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- Fracasso, Ilaria, et al.
(författare)
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Exploring different methodological approaches to unlock paleobiodiversity in peat profiles using ancient DNA
- 2024
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Ingår i: Science of the Total Environment. - 0048-9697. ; 908
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Tidskriftsartikel (refereegranskat)abstract
- Natural and human-induced environmental changes deeply affected terrestrial ecosystems throughout the Holocene. Paleoenvironmental reconstructions provide information about the past and allow us to predict/model future scenarios. Among potential records, peat bogs are widely used because they present a precise stratigraphy and act as natural archives of highly diverse organic remains. Over the decades, several techniques have been developed to identify debris occurring in peat, including their morphological description. However, this is strongly constrained by the researcher's ability to distinguish residues at the species level, which typically requires many years of experience. In addition, potential contamination hampers using these techniques to obtain information from organisms such as fungi or bacteria. Environmental DNA metabarcoding and shotgun metagenome sequencing could represent a solution to detect specific groups of organisms without any a priori knowledge of their characteristics and/or to identify organisms that have rarely been considered in previous investigations. Moreover, shotgun metagenomics may allow the identification of bacteria and fungi (including both yeast and filamentous life forms), ensuring discrimination between ancient and modern organisms through the study of deamination/damage patterns. In the present review, we aim to i) present the state-of-the-art methodologies in paleoecological and paleoclimatic studies focusing on peat core analyses, proposing alternative approaches to the classical morphological identification of plant residues, and ii) suggest biomolecular approaches that will allow the use of proxies such as invertebrates, fungi, and bacteria, which are rarely employed in paleoenvironmental reconstructions.
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| 2. |
- Hamard, Samuel, et al.
(författare)
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Contribution of microbial photosynthesis to peatland carbon uptake along a latitudinal gradient
- 2021
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Ingår i: Journal of Ecology. - : British Ecological Society. - 0022-0477 .- 1365-2745. ; 109:9, s. 3424-3441
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Tidskriftsartikel (refereegranskat)abstract
- Phototrophic microbes, also known as micro-algae, display a high abundance in many terrestrial surface soils. They contribute to atmospheric carbon dioxide fluxes through their photosynthesis, and thus regulate climate similar to plants. However, microbial photosynthesis remains overlooked in most terrestrial ecosystems. Here, we hypothesise that phototrophic microbes significantly contribute to peatland C uptake, unless environmental conditions limit their development and their photosynthetic activity. To test our hypothesis, we studied phototrophic microbial communities in five peatlands distributed along a latitudinal gradient in Europe. By means of metabarcoding, microscopy and cytometry analyses, as well as measures of photosynthesis, we investigated the diversity, absolute abundance and photosynthetic rates of the phototrophic microbial communities. We identified 351 photosynthetic prokaryotic and eukaryotic operational taxonomic units (OTUs) across the five peatlands. We found that water availability and plant composition were important determinants of the composition and the structure of phototrophic microbial communities. Despite environmental shifts in community structure and composition, we showed that microbial C fixation rates remained similar along the latitudinal gradient. Our results further revealed that phototrophic microbes accounted for approximately 10% of peatland C uptake. Synthesis. Our findings show that phototrophic microbes are extremely diverse and abundant in peatlands. While species turnover with environmental conditions, microbial photosynthesis similarly contributed to peatland C uptake at all latitudes. We estimate that phototrophic microbes take up around 75 MT CO2 per year in northern peatlands. This amount roughly equals the magnitude of projected peatland C loss due to climate warming and highlights the importance of phototrophic microbes for the peatland C cycle.
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| 3. |
- Marquer, Laurent, et al.
(författare)
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Pollen-based reconstruction of Holocene land-cover in mountain regions : Evaluation of the Landscape Reconstruction Algorithm in the Vicdessos valley, northern Pyrenees, France
- 2020
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Ingår i: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 228, s. 1-15
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Forskningsöversikt (refereegranskat)abstract
- Long-term perspectives on climate- and human-induced shifts in plant communities and tree line in mountains are often inferred from fossil pollen records. However, various factors, such as complex patterns of orographic wind fields and abundant insect-pollinated plants in higher altitudes, make pollen-based reconstruction in mountain regions difficult. Over the last decade the Landscape Reconstruction Algorithm (LRA) - a model-based approach in reconstruction of vegetation - has been successfully applied in various parts of the globe. However, evaluation of its effectiveness in mountain ranges is still limited. The present study assesses the extent to which the LRA approach helps quantify the local changes in vegetation cover at Vicdessos valley in northern French Pyrenees as a case study. In the study area well-dated sediment cores are available from eight bogs and ponds, 6-113 m in radius, located above the current tree line. We first use a simple simulation experiment to evaluate the way how pollen records from "landscape islands" (mountain tops and plateaus) would represent local vegetation and to clarify important factors affecting the LRA-based reconstruction in a mountainous region. This study then uses pollen records from these sites and vegetation and land-cover data both within a 50-km radius around the Vicdessos valley and within a 2-km radius from each site for evaluation of the REVEALS- and LOVE-based reconstruction of the regional and local plant cover, respectively, in the LRA approach. The land-cover data are complied for coniferous trees, broadleaved trees and non-forested areas from the CORINE and historical maps in three time windows: 1960-1970, 1990-2000 and 2000-2013. Major findings are as follows. (1) Accuracy of the regional vegetation estimates affects the reliability of the LRA-based reconstruction of vegetation within a 2-km radius; use of the CORINE data as input to the LOVE model improves reliability of the results over the use of the REVEALS-based estimates of regional vegetation. This implies that a systematic selection of pollen data only from sites above the tree line is problematic for estimating regional vegetation, and thus the entire LRA process. (2) Selection of the dispersal models for pollen transport (i.e. the Langrangian Stochastic Model vs. Gaussian Plume Model) does not affect significantly the LRA-based estimates at both the regional and local scales in the study area. (3) The LRA approach improves the pollen-based reconstruction of local vegetation compared to pollen percentage alone in northern Pyrenees. Although further empirical and simulation studies are necessary, our results emphasize the importance of site selection for the LRA-based reconstruction of vegetation in mountain regions. (C) 2019 Elsevier Ltd. All rights reserved.
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