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Ecological palaeoecology in the neotropical Gran Sabana region: Long-term records of vegetation dynamics as a basis for ecological hypothesis testing

Ecological palaeoecology in the neotropical Gran Sabana region: Long-term records of vegetation dynamics as a basis for ecological hypothesis testing
Ecological palaeoecology in the neotropical Gran Sabana region: Long-term records of vegetation dynamics as a basis for ecological hypothesis testing

Long-term palaeoecological records are needed to test ecological hypotheses involving time, as short-term observations are of insufficient duration to capture natural variability. In this paper, we review the published palaeoecological evidence for the neotropical Gran Sabana (GS) region, to record the vegetation dynamics and evaluate the potential effects of natural climatic and anthropogenic (notably fire) drivers of change. The time period considered (last 13,000 years) covers major global climate changes and the arrival of humans in the region. The specific points addressed are climate-vegetation equilibrium, reversibility of vegetation changes, the origin of extant biodiversity and endemism patterns and biodiversity conservation in the face of global warming. Vegetation dynamics is reconstructed by pollen analysis and fire incidence is deduced from microscopic charcoal records. Palaeoclimatic inferences are derived from global and regional records using independent physico-chemical evidence to avoid circular reasoning. After analyzing all the long-term records available from both GS uplands and highlands, we conclude that: (1) Upland vegetation (mostly treeless savannas and savanna-forest mosaics, with occasional Mauritia palm swamps) is not in equilibrium with the dominant climates, but largely conditioned by burning practices; (2) a hypothetical natural or "original" vegetation type for these uplands has not been possible to identify due to continuous changes in both climate and human activities during the last 13,000 years; (3) at the time scale studied (millennial), the shift from forest to savanna is abrupt and irreversible due to the existence of tipping points, no matter the cause (natural or anthropogenic); (4) on the contrary, the shift from savanna to palm swamps is reversible at centennial time scales; (5) some of the reconstructed past vegetation types have no modern analogues owing to the individual species response to environmental shifts, leading to variations in community composition; (6) extant biodiversity and endemism patterns are not the result of a long history of topographical isolation, as previously proposed but, rather, the consequence of the action of climatic and palaeogeographic variations; (7) the projected global warming will likely exacerbate the expansion of upland savannas by favouring positive fire-climate feedbacks; (8) in the highlands, extinction by habitat loss will likely affect biodiversity but to a less extent that prognosticated by models based only on present-day climatic features; (9) future highland communities will likely be different to present ones due to the prevalence of individual species responses to global warming; and (10) conservation strategies at individual species level, rather than at community level, are enriched by long-term palaeoecological studies analyzed here. None of these conclusions would have been possible to derive from short-term neoecological observations.

Biodiversity conservation, Climate-vegetation disequilibrium, Community stability, Long-term ecology, Non-analogue communities, Origin of biodiversity
1433-8319
338-359
Rull, Valentí
afd31aba-0540-4788-abea-f5f9e3ec3021
Montoya, Encarni
7f93c60f-cc9c-4c5f-bb43-e42a38872e8e
Nogué, Sandra
5b464cff-a158-481f-8b7f-647c93d7a034
Vegas-Vilarrúbia, Teresa
f1a5df04-58b9-4d16-823c-47c193f63f01
Safont, Elisabet
ace2fe6a-a021-4179-8bc0-30cbf06aff84
Rull, Valentí
afd31aba-0540-4788-abea-f5f9e3ec3021
Montoya, Encarni
7f93c60f-cc9c-4c5f-bb43-e42a38872e8e
Nogué, Sandra
5b464cff-a158-481f-8b7f-647c93d7a034
Vegas-Vilarrúbia, Teresa
f1a5df04-58b9-4d16-823c-47c193f63f01
Safont, Elisabet
ace2fe6a-a021-4179-8bc0-30cbf06aff84

Rull, Valentí, Montoya, Encarni, Nogué, Sandra, Vegas-Vilarrúbia, Teresa and Safont, Elisabet (2013) Ecological palaeoecology in the neotropical Gran Sabana region: Long-term records of vegetation dynamics as a basis for ecological hypothesis testing. Perspectives in Plant Ecology, Evolution and Systematics, 15 (6), 338-359. (doi:10.1016/j.ppees.2013.07.004).

Record type: Review

Abstract

Long-term palaeoecological records are needed to test ecological hypotheses involving time, as short-term observations are of insufficient duration to capture natural variability. In this paper, we review the published palaeoecological evidence for the neotropical Gran Sabana (GS) region, to record the vegetation dynamics and evaluate the potential effects of natural climatic and anthropogenic (notably fire) drivers of change. The time period considered (last 13,000 years) covers major global climate changes and the arrival of humans in the region. The specific points addressed are climate-vegetation equilibrium, reversibility of vegetation changes, the origin of extant biodiversity and endemism patterns and biodiversity conservation in the face of global warming. Vegetation dynamics is reconstructed by pollen analysis and fire incidence is deduced from microscopic charcoal records. Palaeoclimatic inferences are derived from global and regional records using independent physico-chemical evidence to avoid circular reasoning. After analyzing all the long-term records available from both GS uplands and highlands, we conclude that: (1) Upland vegetation (mostly treeless savannas and savanna-forest mosaics, with occasional Mauritia palm swamps) is not in equilibrium with the dominant climates, but largely conditioned by burning practices; (2) a hypothetical natural or "original" vegetation type for these uplands has not been possible to identify due to continuous changes in both climate and human activities during the last 13,000 years; (3) at the time scale studied (millennial), the shift from forest to savanna is abrupt and irreversible due to the existence of tipping points, no matter the cause (natural or anthropogenic); (4) on the contrary, the shift from savanna to palm swamps is reversible at centennial time scales; (5) some of the reconstructed past vegetation types have no modern analogues owing to the individual species response to environmental shifts, leading to variations in community composition; (6) extant biodiversity and endemism patterns are not the result of a long history of topographical isolation, as previously proposed but, rather, the consequence of the action of climatic and palaeogeographic variations; (7) the projected global warming will likely exacerbate the expansion of upland savannas by favouring positive fire-climate feedbacks; (8) in the highlands, extinction by habitat loss will likely affect biodiversity but to a less extent that prognosticated by models based only on present-day climatic features; (9) future highland communities will likely be different to present ones due to the prevalence of individual species responses to global warming; and (10) conservation strategies at individual species level, rather than at community level, are enriched by long-term palaeoecological studies analyzed here. None of these conclusions would have been possible to derive from short-term neoecological observations.

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More information

Published date: 20 December 2013
Keywords: Biodiversity conservation, Climate-vegetation disequilibrium, Community stability, Long-term ecology, Non-analogue communities, Origin of biodiversity

Identifiers

Local EPrints ID: 445938
URI: http://eprints.soton.ac.uk/id/eprint/445938
ISSN: 1433-8319
PURE UUID: 35dcd278-3f1c-4a32-833d-87e8456792d2
ORCID for Sandra Nogué: ORCID iD orcid.org/0000-0003-0093-4252

Catalogue record

Date deposited: 14 Jan 2021 19:16
Last modified: 18 Feb 2021 17:25

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Contributors

Author: Valentí Rull
Author: Encarni Montoya
Author: Sandra Nogué ORCID iD
Author: Teresa Vegas-Vilarrúbia
Author: Elisabet Safont

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