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CRC PUBLICATIONS |
Soil and Litter Evaporation beneath Re-growth and Old-growth Mountain Ash Forest
David McJannet,
Rob Vertessy,
Nigel Tapper,
Sharon O' Sullivan,
Jason Berlinger,
Helen Cleugh
Publication Type:
Technical Report
This is a publication of the current CRC for Catchment Hydrology
CRC Program:
Forest Hydrology (Previous CRC)
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Publication Keywords:
Forests
Evaporation
Time Dependent
Water Balance
Eucalyptus regnans
Catchment Areas
Stream Flow
Water Yields
Lysimeters
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Abstract / Summary:
Microlysimeter and evaporation dome techniques were used to measure soil and litter evaporation (QEs) in 10 and 235 year old mountain ash forest during five 24 h measurement periods spaced through the year. From the limited measurements, QEs beneath mountain ash forest appeared to be influenced for forest age. During all but one measurement period QEs was greater in the 10 year old forest than in the 235 year old forest. The observed dissimilarity is likely to be related to forest structure which is thought to influence energy exchanges and the climate within the forest. During the warmer months QEs in both the 10 and 235 year old forest is thought to be limited by the availability of moisture, while in the cooler months abundant moisture suggests that energy availability is the limiting factor.
The accuracy of evaporation measurements made by the microlysimeter and evaporation dome techniques was determined through intercomparison with simultaneous evaporation measurements made by micrometeorological techniques. The best agreement between all techniques occurred with low net radiation conditions. This increased the confidence with which the microlysimeter and evaporation dome techniques could be used to measure QEs in mountain ash forest due to the low net radiation experienced beneath the forest canopy. Although strong agreement was found between the microlysimeter and evaporation dome measurements during comparison in an open field, such agreement was not found when measuring QEs in mountain ash forest. Possible explanations for the lack of agreement within the forest environment are given.
Combining measurements taken throughout the year, QEs beneath 10 and 235 year old mountain ash forest translated to estimated water losses of 150 and 110 mm year-1 respectively. By combining these values with transpiration and interception rates reported in the literature, QEs in 235 year old forest was estimated to account for 13% of annual evapotranspiration, while in 10 year old forest it was estimated to account for 14% of annual evapotranspiration.
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Centre Office:
CRC for Catchment Hydrology
Dept of Civil Engineering
Building 60
Monash University Vic 3800
Tel: +61 3 9905 2704
Fax: +61 3 9905 5033
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