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Durand M, Paillard J, Ménard MP, Suranyi T, Grondin P, Blarquez O. Pollen identification through convolutional neural networks: First application on a full fossil pollen sequence. PLoS One 2024; 19:e0302424. [PMID: 38687746 PMCID: PMC11060525 DOI: 10.1371/journal.pone.0302424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 04/03/2024] [Indexed: 05/02/2024] Open
Abstract
The automation of pollen identification has seen vast improvements in the past years, with Convolutional Neural Networks coming out as the preferred tool to train models. Still, only a small portion of works published on the matter address the identification of fossil pollen. Fossil pollen is commonly extracted from organic sediment cores and are used by paleoecologists to reconstruct past environments, flora, vegetation, and their evolution through time. The automation of fossil pollen identification would allow paleoecologists to save both time and money while reducing bias and uncertainty. However, Convolutional Neural Networks require a large amount of data for training and databases of fossilized pollen are rare and often incomplete. Since machine learning models are usually trained using labelled fresh pollen associated with many different species, there exists a gap between the training data and target data. We propose a method for a large-scale fossil pollen identification workflow. Our proposed method employs an accelerated fossil pollen extraction protocol and Convolutional Neural Networks trained on the labelled fresh pollen of the species most commonly found in Northeastern American organic sediments. We first test our model on fresh pollen and then on a full fossil pollen sequence totalling 196,526 images. Our model achieved an average per class accuracy of 91.2% when tested against fresh pollen. However, we find that our model does not perform as well when tested on fossil data. While our model is overconfident in its predictions, the general abundance patterns remain consistent with the traditional palynologist IDs. Although not yet capable of accurately classifying a whole fossil pollen sequence, our model serves as a proof of concept towards creating a full large-scale identification workflow.
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Affiliation(s)
- Médéric Durand
- Département de Géographie, Université de Montréal, Montréal, Québec, Canada
| | - Jordan Paillard
- Département de Géographie, Université de Montréal, Montréal, Québec, Canada
| | - Marie-Pier Ménard
- Département de Géographie, Université de Montréal, Montréal, Québec, Canada
| | - Thomas Suranyi
- Département de Géographie, Université de Montréal, Montréal, Québec, Canada
- Laboratoire Chrono-Environnement, UMR 6249 CNRS, Université de Franche-Comté, Besançon, France
| | - Pierre Grondin
- Direction de la recherche forestière, Ministère des Ressources naturelles et des Forêts, Québec City, Québec, Canada
| | - Olivier Blarquez
- Département de Géographie, Université de Montréal, Montréal, Québec, Canada
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Dietze E, Brykała D, Schreuder LT, Jażdżewski K, Blarquez O, Brauer A, Dietze M, Obremska M, Ott F, Pieńczewska A, Schouten S, Hopmans EC, Słowiński M. Human-induced fire regime shifts during 19th century industrialization: A robust fire regime reconstruction using northern Polish lake sediments. PLoS One 2019; 14:e0222011. [PMID: 31525210 PMCID: PMC6746370 DOI: 10.1371/journal.pone.0222011] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 08/20/2019] [Indexed: 11/19/2022] Open
Abstract
Fire regime shifts are driven by climate and natural vegetation changes, but can be strongly affected by human land management. Yet, it is poorly known how humans have influenced fire regimes prior to active wildfire suppression. Among the last 250 years, the human contribution to the global increase in fire occurrence during the mid-19th century is especially unclear, as data sources are limited. Here, we test the extent to which forest management has driven fire regime shifts in a temperate forest landscape. We combine multiple fire proxies (macroscopic charcoal and fire-related biomarkers) derived from highly resolved lake sediments (i.e., 3–5 years per sample), and apply a new statistical approach to classify source area- and temperature-specific fire regimes (biomass burnt, fire episodes). We compare these records with independent climate and vegetation reconstructions. We find two prominent fire regime shifts during the 19th and 20th centuries, driven by an adaptive socio-ecological cycle in human forest management. Although individual fire episodes were triggered mainly by arson (as described in historical documents) during dry summers, the biomass burnt increased unintentionally during the mid-19th century due to the plantation of flammable, fast-growing pine tree monocultures needed for industrialization. State forest management reacted with active fire management and suppression during the 20th century. However, pine cover has been increasing since the 1990s and climate projections predict increasingly dry conditions, suggesting a renewed need for adaptations to reduce the increasing fire risk.
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Affiliation(s)
- Elisabeth Dietze
- Alfred-Wegener-Institute Helmholtz Center for Polar and Marine Research, Research Unit Potsdam, Polar Terrestrial Environmental Systems, Potsdam, Germany
- GFZ German Research Centre for Geosciences, Section Climate Dynamics and Landscape Evolution, Potsdam, Germany
- * E-mail:
| | - Dariusz Brykała
- Polish Academy of Sciences, Institute of Geography and Spatial Organization, Toruń, Poland
| | - Laura T. Schreuder
- Royal Netherlands Institute for Sea Research, Department of Marine Microbiology and Biogeochemistry, and Utrecht University, Texel, The Netherlands
| | | | - Olivier Blarquez
- Département de Géographie, Université de Montréal, Montréal, Québec, Canada
| | - Achim Brauer
- GFZ German Research Centre for Geosciences, Section Climate Dynamics and Landscape Evolution, Potsdam, Germany
| | - Michael Dietze
- GFZ German Research Centre for Geosciences, Section Geomorphology, Potsdam, Germany
| | - Milena Obremska
- Polish Academy of Sciences, Institute of Geological Sciences, Warsaw, Poland
| | - Florian Ott
- Max Planck Institute for the Science of Human History, Department of Archaeology, Jena, Germany
| | - Anna Pieńczewska
- Kaziemierz Wielki University, Institute of Geography, Bydgoszcz, Poland
| | - Stefan Schouten
- Royal Netherlands Institute for Sea Research, Department of Marine Microbiology and Biogeochemistry, and Utrecht University, Texel, The Netherlands
- Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands
| | - Ellen C. Hopmans
- Royal Netherlands Institute for Sea Research, Department of Marine Microbiology and Biogeochemistry, and Utrecht University, Texel, The Netherlands
| | - Michał Słowiński
- Polish Academy of Sciences, Institute of Geography and Spatial Organization, Warsaw, Poland
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Aleman JC, Blarquez O, Elenga H, Paillard J, Kimpuni V, Itoua G, Issele G, Staver AC. Palaeo-trajectories of forest savannization in the southern Congo. Biol Lett 2019; 15:20190284. [PMID: 31455171 DOI: 10.1098/rsbl.2019.0284] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Tropical savannah and forest are thought to represent alternative stable states in ecosystem structure in some climates. The implication is that biomes are maintained by positive feedbacks, e.g. with fire, and that historical distributions could play a role in determining modern ones. In this context, climate alone does not govern transitions between biomes, and understanding the causes and pathways of such transitions becomes crucial. Here, we use a multi-proxy analysis of a 2000-year core to evaluate modes of transition in vegetation structure and fire regimes. We demonstrate a first transition ca 1540 BP, when a cyclic fire regime entered a forested landscape, eventually resulting, by ca 1060 BP, in a transition to a more open savannah-like or mosaicked structure. This pattern may parallel currently accelerating fire regimes in tropical forests suggesting that fires can savannize forests, but perhaps more slowly than feared. Finally, ca 540 BP, a drought combined with anthropogenic influences resulted in a conclusive transition to savannah, probably resembling the modern landscape in the region. We show here that fire interacted with drought to transition forest to savannah, suggesting that disturbance by fire can be a major driver of biome change.
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Affiliation(s)
- Julie C Aleman
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA.,Département de Géographie, Université de Montréal, Montreal, Quebec, Canada
| | - Olivier Blarquez
- Département de Géographie, Université de Montréal, Montreal, Quebec, Canada
| | - Hilaire Elenga
- Département de Biologie, Université Marien Ngouabi, Brazzaville, Republic of the Congo.,Centre de Recherches Géologiques et Minières, Brazzaville, Republic of the Congo
| | - Jordan Paillard
- Département de Géographie, Université de Montréal, Montreal, Quebec, Canada
| | - Victor Kimpuni
- Département de Biologie, Université Marien Ngouabi, Brazzaville, Republic of the Congo
| | - Gaubin Itoua
- Centre de Recherches Géologiques et Minières, Brazzaville, Republic of the Congo
| | - Gauthier Issele
- Centre de Recherches Géologiques et Minières, Brazzaville, Republic of the Congo
| | - A Carla Staver
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA
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Carcaillet C, Blarquez O. Glacial refugia in the south-western Alps? New Phytol 2019; 222:663-667. [PMID: 30734310 DOI: 10.1111/nph.15673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Accepted: 12/31/2018] [Indexed: 06/09/2023]
Affiliation(s)
- Christopher Carcaillet
- Laboratory for Ecology of Natural and Anthropised Hydrosystems (UMR 5023 CNRS ENTPE), Université Claude Bernard-Lyon, Villeurbanne, F-69622, France
- Paris Sciences & Lettres University (PSL), École Pratique des Hautes Études (EPHE), 4-14 rue Ferrus, F-75014, Paris, France
| | - Olivier Blarquez
- Département de Géographie, Université de Montréal, C.P. 6128 Succ. Centre Ville, Montréal, QC, H3C 3J7, Canada
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Molinari C, Lehsten V, Blarquez O, Carcaillet C, Davis BAS, Kaplan JO, Clear J, Bradshaw RHW. The climate, the fuel and the land use: Long-term regional variability of biomass burning in boreal forests. Glob Chang Biol 2018; 24:4929-4945. [PMID: 29959810 DOI: 10.1111/gcb.14380] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 06/08/2018] [Accepted: 06/13/2018] [Indexed: 06/08/2023]
Abstract
The influence of different drivers on changes in North American and European boreal forests biomass burning (BB) during the Holocene was investigated based on the following hypotheses: land use was important only in the southernmost regions, while elsewhere climate was the main driver modulated by changes in fuel type. BB was reconstructed by means of 88 sedimentary charcoal records divided into six different site clusters. A statistical approach was used to explore the relative contribution of (a) pollen-based mean July/summer temperature and mean annual precipitation reconstructions, (b) an independent model-based scenario of past land use (LU), and (c) pollen-based reconstructions of plant functional types (PFTs) on BB. Our hypotheses were tested with: (a) a west-east northern boreal sector with changing climatic conditions and a homogeneous vegetation, and (b) a north-south European boreal sector characterized by gradual variation in both climate and vegetation composition. The processes driving BB in boreal forests varied from one region to another during the Holocene. However, general trends in boreal biomass burning were primarily controlled by changes in climate (mean annual precipitation in Alaska, northern Quebec, and northern Fennoscandia, and mean July/summer temperature in central Canada and central Fennoscandia) and, secondarily, by fuel composition (BB positively correlated with the presence of boreal needleleaf evergreen trees in Alaska and in central and southern Fennoscandia). Land use played only a marginal role. A modification towards less flammable tree species (by promoting deciduous stands over fire-prone conifers) could contribute to reduce circumboreal wildfire risk in future warmer periods.
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Affiliation(s)
- Chiara Molinari
- Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden
| | - Veiko Lehsten
- Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden
- Department of Macroecology and Landscape Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research, Birmensdorf, Switzerland
| | - Olivier Blarquez
- Département de Géographie, Université de Montréal, Montréal, Québec, Canada
| | - Christopher Carcaillet
- École Pratique des Hautes Études (EPHE), PSL Research University, Paris, France
- Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés, UMR 5023, Université Claude Bernard Lyon 1, CNRS, ENTPE, Villeurbanne, France
| | - Basil A S Davis
- Institute of Earth Surface Dynamics, University of Lausanne, Lausanne, Switzerland
| | | | - Jennifer Clear
- Department of Geography and Environmental Science, Liverpool Hope University, Liverpool, UK
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Carcaillet C, Blarquez O. Fire ecology of a tree glacial refugium on a nunatak with a view on Alpine glaciers. New Phytol 2017; 216:1281-1290. [PMID: 28805959 DOI: 10.1111/nph.14721] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 06/26/2017] [Indexed: 06/07/2023]
Abstract
In paleoecology, the function of biomass as a fire driver has become a focus of attention in cold ecosystems, and concerns have been raised about climate in this context. Little is known about the fire frequency and fire-plant relationships during glaciation when woodlands were limited and the climate was cold. Fire history and tree biomass were reconstructed from sedimentary charcoal and macroremains, respectively, archived in lake sediments from the western Alps. Two nunataks were investigated, both with lacustrine sediments covering the last 21 000 yr at least. During the Last Glacial Maximum (LGM) and the Lateglacial, fires occurred only on the nunatak sheltering woody plants. Cembra pine (Pinus cembra) and larch (Larix decidua) survived above glaciers during the LGM, thus evidencing a biological refugium and supporting the nunatak theory. We highlighted a long-term relationship between fires and dominant trees over the last 21 000 yr, where fire frequencies track the global climate and the local changes in tree biomass. Glacial climate (dry, cold) does not rule out fires. Fuel load and composition were significant fire drivers, with cembra pine dominating during colder periods with rare fires, and larch during the warmer Holocene with frequent fires. These findings increase knowledge of fire ecology in cold environments, and open perspectives in tree population genetics by considering new areas of tree glacial refugia in Europe.
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Affiliation(s)
- Christopher Carcaillet
- PSL Research University Paris, Ecole Pratique des Hautes Etudes, 4-14 rue Ferrus, Paris, F-75014, France
- Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés (UMR5023 CNRS), Université Lyon 1, Villeurbanne Cedex, F-69622, France
- LTER Zone Atelier Alpes, Grenoble, F-38000, France
- International Associated Laboratory (LIA France-Canada MONTABOR), Montpellier, F-34000, France
| | - Olivier Blarquez
- International Associated Laboratory (LIA France-Canada MONTABOR), Montpellier, F-34000, France
- Département de Géographie, Université de Montréal, C.P. 6128 Succ. Centre Ville, Montréal, QC, H3C 3J7, Canada
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7
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Aleman JC, Blarquez O, Staver CA. Land-use change outweighs projected effects of changing rainfall on tree cover in sub-Saharan Africa. Glob Chang Biol 2016; 22:3013-3025. [PMID: 27090855 DOI: 10.1111/gcb.13299] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 03/17/2016] [Accepted: 03/18/2016] [Indexed: 06/05/2023]
Abstract
Global change will likely affect savanna and forest structure and distributions, with implications for diversity within both biomes. Few studies have examined the impacts of both expected precipitation and land use changes on vegetation structure in the future, despite their likely severity. Here, we modeled tree cover in sub-Saharan Africa, as a proxy for vegetation structure and land cover change, using climatic, edaphic, and anthropic data (R(2) = 0.97). Projected tree cover for the year 2070, simulated using scenarios that include climate and land use projections, generally decreased, both in forest and savanna, although the directionality of changes varied locally. The main driver of tree cover changes was land use change; the effects of precipitation change were minor by comparison. Interestingly, carbon emissions mitigation via increasing biofuels production resulted in decreases in tree cover, more severe than scenarios with more intense precipitation change, especially within savannas. Evaluation of tree cover change against protected area extent at the WWF Ecoregion scale suggested areas of high biodiversity and ecosystem services concern. Those forests most vulnerable to large decreases in tree cover were also highly protected, potentially buffering the effects of global change. Meanwhile, savannas, especially where they immediately bordered forests (e.g. West and Central Africa), were characterized by a dearth of protected areas, making them highly vulnerable. Savanna must become an explicit policy priority in the face of climate and land use change if conservation and livelihoods are to remain viable into the next century.
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Affiliation(s)
- Julie C Aleman
- Ecology and Evolutionary Biology, Yale University, P.O. Box 208106, New Haven, CT 06520, USA
| | - Olivier Blarquez
- Département de Géographie, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, QC H3C 3J7, Canada
| | - Carla A Staver
- Ecology and Evolutionary Biology, Yale University, P.O. Box 208106, New Haven, CT 06520, USA
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Carcaillet C, Ali AA, Blarquez O, Genries A, Mourier B, Bremond L. Spatial variability of fire history in subalpine forests: From natural to cultural regimes. Écoscience 2015. [DOI: 10.2980/16-1-3189] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Blarquez O, Ali AA, Girardin MP, Grondin P, Fréchette B, Bergeron Y, Hély C. Regional paleofire regimes affected by non-uniform climate, vegetation and human drivers. Sci Rep 2015; 5:13356. [PMID: 26330162 PMCID: PMC4557068 DOI: 10.1038/srep13356] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 07/23/2015] [Indexed: 11/09/2022] Open
Abstract
Climate, vegetation and humans act on biomass burning at different spatial and temporal scales. In this study, we used a dense network of sedimentary charcoal records from eastern Canada to reconstruct regional biomass burning history over the last 7000 years at the scale of four potential vegetation types: open coniferous forest/tundra, boreal coniferous forest, boreal mixedwood forest and temperate forest. The biomass burning trajectories were compared with regional climate trends reconstructed from general circulation models, tree biomass reconstructed from pollen series, and human population densities. We found that non-uniform climate, vegetation and human drivers acted on regional biomass burning history. In the open coniferous forest/tundra and dense coniferous forest, the regional biomass burning was primarily shaped by gradual establishment of less climate-conducive burning conditions over 5000 years. In the mixed boreal forest an increasing relative proportion of flammable conifers in landscapes since 2000 BP contributed to maintaining biomass burning constant despite climatic conditions less favourable to fires. In the temperate forest, biomass burning was uncoupled with climatic conditions and the main driver was seemingly vegetation until European colonization, i.e. 300 BP. Tree biomass and thus fuel accumulation modulated fire activity, an indication that biomass burning is fuel-dependent and notably upon long-term co-dominance shifts between conifers and broadleaf trees.
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Affiliation(s)
- Olivier Blarquez
- Département de Géographie, Université de Montréal, Montréal, Québec, Canada
| | - Adam A Ali
- Institut des Sciences de l'Evolution de Montpellier, CNRS-IRD-Université Montpellier 2-EPHE, Montpellier, France
| | - Martin P Girardin
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, Quebec, Québec, Canada
| | - Pierre Grondin
- Ministère des Forêts, de la Faune et des Parcs, Direction de la recherche forestière, Québec, Canada
| | - Bianca Fréchette
- Centre de recherche en géochimie et géodynamique, Université du Québec à Montréal, Montréal, Québec, Canada
| | - Yves Bergeron
- Centre d'étude de la Forêt, Université du Québec à Montréal, Montréal, Québec, Québec, Canada.,Natural Sciences and Engineering Research Council of Canada Industrial Chair in Sustainable Forest Management, Forest Research Institute, Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, Québec, Canada
| | - Christelle Hély
- Institut des Sciences de l'Evolution de Montpellier, CNRS-IRD-Université Montpellier 2-EPHE, Montpellier, France
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Oris F, Asselin H, Finsinger W, Hély C, Blarquez O, Ferland ME, Bergeron Y, Ali AA. Long-term fire history in northern Quebec: implications for the northern limit of commercial forests. J Appl Ecol 2014. [DOI: 10.1111/1365-2664.12240] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- France Oris
- NSERC-UQAT-UQAM Industrial Chair in Sustainable Forest Management; 445 boul. de l'Université Rouyn-Noranda Québec J9X 5E4 Canada
- Centre d'Etude de la Forêt; Université du Québec à Montréal; Montreal Québec H3C 3P8 Canada
| | - Hugo Asselin
- NSERC-UQAT-UQAM Industrial Chair in Sustainable Forest Management; 445 boul. de l'Université Rouyn-Noranda Québec J9X 5E4 Canada
- Centre d'Etude de la Forêt; Université du Québec à Montréal; Montreal Québec H3C 3P8 Canada
| | - Walter Finsinger
- Centre de Bio-Archéologie et d'Ecologie (UMR5059 CNRS/UM2/EPHE); PALECO; Institut de Botanique; 163 rue Broussonnet Montpellier F-34090 France
| | - Christelle Hély
- Centre de Bio-Archéologie et d'Ecologie (UMR5059 CNRS/UM2/EPHE); PALECO; Institut de Botanique; 163 rue Broussonnet Montpellier F-34090 France
| | - Olivier Blarquez
- NSERC-UQAT-UQAM Industrial Chair in Sustainable Forest Management; 445 boul. de l'Université Rouyn-Noranda Québec J9X 5E4 Canada
- Centre d'Etude de la Forêt; Université du Québec à Montréal; Montreal Québec H3C 3P8 Canada
| | - Marie-Eve Ferland
- Groupe de Recherche Interuniversitaire en Limnologie et en Environnement Aquatique; Département des Sciences Biologiques; Université du Québec à Montréal; Case Postale 8888, Succ. Centre-ville Montréal H3C 3P8 Canada
| | - Yves Bergeron
- NSERC-UQAT-UQAM Industrial Chair in Sustainable Forest Management; 445 boul. de l'Université Rouyn-Noranda Québec J9X 5E4 Canada
- Centre d'Etude de la Forêt; Université du Québec à Montréal; Montreal Québec H3C 3P8 Canada
| | - Adam A. Ali
- NSERC-UQAT-UQAM Industrial Chair in Sustainable Forest Management; 445 boul. de l'Université Rouyn-Noranda Québec J9X 5E4 Canada
- Centre de Bio-Archéologie et d'Ecologie (UMR5059 CNRS/UM2/EPHE); PALECO; Institut de Botanique; 163 rue Broussonnet Montpellier F-34090 France
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Blarquez O, Carcaillet C, Frejaville T, Bergeron Y. Disentangling the trajectories of alpha, beta and gamma plant diversity of North American boreal ecoregions since 15,500 years. Front Ecol Evol 2014. [DOI: 10.3389/fevo.2014.00006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Girardin MP, Ali AA, Carcaillet C, Blarquez O, Hély C, Terrier A, Genries A, Bergeron Y. Vegetation limits the impact of a warm climate on boreal wildfires. New Phytol 2013; 199:1001-1011. [PMID: 23691916 DOI: 10.1111/nph.12322] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Accepted: 04/07/2013] [Indexed: 06/02/2023]
Abstract
Strategic introduction of less flammable broadleaf vegetation into landscapes was suggested as a management strategy for decreasing the risk of boreal wildfires projected under climatic change. However, the realization and strength of this offsetting effect in an actual environment remain to be demonstrated. Here we combined paleoecological data, global climate models and wildfire modelling to assess regional fire frequency (RegFF, i.e. the number of fires through time) in boreal forests as it relates to tree species composition and climate over millennial time-scales. Lacustrine charcoals from northern landscapes of eastern boreal Canada indicate that RegFF during the mid-Holocene (6000-3000 yr ago) was significantly higher than pre-industrial RegFF (AD c. 1750). In southern landscapes, RegFF was not significantly higher than the pre-industrial RegFF in spite of the declining drought severity. The modelling experiment indicates that the high fire risk brought about by a warmer and drier climate in the south during the mid-Holocene was offset by a higher broadleaf component. Our data highlight an important function for broadleaf vegetation in determining boreal RegFF in a warmer climate. We estimate that its feedback may be large enough to offset the projected climate change impacts on drought conditions.
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Affiliation(s)
- Martin P Girardin
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S, PO Box 10380, Stn. Sainte-Foy, Quebec, QC, G1V 4C7, Canada
- Centre d'étude de la forêt, Université du Québec à Montréal, C.P. 8888, Montréal, Québec, H3C 3P8, Canada
| | - Adam A Ali
- Centre de Bio-Archéologie et d'Ecologie, Unité Mixte de Recherche (UMR) 5059 Centre National de la Recherche Scientifique (CNRS), École Pratique des Hautes Études (EPHE), Institut de Botanique, F-34090, Montpellier, France
- Natural Sciences and Engineering Research Council of Canada Industrial Chair in Sustainable Forest Management, Forest Research Institute, Université du Québec en Abitibi-Témiscamingue, 445 boulevard de l'Université, Rouyn-Noranda, Québec, J9X 5E4, Canada
| | - Christopher Carcaillet
- Centre d'étude de la forêt, Université du Québec à Montréal, C.P. 8888, Montréal, Québec, H3C 3P8, Canada
- Centre de Bio-Archéologie et d'Ecologie, Unité Mixte de Recherche (UMR) 5059 Centre National de la Recherche Scientifique (CNRS), École Pratique des Hautes Études (EPHE), Institut de Botanique, F-34090, Montpellier, France
- Paléoenvironnements et Chronoécologie (PALECO), École Pratique des Hautes Études (EPHE), Institut de Botanique, F-34090, Montpellier, France
| | - Olivier Blarquez
- Centre d'étude de la forêt, Université du Québec à Montréal, C.P. 8888, Montréal, Québec, H3C 3P8, Canada
| | - Christelle Hély
- Centre de Bio-Archéologie et d'Ecologie, Unité Mixte de Recherche (UMR) 5059 Centre National de la Recherche Scientifique (CNRS), École Pratique des Hautes Études (EPHE), Institut de Botanique, F-34090, Montpellier, France
- Paléoenvironnements et Chronoécologie (PALECO), École Pratique des Hautes Études (EPHE), Institut de Botanique, F-34090, Montpellier, France
| | - Aurélie Terrier
- Centre d'étude de la forêt, Université du Québec à Montréal, C.P. 8888, Montréal, Québec, H3C 3P8, Canada
| | - Aurélie Genries
- Centre de Bio-Archéologie et d'Ecologie, Unité Mixte de Recherche (UMR) 5059 Centre National de la Recherche Scientifique (CNRS), École Pratique des Hautes Études (EPHE), Institut de Botanique, F-34090, Montpellier, France
| | - Yves Bergeron
- Centre d'étude de la forêt, Université du Québec à Montréal, C.P. 8888, Montréal, Québec, H3C 3P8, Canada
- Natural Sciences and Engineering Research Council of Canada Industrial Chair in Sustainable Forest Management, Forest Research Institute, Université du Québec en Abitibi-Témiscamingue, 445 boulevard de l'Université, Rouyn-Noranda, Québec, J9X 5E4, Canada
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13
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Abstract
We developed an algorithm to improve richness assessment based on paleoecological series, considering sample features such as their temporal resolutions or their volumes. Our new method can be applied to both high- and low-count size proxies, i.e. pollen and plant macroremain records, respectively. While pollen generally abounds in sediments, plant macroremains are generally rare, thus leading to difficulties to compute paleo-biodiversity indices. Our approach uses resampled macroremain influxes that enable the computation of the rarefaction index for the low influx records. The raw counts are resampled to a constant resolution and sample volume by interpolating initial sample ages at a constant time interval using the age∼depth model. Then, the contribution of initial counts and volume to each interpolated sample is determined by calculating a proportion matrix that is in turn used to obtain regularly spaced time series of pollen and macroremain influx. We applied this algorithm to sedimentary data from a subalpine lake situated in the European Alps. The reconstructed total floristic richness at the study site increased gradually when both pollen and macroremain records indicated a decrease in relative abundances of shrubs and an increase in trees from 11,000 to 7,000 cal BP. This points to an ecosystem change that favored trees against shrubs, whereas herb abundance remained stable. Since 6,000 cal BP, local richness decreased based on plant macroremains, while pollen-based richness was stable. The reconstructed richness and evenness are interrelated confirming the difficulty to distinguish these two aspects for the studies in paleo-biodiversity. The present study shows that low-influx bio-proxy records (here macroremains) can be used to reconstruct stand diversity and address ecological issues. These developments on macroremain and pollen records may contribute to bridge the gap between paleoecology and biodiversity studies.
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Affiliation(s)
- Olivier Blarquez
- Centre for Bio-Archaeology and Ecology, Université Montpellier 2, Centre National de la Recherche Scientifique, Montpellier, France
- Paleoenvironments and Chronoecology, École Pratique des Hautes Études, Montpellier, France
- Centre for Forest Research, Université du Québec à Montréal, Montréal, Québec, Canada
- * E-mail:
| | - Walter Finsinger
- Centre for Bio-Archaeology and Ecology, Université Montpellier 2, Centre National de la Recherche Scientifique, Montpellier, France
| | - Christopher Carcaillet
- Centre for Bio-Archaeology and Ecology, Université Montpellier 2, Centre National de la Recherche Scientifique, Montpellier, France
- Paleoenvironments and Chronoecology, École Pratique des Hautes Études, Montpellier, France
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14
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Abstract
BACKGROUND Forecasting the effects of global changes on high altitude ecosystems requires an understanding of the long-term relationships between biota and forcing factors to identify resilience thresholds. Fire is a crucial forcing factor: both fuel build-up from land-abandonment in European mountains, and more droughts linked to global warming are likely to increase fire risks. METHODS To assess the vegetation response to fire on a millennium time-scale, we analyzed evidence of stand-to-local vegetation dynamics derived from sedimentary plant macroremains from two subalpine lakes. Paleobotanical reconstructions at high temporal resolution, together with a fire frequency reconstruction inferred from sedimentary charcoal, were analyzed by Superposed Epoch Analysis to model plant behavior before, during and after fire events. PRINCIPAL FINDINGS We show that fuel build-up from arolla pine (Pinus cembra) always precedes fires, which is immediately followed by a rapid increase of birch (Betula sp.), then by ericaceous species after 25-75 years, and by herbs after 50-100 years. European larch (Larix decidua), which is the natural co-dominant species of subalpine forests with Pinus cembra, is not sensitive to fire, while the abundance of Pinus cembra is altered within a 150-year period after fires. A long-term trend in vegetation dynamics is apparent, wherein species that abound later in succession are the functional drivers, loading the environment with fuel for fires. This system can only be functional if fires are mainly driven by external factors (e.g. climate), with the mean interval between fires being longer than the minimum time required to reach the late successional stage, here 150 years. CONCLUSION Current global warming conditions which increase drought occurrences, combined with the abandonment of land in European mountain areas, creates ideal ecological conditions for the ignition and the spread of fire. A fire return interval of less than 150 years would threaten the dominant species and might override the resilience of subalpine forests.
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Affiliation(s)
- Olivier Blarquez
- Paleoenvironments and Chronoecology, Ecole Pratique des Hautes Etudes, Montpellier, France.
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