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Determinants of woody encroachment and cover in African savannas

Savanna ecosystems are an integral part of the African landscape and sustain the livelihoods of millions of people. Woody encroachment in savannas is a widespread phenomenon but its causes are widely debated. We review the extensive literature on woody encroachment to help improve understanding of t...

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Autores principales: Devine, Aisling P., McDonald, Robbie A., Quaife, Tristan, Maclean, Ilya M. D.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Springer Berlin Heidelberg 2017
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5348564/
https://www.ncbi.nlm.nih.gov/pubmed/28116524
http://dx.doi.org/10.1007/s00442-017-3807-6
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author Devine, Aisling P.
McDonald, Robbie A.
Quaife, Tristan
Maclean, Ilya M. D.
author_facet Devine, Aisling P.
McDonald, Robbie A.
Quaife, Tristan
Maclean, Ilya M. D.
author_sort Devine, Aisling P.
collection PubMed
description Savanna ecosystems are an integral part of the African landscape and sustain the livelihoods of millions of people. Woody encroachment in savannas is a widespread phenomenon but its causes are widely debated. We review the extensive literature on woody encroachment to help improve understanding of the possible causes and to highlight where and how future scientific efforts to fully understand these causes should be focused. Rainfall is the most important determinant of maximum woody cover across Africa, but fire and herbivory interact to reduce woody cover below the maximum at many locations. We postulate that woody encroachment is most likely driven by CO(2) enrichment and propose a two-system conceptual framework, whereby mechanisms of woody encroachment differ depending on whether the savanna is a wet or dry system. In dry savannas, the increased water-use efficiency in plants relaxes precipitation-driven constraints and increases woody growth. In wet savannas, the increase of carbon allocation to tree roots results in faster recovery rates after disturbance and a greater likelihood of reaching sexual maturity. Our proposed framework can be tested using a mixture of experimental and earth observational techniques. At a local level, changes in precipitation, burning regimes or herbivory could be driving woody encroachment, but are unlikely to be the explanation of this continent-wide phenomenon. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00442-017-3807-6) contains supplementary material, which is available to authorized users.
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spelling pubmed-53485642017-03-27 Determinants of woody encroachment and cover in African savannas Devine, Aisling P. McDonald, Robbie A. Quaife, Tristan Maclean, Ilya M. D. Oecologia Concepts, Reviews and Syntheses Savanna ecosystems are an integral part of the African landscape and sustain the livelihoods of millions of people. Woody encroachment in savannas is a widespread phenomenon but its causes are widely debated. We review the extensive literature on woody encroachment to help improve understanding of the possible causes and to highlight where and how future scientific efforts to fully understand these causes should be focused. Rainfall is the most important determinant of maximum woody cover across Africa, but fire and herbivory interact to reduce woody cover below the maximum at many locations. We postulate that woody encroachment is most likely driven by CO(2) enrichment and propose a two-system conceptual framework, whereby mechanisms of woody encroachment differ depending on whether the savanna is a wet or dry system. In dry savannas, the increased water-use efficiency in plants relaxes precipitation-driven constraints and increases woody growth. In wet savannas, the increase of carbon allocation to tree roots results in faster recovery rates after disturbance and a greater likelihood of reaching sexual maturity. Our proposed framework can be tested using a mixture of experimental and earth observational techniques. At a local level, changes in precipitation, burning regimes or herbivory could be driving woody encroachment, but are unlikely to be the explanation of this continent-wide phenomenon. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00442-017-3807-6) contains supplementary material, which is available to authorized users. Springer Berlin Heidelberg 2017-01-23 2017 /pmc/articles/PMC5348564/ /pubmed/28116524 http://dx.doi.org/10.1007/s00442-017-3807-6 Text en © The Author(s) 2017 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
spellingShingle Concepts, Reviews and Syntheses
Devine, Aisling P.
McDonald, Robbie A.
Quaife, Tristan
Maclean, Ilya M. D.
Determinants of woody encroachment and cover in African savannas
title Determinants of woody encroachment and cover in African savannas
title_full Determinants of woody encroachment and cover in African savannas
title_fullStr Determinants of woody encroachment and cover in African savannas
title_full_unstemmed Determinants of woody encroachment and cover in African savannas
title_short Determinants of woody encroachment and cover in African savannas
title_sort determinants of woody encroachment and cover in african savannas
topic Concepts, Reviews and Syntheses
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5348564/
https://www.ncbi.nlm.nih.gov/pubmed/28116524
http://dx.doi.org/10.1007/s00442-017-3807-6
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