MARCO POLO – A new and simple tool for pollen-based stand-scale vegetation reconstruction

Hitherto, the Landscape Reconstruction Algorithm (LRA) has been the only truly quantitative approach to stand-scale palynology. However, the LRA requires information on pollen productivity and dispersal, which is not always available. The alternative approach MARCO POLO (MAnipulating pollen sums to ReCOnstruct POllen of Local Origin) presented here is solely based on pollen values and does not rely on a pollen dispersal function. In a stepwise fashion, MARCO POLO removes those pollen types from the pollen sum whose values are significantly higher than in a neighbouring large basin. The resulting regional pollen sum is free of the disturbing factor of (extra-)local pollen. Based on this sum, comparison with the pollen record from the large basin allows calculating sharp (extra-)local signals. Treating the (extra-)local pollen portion with representation factors ( R-values) then produces a quantitative reconstruction of the stand-scale vegetation composition. We tested MARCO POLO and the LRA on a dataset of pollen surface samples and forest vegetation relevés from northern Central Europe. Both approaches reconstruct the presence or absence of taxa at the stand scale within a small margin of error. Where observed cover was ⩾2%, both models always reconstructed presence, where modelled cover was ⩾2% the taxon was always present. Overall, both approaches perform well in reconstructing the cover of taxa within a 100-m radius. In our tests, MARCO POLO is slightly better at reconstructing cover values for more taxa. Although some model parameters evidently need revision, the simple correlative approach of MARCO POLO appears to perform at least as well as the complex LRA model.

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Long-term forest dynamics at Gribskov, eastern Denmark with early-Holocene evidence for thermophilous broadleaved tree species

The Holocene ◽

10.1177/0959683612455549 ◽

2012 ◽

Vol 23 (2) ◽

pp. 243-254 ◽

Cited By ~ 13

Author(s):

Mette Venås Overballe-Petersen ◽

Anne Birgitte Nielsen ◽

Gina E Hannon ◽

Karen Halsall ◽

Richard HW Bradshaw

Keyword(s):

Early Holocene ◽

Pollen Record ◽

Sediment Stratigraphy ◽

Pollen Types ◽

Broadleaved Tree Species ◽

Pollen Productivity ◽

Broadleaved Tree ◽

Disturbed Forest ◽

Small Forest

We report on a full-Holocene pollen, charcoal and macrofossil record from a small forest hollow in Gribskov, eastern Denmark. The Fagus sylvatica pollen record suggests the establishment of a small Fagus population at Gribskov in the early Holocene together with early establishment of other thermophilous broadleaved trees, including Quercus sp., Tilia sp. and Ulmus sp. The macrofossils contribute to the vegetation reconstruction with evidence for local presence of species with low pollen productivity or easily degraded pollen types such as Populus. The charcoal record shows frequent burning during two periods of the early Holocene and from c. 3000 cal. BP to present. The early-Holocene part of the record indicates a highly disturbed forest ecosystem with frequent fires and abundant macrofossils of particularly Betula sp. and Populus sp. The sediment stratigraphy and age–depth relationships give no clear indication of post-depositional disturbance, although a possible short-lived hiatus occurs around 6500 cal. BP. The early pollen record from thermophilous trees could indicate that there may have been some downwash following sediment desiccation through wood peat layers deposited between c. 6500 and 10,000 cal. BP, but the overall biostratigraphy is consistent with other Danish small hollow records.

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Quantitative land-cover change in West Africa over the Holocene: case study in Cameroon

10.5194/egusphere-egu2020-9054 ◽

2020 ◽

Author(s):

Esther Githumbi ◽

Marie-Jose Gaillard ◽

Anne-Marie Lezine ◽

Gaston Achoundong ◽

Christelle Hély ◽

...

Keyword(s):

Land Cover ◽

Land Cover Change ◽

Spatial Scales ◽

Reconstruction Algorithm ◽

Second Phase ◽

Climate Modelling ◽

The Past ◽

Landscape Reconstruction ◽

Pollen Productivity ◽

Pollen Records

Currently interaction between climate and land-cover change in the past across the globe, and whether drivers are anthropogenic or natural are among the biggest debates. The impacts of climate and land-cover change are having significant consequences on biodiversity and ecosystems. Wide ranging palaeoenvironmental methods have contributed to this debate by providing long-term records of both climate and land-cover change. This provide the context for evaluating the effect of land-cover change on climate.&#160; Inferred past land-cover and climate change from palaeoecological proxies therefore need to be quantified to provide reliable estimates of change; there are several methods of quantifying land-cover change in the past of which the Landscape Reconstruction Algorithm (LRA) &#160;can estimate past land-cover change quantitatively at both regional and local spatial scales using fossil pollen records. The LRA includes two models (REVEALS and LOVE) and has already been tested and validated in Europe, North America, and China.In this study, we apply the LRA on Holocene pollen records in Cameroon to estimate past land-cover change. This is the first pollen-based, quantitative land-cover reconstruction using LRA in Africa.&#160; It will provide a comparison with land-cover change described from raw pollen data and useful information for climate modelling. The first phase involved the estimation of relative pollen productivity (RPP) for 13 taxa using the pollen-vegetation relationship described by the ERV model. The second phase involves the application of LRA using the RPPs from the 13 taxa.&#160;&#160;Acknowledgements: We thank the French ANR (National Research Agency; projects C3A ANR-09-PEXT-001 and VULPES ANR-15-MASC-0003) and the Belgian project BR/132/A1/AFRIFORD for financial support, IRD (France) and the Ministry of Research and National Herbarium of Cameroon for research facilities and authorizations, and A. Vincens, J.-P. Cazet, G. Buchet, L. F&#233;vrier, and K. Lemonnier (CNRS) for laboratory and field assistance. The study is a contribution to PAGES LandCover6k (www.pastglobalchanges.org/ini/wg/landcover6k/intro).

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Relative pollen productivity estimates of savanna taxa from southern Africa and their application to reconstruct shrub encroachment during the last century

The Holocene ◽

10.1177/09596836211003193 ◽

2021 ◽

pp. 095968362110031

Author(s):

Ximena Tabares ◽

Gregor Ratzmann ◽

Stefan Kruse ◽

Martin Theuerkauf ◽

Benjamin Mapani ◽

...

Keyword(s):

Vegetation History ◽

Pollen Dispersal ◽

Quantitative Information ◽

Pollen Record ◽

Gaussian Plume Model ◽

Pollen Productivity ◽

Gaussian Plume ◽

R Value ◽

Dynamics Of Vegetation

To understand the resilience of African savannas to global change, quantitative information on the long-term dynamics of vegetation is required. Past dynamics can be reconstructed with the REVEALS model, which requires pollen productivity estimates (PPE) that are calibrated using surface pollen and vegetation data. Here we calculated PPE values for five savanna taxa using the extended R-value (ERV) model and two pollen dispersal options: the Gaussian plume model (GPM) and the Lagrangian stochastic model (LSM). The ERV calculations failed to produce a reliable PPE for Poaceae. We therefore used Combretaceae as the reference taxon – although values obtained with Poaceae as the reference taxon are presented in the supplement. Our results indicate that Combretaceae is the taxon with the highest pollen productivity and Grewia the taxon with the lowest productivity. Acacia and Dichrostachys are intermediate pollen producers. We find no clear indication of whether the GPM PPEs or the LSM PPEs are more realistic, but the differences between these values confirmed that the pollen fall speed has a greater effect in the modelling of GPM than in the LSM. We also applied REVEALS to the pollen record of Lake Otjikoto (northern Namibia) and obtained the first quantitative reconstruction of the last 130 years of vegetation history in the region. Cover estimates for Poaceae indicate the predominance of a semi-open landscape throughout the 20th century, while cover values below 50% since the 21st century correspond to a thick savanna. This change in grass cover is associated with the spread of Vachellia, Senegalia and Grewia reflecting an encroached state.

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Novel methods of estimating relative pollen productivity: A key parameter for reconstruction of past land cover from pollen records

Progress in Physical Geography Earth and Environment ◽

10.1177/0309133319861808 ◽

2019 ◽

Vol 43 (6) ◽

pp. 731-753 ◽

Cited By ~ 4

Author(s):

Yiman Fang ◽

Chunmei Ma ◽

M Jane Bunting

Keyword(s):

Land Cover ◽

Empirical Data ◽

Alternative Methods ◽

Model Parameters ◽

Value Analysis ◽

Pollen Productivity ◽

Tropical China ◽

The Relationship ◽

Pollen Records ◽

Key Parameter

Reconstructing land cover from pollen data using mathematical models of the relationship between them has the potential to translate the many thousand pollen records produced over the last 100 years (over 2300 radiocarbon-dated pollen records exist for the UK alone) into formats relevant to ecologists, archaeologists and climate scientists. However, the reliability of these reconstructions depends on model parameters. A key parameter is Relative Pollen Productivity (RPP), usually estimated from empirical data using ‘Extended R Value analysis’ (ERV analysis). Lack of RPP estimates for many regions is currently a major limitation on reconstructing global land cover. We present two alternatives to ERV analysis, the Modified Davis Method and an iteration method, which use the same underlying model of the relationship between pollen and vegetation to estimate RPP from empirical data, but with different assumptions. We test them in simulation against ERV analysis, and use a case study of a problematic empirical dataset to determine whether they have the potential to increase the speed and geographic range of RPP estimation. The two alternative methods are shown to perform at least as well as ERV analysis in simulation. We also present new RPP estimates from southeastern sub-tropical China for nine taxa estimated using the Modified Davis Method. Adding these two methods to the ‘toolkit’ for land cover reconstruction from pollen records opens up the possibility to estimate a key parameter from existing datasets with less field time than using current methods. This can both speed up the inclusion of more of the globe in past land cover mapping exercises such as the PAGES Landcover6k working group and improve our understanding of how this parameter varies within a single taxon and the factors control that variation.

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Comparison of settlement-era vegetation reconstructions for STEPPS and REVEALS pollen–vegetation models in the northeastern United States

Quaternary Research ◽

10.1017/qua.2019.81 ◽

2020 ◽

Vol 95 ◽

pp. 23-42 ◽

Cited By ~ 3

Author(s):

Mathias Trachsel ◽

Andria Dawson ◽

Christopher J. Paciorek ◽

John W. Williams ◽

Jason S. McLachlan ◽

...

Keyword(s):

United States ◽

Forest Dynamics ◽

Pollen Dispersal ◽

Parameter Estimates ◽

Vegetation Composition ◽

Northeastern United States ◽

Bayesian Hierarchical ◽

Pollen Productivity ◽

Vegetation Models ◽

Anthropogenic Land Use

AbstractReconstructions of prehistoric vegetation composition help establish natural baselines, variability, and trajectories of forest dynamics before and during the emergence of intensive anthropogenic land use. Pollen–vegetation models (PVMs) enable such reconstructions from fossil pollen assemblages using process-based representations of taxon-specific pollen production and dispersal. However, several PVMs and variants now exist, and the sensitivity of vegetation inferences to PVM selection, variant, and calibration domain is poorly understood. Here, we compare the reconstructions, parameter estimates, and structure of a Bayesian hierarchical PVM, STEPPS, both to observations and to REVEALS, a widely used PVM, for the pre–Euro-American settlement-era vegetation in the northeastern United States (NEUS). We also compare NEUS-based STEPPS parameter estimates to those for the upper midwestern United States (UMW). Both PVMs predict the observed macroscale patterns of vegetation composition in the NEUS; however, reconstructions of minor taxa are less accurate and predictions for some taxa differ between PVMs. These differences can be attributed to intermodel differences in structure and parameter estimates. Estimates of pollen productivity from STEPPS broadly agree with estimates produced for use in REVEALS, while comparison between pollen dispersal parameter estimates shows no significant relationship. STEPPS parameter estimates are similar between the UMW and NEUS, suggesting that STEPPS parameter estimates are transferable between floristically similar regions and scales.

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Phylogenetic assessment of pollen characters in Myrtaceae

Australian Systematic Botany ◽

10.1071/sb11019 ◽

2012 ◽

Vol 25 (3) ◽

pp. 171 ◽

Cited By ~ 9

Author(s):

Andrew H. Thornhill ◽

Michael D. Crisp

Keyword(s):

Internal Transcribed Spacer ◽

Morphological Characters ◽

Molecular Dating ◽

Fossil Pollen ◽

Pollen Record ◽

Plant Family ◽

Pollen Characters ◽

Pollen Types ◽

The Relationship ◽

Potential Use

Identifying synapomorphic morphological characters is needed to select and then accurately place fossils as calibrations on a phylogeny in molecular-dating analyses. The plant family Myrtaceae, with 130 genera and 5500 species, has nine different pollen types, whereas the fossil pollen record of Myrtaceae, represented by the genus Myrtaceidites, putatively extends back to the Cretaceous and also contains at least nine distinct morphospecies. To reveal potential links between extant and fossil pollen, we optimised pollen characters scored from a recent family-wide review of extant Myrtaceae pollen using scanning electron microscopy (SEM) onto a phylogeny of 111 taxa inferred from two chloroplast (matK and ndhF) and one nuclear (internal transcribed spacer, ITS) loci. Our findings indicate the potential use of colpus morphology in diagnosing pollen types in Myrtaceae, whereas the majority of character states of exine pattern, presence of apocolpial island and pollen width appear to be homoplasious. The results of the present study have implications for understanding the relationship between fossil morphospecies and extant Myrtaceae species, and their reliable choice in molecular dating.

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A Doubly Constrained TV Algorithm for Image Reconstruction

Mathematical Problems in Engineering ◽

10.1155/2020/5382106 ◽

2020 ◽

Vol 2020 ◽

pp. 1-15

Author(s):

Zhiwei Qiao ◽

Gage Redler ◽

Boris Epel ◽

Howard Halpern

Keyword(s):

Image Reconstruction ◽

Convergence Rate ◽

Simulated Data ◽

Reconstruction Algorithm ◽

Model Parameters ◽

Resonance Imaging ◽

Reconstruction Accuracy ◽

Paramagnetic Resonance ◽

Positron Emission ◽

Tv Model

Purpose. The total variation (TV) minimization algorithm is an effective image reconstruction algorithm capable of accurately reconstructing images from sparse and/or noisy data. The TV model consists of two terms: a data fidelity term and a TV regularization term. Two constrained TV models, data divergence-constrained TV minimization (DDcTV) and TV-constrained data divergence minimization (TVcDM), have been successfully applied to computed tomography (CT) and electron paramagnetic resonance imaging (EPRI). In this work, we propose a new constrained TV model, a doubly constrained TV (dcTV) model, which has the potential to further improve the reconstruction accuracy for the two terms which are both of constraint forms. Methods. We perform an inverse crime study to validate the model and its Chambolle-Pock (CP) solver and characterize the performance of the dcTV-CP algorithm in the context of CT. To demonstrate the superiority of the dcTV model, we compare the convergence rate and the reconstruction accuracy with the DDcTV and TVcDM models via simulated data. Results and Conclusions. The performance-characterizing study shows that the dcTV-CP algorithm is an accurate and convergent algorithm, with the model parameters impacting the reconstruction accuracy and the algorithm parameters impacting the convergence path and rate. The comparison studies show that the dcTV-CP algorithm has a relatively fast convergence rate and can achieve higher reconstruction accuracy from sparse projections or noisy projections relative to the other two single-constrained TV models. The knowledge and insights gained in the work may be utilized in the application of the new model in other imaging modalities including divergence-beam CT, magnetic resonance imaging (MRI), positron emission tomography (PET), and EPRI.

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