Abstract
The effects of climatic factors and vegetation type on
evapotranspiration (E) and water use efficiency (WUE) were analyzed
using tower-based eddy-covariance (EC) data of eleven African sites (22
site years) located across a continental-scale transect. The seasonal
pattern of E was closely linked to growing-season length and rainfall
distribution. Although annual precipitation (P) was highly variable
among sites (290 to 1650 mm), minimum annual E was not less than 250 mm
and reached a maximum of 900 mm where annual P exceeded 1200 mm.
Site-specific interannual variability in E could be explained by either
changes in total P or variations in solar irradiance. At some sites, a
highly positive linear correlation was found between monthly sums of E
and net radiation (Rn), whereas a hysteretic relationship at other sites
indicated that E lagged behind the typical seasonal progression of Rn.
Results of a cross-correlation analysis between daily (24-h) E and Rn
revealed that site-specific lag times were between 0 days and up to a
few weeks depending on the lag of vapor pressure deficit (D) behind Rn
and vegetation type. Physiological parameters (e.g. mean dry-foliage
Priestley-Taylor alpha) implied that stomatal limitation to
transpiration prevailed. During the rainy season, a strong linear
correlation between monthly mean values of gross primary production
(GPP) and E resulted in water use efficiency being constant with lower
values at grass-dominated sites (~2 to ~3.5 g C kg-1 H2O) than at
natural woodland sites and plantations (~4.5 to ~6 g C kg-1 H2O).
Original language | English |
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Publication status | Published - 2013 |
Event | EGU General Assembly 2013 - Vienna, Austria Duration: 7 Apr 2013 → 12 Apr 2013 |
Conference
Conference | EGU General Assembly 2013 |
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Country | Austria |
City | Vienna |
Period | 7/04/13 → 12/04/13 |