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University of Arizona (1983)

SAPWOOD WATER STORAGE IN THE STEMS OF PONDEROSA PINE

Hsieh, Sheau-Ling

Titre : SAPWOOD WATER STORAGE IN THE STEMS OF PONDEROSA PINE

Auteur : Hsieh, Sheau-Ling.

Université de soutenance : University of Arizona

Grade : Master of Science (MS) 1983

Résumé
The sapwood relative water content, Rs, and stem radii changes in ponderosa pine were examined during the April-July period in 1979. Sapwood water deficits (100 — Rs)% in ponderosa pine never exceeded 20%. In addition, stem radii changes increased throughout the growing season and were greatly influenced by temperature, relative humidity, rainfall, and cloud cover. The dependence of stem radii change upon Rs and water potential was not statistically significant, however. Direct measurement of water drawn from extensible tissues V * 3 0.1 m /ha day appear to underestimate the volume of water withdrawn from the stem, as the observed changes in Rs clearly demonstrate that some water leaves the sapwood storage. On the other hand, direct measurement of relative water content change, 1.2 m /ha day, appears to overestimate the amount of water withdrawn. The problem lies in identifying the volume of the sapwood that is active in the exchange process. Definition of this active volume is a problem that remains unsolved

Mots clés : Ponderosa pine — Water requirements. ; Plant-water relationships.

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