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Root-zone soil moisture variability across African savannas : From pulsed rainfall to land-cover switches

Räsänen, Matti ; Merbold, Lutz ; Vakkari, Ville ; Aurela, Mika ; Laakso, Lauri ; Beukes, J. Paul ; Van Zyl, Pieter G. ; Josipovic, Miroslav ; Feig, Gregor and Pellikka, Petri , et al. (2020) In Ecohydrology 13(5).
Abstract

The main source of soil moisture variability in savanna ecosystems is pulsed rainfall. Rainfall pulsing impacts water-stress durations, soil moisture switching between wet-to-dry and dry-to-wet states, and soil moisture spectra as well as derived measures from it such as soil moisture memory. Rainfall pulsing is also responsible for rapid changes in grassland leaf area and concomitant changes in evapotranspirational (ET) losses, which then impact soil moisture variability. With the use of a hierarchy of models and soil moisture measurements, temporal variability in root-zone soil moisture and water-stress periods are analysed at four African sites ranging from grass to miombo savannas. The normalized difference vegetation index (NDVI)... (More)

The main source of soil moisture variability in savanna ecosystems is pulsed rainfall. Rainfall pulsing impacts water-stress durations, soil moisture switching between wet-to-dry and dry-to-wet states, and soil moisture spectra as well as derived measures from it such as soil moisture memory. Rainfall pulsing is also responsible for rapid changes in grassland leaf area and concomitant changes in evapotranspirational (ET) losses, which then impact soil moisture variability. With the use of a hierarchy of models and soil moisture measurements, temporal variability in root-zone soil moisture and water-stress periods are analysed at four African sites ranging from grass to miombo savannas. The normalized difference vegetation index (NDVI) and potential ET (PET)-adjusted ET model predict memory timescale and dry persistence in agreement with measurements. The model comparisons demonstrate that dry persistence and mean annual dry periods must account for seasonal and interannual changes in maximum ET represented by NDVI and to a lesser extent PET. Interestingly, the precipitation intensity and soil moisture memory were linearly related across three savannas with ET/infiltration ∼ 1.0. This relation and the variability of length and timing of dry periods are also discussed.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
memory, persistence, precipitation intensity, savanna
in
Ecohydrology
volume
13
issue
5
article number
e2213
publisher
John Wiley & Sons Inc.
external identifiers
  • scopus:85085945826
ISSN
1936-0584
DOI
10.1002/eco.2213
language
English
LU publication?
yes
id
f724e47e-e850-4f3d-9225-0f0c1dc6636a
date added to LUP
2020-06-29 15:46:16
date last changed
2022-04-18 23:10:02
@article{f724e47e-e850-4f3d-9225-0f0c1dc6636a,
  abstract     = {{<p>The main source of soil moisture variability in savanna ecosystems is pulsed rainfall. Rainfall pulsing impacts water-stress durations, soil moisture switching between wet-to-dry and dry-to-wet states, and soil moisture spectra as well as derived measures from it such as soil moisture memory. Rainfall pulsing is also responsible for rapid changes in grassland leaf area and concomitant changes in evapotranspirational (ET) losses, which then impact soil moisture variability. With the use of a hierarchy of models and soil moisture measurements, temporal variability in root-zone soil moisture and water-stress periods are analysed at four African sites ranging from grass to miombo savannas. The normalized difference vegetation index (NDVI) and potential ET (PET)-adjusted ET model predict memory timescale and dry persistence in agreement with measurements. The model comparisons demonstrate that dry persistence and mean annual dry periods must account for seasonal and interannual changes in maximum ET represented by NDVI and to a lesser extent PET. Interestingly, the precipitation intensity and soil moisture memory were linearly related across three savannas with ET/infiltration ∼ 1.0. This relation and the variability of length and timing of dry periods are also discussed.</p>}},
  author       = {{Räsänen, Matti and Merbold, Lutz and Vakkari, Ville and Aurela, Mika and Laakso, Lauri and Beukes, J. Paul and Van Zyl, Pieter G. and Josipovic, Miroslav and Feig, Gregor and Pellikka, Petri and Rinne, Janne and Katul, Gabriel G.}},
  issn         = {{1936-0584}},
  keywords     = {{memory; persistence; precipitation intensity; savanna}},
  language     = {{eng}},
  number       = {{5}},
  publisher    = {{John Wiley & Sons Inc.}},
  series       = {{Ecohydrology}},
  title        = {{Root-zone soil moisture variability across African savannas : From pulsed rainfall to land-cover switches}},
  url          = {{http://dx.doi.org/10.1002/eco.2213}},
  doi          = {{10.1002/eco.2213}},
  volume       = {{13}},
  year         = {{2020}},
}