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Vegetation state changes in the course of shrub encroachment in an African savanna since about 1850 CE and their potential drivers

1. Shrub encroachment has far‐reaching ecological and economic consequences in many ecosystems worldwide. Yet, compositional changes associated with shrub encroachment are often overlooked despite having important effects on ecosystem functioning. 2. We document the compositional change and potentia...

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Autores principales: Tabares, Ximena, Zimmermann, Heike, Dietze, Elisabeth, Ratzmann, Gregor, Belz, Lukas, Vieth‐Hillebrand, Andrea, Dupont, Lydie, Wilkes, Heinz, Mapani, Benjamin, Herzschuh, Ulrike
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6988543/
https://www.ncbi.nlm.nih.gov/pubmed/32015858
http://dx.doi.org/10.1002/ece3.5955
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author Tabares, Ximena
Zimmermann, Heike
Dietze, Elisabeth
Ratzmann, Gregor
Belz, Lukas
Vieth‐Hillebrand, Andrea
Dupont, Lydie
Wilkes, Heinz
Mapani, Benjamin
Herzschuh, Ulrike
author_facet Tabares, Ximena
Zimmermann, Heike
Dietze, Elisabeth
Ratzmann, Gregor
Belz, Lukas
Vieth‐Hillebrand, Andrea
Dupont, Lydie
Wilkes, Heinz
Mapani, Benjamin
Herzschuh, Ulrike
author_sort Tabares, Ximena
collection PubMed
description 1. Shrub encroachment has far‐reaching ecological and economic consequences in many ecosystems worldwide. Yet, compositional changes associated with shrub encroachment are often overlooked despite having important effects on ecosystem functioning. 2. We document the compositional change and potential drivers for a northern Namibian Combretum woodland transitioning into a Terminalia shrubland. We use a multiproxy record (pollen, sedimentary ancient DNA, biomarkers, compound‐specific carbon (δ(13)C) and deuterium (δD) isotopes, bulk carbon isotopes (δ(13)Corg), grain size, geochemical properties) from Lake Otjikoto at high taxonomical and temporal resolution. 3. We provide evidence that state changes in semiarid environments may occur on a scale of one century and that transitions between stable states can span around 80 years and are characterized by a unique vegetation composition. We demonstrate that the current grass/woody ratio is exceptional for the last 170 years, as supported by n‐alkane distributions and the δ(13)C and δ(13)Corg records. Comparing vegetation records to environmental proxy data and census data, we infer a complex network of global and local drivers of vegetation change. While our δD record suggests physiological adaptations of woody species to higher atmospheric pCO(2) concentration and drought, our vegetation records reflect the impact of broad‐scale logging for the mining industry, and the macrocharcoal record suggests a decrease in fire activity associated with the intensification of farming. Impact of selective grazing is reflected by changes in abundance and taxonomical composition of grasses and by an increase of nonpalatable and trampling‐resistant taxa. In addition, grain‐size and spore records suggest changes in the erodibility of soils because of reduced grass cover. 4. Synthesis. We conclude that transitions to an encroached savanna state are supported by gradual environmental changes induced by management strategies, which affected the resilience of savanna ecosystems. In addition, feedback mechanisms that reflect the interplay between management legacies and climate change maintain the encroached state.
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spelling pubmed-69885432020-02-03 Vegetation state changes in the course of shrub encroachment in an African savanna since about 1850 CE and their potential drivers Tabares, Ximena Zimmermann, Heike Dietze, Elisabeth Ratzmann, Gregor Belz, Lukas Vieth‐Hillebrand, Andrea Dupont, Lydie Wilkes, Heinz Mapani, Benjamin Herzschuh, Ulrike Ecol Evol Original Research 1. Shrub encroachment has far‐reaching ecological and economic consequences in many ecosystems worldwide. Yet, compositional changes associated with shrub encroachment are often overlooked despite having important effects on ecosystem functioning. 2. We document the compositional change and potential drivers for a northern Namibian Combretum woodland transitioning into a Terminalia shrubland. We use a multiproxy record (pollen, sedimentary ancient DNA, biomarkers, compound‐specific carbon (δ(13)C) and deuterium (δD) isotopes, bulk carbon isotopes (δ(13)Corg), grain size, geochemical properties) from Lake Otjikoto at high taxonomical and temporal resolution. 3. We provide evidence that state changes in semiarid environments may occur on a scale of one century and that transitions between stable states can span around 80 years and are characterized by a unique vegetation composition. We demonstrate that the current grass/woody ratio is exceptional for the last 170 years, as supported by n‐alkane distributions and the δ(13)C and δ(13)Corg records. Comparing vegetation records to environmental proxy data and census data, we infer a complex network of global and local drivers of vegetation change. While our δD record suggests physiological adaptations of woody species to higher atmospheric pCO(2) concentration and drought, our vegetation records reflect the impact of broad‐scale logging for the mining industry, and the macrocharcoal record suggests a decrease in fire activity associated with the intensification of farming. Impact of selective grazing is reflected by changes in abundance and taxonomical composition of grasses and by an increase of nonpalatable and trampling‐resistant taxa. In addition, grain‐size and spore records suggest changes in the erodibility of soils because of reduced grass cover. 4. Synthesis. We conclude that transitions to an encroached savanna state are supported by gradual environmental changes induced by management strategies, which affected the resilience of savanna ecosystems. In addition, feedback mechanisms that reflect the interplay between management legacies and climate change maintain the encroached state. John Wiley and Sons Inc. 2019-12-30 /pmc/articles/PMC6988543/ /pubmed/32015858 http://dx.doi.org/10.1002/ece3.5955 Text en © 2019 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
spellingShingle Original Research
Tabares, Ximena
Zimmermann, Heike
Dietze, Elisabeth
Ratzmann, Gregor
Belz, Lukas
Vieth‐Hillebrand, Andrea
Dupont, Lydie
Wilkes, Heinz
Mapani, Benjamin
Herzschuh, Ulrike
Vegetation state changes in the course of shrub encroachment in an African savanna since about 1850 CE and their potential drivers
title Vegetation state changes in the course of shrub encroachment in an African savanna since about 1850 CE and their potential drivers
title_full Vegetation state changes in the course of shrub encroachment in an African savanna since about 1850 CE and their potential drivers
title_fullStr Vegetation state changes in the course of shrub encroachment in an African savanna since about 1850 CE and their potential drivers
title_full_unstemmed Vegetation state changes in the course of shrub encroachment in an African savanna since about 1850 CE and their potential drivers
title_short Vegetation state changes in the course of shrub encroachment in an African savanna since about 1850 CE and their potential drivers
title_sort vegetation state changes in the course of shrub encroachment in an african savanna since about 1850 ce and their potential drivers
topic Original Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6988543/
https://www.ncbi.nlm.nih.gov/pubmed/32015858
http://dx.doi.org/10.1002/ece3.5955
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