| 1. |
- Trondman, Anna-Kari, et al.
(författare)
-
Pollen-based quantitative reconstructions of Holocene regional vegetation cover (plant-functional types and land-cover types) in Europe suitable for climate modelling
- 2015
-
Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 21:2, s. 676-697
-
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.
|
|
| 2. |
- Gandouin, E., et al.
(författare)
-
Environmental and climate reconstruction of the late-glacial-Holocene transition from a lake sediment sequence in Aubrac, French Massif Central : Chironomid and diatom evidence
- 2016
-
Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182. ; 461, s. 292-309
-
Tidskriftsartikel (refereegranskat)abstract
- The analysis of fossil chironomid and diatom assemblages from a sedimentary record from Les Roustières peat bog (Massif Central, France, 1196 m asl) allows the reconstruction of past environmental and climate changes during the late-glacial and early Holocene. Chironomid assemblages showed that the infilling of the palaeolake had commenced during the Oldest Dryas (GS-2b) as suggested by the rapid decrease in chironomid species associated with the cold and deep zone of lakes and by their replacement by littoral and eutrophic taxa. Quantitative July temperature reconstructions, based on the chironomid data, suggest that mean July air temperature (Tjul) ranged between 6 °C and 11 °C at the termination of the Oldest Dryas period (GS-2b). Climate began to warm at the start of the Bølling period (GI-1e), between 15,000 and 14,800 cal yr BP, with a rise in Tjul of about 4 °C. This climate warming is contemporaneous with lake eutrophication as suggested by diatoms and chironomids. Maximum temperatures of 13–14 °C were reached around 13,600 cal yr BP during the Allerød period (GI-1c–GI-1a). The Younger Dryas period (GS-1) is marked by a return to cold conditions with Tjul of about 10 °C during a first phase, then 13 °C in its terminal part. A probable increase in the duration of the ice-cover may have favoured arctic and alpine diatom species. The early-Holocene climate improvement is marked by a rise in Tjul of about 3 °C.
|
|
| 3. |
- Roberts, N., et al.
(författare)
-
Europe's lost forests : a pollen-based synthesis for the last 11,000 years
- 2018
-
Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- 8000 years ago, prior to Neolithic agriculture, Europe was mostly a wooded continent. Since then, its forest cover has been progressively fragmented, so that today it covers less than half of Europe's land area, in many cases having been cleared to make way for fields and pasture-land. Establishing the origin of Europe's current, more open land-cover mosaic requires a long-term perspective, for which pollen analysis offers a key tool. In this study we utilise and compare three numerical approaches to transforming pollen data into past forest cover, drawing on >1000 C-14-dated site records. All reconstructions highlight the different histories of the mixed temperate and the northern boreal forests, with the former declining progressively since similar to 6000 years ago, linked to forest clearance for agriculture in later prehistory (especially in northwest Europe) and early historic times (e.g. in north central Europe). In contrast, extensive human impact on the needle-leaf forests of northern Europe only becomes detectable in the last two millennia and has left a larger area of forest in place. Forest loss has been a dominant feature of Europe's landscape ecology in the second half of the current interglacial, with consequences for carbon cycling, ecosystem functioning and biodiversity.
|
|
