Bioclimatic variants of the Northeastern Transbaikalia Orobiome

Introduction. The spatial structure of the biota at the regional level of its organization is most closely associated with the climate, expressed primarily through bioclimatic indicators. In the geography of the botanical diversity of Northeastern Transbaikalia, which is characterized by a complex organization of vegetation cover, the influence of a number of important gradients of climatic conditions is expressed. The identification of these gradients was the purpose of this research. Methods and materials of the research. The methodological basis of the research was the ecosystem approach to the identification and evaluation of phytocenotic diversity associated with ecological and geographical factors that determine its spatial differentiation. The geographic and genetic classification of plant communities was used to identify the typological diversity of vegetation. The climatic characteristics of the Northeastern Transbaikalia was given on the basis of key bioclimatic indicators (global model BioClim). The bioclimatic substantiation of the spatial structure was carried out taking into account the principles of identifying the diversity of ecosystems at the regional level. Mapping of the bioclimatic variants of the orobiome was compiled using the clustering of units according to the average values of parameters by the k-means method. Research results and discussion. A joint analysis of vegetation and climate made it possible, for the first time for Northeastern Transbaikalia, to determine the internal structure of ecosystem diversity that develops in the mountains within the framework of an orobiome. It also allowed mapping the spatial organization of ecosystems at the regional level on a climate basis. Using the cluster analysis of climatopes of the main vegetation formations, subdivisions of the orobiome (bioclimatic variants) are proposed. Two variants of the Ist order are expressed through the structure of the vegetation cover of mountain systems: the relatively low Patom highland in the north, and more massive ridges of the strongly dissected North Baikal and Stanovoy highlands in the south. Variants of the IInd order, differing in the degree of continentality and moisture conditions, have specificity in the altitudinal belts and sub-belts of vegetation. Diversity within belts and sub-belts, expressed through the typological diversity of vegetation at the level of formations, classes, and groups of associations, is marked by climatic differences in bioclimatic variants of the IIIrd order. The diversity of climatic conditions that determine the phytocoenotic diversity of Northeastern Transbaikalia is characterized through integral bioclimatic types of orobiome, determined by temperature and moisture supply. Three ombroclimatic types were distinguished by continentality conditions. The influence of the complex orographic structure of a vast mountainous territory, as well as zonal and sectoral patterns in changing climatic conditions, is characterized in their change from continental to extracontinental in according to the degree of climate continentality. The same factors determine the identification of three thermoclimatic types, which are associated with the distinguished altitudinal vegetation belts (mountain tundra, subalpine, mountain taiga). The temperate cold type is expressed in the intermountain depressions and low mountains of the Patom highlands, the cold type is associated with the middle mountains and the lower part of the high mountains (mountain taiga and subalpine belts), and the extra cold type is distinguished in the high mountains of the most massive ridges – Kodar and Kalar. Conclusion. Quantitative interpretation of the climatic conditions of the bioclimatic variants of the orobiome made it possible to give an integral evaluation of the climatic conditionality of the development of basic vegetation formations, the altitudinal belt divisions, and the altitudinal spectra of vegetation in general. The resulting basis can be used for the sustainable development of the region in connection with economic activities in areas adjacent to the Baikal-Amur Railway, for monitoring and forecasting changes in vegetation and ecosystems in general due to climate change and intensification of economic activities in the region.