The effect of rainfall amount and timing on annual transpiration in a grazed savanna grassland
(2022) In Hydrology and Earth System Sciences 26(22). p.5773-5791- Abstract
The role of precipitation (P) variability with respect to evapotranspiration (ET) and its two components, transpiration (T) and evaporation (E), from savannas continues to draw significant research interest given its relevance to a number of ecohydrological applications. Our study reports on 6 years of measured ET and estimated T and E from a grazed savanna grassland at Welgegund, South Africa. Annual P varied significantly with respect to amount (508 to 672 mm yr-1), with dry years characterized by infrequent early-season rainfall. T was determined using annual water-use efficiency and gross primary production estimates derived from eddy-covariance measurements of latent heat flux and net ecosystem CO2 exchange rates. The computed... (More)
The role of precipitation (P) variability with respect to evapotranspiration (ET) and its two components, transpiration (T) and evaporation (E), from savannas continues to draw significant research interest given its relevance to a number of ecohydrological applications. Our study reports on 6 years of measured ET and estimated T and E from a grazed savanna grassland at Welgegund, South Africa. Annual P varied significantly with respect to amount (508 to 672 mm yr-1), with dry years characterized by infrequent early-season rainfall. T was determined using annual water-use efficiency and gross primary production estimates derived from eddy-covariance measurements of latent heat flux and net ecosystem CO2 exchange rates. The computed annual T for the 4 wet years with frequent early wet-season rainfall was nearly constant, 326±19 mm yr-1 (T/ET=0.51), but was lower and more variable between the 2 dry years (255 and 154 mm yr-1, respectively). Annual T and T/ET were linearly related to the early wet-season storm frequency. The constancy of annual T during wet years is explained by the moderate water stress of C4 grasses as well as trees' ability to use water from deeper layers. During extreme drought, grasses respond to water availability with a dieback-regrowth pattern, reducing leaf area and transpiration and, thus, increasing the proportion of transpiration contributed by trees. The works suggest that the early-season P distribution explains the interannual variability in T, which should be considered when managing grazing and fodder production in these grasslands.
(Less)
- author
- organization
- publishing date
- 2022-11-16
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Hydrology and Earth System Sciences
- volume
- 26
- issue
- 22
- pages
- 19 pages
- publisher
- European Geophysical Society
- external identifiers
-
- scopus:85143398309
- ISSN
- 1027-5606
- DOI
- 10.5194/hess-26-5773-2022
- language
- English
- LU publication?
- yes
- id
- 0f2b903c-ccb6-489c-a15c-4bf5d088044d
- date added to LUP
- 2022-12-23 10:38:36
- date last changed
- 2022-12-23 10:38:36
@article{0f2b903c-ccb6-489c-a15c-4bf5d088044d,
abstract = {{<p>The role of precipitation (P) variability with respect to evapotranspiration (ET) and its two components, transpiration (T) and evaporation (E), from savannas continues to draw significant research interest given its relevance to a number of ecohydrological applications. Our study reports on 6 years of measured ET and estimated T and E from a grazed savanna grassland at Welgegund, South Africa. Annual P varied significantly with respect to amount (508 to 672 mm yr-1), with dry years characterized by infrequent early-season rainfall. T was determined using annual water-use efficiency and gross primary production estimates derived from eddy-covariance measurements of latent heat flux and net ecosystem CO2 exchange rates. The computed annual T for the 4 wet years with frequent early wet-season rainfall was nearly constant, 326±19 mm yr-1 (T/ET=0.51), but was lower and more variable between the 2 dry years (255 and 154 mm yr-1, respectively). Annual T and T/ET were linearly related to the early wet-season storm frequency. The constancy of annual T during wet years is explained by the moderate water stress of C4 grasses as well as trees' ability to use water from deeper layers. During extreme drought, grasses respond to water availability with a dieback-regrowth pattern, reducing leaf area and transpiration and, thus, increasing the proportion of transpiration contributed by trees. The works suggest that the early-season P distribution explains the interannual variability in T, which should be considered when managing grazing and fodder production in these grasslands.</p>}},
author = {{Räsänen, Matti and Aurela, Mika and Vakkari, Ville and Beukes, Johan P. and Tuovinen, Juha Pekka and Van Zyl, Pieter G. and Josipovic, Miroslav and Siebert, Stefan J. and Laurila, Tuomas and Kulmala, Markku and Laakso, Lauri and Rinne, Janne and Oren, Ram and Katul, Gabriel}},
issn = {{1027-5606}},
language = {{eng}},
month = {{11}},
number = {{22}},
pages = {{5773--5791}},
publisher = {{European Geophysical Society}},
series = {{Hydrology and Earth System Sciences}},
title = {{The effect of rainfall amount and timing on annual transpiration in a grazed savanna grassland}},
url = {{http://dx.doi.org/10.5194/hess-26-5773-2022}},
doi = {{10.5194/hess-26-5773-2022}},
volume = {{26}},
year = {{2022}},
}