ABSTRACT Canada’s mountain ecosystems are changing as a result of climate change and a host of natural and anthropogenic disturbances. Understanding the kinds, rates, and causes for those changes is important for informed ecosystem management. To assess changes in the vegetation of Jasper National Park (JNP), we documented changes in plant community composition by resampling 41 ecological land classification (ELC) plots first assessed in the 1970s. In 2023, we documented the presence and percent cover of vascular, hepatic, moss, and lichen species within each plot and compared those data to the 1970s data. Within each plot, we determined the change in cover for each taxon. The communities have become more species rich since the 1970s and community type diversity has increased. Despite rates of species turnover that exceed 50%, plant diversity shows no signs of decline. Multidecadal succession, perhaps influenced by climatic change and human disturbances, is altering the vegetation composition independent of wildfire and mountain pine beetle. Ecologically important species that decreased over time included Pinus contorta, Rosa acicularis, Vaccinium cespitosum, V. scoparium, and V. vitis-idaea. Important increasers included Picea glauca, Pseudotsuga menziesii, and Hylocomium splendens. Younger and drier sites changed more than did older and moister sites.

Is moss-associated nitrogen fixation controlled by the same factors across shoots, species and sites?

Ground vegetation is a major component of forest ecosystems. Its composition, diversity, and structure are important factors determining the biological diversity of forest ecosystems. Since the ecosystem is a very complex system, the impact of climate change, meteorological extremes or air pollution is dispersed through all ecosystem components. A change in one parameter inevitably affects the others. The strongest composition and coverage fluctuations within herbs and moss layers are mainly determined by the composition and structure of habitat edificators – trees. The changes of separate understory species and whole-layer coverage are related to the conditions of the tree canopy and the succession stage of the stand. Climate change, meteorological extremes and chemical pollution-induced risks, firstly strike the homeostasis of dominant trees, when some of the trees die off, the microclimatic characteristics of the stands change drastically, inducing significant fluctuations within lower layers of vegetation.Yet long-term data analysis indicates that meteorology-related ground-level vegetation reactions also manifest, so climate change-induced effects on ground vegetation can indirectly affect the homeostasis of the whole stand. Long-term (1993-2024) forest understory vegetation monitoring data collected under the ICP IM program in 3 different old-growth forest stands in Lithuania were analyzed. The effect of main meteorological parameters on the dominant herbs and mosses coverage was assessed. Norway spruce-dominated (Z) and Scots pine-dominated (AI) stands were located on relatively dry, oligotrophic haplic arenosols. The third (A1) stand, is pretty equally covered with Norway spruce, Scots pine and Silver birch, and in contrast to AI and Z located on wet, water-saturated, meso-eutrophic, terric histosol with groundwater connection at about 50 cm. In the A2 polygon after the death of part of the dominant trees in 2010, a dense spruce undergrowth is formed, displacing the vegetation of the lower layers of herbs and moses. In other polygons (A1, ZI), in contrast to the AII polygon, no big-scale die-off within the tree layer was registered, and the ground vegetation communities of herbs and mosses remained pretty constant throughout the investigation period. In Spruce-dominated forest stand (Z), while the majority of dominant understory species demonstrated a positive correlation with an increase in annual rainfall, soil and air temperatures, Maianthemum bifolium and Pleurozium schreberi demonstrate quite an opposite reaction. Indicating its highest vulnerability. An absolute herb-level dominant Vaccinium myrtillus coverage is positively related to the general coverage of the moss layer, especially Plagomnium affine and Hylocomium splendens. Yet coverage of an absolute moss layer dominant Hylocomium splendens significantly negatively correlated with the most sensitive of dominant herb species Maianthemum bifolium. In the Pine-dominated A1 stand, likewise in the Z stand only Pleurozium schreberi and Goodyera repens demonstrate negative species coverage correlation with an increase in annual precipitation and monthly temperature, in opposition to the rest dominant species. Interestingly, an absolute herb layer dominant Vaccinium myrtillus coverage has a significantly positive correlation with rainfall during June, but a negative correlation with air humidity in May. Also registered a rising soil temperature positive effect for Melampyrum pratense and Ptilium crista-castrensis coverage. In contrast to Z stand, Vaccinium myrtillus coverage was more related to Ptilium crista-castrensis, not Hylocomium splendens coverage. Mixed A2 forest, located on organic-rich, water-saturated peat soil, currently is distinguished by thick spruce undergrowth, and herbs and moss layer in many sample plots are poor. In contrast to Z and A1 polygons, the dominant of the remained species indicates quite an opposite pattern compared with previous stands. The rise in annual rainfall also soil and air temperature have a negative correlation with the coverage of the herbs layer. The moss layer coverage has no or low correlation to changes in annual rainfall, yet a significant positive correlation with air humidity was indicated. Overall, the analysis allows us to indicate some species-specific patterns, their stand structure, composition and meteorology-related peculiarities.

Purpose: To assess the level of environmental pollution by radionuclides and heavy metals using the example of studying atmospheric precipitation near the municipal solid waste landfill in Yakutsk. Material and methods: Biomonitor mosses (Hylocomium splendens, Pleurozium Schreberi, and Brachythecium salebrosum), lichens, and soil were used as research samples, which were sampled in the territory surrounding the municipal waste landfill on the 9th km of the Vilyuysky tract in Yakutsk within a radius of 51 km. The PlasmaQuant PQ 9000 Elite optical emission spectrometry (Analytik Jena, Germany) and the direct mercury analyzer DMA-80 evo Milestone were used as methods for studying the presence and concentration of heavy metals. The radionuclide composition of the samples was studied using gamma-ray spectrometry on an ORTEC semiconductor gammaray spectrometer with a GEM-40 highpurity germanium detector and Maestro32 software. Results: According to the results of the study, in the territory within 51 km along the Vilyuysky tract from the landfill, the following microelementes were found in samples of biomonitor mosses: P, S, Al, Fe, Mn, Ba, Sr, Zn, Cu, Pb, Cr, V, Ni, Co, Cd, Hg, with the median values of the content Ba, Cr, Fe, and Pb exceed similar values for the relatively "clean" territory of Norway. During the study of radionuclide concentrations, concentrations of the following radioisotopes were detected and determined: 137Cs, cosmogenic radionuclide 7Be, radioisotopes of lead 212Pb, thallium 208Tl, Bi and actinium 228Ac – daughter products of thorium radionuclide 223Th and isotopes of lead 214Pb and bismuth 214Bi – daughter products of uranium 238U. Conclusion: The high concentrations of such heavy metals in moss samples in the territories nearby the city (near landfills) are comparable to the concentrations of heavy metals in vegetation samples from places located near, for example, industrial sites of mining and processing plants. The detection of the same heavy metals and radionuclides in the atmospheric environment, the soil of the city and in vegetation, the soil near the landfill may indicate that one of the sources of environmental pollution and effects on human health may be the combustion products of the contents of the landfill on the 9th km along the Vilyuysky tract.

Abstract Understorey biodiversity is increasingly impacted by extreme climate events. Retention forestry, which involves preserving small patches of live and dead trees from preharvest forests within clearcuts, can help mitigate these extremes by creating more favourable microclimates than traditional clearcutting practices. Despite their importance in buffering climate extremes, it remains unclear whether, and to what extent, the microclimates in retention patches enhance the growth response and recovery of the understorey after extreme droughts in boreal managed forests. We retrospectively investigated the annual growth response from 2016 to 2022 of the mat‐forming understorey moss Hylocomium splendens, in relation to micro‐ and macroclimate, including an extreme drought in 2018, in retention patches relative to clearcuts and mature forests, across 130 plots distributed across 30 forest sites in a boreal landscape in Sweden. The 2018 summer drought reduced the annual growth rates of H. splendens. Clearcuts experienced the greatest climatic impact from the 2018 drought and exhibited the lowest growth rates, followed by retention patches, while mature forests maintained the highest growth rates. This pattern persisted subsequent two post‐drought years. Closer alignment of below‐canopy temperature and vapour pressure deficits (VPDs) with those of mature forests enhanced moss growth in retention patches, bringing it closer to the levels observed in mature forests. In clearcuts and mature forests, where variation in forest canopy and microclimate was minimal, biological legacies did not influence annual moss growth. In retention patches, however, a greater basal area of large living trees and the presence of standing deadwood contributed to higher canopy closure, which reduced microclimate VPDs and increased H. splendens growth. Increasing volumes of lying deadwood positively contributed to H. splendens growth, likely by creating favourable microhabitats and microclimates near the logs. Synthesis and applications. This study demonstrates that drought reduced the growth of mat‐forming understorey H. splendens in boreal forest ecosystems, but drought effects in clearcuts are mitigated in retention patches. By preserving large living trees, standing and lying deadwood, retention patches can be further optimized. Foresters and policymakers can use these findings to minimize the impact of drought after clearcutting on understorey biodiversity and functionality.

Plant communities formed by shrub willows are widespread in the North of the Koryak Okrug (the mainland of the Kamchatka Territory) in valleys and floodplains of rivers and streams, on gentle mountain slopes, hollows and depressions, along the mire edges. The main dominants are Salix pulchra, S. alaxensis, and S. krylovii. Communities formed by some other species of shrubby willows (Salix lanata, S. saxatilis, S. glauca) are quite rare. The detailed geobotanical characteristics of shrub willow communities of the Koryak Okrug are presented. The dominant-determinant classification based on 54 relevés was elaborated following the main principles and classification methods of the Russian geobotanical school approach. As the result 21 associations, included into 13 association groups and 5 formations are revealed. The peculiarities of their species composition, communities’ structure, ecology and geographical distribution are considered. Communities formed by Salix pulchra are characterized by the higher community diversity in the study area; they occupied a wide range of habitats — from floodplains and tussock tundra to drained slopes of ridges. The low community diversity was typical for phytocoenoses formed by Salix lanata, which are quite rare in the North of the Koryak Okrug, but widespread in the Arctic regions of Eurasia. Shrub willow communities formed by Salix pulchra, S. alaxensis or S. krylovii are represented by Oligoherbosa, Calamagrostidosa, Varioherbosa, Caricosa appendiculatae and Vacciniosa uliginosi association groups; they occupy depressions, hollows, foots of ridges, the slopes of hills, and flat watersheds. Sphagnosa and Paludiherbosa willow communities are found along the mire edges and in the lake hollows. The predominance of herbaceous mesophytes is character for Varioherbosa association group; among these constant are Calamagrostis purpurea s. l. prevailed and Cirsium kamtschaticum, Chamerion angustifolium, Equisetum arvense, Galium boreale, Geranium erianthum, Rubus arcticus, Saussurea pseudotilesii, Thalictrum minus, Trientalis europaea, Veratrum oxysepalum, Viola epipsiloides. The moss layer is formed by Aulacomnium palustre, Brachythecium salebrosum, Bryum pseudotriquetrum, Climacium dendroides, Dicranum majus, Hylocomium splendens, Sanionia uncinata, Sciuro-hypnum reflexum, S. starkei, etc. Alluvial gley soils and podburs are character for the sites of Varioherbosa and Calamagrostidosa association groups. The predominance of mesohygrophytes and hygrophytes in the grass layer, and green and Sphagnum mosses in the ground layer are character for Paludiherbosa willow communities. The grass layer is usually predominated by sedges Carex appendiculata and C. lyngbyei subsp. cryptocarpa with common hygrophilous herbs (Comarum palustre, Equisetum fluviatile, Galium trifidum, Caltha palustris). Mosses Calliergon cordifolium, Plagiomnium ellipticum, Philonotis fontana, Pseudobryum cinclidioides, Rhizomnium punctatum, Straminergon stramineum occur in wet depressions. Gley, peat-gley and peat soils are character for Sphagnosa and Paludiherbosa willow communities. Arctoboreal dwarf-shrubs Empetrum nigrum s. l., Ledum palustre s. l., Vaccinium uliginosum s. l., V. vitis-idaea s. l., dwarf birches Betula exilis and B. middendorffii and mesophilous mosses are main species in the communities of Vacciniosa uliginosi association group. Caricoso lugentis-eriophorosa vaginatae association group formed by Salix pulchra is transitional to zonal tundra communities in which tussock-forming plants cotton grass Eriophorum vaginatum and sedge Carex lugens subsp. soczavaeana in the grass layer predominate. The community site differed by peat-gley and cryosols underlained by permafrost. The shrub willow community’s classification units were compared with the syntaxa identified due to the floristic (Brown-Blanquet) classification approach. Shrub willow communities occupy vast areas in river valleys and intermountain depressions; they are extremely important and valuable reindeer pastures during the summer and early autumn grazing seasons.

This study focuses on investigating atmospheric zinc deposition in the Kaliningrad Re­gion using biomonitoring methods. The moss species Pleurosium schreberi and Hylocomium splendens, collected in 2020, were selected as bioindicators. The primary aim of the study was to assess the spatial distribution of atmospheric air pollution by zinc in the region and to identify its sources. Epithermal neutron activation analysis was used to determine the metal content in the moss samples. The obtained data were processed using statistical methods and backward air mass trajectory modeling. The results indicated that zinc concentrations in the mosses varied significantly, reaching maximum values in the southern and central parts of the region. A comparison with 2015 data revealed a 46 % increase in zinc accumulation lev­els. The study established that the main sources of pollution include both local industrial facil­ities and transboundary transport of air masses from Europe, particularly under prevailing southwesterly winds.

The study, carried out as part of the International Cooperative Program on Effects of Air Pollution on Natural Vegetation and Crops, involved collecting 95 moss samples across the territory of Georgia during the period from 2019 to 2023. Primarily samples of Hypnum cupressiforme were selected, with supplementary samples of Abietinella abietina, Pleurozium schreberi, and Hylocomium splendens in cases of the former's absence. The content of 14 elements (Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, S, Sr, V, and Zn) was detected using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), while the Hg content was determined using a Direct Mercury Analyzer. To identify any relationships between chemical elements and to depict their sources, multivariate statistics was applied. Principal component analysis identified three main components: PC1 (geogenic, 43.4%), PC2 (anthropogenic, 13.3%), and PC3 (local anomalies, 8.5%). The results were compared with the first moss survey conducted in Georgia in the period from 2014 to 2017, offering insights into temporal trends of air quality. Utilizing GIS, a spatial map illustrating pollution levels across Georgia, based on the Pollution Load Index, was generated. The Potential Environmental Risk Index emphasized significant risks associated with mercury and cadmium at several locations. The study highlights the utility of moss biomonitoring in assessing air pollution and identifying hotspots of contamination. The findings from this study could be beneficial for future biomonitoring research in areas with varying physical and geographical conditions.

Instrumental neutron activation analysis in combination with the method of moss biomonitoring for the assessment of atmospheric deposition of heavy metals and other elements was applied for the first time in the Ryazan Region in Russia. Concentrations of 42 macro, micro and trace elements in 63 moss samples (Hylocomium splendens and Pleurozium schreberi, as well as Hypnum cupressiforme, Sciuro-hypnum sp., Plagiothecium sp. and Ptilium sp.), collected on a relatively uniform grid in the study area, were determined. On the basis of analytical results using GIS technologies, maps of the spatial distribution of heavy metals and other toxic elements were constructed for the Ryazan region. The method of multivariate statistical analysis (factor analysis) was used to identify the main sources of pollution—large industrial facilities located in this region. The obtained results were included in the Atlas of Atmospheric Deposition of Heavy Metals, which is published by the UN Commission on Long-Range Transboundary Air Pollution (UNECE ICP Vegetation).

The tiny fishing settlement of Tareya (73.253389° N, 90.596806° W) on the right bank of the river Pyasina (Fig. 1, this and others see in text) in its middle reaches (Western Taymyr) is well known in the circumpolar scientific community due to the long-term Biogeocenological field station of the Komarov Botanical Institute of the Academy of Sciences of the USSR, which operated in 1965-1977. A huge amount of complex researches has been done by numerous scientists, and the results were published in a lot of proceedings, reports at the Arctic conferences, and papers published in various journals, which formed the basis of several monographs as well as the large article in the multi-volume international edition «Ecosystems of the world» [Chernov, Matveyeva, 1997]. It was the reason why just this site was considered as point number one for doing work within the project “Back to the Future” (hereinafter BTF). The idea of visiting the sites of long-term work carried out in circumpolar Arctic within UNESCO “International Biological Program” arose in connection with the popular concept of global warming. The BTF task suggested to assess the current state of arctic ecosystems in details studied half a century ago. In several sites in the North American Arctic this was achieved on the eve of the International Polar Year (2008) [Callaghan et al., 2011a]. The Taymyr trip, took place in July–August 2010. Only the first author worked at the station from its beginning in 1965 and last time was there 40 years ago (1970). The period of field works in 2010 (July 21 – August 8), was not promising for detailed researches due both to the extremely short (18 days) stay and unfavorable weather. Botanists managed to re-inventory the flora of vascular plants and assess their activity in landscape, to make relevés at two permanent experimental stands and selectively some communities as well walk around the territory with vegetation map [Matveyeva, 1978]. The results on the flora were published [Matveyeva et al., 2014]. This paper presents the results of assessing the state of plant cover. We were well aware that opportunities for such a short time of repeated study in assessing the state of ecosystems and making not just expert conclusions about any changes, but to evaluate these quantitatively and to explain their reasons, were minor. In our case, different not only at moments far apart in time, but also at the same time in the past were the methodology doing relevés, including the size of sample plots, the totality of species records and quantitative assessment of their presence in communities, as well as professionalism by researchers, including their field work experience. We kept all this in mind when assessing the results, trying to distinct objectivity, subjectivity and expertise when interpreting these. In the past, detailed studies were carried out at six permanent sites [see: Matveyeva, 1968, 1969; Matveyeva et al., 1973], the most important of which were zonal communities on watersheds – frost-boils and hummock stands. DRyad–sedge–moss frost-boils stand (Matveyeva, 1968: Fig. 1, 3-5, Table 1; Matveyeva et al., 1973: Fig. 4, Table 1. Site N 2) is located on terrace above the floodplain close to high river bank of approx. 10 m high. In the checklist of Taymyr communities, according to the dominant classification [Matveyeva, 1985] it is classified as the ass. Hylocomium splendens var. alaskanum+Aulacomnium turgidum+Tomentypnum nitens–Carex ensifolia+Dryas punctata; according to the Zürich-Montpellier (hereinafter Z-M) school floristic one (Braun-Blanquet (hereinafter B-B) approach) – to the ass. Carici arctisibiricae–Hylocomietum alaskani Matveyeva 1994. In the past, the relevés were carried out on two sample plots located in close proximity to each other, 10 × 10 m (in 1966) and 15 × 15 m (in 1969), with lists of species (vascular plants, mosses, liverworts, lichens) according to 3 nanorelief elements (soil patch, rim, trough), with measurements of their size, and the horizontal structure schemes on both. We did not find those sample plots in 2010, so the relevé was performed on a new plot of 10 × 10 m. Only vascular plants were guaranteed to be identified totally with assessment of their abundance/cover on the B-B scale while that of bryophytes and lichens was estimated only for the most common and large-sized species, relatively easy identified in the field. Due to nanorelief of cryogenic genesis community horizontal structure is of 3-item regularly cyclic type [see. Matveyeva, 1988, 1998], with module repeating in space: soil patch (up to ~0.8 m diam.) at different stages of overgrowth on the medallion (up to 1.3 m diam.) +rim along its periphery (up to ~0.5 m wide)+trough (~0.3 m wide) between medallions (Fig. 2). This type of horizontal structure was preserved in 2010, although some values of element sizes were close, but not identical (Appendix 1, Table П1). However, the fact that after more than 40 years the number of modules per 100 m2 (32 and 31) and the ratio of their elements (patches 30%, rims 50%, troughs 20%) are the same, is rather evidence in favor of the horizontal structure stability, with variances due to measurement error of items widely varying in shape. Visually, the share of bare soil decreased slightly (no more than 2-3%), that caused a minor increase of total community plant cover, ~90% in 1966, 1969. up to ~92% in 2010. The dominating species in the ground layer were Hylocomium splendens var. alaskanum, Aulacomnium turgidum, Tomentypnum nitens, in the sparse upper one – Carex bigelowii ssp. arctisibirica and Dryas punctata. There were 197 species (60 vascular plants, 49 mosses, 27 liverworts, 61 lichens) on two sample plots, being different (135 and 180) on each one, due to some nuances of methodology (the lower number in 1966 is the work of a beginning graduate student, while later is the professional job by specialists in bryophytes; the lichen number was close because lichenologists were working on both plots). This community is the richest in species known in circumpolar Arctic [Matveyeva, 2009]. In 2010, on 10 × 10 m plot the composition of vascular plant species was identified with assessment of their abundance/coverage in points on the B-B scale for the entire area; that of bryophytes and lichens was estimated only for the most common and large-sized species. The most abundant ( 1%) species in the sparse low dwarf shrub-herbaceous layer were the same as before – sedge Carex bigelowii subsp. arctisibirica and dryad Dryas punctata. 11 species (all previously with low abundance/occurrence or single specimen) were not found, including two (underlined) in the past were recorded only on one of the two plots – Androsace chamaejasme, Cardamine bellidifolia, Koeleria asiatica, Orthilia obtusata, Papaver pulvinatum, Pedicularis capitata, P. hirsuta, Petasites frigidus, Nardosmia gmelinii, Ranunculus nivalis, Saxifraga oppositifolia, Vaccinium vitis-idaea subsp. minus) and found, also single specimen, 6 (Carex misandra, Eriophorum brachyantherum, Hedysarum arcticum, Polygonum bistorta, Ranunculus affinis, Saxifraga foliolosa). Such small variances gave practically the same species richness of vascular plants – 55/57 and 56. The abundance of species and their pattern at nanorelief elements remained unchanged except the cover increase of the most active species in the landscape – sedge Carex bigelowii subsp. arctisibirica. For entire community with rims occupying half of its area, this gives an increase of ~10% in layer density, i. e. the sedge abundance over the whole area remained the same (2 points). As cryptogams composition was not completely assessed, we cannot comment their richness, however all co-dominants in ground layer (mosses Hylocomium splendens var. alaskanum, Aulacomnium turgidum, Tomentypnum nitens and liverwort Ptilidium ciliare), as well species with previously significant ( +) cover kept their abundance. The obtained results provide the basis for a partly objective, partly expert conclusion that there are no significant changes in the composition of species and in their distribution within this stand. DRyad–sedge–moss hummock stand [Matveyeva, 1968: Fig. 6, 8, Table 1; Matveyeva et al., 1973: Fig. 3, Table 1. Site N 1] is located on the first terrace above the floodplain in the upper part of stream valley gentle slope at 1.5 km from the riverbank. In the checklist of Taymyr communities, according to the dominant classification [Matveyeva, 1985] it is classified as the ass. Hylocomium splendens var. alaskanum+Aulacomnium turgidum+Tomentypnum nitens–Carex ensifolia+Dryas punctata. This community with closed cover is the same in dominants as the above frost-boils one: Hylocomium splendens var. alaskanum, Aulacomnium turgidum, Tomentypnum nitens, and Ptilidium ciliare in the ground layer, and Carex bigelowii ssp. arctisibirica and Dryas punctata in the sparse upper one. Despite the common dominants and significant number of species with similar abundance, communities with closed cover are poorer in species due to the lack of species obligate to bare or partly overgrown soil. The positioning of such communities in the classification of the Z-M school (B-B approach) was not proposed. In the future, it is possible either to describe new association or to identify a subassociation. There is nanorelief of cryogenic genesis, caused by frost ground cracking and its consequences – hummocks 0.10-0.12 m high and 0.15-0.30 m diam. which sometimes, merging together, form chains or almost locked rims, and troughs 0.15-0.20 m wide, with no patches of bare soil (Fig. 3). The type of horizontal structure is irregular mosaic (Matveyeva, 1988). In 2010, what awaited us in this community was not just a surprise, but rather a shock. A transformation took place that we [Matveyeva et al., 2011; Matveyeva, Zanokha, 2013] formulated as “polygonization” of loamy watersheds – the previously leveled surface (with described nanorelief) turned into a system of mounds (7-10 m diam.) and trenches (2-5 m wide) with significant (0.5-1.0 m) excess in height (Fig. 4). In terms of the area size and the pattern of heterogeneity with rows of mounds and trenches, these are most similar to the massifs of bajdzharakhs (the Yakutian name for mounds that appears a result of the fossil ice wedge melting). Such serious changes occurred without disturbances in the plant cover, as well as in the absence of erosion, with the previous nanorelief and the same irregular mosaic type of horizontal structure both on the surface of mounds and their almost vertical slopes, and in trenches. Since there were no signs of this until 1994 (evidence from colleagues who worked here after 1970), and the system already existed in 2003 (Google Earth Quick Birds, 8.11.2003), the transformation has occurred in less than 9 years. We were not able to find the old sample plots in 2010, and only a wooden stick and small (10 × 20 and 50 × 50 cm) metal frames (used for horizontal structure study) near it convinced us that this was the same permanent stand. More than 40 years later, the horizontal structure on both new microrelief elements looked the same: the familiar combination of hummocks and troughs, but visually the surface became smoother due to the decrease in the height of the elements relative to each other. The link of species with nanorelief elements did not change, with the same dominants on hummocks (mosses Hylocomium splendens var. alaskanum and Aulacomnium turgidum, sedge Carex bigelowii ssp. arctisibirica and dwarf shrub Dryas punctata) and in troughs (Тоmentypnum nitens and Ptilidium ciliare and the same vascular plants but with lower abundance). In general, the variances in species composition between the sample plots in 1966 and 1969 were similar to those recorded in the frost boils stand, but noticeably more dissimilar (69 and 141), and not only in cryptogams but in vascular plants (Appendix 1, Table П3). In 2010, full information was obtained only about vascular plants: 43 species (32 and 33 on 2 mounds) with the same dominants both on mounds and in trenches that were previously on the flat stand surface. The abundance of sedge Carex bigelowii ssp. arctisibirica has increased up to 3 points versus 2 and that of cotton grass Eriophorum angustifolium to 2 versus 1 and +, with the same abundance of dwarf shrubs Dryas punctata and Cassiope tetragona. We found no changes in species composition or abundance in dry trenches compare to the formerly flat surface of the community and the current mound one. The second object is 3-element rim-polygonal mire. RIM-POLYGONAL MIRE [Matveyeva et al., 1973: Fig. 4, Table 3. Site N 4] in 1969 was located in: flat-concave lake depression on a river terrace above the floodplain in about 1 km from the riverbank. There are from hundreds to thousands of modules polygon center+rim+trench – wet polygon 15-20 m diam. with 1) concave center and 2) rim along it periphery 1.0-1.5 m wide, rising (0.15-0.20 m) above central part and 3) water trenches between polygons in a polygonal system (Fig. 6). Quite arbitrarily, without assigning their vegetation to any units of any classification, lists of species were made for three microrelief elements. Altogether there are 110 species (vascular plants 24, mosses 47, liverworts 24, lichens 15) were identified, with respectively 34 (10, 24, 0, 0) on polygon centers, 80 (16, 28, 21, 15) on rims, and 34 (8, 23, 3, 0) in trenches. Co-dominants in continuous moss layer are Cinclidium latifolium, Sarmentypnum sarmentosum, Scorpidium revolvens, Meesia triquetra on polygon centers and in trenches, and Aulacomnium turgidum, Hylocomium splendens var. alaskanum, Tomentypnum nitens on rims; these in the sparse above moss layer are Carex aquatilis subsp. stans and C. chordorrhiza on polygon centers and Carex aquatilis subsp. stans in trenches, and Betula nana, Dryas punctata and Salix pulchra on rims. The classification of such complex object is debatable in all respects, beginning from the relevé methodology (choice of sample plots, their size, number) as well as defining the object status. It is most logical to consider the plant cover of each of the 3 elements as communities, trying to classify them independently, however this is not too obvious: there are 18 numbers in the scheme legend, that demonstrates both the obvious cover complexity (3 types of communities) and the mosaic nature of each type – 7 units on polygon centers, 8 on rims, 3 in trenches. In the Z-M school system (B-B approach), vegetation on polygon centers and in trenches is classified as mires of the class Scheuczerio–Caricetea nigrae (Nordh. 1936) R. Tx. 1937; while that on rims as communities close to zonal ones of the class Carici arcrtisibiricae–Hylocomietea alaskani Matveyeva Lavrinenko 2023 (ass. Carici arcrtisibiricae–Hylocomietum alaskani Matveyeva 1994). In 2010, we not only failed to make relevé on previous sample plot, but could not determine its exact location in wet depression. This was because the general picture of microrelief in the area, where site in question was situated, was so different from described above, that an attempt to obtain a photo of a “classical” rim-polygonal mire for a lecture course for students (which was so easy to do before) turned in vain: there were only isolated hummocks due to partial going down (subsidence) of most rims (Fig. 7), In another massif (south of Lake Bolshoye), which vegetation on map [Matveyeva, 1978] is shown as a 3-item rim-polygonal mire, all rims went downwards, and the polygon surface became flat (Fig. 8, а). As a result, the previously clearly heterogeneous plant cover visually (from a human height) became looked homogeneous. Although heterogeneity remained (Fig. 8, б): in 2010, obviously hygrophilic grasses (Carex aquatilis subsp. stans, Eriophorum medium, Hierochloë pauciflora) and mosses (Sarmentypnum sarmentosum, Cinclidium latifolium, Scorpidium revolvens, Meesia triquetra, etc.) and just as obviously mesophilic shrub/dwarf shrub (Betula nana and Dryas punctata) and mosses (Aulacomnium turgidum, Hylocomium splendens var. alaskanum, Tomentypnum nitens, etc.) cohabit at the same surface level with high soil moisture. Anyone who has seen this would not be able to find an adequate explanation for this phenomenon without knowing the past of such areas. Our expert conclusion is that, despite significant transformations in microrelief, the heterogeneity of plant cover as well as species composition are the same as before, with slight change in the abundance of some dominants. Another type of polygonal complexes is developed in the upper reaches of numerous brook valleys. BOG-TUNDRA POLYGONAL COMPLEX [Matveyeva et al., 1973: Fig. 5, Table 3. Site N 3] in 1969 was located on a river terrace above the floodplain in 1 km from the riverbank in a depression in the upper reaches of a short valley directly close to settlement. The structure of sample plot (50 × 60 m) is a complex of drained polygons of diverse shape and size (15-30 m diam.) and trenches (0.5-6.0 m wide and 0.2-0.3 m deep), filled with water (Fig. 9). The area ratio polygons/trenches is 80/20%. The name of the complex reflects the heterogeneity of its vegetation. Plant cover on polygons is close to that of low watersheds with dominance of willows Salix reptans, S. pulchra and dwarf birch Betula nana in the shrub layer, sedge Carex bigelowii subsp. arctisibirica and cotton grass Eriophorum angustifolium and dwarf shrubs Dryas punctata, Cassiope tetragona, Vaccinium vitis-idaea subsp. minus in dwarf shrub–herbaceous, and Aulacomnium turgidum, Hylocomium splendens var. alaskanum, Tomentypnum nitens in moss one; and mire in trenches with the same shrubs as on the polygons, sedge Carex aquatilis subsp. stans and cotton grass Eriophorum angustifolium and hygrophilic mosses Sarmentypnum sarmentosum, Cinclidium latifolium, Scorpidium revolvens, Meesia triquetra, Polyrichum jensenii. There were 85 species (35 vascular plants, 41mosses, liverworts were not detected, 9 lichens), respectively – 59 (30, 20, 9) on polygons and 35 (12, 23, 0) in trenches. The classification of this object is no less problematic in all respects, as of rim-polygonal mire vegetation. Most logical is to consider the vegetation on each of two elements as communities and try to classify them separately, which is quite difficult. There are 19 numbers in the map legend – two community types with 13 inside units on polygons and 6 ones in trenches. Such complexes so far have not been described in literature. In 2010, visually everything looked as before, however this conclusion is subjective being based upon only on two routes through a vast complex system, including a stationary site with wooden sticks. TUNDRA AND NIVAL-MEADOW COMMUNITIES ON THE SOUTHERN SLOPE OF THE RIVER BANK [Matveyeva et al., 1973: Fig. 7, Table 4, Site N 5]. The steep slope, is cut by hollows (with 3-5 m snow beds) formed due to the ice wedge melting (Fig. 10). Ridges, in winter with little snow, melting completely in June, are in summer the warmest biotopes with the maximum (up to 1.5 m) depth of frozen ground seasonal thawing. The great biotope diversity determines the heterogeneity of the plant cover, with elements small (2-3 m2) in size that form ecological series, contrasting in soil moisture and heating. There are 13 community types on sample plot (70 × 70 m). The most contrasting in comparison with stands in zonal habitats were in 1969 and remained (visually) in 2010 are herb communities on ridges (Fig. 11) with grasses (Festuca brachyphylla, Koeleria asiatica, Trisetum sibiricum subsp. litorale) and forbs (Astragalus alpinus, Cerastium maximum, Myosotis alpestris subsp. asiatica, Oxytropis adamsiana, Pachypleurum alpinum, Pedicularis verticillata, Polemonium boreale) from 0.10-0.15 to 0.30-0.35 m high and thin (up to 0.01 m), and sparse moss layer of Hypnum revolutum, Sanionia uncinata, Thuidium abietinum. Later such community types became the object of close attention [Zanokha, 1993] in different areas of Taymyr (but not in Tareya), and was classified as the ass. Pediculari verticicillatae–Astragaletum arctici Zanokha 1993, but with no placing in any higher unit. The plant cover of such herb communities, in terms of life form set and horizontal and vertical cover structure is closest to boreal meadows of the class Molinio-Arrhenatheretea Tüxen 1937, however composed of not boreal, but of arctic and arctic-alpine species, that stops these from being placed in this class. As well, conditional is the positioning [Matveyeva, Lavrinenko, 2021] of such communities in the class. Mulgedio-Aconitetea Hadač et Klika in Klika et Hadač 1944. In 2010, the lists of vascular plant species were compiled for such herb communities along the whole riverbank of the field station area, and no differences were recorded in their activity [Matveyeva et al., 2014]. It is worth to notice that the methodology for getting data in the past is not described, and it differs from that adopted in the Z-M school. This will not allow objectively assessing possible changes in the future that should be kept in mind by those who will manage to visit this area. VEGETATION UNDER MAN IMPACT [Matveyeva et al., 1973; Fig. 8. Site n 6]. In 1965, when six BIN researchers arrived to Tareya, life in tiny fishing settlement was in full swing. The basis of this was a vast man-made cave in the permanently frozen ground of the high river bank. It was used to store fish that was caught by teams of fishermen from Norilsk State Industrial Enterprise, scattered across the vast Western Taymyr territory. Fishermen were flown to “points” on AN-2 planes, from where the catch was regularly taken, brought to Tareya, frozen and stored until the autumn fishing season, when ships with barges arrived along the river from the Norilsk city. There were three small houses (at the edge of the floodplain) for living and a house where the radio operator lived and worked. In addition, there was a large plank house owned by the Arctic and Antarctic Research Institute (AARI), permission for its use became the basis for organization of a long-term BIN field station (Appendix 2, Fig. П1). In the first summer (1965), the pioneer group lived in a plank house (future laboratory). The following summer, scientific field station began to function, which gathered from 18 (1966) to 30-40 (1967-1969) people from various scientific institutes, who lived in numerous tents located on a gentle slope between the laboratory and the radio operator' house. After 1977, the living buildings continued to be used by fishermen, as well as geologists. Fishing intensity gradually decreased becoming private. In a spring (the year is unknown) high flood, three small houses were carried away by water; the laboratory house was burned down in 1998. Before 1965, the plant cover was quite changed, since for a long time the base of the geological expedition of the AARI was located here. Its initial state is dryad-sedge-moss hummock tundra, common on gentle slopes with the dominance of mosses Aulacomnium turgidum, Hylocomium splendens var. alaskanum, Tomentypnum nitens, sedge Carex bigelowii subsp. arctisibirica, dwarf shrub Dryas punctata. During the field station functioning, the load (trampling) on plant cover in summer (late June–early September) was quite strong. In 1968, the vegetation of the territory was verbally described, and a map-scheme was made, with 12 items in legend [Matveyeva et al., 1973]. In 1968, the most of area between houses, where the original vegetation was damaged almost completely, was occupied by suppressed and sparse grass cover. In 2010, it looked like the original dryad-sedge-moss tundra, with no obvious signs of disturbance and with no high abundance of apophytic grasses (Alopecurus alpinus and Poa alpigena). However walking along, it at the end of July–beginning of August was possible only in rubber boots, i. e., the soil moisture was significantly higher than before, when we lived in tents and walked in light sports shoes. Vegetation map. The conclusion that in 2010 communities have kept their belonging to the same earlier classified community types is made according to their look when walking around the territory with vegetation map that would not have to be changed (Fig. 13). Some of the objectivity of this opinion is supported by the fact that it was done by the researcher who made this map, as well as by few relevés, where the community structure and species composition remained the same. Flora of vascular plants. There were 212 species on the territory that was studied in 2010 [Polozova, Tikhomirov, 1971]. After 40 years, we did not find 29 species (all rare in the landscape) and discovered 10 new ones (all in the floodplain of the Pyasina River, rare, many in a single specimen). We refer a reader to the publication [Matveyeva et al., 2014], the main conclusions of which are as follows: 1) the main reason for the incomplete identification of the flora is the short duration of the research in 2010; 2) there is no firm conviction that newly found species were absent 40 years ago; 3) assuming that the last are still present, the systematic and geographical structure flora remains unchanged. It is possible to assess changes in species activity within landscape only for a total of 184 species – in 162 (88.5%) it remained unchanged, in 5, with the same activity, abundance slightly increased or decreased; activity decreased by 1 point in 22 (mean and low active) species. Small changes in the landscape pattern of species with low activity may be considered both objective and subjective (short duration of observations in 2010 and uncertainty in estimations in the 1971 annotated list). No information was obtained on the cryptogam flora (mosses, liverworts, lichens), earlier detailed studied. Our partly expert opinion is that their composition and presence in communities have not undergone noticeable changes. However, for an objective assessment it is necessary to conduct studies similar to those that were done at high professional level [Pijn, Trass, 1971; Blagodatskikh, 1973; Zhukova, 1973]. THE DISCUSSION OF THE RESULTS. The most general conclusion based on the results of various observations in the course of repeated (after 40 years) visit to the area of long-term field station functioning can be formulated as follows: stability in the plant cover with significant transformations in the landscape, micro- and nanorelief, and as a consequence in changes in surface/inside soil water flow. From the diverse cryometamorphic processes, we focus the most significant and noticeable one, that might considerably change the plant cover on the above-floodplain terrace, where previously there were 2 systems, both in depressed landscape sites: 1) rim-polygonal mires (in lake depressions, bottoms of drained lakes of thermokarst origin) and 2) bog-tundra complexes (concave surfaces of watersheds, dissected by trenches as a result of backward erosion). The third one, with flat mounds of different height and size and trenches of various width and depth, appeared in zonal sites. (Fig. 15). This happened on a large area, lot of watersheds is transformed completely with some (most wide and flat) being so far rather uniform. The beginning or early stages of this process in the form of future polygonal system were recorded already in 1968 by geocryologist [Danilov et al., 1971]. In 2010, already in the field on many interfluves between brook valleys, especially on the widest ones, with a horizontal surface in their middle part, we observed the beginning of polygonization so far with no upcoming mound exceeding the trenches in height ( 1-2 cm), which is clearly visible on satellite images (Fig. 16). Potentially, the presence of trench system on watersheds may strengthen the hydrological cycle through higher inside soil flow (that will eliminate trench wetting), however as drainage system it will reduce the moisture amount on watersheds, that may lead to larger frozen soil seasonal thawing, and greater thermokarst in zonal sites. What will be a result of such large transformation is a subject of professional interest for geocryologists. We can only state the landscape instability, which was not recorded 40 years ago in Tareya. The second phenomenon of significant change is the coming down of rims in rim-polygonal mires, in the place of which only isolated hummocks remained, or the surface of the polygons has become flat, the most important consequence of which was a radical change in hydrological regime. In classic rim-polygonal mire systems, the water on the isolated concave polygon centers surrounded by rims is standing water, while in trenches between polygons it is running, and there is a general waterway, which gathers water from connected trenches. This is the source of brooks through which the general (surface and inside) water flow is running away the wetland (Fig. 17). Without rims, the previously standing water on polygons, being no longer isolated, has become running, that increased the total flow (a kind of drainage). On the downed rims, the plant cover is so far (visually) the same. Although the fact that the mire, heavily watered throughout the growing season in 1967-1969 (and according to satellite image in 2003), in 2010 has lost part of water, affected the activity of the most important grasses – the abundance of Hierochloë pauciflora and Carex chordorrhiza previously dominated on the most watered polygons became less, while that of Carex aquatilis subsp. stans (previously also rather abundant) increased. This expert conclusion is based on difficulty in finding the first two species, which previously were common in these biotopes. At first sight, our judgment about stability in plant cover along with great landscape transformation, looks at least contradictory. In our defense, we propose thesis that stability does not mean the absence of any changes. The latter includes changes in the activity (abundance, occurrence) of some vascular plant species, dominants in communities in zonal sites (Carex bigelowii subsp. arctisibirica) and in mires (Carex chordorrhiza, C. aquatilis subsp. stans, Hierochloë pauciflora). However, for the majority (88.5%) of species it remained unchanged; for few ones the abundance slightly increased or decreased, which did not cause noticeable changes in the structure of communities and their diversity. To explain the slight increase in the cover density on ground patches in frost-boils stands and that of main dominant, the long-rhizome sedge Carex bigelowii subsp. arctisibirica, is hardly makes sense to attach the argument, most common in the last decade, about global warming. A series of questions arises – what do we know about vegetation before we worked in this area 40 years ago? how much do we know about the life cycles of Arctic species populations, about the species individual growth? as well, without single-vector climate trend, changes in vegetation do not occur? or we ignore natural succession? Our conclusion about the stability of syntaxonomic diversity, with small changes in the communitiy structure and with minor variation in vascular plant species set in local flora and their activity in landscape, in general coincides with the opinion of colleagues, who worked within the BTF project in Canada and Greenland, and repeated studies over shorter periods in Alaska and the European North, differing in minor details. This is inspiring and at the same time amazing, because only on Taymyr (besides Tareya, in the Dickson area) this stability takes place against the background of spectacular landscape transformation – polygonization of watersheds and modification of rim-polygonal mires. The formation of the third polygonal system on watersheds, in addition to the widespread polygonal mires and bog-tundra polygonal complexes in depressions, may continue, which gradually lead to radical transformation of the Arctic landscape on the plains. However, to predict exactly, what consequences will follow, is difficult. The existence of new formed trenches proposes their greater moisture, in comparison with mounds and the former flat surface, but the fact that these are not isolated, but form system, suggests a drainage effect. We are not ready to predict to what extent the intra-soil moisture runoff increasing will balance or exceed the current greater moisture in trenches, this is a matter for soil scientists. However, there is no doubt that the dynamics of vegetation in zonal sites depends on this, and significant changes in the plant cover may be expected over vast areas. The data obtained by us and other researchers in different Arctic regions indicate the stability of the plant cover in the course of the period that coincides with the ascending wave of climate warming in high latitudes, which is the second in the 20th century [Vize. 1937; Rosenbaum, Shpolyanskaya, 2000; Malinin, Vainovsky, 2018], even in situations of mobile landscape.

Climate change in high latitude regions leads to both higher temperatures and more precipitation but their combined effects on terrestrial ecosystem processes are poorly understood. In nitrogen (N) limited and often moss-dominated tundra and boreal ecosystems, moss-associated N2 fixation is an important process that provides new N. We tested whether high mean annual precipitation enhanced experimental warming effects on growing season N2 fixation in three common arctic-boreal moss species adapted to different moisture conditions and evaluated their N contribution to the landscape level. We measured insitu N2 fixation rates in Hylocomium splendens, Pleurozium schreberi and Sphagnum spp. from June to September in subarctic tundra in Sweden. We exposed mosses occurring along a natural precipitation gradient (mean annual precipitation: 571-1155 mm) to 8 years of experimental summer warming using open-top chambers before our measurements. We modelled species-specific seasonal N input to the ecosystem at the colony and landscape level. Higher mean annual precipitation clearly increased N2 fixation, especially during peak growing season and in feather mosses. For Sphagnum-associated N2 fixation, high mean annual precipitation reversed a small negative warming response. By contrast, in the dry-adapted feather moss species higher mean annual precipitation led to negative warming effects. Modelled total growing season N inputs for Sphagnum spp. colonies were two to three times that of feather mosses at an area basis. However, at the landscape level where feather mosses were more abundant, they contributed 50% more N than Sphagnum. The discrepancy between modelled estimates of species-specific N input via N2 fixation at the moss core versus ecosystem scale, exemplify how moss cover is essential for evaluating impact of altered N2 fixation. Importantly, combined effects of warming and higher mean annual precipitation may not lead to similar responses across moss species, which could affect moss fitness and their abilities to buffer environmental changes.

Extreme droughts are globally increasing in frequency and severity. Most research on drought in forests focuses on the response of trees, while less is known about the impacts of drought on forest understory species and how these effects are moderated by the local environment. We assessed the impacts of a 45-day experimental summer drought on the performance of six boreal forest understory plants, using a transplant experiment with rainout shelters replicated across 25 sites. We recorded growth, vitality and reproduction immediately, 2 months, and 1 year after the simulated drought, and examined how differences in ambient soil moisture and canopy cover among sites influenced the effects of drought on the performance of each species. Drought negatively affected the growth and/or vitality of all species, but the effects were stronger and more persistent in the bryophytes than in the vascular plants. The two species associated with older forests, the moss Hylocomiastrum umbratum and the orchid Goodyera repens, suffered larger effects than the more generalist species included in the experiment. The drought reduced reproductive output in the moss Hylocomium splendens in the next growing season, but increased reproduction in the graminoid Luzula pilosa. Higher ambient soil moisture reduced some negative effects of drought on vascular plants. Both denser canopy cover and higher soil moisture alleviated drought effects on bryophytes, likely through alleviating cellular damage. Our experiment shows that boreal understory species can be adversely affected by drought and that effects might be stronger for bryophytes and species associated with older forests. Our results indicate that the effects of drought can vary over small spatial scales and that forest landscapes can be actively managed to alleviate drought effects on boreal forest biodiversity. For example, by managing the tree canopy and protecting hydrological networks.

Assessment of air pollution in South Kazakhstan using moss (Hylocomium splendens) biomonitoring technique and neutron activation analysis

Nitrogen (N) fixation by moss-cyanobacteria associations has been recognized as an important N input pathway in many ecosystems from arctic tundra to tropical forests. However, the transfer of fixed N2 from mosses to the soil as well as the effects of rainfall frequency and volume on this N transfer has hardly been studied – even though mosses can leach nutrients upon rewetting. In this study, we investigated the transfer of fixed N2 by moss-cyanobacteria associations in one month under four watering regimes with a combination of high and low volume and frequency. For this, we used two morphologically similar moss species collected from ecosystems with different climate and N availability (subarctic - Hylocomium splendens; and tropical - Thuidium delicatulum). Acetylene reduction assays were conducted as a measure of N2 fixation rates in mosses, and 15N-N2 tracing was used to follow the fixed N2 from moss to the underlying substrate. Nitrogen fixation rates were higher in T. delicatulum than in H. splendens, but rainfall volume and frequency did not show strong effects on N2 fixation rates. Nonetheless, the extent of N leached from mosses was more sensitive to an increase in rainfall volume than to an increase in frequency, and more N was lost from T. delicatulum under high volume precipitation than from H. splendens. Both total nitrogen and 15N enrichment results demonstrate that the fixed N2 was mostly stored in moss tissues with less than 1 % leached to the substrate. Our results show that both moss species retain almost all fixed N2 within their tissues under small rainfall disturbances within one month, while increased N availability under higher precipitation volume renders some moss species an important N source for the soil.

Fiber-like cells with thickened cell walls of specific structure and polymer composition that includes (1 → 4)-β-galactans develop in the outer stem cortex of several moss species gametophytes. The early land plants evolved several specialized cell types and tissues that did not exist in their aquatic ancestors. Of these, water-conducting elements and reproductive organs have received most of the research attention. The evolution of tissues specialized to fulfill a mechanical function is by far less studied despite their wide distribution in land plants. For vascular plants following a homoiohydric trajectory, the evolutionary emergence of mechanical tissues is mainly discussed starting with the fern-like plants with their hypodermal sterome or sclerified fibers that have xylan and lignin-based cell walls. However, mechanical challenges were also faced by bryophytes, which lack lignified cell-walls. To characterize mechanical tissues in the bryophyte lineage, following a poikilohydric trajectory, we used six wild moss species (Polytrichum juniperinum, Dicranum sp., Rhodobryum roseum, Eurhynchiadelphus sp., Climacium dendroides, and Hylocomium splendens) and analyzed the structure and composition of their cell walls. In all of them, the outer stem cortex of the leafy gametophytic generation had fiber-like cells with a thickened but non-lignified cell wall. Such cells have a spindle-like shape with pointed tips. The additional thick cell wall layer in those fiber-like cells is composed of sublayers with structural evidence for different cellulose microfibril orientation, and with specific polymer composition that includes (1 → 4)-β-galactans. Thus, the basic cellular characters of the cells that provide mechanical support in vascular plant taxa (elongated cell shape, location at the periphery of a primary organ, the thickened cell wall and its peculiar composition and structure) also exist in mosses.

Moss-cyanobacteria symbioses were proposed to be based on nutrient exchange, with hosts providing C and S while bacteria provide N, but we still lack understanding of the underlying molecular mechanisms of their interactions. We investigated how contact between the ubiquitous moss Hylocomium splendens and its cyanobiont affects nutrient-related gene expression of both partners. We isolated a cyanobacterium from H. splendens and co-incubated it with washed H. splendens shoots. Cyanobacterium and moss were also incubated separately. After 1 week, we performed acetylene reduction assays to estimate N2 fixation and RNAseq to evaluate metatranscriptomes. Genes related to N2 fixation and the biosynthesis of several amino acids were up-regulated in the cyanobiont when hosted by the moss. However, S-uptake and the biosynthesis of the S-containing amino acids methionine and cysteine were down-regulated in the cyanobiont while the degradation of selenocysteine was up-regulated. In contrast, the number of differentially expressed genes in the moss was much lower, and almost no transcripts related to nutrient metabolism were affected. It is possible that, at least during the early stage of this symbiosis, the cyanobiont receives few if any nutrients from the host in return for N, suggesting that moss–cyanobacteria symbioses encompass relationships that are more plastic than a constant mutualist flow of nutrients.

This study presents the status and trends of long-term monitoring of the elemental concentrations of zinc (Zn), lead (Pb), and cadmium (Cd) in Hylocomium splendens moss tissue in Cape Krusenstern National Monument (CAKR), Alaska, adjacent to the Red Dog Mine haul road. Spatial patterns of the deposition of these metals were re-assessed for the period from 2006–2017 following an identical study that assessed trends between 2001–2006. In contrast to the widespread and steep declines in Zn and Pb levels throughout most of the study area between 2001–2006, this study showed more mixed results for 2006–2017. At distances within 100 m of the haul road, only Pb decreased between 2006–2017. At distances between 100–5,000 m, however, both Zn and Cd decreased between 2006–2017, with high probabilities of decrease and percent decreases of 11–20% and 46–52% respectively. Lead did not decrease in any of the more distant areas. Following earlier work on lichen species richness in the study area, it appears that 2017 Zn levels are approaching those associated with “background” lichen species richness throughout a relatively large proportion of the study area at least 2,000 m from the haul road and several km from the port site. The findings in this study may be used to plan additional mitigation measures to reduce Zn deposition related to impacts on lichen communities.

This study presents the status and trends of long-term monitoring of the elemental concentrations of zinc (Zn), lead (Pb), and cadmium (Cd) in Hylocomium splendens moss tissue in Cape Krusenstern National Monument (CAKR), Alaska, adjacent to the Red Dog Mine haul road. Spatial patterns of the deposition of these metals were re-assessed for the period from 2006-2017 following an identical study that assessed trends between 2001-2006. In contrast to the widespread and steep declines in Zn and Pb levels throughout most of the study area between 2001-2006, this study showed more mixed results for 2006-2017. At distances within 100 m of the haul road, only Pb decreased between 2006-2017. At distances between 100-5,000 m, however, both Zn and Cd decreased between 2006-2017, with high probabilities of decrease and percent decreases of 11-20% and 46-52% respectively. Lead did not decrease in any of the more distant areas. Following earlier work on lichen species richness in the study area, it appears that 2017 Zn levels are approaching those associated with "background" lichen species richness throughout a relatively large proportion of the study area at least 2,000 m from the haul road and several km from the port site. The findings in this study may be used to plan additional mitigation measures to reduce Zn deposition related to impacts on lichen communities.

Environmental pollution is one of the most important problems in urban environment. Mosses are good indicatorsof air pollution. In Estonia, heavy metals have been measured from Pleurozium schreberi and Hylocomium splendens, whichdo not grow in areas of Tallinn with a higher pollution load. In the present study, Cu, Fe and Cd were measured from fivemoss species growing in contaminated as well less polluted areas of Tallinn. Based on stationary and street pollution sourceinventory and air pollution dispersion modelling, the long-term average concentrations of fine particles (PM10) and nitrogenoxides (NOx) in air were estimated. The work revealed that it is possible to find a moss species that is common in Tallinnand grows in both polluted and less polluted areas – Syntrichia ruralis, which is the most suitable species for bioindicationbased on this work. Moss species Ceratodon purpureus accumulated the most Cd, Cu, and Fe, then Brachytheciumrutabulum/Sciuro-hypnum curtum, and Rhytidiadelphus squarrosus the least. Statistically significant higher Fe concentrationswere in the Syntrichia ruralis, compared to the Sciuro-hypnum curtum and Rhytidiadelphus squarrosus. The Syntrichia ruralisalso had significantly higher Cd content compared to the Brachythecium rutabulum/Sciuro-hypnum curtum. The results ofthe GLM analysis showed that the content of various heavy metals depends on the moss species and the degree of fine particlesin the environment, and it didn't depend on whether the moss grows on the soil or a hard substrate such as concrete, stoneor asphalt.

In boreal forests fires often ignite and spread within the dominant moss and lichen cover of the ground layer vegetation, which thus greatly influences fire hazard. We used an experimental set-up in greenhouse conditions to study the differences in how (1) fuel moisture and (2) wind velocity influence the ignition probability and fuel consumption among four common circumboreal ground vegetation fuels, Pleurozium schreberi (Willd. ex Brid.) Mitt., Hylocomium splendens Schimp., Dicranum spp. and Cladonia rangiferina (L.) F. H. Wigg. Our results show that the reindeer lichen C. rangiferina was clearly the most flammable species, with high ignition probability even at high moisture contents and low wind velocities. Of the mosses, Dicranum was the least flammable, with low ignition probability and mass loss at low wind velocities regardless of moisture content. P. schreberi and H. splendens behaved somewhat similarly with wind velocities quickly increasing the initially low ignition probability and mass loss observed in the absence of wind. However, especially for mass loss, among-species differences tended to disappear with stronger winds. The observed differences can be explained by the different structures and growth forms of the studied species and open a potential avenue for improving forest fire risk predictions.