The lateglacial Quercus expansion in the southern European Alps: rapid vegetation response to a late Allerød climate warming? (original) (raw)
Related papers
Quaternary Science Reviews, 2010
The sediments of Lake Fimon, N-Italy, contain the first continuous archive of the Late Pleistocene environmental and climate history of the southern Alpine foreland. We present here the detailed palynological record of the interval between Termination II and the Last Glacial Maximum. The ageedepth model is obtained by radiocarbon dating in the uppermost part of the record. Downward, we correlated major forest expansion and contraction events to isotopic events in the Greenland Ice core records, via a stepping-stone approach involving intermediate correlation to isotopic events dated by TIMS U/Th in Alpine and Apennine stalagmites, and to pollen records from marine cores of the Iberian margin. Modelled ages obtained by Bayesian analysis of deposition are thoroughly consistent with actual ages, with maximum offset of AE1700 years. Sharp expansion of broad-leaved temperate forest and of sudden water table rise mark the onset of the Last Interglacial after a treeless steppe phase at the end of penultimate glaciation. This event is actually a two-step process which matches the two-step rise observed in the isotopic record of the nearby Antro del Corchia stalagmite, respectively dated to 132.5 AE 2.5 and 129 AE 1.5 ka. At the interglacial decline mixed oak forests were replaced by oceanic mixed forests, the latter persisting further for 7 ka till the end of the Eemian succession. Warm-temperate woody species are still abundant at the Eemian end, corroborating a steep gradient between central Europe and the Alpine divide at the inception of the last glacial. After a stadial phase marked by moderate forest decline, a new expansion of warm broad-leaved forests, interrupted by minor events and followed by mixed oceanic forests, can be identified with the north-alpine Saint Germain I. The spread of beech during the oceanic phase is a valuable circumalpine marker. The subsequent stadialeinterstadial succession, lacking the telocratic oceanic phase, is also consistent with the evidence at the north-alpine foreland. The Middle Würmian (full glacial) is marked by persistence of mixed forests dominated by conifers but with significant lime and other broad-leaved species. A major Arboreal Pollen decrease is observed at modelled age of 38.7 AE 0.5 ka (larch expansion and last occurrence of lime), which has been related to Heinrich Event 4. The evidence of afforestation persisting south of the Alps throughout most of MIS 3 contrasts with a boreal and continental landscape known for the northern alpine foreland, pointing to a sharp rainfall boundary at the Alpine divide and to southern air circulation. This is in agreement with the Alpine paleoglaciological record and is supported by the pressure and rainfall patterns designed by mesoscale paleoclimate simulations. Strenghtening the continental high pressure during the full glacial triggered cyclogenesis in the middle latitude eastern Europe and orographic rainfall in the eastern Alps and the Balkanic mountains, thus allowing forests development at current sea-level altitudes.
The spread of deciduous Quercus throughout Europe since the last glacial period
Forest Ecology and Management, 2002
For most of the last glacial period, which ended about 10 ka BP 2 , the temperate forest species were restricted to small areas (termed refugia) with a milder climate, situated mostly along the Mediterranean borderlands and around the Black Sea. Species only started to expand from these glacial period refugia with the large-scale shifts in the global climate in the lateglacial (15±10 ka BP) and the beginning of the Holocene period (10 ka BP to present).
Abstract and list of all Authors: 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° 9 1° 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. A . - K . TRONDMAN , M. - J . GAILLARD, F. MAZIER, S. SUGITA , R. FYFE, A. B . NIELSEN, C. TWIDDLE, P. BARRATT, H. J. B. BIRKS, A. E. BJUNE, L . BJÖRKMAN, A. BROSTRÖM, C. CASELDINE, R. DAVID, J. DODSON, W. DÖRFLER, E. FISCHER, B. VAN GEEL, T. GIESECKE, T. HULTBERG, L . KALNINA, M. KANGUR, P. VAN DE R KNAAP, T. KOFF, P. KUNES, P. LAGERAAS, M. LATAŁOWA, J. LECHTERBECK , C. LEROYER, M. LEYDET, M. LINDBLADH, L . MARQUER, F. J. G. MITCHELL, B. V. ODGAARD, S. M. PEGLAR, T. PERSSON, A. POSKA, M. RÖSCH, H. SEPPÄ, S. VESKI L. WICK
Quaternary International, 2012
Postglacial climate changes and vegetation responses were studied using a combination of biological and physical indicators preserved in lake sediments. Low-frequency trends, high-frequency events and rapid shifts in temperature and moisture balance were probed using pollenbased quantitative temperature reconstructions and oxygen-isotopes from authigenic carbonate and aquatic cellulose, respectively. Pollen and plant macrofossils were employed to shed light on the presence and response rates of plant populations in response to climate changes, particularly focusing on common boreal and temperate tree species. Additional geochemical and isotopic tracers facilitated the interpretation of pollen-and oxygen-isotope data.
We reconstruct the vegetational history of the southern side of the Alps at 18,000-10,000 cal yr BP using previous and new AMS-dated stratigraphic records of pollen, stomata, and macrofossils. To address potential effects of climatic change on vegetation, we compare our results with independent paleoclimatic series (e.g. isotope and chironomid records from the Alps and the Alpine forelands). The period before 16,000 cal yr BP is documented only at the lowland sites. The previous studies used for comparison with our new Palughetto record, however, shows that Alpine deglaciation must have started before 18,000-17,500 cal yr BP south of the Alps and that deglaciated sites were colonized by open woods and shrublands (Juniperus, tree Betula, Larix, Pinus cembra) at ca 17,500 cal yr BP. The vegetational history of a new site (Palughetto, 1040 m a.s.l.) is consistent with that of previous investigations in the study region. Our results show three conspicuous vegetational shifts delimited by statistically significant pollen zones,
Palaeogeography, Palaeoclimatology, Palaeoecology, 2013
High-resolution pollen analyses made on the same samples on which the ratios of oxygen isotopes were measured that provided the time scale and a temperature proxy after correlation to NorthGRIP. (1) A primary succession: The vegetation responded to the rapid rise of temperatures around 14,685 yr BP, with a primary succession on a decadal to centennial time scale. The succession between ca 15,600 and 13,000 yr BP included: (1.1.) The replacement of shrub-tundra by woodland of Juniperus and tree birch (around 14,665 yr BP) (1.2.) The response of Juniperus pollen to the shift in oxygen isotopes in less than 20 yr, (1.3.) A sequence of population increases of Hippophaë rhamnoides (ca 14,600 yr BP), Salix spp. (ca 14,600 yr BP), Betula trees (ca.14,480 yr BP), Populus cf. tremula (ca. 14,300 yr BP), and Pinus cf. sylvestris (ca. 13,830 yr BP). (2) Biological processes: Plants responded to the rapid increase of summer temperatures on all organisational levels: (2.1) Individuals may have produced more pollen (e.g. Juniperus); (2.2) Populations increased or decreased (e.g. Juniperus, Betula, later Pinus), and (2.3) Populations changed their biogeographical range and may show migrational lags. (2.4) Plant communities changed in their composition because the species pools changed through immigration and (local) extinction. Some plant communities may have been without modern analogue. These mechanisms require increasing amounts of time. (2.5) Processes on the level of ecosystems, with species interactions, may involve various time scales. Besides competition and facilitation, nitrogen fixation is discussed. (3) The minor fluctuations of temperature during the Late-Glacial Interstadial, which are recorded in δ 18 O, resulted in only very minor changes in pollen during the Aegelsee Oscillation (Older Dryas biozone, GI-1d) and the Gerzensee Oscillation (GI-1b). (4) Biodiversity: The afforestation at the onset of Bølling coincided with a gradual increase of taxonomic diversity up to the time of the major Pinus expansion.
Quaternary International, 2008
The high topographic complexity of the Alpine region is the origin of important climate differences that characterise the different areas of the Alps. These differences might have had a strong influence on vegetation and on migrations of human populations in the past. Based on an improved database containing about 3000 modern pollen samples, the standard ''Modern Analogue Technique'' has been applied to five pollen sequences from the subalpine belt of the Southwestern Italian Alps (Laghi dell'Orgials, 2240 m, Lago delle Fate, 2130 m, Torbiera del Biecai, 1920 m, Rifugio Mondovı`, 1760 m, Pian Marchisio, 1624 m) to provide quantitative climate estimates for the Lateglacial and Holocene periods. Consistent climate trends are reconstructed for the different sequences. Sites recorded in detail the climate variations when they were located at the limit of two ecotones. Sites above the tree line recorded lower temperature values and less important variations. Climate was cold and dry during the Oldest and Younger Dryas and close to present-day values during the Bølling/Allerød interstadial. At the beginning of the Holocene, climate changed to warmer and moister conditions; a high number of climate fluctuations are recorded at several sites. A climate optimum is recorded in the Atlantic period, which caused a development of fir above its present-day altitudinal distribution. Climatic differences recorded at the various sites are discussed taking into account the limits of the method.
Persistence of tree taxa in Europe and Quaternary climate changes
Quaternary International, 2010
The possibility that some populations of tree species may have survived multiple Quaternary glacial–interglacial cycles in central Europe is discussed. The alternation of forest and non-forest phases observed in long pollen records shows a substantial correspondence with the variations in global ice volume and indicates that the last glacial has been one of the most unfavourable periods for tree survival in Europe. Therefore the species that have survived the last glacial period in central Europe may have reasonably persisted also during less severe glacial periods and ultimately since the beginning of the Quaternary. The history of Picea and Corylus exemplifies the possibility of a continuous presence of trees in Europe. Recognizing the persistence of tree populations is necessary to assess the timing of their genetic diversification. The importance of extending the observation of the species behaviour to the time scale of the whole Quaternary is highlighted, in order to explain the modern distribution of populations and species and to reach a better understanding of evolutionary processes.
The Holocene, 2018
Understanding how climate has modulated forest growth and composition in the past is necessary to predict the influence of the ongoing climate warming on the dynamics of mountain forests. We studied the past dynamics of subalpine Pyrenean forests during the last 700 years by assessing the relationships between sedimentary pollen and tree-ring records, and their link with climatic drivers. We compared the pollen record and the montane pollen ratio, an integrative index obtained from sedimentary pollen that allows inferring past altitudinal variations in the montane–subalpine ecotone, with tree-ring width from mountain pine ( Pinus uncinata) subalpine forests located in Central Pyrenees. To assess climate–growth associations, we related the dendrochronological data with instrumental meteorological records (1901–2010) and temperature reconstructions from the Pyrenees and Northern Hemisphere. Few robust associations were found between arboreal pollen taxa and tree-ring width series of t...
Quaternary Science Reviews, 2007
We reconstruct the vegetational history of the southern side of the Alps at 18,000-10,000 cal yr BP using previous and new AMS-dated stratigraphic records of pollen, stomata, and macrofossils. To address potential effects of climatic change on vegetation, we compare our results with independent paleoclimatic series (e.g. isotope and chironomid records from the Alps and the Alpine forelands). The period before 16,000 cal yr BP is documented only at the lowland sites. The previous studies used for comparison with our new Palughetto record, however, shows that Alpine deglaciation must have started before 18,000-17,500 cal yr BP south of the Alps and that deglaciated sites were colonized by open woods and shrublands (Juniperus, tree Betula, Larix, Pinus cembra) at ca 17,500 cal yr BP. The vegetational history of a new site (Palughetto, 1040 m a.s.l.) is consistent with that of previous investigations in the study region. Our results show three conspicuous vegetational shifts delimited by statistically significant pollen zones,