The larch forest of the “Bastak” State Nature Reserve (Jewish autonomous region)

The article presents the information about the current state of the larch forests of the “Bastak”. State Nature Reserve The area, ecological and cenotic conditions of growth are determined, the classification of the studied plant communities is presented, a brief description of the forest structure is given. The current state of the larch forests of the “Bastak” State Nature Reserve can be assessed as fairly stable. Currently, larch forests occupy within 25 % of the forested area. The most widespread area is occupied by lowland larch forests (94 %). Mountain larch forests are derived plant communities formed after forest cutting in fir-spruce forests.


Introduction
The "Bastak" State Nature Reserve is the only federal specially protected natural area (SPNA) located in the territory of the Jewish Autonomous Region (JAR). It was established by the decree of the Government of the Russian Federation No. 96 of 28.01.1998. The Bastak Reserve consists of two cluster plots, namely, "Central" which is located in the northeastern part of the JAR, north of the administrative center of the region, the City of Birobidzhan, and "Zabelovsky" which is in the eastern part of the JAR. It is located in three municipal districts including Birobidzhansky, Obluchensky and Smidovichi. The total area of the reserve is 128055 ha.
The surface of the territory of the "Bastak" Reserve is represented by two types of relief: mountainous (in the north and in the center of the cluster "Central") and plain (in the south of the cluster "Central" and the entire territory of the cluster "Zabelovsky").
The territory of the Bastak Reserve is characterized by an ultracontinental climate with distinct manifestations of monsoon processes. The long-term average annual air temperature is +1.7 °C, which is the norm for areas of moderate monsoon climate. January is the coldest month of the year, with an average monthly temperature of -21°C. The warmest month of the year is July, the average monthly temperature of which was +21°C. The average annual precipitation falling in the territory of the reserve is 931 mm, which is higher than the norm indicated in the literature (600-800 mm) [1]. The humidification regime of the territory is characterized by a pronounced seasonality. The greatest amount of precipitation falls during the warm period, when from 36 % to 75 % of all precipitation fell. The most abundant precipitation falls in July-August (these months account for from 15 % to 63 % of the total 2 precipitation), the minimum amount of precipitation is typical for January-February (0.2-9 % of the total precipitation). The average multi-year date for establishing a stable snow cover is November 10. The average snow cover height for the winter is 22 cm in open spaces and 19 cm in the forest. In general, since 2016, there has been a tendency to a decrease in the height of snow cover both in open spaces and in the forest [2].
The low temperature in winter and the low power of the snow cover contribute to the deep freezing of the soil, reaching 150-200 cm, which worsens the growing conditions of plant communities.
Most of the territory of the Bastak Nature Reserve (75881.7 ha) is represented by forests that are diverse in conditions of growing and species composition. is occupied by swamps and other non-forest vegetation groups. One of the key indicators of the sustainability of forest ecosystems is the forest cover of the territory. According to the materials of the forest management, the total forest cover of the reserve territory is 56 %. The forest cover is extremely uneven in the district forestry, amounting to 96 % in Mountain, 61 % in Ikurinsky, 39 %, in Razdolnensky, and 29 % in Zabelovsky [3].
The purpose of this work is to characterize the current state of the larch forests of the Bastak Nature Reserve. To achieve this goal, it is necessary to solve the following tasks: 1. Defining the ecological and cenotic conditions for the growth of larch trees within the boundaries of the "Bastak" State Nature Reserve 2. Identifying the main dominant of tree stand and structure of the tree layer of the phytocenoses studied.

Materials and methods
The authors determined the growing conditions of the larch forests of the Bastak Reserve, identified the species composition of plant communities in them, and determined the taxational characteristics of the stand during a route survey of the forests of the reserve. The density of routes made it possible to cover almost the entire array of larch forests. During the route survey, geobotanical descriptions of 20 m x 20 m sample areas were completed. The plots that are relatively homogeneous in terms of ecological conditions and floral composition are selected for the description. When describing communities, the following information and dimensions are collected: 1). Geographical location; 2). Geomorphology; 3). Description of the stand (total density of canopies (TDC), average height of the stand, species composition, and the total cover (TC) in %, height, and diameter for each species of tree; 4). Description of the undergrowth (species composition, height of the undergrowth of each tree species and its quantity is estimated in pcs/ha); 5). Description of the undergrowth (TC in %; for each species of shrubs the average height and the cover in % are collected ); 6. The description of the grass layer includes drawing up a complete species list, determining the total cover of the grass layer and each species in %, the average height of each species in meters) [4,5]. The boundaries of the larch forests of the Bastak Reserve are drawn in the ArcMap 10.4.1 program on the basis of multi-season satellite images of Landsat-8, which are freely available via the Internet. We downloaded 11 multi-channel images in the amount of 11 pieces. In QGIS 3.3, the downloaded images were combined into a single color image with a combination of 5-4-3 colors (red, green, blue) and exported to jpeg format. We used the materials of the forest management (2011) and the data of the State Forest Register (as of 01.01.2021) to correction the area of growth of various types of larch forests.

Results and discussion
The edifier of the larch forests of the Bastak Reserve is the Kayandera larch Larix cajanderi Mayar. In the reserve, the studied phytocenoses grow only in the «Central» cluster in the territories of the Mountain, Ikurinsky and Razdolnensky forestry districts (Fig. 1). These plant communities grow both in the mountainous part of the specially protected natural area and on the plain, and, therefore, they are divided into mountain and plain. The total area of growth of larch trees within the «Bastak» Reserve is 15109.1 ha.
We have noted mountain larch forests in the upper reaches of the Big Sorennak, Bastak, Kirga and Ikura rivers. In these plant communities, slope and valley larch forests are distinguished. Slope larch trees grow on fairly steep slopes (slope steepness 20-30°) and narrow watersheds. The soils in the studied communities are strongly stony light-brown permafrost. According to the forest management materials, these plant communities, belong to shrub larch forest (forest type Lsh), green-mossed larch forest (Lgm) and rhododendron larch forest (Lr), and according to the ecological and floral classification, they are attributed to the association Aceri tegmentosi-Laricetum cajanderi Krestov [3,6]. The studied formations are characterized by a simple structure. The floral composition significantly coincides with the vegetation of spruce forests of a specially protected natural area, which allows one to conclude that these plant communities are derived from the spruce forests of the Bastak Reserve. The tree stand is two-layered. In the plain part, we have registered moss and herbaceous larch forests. The moss larch forests grow on gently shaded, often concave slopes, in flow-swampy hollows, on wide and flat slopes and in saucershaped depressions. According to the forest management materials, these plant communities belong to the following types of larch forests: larch-bagulnik-moss (Lbm), sedge (Lo), blueberry-sphagnum (Lbs), sedge-sphagnum (Lso), and sphagnum (Ls), and according to the ecological and floral classification, they are attributed to the associations Chamaedaphno calyculatae-Laricetum cajanderi Krestov [3,6]. Plant communities grow on light-brown permafrost, humus-illuvial, and peat-podzolic-gley soils. The phytocenoses studied are characterized by a fairly simple structure. The stand is mostly single-tiered, and rather sparse (TDC up to 50 %). It is mainly formed by Larix cajanderi Mayr, Betula platyphylla Sukacz., Alnus hirsuta (Spach) Fisch. ex Rupr. The shrub layer is quite dense (TC up to 50 %), and consists of Betula fruticosa Pall. and Betula ovalifolia Rupr., Andromeda polifolia L., Chamaedaphne calyculata (L.) Moench, Sorbaria sorbifolia (L.) A. Br., Rhododendron dauricum L., Vaccinium uliginosum L., Ledum palustre L., Oxycoccus microcarpus Turcz. ex Rupr., Oxycoccus palustris Pers. and other species. The grass layer is rare (TC up to 20 %), represented by Calamagrostis langsdorffii (Link) Trin., various types of sedges forming tussocks (Carex globularis L., Carex minuta Franch., Carex cespitosa L., Carex schmidtii Meinsh.,