The ecological significance of thickness changes in stem, branches and twigs of Pinus cembra L. during winter : 3rd EUROSILVA Workshop, Obergurgl, Austria, September, 10-14, 1998
During winter various types of thickness changes in the cortex of twigs, branches and the stem of cembran pine (Pinus cembra L.) were established, caused by direct and indirect effects of frost. Direct effects of freezing are the shrinking of the living cortex and its expansion during the following thaw. The mechanism behind this is the transfer of water from the cells into the intercellular space during ice formation, which is accompanied by a loss of cell volume, and the resorption of water by the cells during a thaw. Thickness changes caused indirectly by frost are due to dehydration and hydration of the cortex tissue. As long as the soil was frozen cumulative dehydration of the cortex resulted in considerable shrinking, which was stronger in the stem than in branches and twigs. After soil water was available again, cortex tissues re-expanded and indicated water resaturation of the tree. We conclude that thickness changes measurd with dendrometers are a suitable indicator for water relations of trees during winter.
