The basis for the existence of Arctic plant and animal species is the presence of suitable habitats (biotopes) – fragments of the earth's surface that are vital for a biological species or communities at a certain period of time. Considering the diversity of habitat types in the Russian Arctic, their inventory, preceded by classification, is firstly necessary. In 2019, with the support of a grant from the Russian Science Foundation (RSF), work began on creating a catalog of Arctic habitats using the East European tundra as the case study. The experience of European countries, which have been implementing a number of national and common European programs for the protection of habitats for decades, was taken into account [Lavrinenko, 2020].

A multi-level classification of habitats is demonstrated using the case of the mires of the East European tundra. The classification of habitats is based on their location on the geomorphological profile and environmental features, which are identified by the syntaxonomic composition of vegetation. Since the tundra zone is characterized by small-contour and mosaic landscapes, combinations of phytocenoses – territorial units of vegetation (TUV) have to be highlighted even on large-scale maps.

To define habitats based on their syntaxonomic composition, a typological scheme that allows identifying TUVs of varying complexity and rank (from type to class and division) on the map while preserving information on the composition of syntaxa and the spatial structure of the contours has been developed [Lavrinenko, 2020, 2021; Lavrinenko, Lavrinenko, 2020]. The typological scheme and TUV nomenclature are based on the Braun-Blanquet classification. The background vegetation of the Oxycocco-Sphagnetea and Scheuchzerio–Caricetea nigrae bogs and fens in the East European tundra has been studied to the level of associations and subassociations [Lavrinenko et al., 2016, 2022; Lavrinenko, Lavrinenko, 2015, 2021].

The highest unit of the typological scheme is the division, which combines the TUV of the largest landscape elements (watersheds, river valleys with a floodplain regime and low marine terraces). Divisions include classes – topographically expressed TUV, which reflect the ecological uniqueness of genetically homogeneous simple relief forms by the composition of syntaxa and their combinations. Types are the main elementary units of the typological scheme. Their determination is based on two main criteria: the syntaxonomic composition of TUV elements and the type of spatial structure (phytocenoses, ecological-genetic series, ecological series, complexes, complex combinations). It is proposed to use subclasses and groups as secondary units. A scheme for the step-by-step unification of TUV categories from phytocenosis to geobotanical region during map generalization as the scale decreases was developed using coastal marshes as the case study [Lavrinenko, 2020].

According to the habitat classification at the highest level, 4 groups of biotopes were identified: A – watershed habitats, B – habitats of river valleys with a floodplain regime, C – coastal habitats, D – marine habitats, including estuaries. To reflect the zonal position of biotopes, a letter was added to the highest-level index: a – polar deserts, b – tundra, c – forest-tundra belt, d – taiga, etc. Biotopes of the second-level categories (Ab1, …, Cb3) differ in their position on the generalized geomorphological profile – from the highest to the lowest positions. When identifying the third-level categories, along with the position on the profile, the features of substrate, and the fourth and lower levels – physiognomic (color, texture) and spectral (indices, signatures) characteristics are taken into account. Each category of biotopes below the second level is diagnosed by TUV of the corresponding rank and syntaxonomic composition – from class to type, which reflects its complexity and spatial structure well. The classification of habitats of different levels allows using all TUV ranks for naming – from type to class, depending on the scale and degree of vegetation study.

Mire biotopes belong to the Ab3 category – habitats of drainless or semi-drainage accumulative-eluvial landscapes, which in turn is subdivided into 5 categories of the third level: Ab3.1 – marshy marine terraces with grass (sedge and cotton grass) and dwarf shrub-moss (sphagnum and brown and green mosses) communities on acidic peat and peaty waterlogged soils; Ab3.2 – willow (Salix myrsinites)-moss boggy communities with a high proportion of hemicalciphyte species on base-rich substrates; Ab3.3 – peatlands (bogs) in relief depressions, where active peat accumulation occurred in the Holocene; Ab3.4 – arctic mineral mires; Ab3.5 – lowland sedge-brown-moss and sedge-cotton grass-brown-moss fens. Within the categories of the third level, 10 categories of the fourth level are identified and characterized. Each category passport contains: habitat name, compliance with the EUNIS category, TUV name, syntaxonomic composition of vegetation (alliances, associations and subassociations), vegetation definition, diagnostic species (characters, dominants and constants), ecological conditions (location on the geomorphological profile, soil moisture and type, permafrost, etc.), distribution in the Nenets Autonomous Okrug, species in the Red Data Book of the Nenets Autonomous Okrug (2020), threats and limiting factors, photographs.

The proposed habitat monitoring system does not replace, but complements the established and existing system of nature conservation in Russia through the creation and operation of Special Protected Natural Areas. The prepared catalogue of habitats can serve as a basis for studying their dynamics under anthropogenic impacts and climatic change, and for organizing field and remote monitoring.