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

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http://hdl.handle.net/10138/318245

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Räsänen , M , Merbold , L , Vakkari , V , Aurela , M , Laakso , L , Beukes , J P , Zyl , P G V , Josipovic , M , Feig , G , Pellikka , P , Rinne , J & Katul , G 2020 , ' Root-zone soil moisture variability across African savannas : From pulsed rainfall to land‐cover switches ' , Ecohydrology , vol. 13 , no. 5 , 2213 . https://doi.org/10.1002/eco.2213

Title: Root-zone soil moisture variability across African savannas : From pulsed rainfall to land‐cover switches
Author: Räsänen, Matti; Merbold, Lutz; Vakkari, Ville; Aurela, Mika; Laakso, Lauri; Beukes, Johan P.; Zyl, Pieter G. Van; Josipovic, Miroslav; Feig, Gregor; Pellikka, Petri; Rinne, Janne; Katul, Gabriel
Contributor: University of Helsinki, INAR Physics
University of Helsinki, Finnish Meteorological Institute
University of Helsinki, INAR Physics
University of Helsinki, Department of Geosciences and Geography
University of Helsinki, Lund University
University of Helsinki, Duke University
Date: 2020-07
Language: eng
Number of pages: 20
Belongs to series: Ecohydrology
ISSN: 1936-0584
URI: http://hdl.handle.net/10138/318245
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) 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 similar to 1.0. This relation and the variability of length and timing of dry periods are also discussed.
Subject: 1181 Ecology, evolutionary biology
1171 Geosciences
memory
persistence
precipitation intensity
savanna
WATER-CONTROLLED ECOSYSTEMS
VOLATILE ORGANIC-COMPOUNDS
HYDROLOGIC PROCESSES
ACTIVE-ROLE
CLIMATE
BALANCE
MODEL
STRESS
PLANTS
DISTRIBUTIONS
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