Geosystems of the northeastern Hovsgol region

We examine the main natural features and the present status of geosystems across the territory of the northeastern Hovsgol region. The source of observational evidence concerning the state of the landscapes was provided by field expedition-based investigations, with emphasis placed on the study of the species and age composition of vegetation in conjunction with dynamical processes as well as geomorphological characteristics of the study area. The present status of geosystems across the study territory was analyzed by methods of visual interpretation and automated processing of spatial information using GIS technologies on the basis of Earth remote sensing data, field investigations of landscapes, topographic maps as well as literature sources. Special attention was paid to the analysis of the digital elevation model that was generated on the basis of SRTM 4 data in order to determine the morphometric characteristics of the location of geosystems, assign them to a particular type of classification of geosystems and compile the map legend. The legend to the landscape map was produced on the basis of a classification of a number of geomers as developed by V.B. Sochava in his theory of geosystems. As a result of the work done, we compiled the medium-scale landscape-typological map of geosystems (Sc 1:200000) on the level of groups of facies.


Introduction
The Hovsgol region is a peculiar mountain area of Mongolia, with Lake Hovsgol lying in its middle part. This area is located between Eastern Sayan in the north, the Tuva upland in the west, the offspurs of the upland ranges of Khangai and Sangilen in the south and south-west, and Khamar-Daban Range in the east. In the west, north and north-east, the Hovsgol region is delimited by the state border of Russia and Mongolia, in the south by the latitudinal segments of the valleys of the Egiin-Gol, Delger-Muren and Beltesiin-Gol rivers, and in the east by the upper reaches of the left tributaries of the Uur-Gol river.
Structural features of topography permit us to identify two dramatically differing areas: the Western and Eastern Hovsgol regions, and the boundary between them is arbitrarily delimited along the valleys of the Khankh-Gol and Egiin-Gol rivers [1]. The lake basin itself is represented by the hollow of the western flank of the Baikal rift zone, with the water edge at 1645 m above the sea level and 262 m in depth [2].
Almost the entire north of the Eastern Hovsgol region is occupied by the Kheven-Zaluu Uriiin Sardyk highland stretching over 80 km from north to south and reaching absolute heights of 2300-2550 m. It represents an ancient planation surface armored by basalts. Because of erosional dissection, the marginal areas of the highland have the appearance of low and middle mountains, whereas the inner areas are weakly dissected. The low-mountain relief with insignificant relative heights and elevations as well as with smooth outlines of the slopes mostly occurs to the south of this highland in the Eastern Hovsgol region [3].
The area has an extreme continental climate, with the mean annual temperature of 4.5°С. The mean long-term precipitation amount is 300 mm/year, with its maximum corresponding to a warm period [2].
Altitudinal zonality is the main composition pattern of vegetation cover of the northeastern Hovsgol region. The nival, high-mountain, mountain-taiga and mountain-steppe belts are identified. The mountain-taiga and mountain-steppe belts occur from the level of Lake Hovsgol (1645 m above the sea level) to the lower boundary of the goletz belt (about 2000 m above the sea level); this belt is dominated by larch (Larix sibirica) and Siberian stone pine (Pinus sibirica) forests as well as by steppes and meadows.
The goletz belt occupies habitats at altitudes from 2000-2100 to about 2600 m above the sea level where there occur yernik shrubs (Betula rotundifolia and B. humilis) and mountain tundras. The above-lying nival belt is represented by glaciers of the Munku-Sardyk massif (3491 m) and alpinotype relief.

Models and methods
In investigating the present status of the geosystems of the northeastern Hovsgol region, e used information of different quality: remote sensing data, cartographic material, material of ground-based investigations, and GIS databases: 1) high spatial resolution images (Landsat 5 TM, Landsat 7 ЕTM+, and Landsat 8 OLI.); 2) 1:100 000 and 1:200 000 topographic maps; 3) SRTM 4 data, and 4) expedition material.
To objectively reveal the specific features in the spatial occurrence of geosystems used a DEM on the basis of SRTM 4 data [4][5][6]. The steepness and aspect of the slopes were calculated. The resulting GRID models were exported to the MapInfo vector form, representing an array of points at regular steps of 90 m. As a result of an objective combination of GRID with the geosystem contours obtained from interpretation, it is possible to carry out a quantitative analysis.
Factual evidence concerning the structure and present status of geosystems of the northeastern Hovsgol region was obtained as a result of field work in the year 2018, with investigations made into the most important components of the geosystems: vegetation communities and geomorphological characteristics of the study area. The focus in the study of vegetation cenoses was not only on the species composition but also on the general status of cenoses, and on dynamical processes. Geobotanical descriptions were made by classical techniques [7,8] complemented with brief characteristics of the status of cenoses along he routes as well as using photographic recordings.

Results and discussion
As a result of the research done, we compiled the medium-scale 1:200 000 map for the geosystems (table 1, figure 1). The map legend consists of 28 numbers of primary geosystems and 5 numbers of secondary communities. A classification of the geosystems was accomplished in accordance with the principles of Academician V.B. Sochava's theory of geosystems [9], for the series. The group of facies was used as the main mapping unit.

Landscape type Goletz Group of geoms Lichen Geom Bushy lichen (Cladonia alpestris and Cetrarira cuculata)
Facies class Flat interfluves (South-Siberian bushy-lichen flat interfluves and flat summits) 3. Lichen tundras with grass microgroups (Kobresia myosuroides and Dryas oxyodonta) with gley tundra skeletal immature soils of habitats of goletz planation at 2200 m above the sea level and higher.