Impacts of Precipitation Variability on Carbon Flux Dynamics of Global Semi-Arid Savannas
Nadolski, Laura ; Wesselkamp, Marieke ; El-Madany, Tarek ; Lange, Markus ; Nelson, Jacob ; Carrara, Arnaud ; Wieckowski, Aleksander LU
; Hildebrandt, Anke
; Reichstein, Markus
and Lee, Sung Ching
(2026)
In Global Change Biology
32(6).
- Abstract
With global warming, precipitation variability is increasing, affecting water availability and consequently ecosystem functioning and carbon uptake. Semi-arid ecosystems are very sensitive to changes in water availability since both gross primary productivity (GPP) and ecosystem respiration (Reco) are strongly linked to it, contributing most to the interannual variability and trend of the global land carbon sink. However, their carbon-dioxide (CO2) flux dynamics and specifically Reco are not well understood and poorly represented in models. Here we compiled a long-term global dataset of eight eddy-covariance sites located in semi-arid savannas to analyze the effects of precipitation variability on their... (More)
With global warming, precipitation variability is increasing, affecting water availability and consequently ecosystem functioning and carbon uptake. Semi-arid ecosystems are very sensitive to changes in water availability since both gross primary productivity (GPP) and ecosystem respiration (Reco) are strongly linked to it, contributing most to the interannual variability and trend of the global land carbon sink. However, their carbon-dioxide (CO2) flux dynamics and specifically Reco are not well understood and poorly represented in models. Here we compiled a long-term global dataset of eight eddy-covariance sites located in semi-arid savannas to analyze the effects of precipitation variability on their net ecosystem exchange (NEE, with NEE = Reco—GPP). We assessed the effects of precipitation variability, represented by precipitation amount, frequency, intensity, and dry spell length, on both annual and seasonal CO2 fluxes. We used linear mixed effect models to identify relationships between the precipitation metrics, environmental factors, and CO2 fluxes. We further employed structural equation models to identify direct and indirect effects of precipitation variability on ecosystem CO2 fluxes in different phenological seasons. The results indicate that precipitation amount and intensity mostly lead to increasing GPP and Reco on the annual scale, with different net effects on NEE depending on the sites. On the seasonal scale, both precipitation frequency and intensity explained more NEE variations than precipitation amount only, while the contribution of dry spell length was negligible. The three precipitation metrics together lead to highest model improvement. Across seasons, soil water content was the main mediator of precipitation impacts on CO2 fluxes, with air temperatures co-dominating in the drydown season. Overall, this study shows that precipitation intensity, frequency, and their seasonal timing are crucial for explaining ecosystem CO2 flux dynamics of semi-arid savannas. This can help improve predictions of the effects of increasing precipitation variability on the global carbon cycle.
(Less)
- author
- Nadolski, Laura
; Wesselkamp, Marieke
; El-Madany, Tarek
; Lange, Markus
; Nelson, Jacob
; Carrara, Arnaud
; Wieckowski, Aleksander
LU
; Hildebrandt, Anke
; Reichstein, Markus
and Lee, Sung Ching
- organization
- publishing date
- 2026-06
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- carbon cycle, drylands, ecohydrology, eddy covariance, land carbon sink, precipitation variability
- in
- Global Change Biology
- volume
- 32
- issue
- 6
- article number
- e70954
- publisher
- Wiley-Blackwell
- external identifiers
-
- scopus:105041986487
- pmid:42299680
- ISSN
- 1354-1013
- DOI
- 10.1111/gcb.70954
- language
- English
- LU publication?
- yes
- id
- 07c2b954-b999-4864-a31c-4874941854ad
- date added to LUP
- 2026-08-21 15:22:23
- date last changed
- 2026-09-18 17:06:16
@article{07c2b954-b999-4864-a31c-4874941854ad,
abstract = {{<p>With global warming, precipitation variability is increasing, affecting water availability and consequently ecosystem functioning and carbon uptake. Semi-arid ecosystems are very sensitive to changes in water availability since both gross primary productivity (GPP) and ecosystem respiration (R<sub>eco</sub>) are strongly linked to it, contributing most to the interannual variability and trend of the global land carbon sink. However, their carbon-dioxide (CO<sub>2</sub>) flux dynamics and specifically R<sub>eco</sub> are not well understood and poorly represented in models. Here we compiled a long-term global dataset of eight eddy-covariance sites located in semi-arid savannas to analyze the effects of precipitation variability on their net ecosystem exchange (NEE, with NEE = R<sub>eco</sub>—GPP). We assessed the effects of precipitation variability, represented by precipitation amount, frequency, intensity, and dry spell length, on both annual and seasonal CO<sub>2</sub> fluxes. We used linear mixed effect models to identify relationships between the precipitation metrics, environmental factors, and CO<sub>2</sub> fluxes. We further employed structural equation models to identify direct and indirect effects of precipitation variability on ecosystem CO<sub>2</sub> fluxes in different phenological seasons. The results indicate that precipitation amount and intensity mostly lead to increasing GPP and R<sub>eco</sub> on the annual scale, with different net effects on NEE depending on the sites. On the seasonal scale, both precipitation frequency and intensity explained more NEE variations than precipitation amount only, while the contribution of dry spell length was negligible. The three precipitation metrics together lead to highest model improvement. Across seasons, soil water content was the main mediator of precipitation impacts on CO<sub>2</sub> fluxes, with air temperatures co-dominating in the drydown season. Overall, this study shows that precipitation intensity, frequency, and their seasonal timing are crucial for explaining ecosystem CO<sub>2</sub> flux dynamics of semi-arid savannas. This can help improve predictions of the effects of increasing precipitation variability on the global carbon cycle.</p>}},
author = {{Nadolski, Laura and Wesselkamp, Marieke and El-Madany, Tarek and Lange, Markus and Nelson, Jacob and Carrara, Arnaud and Wieckowski, Aleksander and Hildebrandt, Anke and Reichstein, Markus and Lee, Sung Ching}},
issn = {{1354-1013}},
keywords = {{carbon cycle; drylands; ecohydrology; eddy covariance; land carbon sink; precipitation variability}},
language = {{eng}},
number = {{6}},
publisher = {{Wiley-Blackwell}},
series = {{Global Change Biology}},
title = {{Impacts of Precipitation Variability on Carbon Flux Dynamics of Global Semi-Arid Savannas}},
url = {{http://dx.doi.org/10.1111/gcb.70954}},
doi = {{10.1111/gcb.70954}},
volume = {{32}},
year = {{2026}},
}