Multi-scale remote sensing observations of a palsa in degradation phase

<p>The Vissátvuopmi palsa complex (N 68°74′50′′, E 21°11′30”) is the largest coherent palsa complex in Sweden (ca 274 ha). Aerial photo-interpretation over an area covered by plateau palsas showed a 30% decline in lateral area -- from ca 70 to 49 ha -- that occurred between 1955 to 2016 (Olvmo et al., 2020). Within Vissátvuopmi, we have more closely studied two single palsas, one dome-shaped and one ridge-shaped, for changes in extent, height and vegetation composition. Manual interpretation of aerial photography between 1955 and 2016 show lateral degradation of 35% and 54% for the dome and ridge palsas, respectively. Since 2018 we have monitored the palsas using images from drones as well as analysis of Planet Dove and Sentinel-2 satellite imagery. Photogrammetry is used to produce orthophotos as well as digital surface models (DSMs) from the drone images, and compared to earlier LiDAR and aerial photo DSMs, to study lateral and vertical degradation.</p><p>The drone-generated DSMs from 2018, 2019 and 2020 show further lateral degradation of the two large palsas. In 2020 a rapid change in vegetation composition was seen on the dome-shaped palsa, where a 250 m<sup>2</sup> area of <em>Betula nana</em> and <em>Empetrum hermaphroditum</em> transitioned to lichen. This vegetation change could be seen in spectral data from both drone and satellite platforms. The future development of this palsa, monitored annually using both fine and medium spatial resolution data, will give insight into the timing and signs of the individual palsas in stages of degradation.</p>

Biogeographic relationships between fungi and selected glacial relict plants

The paper discusses fungi of 24 glacial relict plants: <em>Arenaria ciliata</em> L. subsp. <em>ciliata, Betula nana</em> L., <em>B. pubescens</em> Ehrh. subsp. carpatica (Willd.) Asch. &amp; Graebn., <em>B. pubescens</em> subsp. <em>czerepanovii</em> (N.I. Orlova) Hämet-Ahti, <em>C. magellanica</em> Lam. subsp. <em>irrigua</em> (Wahlenb.) Hiitonen, <em>Carex rupestris</em> All., <em>Cerastium alpinum</em> L., <em>C. cerastoides</em> (L.) Britton, <em>C. eriophorum</em> Kit. in Schult., <em>Chamaedaphne calyculata</em> (L.) Moench, <em>Dryas drummondii</em> Richards, <em>D. grandis</em> Juz., <em>D. integrifolia</em> Vahl., <em>D. octopetala</em> L. s.l., <em>Empetrum hermaphroditum</em> Hagerup, <em>E. nigrum</em> L., <em>Juncus trifidus</em> L., <em>Loiseleuria procumbens</em> (L.) Desv., <em>Pedicularis sudetica</em> Willd., <em>Rubus chamaemorus</em> L., <em>Salix herbacea</em> L., <em>S. lapponum</em> L., <em>S. reticulata</em> L., and <em>Saxifraga nivalis</em> L., The work is attempt at application of some fungi (<em>Ascomycota, Chytridiales, Ustilaginales, Uredinales</em>, mitosporic fungi) as guides in vascular plant phytogeography and explanation of the origin of selected glacial relict plants. Parasites and exclusive (specialized) for particular host plant species are the most important fungi for biogeographic analysis. A fungal markers method (FMM) was used. The fungi and host plants for the present study were collected in the mountains and peat bogs of Poland, the Czech Republic, Lithuania, Slovakia, Sweden, Russia and Ukraine. Also materials from Austria, Canada, France, Greenland, Korea, Spitsbergen, Switzerland and U.S.A. were examined. A total of 254 taxa of fungi were collected from 1329 localities investigated. Exclusive species of fungi for all examined host plants have been distinguished. Only <em>Dryas octopetala</em> s.l., <em>D. integrifolia, Empetrum nigrum, E. hermaphroditum, Chamaedaphne calyculata</em> and <em>Rubus chamaemorus</em> possess a number of exclusive species sufficient for analysis. In some cases it was possible to define the direction of migration of the host plants (<em>Betula nana, Juncus trifidus, Dryas octopetala</em> s.l.) on the basis of mycological data. For dryads the extremely High Arctic track is more important than the Middle Arctic or Low Arctic ones. The waves of migrants moved from the East via Spitsbergen to-wards Greenland. <em>Dryas octopetala</em> seems to have reached the Carpathians from the West. Relative age of some fungi has been estimated. Wide circumpolar and alpine distribution points out that <em>Isothea rhytismoides</em> (Bab. ex Berk.) Fr. is one of the oldest dryadicolous fungi. The limited ranges of <em>Sphaerotheca volkartii</em> Blumer, <em>Synchytrium cupulatum</em> Thomas, <em>Hypoderma dryadis</em> Nannf.: L. Holm, and <em>Epipolaeum absconditum</em> (Johanson) L. Holm indicate a relatively young age of these species. A four new taxa i.e. <em>Lachnum uralense, Leptosphaentlina sibirica, Melanomma margaretae</em> and <em>Tiarospora pirozynskii</em> are described and illustrated. 27 species arę for the first time reported from Poland.

Dryas fell-fields in the East of the European part of the Russian Arctic

Communities with Dryas octopetala dominance are rather rare in the East European North. Some of these occupying zonal positions on watersheds within the typical tundra subzone are described in the tradition of the dominant approach at the Vangurey Upland in the northern part of Bolshezemelskaya tundra (Andreev, 1932), the highest moraine elevations in the northern parts of Malozemelskaya tundra (Dedov, 2006) and at the Kolguev Isl. (Bogdanovskaya-Gienef, 1938; Smirnova, 1938). Besides Dryas octopetala abundant species in these stands are willows Salix glauca, S. hastata, S. polaris, S. reticulata, sedge Carex arctisibirica and mesophyte forbs as well bryophytes Aulacomnium turgidum, Hylocomium splendens, Tomentypnum nitens and Ptilidium ciliare in ground layer. The diagnostic species of Loiseleurio-Vaccinietea Eggler ex Schubert 1960 Arctous alpina, Empetrum hermaphroditum and Vaccinium vitis-idaea are also common. Zonal communities of similar composition and structure, but dominating by Dryas punctata, were described on the Taymyr Peninsula as Carici arctisibiricae–Hylocomietum alaskani Matveyeva 1994 (Matveyeva, 1994) and on Wrangel Isl. as Carici lugentis–Hylocomietum alaskani (Sekretareva, 1998; Kholod, 2007) for which the new alliance Caricion lungentis all. prov., within the order Salicetalia polaris Hartmann 1980 has been suggested (Kholod, 2007). The revision of similar syntaxa in the East European North is in our plans.

Complex biotic interactions drive long-term vegetation dynamics in a subarctic ecosystem

Predicting impacts of global warming requires understanding of the extent to which plant biomass and production are controlled by bottom-up and top-down drivers. By annually monitoring community composition in grazed control plots and herbivore-free exclosures at an Arctic location for 15 years, we detected multiple biotic interactions. Regular rodent cycles acted as pulses driving synchronous fluctuations in the biomass of field-layer vegetation; reindeer influenced the biomass of taller shrubs, and the abundance of plant pathogenic fungi increased when densities of their host plants increased in exclosures. Two outbreaks of geometrid moths occurred during the study period, with contrasting effects on the field layer: one in 2004 had marginal effects, while one in 2012 severely reduced biomass in the control plots and eliminated biomass that had accumulated over 15 years in the exclosures. The latter was followed by a dramatic decline of the dominant understory dwarf-shrub Empetrum hermaphroditum , driven by an interaction between moth herbivory on top buds and leaves, and increased disease severity of a pathogenic fungus. We show that the climate has important direct and indirect effects on all these biotic interactions. We conclude that long time series are essential to identify key biotic interactions in ecosystems, since their importance will be influenced by climatic conditions, and that manipulative treatments are needed in order to obtain the mechanistic understanding needed for robust predictions of future ecosystem changes and their feedback effects.

FLOWER DEVELOPMENT OF EMPETRUM HERMAPHRODITUM (ERICACEAE), "БОТАНИЧЕСКИЙ ЖУРНАЛ"

Flowers of most Ericaceae are characterized by pentamery and sympetaly. Empetrum is one of the members of Ericaceae that deviate from this flower groundplan. Due to differences in floral morphology, earlier classifications places Empetrum in a distinct family, Empetraceae belonging to various orders. Perianth of Empetrum is composed by two trimerous whorls of free phyllomes. Different authors interpret it as either simple (with tepals) or double (with sepias and petals). The paper presents scanning electron microscopic data on flower development in Empetrum hermaphroditum. Developmental data suggest that the perianth should be interpreted as double one. Petals are free in anthetic flower and rudiments of corolla tube are not found in early stages of flower development. In this respect, Empetrum differs from some other Ericaceae with free petals in anthetic flowers (such as Rhodonendron tomentosum- Leins, 1964) where rudiments of corolla tube can be traced early in development. In both cases, secondary loss of sympetaly should be assumed. In contrast to another, unrelated genus of Ericaceae bearing flowers with three petals (Tripetaleia-Nishino, 1988) no signs of 'cryptic pentamery' can be traced in flowers of Empetrum. Different patterns of carpel arrangement are documented in Empetrum. Polymerous gynoecium of Empetrum is interpreted as an apomorphic character state derived from a gynoecium isomerous to perianth whorls.