Clustering of siberian cedar pine habitats on the slopes of the borus ridge of the Western Sayan

The formation of the timberline in the mountains is a complex process that depends on many simultaneously acting factors. Climatic factors are usually considered as priorities, for example, low air and soil temperatures and the associated shortened growing season. However, in mountainous areas with complex dissected relief, often not climatogenic, but landscape-like forest boundaries are formed, or mixed. A transect was laid on the territory of the Mountain Forestry of the Shushensky Bor National Park, including three test areas located at an altitude of 1347 to 1411 m above sea level, both in typical forest phytocenoses with a predominance of Siberian cedar pine (Pinus sibirica Du Tour) and at the upper limit of its distribution. The study revealed that during the formation of the timberline of the Pinus sibirica cedar advance on the slopes of the Borus Ridge, climatic factors and terrain features have a significant impact. Among the limiting factors, one can note not only a decrease in temperature as the altitude increases above sea level, but also a water shortage associated with a significant steepness of the slopes, which leads to an increase in surface runoff, and low-power soils are not able to retain enough moisture. Siberian pine trees growing in such conditions have a decrease in the length and weight of needles, and a decrease in the size of stomata is observed as a compensatory mechanism. Large stomata can increase water loss, while small stomata help reduce water loss, which is an important adaptation of plants for survival.

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