Biophysical controls on evapotranspiration and water use efficiency in natural, semi-natural and managed African ecosystems

C. Brümmer, L. Merbold, S. Archibald, J. Ardö, A. Arneth, E.M. Veenendaal

Research output: Contribution to conferenceConference paperAcademic

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 languageEnglish
Publication statusPublished - 2013
EventEGU General Assembly 2013 - Vienna, Austria
Duration: 7 Apr 201312 Apr 2013

Conference

ConferenceEGU General Assembly 2013
CountryAustria
CityVienna
Period7/04/1312/04/13

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water use efficiency
evapotranspiration
vegetation type
ecosystem
net radiation
eddy covariance
vapor pressure
transpiration
foliage
irradiance
primary production
woodland
plantation
growing season
transect
grass
rainfall
radiation

Cite this

Brümmer, C., Merbold, L., Archibald, S., Ardö, J., Arneth, A., & Veenendaal, E. M. (2013). Biophysical controls on evapotranspiration and water use efficiency in natural, semi-natural and managed African ecosystems. Paper presented at EGU General Assembly 2013, Vienna, Austria.
Brümmer, C. ; Merbold, L. ; Archibald, S. ; Ardö, J. ; Arneth, A. ; Veenendaal, E.M. / Biophysical controls on evapotranspiration and water use efficiency in natural, semi-natural and managed African ecosystems. Paper presented at EGU General Assembly 2013, Vienna, Austria.
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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).",
author = "C. Br{\"u}mmer and L. Merbold and S. Archibald and J. Ard{\"o} and A. Arneth and E.M. Veenendaal",
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year = "2013",
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Brümmer, C, Merbold, L, Archibald, S, Ardö, J, Arneth, A & Veenendaal, EM 2013, 'Biophysical controls on evapotranspiration and water use efficiency in natural, semi-natural and managed African ecosystems' Paper presented at EGU General Assembly 2013, Vienna, Austria, 7/04/13 - 12/04/13, .

Biophysical controls on evapotranspiration and water use efficiency in natural, semi-natural and managed African ecosystems. / Brümmer, C.; Merbold, L.; Archibald, S.; Ardö, J.; Arneth, A.; Veenendaal, E.M.

2013. Paper presented at EGU General Assembly 2013, Vienna, Austria.

Research output: Contribution to conferenceConference paperAcademic

TY - CONF

T1 - Biophysical controls on evapotranspiration and water use efficiency in natural, semi-natural and managed African ecosystems

AU - Brümmer, C.

AU - Merbold, L.

AU - Archibald, S.

AU - Ardö, J.

AU - Arneth, A.

AU - Veenendaal, E.M.

N1 - id. EGU2013-8102

PY - 2013

Y1 - 2013

N2 - 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).

AB - 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).

M3 - Conference paper

ER -

Brümmer C, Merbold L, Archibald S, Ardö J, Arneth A, Veenendaal EM. Biophysical controls on evapotranspiration and water use efficiency in natural, semi-natural and managed African ecosystems. 2013. Paper presented at EGU General Assembly 2013, Vienna, Austria.