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  1. Article ; Online: Response of Amazonian forests to mid-Holocene drought: A model-data comparison.

    Smith, Richard J / Singarayer, Joy S / Mayle, Francis E

    Global change biology

    2021  Volume 28, Issue 1, Page(s) 201–226

    Abstract: There is a major concern for the fate of Amazonia over the coming century in the face of anthropogenic climate change. A key area of uncertainty is the scale of rainforest dieback to be expected under a future, drier climate. In this study, we use the ... ...

    Abstract There is a major concern for the fate of Amazonia over the coming century in the face of anthropogenic climate change. A key area of uncertainty is the scale of rainforest dieback to be expected under a future, drier climate. In this study, we use the middle Holocene (ca. 6000 years before present) as an approximate analogue for a drier future, given that palaeoclimate data show much of Amazonia was significantly drier than present at this time. Here, we use an ensemble of climate and vegetation models to explore the sensitivity of Amazonian biomes to mid-Holocene climate change. For this, we employ three dynamic vegetation models (JULES, IBIS, and SDGVM) forced by the bias-corrected mid-Holocene climate simulations from seven models that participated in the Palaeoclimate Modelling Intercomparison Project 3 (PMIP3). These model outputs are compared with a multi-proxy palaeoecological dataset to gain a better understanding of where in Amazonia we have most confidence in the mid-Holocene vegetation simulations. A robust feature of all simulations and palaeodata is that the central Amazonian rainforest biome is unaffected by mid-Holocene drought. Greater divergence in mid-Holocene simulations exists in ecotonal eastern and southern Amazonia. Vegetation models driven with climate models that simulate a drier mid-Holocene (100-150 mm per year decrease) better capture the observed (palaeodata) tropical forest dieback in these areas. Based on the relationship between simulated rainfall decrease and vegetation change, we find indications that in southern Amazonia the rate of tropical forest dieback was ~125,000 km
    MeSH term(s) Climate Change ; Climate Models ; Droughts ; Forests ; Humans ; Trees
    Language English
    Publishing date 2021-10-25
    Publishing country England
    Document type Journal Article
    ZDB-ID 1281439-8
    ISSN 1365-2486 ; 1354-1013
    ISSN (online) 1365-2486
    ISSN 1354-1013
    DOI 10.1111/gcb.15929
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: Response of Amazonian forests to mid‐Holocene drought: A model‐data comparison

    Smith, Richard J. / Singarayer, Joy S. / Mayle, Francis E.

    Global change biology. 2022 Jan., v. 28, no. 1

    2022  

    Abstract: There is a major concern for the fate of Amazonia over the coming century in the face of anthropogenic climate change. A key area of uncertainty is the scale of rainforest dieback to be expected under a future, drier climate. In this study, we use the ... ...

    Abstract There is a major concern for the fate of Amazonia over the coming century in the face of anthropogenic climate change. A key area of uncertainty is the scale of rainforest dieback to be expected under a future, drier climate. In this study, we use the middle Holocene (ca. 6000 years before present) as an approximate analogue for a drier future, given that palaeoclimate data show much of Amazonia was significantly drier than present at this time. Here, we use an ensemble of climate and vegetation models to explore the sensitivity of Amazonian biomes to mid‐Holocene climate change. For this, we employ three dynamic vegetation models (JULES, IBIS, and SDGVM) forced by the bias‐corrected mid‐Holocene climate simulations from seven models that participated in the Palaeoclimate Modelling Intercomparison Project 3 (PMIP3). These model outputs are compared with a multi‐proxy palaeoecological dataset to gain a better understanding of where in Amazonia we have most confidence in the mid‐Holocene vegetation simulations. A robust feature of all simulations and palaeodata is that the central Amazonian rainforest biome is unaffected by mid‐Holocene drought. Greater divergence in mid‐Holocene simulations exists in ecotonal eastern and southern Amazonia. Vegetation models driven with climate models that simulate a drier mid‐Holocene (100–150 mm per year decrease) better capture the observed (palaeodata) tropical forest dieback in these areas. Based on the relationship between simulated rainfall decrease and vegetation change, we find indications that in southern Amazonia the rate of tropical forest dieback was ~125,000 km² per 100 mm rainfall decrease in the mid‐Holocene. This provides a baseline sensitivity of tropical forests to drought for this region (without human‐driven changes to greenhouse gases, fire, and deforestation). We highlight the need for more palaeoecological and palaeoclimate data across lowland Amazonia to constrain model responses.
    Keywords Biological Sciences ; Holocene epoch ; climate ; climate change ; data collection ; deforestation ; dieback ; drought ; ecosystems ; greenhouses ; paleoclimatology ; paleoecology ; rain ; rain forests ; rainfall simulation ; tropical forests ; uncertainty ; Amazonia
    Language English
    Dates of publication 2022-01
    Size p. 201-226.
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note JOURNAL ARTICLE
    ZDB-ID 1281439-8
    ISSN 1365-2486 ; 1354-1013
    ISSN (online) 1365-2486
    ISSN 1354-1013
    DOI 10.1111/gcb.15929
    Database NAL-Catalogue (AGRICOLA)

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  3. Article: Ecosystem turnover in palaeoecological records: The sensitivity of pollen and phytolith proxies to detecting vegetation change in southwestern Amazonia

    Plumpton, Heather / Mayle, Francis / Whitney, Bronwen

    Holocene. 2019 Nov., v. 29, no. 11

    2019  

    Abstract: Identification of ecosystem turnover in the palaeo-vegetation record is important for understanding the resilience of ecosystems to past environmental change. There is uncertainty over the ability of different types of palaeo-vegetation proxies to detect ...

    Abstract Identification of ecosystem turnover in the palaeo-vegetation record is important for understanding the resilience of ecosystems to past environmental change. There is uncertainty over the ability of different types of palaeo-vegetation proxies to detect ecosystem turnover. The aim of this paper is to compare the sensitivity of two palaeo-vegetation proxies – pollen and phytoliths – to changes within and between three key tropical South American ecosystems: evergreen forest, dry forest and savannah. A quantitative approach is used to assess the sensitivity of these two proxies to vegetation changes, based on the variability of proxy assemblages from 1-ha ecological plots in ecotonal south-west Amazonia. This modern dataset of proxy variability within evergreen forest, dry forest and savannah plots is then used to define thresholds for proxy variability which differentiate floristic changes within an ecosystem from ecosystem turnover. These thresholds are applied to two palaeo-vegetation records from NE Bolivia. Our results show that pollen is more sensitive than phytoliths to changes within evergreen forest, but phytoliths are more sensitive than pollen to changes within dry forest. Both proxies were equally sensitive to changes within the savannahs. These are important considerations for palaeoecologists selecting proxies for the study of ecosystem turnover in the palaeo-record. Application of the thresholds to the palaeo-record demonstrated the utility of this quantitative approach for assessing the magnitude of vegetation change in the palaeo-record. This quantitative approach is therefore a useful tool to improve the identification of ecosystem turnover in the palaeo-record.
    Keywords data collection ; dry forests ; ecosystems ; evergreen forests ; Holocene epoch ; paleoecology ; phytoliths ; pollen ; quantitative analysis ; savannas ; uncertainty ; Amazonia ; Bolivia
    Language English
    Dates of publication 2019-11
    Size p. 1720-1730.
    Publishing place SAGE Publications
    Document type Article
    ZDB-ID 2027956-5
    ISSN 1477-0911 ; 0959-6836
    ISSN (online) 1477-0911
    ISSN 0959-6836
    DOI 10.1177/0959683619862021
    Database NAL-Catalogue (AGRICOLA)

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  4. Article: Paleoecological potential of phytoliths from lake sediment records from the tropical lowlands of Bolivia

    Plumpton, Heather J / Plumpton, Heather / Mayle, Francis M / Whitney, Bronwen S / Whitney, Bronwen

    Review of palaeobotany and palynology. 2020 Apr., v. 275

    2020  

    Abstract: Phytolith analysis is conventionally an archeo-botanical tool used to study past human activity using material from excavations or soil pits. However, phytolith analysis also has potential as a paleoecological tool, to reconstruct vegetation changes ... ...

    Abstract Phytolith analysis is conventionally an archeo-botanical tool used to study past human activity using material from excavations or soil pits. However, phytolith analysis also has potential as a paleoecological tool, to reconstruct vegetation changes through periods of climatic change and human influence. To study phytoliths from lake sediment alongside pollen requires an understanding of phytolith taphonomy in lakes. Theoretical models suggest phytoliths represent more local vegetation at smaller spatial scales than pollen from lake sediments, but this has not been tested empirically in the Neotropics. This paper compares pollen and phytolith assemblages from the same lake sediment surface sample, from a suite of lakes of different sizes across different vegetation types of lowland tropical Bolivia. We find three factors driving phytolith composition in lakes: taphonomy, lake size and phytolith productivity. By comparing phytolith assemblages with pollen assemblages, we find that they provide different taxonomic information and generally complement each other as paleo-vegetation proxies. We also demonstrate empirically that pollen assemblages in lake samples represent a larger catchment area than phytolith assemblages. Our findings suggest that phytoliths can be particularly useful in providing local-scale vegetation histories from large lakes, to complement the regional-scale vegetation histories provided by pollen data.
    Keywords climate change ; humans ; lakes ; lowlands ; Neotropics ; paleoecology ; phytoliths ; pollen ; savannas ; sediments ; soil ; theoretical models ; understory ; watersheds ; Bolivia
    Language English
    Dates of publication 2020-04
    Publishing place Elsevier B.V.
    Document type Article
    ISSN 0034-6667
    DOI 10.1016/j.revpalbo.2019.104113
    Database NAL-Catalogue (AGRICOLA)

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  5. Article: Integrated palaeoecology and archaeology – a powerful approach for understanding pre-Columbian Amazonia

    Mayle, Francis E / Iriarte, José

    Journal of archaeological science. 2014 Nov., v. 51

    2014  

    Abstract: The old paradigm that Amazonia's tropical ecosystems prevented cultural development beyond small-scale shifting agricultural economies, that had little environmental impact, no longer holds true for much of Amazonia. A diversity of archaeological ... ...

    Abstract The old paradigm that Amazonia's tropical ecosystems prevented cultural development beyond small-scale shifting agricultural economies, that had little environmental impact, no longer holds true for much of Amazonia. A diversity of archaeological evidence, including terra preta soils, raised fields, causeways, large habitation mounds, geometric earthworks, and megalithic monuments, all point to considerable cultural complexity and environmental impacts. However, uncertainty remains over the chronology of these cultures, their diet and economy, and the scale of environmental impact and land use associated with them. Here, we argue that a cross-disciplinary approach, closely coupling palaeoecology and archaeology, can potentially resolve these uncertainties. We show how, with careful site selection (pairing small and large lakes, close proximity to archaeological sites, transects of soil pits) and choice of techniques (e.g., pollen, phytoliths, starch grains, charcoal, stable isotopes), these two disciplines can be successfully integrated to provide a powerful tool for investigating the relationship between pre-Columbian cultures and their environment.
    Keywords agricultural economics ; archaeology ; charcoal ; diet ; ecosystems ; environmental impact ; geometry ; lakes ; land use ; monuments ; paleoecology ; phytoliths ; pollen ; stable isotopes ; starch granules ; terra preta ; uncertainty ; Amazonia
    Language English
    Dates of publication 2014-11
    Size p. 54-64.
    Publishing place Elsevier Ltd
    Document type Article
    ZDB-ID 1468969-8
    ISSN 0305-4403
    ISSN 0305-4403
    DOI 10.1016/j.jas.2012.08.038
    Database NAL-Catalogue (AGRICOLA)

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  6. Article: Insights into past land-use and vegetation change in the Llanos de Moxos (Bolivia) using fungal non-pollen palynomorphs

    Loughlin, Nicholas J.D / Mayle, Francis E / Nuñez Otaño, Noelia B / O'Keefe, Jennifer M.K / Duncan, Neil A / Walker, John H / Whitney, Bronwen S

    Journal of archaeological science. 2021 June, v. 130

    2021  

    Abstract: Here we document a 1000-year fungal record from the raised-field region of the Llanos de Moxos, a seasonally inundated forest-savanna mosaic in the Bolivian Amazon. Fungi are extremely sensitive to changes in vegetation due to their close relationship ... ...

    Abstract Here we document a 1000-year fungal record from the raised-field region of the Llanos de Moxos, a seasonally inundated forest-savanna mosaic in the Bolivian Amazon. Fungi are extremely sensitive to changes in vegetation due to their close relationship with the local environment, providing a useful proxy for past local vegetation and land-use change. Here the remains of fungal non-pollen palynomorphs (NPPs) are identified from a sediment core taken from Laguna El Cerrito. A multivariate constrained ordination is used to extract relationships between the fungal NPP types and environmental gradients, specifically, tree cover, near-shore vegetation, crop cultivation, burning and local sediment input. NPP types such as Neurospora cf. cerealis are identified as indicative of pre-European agriculture and offer the ability to expand on the temporal range of cultivation in the raised-field region. Constrained cluster analysis indicates that the most significant changes in the NPP assemblage occurs c. 1500 and c. 1700 CE, corresponding to the arrival of Europeans to the Americas and Jesuit missionaries to the Llanos de Moxos respectively. The modern savanna landscape is one shaped by changes in land-use and the introduction of cattle following the European Encounter.
    Keywords Neurospora ; archaeology ; cattle ; cluster analysis ; fungi ; land use change ; landscapes ; ordination techniques ; savannas ; sediments ; trees ; Amazonia ; Bolivia
    Language English
    Dates of publication 2021-06
    Publishing place Elsevier Ltd
    Document type Article
    Note NAL-AP-2-clean
    ZDB-ID 1468969-8
    ISSN 0305-4403
    ISSN 0305-4403
    DOI 10.1016/j.jas.2021.105382
    Database NAL-Catalogue (AGRICOLA)

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  7. Article ; Online: Cold spot microrefugia hold the key to survival for Brazil's Critically Endangered Araucaria tree.

    Wilson, Oliver J / Walters, Richard J / Mayle, Francis E / Lingner, Débora V / Vibrans, Alexander C

    Global change biology

    2019  Volume 25, Issue 12, Page(s) 4339–4351

    Abstract: Brazil's Araucaria tree (Araucaria angustifolia) is an iconic living fossil and a defining element of the Atlantic Forest global biodiversity hotspot. But despite more than two millennia as a cultural icon in southern Brazil, Araucaria is on the brink of ...

    Abstract Brazil's Araucaria tree (Araucaria angustifolia) is an iconic living fossil and a defining element of the Atlantic Forest global biodiversity hotspot. But despite more than two millennia as a cultural icon in southern Brazil, Araucaria is on the brink of extinction, having lost 97% of its extent to 20th-century logging. Although logging is now illegal, 21st-century climate change constitutes a new-but so far unevaluated-threat to Araucaria's future survival. We use a robust ensemble modelling approach, using recently developed climate data, high-resolution topography and fine-scale vegetation maps, to predict the species' response to climate change and its implications for conservation on meso- and microclimate scales. We show that climate-only models predict the total disappearance of Araucaria's most suitable habitat by 2070, but incorporating topographic effects allows potential highland microrefugia to be identified. The legacy of 20th-century destruction is evident-more than a third of these likely holdouts have already lost their natural vegetation-and 21st-century climate change will leave just 3.5% of remnant forest and 28.4% of highland grasslands suitable for Araucaria. Existing protected areas cover only 2.5% of the surviving microrefugia for this culturally important species, and none occur in any designated indigenous territory. Our results suggest that anthropogenic climate change is likely to commit Araucaria to a second consecutive century of significant losses, but targeted interventions could help ensure its survival in the wild.
    MeSH term(s) Biodiversity ; Brazil ; Climate Change ; Conservation of Natural Resources ; Forests ; Trees
    Language English
    Publishing date 2019-08-10
    Publishing country England
    Document type Journal Article
    ZDB-ID 1281439-8
    ISSN 1365-2486 ; 1354-1013
    ISSN (online) 1365-2486
    ISSN 1354-1013
    DOI 10.1111/gcb.14755
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article: Cold spot microrefugia hold the key to survival for Brazil's Critically Endangered Araucaria tree

    Wilson, Oliver J / Walters, Richard J / Mayle, Francis E / Lingner, Débora V / Vibrans, Alexander C

    Global change biology. 2019 Dec., v. 25, no. 12

    2019  

    Abstract: Brazil's Araucaria tree (Araucaria angustifolia) is an iconic living fossil and a defining element of the Atlantic Forest global biodiversity hotspot. But despite more than two millennia as a cultural icon in southern Brazil, Araucaria is on the brink of ...

    Abstract Brazil's Araucaria tree (Araucaria angustifolia) is an iconic living fossil and a defining element of the Atlantic Forest global biodiversity hotspot. But despite more than two millennia as a cultural icon in southern Brazil, Araucaria is on the brink of extinction, having lost 97% of its extent to 20th‐century logging. Although logging is now illegal, 21st‐century climate change constitutes a new—but so far unevaluated—threat to Araucaria's future survival. We use a robust ensemble modelling approach, using recently developed climate data, high‐resolution topography and fine‐scale vegetation maps, to predict the species' response to climate change and its implications for conservation on meso‐ and microclimate scales. We show that climate‐only models predict the total disappearance of Araucaria's most suitable habitat by 2070, but incorporating topographic effects allows potential highland microrefugia to be identified. The legacy of 20th‐century destruction is evident—more than a third of these likely holdouts have already lost their natural vegetation—and 21st‐century climate change will leave just 3.5% of remnant forest and 28.4% of highland grasslands suitable for Araucaria. Existing protected areas cover only 2.5% of the surviving microrefugia for this culturally important species, and none occur in any designated indigenous territory. Our results suggest that anthropogenic climate change is likely to commit Araucaria to a second consecutive century of significant losses, but targeted interventions could help ensure its survival in the wild.
    Keywords Araucaria angustifolia ; biodiversity ; climate change ; cold ; conservation areas ; endangered species ; extinction ; forests ; grasslands ; habitats ; logging ; meteorological data ; microclimate ; models ; topography ; trees ; vegetation maps ; Brazil
    Language English
    Dates of publication 2019-12
    Size p. 4339-4351.
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note JOURNAL ARTICLE
    ZDB-ID 1281439-8
    ISSN 1365-2486 ; 1354-1013
    ISSN (online) 1365-2486
    ISSN 1354-1013
    DOI 10.1111/gcb.14755
    Database NAL-Catalogue (AGRICOLA)

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  9. Article: Constraining pollen-based estimates of forest cover in the Amazon: A simulation approach

    Whitney, Bronwen S / Smallman, T Luke / Mitchard, Edward TA / Carson, John F / Mayle, Francis E / Bunting, M Jane

    Holocene. 2019 Feb., v. 29, no. 2

    2019  

    Abstract: Pollen dispersal and deposition (PDD) modelling has been instrumental in reconstructing historical vegetation in temperate regions, but its application has been limited in the tropics where there is greatest uncertainty in past land cover change. Here, ... ...

    Abstract Pollen dispersal and deposition (PDD) modelling has been instrumental in reconstructing historical vegetation in temperate regions, but its application has been limited in the tropics where there is greatest uncertainty in past land cover change. Here, we apply PDD modelling to Amazonian savanna and forested ecosystems. Empirical pollen data from lakes situated in southwestern Amazonia were used to calibrate the PDD model for a two-component landscape of forest and non-forest. The PDD model was then used to simulate pollen assemblages for different combinations of landscape arrangements (the multiple scenario approach) that reflect possible anthropogenic and climate-driven forest cover change in the late-Holocene. We show that pollen records from large Amazonian lakes vary greatly in their sensitivity to forest loss depending on the baseline forest cover. Lakes in landscapes containing >80% forest will detect small reductions (5% of total cover), but this sensitivity degrades rapidly with forest cover loss. There are a wide range of uncertainties in pollen reconstructions from mosaic and ecotonal landscapes. In forest-savanna mosaics, large reductions of forest cover could be undetectable through the pollen record. In ecotonal landscapes, the relationship between forest cover and its representation in the pollen record rapidly weakens with increasing distance from the forest boundary. Further application of PDD modelling in combination with the multiple scenario approach can address the uncertainties in pollen-based reconstructions of past land cover in the tropics, but require further investment and development.
    Keywords ecosystems ; forests ; lakes ; land cover ; landscapes ; models ; pollen ; pollen flow ; savannas ; temperate zones ; tropics ; uncertainty ; Amazonia
    Language English
    Dates of publication 2019-02
    Size p. 262-270.
    Publishing place SAGE Publications
    Document type Article
    ZDB-ID 2027956-5
    ISSN 1477-0911 ; 0959-6836
    ISSN (online) 1477-0911
    ISSN 0959-6836
    DOI 10.1177/0959683618810394
    Database NAL-Catalogue (AGRICOLA)

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  10. Article: Modelling the distribution of Amazonian tree species in response to long‐term climate change during the Mid‐Late Holocene

    Gomes, Vitor H. F / Mayle, Francis E / Gosling, William D / Vieira, Ima C. G / Salomão, Rafael P / ter Steege, Hans

    Journal of biogeography. 2020 July, v. 47, no. 7

    2020  

    Abstract: AIM: To (a) assess the environmental suitability for rainforest tree species of Moraceae and Urticaceae across Amazonia during the Mid‐Late Holocene and (b) determine the extent to which their distributions increased in response to long‐term climate ... ...

    Abstract AIM: To (a) assess the environmental suitability for rainforest tree species of Moraceae and Urticaceae across Amazonia during the Mid‐Late Holocene and (b) determine the extent to which their distributions increased in response to long‐term climate change over this period. LOCATION: Amazonia. TAXON: Tree species of Moraceae and Urticaceae. METHODS: We used MaxEnt and inverse distance weighting interpolation to produce environmental suitability and relative abundance models at 0.5‐degree resolution for tree species of Moraceae and Urticaceae, based on natural history collections and a large plot dataset. To test the response of the Amazon rainforest to long‐term climate change, we quantified the increase in environmental suitability and modelled species richness for both families since the Mid‐Holocene (past 6,000 years). To test the correlation between the relative abundance of these species in modern vegetation versus modern pollen assemblages, we analysed the surface pollen spectra from 46 previously published paleoecological sites. RESULTS: We found that the mean environmental suitability in Amazonia for species of Moraceae and Urticaceae showed a slight increase (6.5%) over the past 6,000 years, although southern ecotonal Amazonia and the Guiana Shield showed much higher increases (up to 68%). The accompanied modelled mean species richness increased by as much as 120% throughout Amazonia. The mean relative abundance of Moraceae and Urticaceae correlated significantly with the modern pollen assemblages for these families. MAIN CONCLUSIONS: Increasing precipitation between the Mid‐ and Late Holocene expanded suitable environmental conditions for Amazonian humid rainforest tree species of Moraceae and Urticaceae, leading to rainforest expansion in ecotonal areas of Amazonia, consistent with previously published fossil pollen data.
    Keywords Holocene epoch ; Moraceae ; Urticaceae ; biogeography ; climate change ; data collection ; natural history ; palynology ; pollen ; rain forests ; species richness ; trees ; Amazonia
    Language English
    Dates of publication 2020-07
    Size p. 1530-1540.
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note NAL-AP-2-clean ; JOURNAL ARTICLE
    ZDB-ID 188963-1
    ISSN 0305-0270
    ISSN 0305-0270
    DOI 10.1111/jbi.13833
    Database NAL-Catalogue (AGRICOLA)

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