Differentiation of climatic ecotypes in Siberian dwarf pine (Pinus pumila (Pall.) Regel): in situ research experience

In the boreal zone, few forest-forming conifers have huge ranges within which the species are differentiated into climatic ecotypes. This phenomenon has been well studied using the example of upright species. Their geographical and climatic range is several times smaller than that of the Siberian dwarf pine. However, large differences in productivity and stability of contrasting climatic ecotypes were found in all species when they were cultivated under the same conditions. In this work, the ecotypes of the Siberian dwarf pine were studied at experimental sites outside its natural range in the southern part of Western Siberia where the sum of active temperatures was 1850°C. In the main experiment, four ecotypes represented the longitude transect from the Northern Baikal Region to the Southern Kuriles (where the sum of temperatures varies from 800 to 1800 degrees, respectively) (See Table 1). The indicators of total productivity (trunk diameter, crown volume) increased slightly from the Siberian ecotypes to the Far Eastern ones, i.e. from the most continental to the most oceanic ecotype (See Table 2). The most significant differences were in two characteristics important for the breeding of ornamental cultivars: the shape of the crown and the color of the needles. The Siberian ecotypes had a narrow crown and a bluish color of needles. The Far Eastern ecotypes, especially from the South Kuril, had a wide crown and bright blue needles (See Fig. 1). Thus, despite the huge variety of climatic conditions within the range, the basic differences in growth rate between Siberian dwarf pine ecotypes are much smaller than in other boreal conifer species. Outside the tropical zone, winter conditions are the main climatic factor for trees. Pinus pumila is a chionophilic species which always winters under snow cover. The "undersnow" climate is about the same in different regions. Apparently, this is the main reason for the small basic differences between ecotypes in terms of growth rate and living status. The main experiment was conducted in a place relatively protected from spring frosts. There were also no significant sources of pest (wooly aphid, Pineus cembrae) in this place. In other experiment where external destructive factors acted in full force the differences between the ecotypes were much greater (See Table 2). The South Kuril ecotype surpassed the Siberian one by 2 times in height, 4 times in crown diameter, and 22 times in crown volume! Such huge differences in productivity were explained almost exclusively by different resistance to external factors. The South Kuril ecotype was completely uninhabited by wooly aphid, it rarely and slightly damaged by spring frosts. The Siberian ecotype was regularly and seriously damaged by these factors. Thus, the higher the sum of the active temperatures in the places of origin of the ecotypes, the higher their stability and productivity at the test site. The differences were small in the absence of secondary negative factors but they increased sharply under the influence of spring frosts and pests. P. pumila is a unique species in terms of originality and decorativeness. Our results clearly indicate its prospects in Southern Siberia. Paradoxically, the Far Eastern ecotypes are more relevant for this region than the Siberian ones. They are perfectly resistant and decorative regardless of the growing conditions. The South Kuril ecotype occupies a special place as the most stable and the most decorative. The article contains 2 Figures, 5 Tables and 49 References. The Author declares no conflict of interest.

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