Northern distribution limits of Sphagnum wulfianum (Sphagnaceae, Bryophyta) in the Northern Palearctic – records from tundra: coincidence or rule?

Sphagnum wulfianum is a widespread circumboreal species in the Northern Hemisphere. The distribution of this species in the Northern Palearctic was studied by generalizing and combining data from open sources (GBIF, literature data) and herbarium samples from LE, MW, NSK, and MHA into a single database. Data from herbarium labels and annotated lists were put on the map of Eurasia as points in the ArcGis 10.0 software. Analysis of the data shows that out of 3061 points 15 samples only were found in the tundra zone, which is 0.49% of all samples. This demonstrates that tundra habitats are not typical for S. wulfianum. Spatial analysis of samples collected in the Arctic of Eurasia shows that S. wulfianum was found only in the tundra of Yamal, Taz, and Taimyr peninsulas and in the part of Bolshezemelskaya tundra, which is adjacent to the Polar Urals. Analysis of vegetation history shows that S. wulfianum is a relic of the Holocene climatic optimum, preserved in the present southern tundra since the existence of forest vegetation. It is unknown from the tundras of Yakutia and Chukotka and from the mountainous tundras of Scandinavia, where any forest vegetation is unknown in the Holocene.

Long-term fungus-plant co-variation from multi-site sedimentary ancient DNA metabarcoding in Siberia

Climate change has a major impact on arctic and boreal terrestrial ecosystems as warming leads to northward treeline shifts, inducing consequences for heterotrophic organisms associated with the plant taxa. To unravel ecological dependencies, we address how long-term climatic changes have shaped the palaeo-ecosystems at selected sites in Siberia. We investigated sedimentary ancient DNA from five lakes spanning the last 47,000 years, using the ITS1 marker for fungi and the chloroplast P6 loop marker for vegetation metabarcoding. After bioinformatic processing with the OBItools pipeline, we obtained 706 unique fungal operational taxonomic units (OTUs) and 243 amplicon sequence variants (ASVs) for the plants. We show higher OTU numbers in dry forest tundra as well as boreal forests compared to wet southern tundra. The most abundant fungal taxa in our dataset are Pseudeurotiaceae, Mortierella, Sordariomyceta, Exophiala, Oidiodendron, Protoventuria, Candida vartiovaarae, Pseudeurotium, Gryganskiella fimbricystis, and Trichosporiella cerebriformis. The overall fungal composition is explained by the plant composition as revealed by redundancy analysis. The fungal functional groups show antagonistic relationships in their climate susceptibility. The advance of woody taxa in response to past warming led to an increase in the abundance of mycorrhizae, lichens, and parasites, while yeast and saprotroph distribution declined. We also show co-occurrences between Salicaceae, Larix, and Alnus and their associated pathogens and detect higher mycorrhizal fungus diversity with the presence of Pinaceae. Under future warming, we can expect feedback between fungus compositional and plant diversity changes which will affect forest advance and stability in arctic regions.

FEATURES OF THE RADIAL GROWTH OF SHRUBS BETULA NANA AND SALIX LANATA ON VARIOUS LANDSCAPE ELEMENTS IN THE SOUTHERN TUNDRA OF YAMAL

Tundra communities are widespread in the northern part of Russia, in particular on the Yamal Peninsula in the registration of Siberia, where research was carried out. For the study, we used plants of the species Betula nana and Salix lanata, these species are among the most common in the southern tundra of Yamal. Sampling sites were located on various morphological elements of the relief with the identification of patterns in the distribution of natural resources that determine the radial growth of the trunks of Betula nana and Salix lanata. At each site, at least 30 samples of each species were taken to obtain a sufficient sample. The sampling sites were located on different morpholog-ical parts of the relief. In the course of the study, general growth trends are highlighted, as well as absolute values of growth for 5 years. This age corresponds to the minimum age of the selected plants. As a result, data were obtained on the distribution and growth characteristics of Betula nana and Salix lanata shrubs along the relief profile; the most and least favourable areas of the profile for the growth of shrubs were identified. To compare the general trends of radial growth, a faster slowdown in growth was found in Betula nana. In addition, it was found that the species Salix lanata has a stronger effect on mechanical impact (winter road).

A contribution to the syntaxonomic diversity of the Tazovsky Peninsula, Arctic Russia

Syntaxonomic diversity of the vegetation in the southern tundra subzone of the Tazovsky Peninsula is represented by six associations, three subassociations and three variants. Four associations (Dicrano maji–Salicetum lanatae Khitun ass. nov. hoc loco, Sphagno girgensohnii–Betuletum nanae Khitun ass. nov. hoc loco, Empetro subholarctici– Eriophoretum vaginati Khitun ass. nov. hoc loco, Eriophoro leiocarpi–Caricetum rotundatae Khitun ass. nov. hoc loco), the three subassociations (Hierochloo alpinae– Hylocomietum splendentis empetretosum subholarctici Khitun subass. nov. hoc loco, Eriophoro leiocarpi–Caricetum rotundatae typicum Khitun subass. nov. hoc loco, Eriophoro leiocarpi–Caricetum rotundatae caricetosum chordorrhizae Khitun subass. nov. hoc loco) and the three variants are described for the first time. A high degree of similarity was found between vegetation of the Tazovsky Peninsula and vegetation of the southern part of the Gydansky Peninsula (the typical tundra subzone). They have four of six associations in common, whereas with the northern part of the typical tundra there is only one association in common.

Formation of frost boils in peat plateau of the Pur-Taz interfluve at the background of modern climate warming

In 2016-2017, we have detected numerous organic frost boils on the surface of khasyrey peat plateau in the southern tundra part of Pur-Taz interfluve (the north of West Siberia). They are related to the microrelief depressions in polygons and to the swales between tussocks. Cross-sections, cryogenic structure, properties of peat in active layer (moisture, density, heaving, chemical composition) and peat distribution within the khasyreys were studied. In the active layer, we distinguished soil and vegetation cover, upper and middle solid layers of weakly decomposed peat, lower layer of a well decomposed peat. Under the microrelief depressions, the top of permafrost is lowered, thickness and moisture of decomposed peat is increased due to the recent thawing in comparison to the elevated parts of polygons. In the cross-sections of seasonally thawing peat, we determined injections of organic matter from the lower layer of peat to the surface. We propose the mechanism of organic frost boils formation in peat plateau due to the injections during the summer seasons of 2016-2018 against the increase of a thaw depth without freezing. During the observation period, the amount of frost boils on polygonal peat plateau was found to increase.