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| Titel |
The impact of broadleaved woodland on water resources in lowland UK: II. Evaporation estimates from sensible heat flux measurements over beech woodland and grass on chalk sites in Hampshire |
| VerfasserIn |
J. Roberts, P. Rosier, D. M. Smith |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 9, no. 6 ; Nr. 9, no. 6 (2005-12-31), S.607-613 |
| Datensatznummer |
250007141
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| Publikation (Nr.) |
 copernicus.org/hess-9-607-2005.pdf |
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| Zusammenfassung |
| The impact on recharge to the Chalk aquifer of substitution of broadleaved
woodland for pasture is a matter of concern in the UK. Hence, measurements of
energy balance components were made above beech woodland and above pasture,
both growing on shallow soils over chalk in Hampshire. Latent heat flux
(evaporation) was calculated as the residual from these measurements of
energy balances in which sensible heat flux was measured with an eddy
correlation instrument that determined fast response vertical wind speeds and
associated temperature changes. Assessment of wind turbulence statistics
confirmed that the eddy correlation device performed satisfactorily in both
wet and dry conditions. There was excellent agreement between forest
transpiration measurements made by eddy correlation and stand level tree
transpiration measured with sap flow devices. Over the period of the
measurements, from March 1999 to late summer 2000, changes in soil water
content were small and grassland evaporation and transpiration estimated from
energy balance-eddy flux measurements were in excellent agreement with Penman
estimates of potential evaporation. Over the 18-month measurement period, the
cumulative difference between broadleaved woodland and grassland was small
but evaporation from the grassland was 3% higher than that from the
woodland. In the springs of 1999 and 2000, evaporation from the grassland was
greater than that from the woodland. However, following leaf emergence in the
woodland, the difference in cumulative evaporation diminished until the
following spring. |
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