The Tree Growth and Water Relation of Boreal Forest

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The Tree Growth and Water Relation in Boreal ForestThe tree growth and water relation in boreal forests were investigated. Strain gages were glued in the tangential direction of the surface of the inner bark of several trees. Diurnal change in the tangential strain were measured throughout the seasons.1) In winter in the boreal forests, the water in the tranks of trees frozen into ice. The diurnal change of the strain during this period coinsided with the shrinkage and swelling of the ice following the change of air temperature under zero degrees centigrate. The movement was the largest in a yaer.2) In early spring, shirakamba birch exudated sap through a hole drilled on the trank. Sap exudation continued for one month and stopped just on time when flowers and leaves opened. The diurnal change of the strain was the lowest in the year. Trees seemed to keep a positive pressure throughout this period for sending the sap up to the buds of flowers and leaves for their growth and opening.3) … More In spring and summer after the leaf opening, tree growed. The diurnal change of the strain in this period varied inversely with the change observed in the winter season. Namely, the trank started to shrink when air temperature started to rise after sun rise and shrinked continuously till noon and released the shrinkage when air temperature started to fall down toward evening. During night the shrinkage was revovered and swelled a little more than the starting point of the day before. The change seemed to coinside with the balance of the activities between transpiration of the leaves and water absorption from the roots. The changes were higher in sunny days because of higher transpiration and photosynthesis activities and were lower in rainy days with their lower activities.4) The growth curve of the trank was drawn as an integration of the difference between the shrinkage and the release of the shrinkage and following swelling. A maximum of the growth rate was observed on the end of July and the rate decreased gradually toward defoliation. Less