Co-Authors:
Schiller, G., Department of Agronomy and Natural Resources, Agricultural Research Organization, the Volcani Center, P.O. Box 6, 50250 Bet Dagan, Israel
Cohen, S., Department of Environmental Physics and Irrigation, Agricultural Research Organization, the Volcani Center, P.O. Box 6, 50250 Bet Dagan, Israel
Ungar, E.D., Department of Agronomy and Natural Resources, Agricultural Research Organization, the Volcani Center, P.O. Box 6, 50250 Bet Dagan, Israel
Moshe, Y., Department of Agronomy and Natural Resources, Agricultural Research Organization, the Volcani Center, P.O. Box 6, 50250 Bet Dagan, Israel
Herr, N., Faculty of Agriculture, the Hebrew University of Jerusalem, P.O. Box 12, Rehovot, Israel
Abstract:
The annual course of daily transpiration and the hydrological balance of a Tabor oak forest were determined. The study was done in a representative forest within the natural geographical range of the species in the lower Galilee region of Israel. The climate is sub-humid with a rainless dry season from May to October. A partial water balance of a 0.1 ha area supporting an average of 14 trees was calculated from: (a) soil water content (SWC) measured by a Neutron Probe at depths of from 0.2 to 8 m, and (b) daylight transpiration rate measured with sap flow sensors by the heat pulse technique. Soil-bedrock complex water content (%) in the first 2 m of the profile fluctuated strongly between 5 and 20% depending on the season. The water content increased with depth from about 10% at 2.0 m depth to more than 20% at 5.0 m depth. For depths exceeding 5.5 m seasonal fluctuations in water content were negligible and water content ranged from 30 to 35%. After a dry winter, water content generally decreased within the main root zone down to about 2.0 m depth. Monthly changes in water content (mm) were greatest at depths of 0.35-1.0 m. Only minor changes in the soil-bedrock complex water content were recorded at greater depths. After a very rainy winter (2002/2003), decreases in soil-bedrock complex water content in the upper 2 m were much larger than after a dry winter. Fluctuations of soil-bedrock complex water content in deeper regions were larger in the wetter year, probably the result of drainage. Sap velocity was measured at six depths in the sapwood, from 4 to 44 mm, at 8 mm intervals. Sap velocity declined with depth, hence, sap flux density too. Based on sap velocity measurements performed during 4 years, the annual average daily transpiration (T) was 0.796 mm/day. This sums up to 239 mm during ∼300 days of leaf carriage, i.e. 41.3% of the 578 mm average annual rainfall for the area in the last 50 years. In a relatively dry year (rainfall of 432.7 mm) total water withdrawal from the 8 m soil-bedrock profile was 81% of the annual rainfall; of this amount 69% were transpired by the oak trees (239.0 mm), or 55% of the annual rainfall. In a relatively wet year (annual rainfall 801.4 mm) total water withdrawal was 67%; of this amount 45% would be transpired by the oak trees, or 30% of the annual rainfall. © 2006 Elsevier B.V. All rights reserved.
תפריט נגישות
ניגודיות עדינה
מונוכרום
הדגשת קישורים
חסימת אנימציה
פונט קריא
סגור
איפוס הגדרות נגישות
להורדת מודול נגישות חינם
