North Okhotiya is the informal name for a huge area of land surrounding North-West coast of the Sea of Okhotsk and geologically belongs to adjacent edges of the Eurasian and Pacific Geological Plates (Seno et al. 1996). If the geological map of the west coast of the Sea of Okhotsk is looked at, a mosaic of bedrocks of different composition and age would be very prominent at the 56th degree of the northern latitude, just southward of the contact zone of two plates (http://atlaspacket.vsegei.ru/#c9d3d204b97b3b163). This geological diversity ‘hot spot’ covers the vicinity of the Ayan Settlement and stretches westwards to the axial line of Dzhugdzhur Range – one of the great ranges orographically connecting Northeast Asia and East Asia. The rocky outcrops in this area vary from Archean time (observed mainly on the axial part of Dzhugdzhur Range), to younger rocks, up to the Cretaceous (in areas adjacent to the seacoast). This great age variation is combined with a variety of compositions: Archean rocks belonging to anorthosites, gabbroanorthosites, gabbros, gabbroamphibolites, norites, metagabbro, metapyroxenites, metaperidotites, various gabbroids, granites etc.; Proterozoic rocks represented by gabbros and dolerites; Paleozoic bedrocks represented by Devonian granites, granite-porphyry, diorites, diorite-porphyrite and gabbros. The youngest rocks are from the Mesozoic Cretaceous. Noticeable geological diversity may likely portend to a high taxonomic diversity in the flora.

The surroundings of Ayan is the area that is hard to access. In the vicinities of the settlement, there is only one all-year-round operated road of 12 km length that connects the settlement itself with the local airport. Another way goes to Nelkan Village, located 200 km west from Ayan and can be called the ‘road’ very conditionally, since it is passable only for three-axle heavy-wheeled vehicles and all-terrain (crawler) vehicles and only for two months per year (July and August), with the greater part of the track going directly by the riverbed. These circumstances make the exploration of the area very difficult and, before 1990-th, the works were mostly conducted using helicopter – a practice almost abandoned in the current floristic research in Russia. The maximal distance between localities studied in the present paper is about 60 km (by direct line). The studied localities were visited in the course of pedestrian routes combined with heavy vehicle transportation. The study was undertaken over a period of three weeks at the end of June and the beginning of July of 2019. In total ca. 400 specimens of liverworts and 350 specimens of mosses (not covered in the present account) were collected. The explored localities could be combined into three main areas:

1. The area immediately adjacent to the Ayan Settlement (3–7 km from the centre of the settlement);
2. Low and middle altitudinal belts of the northern part of Pribrezhnyi Range (Unych’ya River catchment);
3. Axial part of Dzhugdzhur Range, in other words, the watershed of the Pacific and Arctic Oceans, mainly in the upper reaches of the Tugorma River (more precisely, in one of its left tributaries).

For more details, the localities are shown in Table 1 and Fig. 1. The mosses were air-dried immediately, whereas the liverwort specimens were kept in the fridge (in anabiosis conditions) until they arrived at the Cryptogamic Biota laboratory in VBGI where they were identified alive by morphological methods and partly photographed (mostly for oil bodies data) and only then dried.

Since the main goal of the work was to reveal the liverwort diversity, the main efforts were assigned to their collection.. In the collection process, we tried to cover all types of vegetation communities and landscapes present in the studied area. In practice, this could not be achieved, due to both the inaccessibility of some geological formations and the time limit allocated for research. Nevertheless, we studied both presumed acidic rocks (meaning the pH of the water extract of the sedimentary products), for example granites, as well as presumed alkaline rocks, from various kinds of metamorphic rocks to limestone. Therefore, we expect the core of the liverwort flora to be revealed.

There are few data on the climate of Ayan surroundings. The weather station in Ayan Settlement provides data on the climate at low elevation. However, the climate parameters in the upper elevation and at the distance from the sea coast should be noticeably different. The Ayan weather station (https://en.climate-data.org/asia/russian-federation/khabarovsk-krai/ayan-718644/) is located at 24 m a.s.l., at a distance less than 500 m from the coast of Ayanskaya Bay of the Sea of Okthotsk. The mean annual temperature there is –3.26°C, the warmest month is August, as it commonly occurs in amphi-oceanic North Pacific areas (thus, not July), when the average temperature reaches 13.0°C, the coldest month is January with temperature average –19.6°C. The mean annual amount of precipitation is 856 mm per year, with a distinct late summer maximum from July to September, when the amount of precipitation exceeds 100 mm per month. The winter precipitation is quite scanty, represented by snow and does not exceed 33 mm per month from November to March. Taking account of available information, the Ayan surroundings climate may be called subarctic suboceanic that indeed corresponds to the dominance of subarctic vegetation in the coastal area, as described below. Going inwards from the Asian mainland, the climate transforms to continental, similar to that widely distributed in the south-eastern flank of the Republic of Yakutiya (bordering Ayano-Maysky administrative district westwards), but the character of changes remains unclear. The climate parameters in the nearest Nelkan Village (314 m a.s.l.) that is behind the main axis of Dzhugdzhur Range westwards (https://en.climate-data.org/asia/russian-federation/khabarovsk-krai/nelkan-296379/) has only 414 mm of precipitation per year (i.e. less than half that of Ayan), the mean annual temperature –6.7°C, with the warmest month being July, 14.4°C and the coldest one being January, –30.4°C. Therefore, the Nelkan Village climate is much more continental than that observed in the Ayan Settlement.

The vegetation in the study area is difficult to describe in distinct definitions of altitudinal belts. In fact, the dominant vegetation is represented by deeply interpenetrating complexes, such as forests composed of Picea ajanensis or Larix cajanderi Mayr, crooked forests (krummholz) composed of Pinus pumila (Pall.) Regel. and Alnus fruticosa Rupr. and mountain tundra and tundra-like communities. Indeed, the area just near to the seacoast provides a variation of communities from tundra (or, at least, almost indistinguishable analogue) at the slopes with severe wind conditions to true boreal dark-coniferous forests in the narrow valleys protected from the dominant winds (Fig. 2a). At elevations 300–400 m a.s.l., all abovementioned vegetation types occupied almost equal proportions. Azonal complexes are represented by vegetation of ice glades, rocky fields (gravelly barrens), swamps and floodplains. Rocky fields (kurum), depending on the topography, may be observed from the seashore, although they begin to dominate at elevations exceeding 500–700 m a.s.l. (Fig. 2b, c). The ice glades are occupied by willow-grass communities, sometimes with some mosses dominating in the cover, but commonly entirely liverworts free. Swamps are very local; we observed a true swamp (with peat deposits production) only once (although, it was quite peculiar due to sluggishly-flowing waters above a limestone sub-base) (Fig. 2d). Therefore, the use of terms such as boreal, subalpine and alpine belt bears only a conditional sense and reflects rather the nearest environment where the specimen was collected.

With the aforementioned reservations, the lower altitudes are dominated by spruce forests formed by Picea ajanensis that are usually mixed with Betula lanata in various proportions. In more drained areas and commonly further from the seacoast, closed to open Larix cajanderii stands (Fig. 3a) with common (almost inevitable) Pinus pumila (Pall.) Regel clumps in the understorey are widely developed. The riversides in wide floodplains of some rivers are occupied by communities composed of Populus suaveolens Fisch., Chosenia arbutifolia (Pall.) A.K. Skvortsov and Salix udensis Trautv. & C.A. Mey. with tall grass cover. Some shrubs, such as Rosa acicularis Lindl., Sorbus sambucifolia (Cham. & Schltdl.) M. Roem. (the latter also often penetrates to the virgin birch forests), are almost confined to these communities. Pure Betula lanata (Regel) V.N. Vassil. stands are quite rare and are usually confined to the gentle slopes moistened by percolating waters near the base of hills and high slopes (Fig. 3b). The ground cover in birch forest is usually grassy, more rarely shrubby.

Pinus pumila – the main dominant plant in the area investigated (by total coverage) – forms well-defined stands (Figs 3b, 4). It almost does not penetrate to the spruce forests, but is widespread as an understorey in Larix forests and commonly so (although with much lesser regularity) in Betula lanata scattered forests. The virgin stands of Pinus pumila start at elevations of 100–200 m a.s.l. and usually remain widespread on the ridgelines of the spurs in the middle elevation, near 500–700 m a.s.l. Above these elevations, as far as to elevations exceeding 1000 m a.s.l., Pinus pumila clumps become more and more scattered, plants become smaller and more certainly better developed in the hollows protected from the wind, with thicker snow cover. Communities of Duschekia fruticosa – another dominant of crooked forests in the Hemiarctic Pacific Asia – are much rarer and likely confined to those places close to the surface or open percolating waters, as well as to the slopes of narrow mountain valleys where a lot of snow is deposited in winter. In addition, shrubby Betula fruticosa clumps sporadically occur near the axial part of Dzhugdzhur Range and form small-sized communities composed of dwarf modifications of the species and show a transition to the true mountain dwarf shrub tundra. Besides communities where Betula fruticosa is a dominant, that species commonly occurs in larch forests, where it reaches a height of 1 m or slightly more. In humid sites near the seacoast, where larch forests are replaced by mixed Picea ajanensis – Betula lanata forests, a continuous morphological transitional series of hybrids between B. fruticosa and B. lanata are observed, these hybrids commonly having a height between 1.5 and 3 m.

Pinus pumila communities are not so much interrupted by mountain tundra (we rarely observed sizable mountain tundra communities), but they are mostly disconnected by rock fields (kurums), both on steep and gently sloping surfaces (Fig. 2b, c). In general, the water deficit (due to the absence of a closely lying waterproof horizon - in other words, when all the moisture after snowmelt or rains almost immediately seeps into the substrate), is the main reason for the absence of closed vegetation at heights exceeding 500–1000 m a.s.l. Mountain tundras are represented by scattered ‘spots’ of 5–20 m in length, less often longer and are located at the places of (or near) percolating water openings. The general organisation of alpine communities is usually exhausted by the following scheme: Sphagnum lenense tufts form the central patch, then they are surrounded by the perimeter (sometimes quite wide strip) of lichen-dwarf shrub (sometimes including dwarfy Pinus pumila) communities and then grade into rocky fields (Fig. 5a). Pure lichen tundra communities (Fig. 5b) are distributed somewhat wider than moss and moss-shrub communities, although also are not common. The special conditions for the development of wet dwarf shrub-moss tundra are observed at the base of slopes at heights exceeding 1100 m a.s.l., in places of firns (dense snow strata lying sometimes over summer) distribution and/or groundwater openings. The severe wind regime on the seacoast, especially in the saddles between the hill-shaped uplifts, leads to the local distribution of tundra-like communities even at altitudes less than 50 m a.s.l. (Figs 5c, d, 6). At a distance from the seacoast, such communities are found everywhere above 300 m a.s.l. and are confined to the most well-drained axial parts of small spurs with clearly blown snow in the winter.

In general, the vegetation of the study area can be identified as subarctic montane. The spruce forests do not dominate even in the lower altitudes and, as a rule, have a great admixture of hem-iarctic Betula lanata. Larix forests have an understorey of Pinus pumila and commonly do not have closed canopy. The larger areas are covered by the ‘subalpine’ shrub Pinus pumila that occurs as understorey or small-sized clumps from lower elevations starting almost from the seacoast and then stretching to the elevations slightly exceeding 1000 m a.s.l., as dwarf and strongly disintegrated patches. The subarctic nature of the flora is also determined by the climate characteristics briefly described above.

One hundred and seventeen species and one subspecies were revealed in the flora of Ayan surroundings, as was defined in the present study. All identification data were input into the electronic herbarium database of the Botanical Garden-Institute FEB RAS (http://botsad.ru/en/herbarium/). All taxa are listed below in alphabetical order. Nomenclature follows Söderström et al. (2016), with the exception for: 1) Solenostomataceae, where the narrow genus concept was adopted; 2) acceptance of Pseudolophozia distinct from Barbilophozia; 3) new conception of Schistochilopsis genus according to Bakalin et al. (2020b) and 4) the narrow species concept in Blepharostoma (the last following Bakalin et al. (2020a)). As only a few specimens of Blepharostoma species (only in pure mats) were checked by DNA analysis, clear taxonomical status of the vast majority of Blepharostoma species found as accompanying taxa (sometimes in small amounts) to other liverworts is not known definitely. In one case (stressed in the checklist), the name Blepharostoma sp. from Kh-58-4-19 means new cryptic taxon discussed in Bakalin et al. (2020a). Cladopodiella is accepted in the old sense, as the genus is different from Odontoschisma. Each taxon is annotated with data on: 1) numbers of collecting localities in accordance with Table 1 and Fig. 1, numbers are given in bold font; 2) altitudinal diapason in the explored area, m above sea level; 3) description of habitat in area treated and accompanying taxa and 4) selected specimens examined field numbers. The subsections are divided by dash.

Anastrophyllum michauxii (F. Weber) H. Buch – 23 – 118 m – Moist decaying wood in Picea ajanensis dominated forest with Betula lanata slight admixture, in the stream valley. With Mylia verrucosa. Kh-55-16-19.

Aneura pinguis (L.) Dumort. – 16, 25, 26 – 22–105 m – Open moist to wet places including humus in the trail in open Larix forest, hummocks in the meadow-like windy community near seacoast with low grasses and shrubs and hollows in eutrophic hypnaceous swamp developed over limestone, with sluggishly-flowing waters. In pure mats or with Mesoptychia rutheana. Kh-48-4-19, Kh-58-9-19, Kh-59-2-19, Kh-59-3-19.

Anthelia juratzkana (Limpr.) Trevis. – 6, 7, 9, 10, 12, 15, 18 – 129–1484 m – Open or rarely partly shaded places in cliffy areas in the forests and alpine belt, most commonly on moist cliffs and rocks, including those near streams, rare in their crevices or humus along watercourses in a variety of communities, such as scattered Betula lanata forest along riverside, Picea ajanensis dominated forest in narrow valley, mosaic of Duschekia and Pinus pumila clumps and mountain tundra vegetation on steep N-facing slopes, moist mossy tundra near stream and alpine vegetation with many rocky outcrops and gravelly barrens on steep N-facing slope to stream. In pure mats or with Blepharostoma sp., Cephalozia bicuspidata, Cladopodiella francisci, Cryptocolea imbricata, Diplophyllum taxifolium, Gymnocolea inflata, Marsupella boeckii, Marsupella emarginata, Nardia geoscyphus, Pleurocladula albescens, Prasanthus suecicus, Protochilopsis grandiretis, Pseudolophozia debiliformis, Pseudolophozia sudetica, Pseudotritomaria heterophylla, Radula prolifera, Scapania sp., Solenostoma obscurum, Sphenolobus minutus and Tetralophozia setiformis. Kh-38-9-19, Kh-39-10-19, Kh-41-6-19, Kh-42-3-19, Kh-44-1-19, Kh-47-26-19, Kh-50-53-19, Kh-56-21-19.

Barbilophozia barbata (Schreb.) Loeske – 2, 3 – 141–294 m – Mesic cliffs and boulders in Larix forest with some clumps of Pinus pumila in understorey and upper reaches of subalpine belt near the top of the hill covered mostly with the mosaic of alpine and subalpine scattered vegetation. In pure mats or with Metzgeria pubescens and Scapania microdonta. Kh-34-2-19, Kh-35-11-19, Kh-35-14-19.

Barbilophozia hatcheri (A. Evans) Loeske – 19 – 780 m – Open mesic cliff crevice at the mountain ridge just above crooked forest line. With Scapania sphaerifera, Sphenolobus saxicola and Tetralophozia setiformis. Kh-51-9-19.

Bazzania denudata (Torr. ex Gottsche, Lindenb. & Nees) Trevis. – 17, 18 – 82–154 m – Open to partly shaded moist cliffs and their crevices in Betula lanata, sometimes scattered forests along riversides. In pure mats or with Bazzania tricrenata, Blepharostoma sp., Blepharostoma trichophyllum, Diplophyllum taxifolium, Douinia plicata, Lepidozia reptans and Metacalypogeia cordifolia. Kh-49-5-19, Kh-50-6-19, Kh-50-44-19, Kh-56-16-19.

Bazzania tricrenata (Wahlenb.) Trevis. – 18 – 129–154 m – Open moist to mesic large riverside N-facing cliffs, with scattered Betula lanata forest. In pure mats or with Bazzania denudata, Calycularia laxa, Cephaloziella sp., Diplophyllum taxifolium, Douinia plicata, Herbertus aff. buchii, Marsupella emarginata, Metacalypogeia cordifolia, Plagiochila porelloides, Solenostoma rossicum, Sphenolobus minutus, Trilophozia quinquedentata and Tritomaria exsecta. Kh-50-23-19, Kh-50-39-19, Kh-50-48-19, Kh-50-56-19, Kh-56-14-19.

Blepharostoma primum Vilnet et Bakalin – 15 – 143 m – Open moist cliff near stream in Picea ajanensis dominating forest in the valley. In pure mats. Kh-47-28-19.

Blepharostoma trichophyllum (L.) Dumort. s. str. – 14, 18 – 54–154 m – Partly shaded moist cliffs and open wet humus near the stream in scattered pure Betula lanata and mixed Picea ajanensis-Betula lanata forests in the valleys. In pure mats. Kh-46-12-19, Kh-50-17-19.

Blepharostoma neglectum "neglecta" Vilnet et Bakalin – 14 – 54 m – Moist fallen decaying tree branch in Picea ajanensis-Betula lanata forest in the valley. In pure mats. Kh-46-3-19.

Blepharostoma sp. (indefinite hybrid taxon with B. trichophyllum as one parent, cf. Bakalin et al. 2020) – 25 – 22 m – Partly shaded moist humus developed over limestone on the trail in open Larix forest in small stream valley. With Eocalypogeia schusteriana, Mesoptychia gillmanii and Scapania gymnostomophila. Kh-58-4-19.

Calycularia laxa Lindb. & Arnell – 6, 7, 11, 15, 18 – 129–1261 m – Partly shaded crevices in the cliffs and between boulders, also those filled with fine soil. Boreal forests including pure stands by Picea ajanensis, Betula lanata and their mixed variants, large riverside N-facing cliffs with scattered Betula lanata; mosaic of Duschekia and Pinus pumila clumps and mountain tundra vegetation on steep slopes; dwarf shrub-lichen tundra with gravelly barrens on steep N-facing slopes. In pure mats or with Bazzania tricrenata, Diplophyllum taxifolium, Lophozia sp., Marsupella emarginata, Sphenolobus minutus, Sphenolobus saxicola and Trilophozia quinquedentata. Kh-38-12-19, Kh-39-5-19, Kh-43-4-19, Kh-47-15-19, Kh-50-35-19, Kh-56-1-19.

Calypogeia integristipula Steph. – 1, 15 – 11–143 m – Partly shaded moist humus on slopes, decaying wood and cliffs near stream in Picea ajanensis dominating forest in narrow valley. With Blepharostoma sp., Cephalozia bicuspidata, Douinia plicata, Fuscocephaloziopsis lunulifolia, Lepidozia reptans, Lophozia sp., Scapania parvifolia, Schistochilopsis incisa and Sphenolobus minutus. Kh-33-11-19, Kh-47-5-19, Kh-47-14-19, Kh-47-16-19, Kh-47-18-19.

Calypogeia muelleriana (Schiffn.) Müll. Frib. – 11 – 1148 m – Over wet Sphagnum mat in alpine belt with scattered vegetation over percolating water. With Lophozia sp., Scapania parvifolia and Sphenolobus minutus. Kh-43-11-19.

Calypogeia neogaea (R.M. Schust.) Bakalin – 6 – 904 m – Over moist Sphagnum mat on the slope in mosaic of Duschekia and Pinus pumila clumps and mountain tundra vegetation. With Cephalozia sp. and Neoorthocaulis binsteadii. Kh-38-7-19.

Calypogeia suecica (Arnell & J. Perss.) Müll. Frib. – 23 – 118 m – Moist decaying wood in Picea forest with scattered Betula lanata admixture in the valley. With Cephalozia bicuspidata, Lophozia guttulata and Mylia verrucosa. Kh-55-10b-19.

Cephalozia bicuspidata (L.) Dumort. – 1, 7, 9, 11, 14, 15, 23, 26 – 11–1484 m – Moist humus on the trails, open wet peat, clayish soil on steep slopes, rarer in dense moist mossy hummocks. Mixed Picea ajanensis-Betula lanata forests, through subalpine belt where near Duschekia and Pinus pumila clumps to alpine belt with scattered vegetation, once in eutrophic hypnaceous swamp developed over limestone, with sluggishly-flowing water above. In pure mats or with Anthelia juratzkana, Calypogeia integristipula, Calypogeia suecica, Diplophyllum taxifolium, Lophozia guttulata, Lophozia silvicoloides, Lophozia sp., Marsupella emarginata, Mylia verrucosa, Nardia geoscyphus, Prasanthus suecicus, Scapania irrigua, Scapania parvifolia, Schistochilopsis incisa, Solenostoma obscurum, Sphenolobus minutus and Trilophozia quinquedentata. Kh-33-7-19, Kh-39-9-19, Kh-41-6-19, Kh-43-6-19, Kh-46-1-19, Kh-47-22-19, Kh-55-10-19, Kh-59-1-19.

Cephaloziella divaricata (Sm.) Schiffn. – 17, 19 – 82–780 m – Open moist cliffs and their crevices in large riverside S-facing cliffs in scattered Picea ajanensis forest and cliffs on ridgeline of small spur in crooked forest belt. With Mannia fragrans, Mannia fragrans var. fragrans, Mannia sibirica and Riccia sorocarpa. Kh-49-11-19, Kh-49-21-19, Kh-49-22-19, Kh-49-22a-19, Kh-51-2-19.

Cephaloziella varians (Gottsche) Steph. – 9, 11 – 1148–1484 m – Open mesic sandy soil on slope in alpine belt with sparse vegetation. With Cryptocolea imbricata, Fuscocephaloziopsis pleniceps, Isopaches bicrenatus, Riccardia palmata, Scapania sp. and Protochilopsis grandiretis. Kh-41-9-19, Kh-43-1-19.

Cladopodiella francisci (Hook.) Jørg. – 12 – 1109 m – Over humus on wet mossy bank of the stream in moist mossy tundra. With Anthelia juratzkana, Pseudolophozia sudetica. Kh-44-4-19.

Conocephalum salebrosum Szweyk., Buczk. & Odrzyk. – 18, 25 – 22–154 m – Open to partly shaded moist humus covering rocks in large N-facing conglomerate cliffs with scattered Betula lanata along riverside and in open Larix forest in small stream valley with many limestone boulders in the streambed. In pure mats or with Plagiochila porelloides. Kh-56-5-19, Kh-58-8-19.

Crossocalyx hellerianus (Nees ex Lindenb.) Meyl. – 3, 23 – 118–294 m – Partly shaded moist decaying decorticated fallen tree trunk in Larix forest with some clumps of Pinus pumila in understorey. With Lepidozia reptans, Lophozia sp., Mylia verrucosa and Ptilidium pulcherrimum. Kh-35-8-19, Kh-35-9-19, Kh-55-8-19.

Cryptocolea imbricata R.M. Schust. – 9, 10 – 1478–1484 m – Open wet humus along stream and moist sandy soil on slope, only in the areas of distribution of rocks of basic reaction in alpine belt with scattered vegetation. With Anthelia juratzkana, Cephaloziella varians, Fuscocephaloziopsis pleniceps, Pseudotritomaria heterophylla, Radula prolifera, Riccardia palmata, Scapania sp. and Protochilopsis grandiretis. Kh-41-3-19, Kh-42-3-19.

Diplophyllum sibiricum Bakalin et Vilnet – 17 – 82 m – Open moist cliff in large riverside S-facing cliffs with scattered Betula lanata. With Diplophyllum taxifolium, Marsupella emarginata, Scapania mucronata and Schistochilopsis sp. Kh-49-16-19.

Diplophyllum taxifolium (Wahlenb.) Dumort. – 2, 7, 15, 17, 18 – 82–1261 m – Open to partly shaded moist cliffs and boulders in Picea ajanensis forests, large riverside cliffs with scattered Betula lanata and alpine vegetation with many rocky outcrops and gravelly barrens on steep N-facing slope. In pure mats or with Anthelia juratzkana, Bazzania denudata, Bazzania tricrenata, Calycularia laxa, Cephalozia bicuspidata, Diplophyllum sibiricum, Douinia plicata, Frullania subarctica, Gymnomitrion corallioides, Lepidozia reptans, Marsupella boeckii, Marsupella emarginata, Metacalypogeia cordifolia, Metzgeria pubescens, Nardia geoscyphus, Plagiochila porelloides, Pleurocladula albescens, Pseudolophozia sudetica, Scapania crassiretis, Scapania mucronata, Schistochilopsis incisa, Schistochilopsis sp., Solenostoma obscurum, Sphenolobus minutus and Trilophozia quinquedentata. Kh-34-3-19, Kh-39-12-19, Kh-47-8-19, Kh-49-18-19, Kh-50-42-19.

Douinia plicata (Lindb.) Konstant. et Vilnet – 1, 14, 15, 17, 18, 23 – 11–154 m – Partly shaded moist decaying wood, moist cliffs, rarely clayish soil on steep slopes; from various coniferous, mixed and Betula lanata forests to subalpine belt with many Duschekia and Pinus pumila clumps. In pure mats or with Bazzania denudata, Bazzania tricrenata, Blepharostoma trichophyllum, Calypogeia integristipula, Diplophyllum taxifolium, Fuscocephaloziopsis lunulifolia, Lepidozia reptans, Lophozia sp., Marsupella emarginata, Metacalypogeia cordifolia, Metzgeria pubescens, Schistochilopsis incisa and Sphenolobus minutus. Kh-33-5-19, Kh-46-17-19, Kh-47-14-19, Kh-49-24-19, Kh-50-23-19, Kh-55-19-19, Kh-56-17-19.

Eocalypogeia schusteriana (S. Hatt. & Mizut.) R.M. Schust. – 18, 24 – 34–154 m – Open to, rarely, partly shaded crevices in cliffs of basic to neutral reaction (mostly metamorphic rocks, rarely pure limestone), in windy tundra-like communities near seacoast and scattered Betula lanata stands along sea coast and riverside. With Blepharostoma sp., Jungermannia afoninae, Mesoptychia badensis, Mesoptychia gillmanii, Preissia quadrata and Scapania gymnostomophila. Kh-50-16-19, Kh-50-34-19, Kh-57-8-19, Kh-57-11-19, Kh-57-19-19, Kh-57-23-19.

Eremonotus myriocarpus (Carrington) Pearson – 18 – 129–154 m – Open moist cliff crevices in large N-facing conglomerate cliffs with scattered Betula lanata along riverside. With Sauteria alpina and Solenostoma obscurum. Kh-56-10a-19, Kh-56-12-19.

Frullania bolanderi Austin – 4, 15 – 143–377 m – Partly shaded Betula lanata and Salix udensis trunks in valley forests near streams and rivers. In pure mats. Kh-36-11-19, Kh-47-12-19, Kh-47-13-19.

Frullania davurica Hampe – 18, 19 – 129–780 m – Open mesic cliffs on riverside with scattered Betula lanata and ridgeline (crooked forest belt) of small ridge with many rocky outcrops, gravelly barrens and Pinus pumila clumps. In pure mats or with Frullania ignatovii, Frullania subarctica and Trilophozia quinquedentata. Kh-50-27-19, Kh-50-28-19, Kh-51-8-19.

Frullania ignatovii Sofronova, Mamontov & Potemkin – 18 – 129–154 m – Open mesic cliffs in large riverside N-facing cliffs with scattered Betula lanata. In pure mats or with Frullania davurica. Kh-50-26-19, Kh-50-29-19.

Frullania subarctica Vilnet, Borovich. et Bakalin – 18 – 129–154 m – Open moist cliffs in large riverside N-facing cliffs with scattered Betula lanata. In pure mats or with Diplophyllum taxifolium, Frullania davurica, Frullania ignatovii, Gymnomitrion corallioides, Herbertus aff. buchii, Plagiochila porelloides and Scapania crassiretis. Kh-50-43a-19, Kh-50-47-19, Kh-50-55-19, Kh-56-26-19.

Fuscocephaloziopsis leucantha (Spruce) Váňa et L.Söderstr. – 23 – 118 m – Moist decaying wood in Picea forest with scattered Betula lanata in the valley. With Lophozia guttulata. Kh-55-10a-19.

Fuscocephaloziopsis lunulifolia (Dumort.) Váňa et L.Söderstr. – 15, 23 – 118–143 m – Moist decaying wood, moist humus on trails and humus covering cliffs in Picea forest also that with the admixture of Betula lanata. With Blepharostoma sp., Calypogeia integristipula, Douinia plicata, Lepidozia reptans, Lophozia sp., Mylia verrucosa, Schistochilopsis incisa and Schistochilopsis incisa. Kh-47-2-19, Kh-47-14a-19, Kh-55-3-19.

Fuscocephaloziopsis pachycaulis (R.M.Schust.) Váňa et L.Söderstr. – 15 – 118 m – Open moist cliff near stream in Picea ajanensis dominating forest in narrow valley. In pure mats. Kh-47-23-19.

Fuscocephaloziopsis pleniceps (Austin) Váňa & L. Söderstr. – 9, 12 – 1109–1484 m – Over humus on wet mossy bank of the stream in moist mossy tundra. With Cephaloziella varians, Cryptocolea imbricata, Mylia anomala, Riccardia palmata, Scapania sp. and Protochilopsis grandiretis. Kh-41-9-19, Kh-44-2-19, Kh-44-8-19.

Gymnocolea inflata (Huds.) Dumort. – 6, 12 – 904–1109 m – Mossy banks and open wet cliffs near streams in subalpine belt with mosaic of Duschekia and Pinus pumila clumps and mossy tundra. With Anthelia juratzkana, Pleurocladula albescens, Protochilopsis grandiretis, Schljakovia kunzeana and Tetralophozia setiformis. Kh-38-10-19, Kh-44-5-19, Kh-44-13-19.

Gymnomitrion commutatum (Limpr.) Schiffn. – 6, 8, 9, 19 – 780–1484 m – Mesic to moist sandy soil and humus on steep slopes and solifluction spots, rarely open moist cliffs, in subalpine and alpine belts. In pure mats and with Gymnomitrion concinnatum. Kh-38-4-19, Kh-40-9-19, Kh-41-1-19, Kh-51-4-19.

Gymnomitrion concinnatum (Lightf.) Corda – 7, 8 – 1261–1328 m – Open moist cliffs in alpine belt with scattered vegetation and many rocky outcrops and gravelly barrens on steep N-facing slope. With Gymnomitrion commutatum, Gymnomitrion corallioides and Pseudolophozia sudetica. Kh-39-3-19, Kh-40-4-19.

Gymnomitrion corallioides Nees – 2, 6, 7, 8, 18, 19 – 129–1328 m – Moist to mesic cliffs and their crevices, rarely dense sandy soil on slopes; in large riverside N-facing cliffs with scattered Betula lanata; subalpine belt with mosaic of Duschekia and Pinus pumila clumps and mountain tundra vegetation on steep N-facing slope and alpine belt with scattered vegetation with many rocky outcrops and gravelly barrens moistened by neutral to basic reaction percolating water on steep N-facing slope. In pure mats and with Diplophyllum taxifolium, Frullania subarctica, Gymnomitrion concinnatum, Pseudolophozia sudetica, Scapania crassiretis and Sphenolobus minutus. Kh-34-3-19, Kh-38-3-19, Kh-39-3-19, Kh-40-3-19, Kh-50-52-19, Kh-51-10-19.

Herbertus aff. buchii Juslen – 18, 22 – 119–154 m – Kh-50-1-19, Kh-50-25-19, Kh-50-43-19, Kh-54-4-19, Kh-56-27-19, Kh-56-28-19. Open moist cliffs along riverside with scattered Betula lanata, rarely moist boulders in waterfall canyon in subalpine belt. In pure mats or with Bazzania tricrenata, Cephaloziella sp., Frullania subarctica, Marsupella emarginata, Metacalypogeia cordifolia, Plagiochila porelloides, Scapania crassiretis, Solenostoma rossicum and Sphenolobus minutus.

Isopaches bicrenatus (Schmidel) H. Buch – 10, 11 – 1148–1478 m – Open mesic clayish soil on slope with scattered alpine vegetation, many rocky outcrops and gravelly barrens moistened by neutral to basic reaction percolating water on steep N-facing slope. With Cephaloziella varians. Kh-42-1-19, Kh-43-1-19.

Jungermannia afoninae Mamontov, Konstant. & Vilnet – 17, 21, 24 – 34–235 m – Open to partly shaded moist cliff crevices and niches in lower elevations: large riverside cliffs with scattered Betula lanata, windy tundra-like communities developed over limestone and deep canyons near waterfalls. In pure mats and with Eocalypogeia schusteriana, Mesoptychia badensis, Preissia quadrata and Scapania gymnostomophila. Kh-49-1-19, Kh-49-14-19, Kh-53-2-19, Kh-57-1-19, Kh-57-12-19, Kh-57-13-19.

Jungermannia pumila With. – 21 – 235 m – Open wet boulder near stream in deep canyon with small waterfall, in subalpine belt with scattered Pinus pumila clumps in surroundings. With Scapania irrigua. Kh-53-7-19.

Lejeunea alaskana (R.M. Schust. & Steere) Inoue & Steere – 18 – 129–154 m – Open moist cliff in large N-facing conglomerate rocky outcrops with scattered Betula lanata along riverside. In pure mats. Kh-56-24-19.

Lepidozia reptans (L.) Dumort. – 15, 17, 21, 24 – 34–235 m – Moist fallen decaying decorticated tree trunks, decaying stumps, moist cliffs and their crevices, everywhere in part shade; in forest belt, including Picea ajanensis forest with scattered Betula lanata trees, Picea ajanensis-Betula lanata forest in the valley with some Salix udensis near stream, Larix forest in narrow valley and scattered Betula lanata stand in large riverside cliffs. With Bazzania denudata, Blepharostoma sp., Blepharostoma trichophyllum, Calypogeia integristipula, Crossocalyx hellerianus, Diplophyllum taxifolium, Douinia plicata, Fuscocephaloziopsis lunulifolia, Lophozia guttulata, Lophozia sp., Metacalypogeia cordifolia, Mylia verrucosa, Schistochilopsis incisa, Sphenolobus minutus and Tritomaria exsecta. Kh-36-3-19, Kh-46-7-19, Kh-47-16-19, Kh-49-6-19, Kh-50-7-19, Kh-55-15-19, Kh-55-18-19.

Lophocolea heterophylla (Schrad.) Dumort. – 4 – 377 m – Partly shaded moist fallen decaying decorticated tree trunk in wide floodplain with solitary Populus suavealons and Salix udensis trees near streambed. With Blepharostoma sp. Kh-36-9-19.

Lophocolea minor Nees – 1, 4, 25 – 11–377 m – Partly shaded moist humus along trail, boulders on slopes, fallen decaying tree trunks; in open Larix forests, subalpine belt with many Duschekia and Pinus pumila clumps, floodplain Populus suavealons and Salix udensis forest near streambed. In pure mats and with Mesoptychia aff. heterocolpos. Kh-33-3a-19, Kh-36-10-19, Kh-58-3-19.

Lophozia guttulata (Lindb. & Arnell) A. Evans – 14, 15, 23 – 54–143 m – Partly shaded moist decaying wood, rarely humus covered boulders in Picea ajanensis and Betula lanata pure stands and their mixtures. With Calypogeia suecica, Cephalozia bicuspidata, Fuscocephaloziopsis leucantha, Lepidozia reptans, Lophozia silvicola and Mylia verrucosa. Kh-46-8-19, Kh-47-4-19, Kh-55-10-19, Kh-55-14-19.

Lophozia lantratoviae Bakalin – 18, 20 – 129–200 m – Open and partly shaded cliffs and their crevices along streams and riversides in scattered Betula lanata forest and floodplain Salix udensis-Chosenia arbutifolia-Populus suaveolens stand. With Blepharostoma sp., Mesoptychia heterocolpos, Scapania gymnostomophila, Scapania rufidula and Trilophozia quinquedentata, Tritomaria scitula. Kh-50-32-19, Kh-52-1a-19, Kh-56-13-19, Kh-56-19-19.

Lophozia silvicola H. Buch – 3, 15, 18 – 129–294 m – Open to partly shaded moist humus (also that covering rocks) along streams and rivers in scattered Betula lanata forest and flood plain communities dominated by Populus suavealons and Salix udensis. In pure mats or with Lophozia guttulata. Kh-35-2-19, Kh-47-4-19, Kh-50-10-19.

Lophozia silvicoloides N. Kitag. – 1, 3 – 11–294 m – Partly shaded moist clayish soil on steep slope and decaying wood; in Larix forest in narrow valley and subalpine belt with clumps of Duschekia and Pinus pumila. With Cephalozia bicuspidata and Sphenolobus minutus. Kh-33-8-19, Kh-35-7-19.

Lophozia ventricosa (Dicks.) Dumort. – 14, 23 – 54–118 m – Moist decaying wood and partly shaded moist humus near stream in Picea ajanensis–Betula lanata forests, also those near streams with scattered Salix udensis. In pure mats or with Mylia verrucosa. Kh-46-15-19, Kh-55-7-19.

Lophoziopsis excisa (Dicks.) Konstant. & Vilnet – 17 – 82 m – Open moist crevices in large riverside S-facing cliffs with scattered Betula lanata. In pure mats. Kh-49-9-19.

Lophoziopsis longidens (Lindb.) Konstant. et Vilnet – 4 – 377 m – Partly shaded lying Pinus pumila branches in Larix forest with scattered Pinus pumila in understorey. In pure mats. Kh-36-4-19.

Mannia androgyna (L.) Evans – 17 – 82 m – Partly shaded moist crevice in large riverside S-facing cliffs in forest belt. In pure mats. Kh-49-2-19.

Mannia fragrans (Balb.) Frye & L. Clark – 17 – 82 m – Open moist crevice in large riverside S-facing cliffs in forest belt. In pure mats or with Cephaloziella divaricata. Kh-49-10-19, Kh-49-12-19

Mannia pilosa (Hornem.) Frye & L. Clark – 18, 24, 27, 28 – 5–154 m – Open moist cliff crevices partly filled with humus; in large riverside basic conglomerate S-facing cliffs surrounded by scattered Betula lanata and limestone outcrops surrounded by tundra-like community. In pure mats or with Mesoptychia sp., Preissia quadrata and Scapania gymnostomophila. Kh-50-4-19, Kh-50-5-19, Kh-50-31-19, Kh-57-4-19, Kh-57-5-19, Kh-60-3-19, Kh-61-2-19.

Mannia sibirica (K. Müller) Frye & L. Clark – 17 – 82 m – Open moist crevice in large riverside S-facing cliffs with scattered Betula lanata. With Cephaloziella divaricata, Riccia sorocarpa and Riccia bifurca. Kh-49-3-19, Kh-49-13-19.

Marchantia alpestris (Nees) Burgeff – 27 – 5 m – Partly shaded moist clay in deep niche in sedimentary N-facing rocky outcrops of basic reaction along seacoast. In pure mats. Kh-60-1-19.

Marsupella boeckii (Austin) Lindb. ex Kaal. – 15 – 143 m – Open moist boulders and cliffs near stream in Picea ajanensis dominating forest in narrow valley. With Anthelia juratzkana, Diplophyllum taxifolium, Nardia geoscyphus, Pleurocladula albescens, Pseudolophozia sudetica and Schistochilopsis incisa. Kh-47-1-19, Kh-47-19-19, Kh-47-24-19.

Marsupella emarginata (Ehrh.) Dumort. – 7, 8, 15, 17, 18, 21 – 82–1328 m – Open to partly shaded moist cliffs near streams and rivers as well as in waterfall canyons, from Picea ajanensis forests to alpine belt. In pure mats or with Anthelia juratzkana, Bazzania tricrenata, Blepharostoma sp., Calycularia laxa, Cephalozia bicuspidata, Diplophyllum sibiricum, Diplophyllum taxifolium, Douinia plicata, Herbertus aff. buchii, Metacalypogeia cordifolia, Pleurocladula albescens, Pseudolophozia sudetica, Scapania mucronata, Schistochilopsis incisa, Schistochilopsis sp., Sphenolobus minutus and Trilophozia quinquedentata. Kh-39-6-19, Kh-39-11-19, Kh-40-5-19, Kh-40-7-19, Kh-47-25-19, Kh-49-17-19, Kh-50-24-19, Kh-50-40-19, Kh-50-41-19, Kh-53-1-19, Kh-56-18-19, Kh-56-25-19.

Marsupella sprucei (Limpr.) Bernet – 6, 8 – 904–1328 m – Open moist peaty and sandy soil on N-facing slopes in alpine and subalpine belts. In pure mats. Kh-38-1-19, Kh-40-1-19.

Mesoptychia badensis (Gottsche ex Rabenh.) L. Söderstr. & Váňa – 24 – 34 m – Open moist limestone cliffs also those covered with thin layer of humus, surrounded by tundra-like community in low elevation near seacoast. In pure mats or with Eocalypogeia schusteriana, Jungermannia afoninae and Scapania gymnostomophila. Kh-57-6-19, Kh-57-14-19, Kh-57-15-19.

Mesoptychia gillmanii (Austin) L. Söderstr. & Váňa – 24 – 34 m – Open moist clayish soil on steep slope with many limestone outcrops surrounded by tundra-like community near seacoast. With Blepharostoma sp., Eocalypogeia schusteriana, Plagiochila satoi and Preissia quadrata. Kh-57-16-19, Kh-57-17-19.

Mesoptychia heterocolpos (Thed.) L. Söderstr. & Váňa – 17, 18, 25 – 22–154 m – Open moist clayish soil along watercourse, moist cliff crevices and, rarely, partly shaded decaying wood in scattered Betula lanata and Larix cajanderi forests. In pure mats and with Blepharostoma sp., Blepharostoma trichophyllum, Lophozia lantratoviae, Preissia quadrata, Trilophozia quinquedentata and Tritomaria scitula. Kh-49-23-19, Kh-50-33-19, Kh-58-1-19.

Mesoptychia rutheana (Limpr.) L. Söderstr. & Váňa – 26 – 91 m – Open wet hummocks and hollows in eutrophic hypnaceous swamp with sluggishly-flowing waters, developed over limestone. In pure mats and with Aneura pinguis. Kh-59-4-19, Kh-59-5-19, Kh-59-6-19.

Metacalypogeia cordifolia (Stephani) Inoue – 17, 18, 22 – 82–154 m – Open to partly shaded moist cliffs in large riverside variously-faced cliff massifs with scattered Betula lanata. With Bazzania denudata, Bazzania tricrenata, Blepharostoma sp., Blepharostoma trichophyllum, Cephaloziella sp., Diplophyllum taxifolium, Douinia plicata, Herbertus aff. buchii, Lepidozia reptans, Marsupella emarginata, Plagiochila porelloides, Solenostoma rossicum, Sphenolobus minutus and Tritomaria exsecta. Kh-49-4-19, Kh-49-7-19, Kh-49-20-19, Kh-50-19-19, Kh-50-36-19, Kh-50-42-19, Kh-54-1-19.

Metzgeria pubescens (Schrank) Raddi –18, 19 – 129–780 m – Open moist to mesic cliffs and their crevices at ridgeline surrounded by subalpine vegetation and cliff-like massif at riverside in low elevation, once on thin Sorbus trunk base in scattered Betula lanata forest. In pure mats or with Barbilophozia barbata, Diplophyllum taxifolium, Douinia plicata and Plagiochila porelloides. Kh-50-13-19, Kh-50-38-19, Kh-51-11-19, Kh-56-17-19.

Mylia anomala (Hook.) Gray – 12 – 1109 m – Over humus on wet mossy stream bank in moist mossy tundra in alpine belt. With Fuscocephaloziopsis pleniceps and Protochilopsis grandiretis. Kh-44-3-19, Kh-44-10-19.

Mylia verrucosa Lindb. – 15, 23 – 118–143 m – Partly shaded moist decaying wood and, rarely, humus on the trail-side in Picea ajanensis pure or with Betula lanata admixture forests. With Anastrophyllum michauxii, Blepharostoma sp., Calypogeia suecica, Cephalozia bicuspidata, Crossocalyx hellerianus, Fuscocephaloziopsis lunulifolia, Lepidozia reptans, Lophozia guttulata, Lophozia sp., Lophozia ventricosa and Schistochilopsis incisa. Kh-47-3-19, Kh-47-17-19, Kh-55-1-19, Kh-55-11-19.

Nardia geoscyphus (De Not.) Lindb. – 15 – 143 m – Open moist cliffs near stream and humus covering rocks on slope in Picea ajanensis dominating forest in narrow valley. With Anthelia juratzkana, Cephalozia bicuspidata, Diplophyllum taxifolium, Marsupella boeckii, Pleurocladula albescens Pseudolophozia sudetica. Kh-47-7-19, Kh-47-20-19, Kh-47-21-19.

Neoorthocaulis binsteadii (Kaal.) L. Söderstr., De Roo & Hedd. – 6, 11 – 904–1148 m – Open moist Sphagnum mats in alpine and subalpine belts, in the latter case surrounded by mosaic of Duschekia and Pinus pumila clumps and mountain tundra vegetation on steep N-facing slope. With Calypogeia neogaea, Cephalozia sp., Lophozia sp. and Sphenolobus minutus. Kh-38-5-19, Kh-43-8-19.

Pellia endiviifolia (Dicks.) Dumort. – 25 – 22 m – Open moist humus along stream with many limestone boulders in the streambed in open Larix forest in the valley. In pure mats. Kh-58-2-19.

Pellia neesiana (Gottsche) Limpr. – 15 – 143 m – Partly shaded moist humus on slope in Picea ajanensis dominating forest in narrow valley. With Blepharostoma trichophyllum , Plagiochila porelloides and Scapania sp. Kh-46-8-19, Kh-47-6-19.

Peltolepis quadrata (Saut.) Müll. Frib. – 18 – 129–154 m – Open wet cliff crevice in large N-facing conglomerate cliffs with scattered Betula lanata along riverside. With Plagiochila porelloides. Kh-56-4-19.

Plagiochila arctica Bryhn & Kaal. – 9 – 1484 m – Moist humus moistened by basic reaction percolating water on steep N-facing slope in alpine belt. With Scapania crassiretis. Kh-41-8-19.

Plagiochila porelloides (Torr. ex Nees) Lindenb. – 1, 14, 16, 18, 23, 27 – 5–154 m – Open to partly shaded moist to wet boulders (also those along watercourses) and humus on slopes, mesic cliffs, rarely decaying wood, in various types of forests (dominated by Larix cajanderi and Picea ajanensis, with a certain admixture of Betula lanata), subalpine clumps of Duschekia and Pinus pumila, also tundra-like communities along seacoast, once on moist hummock on the windy meadow in a small saddle. In pure mats or with Bazzania tricrenata, Blepharostoma sp., Blepharostoma trichophyllum, Conocephalum salebrosum, Diplophyllum taxifolium, Frullania subarctica, Herbertus aff. buchii, Metacalypogeia cordifolia, Metzgeria pubescens, Pellia neesiana, Peltolepis quadrata, Scapania sp., Solenostoma rossicum andTritomaria exsecta. Kh-33-1-19, Kh-46-9-19, Kh-48-3-19, Kh-50-50-19, Kh-55-4-19, Kh-56-2-19, Kh-58-5-19, Kh-58-7-19, Kh-60-2-19.

Plagiochila satoi S. Hatt. – 17, 24 – 24–82 m – Open moist humus between limestone outcrops on steep slope surrounded by tundra-like community developed as the result of severe wind conditions. With Mesoptychia gillmanii and Preissia quadrata. Kh-49-8-19, Kh-57-20-19.

Pleurocladula albescens (Hook.) Grolle – 12, 15 – 143–1109 m – Open humus banks and cliffs near stream; from low to high elevations: in Picea ajanensis forest in narrow valley and moist mossy tundra. With Anthelia juratzkana, Blepharostoma sp., Diplophyllum taxifolium, Gymnocolea inflata, Marsupella boeckii, Marsupella emarginata, Nardia geoscyphus, Protochilopsis grandiretis, Pseudolophozia debiliformis, Pseudolophozia sudetica, Scapania parvifolia, Scapania sp. and Trilophozia quinquedentata. Kh-44-7-19, Kh-44-9-19, Kh-47-20a-19.

Porella vernicosa Lindb. – 18 – 129–154 m – Open mesic cliff crevice in large riverside N-facing cliffs with scattered Betula lanata in low elevations. In pure mats. Kh-50-2-19, Kh-50-3-19.

Prasanthus suecicus (Gottsche) Lindb. – 9 – 1484 m – Open wet humificated soil moistened by percolating waters of neutral reaction near small temporary stream in alpine belt with scattered vegetation, on steep N-facing slope. With Anthelia juratzkana and Cephalozia bicuspidata. Kh-41-6-19.

Preissia quadrata (Scop.) Nees – 10, 16, 18, 22, 24, 28 – 5–1478 m – Open to partly shaded moist cliff crevices (including those of limestone) filled with humus or fine soil, rarely open wet humus, moistened with percolating waters of neutral reaction, near temporary stream; in all elevation belts. In pure mats or with Blepharostoma sp., Eocalypogeia schusteriana, Jungermannia afoninae, Mannia pilosa, Mesoptychia gillmanii, Mesoptychia heterocolpos, Plagiochila satoi, Scapania gymnostomophila, Trilophozia quinquedentata and Tritomaria quinquedentata. Kh-42-2-19, Kh-48-2-19, Kh-50-14-19, Kh-50-18-19, Kh-50-30-19, Kh-54-2-19, Kh-57-21-19, Kh-61-3-19.

Protochilopsis grandiretis (Lindb. ex Kaal.) A.V. Troitsky, Bakalin & Fedosov – 6, 9, 12 – 904–1484 m – Open moist peat on slope in subalpine belt amongst mosaic of Duschekia and Pinus pumila clumps and mountain tundra vegetation on steep N-facing slope to stream. With Cephaloziella varians, Cryptocolea imbricata, Fuscocephaloziopsis pleniceps, Gymnocolea inflata, Mylia anomala, Pleurocladula albescens, Riccardia palmata and Scapania sp. Kh-38-1-19, Kh-41-9-19, Kh-44-3-19.

Pseudolophozia debiliformis (R.M. Schust. & Damsh.) Konstant. & Vilnet. – 12 – 1109 m – Over humus on wet mossy stream bank in moist mossy tundra. With Anthelia juratzkana and Pleurocladula albescens. Kh-44-1-19.

Pseudolophozia sudetica (Nees ex Huebener) Konstant. & Vilnet – 4, 7, 12, 15, 17, 21 – 82–1261 m – Open to partly shaded moist cliffs and boulders, including those near stream and waterfall canyon; in open Larix cajanderi forest or scattered Betula lanata stands. With Anthelia juratzkana, Blepharostoma sp., Cladopodiella francisci, Diplophyllum taxifolium, Gymnomitrion concinnatum, Gymnomitrion corallioides, Marsupella boeckii, Marsupella emarginata, Nardia geoscyphus, Pleurocladula albescens, Scapania crassiretis, Scapania sp., Schistochilopsis incisa and Trilophozia quinquedentata. Kh-36-7-19, Kh-39-3-19, Kh-44-9-19, Kh-47-21-19, Kh-49-19a-19, Kh-53-4-19.

Pseudotritomaria heterophylla (R.M. Schust.) Konstant. & Vilnet – 9, 10 – 1478–1484 m – Open moist sandy soil and humus moistened by percolating water of basic reaction, also those near small temporary stream; in alpine belt with scattered vegetation. With Anthelia juratzkana, Cryptocolea imbricata and Scapania parvifolia. Kh-41-5-19, Kh-42-3a-19.

Ptilidium ciliare (L.) Hampe – 3, 6, 9, 10, 19 – 11–1484 m – Open mesic boulders and cliffs in forest and subalpine belts, rarely wet hollows between mossy hummock on slope amongst subalpine vegetation by a mosaic of Duschekia and Pinus pumila clumps and mountain tundra. In pure mats or with Radula prolifera and Scapania crassiretis. Kh-35-5-19, Kh-38-8-19, Kh-41-7-19, Kh-42-4-19, Kh-51-7-19.

Ptilidium pulcherrimum (Weber) Vain. – 1, 3, 6, 14, 23 – 11–904 m – Partly shaded moist decaying wood in Picea ajanensis (sometimes with Betula lanata admixture) forests, Pinus pumila living branches in subalpine belt, rarely moist humus near stream in Larix cajanderi forest with Pinus pumila understorey. In pure mats or with Crossocalyx hellerianus. Kh-33-2-19, Kh-35-1-19, Kh-46-5-19, Kh-55-9-19.

Radula complanata (L.) Dumort. – 18, 23 – 129–154 m – Partly shaded moist decaying wood in Picea ajanensis with scattered Betula lanata forest, open to partly shaded moist cliffs and their crevices in large N-facing conglomerate cliffs with scattered Betula lanata along riverside. In pure mats. Kh-50-15-19, Kh-55-6-19, Kh-56-23-19.

Radula prolifera Arnell – 10 – 1478 m – Open sandy soil moistened by percolate waters of basic reaction on slope with scattered vegetation in alpine belt. With Anthelia juratzkana, Cryptocolea imbricata and Ptilidium ciliare. Kh-42-4-19.

Reboulia hemisphaerica (L.) Raddi subsp. orientalis R.M. Schust. – 18, 21 – 129–235 m – Open to partly shaded moist cliff crevices and caves in large rocky outcrops along riverside and waterfall canyon at low elevation, surrounded by scattered Betula lanata stands. The second of the cited specimens is sterile and referred to this subspecies tentatively. In pure mats. Kh-50-9-19, Kh-53-3-19.

Riccardia palmata (Hedw.) Carruth. – 9 – 1484 m – Over humus moistened by percolating waters of neutral reaction, near temporary stream on N-facing slope in alpine belt with scattered vegetation. With Cephaloziella varians, Cryptocolea imbricata, Fuscocephaloziopsis pleniceps, Scapania sp. and Protochilopsis grandiretis. Kh-41-9-19.

Riccia bifurca Hoffm. – 17, 18 – 82–154 m – Open mesic cliff crevice in large riverside N-facing cliffs surrounded by scattered Betula lanata. With Mannia cf. sibirica. Kh-48-1-19, Kh-49-13-19, Kh-50-3-19. Kh-51-3-19.

Riccia sorocarpa Bisch. – 17 – 82 m – Open moist humus filling cliff crevice in large riverside S-facing cliffs surrounded by scattered Betula lanata. With Cephaloziella divaricata and Mannia sibirica. Kh-49-3-19.

Sauteria alpina (Nees) Nees – 18 – 129–154 m – Open moist cliff crevices also those filled with humus in large N-facing conglomerate riverside cliffs surrounded by scattered Betula lanata. In pure mats and with Eremonotus myriocarpus and Solenostoma obscurum. Kh-50-12-19, Kh-56-9-19, Kh-56-10-19, Kh-56-11-19, Kh-56-12a-19.

Scapania crassiretis Bryhn – 7, 9, 18, 22 – 119–1484 m – Open to partly shaded moist to wet cliffs and their crevices, rarely moist humus on slope, only along watercourses (although sometimes at a distance from the running water); in alpine belt with scattered vegetation, rarely in open places on riverside rocky outcrops in scattered forest. In pure mats or with Diplophyllum taxifolium, Frullania subarctica, Gymnomitrion corallioides, Herbertus aff. buchii, Plagiochila arctica, Pseudolophozia sudetica, Ptilidium ciliare and Trilophozia quinquedentata. Kh-39-1-19, Kh-39-7-19, Kh-39-13-19, Kh-41-7-19, Kh-50-1-19, Kh-50-45-19, Kh-50-54-19, Kh-54-3-19.

Scapania cuspiduligera (Nees) Müll. Frib. – 25 – 22 m – Partly shaded moist humus along stream, with many limestone boulders in the stream bed in open Larix forest. In pure mats. Kh-58-6-19.

Scapania gymnostomophila Kaal. – 18, 24 – 34–154 m – Humus covering rocks and cliff crevices, only those in limestone and basic conglomerates; at low elevation, surrounded by tundra-like community developed due to severe wind conditions near seacoast or by scattered Betula lanata over large riverside N-facing cliffs. With Blepharostoma sp., Eocalypogeia schusteriana, Jungermannia afoninae, Lophozia lantratoviae, Mannia pilosa, Mesoptychia badensis, Preissia quadrata and Trilophozia quinquedentata. Kh-50-1-19, Kh-50-51-19, Kh-56-15-19, Kh-56-22-19, Kh-57-7-19, Kh-57-10-19, Kh-57-18-19, Kh-57-22-19.

Scapania hyperborea Jørg. – 6 – 904 m – Open wet cliff on N-facing slope to stream in subalpine belt amongst mosaic of Duschekia and Pinus pumila clumps and mountain tundra vegetation. In pure mats. Kh-38-10a-19.

Scapania irrigua (Nees) Nees – 13, 14, 15, 21 – 54–1139 m – Open to partly shaded stones and humus covering rocks along streams and in waterfall canyons; from low elevations with Picea ajanensis dominating forests (also those with admixture of Betula lanata) to moist mountain moss-dwarf shrub tundra. In pure mats or with Cephalozia bicuspidata, Jungermannia pumila and Nardia cf. geoscyphus. Kh-45-1-19, Kh-46-2-19, Kh-47-11-19, Kh-53-8-19.

Scapania microdonta (Mitt.) Müll.Frib – 5, 8, 19 – 418–1328 m – Open to partly shaded mesic crevices in cliffs and between boulders in gravelly barrens in alpine and subalpine belts. In pure mats or with Barbilophozia barbata, Sphenolobus minutus, Sphenolobus saxicola and Tetralophozia setiformis. Kh-37-3-19, Kh-40-8-19, Kh-51-1-19.

Scapania mucronata H. Buch – 1, 3, 4, 17, 18 – 11–377 m – Open moist cliffs and boulders covered with thin layer of humificated soil, rarely humus on trail sides; in low elevations collected in scattered Betula lanata forest surrounding riverside cliffs and Larix cajanderi forest in narrow valley; in subalpine belt collected in scattered Duschekia and Pinus pumila clumps on steep slope. With Blepharostoma sp., Diplophyllum sibiricum, Diplophyllum taxifolium, Marsupella emarginata, Schistochilopsis sp., Solenostoma obscurum and Tritomaria exsecta. Kh-33-4-19, Kh-35-6-19, Kh-36-6-19, Kh-49-19-19, Kh-56-6-19.

Scapania paludicola Loeske & Müll. Frib. – 6 – 904 m – Humus on the bank of sluggishly-flowing stream in moist moss-dwarf shrub tundra. In pure mats. Kh-45-1a-19.

Scapania parvifolia Warnst. – 1, 9, 11, 12 – 11–1484 m – Open (or, rarely, partly shaded) moist sandy, clayish and humificated soil on steep slopes (also those going to streams); mostly in alpine belt in scattered dwarf shrub-moss tundras, also those developed in percolating waters, once in subalpine belt amongst Duschekia and Pinus pumila clumps on the slope ca. 30° steepness. With Calypogeia integristipula, Calypogeia muelleriana, Cephalozia bicuspidata, Lophozia sp., Pleurocladula albescens, Pseudotritomaria heterophylla, Sphenolobus minutus and Trilophozia quinquedentata. Kh-33-9-19, Kh-41-2-19, Kh-43-5-19, Kh-44-7-19.

Scapania rufidula Warnst. – 3, 18, 20 – 129–294 m – Open wet boulders near streams, rarely sandy stream banks; in floodplain (dominating by Populus suavealons and Salix udensis), low elevation Picea ajanensis and Betula lanata and their combinations dominating forests. In pure mats or with Blepharostoma sp. and Lophozia lantratoviae. Kh-35-4-19, Kh-35-13-19, Kh-50-11-19, Kh-52-1-19, Kh-56-7-19, Kh-56-8-19.

Scapania sphaerifera H. Buch & Tuom. – 19 – 780 m – Open mesic cliff crevice at the mountain ridge just above crooked forest line. With Barbilophozia hatcheri, Sphenolobus saxicola and Tetralophozia setiformis. Kh-51-9-19.

Schistochilopsis incisa (Schrad.) Konstant. s.l. – 1, 4, 6, 7, 14, 15, 17, 18, 23 – 11–1261 m – Party shaded moist decaying wood and humus covering cliffs in Picea ajanensis with various proportions of admixture of Betula lanata forests, as well as scattered Betula lanata stands surrounding large riverside cliffs; moist to wet cliffs and their crevices and moist boulders near streams in subalpine (with mosaic of Duschekia and Pinus pumila clumps and mountain tundra vegetation on steep N-facing slope) and alpine (scattered tundra vegetation amongst gravelly barrens) belts, once found in floodplain forest dominating by Populus suavealons and Salix udensis. With Blepharostoma sp., Calypogeia integristipula, Cephalozia bicuspidata, Diplophyllum taxifolium, Douinia plicata, Fuscocephaloziopsis lunulifolia, Lepidozia reptans, Marsupella boeckii, Marsupella emarginata, Mylia verrucosa, Pseudolophozia sudetica, Solenostoma obscurum, Sphenolobus minutus, Trilophozia quinquedentata and Tritomaria exsecta. Kh-38-13-19, Kh-39-8-19, Kh-46-13-19, Kh-47-2-19, Kh-47-3-19, Kh-49-15-19, Kh-55-1-19, Kh-56-3-19.

Schljakovia kunzeana (Huebener) Konstant. & Vilnet – 12 – 1109 m – Wet mossy bank of the stream in moist mossy tundra. With Gymnocolea inflata. Kh-44-12-19.

Solenostoma cf. confertissimum (Nees) Schljakov. – 15 – 143 m – Partly shaded moist boulder on slopes in mostly Picea ajanensis forest in narrow valley. With Mesoptychia aff. heterocolpos. Kh-47-10-19.

Solenostoma obscurum (A. Evans) R.M. Schust. – 4, 15, 18, 20, 21 – 129–377 m – Open to partly shaded moist to wet boulders and cliffs along streams and river, also waterfall canyons in Populus suaveolens and Salix udensis floodplain forests and Picea ajanensis dominating forests on slopes. In pure mats and with Anthelia juratzkana, Cephalozia bicuspidata, Diplophyllum taxifolium, Eremonotus myriocarpus, Sauteria alpina, Scapania mucronata, Scapania sp., Schistochilopsis incisa, Schistochilopsis incisa and Trilophozia quinquedentata. Kh-36-5-19, Kh-47-22-19, Kh-47-27-19, Kh-50-53-19, Kh-52-2a-19, Kh-53-5-19, Kh-56-6-19.

Solenostoma rossicum Bakalin & Vilnet – 18 – 129–154 m – Open moist cliffs and their crevices partly filled with humus in large N-facing riverside conglomerate cliffs with scattered Betula lanata. With Bazzania tricrenata, Cephaloziella sp., Herbertus aff. buchii, Metacalypogeia cordifolia, Plagiochila porelloides, Sphenolobus minutus and Tritomaria exsecta. Kh-50-20-19, Kh-56-20-19.

Sphenolobus minutus (Schreb.) Berggr. – 1, 3, 5, 6, 8, 9, 11, 17, 18 – 11–1484 m – Partly shaded mesic boulders, open moist cliffs, dense Sphagnum cushions, rarely partly shaded moist clayish soil on steep slopes; from low elevation floodplain and Picea ajanensis forests via krumholtz to alpine belt with scattered vegetation represented by dwarf shrub-lichen tundra and Sphagnum lenense mats on percolate water openings, surrounded by gravelly barrens. In pure mats or with Anthelia juratzkana, Bazzania tricrenata, Blepharostoma sp., Calycularia laxa, Calypogeia integristipula, Calypogeia muelleriana, Calypogeia sp., Cephalozia bicuspidata, Cephaloziella sp., Diplophyllum taxifolium, Douinia plicata, Gymnomitrion corallioides, Herbertus aff. buchii, Lepidozia reptans, Lophozia silvicoloides, Lophozia sp., Marsupella emarginata, Metacalypogeia cordifolia, Neoorthocaulis binsteadii, Scapania microdonta, Scapania parvifolia, Schistochilopsis incisa, Solenostoma rossicum and Tetralophozia setiformis. Kh-33-6-19, Kh-35-12-19, Kh-35-15-19, Kh-37-3-19, Kh-38-6-19, Kh-39-12-19, Kh-40-6-19, Kh-41-2-19, Kh-43-3-19, Kh-43-7-19, Kh-49-4-19, Kh-50-37-19, Kh-56-21-19.

Sphenolobus saxicola (Schrad.) Steph. – 5, 7, 8, 11, 19 – 418–1328 m – Open mesic cliff crevices, also those filled with soil, rarely dense Sphagnum cushions; in alpine belt with scattered vegetation amongst gravelly barrens or ridgeline cliffs. In pure mats or with Barbilophozia hatcheri, Calycularia laxa, Lophozia sp., Scapania microdonta, Scapania sphaerifera and Tetralophozia setiformis. Kh-37-2-19, Kh-39-4-19, Kh-40-8-19, Kh-43-12-19, Kh-51-5-19.

Tetralophozia setiformis (Ehrh.) Schljakov – 5, 6, 8, 11, 19 – 418–1328 m – Mesic cliffs on ridgeline, crevices between boulders in gravelly barrens, rarely moist dense Sphagnum lenense cushions; only in alpine belt. In pure mats or with Anthelia juratzkana, Barbilophozia hatcheri, Gymnocolea inflata, Scapania microdonta, Scapania sphaerifera, Sphenolobus minutus and Sphenolobus saxicola. Kh-37-1-19, Kh-38-10-19, Kh-40-6-19, Kh-43-10-19, Kh-51-6-19.

Trilophozia quinquedentata (Huds.) Bakalin – 2, 4, 12, 15, 18, 19, 22 – 119–1109 m – Open to partly shaded moist to wet cliffs and their crevices, boulders, also those near streams, open moist humus on stream banks; from low elevation in various forests, through subalpine belt in scattered shrubby clumps to alpine belt in scattered vegetation surrounded by gravelly barrens and ridgeline cliffy massifs. In pure mats or with Bazzania tricrenata, Blepharostoma sp., Calycularia laxa, Cephalozia bicuspidata, Diplophyllum taxifolium, Frullania davurica, Lophozia lantratoviae, Marsupella emarginata, Mesoptychia heterocolpos, Pleurocladula albescens, Preissia quadrata, Pseudolophozia sudetica, Scapania crassiretis, Scapania gymnostomophila, Scapania parvifolia, Schistochilopsis incisa, Solenostoma obscurum and Tritomaria scitula. Kh-34-4-19, Kh-36-1-19, Kh-44-6-19, Kh-47-22-19, Kh-46-11-19, Kh-50-22-19, Kh-51-8-19, Kh-54-3-19, Kh-56-14-19.

Tritomaria exsecta (Schmidel ex Schrad.) Schiffn. ex Loeske – 4, 18, 23 – 118–377 m – Open moist cliff crevices partly filled with humus, partly shaded humus covered boulders near streams; low elevation riverside cliff-like massifs with scattered Betula lanata and floodplain forests dominated by Populus suavealons and Salix udensis. With Bazzania tricrenata, Blepharostoma sp., Lepidozia reptans, Lophozia sp., Metacalypogeia cordifolia, Plagiochila porelloides, Scapania mucronata, Schistochilopsis incisa and Solenostoma rossicum. Kh-36-6-19, Kh-50-21-19, Kh-55-1-19.

Tritomaria scitula (Taylor) Jørg. – 18 – 129–154 m – Open moist cliff crevice in large riverside N-facing cliffs with scattered Betula lanata. With Blepharostoma sp., Lophozia lantratoviae, Mesoptychia heterocolpos and Trilophozia quinquedentata. Kh-50-32-19.

The total number of revealed taxa (118 species, including one criptic taxon and 1 subspecies) is quite high for relatively brief studies of the local hemiarctic flora. This is likely a consequence of co-action of habitat diversity (of geological, orographic and climatic origin) and historical reasons (the position of explored area at the migration route between Northeast Asia and East Asia). Meanwhile, not all revealed taxa are listed in the checklist. There are several specimens which were not identified convincingly. These doubtfully identified specimens require a molecular-genetic study to find the name (some of them may belong to undescribed taxa). These unlisted taxa may potentially provide certain additional peculiarities of the studied flora.

Relatively few in number are ‘forest’ taxa, represented here by boreal and hemiboreal species (distributed mostly in corresponding zones of the Northern Hemisphere). Several of them were found on decaying wood in Picea ajanensis forests (less in number are epixylous taxa in Larix cajanderi forests): Fuscocephaloziopsis leucantha and Mylia verrucosa are locally abundant, Crossocalyx hellerianus is rare, Anastrophyllum michauxii, Calypogeia suecica and Radula complanata (also recorded from the cliff) were found only once. Bazzania denudata is rare and found on rocky substrates, only in the localities near the seacoast. Frullania bolanderi, apparently, is quite frequent in floodplain communities, on the trunks of Salix udensis and Betula lanata. Rarely observed are Lophocolea heterophylla (floodplain forests only) and Lophozia ventricosa (also found in Picea–Betula forest).

Two taxa complete the epiphytes in the area: Frullania bolanderi and Ptilidium pulcherrimum. The latter is widespread on tree trunks and thick branches in tall and crooked forest communities. Some taxa, commonly not limited to the forest communities in other hemiarctic floras, are exclusively forest taxa in the explored area: Fuscocephaloziopsis lunulifolia, Lepidozia reptans, Lophocolea minor, Lophozia lantratoviae, L. silvicola, Scapania irrigua, S. mucronata, S. rufidula and Solenostoma obscurum. Douinia plicata is found in all belts and is abundant in true forests and krummholtz. Larix cajanderi forests are poor in taxa (excluding liverwort flora of watercourses and other habitats only slightly related to the larch forest itself). Their dryness predict occurrence of meso-xerophytes, like Barbilophozia barbata. The species previously identified as Blepharostoma brevirete (Bryhn & Kaal.) Vilnet & Bakalin (Blepharostoma sp. (Kh-58-4-19) in the annotated checklist) was found in open Larix forest and was re-identified by genetic methods as a different, not yet described (tentatively cryptic) hybrid of B. trichophyllum and an unknown taxon (Bakalin et al. 2020a). It is morphologically similar to B. brevirete.

The krummholtz (Pinus pumila and Duschekia fruticosa thickets) houses a few liverwort taxa and have no specific flora. Besides Ptilidium pulcherrimum that is the commonest species in these communities, a whole series of species are found here, descending into crooked forests from the alpine belt along watercourses, i.e. by intrazonal habitats. On the contrary, examples of taxa that would join forests and krumholtz, but would be absent in alpine belt are few: Lophozia silvicoloides, Ptilidium ciliare and Scapania mucronata – their absence from the alpine belt may be the simple result of undercollecting, since all those listed are common inhabitants of alpine belts in other parts of the eastern Paleoarctic.

The arctic-montane acidophilous (or neutrotolerant) species were quite numerous. Widely distributed, though not confined to, but more frequent in the alpine belt, were Anthelia juratzkana, Gymnomitrion corallioides, Pleurocladula albescens, Pseudolophozia sudetica, Scapania microdonta, Sphenolobus saxicola and Tetralophozia setiformis. Other taxa were sparse and occurred locally in upper elevations: Cephaloziella varians and Gymnomitrion concinnatum. Several species were restricted to the high altitudes in the upper reaches of the axial part of Dzhugdzhur Range: Gymnomitrion commutatum, Prasanthus suecicus and Protochilopsis grandiretis were all very rare in the explored area. Isopaches bicrenatus (that is not, strictly speaking, purely arctic-montane species) was found only on solifluction spots in the axial part of Dzhugdzhur Range. Neoorthocaulis binsteadii was very common on Sphagnum cushions in the axial part. Riccardia palmata that was rather expected to be found on decaying wood in lower altitudes, was found only in the alpine belt in tundra environments. Similarly, mainly swampy Scapania paludicola and Schljakovia kunzeana were found in moist moss-dwarf shrub tundra near streams. Rare were Diplophyllum sibiricum, Jungermannia afoninae, Marsupella boeckii and M. emarginata. Scapania sphaerifera, expected in the axial part, was found at the highest elevations in Pribrezhny Range in the coastal part of the area only.

A limited number of species were common in all altitudinal belts: Calypogeia integristipula, Lophozia guttulata (the specimens referred to this species were gathered in mountain tundra and may represent another taxon not yet described), L. lantratoviae, Scapania crassiretis and Sphenolobus minutus. Sparsely, although occurring across all belts, were Metzgeria pubescens, Plagiochila porelloides, Preissia quadrata, Scapania parvifolia, S. rufidula (restricted to the axial part of Dzhugdzhur Range), Schistochilopsis incisa, Sphenolobus minutus, Trilophozia quinquedentata and Tritomaria exsectiformis.

The abundance of Cretaceous sediments of basic reactions (limestone and its derivates) has determined the wide distribution of basiphilous taxa accounting for about 10% of the liverwort flora. The presence of basiphilous taxa is a peculiar feature of studied flora in comparison with the vast majority of other local floras in Hemiarctic Pacific Asia. Striking examples of basiphilous taxa include Eocalypogeia schusteriana, four species of Mannia, three species of Mesoptychia (M. badensis, M. gillmanii, M. rutheana), Peltolepis quadrata, Pseudotritomaria heterophylla, Sauteria alpina, Scapania cuspiduligera and S. gymnostomophila. Conocephalum salebrosum should be conditionally referred to the group of basiphilous taxa in the investigated area since it was found only in areas of distribution of limestone and neutral metamorphic rocks. Mesoptychia heterocolpos is also not the obligate basiphilous taxon; however, it was found only in the area where basic rocks are distributed. Three species, Cryptocolea imbricata, Plagiochila arctica and Radula prolifera although, were found in the axial part of Dzhugdzhur Range that is predominantly acidic, but restricted there to the places with a pronounced neutrophilic flora (including from vascular plants, for example, Salix berberifolia Pall.) and developed near basic reaction percolating water openings.

The rocky outcrop liverwort flora in lower altitudes usually is not liverwort-rich, with one striking exception. In the course of our works, we found a large riverside cliff-like massif on the right bank of the Unych’ya River in its middle course (56°25'07.3"N 137°56'54.7"E) that is very peculiar in its geological and ecological respect (Fig. 8a). The cliff area has a length of about 100 m along the riverbed and has a height of up to 50 m from the riverbed to the top. These are conglomerate rocks that unite both basic and acidic metamorphic 'pebbles' (expected only due to the bryophyte inhabitants of the rocky particles as no special chemical analyses were conducted there) (Fig. 8b). Ecologically, these cliff walls also provide a variety of moisture conditions (from very wet to very dry) combined with variations in illumination and various niches and caves. Besides, these cliffs are covered by scattered Betula lanata trees – in this case, by enriching potential habitat diversity by shading as well. The liverwort diversity occurred there covers about 40% of the entire explored flora, although with the vast majority of taxa found also in other complexes. Bazzania tricrenata, Frullania davurica and Herbertus dicranus were very common there, while Jungermannia afoninae and Metacalypogeia cordifolia were sparse. Several taxa, including Erimonotus myriocarpus, Frullania ignatovii, F. subarctica, Lejeunea alaskana, Peltolepis quadrata, Porella vernicosa, Reboulia hemisphaerica, Sauteria alpina, Solenostoma rossicum and Tritomaria scitula were found only in the mentioned cliff-like massif. Moreover, for some of the listed species (Frullania ignatovii, F. subarctica and Lejeunea alaskana), this location is very unusual, taking into account the low elevation that formally belongs to the forest belt. The striking trait of the liverwort complex in the described massif is the occurrence within the same locality of the species belonging to different flora elements: it is especially pronounced in the ‘pair’ Metacalypogeia cordifolia and Eocalypogeia schusteriana occurring in adjacent patches of the same cliff. The chemical composition diversity results in an almost artificial mixture of joint occurrence of acidophilous and basiphilous taxa, like Bazzania denudata growing together with Tritomaria scitula. Taking into account the total diversity and peculiarity of taxonomic composition, this cliff riverside complex deserves protection as a natural monument of regional significance.

The formerly (and on-going) migration of liverworts by the mountains along the western coast of the Sea of Okhotsk in view of possible connections between East Asian and North-East Asian floras may be well illustrated by the occurrence of mainly Beringian Cryptocolea imbricata, Eocalypogeia schusteriana, Frullania ignatovii, Frullania subarctica and Fuscocephaloziopsis pachycaulis found in the area. All of them were recorded also south of the explored area. 'Southern', mainly temperate East Asian elements were represented by a lesser number of taxa, including Metacalypogeia cordifolia, Porella vernicosa and Mylia verrucosa. For the first two taxa, the studied locality is the northernmost outpost of worldwide distribution. Calypogia neogaea – mainly East Asian–North American taxon, occurring in the areas adjacent to the oceanic coast – had in Ayan surroundings the most ‘inland’ and the most northern occurrence in the Asian mainland.

Describing characteristic traits of the liverwort flora in the area treated, the absence of several taxa, forming ‘negative’ peculiarity, should be also taken into account. A large number of boreal ‘forest’ taxa were not found in the area: Bazzania trilobata, Nowellia curvifolia, Neoorthocaulis attenuatus and Scapania apiculata. For all listed, it was quite unexpected, because they are known not only southwards, but also north of Ayan surroundings. The same should be noted on the taxa commonly not limited by forest communities and absent from the explored area: Chyloscyphus polyanthos, Geocalyx graveolens and Harpanthus flotovianus. Aneura pinguis occurs very locally. Calypogeia muelleriana is very rare. Even so widespread in Holarctic, Cephalozia bicuspidata is quite rare. Very infrequent were Diplophyllum taxifolium, Gymnocolea inflata and Mylia anomala. Once found were Marchantia polymorpha and Pellia neesiana. Extremely rare (and observed in the axial part of the Dzhhugdzhur Range only) was Nardia geoscyphus. Certainly, the ‘absence’ of some taxa may be caused by the imperfections of the study, but for some taxa, another explanation may be necessary. It is difficult to expect that we have overlooked large-sized plants such as Chiloscyphus or so widespread in Northeast Asia, Harpanthus flotovianus. The rarity of Cephalozia bicuspidata and Diplophyllum taxifolium, as well as several other taxa is also surprising. The possible explanations may be in the wide distribution of basic and neutral rocks (blocking wide distribution of acidophilous taxa) and the wide distribution of neutrophilous and neutrotolerant taxa, with the latter also able to occupy the habitats potentially suitable for acidophilous taxa. A similar phenomenon was observed in the boreal zone in Sakhalin Island in the area with the evident dominance of limestone outcrops and neutral rocks (Bakalin et al. 2019).

The vast majority of taxa belong to the arctic-montane flora elements, although boreal taxa are also quite common in the flora. Therefore, the liverwort flora, in general, possesses a subarctic character (thus being the same as the vegetation). Using Whittaker (1960) terminology, the relatively high gamma diversity of the explored area is associated with low level of alpha diversity: each small site by itself possesses a few species, but the difference in the inhabitants’ composition of different sites (e.g. basic and acidic rocks) is quite strong. The combination of various flora elements and taxa of different ‘acidophilia’ results in taxonomically quite rich liverwort flora. Nevertheless, although our assumption on the taxonomic richness of the liverwort flora in the studied area was confirmed, the revealed diversity cannot be regarded as the final calculation. Moreover, taking into account the short duration of the studies, the data obtained by us should be considered as preliminary only and may be supplemented with many new findings in the further studies.