| 1. |
- Trondman, Anna-Kari, et al.
(författare)
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Pollen-based quantitative reconstructions of Holocene regional vegetation cover (plant-functional types and land-cover types) in Europe suitable for climate modelling
- 2015
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 21:2, s. 676-697
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Tidskriftsartikel (refereegranskat)abstract
- We present quantitative reconstructions of regional vegetation cover in north-western Europe, western Europe north of the Alps, and eastern Europe for five time windows in the Holocene [around 6k, 3k, 0.5k, 0.2k, and 0.05k calendar years before present (bp)] at a 1 degrees x1 degrees spatial scale with the objective of producing vegetation descriptions suitable for climate modelling. The REVEALS model was applied on 636 pollen records from lakes and bogs to reconstruct the past cover of 25 plant taxa grouped into 10 plant-functional types and three land-cover types [evergreen trees, summer-green (deciduous) trees, and open land]. The model corrects for some of the biases in pollen percentages by using pollen productivity estimates and fall speeds of pollen, and by applying simple but robust models of pollen dispersal and deposition. The emerging patterns of tree migration and deforestation between 6k bp and modern time in the REVEALS estimates agree with our general understanding of the vegetation history of Europe based on pollen percentages. However, the degree of anthropogenic deforestation (i.e. cover of cultivated and grazing land) at 3k, 0.5k, and 0.2k bp is significantly higher than deduced from pollen percentages. This is also the case at 6k in some parts of Europe, in particular Britain and Ireland. Furthermore, the relationship between summer-green and evergreen trees, and between individual tree taxa, differs significantly when expressed as pollen percentages or as REVEALS estimates of tree cover. For instance, when Pinus is dominant over Picea as pollen percentages, Picea is dominant over Pinus as REVEALS estimates. These differences play a major role in the reconstruction of European landscapes and for the study of land cover-climate interactions, biodiversity and human resources.
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| 2. |
- Gaillard, Marie-José, 1953-, et al.
(författare)
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Holocene land-cover reconstructions for studies on land cover-climate feedbacks
- 2010
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 6, s. 483-499
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Tidskriftsartikel (refereegranskat)abstract
- The major objectives of this paper are: (1) to review the pros and cons of the scenarios of past anthropogenic land cover change (ALCC) developed during the last ten years, (2) to discuss issues related to pollen-based reconstruction of the past land-cover and introduce a new method, REVEALS (Regional Estimates of VEgetation Abundance from Large Sites), to infer long-term records of past land-cover from pollen data, (3) to present a new project (LANDCLIM: LAND cover – CLIMate interactions in NW Europe during the Holocene) currently underway, and show preliminary results of REVEALS reconstructions of the regional land-cover in the Czech Republic for five selected time windows of the Holocene, and (4) to discuss the implications and future directions in climate and vegetation/land-cover modeling, and in the assessment of the effects of human-induced changes in land-cover on the regional climate through altered feedbacks. The existing ALCC scenarios show large discrepancies between them, and few cover time periods older than AD 800. When these scenarios are used to assess the impact of human land-use on climate, contrasting results are obtained. It emphasizes the need for methods such as the REVEALS model-based land-cover reconstructions. They might help to fine-tune descriptions of past land-cover and lead to a better understanding of how long-term changes in ALCC might have influenced climate. The REVEALS model is demonstrated to provide better estimates of the regional vegetation/landcover changes than the traditional use of pollen percentages. This will achieve a robust assessment of land cover at regional- to continental-spatial scale throughout the Holocene. We present maps of REVEALS estimates for the percentage cover of 10 plant functional types (PFTs) at 200 BP and 6000 BP, and of the two open-land PFTs “grassland” and “agricultural land” at five time-windows from 6000 BP to recent time. The LANDCLIM results are expected to provide crucial data to reassess ALCC estimates for a better understanding of the land suface-atmosphere interactions.
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| 3. |
- Bragée, Petra, et al.
(författare)
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Historical TOC concentration minima during peak sulfur deposition in two Swedish lakes
- 2015
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 12:2, s. 307-322
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Tidskriftsartikel (refereegranskat)abstract
- Decadal-scale variations in total organic carbon (TOC) concentration in lake water since AD1200 in two small lakes in southern Sweden were reconstructed based on visible-near-infrared spectroscopy (VNIRS) of their recent sediment successions. In order to assess the impacts of local land-use changes, regional variations in sulfur, and nitrogen deposition and climate variations on the inferred changes in TOC concentration, the same sediment records were subjected to multi-proxy palaeolimnological analyses. Changes in lake-water pH were inferred from diatom analysis, whereas pollen-based land-use reconstructions (Landscape Reconstruction Algorithm) together with geochemical records provided information on catchment-scale environmental changes, and comparisons were made with available records of climate and population density. Our long-term reconstructions reveal that inferred lake-water TOC concentrations were generally high prior to AD1900, with additional variability coupled mainly to changes in forest cover and agricultural land-use intensity. The last century showed significant changes, and unusually low TOC concentrations were inferred at AD1930-1990, followed by a recent increase, largely consistent with monitoring data. Variations in sulfur emissions, with an increase in the early 1900s to a peak around AD1980 and a subsequent decrease, were identified as an important driver of these dynamics at both sites, while processes related to the introduction of modern forestry and recent increases in precipitation and temperature may have contributed, but the effects differed between the sites. The increase in lake-water TOC concentration from around AD1980 may therefore reflect a recovery process. Given that the effects of sulfur deposition now subside and that the recovery of lake-water TOC concentrations has reached pre-industrial levels, other forcing mechanisms related to land management and climate change may become the main drivers of TOC concentration changes in boreal lake waters in the future.
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| 4. |
- Eklöf, Martin, et al.
(författare)
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OPENLAND3: a computer program to estimate plant abundance around pollen sampling sites from vegetation maps: a necessary step for calculation of pollen productivity estimates
- 2004
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Ingår i: Review of Palaeobotany and Palynology. - : Elsevier BV. - 0034-6667. ; 132:1-2, s. 67-77
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Tidskriftsartikel (refereegranskat)abstract
- OPENLAND3 belongs to a suite of computer programs included in the POLLSCAPE simulation model. These programs make it possible to calculate estimates of pollen loadings in lake basins or bogs using vegetation data. OPENLAND3, written in Visual Basic 6, is designed to produce appropriate vegetation data files from vegetation maps stored in a Geographical Information System. It calculates percentage cover of plant taxa in concentric circles at increasing distances from a central point, using either real digitised maps or hypothetical maps (simulated landscape designs). Such data are necessary for simulation of pollen dispersal and deposition, and for calculation of pollen productivity estimates and relevant source area of pollen using specific mathematical models developed by palynologists, such as the Prentice-Sugita model. OPENLAND3 also produces output files needed to run RS-OPEN, another program included in POLLSCAPE, in order to obtain estimates of pollen loadings in lakes or bogs. The rationale of OPENLAND3, the algorithm used, and a modification of RS-OPEN (RS-OPEN2) are described. A test of the programme capability using a detailed vegetation map from southern Sweden shows that simulations using OPENLAND3 produce coherent results. Pollen loading for species characterized by high pollen productivity is higher than for species with low pollen productivity. Altering the wind speed has also a significant effect on pollen loading. As wind speed increases, the proportions of the light pollen decrease, while the heavy pollen types increase, which is what empirical data suggest, and what the model predicts in earlier studies. (C) 2004 Elsevier B.V. All rights reserved.
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| 5. |
- Åkesson, Christine, et al.
(författare)
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From landscape description to quantification : A new generation of reconstructions provides new perspectives on Holocene regional landscapes of SE Sweden
- 2015
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 25:1, s. 178-193
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Forskningsöversikt (refereegranskat)abstract
- The development since the beginning of the 20th century of the pollen-analytical theory and method as a palaeoecological tool for describing landscape development is outlined with reference to southern Scandinavia. Numerical methods applied since the 1980s are discussed. The aim of this paper is to provide a new perspective on the landscape development and human impact during the Holocene by applying the Regional Estimates of VEgetation Abundance from Large Sites (REVEALS) model to the pollen records from the reference site Lake Farskesjon in SE Sweden. The model was applied both to a previously published record (core 1956, entire Holocene until ad 1600) and a newly collected dataset (core 2013, the last 3000years). The comparison between the REVEALS estimates of vegetation cover and historical landscape maps indicate that traditional, uncorrected pollen percentages significantly underestimate the degree of landscape openness created by long-term farming and pasturing, but that the degree of underestimation varies over time, depending on the species composition of both the forest and the open-land communities. The REVEALS reconstructions are also a useful tool for the quantification of past land-use changes that may have affected the nutrient loading to the Baltic Sea.
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| 6. |
- Broström, Anna
(författare)
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Estimating source area of pollen and pollen productivity in the cultural landscapes of southern Sweden - developing a palynological tool for quantifying past plant cover
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fossil pollen records retrieved from peat and lake sediments have great potential for quantifying past plant cover. This thesis is a contribution to the development of a palynological interpretation tool for reconstructing past cultural landscapes in terms of plant abundance and distribution. The aims of this thesis are (1) to explore pollen-vegetation relationships in the ancient, traditional cultural landscape of southern Sweden, (2) to test the potentials and limits of using mechanistic models of pollen dispersal and deposition to reconstruct past cultural landscapes from fossil pollen assemblages, (3) to estimate pollen productivity for the most common plant taxa characteristic of the past cultural landscapes of southern Sweden, and (4) to define and estimate the spatial scale of the cultural landscape reflected by pollen assemblages in moss polsters and small lakes. Data collection included sampling moss polsters and lake sediments for pollen and making vegetation surveys. The compilation of vegetation data was performed using GIS software. Pollen/vegetation relationships were explored using numerical techniques (PCA, RDA, Monte Carlo permutation test). Pollen productivity was estimated using Extended R-Value (ERV) -models. These models imply that vegetation is distance-weighted, which required the development of an appropriate design of vegetation survey in the field. The spatial scale of the landscape reflected by pollen assemblages is defined as the area beyond which the correlation of pollen and vegetation does not improve, and is named "relevant source area of pollen" (RSAP). RSAP was estimated using the maximum likelihood method. For hypothesis testing, a computer simulation model (POLLSCAPE) developed for forest vegetation was used to simulate pollen dispersal and deposition in cultural landscapes. The empirical pollen/vegetation data shows a major difference between the two contrasting vegetation regions of southern Sweden in terms of the relationship between NAP (herb pollen) percentages and open-land percentage cover. The relationship between NAP % and open-land % cover was also simulated using POLLSCAPE. The simulated and empirical relationships are very similar, which demonstrates that POLLSCAPE can be used for semi-open and open landscapes. Pollen productivity estimates (PPE) were obtained for 25 herb and tree taxa. RSAP for small lakes and moss polsters was estimated to be 800-1000 m and 400 m, respectively. Empirical data and simulations show that random site selection is required in order to obtain reliable estimates of RSAP, and that the spatial resolution of the vegetation survey close to the pollen sample, i.e. the size distribution of the vegetation mosaic, plays a critical role in RSAP estimates. Major implications of the results are (1) the cover of open land is likely to be strongly underestimated on the basis of NAP percentages alone in a mosaic semi-open landscape, (2) provided that past and present landscapes have a similar vegetation structure, a quantitative reconstruction of the past landscape would be possible within 1000 m radius around small lakes and 400 m radius around soil profiles, (3) the availability of PPE for critical herb taxa and the demonstration that POLLSCAPE may be used to study open and semi-open landscapes provide a reliable tool for proceeding with the study of pollen dispersal and deposition in cultural landscapes.
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| 7. |
- Broström, Anna, et al.
(författare)
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Geologi och landskapshistoria i och runt Arrie
- 2009
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Ingår i: Närnaturens mångfald : planering och brukande av Arriesjöns strövområde. - 1654-6881. - 9789197723336 ; 3, s. 20-33
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Arriesjöns strövområde var mellan 1906 och1998 en täkt för grus, sand och lera. Innan dess var området en ca 20 m hög platåliknande kulle som en isälv i den senaste inlandsisen lämnat efter sig. I kullens sediment har hittats mammutrester, renben och torv med växtrester som vittnar om ett annat klimat och en annorlunda miljö. Vad sedimenten består av och hur de hamnat där har geologer beskrivit, tolkat och omtolkat sedan slutet av 1800-talet. Detektivarbetet att rekonstruera istidernas förlopp, deras avlagringar på djupet och landskapets förändring fram tills idag är ständigt pågående. Det baseras på information från grustäkter, borrningar och utgrävningar i samband med vägbyggen, kustklintar (minerogena sediment) samt undersökningar av torv- och sjösediment (organogena sediment). För datering används förutom korrelation av lagerföljder mellan olika platser bl.a. Optisk Stimulerad Luminiscens och kol-14 för minerogena respektive organogena sediment. Nedan beskrivs områdets geologi, med dagens kunskapsläge, för att ge de förutsättningar som finns för landskapets förändring i och runt Arrie i ett långt tidsperspektiv. Det rumsliga perspektivet är både lokalt och regionalt.
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| 8. |
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| 9. |
- Broström, Anna, et al.
(författare)
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Mellan åkern och havet
- 2008
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Ingår i: Inne och ute i Malmö : studier av urbana förändringsprocesser. - 1654-6881. - 9789197723329 ; 2, s. 121-137
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 10. |
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