Diversity and distribution of vascular plants within the treeline ecotone in Mount Iremel (Southern Urals, Russia)

Abstract Background During the last 100 years, rapid advances of trees towards higher elevations and latitudes have been recorded for various regions worldwide, including the Ural Mountains. Climate warming and tree cover increases can lead to significant changes in the high-mountain vegetation. Direct observations on the vegetation of high-mountain regions provide evidence for an increase in the species diversity of plants at high elevations and changes in the composition of the alpine communities. This study investigated the diversity and distribution of vascular plants within the present-day treeline ecotone in Mount Iremel, the Southern Urals. New information The dataset (Trubina and Nesterkov 2021, available from the GBIF network at https://www.gbif.org/dataset/284f1484-10b7-4ef5-87b7-9de1159e6b42) presents the results of an assessment of species richness and frequency of vascular plants at the different elevation levels (from 1203 to 1348 m a.s.l.) and different biotopes (birch-spruce shrub forest, birch-spruce sparse forest and spruce forest with fragments of meadow plant communities) within the treeline ecotone in Mount Iremel, Southern Urals. Observations were carried out at 700 sampling plots with two estimation methods: small-size plot (0.5 × 0.5 m) sampling (672 plots in total) and large-size plot (10 × 10 m) sampling (28 plots). The dataset includes 700 sampling events (= sampling plots), corresponding to 5585 occurrences (vascular plants, mainly identified to species) observed during July 2003. Only occurrences containing plant taxa (occurrenceStatus = present) have been provided. The dataset includes information about distribution and frequency of the Ural endemic species (Anemone narcissiflora subsp. biarmiensis (Juz.) Jalas, Calamagrostis uralensis Litv., Cerastium krylovii Schischk. & Gorczak., Festuca igoschiniae Tzvel., Hieracium iremelense (Elfstr.) Üksip, Lagotis uralensis Schischk, Pleurospermum uralense Hoffm.) and the Pleistocene relict species (Alopecurus magellanicus Lam., Bistorta vivipara (L.) Delarbre, Cerastium pauciflorum Stev. ex. Ser., Pedicularis oederi Vahl, Saussurea controversa DC., Swertia perennis L.). The dataset also provides information that can be useful for estimating biodiversity and plant communities composition within the treeline ecotone at a specified time period and contributes to the study of biodiversity conservation in the Ural Region.


Introduction
High mountain ecosystems and their biota are driven by low-temperature conditions and can be used as indicators for climate warming impacts on natural ecosystems. In the 20th century, high-mountain forests increased in range and their boundaries changed in different regions of the world (Jakubos and Romme 1993, Shiyatov 1993, Woodward et al. 1995, Holtmeier 2009, Peñuelas and Boada 2003, including the Southern Urals (Shiyatov 1983, Moiseev et al. 2004, Hagedorn et al. 2014). This phenomenon is usually attributed to global warming. Direct observations on the vegetation of high-mountain regions also provide evidence for an increase in the species diversity of plants at high elevations and changes in the composition of alpine communities (Grabherr et al. 1994, Keller et al. 2000, Lamprecht et al. 2018, Løkken et al. 2020, Savage and Vellend 2014. However, the magnitude and direction of upward-elevational shifts of species distribution vary tremendously amongst species and regions, the geographic range of existing studies is relatively sparse and the opportunities for assessing long-term community change provided by historical biodiversity surveys are relatively rare (Savage and Vellend 2014).
Mount Iremel is one of the highest mountains in the Southern Urals. Rapid advances of trees towards higher elevations are well documented (Shiyatov 1983, Moiseev et al. 2004, Hagedorn et al. 2014. Despite the long history of the vegetation studies in this region, assessments of the species richness for the vascular plants at different elevational levels are sporadic and relate either to changes in the species richness for plants with different thermal preferences within a present-day treeline ecotone (Trubina 2006) or to changes in the functional and taxonomic diversity within the treeline ecotone at the single slope (Gazol et al. 2017). Quantitative assessments of the species distribution at the different slopes of this mountain massif have never been conducted. However, due to their geographical location, the mountain tundra and the sub-alpine belt communities of the Southern Urals may be particularly vulnerable to climate warming and the rapid upward movement of trees. Moreover, most of the endemic and relict species of the Urals are extremely vulnerable to environmental changes, as they are associated with high mountain communities and have low population size (Gorchakovskii and Shurova 1982). The dataset includes information about distribution and frequency of the Ural endemic species ( Anemone narcissiflora subsp. biarmiensis (Juz.) Jalas, Calamagrostis uralensis Litv., Cerastium krylovii Schischk. & Gorczak., Festuca igoschiniae Tzvel., Hieracium iremelense (Elfstr.) Üksip, Lagotis uralensis Schischk, Pleurospermum uralense Hoffm.) and the Pleistocene relict species (Alopecurus magellanicus Lam., Bistorta vivipara (L.) Delarbre, Cerastium pauciflorum Stev. ex. Ser., Pedicularis oederi Vahl, Saussurea controversa DC., Swertia perennis L.). The dataset also provides helpful information for estimating the biodiversity and composition of plant communities within the treeline ecotone at the different slopes and at a specified time period and contributes to the study of biodiversity conservation in the Ural Region.

Project description
Title: Diversity and distribution of vascular plants within the treeline ecotone in Mount Iremel (Southern Urals, Russia) Study area description: Mount Iremel is located in the region of the highest elevation of the Southern Urals within the Iremel-Avalyak mountain region (Fig. 1). On the joint base of Mount Iremel, two peaks rise -the second largest one of the Southern Urals, Bol'shoy Iremel (1582 m a.s.l.) and Malyy Iremel (1450 m a.s.l.). The average annual temperature is 0.3°C and the precipitation average is 600-700 mm, which is typical for the northeast of the mountainous part of the Bashkortostan. The mountain forest, subgoltzy (subalpine) and mountain tundra belts are distinguished in the vegetation of Mount Iremel (Gorchakovskii 1975). The subalpine zone extends from 1100-1150 m to 1350-1400 m a.s.l.. Park-type open spruce and spruce-birch forests and tall-herb meadows, dominated by Alpine knotweed (Persicaria alpina) and snakeweed (Persicaria bistorta), are characteristic for its lower part. In contrast, spruce and birch shrub forests with small-herb meadows prevail in their upper part ( Fig. 2) (Nikonova et al. 1992). The range of elevations occupied by the mountain tundra belt is about 200 m. The herb-moss tundra type prevails, but stony, lichen, dwarf shrub-moss and complex tundra types are also presented (Sharafutdinov 1983). Siberian spruce Picea obovata and birch Betula tortuosa are the main tree species forming the treeline. Currently, Mount Iremel has been assigned the status of a nature park. Location of the macro-plots at the slopes of the mountains Bol'shoy and Malyy Iremel, Southern Urals (data from Open Street Map; numbers of the macro-plots correspond to those in the dataset).

Study extent:
The study was carried out in the Southern Urals, Russia, within the Iremel mountain group, at the slopes of the mountains Bol'shoy (54.52000°N, 58.84167°E) and Malyy (54.55167°N, 58.89167°E) Iremel. A total of 700 sampling plots (672 plots of 0.5 × 0.5 m and 28 plots of 10 × 10 m) were established in three types of biotopes: 300 plots in a birch-spruce sparse forest, 300 plots in a spruce forest with fragments of meadow plant communities and 100 plots in a birch-spruce shrub forest. The study was completed in July 2003.
Sampling description: Vertical transects (Fig. 3) were established within the present-day treeline ecotone at the south-western and southern slopes of mount Malyy Iremel and the north-eastern slope of mount Bol'shoy Iremel (three transects on each slope, nine transects in total). At the southern slope of Malyy Iremel and the north-eastern slope of Bol'shoy Iremel, within each transect, two elevation levels were identified corresponding to biotope types (birch-spruce sparse forest and spruce forest with fragments of meadow plant communities). At the south-western slope of Malyy Iremel, three elevation levels were identified (the corresponding biotopes are birch-spruce sparse forest, birch-spruce shrub forest and spruce forest with fragments of meadow plant communities). Detailed characteristics of the biotopes were published earlier (Trubina 2006).
Three sampling sites, 20 × 20 m (also referred to as macro-plots (= locationID in the dataset, 21 in total), were established within each elevation level. The central points of the sampling sites were positioned at a distance of 50-70 m from each other. Each macroplot was divided into four subplots of 10 × 10 m. At each elevation level, within two macroplots, 12 plots with a size of 1 × 1 m were located (total number 168), within which, in turn, four sampling plots with a size of 0.5 × 0.5 m were placed (total number 672). The small plots with a size of 0.5 × 0.5 m were established for assessment of plant species frequency. Within the third macroplot at each elevation level, the sampling was carried out only in subplots with a size of 10 × 10 m (total number 28).
The sampling process included direct observations and active search to find all vascular plant species in understorey vegetation in sampling plots of two sizes (0.5 × 0.5 m and 10 × 10 m). Sampling effort (time interval for describing all plants in one sampling plot) was approximately 10 minutes for small-sized plots and 50 minutes for large-sized plots. A large number of plots (700 in total) made it possible to take into account the irregularity in distribution of plant species within the study sites. The use of small-sized sampling plots allows obtaining quantitative data (frequency of species) to estimate the species abundance.
Quality control: Identification of plant species was carried out mainly in the field; specimens with controversial species affiliation were herborised and identified later in a laboratory by specialists from the Institute of Plant and Animal Ecology of the Ural Branch of the Russian Academy of Sciences (IPAE UB RAS). Identification was cross-checked by specialists from the Institute Botanical Garden of the Ural Branch of the Russian Academy of Sciences (IBG UB RAS).

Geographic coverage
Description: Sampling plots were founded at an altitude of 1200-1350 m a.s.l. within the present-day ecotone of the upper forest line. At the southern slope of Malyy Iremel and the north-eastern slope of Bol'shoy Iremel, plots were located in two types of biotopes (birchspruce sparse forest and spruce forest with fragments of meadow plant communities); at the south-western slope of Malyy Iremel in three types of biotopes (birch-spruce shrub forest, birch-spruce sparse forest and spruce forest with fragments of meadow plant communities).

Data format: Darwin Core
Description: The dataset presents the results of an assessment of the species richness and frequency of vascular plants at the different elevation levels (from 1203 to 1348 m a.s.l.) and in the different biotopes (birch-spruce sparse forest, birch-spruce shrub forest and spruce forest with fragments of meadow plant communities) in the Iremel mountain group (Southern Urals). Observations were carried out at 700 sampling plots using two estimation methods: small-size plot (0.5 × 0.5 m) sampling (672 plots in total) and large-size plot (10 × 10 m) sampling (28 plots). The dataset includes 700 sampling events (= sampling plots) corresponding to 5585 occurrences (vascular plants, identified mostly to species) and observed during July 2003. Only occurrences containing plant taxa (occurrenceStatus = present) have been provided. The dataset provides valuable information for estimating the biodiversity and composition of plant communities within the treeline ecotone, including the information about distribution and frequency of the Ural endemic species ( The geographic latitude (in decimal degrees, using the spatial reference system given in geodeticDatum) of the geographic centre of a Location. decimalLongitude The geographic longitude (in decimal degrees, using the spatial reference system given in geodeticDatum) of the geographic centre of a Location.
geodeticDatum The ellipsoid, geodetic datum or spatial reference system (SRS) upon which the geographic coordinates given in decimalLatitude and decimalLongitude are based.
coordinateUncertaintyInMetres The horizontal distance (in metres) from the given decimalLatitude and decimalLongitude describing the smallest circle containing the whole of the kingdom The full scientific name of the kingdom in which the taxon is classified. phylum The full scientific name of the phylum or division in which the taxon is classified. class The full scientific name of the class in which the taxon is classified. order The full scientific name of the order in which the taxon is classified. family The full scientific name of the family in which the taxon is classified.

genus
The full scientific name of the genus in which the taxon is classified.
specificEpithet The name of the first or species epithet of the scientificName.
identificationRemarks Comments or notes about the Identification. taxonRank The taxonomic rank of the most specific name in the scientificName. recordedBy A list (concatenated and separated) of names of people, groups or organisations responsible for recording the original Occurrence.
identifiedBy A list (concatenated and separated) of names of people, groups or organisations who assigned the Taxon to the subject.