Pteridophyte distribution of the Urals and adjacent areas: a dataset

Abstract Background Data on the species diversity and distribution of pteridophytes (lycophytes and ferns) in the Urals and adjacent areas are presented. The dataset includes 13,742 observations of two classes Lycopodiopsida and Polypodiopsida. In total, the dataset contains information on 16 families, 28 generas, 65 species, four subspecies and nine interspecies hybrids. All records are for lycophytes and ferns collected over 170 years between 1853 and 2021. The dataset presented is based on herbarium specimens, published data and field research conducted by the authors. This dataset is the first and important step towards generalising information on the current diversity and geographical distribution of pteridophytes in the Urals and adjacent areas. New information The dataset contains 13,742 records of 65 species of pteridophytes occurrences in the Urals and adjacent territories: Udmurt Republic (42,100 km2); Perm Krai (160,600 km2); Sverdlovsk Oblast (194,800 km2); Chelyabinsk Oblast (87,900 km2); Republic of Bashkortostan (143,600 km2); Tyumen Oblast (160,100 km2); Yamalo-Nenets Autonomous Okrug (769,300 km2); Khanty-Mansi Autonomous Okrug (534,800km2) and Kurgan Oblast (71,500 km2). Each record includes a geographical description of the place of discovery and habitat, year of discovery, author of the finding and determination, as well as a link to a literary source (if the data were published) or the place of storage of the herbarium specimen. The presented dataset supplements the information on the occurrence of pteridophytes in the Russian Federation as a whole and clarifies their distribution in the Urals.


Introduction
The study of the floristic diversity of territories is the basis for solving the problems of plant taxonomy, phytogeography, botanical resource science, protection of rare and endangered plant species etc. The vegetation cover is constantly changing and its study remains an important scientific direction.
The flora of the Urals and adjacent territories has been studied for a long time. Some of the first researchers of the Ural flora were J.G. Gmelin, P.S. Pallas, I.I. Lepyokhin, J.P. Falck and J.G. Georgi. The first large floristic summaries of the vegetation cover of the Urals were published in the late 19 -early 20 century were the works of P.N. Krylov (Krylov 1927), S.I. Korzhinsky (Korshinsky 1898), P.V. Syuzev (Syuzev 1912) and V.S. Govorukhin (Govorukhin 1937).
Currently, a huge amount of data has been accumulated on the biological diversity of the flora of the Urals. The results are summarised in the form of regional floristic summaries, such as checklists and flora keys. At the same time, the collected information is inaccessible to the majority of Russian colleagues and the international scientific 2 2 2 2 2 2 2 2 2 th th community. The current global trend in biodiversity research is the use of the information technology and the principles of open science. Uploading the biodiversity data into the open international repositories would make them accessible to a wide range of specialists and help to find solutions to a wide range of problems at the regional and global level.
Our group of authors compiled a dataset on the diversity and distribution of Lycopodiophyta and Polypodiophyta of the Urals and adjacent areas and published it in the Global Biodiversity Information Facility (GBIF) as a Darwin Core Archive (Melnikov et al. 2021). The dataset was prepared in accordance with the concept of "data paper" (Penev et al. 2017) and contains information on the species composition, distribution and diversity of fern habitats in the Urals and adjacent areas. This is the first step towards the "Flora of the Urals and adjacent areas", which will summarise all available information on the distribution of vascular plants in the study area and reflect modern views of taxonomists. These data were supplemented by published materials (Kler 1914, Krylov 1927, Gorchakovsky 1950, Krasovsky and Skvortsov 1959, Igoshina 1966, Gorchakovsky 1975, Naumenko 1994, Radchenko and Fedorov 1997, Naumenko and Ivanenko 1999, Mukhin et al. 2003a, Mukhin et al. 2003b, Yudin et al. 2005, Kulikov and Kirsanova 2012.
Third data source about occurrences of lycophytes and ferns in the Urals and adjacent areas is based on field surveys performed by the authors. Every type of habitat, including natural, semi-natural and human-made in each region, was surveyed for the presence of species of pteridophytes. Step description: The dataset preparation process included the following steps.

Geographic coverage
Description: The dataset contains information on the distribution of Lycopodiophyta and Polypodiophyta in nine administrative regions of the Russian Federation including Regions of Cis-Urals (Perm Krai, the Udmurt Republic), Urals (Republic of Bashkortostan, Chelyabinsk Oblast and Sverdlovsk Oblast), and Trans-Urals and Western Siberia (Kurgan Oblast and Tyumen Oblast, Khanty-Mansi Autonomous Okrug -Yugra, Yamal-Nenets Autonomous Okrug). The largest number of occurrences (6776 or 49.3%) and species (58) were made in Sverdlovsk Oblast, while the fewest occurrences (174 or 1.3%) and species (3) were made in Kurgan Oblast ( The Udmurt Republic and the Perm Krai are located in the Cis-Urals Region. The area of the Udmurt Republic is about 42,100 km . In the north-south direction, the Region stretches across 270 km (56°00' N and 58°30' N) and in the west-east direction, 180 km (51°15'E and 54°30' E). The Perm Krai is located within 61°39′-56°06′ N and 51°47′-59°39′ E. The area of the Region is 160,600 km . In the north-south direction, the Region stretches across 600 km and in the west-east direction, 400 km. The territory of Udmurtia and most of Perm Krai are situated in the north-east of the East European Plain. The relief is predominantly flat, with alternating hills and depressions. The eastern districts of the Perm Krai are situated in the foothills of the Middle and Northern Urals. The relief varies from ridgy hilly to low-and medium-hilly (Ovesnov 1997, Tuganaev 2000. The next three Regions (Republic of Bashkortostan, Chelyabinsk Oblast and Sverdlovsk Oblast) are located within the Urals physical-geographical mountainous country. The Republic of Bashkortostan is located within 51°31′-56°34′ N and 53°10′-59°59′ E. The area of the Republic is 143,600 km . In the north-south direction, the Region is 550 km long and 450 km wide in the west-east direction. The Chelyabinsk Oblast is situated between 51º57´-56º22´ N and 57º05´-63º25´ E. The area is 87,900 km and its length from the north to the south is about 490 km and from the west to the east, it is about 400 km. The Sverdlovsk Oblast area is 194,800 km . In the north-south direction, the Region is 660 km long (from 56º03' N to 61º57' N) and is 560 km wide in the west-east direction (from 57º14' E to 66º11' E). Most of the territory of the Regions are located in the mountainous part of the Urals. The extreme parts of the Regions are the eastern edge of the East European Plain, which corresponds to a flat and hilly relief. The eastern part of 2 2 2 2 2 Table 2.

Number of species and occurrences in the studied regions
Sverdlovsk Oblast and Chelyabinsk Oblast includes sections of the West Siberian lowlands and have a typically flat relief (Kulikov 2005, Kulikov et al. 2013.
Kurgan Oblast and Tyumen Oblast, Khanty-Mansi Autonomous Okrug -Yugra and Yamal-Nenets Autonomous Okrug are located in the Trans-Urals within the West Siberian Plain with the adjacent eastern macro-slopes of the Northern, Circumpolar and Polar Urals. The area of the Tyumen Oblast is 1,464,200 km , its length from south to north is 2,100 km (55°10ʹ-77°30ʹ N) and from west to east is 1,400 km (58°50ʹ-86°00ʹ E). The Region is comprised of three independent subjects of the Russian Federation: the Tyumen Oblast (with the area of 160,100 km ), Khanty-Mansi Autonomous Okrug -Yugra (with the area of 534800 km ) and Yamal-Nenets Autonomous Okrug (with the area of 769,300 km ). The area of the Kurgan Oblast is 71,500 km , its maximum length from the north to the south is 290 km (56°48'-54°14' N), from the west to the east is 430 km (62°06'-68°37' E). The main type of relief are plains, with elevations up to 250-300 m, located mainly along the right banks of the large rivers -Ob and Irtysh (Ogorodnov 1971, Gvozdetskiy 1973, Larin 2004, Naumenko 2008.
In general, the climate of the Urals is characterised by continentality, expressed in sharp annual fluctuations in air temperature and a moderate amount of atmospheric precipitation.
As an obstacle to the movement of air masses from west to east, the Urals restrains and weakens the influence of the Atlantic Ocean on the eastern territories. Behind the Urals, there is a so-called "rain shadow": there is less precipitation here than in the Cis-Urals. The annual amount of precipitation in the plains of the Cis-Urals is 450-600 mm. In the mountains of the Northern Urals, 800-850 mm (in some places more than 1000 mm) of precipitation fall annually and the average annual amount of precipitation decreases to 450-650 mm in the Middle Urals and 300-320 mm in the South Urals. In the Trans-Urals, the annual amount of precipitation ranges from 300-350 mm in the flat southeast and north to 450-600 mm in the central part, reaching a maximum in the mountains of the Subpolar and Polar Urals is more than 700 mm (Ovesnov 1997, Tuganaev 2000, Kulikov 2005, Naumenko 2008, Kulikov et al. 2013. Moving from the north to the south, the climate becomes warmer: the average annual temperature increases from -8°C to +2°C, the duration of snow cover decreases from 170-180 to 145-160 days, respectively. The growing season (with average daily temperatures above +5°C) increases from 60 days in the north of Tyumen Oblast and 110-120 days in the northern parts of the mountainous Urals to 160-170 days in the South Trans-Ural. The hydrothermal coefficient in the northern regions is 1.8-2.0, in the central regions, it is 1.4-1.6 and in the warmest southern regions, it varies from 0.6 to 1.1. In the Cis-Urals, the sum of positive temperatures above +10°С ranges from 1250-1300°С in the northeast to 1950-2000°С in the south-western regions. In the mountainous part and the Trans-Urals, the sum of temperatures varies from north to south from 1000-1250°C to 1400-1700°C. The highest values of the sum of temperatures are observed in the southern regions of Bashkiria and the Chelyabinsk Oblast and these are 2000-2300°C (Ogorodnov 1971, Gvozdetskiy 1973, Ovesnov 1997, Tuganaev 2000, Larin 2004, Kulikov 2005, Naumenko 2008, Kulikov et al. 2013). The study area is located within five vegetation zones: tundra, forest-tundra, forest, foreststeppe and steppe. Forest vegetation occupies most of the studied area. In the mountainous regions, on the western slope of the Northern and Middle Urals, the most widespread dark coniferous forests are Picea obovata and Abies sibirica, usually with a greater or lesser admixture of Betula sp. and sometimes Tilia cordata (as an undergrowth).
In the northern part of the Sverdlovsk Oblast and Perm Krai, there are forests with Pinus sibirica. In the Cis-Urals, on the western macroslope of the southern part of the Middle and northern part of the Southern Urals, there are coniferous broad-leaved forests of Picea obovata and Abies sibirica with a more or less significant admixture of Tilia cordata, Ulmus glabra and Acer platanoides. On the territory of the Republic of Bashkortostan (the southern part of the Bashkir Cis-Urals) and adjacent areas of the Chelyabinsk Oblast, broad-leaved mixed forests of Tilia cordata, Ulmus glabra, Acer platanoides prevail, but areas of Acer platanoides and Quercus robur forests with a slight admixture of other broadleaved species are also common. The eastern slope of the Urals and the northern part of the West Siberian Plain are territories with a continuous predominance of pine forests (Pinus sylvestris) with an insignificant admixture of Larix sibirica (Ovesnov 1997, Tuganaev 2000, Kulikov 2005, Puzyrev 2012, Kulikov et al. 2013).
In the mountains, near the upper border of the forest (in the subalpine belt), there is a strip of sparse Picea obovata, Larix sibirica and Pinus sibirica forests alternating with a birch krummholz formation, Juniperus sibirica knee timbers and subalpine tall grass meadows. Above, it is a belt of mountain tundra (alpine). The mountain-tundra vegetation is dominated by shrub-lichen and grass-moss mountain tundra; other types of tundra communities (Vaccinieto-uliginosi-lichen, Salicetum, Betuletum nanae, Juncus-dominated, Dryas and Arctous alpina communities) are much less common.
Forest-steppe vegetation is represented by two areas. The first is located in the western part of the study area (the Cis-Ural forest-steppe): the Kungur forest-steppe in the Perm Krai, the Krasnoufimskaya forest-steppe in the Sverdlovsk Oblast and the Mesyagutov forest-steppe in Bashkiria and in the western part of the Chelyabinsk Oblast. The vegetation cover here is represented by a combination of birch, aspen, pine-birch and oakbirch groves on the northern slopes of hills, in ravines and depressions of the relief with motley-grass meadow steppes and steppe meadows on gentle slopes of hills and river valleys.
The second area of forest-steppe vegetation is located in the east, in the southern part of the Urals sector of the West Siberian Plain (the forest-steppe of the Trans-Urals). This territory covers the Kurgan Oblast, the east of the Chelyabinsk Oblast and Sverdlovsk Oblast and the south of the Tyumen Oblast. The vegetation consists of birch and aspenbirch 'kolok' (forest in the steppe), small areas of steppe pine (Pinus sylvestris) and pinebirch (Pinus sylvestris+Betula alba s.l.) forests, alternating with areas of steppe meadows, meadows and petrophytic steppes.
The steppe zone occupies the southern part of the Trans-Urals within the Chelyabinsk Oblast and Bashkiria and is also represented in the southern part of the Bashkir Cis-Urals. The vegetation cover is represented on the watersheds by communities of true herb-feather-grass and feather-grass-fescue steppes. In hollows with more abundant moisture, there are areas of meadow steppes and steppe meadows. Petrophytic steppes are widespread along the outcrops of rocks on the tops and slopes of the ridges (Ovesnov 1997, Kulikov 2005, Naumenko 2008, Kulikov et al. 2013.
The Tyumen Oblast is one of the most water-logged regions of the world. Swamps occupy more than 50% of the area here. For the Northern, Subpolar and Polar Urals, within the boundaries of the region, a low-mountainous and, in part, a middle-mountainous relief are characteristic. At the level of 61-62°N passes the southern boundary of the distribution of permafrost. In the north of the Tyumen Oblast, there are forest-tundra and tundra vegetation, dominated by dwarf birch (Betula nana L.) and moss-lichen tundra (Ogorodnov 1971, Gvozdetskiy 1973, Larin 2004.

Taxonomic coverage
Description: The dataset includes 13,742 observations of two classes, Lycopodiopsida and Polypodiopsida. The dataset contains information on three families, seven genera, 12 species, two subspecies and two interspecies hybrids of Lycopodiopsida and 13 families, 21 genera, 53 species, two subspecies and seven interspecies hybrids of Polypodiopsida.
The largest number of the Pteridophyte species was recorded in Sverdlovsk oblast (58 species), in Chelyabinsk oblast (51 species) and the Republic of Bashkortostan (51 species) ( Table 2).

Temporal coverage
Notes: The presented dataset contains information on the occurrences of lycophytes and ferns since 1853, with the most recent findings recorded in 2021 (Fig. 2). Fig. 4 shows that, in 19 century and in early 20 century, the number of findings of lycophytes and ferns was small. The number of occurrences increases by the second half of the 20 century, with the largest number of records registered between 1951 and 2000. This result is connected with the growing interest in the study of the flora of the Urals in general and the active work conducted by the regional research institutes. th th th Figure 1.
The species with the largest number of occurrences (species with more than 400 records are shown).

Figure 2.
Number of occurrences in temporal scope.