| 1. |
- Cui, Qiao-Yu, et al.
(author)
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A case study of the role of climate, humans, and ecological setting in Holocene fire history of northwestern Europe
- 2015
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In: Science China. Earth Sciences. - : Springer Science and Business Media LLC. - 1674-7313 .- 1869-1897. ; 58:2, s. 195-210
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Journal article (peer-reviewed)abstract
- We present the major results from studies of fire history over the last 11000 years (Holocene) in southern Sweden, on the basis of palaeoecological analyses of peat sequences from three small peat bogs. The main objective is to emphasize the value of multiple, continuous sedimentary records of macroscopic charcoal (macro-C) for the reconstruction of local to regional past changes in fire regimes, the importance of multi-proxy studies, and the advantage of model-based estimates of plant cover from pollen data to assess the role of tree composition and human impact in fire history. The chronologies at the three study sites are based on a large number of C-14 dates from terrestrial plant remains and age-depth models are achieved using Bayesian statistics. Fire history is inferred from continuous records of macro-C and microscopic charcoal counts on pollen slides. The Landscape Reconstruction Algorithm (LRA) for pollen-based quantitative reconstruction of local vegetation cover is applied on the three pollen records for plant cover reconstruction over the entire Holocene. The results are as follows: (1) the long-term trends in fire regimes are similar between sites, i.e., frequent fires during the early Holocene until ca. 9 ka BP, low fire frequency during the mid-Holocene, and higher fire frequency from ca. 2.5 ka BP; (2) this broad trend agrees with the overall fire history of northwestern and western Europe north of the Mediterranean area, and is due to climate forcing in the early and mid-Holocene, and to anthropogenic land-use in the late Holocene; (3) the LRA estimates of plant cover at the three sites demonstrate that the relative abundance of pine played a primordial role in the early and mid-Holocene fire history; and (4) the between-site differences in the charcoal records and inferred fire history are due to local factors (i.e., relative abundance of pine, geomorphological setting, and anthropogenic land-use) and taphonomy of charcoal deposition in the small peat bogs. It is shown that continuous macro-C records are most useful to disentangle local from regional-subcontinental fire history, and climate-induced from human-induced fire regimes, and that pollen-based LRA estimates of local plant cover are more adequate than pollen percentages for the assessment of the role of plant composition on fire history.
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| 2. |
- Cui, Qiao-Yu, et al.
(author)
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The role of tree composition in Holocene fire history of the hemiboreal and southern boreal zones of southern Sweden, as revealed by the application of the Landscape Reconstruction Algorithm : Implications for biodiversity and climate-change issues
- 2013
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In: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 23:12, s. 1747-1763
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Journal article (peer-reviewed)abstract
- We present a quantitative reconstruction of local forest history at two sites, Stavsåkra (hemiboreal zone) and Storasjö (southern boreal zone), in southern Sweden (province of Småland) to evaluate possible causes of contrasting Holocene fire histories in mid- and late Holocene. The Landscape Reconstruction Algorithm (LRA) is applied to evaluate between-site differences in the relative abundance of deciduous trees and Pinus (pine) and landscape/woodland openness during the Holocene. The LRA estimates of local vegetation abundance are compared with other proxies of local vegetation, that is, plant and beetle remains. The LRA results suggest that Pinus was a major tree taxon in the woodlands of Storasjö during mid- and late Holocene, while Tilia(linden) and Betula (birch) were dominant at Stavsåkra. The contrasting fire histories are shown to be strongly related to between-site differences in tree composition during mid-Holocene, 4000–2000 BC in particular. The archaeological/historical and beetle data indicate contrasting land uses from c. 1000BC (late Bronze Age/early Iron Age), grazing in open Calluna heaths at Stavsåkra and woodland grazing at Storasjö. Between-site differences in fire historyduring late Holocene were likely due to different land-use practices. Between-site differences in tree composition in mid-Holocene are best explainedby local climatic and geological/geomorphological differences between the hemiboreal and southern boreal zones of Småland, which might also be the primary cause of between-site differences in land-use histories during late Holocene. Maintenance of biodiversity at the landscape scale in the studyarea requires that existing old pine woodlands and Calluna heath are managed with fire and cattle grazing. Further climate warming might lead to higherprobabilities of climate-induces fire, in particular in pine-dominated woodlands.
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| 3. |
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| 4. |
- Gaillard, Marie-José, et al.
(author)
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The role of climate, human impact and fire on forestdynamics, landscape development and biodiversity during the last 10,500 calendar years in southern Sweden : a synthesis ofthe multiproxy study of Stavsåkra bog
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Other publication (other academic/artistic)abstract
- In this paper, we discuss the contribution of a multi-proxy approach to the study of long-term forest dynamics and biodiversity (at the species to landscape levels), using the records from a palaeoecological investigation at Stavsåkra, province of Småland, southern Sweden. The results from all the proxies, i.e. beetles, pollen, plant macrofossils, charred plant remains, andmicroscopical and macroscopical charcoal, are compared. The study of all charred material has the advantage of providing valuable information on the local plants that burnt (charred plant remains) and a more robust reconstruction of the local fire history and its regional representativeness. The plant macrofossil analysis allows specifying the origin of pollen from plants that may grow either on the coring site (fen or bog) or in the surrounding vegetation on dry land. This is particularly crucial for the interpretation of pollen types such as Gramineae, Cyperaceae, and Ericaceae (Calluna, Empetrum and Vaccinium species). The origin of Calluna pollen (bog, forest floor or open heaths) is often difficult to establish with certainty. In this study, the total absence of Calluna remains in the plant macrofossil record, and theoccurrence of beetle species dependant on Calluna heath ecosystems from the Late Neolithic (ca. 2000 BC) suggest that Calluna pollen originated from the surrounding vegetation, probably from the under-storey of the pine forests in early Holocene, and from the Calluna heaths during late Holocene. The beetle record further strengthens the inferred fire history by providing findings of species dependant on fire and, therefore, confirms the existence ofrelatively large burnt areas. Moreover, the insect analysis provides information on vegetation characteristics that cannot be inferred from pollen and plant macrofossil with certainty - or cannot be inferred at all - such as the forest structure in terms of openness, sun exposure, occurrence of dead wood and old trees. The results at Stavsåkra demonstrate that disturbances such as fire, forest clearance, and grazing can have both positive and negative impacts onbiodiversity, depending on the character and intensity of the disturbance in both time and space, and on the type of biota concerned, in this case plants and beetles.
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| 6. |
- Greisman, Annica, et al.
(author)
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The role of climate variability and fire in early and mid Holocene forest dynamics of southern Sweden
- 2009
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In: Journal of Quaternary Science. - : Wiley. - 0267-8179 .- 1099-1417. ; 24:6, s. 593-611
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Journal article (peer-reviewed)abstract
- The objective of this study was to investigate the possible links between regional climate, fire and vegetation at the small spatial scale during the early and mid Holocene in southern Sweden using pollen, plant macrofossil and charcoal records from a small bog. The fire history was compared with climate reconstructions inferred from various proxy records in the study region. High fire activity is related to dry and warm climate around 8550, 7600, 5500-5100 and 4500 cal. a BC. Low fire activity ca. 6500-6000 and 4750 BC may correspond to the widespread '8.2 k event' (ca. 6200 BC) recorded across the North Atlantic region, and a later, brief period of increased precipitation, respectively. The decrease in broadleaved trees Culminating ca. 6500-6000 BC correlates with the '8.2 k event'. A long mid Holocene period with low fire activity (ca. 4350-1000 BC) agrees with the pattern emerging for Europe from the global charcoal database, and may correspond to generally wetter and cooler conditions. High fire activity ca. 8550 BC probably triggered the local establishment of Corylus. Warmer and drier conditions (and high fire activity) ca. 7600 BC might have favoured the establishment of Alnus, Quercus and Tilia. The fire-adapted Pinus maintained important populations throughout the early and mid Holocene.
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| 7. |
- Olsson, Fredrik, et al.
(author)
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A continuous record of fire covering the last 10500 calendar years from souther Sweden : The role of climate and human activities
- 2010
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In: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 291, s. 128-141
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Journal article (peer-reviewed)abstract
- A high-resolution, continuous 10,500 cal. yrs-long macroscopic charcoal record from a peat and lake sediment deposit at Storasjö, in the hemiboreal vegetation zone of southern Sweden, is presented. This record was compared with the microscopic charcoal record from the same core, and tentatively correlated with the macroscopic and microscopic charcoal records from another site (Stavsåkra), situated 30 km West of Storasjö. The charcoal records are also compared with regional climate proxy records with the aim to separate climate microscopic and macroscopic charcoal records represents local history was obtained from the continuous macroscopic charcoal analysis. A tentative correlation of the charcoal records between the sites indicates that most probably of regional character. Both sites exhibit three major phases of high 7250 BC to ca. 4000 BC, and 3) 750 BC to the 19th century. These three phases are separated by periods with lower or very low from the analysis of the recently developed global charcoal database. Fire appears to have been controlled by climate during the early and middle Holocene and by humans during the late Holocene. Warmer and drier climate during the early and middle Holocene caused frequent and intensive natural was an important disturbance factor in the hemiboreal vegetation zone of Sweden and played an important role in the forest dynamics and characteristics of the — from human-induced fire activity. The results suggest that the major signal of bothfire history. The best record of local firefire episodes of the early and middle Holocene arefire activity 1) 8700–8300 BC, 2)fire activity. This general trend is in good agreement with the pattern emerging for Europefires, which suggests thatfire activity might increase under predicted future climate scenarios. The results also suggest that fireflora and fauna of the region.
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| 8. |
- Trondman, Anna-Kari, et al.
(author)
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Are pollen records from small sites appropriate for REVEALS model-based quantitative reconstructions of past regional vegetation? : An empirical test in southern Sweden
- 2016
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In: Vegetation History and Archaeobotany. - : Springer Science and Business Media LLC. - 0939-6314 .- 1617-6278. ; 25:2, s. 131-151
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Journal article (peer-reviewed)abstract
- In this paper we test the performance of the Regional Estimates of VEgetation Abundance from Large Sites (REVEALS) model using pollen records from multiple small sites. We use Holocene pollen records from large and small sites in southern Sweden to identify what is/are the most significant variable(s) affecting the REVEALS-based reconstructions, i.e. type of site (lakes and/or bogs), number of sites, site size, site location in relation to vegetation zones, and/or distance between small sites and large sites. To achieve this objective we grouped the small sites according to (i) the two major modern vegetation zones of the study region, and (ii) the distance between the small sites and large lakes, i.e. small sites within 50, 100, 150, or 200 km of the large lakes. The REVEALS-based reconstructions were performed using 24 pollen taxa. Redundancy analysis was performed on the results from all REVEALS-model runs using the groups within (i) and (ii) separately, and on the results from all runs using the groups within (ii) together. The explanatory power and significance of the variables were identified using forward selection and Monte Carlo permutation tests. The results show that (a) although the REVEALS model was designed for pollen data from large lakes, it also performs well with pollen data from multiple small sites in reconstructing the percentage cover of groups of plant taxa (e.g. open land taxa, summer-green trees, evergreen trees) or individual plant taxa; however, in the case of this study area, the reconstruction of the percentage cover of Calluna vulgaris, Cyperaceae, and Betula may be problematic when using small bogs; (b) standard errors of multiple small-site REVEALS estimates will generally be larger than those obtained using pollen records from large lakes, and they will decrease with increasing size of pollen counts and increasing number of small sites; (c) small lakes are better to use than small bogs if the total number of small sites is low; and (d) the size of small sites and the distance between them do not play a major role, but the distance between the small sites and landscape/vegetation boundaries is a determinant factor for the accuracy of the vegetation reconstructions.
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