LOCAL FLORA OF NELKAN PASS (TAS-KYSTABYT RANGE, NORTHEASTERN YAKUTIA)
Tas-Kystabyt Range is one of the largest mountain systems in the Northeastern Asia, separating the Oymyakon Plateau and Chersky Range. The maximum height of mountains in the system is 2353 m. Nelkan Pass is a mountain saddle in the northwestern part of the range, located at ~1400 m above sea level, and the adjacent peaks reach 1700–1800 (2000) m. The pass is a natural watershed of a left tributary of the Nera River (Artyk-Yuryue stream) and the basin of the Nelkan River (tributary of the Indigirka River), and is used as a road to mountain mines. The study area is located in the area of extremely cold climate with winter air temperatures approaching –65…–70°С, and the solid thickness of permafrost reaching 400–700 m. An average annual temperature in the town Ust-Nera located not far from the pass is –15.4°С. The severe climate and soil conditions have contributed to a very restricted flora and vegetation diversity of the area. The vegetation of the studied part of Tas-Kystabyt Range forms the altitudinal belts (zones): forest, sub-goltsy shrubs, tundra, epilithic-lichen communities, and the complex of valley vegetation. Such species as Larix dahurica subsp. cajanderi, Pinuspumila, Carexbigelowii, C. soczaveana, Eriophorumvaginatum, Salixalaxensis, S. berberifolia subsp. fimbriata, S. polaris, S. pulchra, S. tschuktschorum, Betuladivaricata, B. nana subsp. exilis, Duschekiafruticosa, Saxifraganelsoniana, S. punctata, S. spinulosa, Dryaspunctata, Empetrumnigrum, Chamerionlatifolium, Cassiopeericoides, C. tetragona, Ledumpalustre subsp. decumbens and L. palustre var. angustum, Rhododendronaureum, Vacciniumuliginosum subsp. microphyllum, V. vitis-idaea var. minus, Pedicularisalopecuroides, Valerianacapitata, Crepisnana, Petasitesglacialis, Saussureatilesii have an important phytocoenotic value and in different combinations form the structure of the altitudinal belts. Ample space on the sides of the Artyk-Yuryue stream valley is occupied by rock outcrops – rocks and screes, covered with epilithic lichens. Until recently, the structure of the flora of this area remained unknown. The aim of the research is to accumulate an analytical database on the distribution of vascular plant species in the Northeastern Yakutia. The accounting of vascular plant species distribution was conducted in the period 17–28.06.2014 and 26–28.06.2015, using the method of concrete floras developed by A.I. Tolmachev. For quantitative evaluation of biological diversity, a sample site (1 sq. km) was laid in the Artyk-Yuryue stream valley for the study of the standard flora according to the original methodology of the author. The low-temperature regime of the studied area and the predominance of stony sites with poorly developed soil cover created a prerequisite for the selection of the most cold-resistant petrophytes from a limited number of species growing in the Northeastern Yakutia. The flora comprises a total of 121 species, including 1 nothospecies, 3 subspecies and 4 varieties included in 31 families and 71 genera. A significant share is a group of adventive and presumably adventive species – 17 taxa: Agrostisanadyrensis, Festucabrachyphylla, Poaglauca, P. ochotensis, Eriophorumcallitrix, Choseniaarbutifolia, Salixbebbiana, Betulapendula, Silenestenophylla, Drabalactea, Rorippabarbareifolia, Ribesfragrans, Rubussachalinensis, Artemisiaborealis, A. leucophylla, Erigeronacris, Taraxacum sp. Some primarily petrophyte species of a native fraction (Pinuspumila, Salixkhokhrjakovii, S. tschuktschorum, Saxifragapunctata, Potentillaelegans, P. inquinans, Chamerionangustifolium, C. latifolium, Cassiopeericoides, Ledumpalustre subsp. decumbens, Artemisiafurcata, A. kruhsiana and Crepis nana) show a clear positive response to the development of roadside dumps, mounds, hollows, increasing their number and frequency of occurrence in such habitats. The most diverse are the following genera: Salix – 16 species, Saxifraga – 7 species (including one hybrid) and 1 variety, Carex – 6 species and 2 subspecies, Artemisia – 4 species (2 of them are probably adventive). The remaining genera include 3 species or less. This composition shows that the flora its young, weakly isolated, consisting chefly of cryopetrophytic elements, largely represented by the pioneers of mountain spaces. The analyzed flora has a high similarity with the flora of the Suntar-Hayata Range, similar by the severity of climatic conditions, and with the flora of Darpir Lake located in the mountains on the border of Yakutia and the Magadan Region. The standard flora of the area numbers 87 species, 3 subspecies and 2 varieties (92 taxa/sq. km). This is a very low index of diversity of the territory. To compare, there are data for the valley of the Lena River: in its middle reaches (61°04–05'' N, 126°20–28'' E) there are 228 species/sq. km, and in its lower reaches (72°11'' N, 128°01–03'' E) 170 taxa/sq. km (161 species, 1 nothospecies and 8 subspecies). There growing on a very small space of the studied area are rare and protected species: Hyalopoalanatiflora subsp. momica, Rhododendronaureum, Carexsoczaveana, Salixkhokhrjakovii, Claytoniasoczaviana.