Morphogenesis of Upright and Prostrate Growth forms of Pinus sibirica Du Tour (Pinaceae) at the Intrazonal Distribution Limits

A comparative analysis of the crown morphogenesis of upright and prostrate growth forms of Siberian stone pine inhabited on intrazonal distribution limits associated with temperature (the upper limit in the mountains) and soil moisture (forest-bog ecotones) was carried out. Case study of the ecotone “subalpine forest – mountain tundra” in the Central Altai showed that high winds with thin snow cover contribute to formation of the low-growing multi-stemed trees. Increase of thickness of the snow cover and decrease of the wind speed lead to formation of the combined crown consisting of nival prostrate and vertical parts producing a typical type of tree form. The crown morphogenesis in upland swamp area (southern West Siberian taiga subzone) is due to the specific microrelief of peat hillock formed by several species of Sphagnum mosses differing in morphology and growth rate. Trees growing in the central part of peat hillock, where slow-growing S. fuscum dominated, had upright growth form. Trees growing in the peripheral part of the peat hillock, where fast-growing S. magellanicum dominated, had prostrate growth form. It was shown that ability to form multilevel adventitious root system plays a determinant role in surviving of Siberian stone pine in upland swamp areas