FLORISTIC COMPOSITION AND BIOLOGICAL SPECTRUM OF THE BOGDKHAN MOUNTAIN, MONGOLIA

The Bogdkhan mountain of Mongolia is strictly protected and possesses a unique ecosystem, because of its location in the transitional zone of Siberian taiga and the Asian steppe. Floristic composition and the biological spectrum of the Bogdkhan Mountain were studied during July 2019 to September 2020. A total of 522 vascular plants were recorded belonging to 249 genera and 63 families. Asteraceae was found to be the most dominant family (13.22%; 33 genera and 69 taxa) followed by Poaceae (8.43%; 21 genera and 44). The classified life-form spectra of all the species recorded from the study area revealed the predominance of hemicryptophytes (63.03%) followed by geophytes (11.30%), therophytes (10.34%), phanerophytes (9.58%), chamaephytes (5.36%), and hydrophytes (0.38%). The notable changes found in the biological spectrum, which are chamaephytes from 12 to 5.36%, geophytes from 8 to 11.30% and therophytes from 8 to 10.34%. Variaty of reasons might cause change the life form, such as climate change, anthropogenic impacts, etc. Hemicryptophytes and chamaephytes dominate the flora of the mountain due to the cold mountain niche. The floristic diversity of this mountain tends to decline further videnced from the observed lesser divergence values of geophytes and therophytes.


Introduction
The Bogdkhan Mountain is one of the well known protected areas of Mongolia and the oldest continuously protected areas of the world (Jargal, 2003;Wurts, 2013) and is located in the southwest of the Khentei Mountain range (Tsegmid, 1969). Phytogeographically, it is included in the region of Khentei mountain taiga (Junatov, 1977;Grubov, 1982;Ulziikhutag, 1989), also to the region of Transbaikalian mountain -hillock forest-vegetation following forest-vegetation classification (Junatov, 1977;Tsedendash, 1995). Previous studies recorded 2823 taxa of vascular plants belonging to 662 genera and 128 families for the flora of Mongolia, out of which 1087 species were recorded from the region of Khentei mountain taiga (Gubanov, 1996). In addition, 44 taxa of vascular plants were further added for Khentei Mountains (Dulamsuren and Mühlenberg, 2003).
The Bogdkhan Mountain is in a mountainous forest-steppe zone with a predominance of larch forests, rich pine forests, spruce forests that follow the upper reaches of small mountain ranges and very small areas of pine (Junatov, 1977;Ganbold et al., 1993;Dugarjav, 2006). This area is considered to be the southern border of the Mongolian taiga forest. The steppe vegetation is broadly distributed on this mountain slopes and meadow steppe and meadow vegetation can be seen at the foot of the mountain and sub-belts such as pseudo-taiga, subtaiga, taiga and subgoltsy (Tsedendash, 1995).
The first floral investigation in the Bogdkhan Mountain, was carried out by the Soviet-Mongolian Joint Biological Expedition team in [1989][1990] which recorded 579 species belonging to 259 genera and 69 families (Ganbold et al., 1993). Further, 26 species were newly added to this list by Hilbig et al. (2004). The vegetation of the Bogdkhan Mountain, categorized under 17 different vegetation communities comprising of four altitude levels (hillock, lower montane, upper montane, and subalpine belt), grouped under 20 distribution types (Hilbig et al., 2004). However, Enkhmaa (2015) recorded 746 species belonging to 295 genera and 75 families, however, the checklist and information of herbarium where the collections were deposited, were not provided. In addition, Sanchir (2008), and Enkhmaa (2017) reported a number of threatened and economically useful plants from this area.
In terms of climate change in Mongolia, there is a temperature rise by 1.66 º C during 1940 to 2001 (Batima et al., 2005). According to an estimate, the temperature is further expected to rise by 5-7 º C, along with summer precipitation by 40-60 mm till 2100 in mountainous regions (Bayasgalan et al., 2009). Hence, changes in vegetation communities and between ecosystems have been increasing (Dulamsuren et al., 2011;Natsagdorj, 2012;Bolormaa et al., 2017).
Considering the above facts, the ecosystem of Bogdkhan Mountain is vulnerable because of its isolated location at the southernmost point of the Khentei Range, which is adjacent to the steppe to the south and closest to the most densely populated Ulaanbaatar city. The Bogdkhan Mountains have further been exposed to tourism, construction, and approach roads (Erdenechimeg, 2013;Naranbaatar et al., 2018;Gradel et al., 2019). Tourism operations are actively developing 'ger' (Mongolian traditional house) camps in 24 valleys; and about 17 thousand livestock graze in Bogdkhan Mountain (Erdenechimeg, 2013;Naranbaatar et al., 2018). It was documented that 22.4% of pastures were overgrazed and 10.9% were polluted or damaged (Erdenechimeg, 2013). The landscape cover decreased by 0.8 -2.6% in the forest, meadow, and shrub area, and the steppe area increased by 1.5% (Naranbaatar et al., 2018). Moreover, many regular activities such as jogging, hiking, skiing, the traditional prayer for mountain, and shamanic rituals, and other seasonal activities such as picking nuts, fruits, and mushrooms have negatively affected the flora of the Bogdkhan Mountain to some extent (Erdenechimeg, 2013;Naranbaatar et al., 2018). Therefore, we aimed to conduct detailed floral investigations for the Bogdkhan Mountain and to understand its floristic composition, diversity and ecology. We hypothesized that the Bogdkhan Mountain ecosystem might be changing rapidly and becoming more vulnerable because of its geographical-transitional location and diverse drivers. Furthermore, investigation of vegetation and diversity will allow a better understanding of the natural changes which may ultimately contribute to efficient management of the protected areas of Mongolia.

Materials and Methods
Study area: The Bogdkhan Mountain is a protected area located 30-40 km south of Ulaanbaatar city with relative altitude of 1200-1500 m, and absolute altitude of 2268 m above sea level with its highest peak, called Tsetsee-Gun (Fig. 1). The mountain area is 41,651 ha, thereof forest area covering 53.2% or 22,129 ha square (Shirendev and Munkhtuya, 2015). Tuul River, one of the biggest rivers in Mongolia flows by northern downhill of Bogdkhan Mountain. The topography is alpine, rugged and mostly steep and streams originated from the valleys (MNEM, 1998). The main annual average temperature is -0.5 ºC, the coldest month is January, with a minimum average temperature of -22.5 ºC, and the warmest month is July, with a maximum average temperature of 18.7ºC. The average WI and CI for three stations are 45.1 and -41.9, respectively. The annual average total precipitation is 268.5 mm, and summer precipitation occurs between May and September and accounts for 86.5% of the total annual rainfall (Table 1). Taxonomic method: Fourty field surveys were conducted 5 times during flowering seasons in June, July, August of 2019; July and August of 2020. Twenty-five sampling points, including eleven largest valleys of Bogdkhan Mountain, were targetted during the field trip and 1200 voucher specimens were collected from mountain steppe, mountain slopes, meadow, riverside, forest fringes, larch forest, pine forest, spruce forest, mixed forest, and rocks ( Fig. 1; Table 2). Samples of each taxon were prepared following standard herbarium techniques (Maden, 2004) and deposited in the Herbarium of Natural History Museum of Mongolia (MMNH). These specimens were identified using the key to the Vascular Plants of Mongolia (Grubov, 1982) and several volumes of Flora of Mongolia (Nyambayar, 2009;Urgamal, 2009;Dariimaa, 2014;Dariimaa and Saruul, 2017;Dariimaa et al., 2015). Plant classification followed APG IV (2016), and nomenclature according to Plants of the World Online (POWO, 2020), and International Plant Names Index (IPNI, 2020). The analysis of floristic characteristics was based on the total number of species including the collection of vascular plant specimens in investigated areas. Besides, earlier specimens collected from the study area and deposited in the herbaria such as Moscow University (MW), Central Siberian Botanical Garden (NSK), Gatersleben (GAT), Institute of Botanical Garden and Research, Mongolian Academy of Science (UBA), National University of Mongolia (UBU), and Natural History Museum of Mongolia (MMNH) were also consulted. In table 6, family and taxa names are listed in alphabetical order and each is presented with the following information: accepted name with authority, family name, life-form, chorotypes, global and regional red list categories, endemism, and relict. A biogeographical analysis was performed according to Tolmachev (1974) and Ganbold (2010) based on plant distribution and phytogeographic origin. Each taxon was categorized into five large distributional groups; the Asian group was divided into 8 subgroups. Chorotypes, life-form are marked with their abbreviations (Table 6). Threatened species were defined according to International Union for Conservation of Nature (IUCN, 2020); Regional Red List (Nyambayar et al., 2011;Tsendeekhuu et al., 2019) and Mongolian Red Book (Shiirevdamba et al., 2013). Endemism was defined according to the conspectus of flora in Mongolia (Urgamal et al., 2014;Urgamal and Ouyntsetseg, 2017) and relict plants were noted according to Ulziikhutag (1989).
In addition, Pearson correlation was applied to compare the result life-form spectrum of the present study with different studies.
-correlation coefficient; x -values of the x-variable in a sample; ẋ -mean of the values of the x-variable; y -values of the y-variable in a sample; ẏ -mean of the values of the y-variable.
Biological spectrum: Of the total species recorded from the study area, 88.31% are herbs (461 taxa), 5.55% shrubs (29), 5.17% trees (27), 0.57% creepers (3) and 0.38% climbers (2). The biological spectrum showed that hemicryptophytes were the dominant life-forms, accounted for 329 species, 63.03% of all species in the mountain, followed by geophytes 59 (11.30%), therophytes 54 (10.34%), phanerophytes 50 (9.58%), chamaephytes 28 (5.36%) and hydrophytes 2 (0.38%) ( Table 4). In addition, the observed flora was compared with Raunkiaer's (1934) normal spectrum which accounts for altitudinal zones in the northern cold temperate. The Ẋ 2 test results showed significant differences between the Bogdkhan Mountain and Raunkiaer's normal spectrum (p˂0.05). The observed proportions were higher than expected for the phanerophytes, geophytes and therophytes. Chamaephytes (3.67) had the highest individual value determined from the Ẋ 2 test, followed by geophytes (1.36) and therophytes (0.69) ( Table 4).  We compared the life-form spectrum of the present study with the results of previous studies that were conducted in neighboring phytogeographical regions (Table 5). There was a likeness between neighbor phytogeographical regions. The results of Ẋ 2 test and correlation analysis demonstrated a significant correlation between the life-form spectrum in the Bogdkhan Mountain and those of other studies investigated in the neighboring regions which are Khangai and Mongol Daurian forest-steppe, Middle Khalkha dry steppe.
For biological spectrum, we compared our results with the earlier studied three different phytogeographical regions (Khongor district in the forest-steppe of Mongol-Daurian, Khustai National Park in the steppe of Middle-Khalkha, Ulziit Mountain in the forest-steppe of Khangai Mountain). Correlation coefficient was found to be very similar (0.989; 0.988; 0.995) to each other. The study showed that all study areas were in the same cold temperate zone of climate condition. Despite the similarity of the biological spectrum, the vegetation structure and species composition of the flora were considerably different (Fig. 4). environmental factor will increase therophytes, but also diverse anthropogenic impacts, such as unregulated tourism, timber harvesting, population settlement etc. In addition, an increase of therophytes causes humidity extremes and water shortages (Moradi et al., 2009). We agree with the conclusion of Hilbig et al. (2004) that the conditions of the Bogdkhan Mountain change rapidly due to anthropogenic influences. The underlying causes for the increasing anthropogenic influences are related to land use, which has been intensified near the city of Ulaanbaatar since the 1990s during the transitional phase of socialism to a democratic society (Erdenechimeg, 2013;Naranbaatar et al., 2018;Gradel et al., 2019). Asian elements with 8 subgroups occupied the most percentage followed Eurasian, Holarctic, Asia-American and Cosmopolitan elements, which were influenced to this mountain vegetation. It is in agreement with the results reported by previous studies (Ulziikhutag, 1989;Ganbold, 2010;Tserendulam et al., 2018;Batdelger et al., 2021). The presence of endemic, relict and vulnerable (8 Vulnerable, 2 Endangered and 1 Critically Endangered) species emphasizes on the need for conserving the rich flora of Bogdkhan Mountains. Cold temperate with mountainous climate conditions in the Bogdkhan Mountain might allow hemicryptophytes and chamaephytes to be dominant. We consider that the floristic composition of Bogdkhan Mountain could be decreasing in future, due to increasing of therophytes. Given such a situation, the causes for decreases in mountain flora are influences of anthropogenic factors, especially population settlements, and constructions in the mountain. In addition, it was noted that overgrazing in some parts of the studied area, especially in the lower belt of the mountain, has led to an increase in therophytes. Therefore, overgrazing is viewed as a cause of the deterioration of the ecosystem in the area. We finally conclude with a strong recommendation to improve the protection management of the Bogdkhan Mountain in the near future.