Precipitation–fire functional interactions control biomass stocks and carbon exchanges across the world's largest savanna
<p>Southern African woodlands (SAW) are the world's largest savanna, covering <span class="inline-formula">∼</span> 3 M km<span class="inline-formula"><sup>2</sup></span>, but their carbon balance and its interactions with climate an...
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Copernicus Publications
2025-03-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/22/1597/2025/bg-22-1597-2025.pdf |
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| author | M. Williams M. Williams D. T. Milodowski D. T. Milodowski T. L. Smallman T. L. Smallman K. G. Dexter G. C. Hegerl I. M. McNicol M. O'Sullivan C. M. Roesch C. M. Ryan C. M. Ryan S. Sitch A. Valade |
| author_facet | M. Williams M. Williams D. T. Milodowski D. T. Milodowski T. L. Smallman T. L. Smallman K. G. Dexter G. C. Hegerl I. M. McNicol M. O'Sullivan C. M. Roesch C. M. Ryan C. M. Ryan S. Sitch A. Valade |
| author_sort | M. Williams |
| collection | DOAJ |
| description | <p>Southern African woodlands (SAW) are the world's largest savanna, covering <span class="inline-formula">∼</span> 3 M km<span class="inline-formula"><sup>2</sup></span>, but their carbon balance and its interactions with climate and disturbance are poorly understood. Here we address three issues that hinder regional efforts to address international climate agreements: producing a state-of-the-art C budget of the SAW region; diagnosing C cycle functional variation and interactions with climate and fire across SAW; and evaluating SAW C cycle representation in land surface models (LSMs). Using 1506 independent 0.5° pixel model calibrations, each constrained with local Earth observation time series of woody carbon stocks (C<span class="inline-formula"><sub>wood</sub></span>) and leaf area, we produce a regional SAW C analysis (2006–2017). The regional net biome production is neutral, i.e. <span class="inline-formula">−</span>0.08 Mg C ha<span class="inline-formula"><sup>−1</sup></span> yr<span class="inline-formula"><sup>−1</sup></span> (95 % uncertainty interval <span class="inline-formula">−</span>1.67/1.66), with fire emissions contributing <span class="inline-formula">∼</span> 0.88 Mg C ha<span class="inline-formula"><sup>−1</sup></span> yr<span class="inline-formula"><sup>−1</sup></span> (95 % uncertainty interval 0.36–2.51). Fire-related mortality driving fluxes from the total C<span class="inline-formula"><sub>wood</sub></span> to dead organic matter likely exceeds both fire-related emissions from C<span class="inline-formula"><sub>wood</sub></span> into the atmosphere and non-fire C<span class="inline-formula"><sub>wood</sub></span> mortality. The emergent spatial variation in biogenic fluxes and C pools is strongly correlated with mean annual precipitation and burned area. However, there are multiple, potentially confounding, causal pathways through which variation in environmental drivers impacts the spatial distribution of C stocks and fluxes, which is mediated by spatial variations in functional parameters like allocation, wood lifespan, and fire resilience. More C<span class="inline-formula"><sub>wood</sub></span> in wetter areas is caused by positive precipitation effects on net primary production and on parameters for wood lifespan but is damped by a negative effect with rising precipitation increasing fire-related mortality. Compared to this analysis, LSMs showed marked differences in spatial distributions and magnitudes of C stocks and fire emissions. The current generation of LSMs represents savanna as a single plant functional type, missing important spatial functional variations identified here. Patterns of biomass and C cycling across the region are the outcome of climate controls on production and vegetation–fire interactions which determine residence times, which is linked to spatial variations in key ecosystem functional characteristics.</p> |
| format | Article |
| id | doaj-art-90d174bb24944827b534080397f1e140 |
| institution | OA Journals |
| issn | 1726-4170 1726-4189 |
| language | English |
| publishDate | 2025-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj-art-90d174bb24944827b534080397f1e1402025-08-20T02:10:38ZengCopernicus PublicationsBiogeosciences1726-41701726-41892025-03-01221597161410.5194/bg-22-1597-2025Precipitation–fire functional interactions control biomass stocks and carbon exchanges across the world's largest savannaM. Williams0M. Williams1D. T. Milodowski2D. T. Milodowski3T. L. Smallman4T. L. Smallman5K. G. Dexter6G. C. Hegerl7I. M. McNicol8M. O'Sullivan9C. M. Roesch10C. M. Ryan11C. M. Ryan12S. Sitch13A. Valade14School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3FF, UKNational Centre for Earth Observation, University of Edinburgh, Edinburgh, EH9 3FF, UKSchool of GeoSciences, University of Edinburgh, Edinburgh, EH9 3FF, UKNational Centre for Earth Observation, University of Edinburgh, Edinburgh, EH9 3FF, UKSchool of GeoSciences, University of Edinburgh, Edinburgh, EH9 3FF, UKNational Centre for Earth Observation, University of Edinburgh, Edinburgh, EH9 3FF, UKSchool of GeoSciences, University of Edinburgh, Edinburgh, EH9 3FF, UKSchool of GeoSciences, University of Edinburgh, Edinburgh, EH9 3FF, UKSchool of GeoSciences, University of Edinburgh, Edinburgh, EH9 3FF, UKFaculty of Environment, Science and Economy, University of Exeter, Exeter, EX4 4QF, UKSchool of GeoSciences, University of Edinburgh, Edinburgh, EH9 3FF, UKSchool of GeoSciences, University of Edinburgh, Edinburgh, EH9 3FF, UKNational Centre for Earth Observation, University of Edinburgh, Edinburgh, EH9 3FF, UKFaculty of Environment, Science and Economy, University of Exeter, Exeter, EX4 4QF, UKUMR Ecologie Fonctionnelle et Biogéochimie des Sols et Agroécosystèmes, 34090 Montpellier, France<p>Southern African woodlands (SAW) are the world's largest savanna, covering <span class="inline-formula">∼</span> 3 M km<span class="inline-formula"><sup>2</sup></span>, but their carbon balance and its interactions with climate and disturbance are poorly understood. Here we address three issues that hinder regional efforts to address international climate agreements: producing a state-of-the-art C budget of the SAW region; diagnosing C cycle functional variation and interactions with climate and fire across SAW; and evaluating SAW C cycle representation in land surface models (LSMs). Using 1506 independent 0.5° pixel model calibrations, each constrained with local Earth observation time series of woody carbon stocks (C<span class="inline-formula"><sub>wood</sub></span>) and leaf area, we produce a regional SAW C analysis (2006–2017). The regional net biome production is neutral, i.e. <span class="inline-formula">−</span>0.08 Mg C ha<span class="inline-formula"><sup>−1</sup></span> yr<span class="inline-formula"><sup>−1</sup></span> (95 % uncertainty interval <span class="inline-formula">−</span>1.67/1.66), with fire emissions contributing <span class="inline-formula">∼</span> 0.88 Mg C ha<span class="inline-formula"><sup>−1</sup></span> yr<span class="inline-formula"><sup>−1</sup></span> (95 % uncertainty interval 0.36–2.51). Fire-related mortality driving fluxes from the total C<span class="inline-formula"><sub>wood</sub></span> to dead organic matter likely exceeds both fire-related emissions from C<span class="inline-formula"><sub>wood</sub></span> into the atmosphere and non-fire C<span class="inline-formula"><sub>wood</sub></span> mortality. The emergent spatial variation in biogenic fluxes and C pools is strongly correlated with mean annual precipitation and burned area. However, there are multiple, potentially confounding, causal pathways through which variation in environmental drivers impacts the spatial distribution of C stocks and fluxes, which is mediated by spatial variations in functional parameters like allocation, wood lifespan, and fire resilience. More C<span class="inline-formula"><sub>wood</sub></span> in wetter areas is caused by positive precipitation effects on net primary production and on parameters for wood lifespan but is damped by a negative effect with rising precipitation increasing fire-related mortality. Compared to this analysis, LSMs showed marked differences in spatial distributions and magnitudes of C stocks and fire emissions. The current generation of LSMs represents savanna as a single plant functional type, missing important spatial functional variations identified here. Patterns of biomass and C cycling across the region are the outcome of climate controls on production and vegetation–fire interactions which determine residence times, which is linked to spatial variations in key ecosystem functional characteristics.</p>https://bg.copernicus.org/articles/22/1597/2025/bg-22-1597-2025.pdf |
| spellingShingle | M. Williams M. Williams D. T. Milodowski D. T. Milodowski T. L. Smallman T. L. Smallman K. G. Dexter G. C. Hegerl I. M. McNicol M. O'Sullivan C. M. Roesch C. M. Ryan C. M. Ryan S. Sitch A. Valade Precipitation–fire functional interactions control biomass stocks and carbon exchanges across the world's largest savanna Biogeosciences |
| title | Precipitation–fire functional interactions control biomass stocks and carbon exchanges across the world's largest savanna |
| title_full | Precipitation–fire functional interactions control biomass stocks and carbon exchanges across the world's largest savanna |
| title_fullStr | Precipitation–fire functional interactions control biomass stocks and carbon exchanges across the world's largest savanna |
| title_full_unstemmed | Precipitation–fire functional interactions control biomass stocks and carbon exchanges across the world's largest savanna |
| title_short | Precipitation–fire functional interactions control biomass stocks and carbon exchanges across the world's largest savanna |
| title_sort | precipitation fire functional interactions control biomass stocks and carbon exchanges across the world s largest savanna |
| url | https://bg.copernicus.org/articles/22/1597/2025/bg-22-1597-2025.pdf |
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