| 1. |
- Abraham, Vojtech, et al.
(författare)
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Patterns in recent and Holocene pollen accumulation rates across Europe - the Pollen Monitoring Programme Database as a tool for vegetation reconstruction
- 2021
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 18:15, s. 4511-4534
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Tidskriftsartikel (refereegranskat)abstract
- The collection of modern, spatially extensive pollen data is important for the interpretation of fossil pollen assemblages and the reconstruction of past vegetation communities in space and time. Modern datasets are readily available for percentage data but lacking for pollen accumulation rates (PARs). Filling this gap has been the motivation of the pollen monitoring network, whose contributors monitored pollen deposition in modified Tauber traps for several years or decades across Europe. Here we present this monitoring dataset consisting of 351 trap locations with a total of 2742 annual samples covering the period from 1981 to 2017. This dataset shows that total PAR is influenced by forest cover and climate parameters, which determine pollen productivity and correlate with latitude. Treeless vegetation produced PAR values of at least 140 grains cm(-2) yr(-1). Tree PAR increased by at least 400 grains cm(-2) yr(-1) with each 10% increase in forest cover. Pollen traps situated beyond 200 km of the distribution of a given tree species still collect occasional pollen grains of that species. The threshold of this long-distance transport differs for individual species and is generally below 60 grains cm(-2) yr(-1). Comparisons between modern and fossil PAR from the same regions show similar values. For temperate taxa, modern analogues for fossil PARs are generally found downslope or southward of the fossil sites. While we do not find modern situations comparable to fossil PAR values of some taxa (e.g. Corylus), CO2 fertilization and land use may cause high modern PARs that are not documented in the fossil record. The modern data are now publicly available in the Neotoma Paleoecology Database and aid interpretations of fossil PAR data.
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| 2. |
- Githumbi, Esther, et al.
(författare)
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European pollen-based REVEALS land-cover reconstructions for the Holocene : Methodology, mapping and potentials
- 2022
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Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3508 .- 1866-3516. ; 14:4, s. 1581-1619
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Tidskriftsartikel (refereegranskat)abstract
- Quantitative reconstructions of past land cover are necessary to determine the processes involved in climate-human-land-cover interactions. We present the first temporally continuous and most spatially extensive pollen-based land-cover reconstruction for Europe over the Holocene (last 11g€¯700g€¯calg€¯yrg€¯BP). We describe how vegetation cover has been quantified from pollen records at a 11 spatial scale using the "Regional Estimates of VEgetation Abundance from Large Sites"(REVEALS) model. REVEALS calculates estimates of past regional vegetation cover in proportions or percentages. REVEALS has been applied to 1128 pollen records across Europe and part of the eastern Mediterranean-Black Sea-Caspian corridor (30-75° N, 25° W-50° E) to reconstruct the percentage cover of 31 plant taxa assigned to 12 plant functional types (PFTs) and 3 land-cover types (LCTs). A new synthesis of relative pollen productivities (RPPs) for European plant taxa was performed for this reconstruction. It includes multiple RPP values (≥2 values) for 39 taxa and single values for 15 taxa (total of 54 taxa). To illustrate this, we present distribution maps for five taxa (Calluna vulgaris, Cerealia type (t)., Picea abies, deciduous Quercus t. and evergreen Quercus t.) and three land-cover types (open land, OL; evergreen trees, ETs; and summer-green trees, STs) for eight selected time windows. The reliability of the REVEALS reconstructions and issues related to the interpretation of the results in terms of landscape openness and human-induced vegetation change are discussed. This is followed by a review of the current use of this reconstruction and its future potential utility and development. REVEALS data quality are primarily determined by pollen count data (pollen count and sample, pollen identification, and chronology) and site type and number (lake or bog, large or small, one site vs. multiple sites) used for REVEALS analysis (for each grid cell). A large number of sites with high-quality pollen count data will produce more reliable land-cover estimates with lower standard errors compared to a low number of sites with lower-quality pollen count data. The REVEALS data presented here can be downloaded from https://doi.org/10.1594/PANGAEA.937075 (Fyfe et al., 2022).
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| 3. |
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| 4. |
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| 5. |
- Tonkov, Spassimir, et al.
(författare)
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A 30,000-year pollen record from Mire Kupena, Western Rhodopes Mountains (south Bulgaria)
- 2014
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Ingår i: Review of Palaeobotany and Palynology. - : Elsevier BV. - 0034-6667 .- 1879-0615. ; 209, s. 41-51
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Tidskriftsartikel (refereegranskat)abstract
- A palynological study was performed on a 2 m thick sediment sequence recovered from Mire Kupena (1356 m), a former lake in the Western Rhodopes Mountains (south Bulgaria) and supported by radiocarbon dating. The record extends back to ca. 30,000 cal. yrs. BP (Middle Pleniglacial) when the study area was occupied by wooded steppe composed of Pinus sp., Pinus peuce, some Betula,Juniperus, and cold-tolerant herb vegetation dominated by Artemisia and Chenopodiaceae. In addition, the almost continuous presence of deciduous Quercus, Tilia, Corylus, Abies, Picea, Fagus, Alnus, and Carpinus betulus pollen suggests interstadial conditions and this area could be recognized as a montane refugial place. A reconstruction of the interval between ca. 24,000 and 15,000 cal. yrs. BP was not possible due to an extremely low sediment accumulation rates or, more likely, a hiatus. The lateglacial landscape was dominated by mountain-herb steppe vegetation with isolated stands of Pinus, Betula and shrubland of Juniperus. The afforestation in the Early Holocene started with broad-leaved forests composed of Quercus with C betulus, Carpinus orientalis/Ostrya, Ulmus, Tilia and Corylus and minor amounts of Pinus, Betula and Abies. In the Late Holocene (< ca. 4700 cal. yrs. BP) Fagus began to gain importance chiefly at the expense of the mixed oak forests, while after ca. 2000 cal. yrs. BP forests of Pinus sylyestris with some P. peuce quickly expanded around the mire. A comparison with other long palynological records from the mountains and lowlands of Bulgaria and in northern Greece reveals not only common trends in the vegetation development that are a reflection of the climate changes, but also site-specific features related to the location and topography of each site.
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| 6. |
- Tonkov, Spassimir, et al.
(författare)
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A contribution to the postglacial vegetation history of the Rila Mountains, Bulgaria : The pollen record of Lake Trilistnika
- 2008
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Ingår i: Quaternary International. - : Elsevier BV. - 1040-6182 .- 1873-4553. ; 190:1, s. 58-70
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Tidskriftsartikel (refereegranskat)abstract
- Pollen analysis of sediments from the glacial Lake Trilistnika (2216 m) in the Northwestern Rila Mountains (Bulgaria), supplemented by 13 radiocarbon dates, allowed the reconstruction of the palaeoenvironment and vegetation history in postglacial time. The exact time of the cirque glacier retreat is still under discussion but the lake was free of ice before 15,000 cal. BP. when sedimentation of gray silt began. The lateglacial vegetation, composed of Artemisia, Chenopodiaceae and Poaceae, with isolated stands of Pinus and Juniperus-Ephedra shrubland, dominated during the stadials and partly retreated during the Bolling/Allerod interstadial complex. The afforestation in the early Holocene (11,500-7800 cal. BP) started with the distribution of pioneer Benda forests with groups of Pinus (P. mugo, P. sylvestris and P. peuce) at mid-high altitudes, and Quercus forests with Tilia, Ulmus, Fraxinus, Corylus below the birch zone. The change to more humid and cooler climate ca. 7800-7500 cal. BP favored the vertical migration of Abies, P. sylvestris and P. peuce. The establishment of Fagus sylvatica took place after 5200 cal. BP, when pure or mixed beech communities were formed. The last tree which invaded the coniferous belt between 4300 and 3400 cal. BP was Picea abies. The first expansion maximum of spruce was recorded after ca. 2700 cal. BP. The vegetation development in historical times was also influenced by human interference, indicated by the continuous presence of pollen anthropogenic indicators Such as Triticum, Secale, Hordeum, Plantago lanceolata, Rumex, Scleranthus, Juniperus.
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| 7. |
- Tonkov, Spassimir, et al.
(författare)
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Lateglacial to Holocene vegetation development in the Central Rila Mountains, Bulgaria
- 2016
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 26:1, s. 17-28
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Tidskriftsartikel (refereegranskat)abstract
- The vegetation history of the Central Rila Mountains for the last 14,000years was reconstructed by means of pollen analysis and radiocarbon chronology of a core retrieved from Lake Manastirsko-2 (2326m). The Lateglacial landscape was dominated by open herb vegetation composed of Artemisia, Chenopodiaceae, Poaceae, and other cold-resistant herbs (14,000-11,700 cal. yr BP). Stands of Pinus, Betula, and Juniperus-Ephedra shrubland partly enlarged during the Lateglacial interstadial. Pioneer forests of Betula with Pinus and Juniperus occupied barren soils in the early Holocene (11,700-7900 cal. yr BP), while mixed oak forests with Tilia, Ulmus, Acer, and later on Corylus spread at lower elevations. A coniferous forest belt with Pinus sylvestris, Pinus peuce, and Abies developed after 7900 cal. yr BP in the conditions of milder winters, cooler summers, and increase in precipitation. The late Holocene dynamic vegetation changes were associated with the invasion of Picea abies after 3400 cal. yr BP, while Fagus communities slightly enlarged in the river valleys. Indications of human activities are visible in the pollen diagram since the Late Bronze Age' (3400-3200 cal. yr BP). The vegetation development in the study area followed a similar pattern when compared with palynological and macrofossil records from other parts of the Rila and the adjacent Northern Pirin Mountains. On a larger geographical scale, the postglacial vegetation history of the Rila Mountains displays common features with sites in the Romanian Carpathians, whereas the differences observed are result of the location of tree refugia, competing abilities, climate changes, and human activities.
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| 8. |
- Tonkov, Spassimir, et al.
(författare)
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On the Holocene vegetation history of the Central Rila Mountains, Bulgaria : The palaeoecological record of peat bog Vodniza (2113 m)
- 2018
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Ingår i: Review of Palaeobotany and Palynology. - : ELSEVIER SCIENCE BV. - 0034-6667 .- 1879-0615. ; 250, s. 16-26
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Tidskriftsartikel (refereegranskat)abstract
- Information on the Holocene vegetation history of the Central Rila Mountains for the last 10,000 years was obtained by means of pollen and fossil stomata analyses of a 500 cm core retrieved from peat bog Vodniza (2113 ma.s.l.), and supported by radiocarbon chronology. The early Holocene afforestation started with an initial Betula phase with stands of Juniperus and Pinus which occupied barren soils (10,000-8300 cal. yrs. BP) while deciduous oak forests with abundant Tilia, Ulmus, Acer, and later on Corylus, spread at lower elevations. During the Holocene climatic optimum (8300-6000 cal. yrs. BP) the conifers Pious (Pious sylvestris, Pinus mugo, Pinus peuce) and Abies expanded at the expense of the birch and oak forests. The tree line was running above 2100 m comparable to the present-day situation and started to descend after ca. 3200 cal. yrs. BP mostly due to human impact. The last tree which penetrated into the coniferous belt after 3400 cal. yrs. BP and reached altitudes of 2000-2100 m, confirmed by the find of fossil stomata, was Picea abies. Its maximal distribution was achieved between 2250 and 1100 cal. yrs. BP, alongside with some enlargement of beech communities. The first indications of stockbreeding and other human activities in the Central Rila Mountains were recorded since 3400-3200 cal. yrs. BP (Late Bronze Age). The vegetation reconstruction during the Holocene followed a pattern coherent with the information from the Northern Pirin and partly from the Western Rhodopes Mountains. The palaeoecological evidence from the Rila Mountains could be compared in broad lines with the high quality data obtained from the Romanian Carpathians by the application of multi-proxy research approach.
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| 9. |
- Tonkov, Spassimir, et al.
(författare)
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Postglacial vegetation history as recorded from the subalpine Lake Ribno (NW Rila Mts), Bulgaria
- 2013
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Ingår i: Central European Journal of Biology. - : Walter de Gruyter GmbH. - 1895-104X .- 1644-3632. ; 8:1, s. 64-77
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Tidskriftsartikel (refereegranskat)abstract
- A pollen analysis conducted on a 600 cm core from Lake Ribno (2184 m) in the Northwestern Rila Mountains, supplemented by 13 radiocarbon dates, has revealed the basic stages in its postglacial vegetation dynamics. The lateglacial vegetation, composed of Artemisia, Chenopodiaceae and Poaceae, with stands of Pinus and Juniperus-Ephedra shrubland, dominated in the stadials and partly retreated during the Bolling/Allerod interstadial (14700-12900 cal. yrs. BP). The afforestation in the early Holocene (11600-7800 cal. yrs. BP) started with pioneer Betula forests, with groups of Pinus and Juniperus at mid-high altitudes, and Quercus forests with Tilia, Ulmus, Fraxinus, Corylus below the birch zone. A coniferous belt composed of Pinus sylvestris, P. peuce and Abies was shaped under the conditions of a more humid climate (7800-5800 cal. yrs. BP). The last trees that invaded the study area were Fagus after 4300 cal. yrs. BP and Picea abies after 3400 cal. yrs. BP. Evidence for destructive changes in the vegetation and indications of agricultural and stock-breeding activities (pollen of Triticum, Secale, Plantago lanceolata, Rumex, Juglans) was continuously recorded since the Late Bronze Age (3400-3200 cal. yrs. BP). The postglacial vegetation history in the Northwestern Rila Mountains demonstrated close similarities with that of the Northern Pirin Mountains.
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| 10. |
- Tonkov, Spassimir, et al.
(författare)
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The Lateglacial in the Rila Mountains (Bulgaria) revisited : The pollen record of Lake Ribno (2184m)
- 2011
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Ingår i: Review of Palaeobotany and Palynology. - : Elsevier BV. - 0034-6667 .- 1879-0615. ; 166:1-2, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Pollen analysis and AMS radiocarbon dating were conducted on the lateglacial sediments (175 cm in thickness) of a core obtained from the glacial Lake Ribno (2184 m) in the northwestern Rila Mountains. The vegetation dynamics at high-mid altitudes based on important changes in palynostratigraphy as a response to the lateglacial climate fluctuations for the time interval 16000-11600 cal.yrs BP is bound to an interstadial/stadial cycle, analogous with the Bolling/Allerod-Younger Dryas. The established local chronology demonstrates also good correlation with the isotopic signal from Greenland ice-cores. The reconstruction of the lateglacial vegetation shows common features with other sites from the Bulgarian mountains (Rila, Pirin, Western Rhodopes) and the glacial lakes in the southern Romanian Carpathians (Retezat Mountains).
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