic matter in the soil.

Climate and Soil Properties Drive the Distribution of Minor and Trace Elements in Forest Soils of the Winter Olympic Core Area

Minor and trace elements in soil play a crucial role in regulating ecological processes that sustain the functionality of forest ecosystems. In this study, we have selected three conifer forests (Pinus sylvestris, Picea asperata, Larix principis-rupprechtii), one broadleaf forest (Betula Platyfilla) and one mixed forest of Betula Platyfilla and Larix principis-rupprechtii in the Winter Olympic core area and determined the pattern of 12 typical elements (B, Fe, V, Cr, Ni, Co, Mn, As, Cu, Zn, Sn and Se) in soils and their main drivers in the three different soil layers (A, B and C horizon) in each soil profile. Our results showed that the concentrations of B, Fe, Cr, Cu, Ni and Sn were mainly enriched in the broadleaf forest and mixed broadleaf-conifer forest zones, and the average concentrations of Co, Mn, V, Zn, As and Se were mainly enriched in coniferous forest zones in contrast. We have observed that the mean concentrations of Fe, Cr, Ni, Zn, As, Sn and Co increase with soil depth in the BP forest. The concentrations of Se and Cu were higher in the A layer than the C layer. The piecewise structural equation modeling (piecewiseSEM) results visualized a direct and negative effect on B, Fe, V, Cr and Ni concentrations due to soil temperature, while the concentrations of Se is mainly influenced by soil temperature and soil properties.

Sources of exposure to lead in Arctic and subarctic regions: a scoping review

Understanding lead exposure pathways is a priority because of its ubiquitous presence in the environment as well as the potential health risks. We aimed to identify potential lead sources and pathways of lead exposure, including long-range transport, and the magnitude of exposure in Arctic and subarctic communities. A scoping review strategy and screening approach was used to search literature from January 2000 to December 2020. A total of 228 academic and grey literature references were synthesised. The majority of these studies (54%) were from Canada. Indigenous people in Arctic and subarctic communities in Canada had higher levels of lead than the rest of Canada. The majority of studies in all Arctic countries reported at least some individuals above the level of concern. Lead levels were influenced by a number of factors including using lead ammunition to harvest traditional food and living in close proximity to mines. Lead levels in water, soil, and sediment were generally low. Literature showed the possibility of long-range transport via migratory birds. Household lead sources included lead-based paint, dust, or tap water. This literature review will help to inform management strategies for communities, researchers, and governments, with the aim of decreasing lead exposure in northern regions.

Altitude governs the air pollution tolerance and heavy metal accumulation in plants

Plant response to changing air pollution is a function of various factors including meteorology, type of pollutants, plant species, soil chemistry, and geography. However, the impact of altitude on plant behavior has received little attention to date. A study was therefore conducted to evaluate the impact of altitude on the air pollution tolerance index (APTI), heavy metal accumulation, and deposition in plant species. The results favor the hypothesis of a definite impact of altitude on biochemical and heavy metal accumulation in plants. While a significant decline (p < 0.05) in the relative water content (RWC), APTI, and heavy metal accumulation with increasing altitude was evident in the studied plant species, the behavior of ascorbic acid, leaf extract pH, chlorophyll content, and the particle heavy metal deposition was erratic and did not display any statistically significant differences. The metal accumulation index was in the following order: Ni > Zn > Cu > Pb > Cd > Co. Similarly, the particle heavy metal deposition on the leaf surface (µg/cm2) displayed significant species variability (p < 0.05) and was in the order: Cu (0.303) > Pb (0.301) > Ni (0.269) > Zn (0.241) > Cd (0.044) > Co (0.025). The accumulated heavy metal and RWC showcased a significant positive correlation with the APTI, suggesting the dominant role of RWC in the plant's tolerance against air pollution in an altitudinal gradient. Future studies on the role of micrometeorological conditions in altering APTI may be fruitful in ascertaining these postulations.

The influence of sea animals on selenium distribution in tundra soils and lake sediments in maritime Antarctica

The biogeochemical behavior of selenium (Se) has been extensively studied in Se-enriched or Se contaminated soils at low and middle latitudes. However, the Se distribution patterns have not been studied in tundra ecosystems of remote Antarctica. Here, the soils/sediments were collected from penguin and seal colonies, their adjacent tundra and lakes, tundra marsh, human-activity areas, normal tundra and the periglacial in maritime Antarctica, and total Se and seven operationally defined Se fractions were analyzed. Overall the regional distribution of Se levels showed high spatial heterogeneity (coefficient of variation, CV = 114%) in tundra soils, with the highest levels in penguin (mean 6.12 ± 2.66 μg g^-1) and seal (mean 2.29 ± 1.43 μg g^-1) colony soils, and the lowest in normal tundra soils and periglacial sediments (<0.5 μg g^-1). The contribution rates of penguins and seals to tundra soil Se levels amounted to 91.7% and 78.0%. The lake sediment Se levels (mean 2.15 ± 0.87 μg g^-1) close to penguin colonies were one order of magnitude higher than those (mean 0.49 ± 0.87 μg g^-1) around normal tundra. Strong positive correlations (p < 0.01) of Se concentrations between lake sediments and adjacent tundra soils, and lower Se: P (<0.001) and S: P (<1) ratios in the lake sediments close to penguin colonies, indicated the infiltration or leaching of penguin guano as the predominant Se source in lake sediment. The Se species in penguin and seal guano were dominated by SeCys₂ (76.6%) and SeMet (73.5%), respectively. The evidence from the predominant proportions of total organic matter-bound Se (Se_om, 67%-70% of total Se) in penguin or seal colony soils further supported penguin or seal guano had a great influence on the distribution patterns of Se fractions in the tundra. This study confirmed that sea animal activities transported substantial amount Se from ocean to land, and significantly altered the biogeochemical cycle of Se in maritime Antarctica.

The Relationships among Microelement Composition of Reindeer Meat (Rangifer tarandus) and Adaptation: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis based on PRISMA statements aimed to summarise the data on the chemical composition of reindeer meat depending on the region of the Rangifer tarandus. We searched SCOPUS, PubMed, Embase, CrossRef, Medline, Cochrane library, eLibrary, and CyberLeninka. A total of 3310 records published between January 1980 and December 2021 were screened. We identified 34 relevant studies conducted in Russia, Norway, the USA, Canada, and Finland for the synthesis. Overall, the consumption of reindeer meat reduces arterial hypertension and atherosclerosis due to many polyunsaturated fatty acids (linoleic, linolenic, arachidonic) and vitamin C, which balances lipid fractions. Venison is an effective means of preventing obesity and adapting to cold due to the content of a complete set of essential trace elements, amino acids, and even L-carnitine. The high content of vitamin C and microelements (iron, zinc, copper) in reindeer meat is likely to increase the body’s antioxidant defence against free radicals and help prevent chronic non-infectious diseases. Thus, venison is an essential component of the adaptation mechanism for the Arctic population.

Changes of Soil Properties along the Altitudinal Gradients in Subarctic Mountain Landscapes of Putorana Plateau, Central Siberia

Changes of soil properties along elevational gradients were studied in a less accessible and explored forest-tundra ecotone in the NW part of Central Siberia. Data on soil physical and chemical properties were collected along three horizontal transects at an elevation of 100–420 m a.s.l., at two localities differing in the slope angle. At each transect, five soil pits were excavated to a depth of 0.3–0.4 m. Soil samples were taken from the depths of 0–0.1 m, 0.1–0.2 m, and 0.2–0.3 m. The results showed a pronounced effect of slope angle on the pattern of soil properties along the elevational gradient. At the locality with a gentle slope, soils exhibited 2.5 times larger thickness of the surface organic layer (SOL), higher pH, and Na+ content, and lower C, N, Ald, and Fed concentration indicating slower pedogenic processes on this site. On the other hand, at the locality with a steeper slope, soil properties were better differentiated between transects situated along elevational gradient especially at the depths of 0.1–0.2 and 0.2–0.3 m. However, a clear positive or negative trend with the altitude was observed only for some soil characteristics, e.g., SOL, C, N, or Ald concentrations on the Lama location.

Mass balance of nine trace elements in two karst catchments in southwest China

High geological background levels of trace elements (TEs) and high population density in the karst areas of southwest China have imposed environmental pressure on the fragile ecosystems in this region. Understanding the mass budget of TEs, especially the toxic ones, is of great importance to sustain future developments. This study investigates the mass balance and fate of nine TEs (cadmium, arsenic, lead, chromium, copper, nickel, zinc, thallium, and antimony) in two karst catchments (Huilong and Chenqi) in southwest China through estimation of their mass budgets in throughfall, open field precipitation, total suspended particulate matter (TSP), litterfall, fertilization, harvested crops, surface runoff, and underground runoff. The estimated net fluxes are positive, indicating a source region, for four elements (Cu, Cr, Ni, and Tl) and negative, indicating a sink region, for five elements (As, Cd, Pb, Sb, and Zn) in both catchments. The net fluxes for the nine elements in Chenqi catchment are within a relatively small range (2.6, 2.0, 1.6, 0.6, -0.05, -0.5, -0.5, -2.9, and -3.3 mg m^-2 yr^-1 for Cu, Ni, Cr, Tl, Cd, Zn, Sb, Pb, and As, respectively), but in Huilong catchment in quite a large range (15.5, 6.0, 1.0, 0.8, -0.3, -0.9, -4.5, -7.5, and -8.7 mg m^-2 yr^-1 for Tl, Cr, Ni, Cu, Cd, Sb, As, Pb, and Zn, respectively). Rainfall (12.3%-66.2%) and litterfall (18.4%-81.3%) are the major input flux pathways, while crops harvest (16%-99%) is the major output flux pathway for the TEs in both catchments, indicating that the fate of TEs is shaped by both natural factors such as precipitation and litterfall and human activities such as fertilization and crop harvesting in these forestland-farmland compound karst catchments. Results from this study suggest that restoring forests from low-yield sloping farmlands will be useful for controlling TEs pollution in these fragile karst regions with high geological background TEs.

Influence of Mining and Vegetation Restoration on Soil Properties in the Eastern Margin of the Qinghai-Tibet Plateau

Mining causes serious destruction of the surface morphology and soil structure of lands, and vegetation restoration on post-mining lands provides an effective way for soil and water conservation. To determine the influence of mining and vegetation restoration on soil properties in the eastern margin of the Qinghai-Tibet Plateau, four land sites, including two vegetation restoration sites (restorated by Elymus nutans and Picea crassifolia, respectively), one non-vegetated mining site and one native grassland site, were selected. Fifty-two topsoil (0–10) samples were collected from these four sites, and then soil properties, trace metals and soil enzyme activities were analyzed. The results showed that there was an increase in soil pH (>8.0) after mining, while vegetation restoration decreased the soil pH compared with native grassland; the soil organic matter and total nitrogen in the site restored with E. nutans increased by 48.8% and 25.17%, respectively, compared with the site restored with P. crassifolia. The soil enzyme activities decreased after mining, and there were no significant increases in urease, phosphatase, β-glucosidase and β-1,4-N-acetylglucosaminidase activities after five years of restoration. In addition, the contents of soil trace metals (cadmium, chromium, mercury, lead and zinc) after mining were lower than the Chinese threshold (GB 15618/2018), but the content of arsenic in non-vegetated soil and P. crassifolia-restored soil exceeded the threshold by 22.61 times and 22.86 times, respectively. Therefore, As-contaminated land areas should be accurately determined and treated in a timely way to prevent arsenic from spreading, and plant species with tolerance to alkaline soil should be selected for vegetation restoration on post-mining lands.

Evolution of Land Cover and Ecosystem Services in the Frame of Pastoral Functional Categories: A Case Study in Swedish Lapland

Ecosystem services (ES) are a key-component for sustainable management of human–environment systems, particularly in polar environments where effects of global changes are stronger. Taking local knowledge into account allows the valuation of ES experienced by stakeholders. It is the case for reindeer herders in Scandinavia, the ungulate being a keystone specie for subarctic socio-ecosystems. We adapt the ecosystem services assessment (ESA) proposed in Finland to the case study of the Gabna herders’ community (Sweden), considering its cultural, geographical, and dynamic specificities. We used Saami ecological categories over the land-use categories of the CORINE Land Cover (CLC). We reassessed ES at the scale of the Gabna community and its seasonal pastures. We studied their evolution over 2000–2018, using CLC maps and Change CLC maps. Integration of Saami ecological categories in the classification of land cover did not substantially change the land cover distributions. However, ES were greater in Saami land use compared to other CLC categories. Cultural services were higher for summer and interseasonal pastures, dedicated to the reindeer reproduction, suggesting interactions between provisioning and cultural ES. Land cover changes are mostly represented by intensive forestry (5% of winter pastures) impeding reindeer grazing activity, while other seasonal pasture landscape composition stayed comparable along time. Consequently, forest activity, and in a lesser extent glacier melting and urbanization are the main drivers of the temporal evolution of ES. In the frame of pastoral landscapes conservation, the use of local terminologies opens perspectives for a holistic approach in environmental science. It raises the importance of local stakeholders as co-researchers in nature conservation studies.