The importance of plant macrofossils in the reconstruction of Lateglacial vegetation and climate: examples from Scotland,western Norway,and Minnesota,USA

Lateglacial and early Holocene (ca 14–9000 ¹⁴C yr BP; 15–10,000 cal yr BP) pollen records are used to make vegetation and climate reconstructions that are the basis for inferring mechanisms of past climate change and for validating palaeoclimate model simulations. Therefore, it is important that reconstructions from pollen data are realistic and reliable. Two examples of the need for independent validation of pollen interpretations are considered here. First, Lateglacial-interstadial Betula pollen records in northern Scotland and western Norway have been interpreted frequently as reflecting the presence of tree-birch that has strongly influenced the resulting climate reconstructions. However, no associated tree-birch macrofossils have been found so far, and the local dwarf-shrub or open vegetation reconstructed from macrofossil evidence indicates climates too cold for tree-birch establishment. The low local pollen production resulted in the misleadingly high percentage representation of long-distance tree-birch pollen. Second, in the Minnesotan Lateglacial Picea zone, low pollen percentages from thermophilous deciduous trees could derive either from local occurrences of the tree taxa in the Picea/Larix forest or from long-distance dispersal from areas further south. The regionally consistent occurrence of low pollen percentages, even in sites with local tundra vegetation, and the lack of any corresponding macrofossil records support the hypothesis that the trees were not locally present. Macrofossils in the Picea zone represent tundra vegetation or Picea/Larix forest associated with typically boreal taxa, suggesting it was too cold for most thermophilous deciduous trees to grow. Any long-distance tree pollen is not masked by the low pollen production of tundra and Picea and Larix and therefore it is registered relatively strongly in the percentage pollen spectra.Many Lateglacial pollen assemblages have no recognisable modern analogues and contain high representations of well-dispersed ‘indicator’ taxa such as Betula or Artemisia. The spectra could have been derived from vegetation types that do not occur today, perhaps responding to the different climate that resulted from the different balance of climate forcing functions then. However, the available contemporaneous plant-macrofossil assemblages can be readily interpreted in terms of modern vegetation communities, suggesting that the pollen assemblages could have been influenced by mixing of locally produced pollen with long-distance pollen from remote vegetation types that are then over-represented in situations with low local pollen production. In such situations, it is important to validate the climate reconstructions made from the pollen data with a macrofossil record.     

A full-glacial biota from southeastern Iowa,USA

Wisconsinan full-glacial silts filling a swale exposed in Conklin Quarry, Johnson Co., Iowa, contain a large and diverse biota that includes pollen, bryophytes, vascular-plant macrofossils, small mammals, molluscs, and insects. Radiocarbon dates on wood from the top, middle and bottom of the swale fill respectively were 16710 ± 270, 17 170 ± 205, and 18090 ± 190 yr BP. The pollen diagram is dominated by Picea (spruce), Pinus (pine), and Cyperaceae (sedge), and it records low pollen accumulation rates. Plant macrofossils include a number of tundra species along with Picea and Larix (larch) needles and small pieces of wood. The insect fauna contains many species now confined to the forest-tundra transition zone of northwestern Yukon and Alaska. Small mammals include the tundra indicators Dicrostonyx (collared lemming), and probably Microtus miurus (singing vole) together with boreal forest taxa. The molluscs include extinct and relict species and show the widest range in present geographic distribution, but Rocky Mountain and especially northern elements predominate in the swale fill. All these lines of evidence lead to consistent palaeoclimato-logical interpretation and palaeoecological reconstruction. The dominant habitats represented by the biota and sedimentary environment collectively included open calcareous silty to sandy or gravelly upland sites, minerotrophic fens (wetlands), pond- or stream-side clayey to sandy shores, and shallow (possibly ephemeral), cold, clear-water ponds. Mean July temperatures were probably 11° to 13°C cooler than at present. The biota indicates that a Picea-Larix krummholz with extensive tundra openings was present in southeastern Iowa between 18090 and 16710 yr BP.     

The Fernbank interglacial site near Ithaca, New York, USA

The Fernbank interglacial site, on the west side of Cayuga Lake, New York, has been recently subjected to more detailed study. To a lengthened mollusc list are added ostracodes, insects, fish, pollen, and plant macrofossils. Of these, plants are well preserved and diverse, whereas other groups are poorly preserved and incomplete. Nevertheless, all support the interglacial assignment (Sangamon), which is further supported by minimum age radiocarbon dates (> 50,000 ¹⁴C yr BP) and a TL date of 81 ± 11 ka. In the plant record near the top of the sequence, abundant tree charcoal indicates forest fires. Like the Toronto interglacial record, the plants show a declining July mean temperature from 24 to 18°C (according to transfer functions) through the sequence, from mixed deciduous forest to boreal forest.     

Plant and insect fossils at Norwood in south-central Minnesota: A record of late-glacial succession

The Norwood site in Sibley Co., Minnesota, contains 1.6 m of silt resting on till and overlain by peat. The base of the peat has been radiocarbon dated at 12,400 ± 60 and the top at 11,200 ± 250 yr B.P. The pollen, plant macrofossils, and insect remains in the basal silt consist of boreal species inhabiting open environments, but not tundra. No modern analogue exists for the insect assemblage, which includes elements of boreal forest, tundra-forest, and western affinities. The transition from an unstable open environment to a stable coniferous forest is reflected by both plant and insect fossils and is interpreted as a successional rather than a climatic event. During this time of significant biologic change, the climate is inferred to have been relatively uniform, with temperatures similar to those presently existing in the boreal forest south of the tundra-forest transition zone. The geologic and ecologic succession at Norwood is generally similar to that presently associated with ice stagnation of the Klutlan Glacier in the Yukon Territory. Localized successional sequences similar to those at Norwood are conceived to have occurred repeatedly during the melting of the Laurentide ice, and thus the proposed model has potentially broad application to the interpretation of late-glacial sequences.     

Pollen and macrofossil‐inferred palaeoclimate at the Ridge Site,Hudson Bay Lowlands,Canada: evidence for a dry climate and significant recession of the Laurentide Ice Sheet during Marine Isotope Stage 3

We examine pollen, macrofossils and sedimentological proxies from the Ridge Site, an 18‐m sequence of glacial and non‐glacial sediments exposed along the bank of the Ridge River in the southern Hudson Bay Lowlands (HBL), Canada. As the HBL is located in the previously glaciated region of North America, palaeorecords from this region have important implications for understanding ice‐sheet palaeogeography and climate for the late Pleistocene. Two diamicton units were interpreted as subglacial till deposited by a glacier flowing toward the south‐southwest (lower diamicton) and west‐southwest (upper diamicton), respectively. Confined between these tills is a 6‐m non‐glacial unit, constrained to Marine Isotope Stage 3 (MIS 3; c. 57 000 to c. 29 000 a BP) by three radiocarbon dates. Quantitative analyses of the pollen record (dominated by Sphagnum, Cyperaceae, Pinus, Picea, Salix, Alnus and Betula) suggest that average summer temperature (June, July, August) was 14.6±1.51 °C, which is similar to that of the present day at the site. Total annual precipitation was 527±170 mm as compared to 705 mm present‐day. The macrofossil record confirmed the local presence of Betula, Salix and conifers. Our results, in combination with other records from the periphery of the Laurentide Ice Sheet, suggest that vast boreal forest‐type vegetation, along with a drier interstadial climate, existed in the region during MIS 3. We also compare pollen‐derived palaeoclimate reconstructions from the Ridge Site with reconstructions from a previously published site along the Nottaway River, HBL, which was dated to MIS 5a–d (c. 109 000 to c. 82 000 a BP). This comparison suggests that, with additional data, it may be possible to differentiate MIS 3 and MIS 5 deposits in the HBL on the basis of relative continentality, with MIS 3 characterized by lower total annual precipitation, and MIS 5 by values similar or greater than present‐day.     

Paleobotany of Wisconsinan interstadials, eastern Great Lakes region, North America

This study concerns the pollen and plant macrofossils from Mid-Wisconsinan Interstadial sites within the Wisconsinan ice margin in eastern North America. The time period covered is from about 55,000 years BP to 22,500 years BP, an interval much longer than the postglacial. Sediments examined are principally those of large lakes deposited in the Erie and Ontario basins during intervals of ice retreat.The Port Talbot I Interval (from about 55,000 to 50,000 years BP) in the Erie basin is characterized by pollen assemblages alternating from Pinus-dominated zones to ones with abundant Pinus, Quercus, and nonarboreal pollen. These assemblages are interpreted as indicating relatively warm and dry conditions. Mean July temperatures fluctuated between 15 and 21°C.During the succeeding Port Talbot II Interval and Plum Point Interstadial, in both the Erie and Ontario basins, pollen assemblages are characterized by dominant Pinus and Picea. Characteristic macrofossils include needles of the boreal Picea and Larix and leaves of species with a more northerly distribution, such as Dryas integrifolia, Betula glandulosa var. glandulosa, Vaccinium uliginosum var. alpinum, and Salix herbacea. These fossil assemblages are interpreted as indicating cooler and moister conditions in a forest-tundra environment. Mean July temperatures fluctuated between 10 and 15°C during the Port Talbot II Interval and Plum Point Interstadial.     

The tunica hills,Louisiana-Mississippi: Late glacial locality for spruce and deciduous forest species

Reinvestigation of Quaternary sediments in West Feliciana Parish, southeastern Louisiana, and adjacent Wilkinson County, southwestern Mississippi, has resulted in revision of previous terrace stratigraphy of this portion of the Gulf Coastal Plain. Plant-macrofossil and pollen assemblages incorporated in fluviatile terrace deposits in the study area are reexamined in light of the current stratigraphic understanding. Macrofossils identified as white spruce (Picea glauca), tamarack (Larix laricina), and northern white cedar (Thuja occidentalis), recovered from these terrace deposits along with fossil remains of distinctly southern plant species, were initially interpreted as the result of dynamic intermixing of aggressive boreal species within a southern forest during the early Wisconsin (Brown, 1938). Failure to distinguish chronologically separate fossiliferous deposits resulted in the conceptual “mixing” of northern and southern plant species which came from two distinct fluviatile terrace sequences. Terrace 2 is now believed to be a fluviatile and coastwise depositional terrace of Sangamon Interglacial age; deposits of terrace 2 contain a distinctly warm-temperate plant assemblage. Fluviatile terrace 1 dates from 12,740 ± 300 to 3457 ± 366 BP and is now considered to be related to late glacial and Holocene aggradation and lateral migration of the Mississippi River (the local base level for streams in the study area); basal portions of terrace 1 contain fossils of white spruce, tamarack, and many plant species today characteristic of the cool-temperate Mixed Mesophytic Forest Association. Terrace 1 fossil deposits occur in fluviatile terraces along tributary streams of the Mississippi River at elevations 15 to 30 m above the maximum recorded historic flood stage of the Mississippi River. The plant macrofossils represent remains of species that grew at or very near the site of deposition; they were not “rafted in” by floodwaters of the Mississippi River. We present quantitative data for plant macrofossils and pollen that support our hypothesis that at least local cooling along the Blufflands of Mississippi and Louisiana promoted southward migrations of mixed mesophytic forest species and certain boreal species along this major pathway during late Wisconsin continental glaciation.     

Holocene vegetation and climate change in southern New Zealand: linkages between forest composition and quantitative surface moisture reconstructions from an ombrogenous bog

This paper presents a Holocene pollen record from an ombrotrophic bog in Southland, New Zealand, together with multiproxy data (testate amoebae, peat humification and plant macrofossils) from the same core to establish an independent semiquantitative record of peatland surface moisture. Linkages between reconstructed peatland surface moisture and regional forest composition are investigated using redundancy analysis of the forest pollen data constrained with predicted bog water‐table depths. Over 32% of the pollen data variance can be explained by surface moisture changes in the bog, suggesting a common cause of water‐table and regional vegetation change. Water tables were higher during the early to mid‐Holocene when the forest was dominated by podocarp taxa. Water tables lowered after about 3300 cal. yr BP coevally with the expansion of Nothofagus species, culminating with the dominance of Nothofagus subgenus Fuscospora in the past 1200 cal. yr BP. This is in apparent opposition to the warm/dry to cool/wet trend suggested by subjective interpretation of pollen data alone, from this and other studies. We suggest that during the late Holocene, drier summers associated with shifts in solar insolation caused reduced surface wetness and summer humidity, which together with a trend to cooler winters, apparently favoured the regeneration of Nothofagus species. Copyright © 2002 John Wiley & Sons, Ltd.     

Late-glacial vegetation associated with caribou and mastodon in central Indiana

The Christensen Mastodon Site, located in central Indiana, contains a rich assemblage of vertebrates (including mastodon, caribou, and giant beaver), invertebrates, and plant macrofossils in situ in lake and bog sediments of late-glacial age. Studies of pollen and plant macrofossils suggest the existence of open, white spruce-dominated boreal forests from >; 14,000 yr B.P. to ca. 13,000 yr B.P. The regional decline of spruce, local occurrence of black spruce, white spruce, and larch, immigration of many hardwood taxa (e.g., ash, oak, elm), and the initiation of bog development are recorded beginning about 13,000 yr B.P. Recent reconstructions of late-glacial and early postglacial vegetational changes provide a context for understanding the disappearance of mastodons. The dramatic and rapid restriction of boreal forests along the retreating ice margin from 11,000 to 9000 yr B.P. may have caused a substantial reduction of mastodon populations. A diminished population would be more susceptible to small-scale, stochastic events such as short-term extremes of weather, outbreaks of disease, or predation pressure from paleoindian hunters.     

Late Quaternary palaeoecological and palaeoclimatological reconstruction in the Gutaiului Mountains,northwest Romania

Macrofossil, pollen, lithostratigraphy, mineral magnetic measurements (SIRM and magnetic susceptibility), loss‐on‐ignition, and AMS radiocarbon dating on sediments from two former crater lakes, situated at moderate altitudes in the Gutaiului Mountains of northwest Romania, allow reconstruction of Late Quaternary climate and environment. Shrubs and herbs with steppe and montane affinities along with stands of Betula and Pinus, colonised the surroundings of the sites prior to 14 700 cal. yr BP and the inferred climatic conditions were cold and dry. The gradual transition to open Pinus–Betula forests, slightly higher lake water temperatures, and higher lake productivity, indicate more stable environmental conditions between 14 700 and 14 100 cal. yr BP. This development was interrupted by cooler and drier climatic conditions between 14 100 and 13 800 cal. yr BP, as inferred from a reduction of open forests to patches, or stands, of Pinus, Betula, Larix, Salix and Populus. The expansion of a denser boreal forest, dominated by Picea, but including Pinus, Larix, Betula, Salix, and Ulmus started at 13 800 cal. yr BP, although the forest density seems to have been reduced between 13 400 and 13 200 cal. yr BP. Air temperature and moisture availability gradually increased, but a change towards drier conditions is seen at 13 400 cal. yr BP. A distinct decrease in temperature and humidity between 12 900 and 11 500 cal. yr BP led to a return of open vegetation, with patches of Betula, Larix, Salix, Pinus and Alnus and individuals of Picea. Macrofossils and pollen of aquatic plants indicate rising lake water temperatures and increased aquatic productivity already by ca. 11 800 cal. yr BP, 300 years earlier than documented by the terrestrial plant communities. At the onset of the Holocene, 11 500 cal. yr BP, forests dominated by Betula, Pinus and Larix expanded and were followed by dense Ulmus forests with Picea, Betula and Pinus at 11 250 cal. yr BP. Larix pollen was not found, but macrofossil evidence indicates that Larix was an important forest constituent at the onset of the Holocene. Moister conditions were followed by a dry period starting about 10 600 cal. yr BP, which was more pronounced between 8600 and 8200 cal. yr BP, as inferred from aquatic macrofossils. The maximum expansion of Tilia, Quercus, Fraxinus and Acer between 10 700 and 8600 cal. yr BP may reflect a more continental climate. A drier and/or cooler climate could have been responsible for the late expansion (10 300 cal. yr BP) and late maximum (9300 cal. yr BP) of Corylus. Increased water stress, and possibly cooler conditions around 8600 cal. yr BP, may have caused a reduction of Ulmus, Tilia, Quercus and Fraxinus. After 8200 cal. yr BP moisture increased and the forests included Picea, Tilia, Quercus and Fraxinus. Copyright © 2004 John Wiley & Sons, Ltd.     

Late Pleistocene vegetation of Kings Canyon,Sierra Nevada,California

Seven packrat midden samples make possible a comparison between the modern and late Pleistocene vegetation in Kings Canyon on the western side of the southern Sierra Nevada. One modern sample contains macrofossils and pollen derived from the present-day oak-chaparral vegetation. Macrofossils from the six late Pleistocene samples record a mixed coniferous forest dominated by the xerophytic conifers Juniperus occidentalis, Pinus cf. ponderosa, and P. monophylla. The pollen spectra of these Pleistocene middens are dominated by Pinus sp., Taxodiaceae-Cupressaceae-Taxaceae (TCT), and Artemisia sp. Mesophytic conifers are represented by low macrofossil concentrations. Sequoiadendron giganteum is represented by a few pollen grains in the full glacial. Edaphic control and snow dispersal are the most likely causes of these mixed assemblages.The dominant macrofossils record a more xeric plant community than those that now occur on similar substrates at higher elevations or latitudes in the Sierra Nevada. These assemblages suggest that late Wisconsin climates were cold with mean annual precipitation not necessarily greater than modern values. This conclusion supports a model of low summer ablation allowing for the persistence of the glaciers at higher elevations during the late Wisconsin. The records in these middens also suggest that S. giganteum grew at lower elevations along the western side of the range and that P. monophylla was more widely distributed in cismontane California during the Pleistocene.     

Vegetation and climate during the last glacial maximum in Japan

The Japanese Archipelago was almost entirely covered by coniferous forests during the last glacial maximum. Northern Hokkaido was distinguished by coniferous parkland and tundra vegetation, while southern Hokkaido and northernmost Honshu were covered by northern boreal coniferous forests consisting mainly of Picea jezoensis, Picea glehnii, Abies sachalinensis, and Larix gmelinii; Tsuga was missing from the forest. More diverse boreal forests including species from Sakhalin and northern Japan grew together in northeastern Honshu. Central Honshu and the mountains of southwestern Japan supported subalpine coniferous forests which are now mainly restricted in distribution to the central mountains. Temperate coniferous forests (Picea polita, Abies firma, and Tsuga sieboldii) existed principally in the modern mid-temperate and evergreen laurel-oak forest regions. Haploxylon pine and tree birch were also abundant in the boreal and cool-temperate zones, as was Diploxylon in the southern temperate zone. Significant populations of Fagus were found along the Pacific coasts of Kyushu and Shikoku, but they were too small to be defined as a beech forest zone. Quercetum mixtum (Quercus, Ulmus, and Tilia) was more common in the coastal lowlands of southwestern Japan than those of northeastern Honshu; it was completely eliminated from Hokkaido. The reduced mean August temperature inferred from the floral assemblages showed a latitudinal gradient 20,000 yr ago; it was 8–9°C in northern Hokkaido, 7.7–8.7°C in northernmost Honshu, 7.2–8.4°C in the central mountains, 6.5°C in the Chugoku District, and 5–6°C in Kyushu. The probable annual precipitation ranged from 1050 to 1300 mm along coasts in southwestern Japan during the culmination of the last glaciation.     

Map of vegetation during the last glacial maximum in Japan

A vegetation map reconstructed for the Japanese Archipelago (based upon pollen data from 28 sites and plant macrofossil data from 33 sites) at the time of last glacial maximum shows that coniferous forests covered extensive areas of the land. Boreal conifer forests (dominated by the Picea jezoensis complex, P. glehnii, Abies sachalinensis, A. mariesii, Tsuga diversifolia, and Pinus with Larix gmelinii, though the latter species was confined only to the northern part of northeastern Honshu and Hokkaido) occupied the modern cool-temperature deciduous broadleaf and mid-temperate conifer forest zones, and temperate coniferous forests (mainly Picea maximowiczii, P. polita, P. bicolor, P. koyamai, Abies firma, A. homolepis, Tsuga sieboldii, and Pinus), the present warm-temperate evergreen (laurilignosa) forest zone. Small populations of various broadleaf forest species were scattered in the full-glacial temperate conifer forest mainly along the coastal belt, and the true laurilignosa forest was limited in distribution, occurring only in the paleo-Yaku Peninsula.     

A subsurface Middle Wisconsinan interstadial site at Waterloo, Ontario, Canada

Commercial borings to a depth of 36 m encountered organic sediments under till. A continuously cored borehole was subsequently put down to 42 m and revealed a succession of sand and silt, over clayey Maryhill hill, over sandy Catfish Creek Till, over fossiliferous sand. Pollen, plant macrofossils, and a few ostracodes, molluscs, and insects provide a coherent picture of interstadial conditions. Two pollen zones are represented. The older zone is characterized by Picea and ThujalJuniperus pollen, and Dryopteris- type and Sphagnum spores, which suggest a lowland, forested peatland. Reduction of peatland, and transition to a wetland with more open water associated with a stream is indicated by an increase in Cyperaceae pollen, Pediastrum algae, and a diversity of aquatic plant macrofossils during the later zone. Fossil plant assemblages are similar to modern southern boreal associations in Ontario, which implies that the climate was cooler and possibly drier than the present. Phytogeographically, Picea needles and wood, and seeds of Brasenia schreberi and Potamogetan spirillus are noteworthy among the plant macrofossils. The sequence of Late Wisconsinan tills overlying the fossiliferous zone implies a Middle Wisconsinan age for the interstadial. This is supported by an accelerator radiocarbon date on small wood pieces of 40,080 + 1,200 years B.P.     

Post‐glacial vegetation reconstruction and a possible 8200 cal. yr BP event from the low arctic of continental Nunavut,Canada

Climate models suggest that the global warming during the early to mid‐Holocene may have partly resulted from the northward advance of the northern treeline and subsequent reduction of the planetary albedo. We investigated the Holocene vegetation history of low arctic continental Nunavut, Canada, from a radiocarbon‐dated sediment core from TK‐2 Lake, a small‐lake ca. 200 km north of the limit of the forest‐tundra. The pollen and loss‐on‐ignition data indicate the presence of dwarf shrub tundra in the region since the beginning of organic sedimentation at ca. 9000 cal. yr BP with dominance of Betula, especially since 8700 cal. yr BP. At 8100–7900 cal. yr BP the dominance of the shrub tundra was punctuated by a transient decline of Betula and coincident increases of Ericaceae undiff., Vaccinium‐type, and Gramineae. This suggests an abrupt disturbance of the Betula glandulosa population, approximately simultaneously with the sudden 8200 cal. yr BP event in the North Atlantic. However, in the absence of other sites studied in the area, linkage to the 8200 cal. yr BP event remains tentative. The lack of any evidence of forest‐tundra in the region constrains the northern limit of the mid‐Holocene advance of the forest‐tundra boundary in central northern Canada. Consequently, our results show that the climate models imposing a mid‐Holocene advance of the limit of the forest‐tundra to the arctic coast of Canada may have overestimated the positive climatic feedback effects that can result from the replacement of tundra by the boreal forest. Copyright © 2003 John Wiley & Sons, Ltd.     

Late Pleistocene and Holocene Afromontane vegetation and headwater wetland dynamics within the Eastern Mau Forest,Kenya

The Mau Forest Complex is Kenya's largest fragment of Afromontane forest, providing critical ecosystem services, and has been subject to intense land use changes since colonial times. It forms the upper catchment of rivers that drain into major drainage networks, thus supporting the livelihoods of millions of Kenyans and providing important wildlife areas. We present the results of a sedimentological and palynological analysis of a Late Pleistocene–Holocene sediment record of Afromontane forest change from Nyabuiyabui wetland in the Eastern Mau Forest, a highland region that has received limited geological characterization and palaeoecological study. Sedimentology, pollen, charcoal, X-ray fluorescence and radiocarbon data record environmental and ecosystem change over the last ~16 000 cal a bp. The pollen record suggests Afromontane forests characterized the end of the Late Pleistocene to the Holocene with dominant taxa changing from Apodytes, Celtis, Dracaena, Hagenia and Podocarpus to Cordia, Croton, Ficus, Juniperus and Olea. The Late Holocene is characterized by a more open Afromontane forest with increased grass and herbaceous cover. Continuous Poaceae, Cyperaceae and Juncaceae vegetation currently cover the wetland and the water level has been decreasing over the recent past. Intensive agroforestry since the 1920s has reduced Afromontane forest cover as introduced taxa have increased (Pinus, Cupressus and Eucalyptus).     

The Lateglacial and Holocene in Central Europe: a multi‐proxy environmental record from the Bohemian Forest,Czech Republic

The Hercynian mountain ranges were islands of mountain glaciation and alpine tundra in a Central European ice‐free corridor during the Late Pleistocene. Today they are notable areas of glacial landforms, alpine‐forest free areas, peatlands and woodlands. However, our knowledge of the Lateglacial and early Holocene environmental changes in this region is limited. We present a new multi‐proxy reconstruction of a mid‐altitude environment in the Bohemian Forest spanning this period. A core (5.2 m length) in the ?erné Lake cirque (1028 m a.s.l.) was subjected to lithological, geochemical, pollen and macrofossil analysis supplemented by two optically stimulated luminescence (OSL) and 10 AMS radiocarbon dates. We determined the impact of regional and supraregional climate changes on the environment. The two most significant changes in sedimentation during the Lateglacial (17.6 and 15.8–15.5 cal. ka BP) were synchronous with regional glacial chronostratigraphy. Unlike Central European mountain ranges, in the Bohemian Forest the Younger Dryas was not coincident with glacier re‐advance, but was a dry, cold episode with low lake levels, which prevailed until the early Preboreal. Plant macrofossils indicate local establishment of Betula nana and Betula pendula/pubescens at 15.4–13.4 cal. ka BP. Comparison with Holocene records from Central Europe shows a similar immigration history of vegetation at mid and higher altitudes. The tree line exceeded an altitude of ~1000 m a.s.l. around 10.5 cal. ka BP and coincided with rapid geochemical changes in the sediment. The 8.2 ka BP event did not have any response in the sedimentary record, but corresponded to stabilization of the Picea abies population and expansion of Fagus. Fagus colonized the Bohemian Forest earlier than other Hercynian mid‐mountains, but never predominated in the composition of the forest at higher elevations. Abies alba was the last tree species that immigrated to the study area.     

Geology and paleoecology of a mid-Wisconsin peat from the Queen Charlotte Islands, British Columbia, Canada

A peat bed on east-central Graham Island of the Queen Charlotte Islands occurs within a nonglacial fluvial succession that is both overlain and underlain by glacial deposits. Radiocarbon dates of 27,500 ± 400 and 45,700 ± 970 yr B.P. at the top and base of the peat, respectively, indicate that it was deposited during the mid-Wisconsin nonglacial interval. The peat is the first documented mid-Wisconsin organic deposit in northern coastal areas of British Columbia. Three local pollen zones are represented. The lowest zone (PM-1) is restricted to sandy silt directly underlying the dated peat. Very high Cyperaceae and moderate Poaceae pollen percentages characterize zone PM-1, and a variety of other herbs are common, suggesting an open landscape rather than a forested one. The middle zone (PM-2) is characterized by abundant pollen of Picea, Tsuga mertensiana, and Cyperaceae, and also contains pollen of Abies, a genus now absent from the Queen Charlotte Islands. Graham Island probably had extensive forests at this time, but abundant pollen and macrofossils of Cyperaceae and emergent aquatics such as Hippuris vulgaris, Veronica scutellata, Potentilla palustris, and Menyanthes trifoliata indicate that there also were open wetland areas. Zone PM-3 also contains abundant arboreal pollen. Large amounts of Sphagnum spores and Selaginella selaginoides megaspores indicate succession of the wetland area at the sample site to a peat bog. Paleoecological analysis of the data suggests that subalpine vegetation elements were depressed by at least 400 m, probably due to a cooler climate. Probable modern analogs in southeastern Alaska and the presence of Abies (probably A. amabilis) indicate that precipitation was higher on eastern Graham Island during the mid-Wisconsin than at present.     

A new Middle Pleistocene interglacial record from Denmark: Chronostratigraphic correlation,palaeovegetation and fire dynamics

Previously only three terrestrial interglacial periods were known from southern Scandinavia, all of which could be relatively easily correlated within the central European stratigraphical framework. Here, we present a new interglacial–interstadial pollen, plant macrofossil and charcoal record from Trelde Klint, Denmark, and analyse its biostratigraphy, correlation with other European records, vegetation development, fire dynamics and absolute dating. Except for a slight truncation of the early part of the record, the pollen stratigraphy exhibits a full interglacial succession, including temperate trees (Quercus, Ulmus and Tilia) during its mesocratic stage. Macrofossil analysis allowed identification to species level for Quercus robur, Picea abies and two mosses. Conifers (Pinus and Picea) dominate the pollen record of the interglacial sequence, and the occurrence of Larix pollen in the top part of the interglacial record as well as in the interstadial sediments is especially indicative of this interglacial. The overall diversity of tree genera is rather low. These biostratigraphical features suggest that Trelde Klint is unique among Danish records, but it is similar to records from northern Germany. Numerical analyses (REVEALS and DCA) indicate that forests during the temperate stage were dense and that vegetation openness increased only towards the end of the interglacial, accompanied by increased fire occurrence. A short interstadial sequence with a dominance of Pinus and Betula and the presence of Larix is present above the interglacial deposit. We argue that lack of attention to differences in fire regimes may hamper understanding of between‐site correlations of interglacial pollen records. OSL dating, using a novel feldspar technique, yields an average age of 350±20 ka for the sandy sediments above the interglacial layers at Trelde Klint, suggesting that the whole interglacial–interstadial succession belongs to Marine Isotope Stage 11.     

Strong correlation between summer temperature and pollen accumulation rates for Pinus sylvestris,Picea abies and Betula spp. in a high‐resolution record from northern Sweden

Highly resolved pollen spectra analysed from a 47 cm peat monolith recovered from a mire in northern Sweden exhibit climatic sensitivity in the pollen accumulation rates (PAR) of boreal treeline species. Robust temporal control, afforded through multiple AMS radiocarbon dating of the post‐atomic‐bomb‐test period (AD 1961–2002), provides a unique opportunity to compare pollen accumulation rates with the instrumental meteorological record. Strong correlations are observed between summer temperature and PAR for Pinus sylvestris, Picea abies and Betula spp. (excluding B. nana). Despite well constrained, contiguous (‘annual’) sampling, the temporal resolution of the pollen signal preserved within each sample appears to be degraded to ca. 3–5 year resolution. This is likely to reflect processes occurring during peat accumulation and pollen deposition, as well as dating uncertainties and the effects of subsampling. These findings identify limitations to the maximum resolution that may realistically be recovered from the peat archive using high‐resolution sampling protocols and AMS ¹⁴C dating. We also identify the need for additional work to quantify the role of climate on peat accumulation and the resultant impact on assemblage‐based palaeoenvironmental reconstructions within mire sequences. The strongest climate association observed for Picea abies (r = 0.53; n = 36) was extended through the monolith beyond the 42 year period of ‘annual’ sampling and the response successfully correlated with the Bottenviken historical instrumental record to AD 1860. Although only presenting data from a single site, and requiring wider replication, we conclude that for sites close to the ecological limits of tree species, where levels of anthropogenic/non‐climatic forcing on pollen production are low, well‐dated records of PAR may potentially provide a proxy for reconstructing past summer temperature variability. Copyright © 2007 John Wiley & Sons, Ltd.