Influence of human impact and bedrock differences on the vegetational history of the Insubrian Southern Alps

Vegetation history for the study region is reconstructed on the basis of pollen, charcoal and AMS¹⁴C investigations of lake sediments from Lago del Segrino (calcareous bedrock) and Lago di Muzzano (siliceous bedrock). Late-glacial forests were characterised byBetula andPinus sylvestris. At the beginning of the Holocene they were replaced by temperate continental forest and shrub communities. A special type of temperate lowland forest, withAbies alba as the most important tree, was present in the period 8300 to 4500 B.P. Subsequently,Fagus, Quercus andAlnus glutinosa were the main forest components andA. alba ceased to be of importance.Castanea sativa andJuglans regia were probably introduced after forest clearance by fire during the first century A.D. On soils derived from siliceous bedrock,C. sativa was already dominant at ca. A.D. 200 (A.D. dates are in calendar years). In limestone areas, however,C. sativa failed to achieve a dominant role. After the introduction ofC. sativa, the main trees were initially oak (Quercus spp.) and later the walnut (Juglans regia). Ostrya carpinifolia became the dominant tree around Lago del Segrino only in the last 100–200 years though it had spread into the area at ca. 5000 cal. B.C. This recent expansion ofOstrya is confirmed at other sites and appears to be controlled by human disturbances involving especially clearance. It is argued that these forests should not be regarded as climax communities. It is suggested that under undisturbed succession they would develop into mixed deciduous forests consisting ofFraxinus excelsior, Tilia, Ulmus, Quercus andAcer.     

Palynological investigations on vegetation and climate change in the Late Quaternary of Lake Rukche area,Gorkha Himal,Central Nepal

Palynological data and pedological investigations including stable isotopes and lignin biomarkers (Glaser et al. in press) from a 4 m core of Lake Rukche (3500 m a.s.l.) enhance our palaeoecological knowledge of the time since the LGM in the Gorkha Himal, Central Nepal. Even before 15000 B.P. forest types became established which prove the existence in Central Nepal of a temperate-humid climate with a considerable amount of winter and spring precipitation from westerly disturbances. Lignin input and pollen data point to a patchy vegetation cover around Lake Rukche with meadow-steppes dominated by Poaceae. Around 15000 B.P. Quercus and Pinus roxburghii dominated the lower altitudes while the vegetation around Lake Rukche was more steppe-like (Chenopodiaceae, Artemisia). Subsequently the climate became warmer and drier as winter and spring precipitation decreased while summer rain remained low. Later on more resource-demanding forests became established under improved temperature and precipitation conditions (Engelhardia). Around Lake Rukche coniferous forests (Abies, Picea) occurred beside meadow-steppes. The transition from the Pleistocene to the Holocene is not recorded. In the Holocene alpine Kobresia-meadows stabilised the soil surface causing sand accumulation to end. During the mid-Holocene (7800–2750 B.P.) humid oak forests with demanding elements (Ilex, Coriaria, Myrsine and Engelhardia) dominated the vegetation cover. A charcoal layer and a marked emergence of fire-induced communities with Pinus roxburghii, Poaceae, Ericaceae and Pteridium are proofs of a first strong anthropogenic change in vegetation which coincided with the climatic deterioration at the onset of the Subatlantic. Since 900 B.P. grazing pressure and the frequency of fires increased, resulting in a replacement of Betula utilis-forests by meadows and woods of Juniperus and Rhododendron. While previous anthropogenic influence increased the biodiversity by promoting replacement communities, recent developments have led to a decrease in biodiversity through loss of natural vegetation communities.     

Mid- and late-Holocene vegetation and fire history at Biviere di Gela, a coastal lake in southern Sicily, Italy

The vegetation and fire history of few coastal sites has been investigated in the Mediterranean region so far. We present the first paleoecological reconstruction from coastal Sicily, the largest island in the Mediterranean Sea. We analysed pollen and charcoal in the sediments of Biviere di Gela, a lake (lagoon) on the south coast of Sicily. Our data suggest that the area became afforested after a marine transgression at ca. 7200 cal b.p. (5250 b.c.). Build-up of forest and shrublands took ca. 200–300 years, mainly with the deciduous trees Quercus, Ostrya and Fraxinus. Juniperus expanded ca. 6900 cal b.p. (4950 b.c.), but declined again 6600 cal b.p. (4650 b.c.). Afterwards, evergreen trees (Q. ilex-type and Olea) became dominant in the forest and Pistacia shrublands were established. Forest and shrubland reached a maximum ca. 7000–5000 cal b.p. (5050–3050 b.c.); subsequently forest declined in response to human impact, which was probably exacerbated by a general trend towards a more arid climate. During the Neolithic, fire was used to open the landscape, significantly reducing several arboreal taxa (Q. ilex, Fraxinus, Juniperus) and promoting herbs and shrubs (Achillea, Cichorioideae, Brassicaceae, Ephedra). Final forest disruption occurred around 2600 cal b.p. (650 b.c.) with the onset of the historically documented Greek colonization. We conclude that the open maquis and garrigue vegetation of today is primarily the consequence of intensive land-use over millennia. Under natural or near-natural conditions arboreal taxa such as Q. ilex, Olea and Pistacia would be far more important than they are today, even under the hot and rather dry coastal conditions of southern Sicily.     

Long-term human impact as registered in an upland pollen profile from the southern Black Forest, south-western Germany

A detailed,¹⁴C-dated, pollen profile from Steerenmoos, a raised bog in the uplands of the southern Black Forest (Schwarzwald) is presented. The Late-glacial and early Holocene vegetation history conforms to the known pattern of forest dynamics for that region. At ca. 6100 cal. B.P.,Abies replaced the mixed oak forest, which is in contrast to adjacent regions whereFagus spread beforeAbies. From the Subboreal onwards,Fagus expanded and slowly largely replacedAbies. The mire developed from a fen to a raised bog. The mountain pine (Pinus mugo ssp.rotundata) on the present-day bog surface is a result of medieval burning. Cereal pollen are first recorded in the Neolithic (7600 cal. B.P.) and there is a closed curve forPlantago Lanceolata — a good indicator of human impact — since the Bronze Age (4000 cal. B.P.). On the basis of the cereal pollen record nine human impact phases (HIP) are described. HIP 1 and 2, which are short, date to ca. 7600 and 6700 cal. B.P., respectively, in a mixed oak forest context and are characterized by declines inCorylus, Tilia, Ulmus and bySalix (but no major deforestation) and peaks in charcoal and loss-on-ignition curves. HIP 3 and 4, which are short and weak, date to ca. 6000 and 5300 cal. B.P., respectively, and occur in the context of anAbies alba forest. The Bronze Age and Iron Age HIPs 5-7 are more intense and of longer duration than the Neolithic phases and result in a decline inAbies and an increase inFagus. The early medieval HIP 8, although rather weak, probably finds expression also in an archaeological artefact, namely a dug-out boat from the near-by Schluchsee. Finally, the late Medieval HIP 9 resulted in a major transformation in the landscape. It is argued that the earlier HIPs are not a reflection of distant events in the lowland valleys of the Rhine, Danube or Neckar but reflect more or less local developments.     

Fire and late-Holocene expansion of Quercus ilex and Pinus pinaster on Corsica

Abstract. The natural origin of old Quercus ilex (holm oak) forests on the west coast of Corsica is a matter of dispute. This paper discusses the use of pedoanthracology, especially adapted to approach topics in palaeoecology requiring a high spatial precision. It also shows the importance of fire in vegetation change during the Holocene. Pedoanthracology relies on botanical identification and AMS ¹⁴C dating of micro-charcoal found in soil. Three test pits were dug in a forest currently protected within the ‘Man and Biosphere’ program. These pits yielded large quantities of charcoal. There is evidence that Pinus nigra ssp. laricio (laricio pine) and understorey heather species (Ericaceae) played an important role in the vegetation at the beginning of the Subatlantic (ca. 2500 BP). The importance of Pinus pinaster (maritime pine), Quercus ilex and a few mesophilic species increased between 2000 and 1000 BP. Charcoal fragments found in the soil show the role of fire in the vegetation changes recorded. The late expansion of P. pinaster results from a high fire frequency. The hypothesis proposed in the paper suggests that fires destroyed the remaining toxic humus that had accumulated during the millennia which preceded the arrival of Q. ilex to our study sites. The late development of holm oak forest is a combination of the migration of the species and the increase of fire frequency since 2500 BP, most probably resulting from slash-and-burn agriculture.     

Vegetation history,climate and human impact over the last 15,000 years at Lago dell’Accesa (Tuscany,Central Italy)

Interdisciplinary studies of the sediments of Lago dell’Accesa started in 2001. We present here results from the palynological study. The pollen diagram provides a record of vegetation and climatic change spanning over 15,000 years. The oldest pollen spectra show a late-glacial steppe vegetation typical of central and southern Italy during this period. The Late-glacial Interstadial, interrupted by two cooling events, is dominated by open deciduous oak forests. The Younger Dryas is represented by 150 cm of sediment and shows the presence of steppic vegetation. The Holocene vegetation is characterised by alternating dominance of deciduous oaks and Quercus ilex. The three zones characterised by Q. ilex are accompanied by peat layers marking lake-level lowering at ca. 8600–7900, 4600–4300 and 3700–2800 cal b.p. Between approximately 9000 and 6000 cal b.p. extensive Abies-forests existed on the Colline Metallifere located 15–20 km to the north and northeast of the lake. Local fir populations may also have existed by the lake. Human impact starts at approximately 8000 cal b.p. during the Neolithic period, and increases at ca. 4300 cal b.p. Castanea and Juglans pollen is recorded from ca. 2800 cal b.p. The impact of the Etruscan settlement near the lakeshore is shown in the increasing values of arable crops, species of secondary forest canopy (Ericaceae, Pinus, Pistacia, Myrtus) and anthropogenic indicators (Chenopodiaceae, Plantago lanceolata, Rumex etc).     

Middle to Late Holocene vegetation history of the Upper Engadine (Swiss Alps): the role of man and fire

To reconstruct the vegetation and fire history of the Upper Engadine, two continuous sediment cores from Lej da Champfèr and Lej da San Murezzan (Upper Engadine Valley, southeastern Switzerland) were analysed for pollen, plant macrofossils, charcoal and kerogen. The chronologies of the cores are based on 38 radiocarbon dates. Pollen and macrofossil data suggest a rapid afforestation with Betula, Pinus sylvestris, Pinus cembra, and Larix decidua after the retreat of the glaciers from the lake catchments 11,000 cal years ago. This vegetation type persisted until ca. 7300 cal b.p. (5350 b.c.) when Picea replaced Pinus cembra. Pollen indicative of human impact suggests that in this high-mountain region of the central Alps strong anthropogenic activities began during the Early Bronze Age (3900 cal b.p., 1950 b.c.). Local human settlements led to vegetational changes, promoting the expansion of Larix decidua and Alnus viridis. In the case of Larix, continuing land use and especially grazing after fire led to the formation of Larix meadows. The expansion of Alnus viridis was directly induced by fire, as evidenced by time-series analysis. Subsequently, the process of forest conversion into open landscapes continued for millennia and reached its maximum at the end of the Middle Ages at around 500 cal b.p. (a.d. 1450).     

Response of broadleaved evergreen Mediterranean forest vegetation to fire disturbance during the Holocene: insights from the peri-Adriatic region

Aim To test whether fire contributed to the expansion and compositional change of evergreen forests in the Mediterranean region during the Holocene. Location The peri‐Adriatic region, encompassing the Italian peninsula, Sicily and the western and southern Balkans between latitudes 46° and 37° N. Methods New high‐resolution pollen and microscopic charcoal data from Lago dell’Accesa (Tuscany, Italy) were used to estimate the response of the evergreen oak, Quercus ilex L., to fire during its expansion phase at 8500 cal. yr bp . The data were compared with the pollen and charcoal series from other Mediterranean sites (Lago di Massaciuccoli in Tuscany, Malo Jezero in Croatia, Biviere di Gela in Sicily) and analysed using numerical techniques (redundancy analysis, detrended canonical correspondence analysis) to identify long‐term fire–vegetation linkages and the degree of compositional change. Results Microscopic charcoal and pollen of evergreen oaks were negatively correlated during the period of quasi‐natural fire regime (Mesolithic, 10,000–8000 cal. yr bp ). In addition, there was no such positive correlation during periods when the fire regime was potentially more influenced by people (Neolithic–Bronze Age, 8000–3000 cal. yr bp ). Compared with inland sites, coastal sites that are currently located at a distinct ecotone showed more compositional change. Main conclusions The analyses suggest that climatic change, without an additional effect of fire regimes, favoured the expansion and compositional change of evergreen forests across the peri‐Adriatic region. Strikingly different patterns occurred along a north–south gradient. In the north (Tuscany and Croatia, meso‐Mediterranean belt), Q. ilex replaced deciduous forests when conditions became drier; in the south (Sicily, thermo‐Mediterranean belt) the species replaced maquis or steppe vegetation when climatic conditions became moister. We conclude that the projected increase in fire activity may lead to the loss of most of the remaining relict forests of Q. ilex in southern Europe.     

Predicting the Recovery of <Emphasis Type="Italic">Pinus halepensis</Emphasis> and <Emphasis Type="Italic">Quercus ilex</Emphasis> Forests after a Large Wildfire in Northeastern Spain

Quercus ilex and Pinus halepensis are two of the most common tree species of the western Mediterranean basin. Both species regenerate reliably after fire: P. halepensis colonizes recently disturbed areas by effective seedling recruitment, while Q. ilex resprouts vigorously after disturbances. For this reason, the natural regeneration of these species after fire should ensure the re-establishment of a forest similar to that which existed before the fire. This study analyzes with a simple simulation model whether or not the relative abundance of monospecific and mixed forests of these species in the landscape is altered by fire. We also analyze the topographic factors and the forest structure before the fire that determine the changes in forest composition after fire. This study has been carried out in a large fire that occurred in NE Spain. Overall, 33% of plots changed to another community type, but this probability of change varied considerably among community types before the fire. Monospecific forests of P. halepensis or Q. ilex had a high probability of remaining in their original composition after the fire, whereas the resilience of mixed forests of these two species was quite low. Mixed forests changed for the most part to monospecific P. halepensis or Q. ilex forests. Analysis of several factors determining these changes indicated that only elevation as a significant topographical variable. The effect of fire was to increase the altitudinal differentiation between the two species. P. halepensis forests that changed to mixed or Q. ilex forests were those of highest elevation, while the mixed and Q. ilex plots that changed to P. halepensis forests were those located at the lowest elevations. Concerning structural variables before fire, density of Q. ilex trees before the fire showed a much greater effect than P. halepensis density in determining the post-fire community. Finally, burn severity also influenced the changes observed. For both P. halepensis and Q. ilex forests, plots that changed to another forest type were mainly those that burned more severely. In the case of mixed forests, even low fire severities involved high probabilities of change to monospecific forests.     

Towards the vegetation and settlement history of the southern Dobrudza coastal region, north-eastern Bulgaria: A pollen diagram from Lake Durankulak

Palynological investigation and radiocarbon dating of a 6-m core from lake Durankulak, north-eastern Bulgaria, enables vegetation development and human occupation from ca. 5500–5300 cal. B.C. onwards to be traced. Steppe vegetation that included with groves of deciduous trees asQuercus, Ulmus, Carpinus belulus andCorylus changed to a forest-steppe after 4000 cal. B.C. The archaeopalynological record indicates three distinct phases of human activity as follows: (1) 5300–4200 cal. B.C. (late Neolithic and Eneolithic) during which farming, that included a substantial arable component, was pursued, (2) 3500–3000 cal. B.C. (transition to early Bronze Age) when stock rearing appears to have dominated, and (3) after 1300 cal. B.C. (late Bronze Age) when arable farming again assumed importance. The palynological data correlate well with the rich archaeological record for human settlement that is available for the region from late Neolithic times onwards.     

Reconstruction of environment and history of plant use during the late Mesolithic (Ertebølle culture) at the inland settlement of Bökeberg III,southern Sweden

Pollen, plant macrofossils and charcoal were analysed from a lake-sediment sequence, including a refuse layer, from the Late Mesolithic settlement at Bökeberg III, southern Sweden. The chronology was established by means of AMS-dated plant macroremains. The results of the biostratigraphical studies indicate two settlement phases (A and B), at ca. 6650-6400 B.P. (5560-5320 cal. B.C.) and ca. 6150-5800 B.P. (5200-4680 cal. B.C.), respectively. The two settlement phases are associated with periods of low lake-level contemporaneous with the second major period of low lake levels during the Holocene in southern Sweden, and thus with a period of generally drier climate. The pollen analytical data suggest only minor human impact on the local vegetation during the two settlement phases. Three elm declines at ca. (1) 6200 B.P. (5200-5100 cal. B.C.), (2) 5450 B.P. (4340 cal. B.C.), and (3) 5150 B.P. (3980 cal. B.C.) are discussed. Elm decline 3 is synchronous with the classical north-west European elm decline. Elm declines 2 and 3 may be due to outbreaks of elm disease rather than to strong human impact or climate change. The charcoal analyses show that wood of a wide range of species was collected for fuel or other purposes. During phase A, plants used included acorns, hazelnuts and, possibly, Cornus sanguinea, and also Prunus spinosa, Sorbus aucuparia and Rubus idaeus. There is convincing evidence that Cladium mariscus was used for thatching. The second occupation phase, B, is characterised by the use of hazelnuts for food. The possible use of several other identified species is discussed.     

Effects of germination inhibition on the dynamics of Quercus ilex stands

Abstract. Germination of Quercus ilex L. in coppice stands of this species in the western Mediterranean Basin was examined and a germination inhibitory process is proposed to explain some germination traits. Germination rate and seedling biomass of Q. ilex were greatly modified by watering acorns with various concentrations of aqueous soil extracts from a Q. ilex coppice stand but also when the acorns were sown in soil from Q. ilex coppice stands. In the aqueous extract experiment, Q. ilex germination and seedling weight both decreased as the aqueous extract concentration increased. In the soil type experiment, Q. ilex soil decreased the Q. ilex germination rate. Comparative studies with Q. pubescens germination (this species, replaced by Q. ilex around 5 000 B.P., is assumed to form the climax vegetation of the region) revealed that Q. pubescens was less sensitive to the aqueous extracts and soils of Q. ilex coppice stands. Inhibition of Q. ilex seed germination could be a major reason for the poor seed regeneration and suggested a possible comeback of Q. pubescens.     

The effects of chemicals on the phenotypic expression of aVestigial mutant inDrosophila melanogaster

Several kinds of chemicals were tested to determine their effects on the wings of avestigial mutant inDrosophila melanogaster. Two isogenic strains were used, viz.vg-ms andB; vg-ms, both co-isogenic with the Oregon-isogenic strain. Ammonium lactate was found to have a conspicuous effect in enlarging thevestigial wings. At an appropriate concentration of this agent the wings of thevg-ms- andB;vg-ms-co-isogenic strains were restored almost to wild-type wing at 27°C. This fact indicates that the wings of thevg-ms mutant can be restored to wild type not only by temperature but also by certain chemicals. Ammonium lactate was effective conspicuously on bothBar andvestigial-ms mutants. However, there was found an interaction betweenBar andvestigial-ms when these genes were combined. The manifestation ofB is enhanced byvg-ms, especially under the the condition of feeding in medium containing the chemical, and the manifestation ofvg-ms is reduced byB.This work forms part of a thesis for the doctorate of Kyoto University.     

On the Holocene vegetation history of the Argive Plain (Peloponnese,southern Greece)

Palynological investigations have been carried out on a sediment core from ancient Lake Lerna, a former fresh water lagoon in the western part of the Argive plain, Peloponnese, southern Greece. The sequence starts at 6800 B.P. (5700 cal B.C.). The lowest part of the pollen diagram shows a period of open deciduous oak woods, which may have been influenced by human impact already (Zone I). It is followed by a period of dense deciduous oak woods (Zone II), which lasted until the beginning of the Bronze Age ca. 4800 B.P. (3500 cal B.C.). Later, the diagram indicates strong human influence such as woodland clearance, the spread of maquis, phrygana and pine in Zones IIIa-IV. During the Archaic, Geometric and Classical periods after ca. 2700 B.P. (800 cal B.C.) there is evidence of a phase of extensive olive farming (Zone IIIb). In the same zone, after a period of scattered finds, there is an almost continuous Juglans curve. Zone IV is characterised by high pine values. In Zones I-II the evidence of evergreen Mediterranean plants is surprisingly small. In times with no discernible human influence (Zone II), deciduous oaks dominate, with no evidence for a climax vegetation of the Oleo-Ceratonion alliance. Olea europaea is the only species of that alliance traceable by its pollen in the diagram, while Ceratonia pollen is totally absent.     

Vegetation history since the last glacial period in the Mikata lowland,the Sea of Japan area,western Japan

Local and regional vegetation since the last glacial period was reconstructed on the basis of a palynological study of sediment at Iwaya, in the Sea of Japan area, western Japan. During the interstade (before about 30 000 years BP), forests were composed predominantly ofCryptomeria japonica withTsuga sieboldii and cool-temperate deciduous broad-leaved trees. In the pre-full-glacial, the full-glacial and the early late-glacial (30 000-12 000 years BP), forests were dominated by temperate (montane) and boreal (subalpine) Pinaceae andBetula. During the early full-glacial, the pinaceous forests were mixed with cool-temperate trees such asFagus crenata. In the late full-glacial (18 000-16 000 years BP), the maximum development of pinaceous conifer forests was recognized. Cool-temperate broad-leaved forests composed mainly ofF. crenata andQuercus (Lepidobalanus) replaced the pinaceous forests at about 12 000 years BP and were maintained to the early postglacial.Cryptomeria japonica was distributed around the Mikata lowland during the last glacial.Cryptomeria japonica, which began to increase at 16 000 years BP, increased abruptly in the early postglacial and spread throughout the postglacial in the lowlands. After 6300 years BP, lucidophyllous forests composed mainly ofQuercus (Cyclobalanopsis) andCastanopsis were established in the Mikata district; this was later than in the inland and the Pacific Ocean areas in the Kinki region, western Japan. In historic times (afterca 2000 years BP), secondary forest ofPinus densiflora, which can grow as a pioneer in disturbed habitats, spread.     

The composition,structure and distribution of heathland and grassland communities in the subalpine tract of the Bogong High Plains,Victoria

In the subalpine tract of the Bogong High Plains (37°S, 147°E; altitude 1600–1800 m a.s.l.) the vegetation consists of a mosaic of snow gum (Eucalyptus pauciflora) woodland, heathland, grassland and wetland communities. Classification (polythetic-agglomerative) and ordination (principal co-ordinates analysis) of quadrat data from heathlands and grasslands on relatively well drained sites allowed the identification of four main heathland and grassland vegetation units. These units may be ranked in a structural and floristic continuum, from closed heath variously dominated by Prostanthera cuneata, Orites lancifolia and Phebalium squamulosum to closed heath dominated by P. squamulosum and Grevillea australis, open grassy heath of G. australis and Poa hiemata. and grassland of P. hiemata. The transition from Prostanthera closed heath to Poa grassland is correlated with gradients of decreasing steepness and rockiness of terrain, and increasing exposure and frost.     

Effects of a severe drought on Quercus ilex radial growth and xylem anatomy

We assessed the response of Quercus ilex subsp. ballota to the severe summer drought recorded in 1994 in NE Spain through the study of changes in radial growth and wood anatomy. We selected a coppice stand in the Iberian Peninsula, which is characterized by a Mediterranean climate under continental influence. We measured internode length, tree-ring width, mean and maximum vessel diameter, and vessel density for 1981–1997. The annual predicted hydraulic conductance (K_h) was calculated following Hagen-Poisseuille's law. We compared the tree-ring width, vessel diameter and K_h of Q. ilex subsp. ballota and co-existing ring-porous oaks (Q. faginea, Q. pyrenaica) for a dry summer (1994) and a wet summer (1997). To evaluate the drought-resistance of xylem for Q. ilex subsp. ballota (dominant under continental conditions) and Q. ilex subsp. ilex (dominant in mild areas) we determined vulnerability curves. Dimensionless indices of internode length, tree-ring width, and vessel density were compared with climatic data (monthly total precipitation and mean temperature) using correlation analyses. Internode length, tree-ring width, K_h, and mean and maximum vessel diameter declined in 1994. According to vulnerability curves, Q. ilex subsp. ballota showed a greater drought resistance than Q. ilex subsp. ilex. During the year of growth, we found a positive influence of January and June–August precipitation on the internode length, tree-ring width, and vessel density. The response of Q. ilex subsp. ballota radial-growth to summer drought was comparable to that of Q. faginea latewood. Overall, growth and wood anatomy of Q. ilex subsp. ballota showed a plastic response to drought.     

Late-glacial and Holocene vegetation history of the Magellanic rain forest in southwestern Patagonia,Chile

A ¹⁴C-dated high-resolution palaeoenvironmental record from a mire in southern Chile is used to reconstruct the Late-glacial and Holocene vegetation history of the Magellanic rain forest. The Late-glacial environment after around 15400–13500 cal b.p. was dominated by Gunnera magellanica, Nothofagus species (dombeyi type) and Gramineae (Poaceae) indicating an open parkland with cool and damp climatic conditions. At the end of the Late-glacial there was an increase in G. magellanica and a decline in Nothofagus dombeyi type. This ecological signal is interpreted as a result of a re-advance of the Gran Campo Nevado icefield, caused by either Younger Dryas cooling or a latitudinal shift of the southern Westerlies. After around 11250–10750 cal b.p. Nothofagus species, Drimys winteri and Embothrium coccineum expanded, indicating development of the Magellanic rain forest. At 4254±120 cal b.p. a tephra layer was deposited by the eruption of the Mt. Burney volcano leading to a long-term decline of the Nothofagus forest. A primary succession was then initiated, lasting for over 800 years before pre-eruption vegetation patterns redeveloped. In summary, our results indicate the extreme sensitivity of the Magellanic rain forest to climatic or volcanic impacts and the slow recovery of a mature forest after environmental changes.     

Holocene vegetation and land-use history in the environs of Lake Kahala, northern Estonia

Pollen profiles, based cores taken in Lake Kahala and from the adjoining mire, were used to establish general vegetation history and to reconstruct the extent and types of land-use over most of the Holocene. Modern pollen deposition was studied using moss polsters and the results were used in the interpretation of the fossil pollen data in terms of former land-use practices. The modern-day samples are from settlements, hay meadow and pasture, and overgrown pasture. Indications of human activity can be traced back to the Stone Age. At ca. 6400 cal. B.C., the first indications of possible woodland utilisation by humans are recorded. This may have involved grazing within the forests. From 4200 cal. B.C. onwards, animal husbandry with changing intensity was practised. Arable farming, involving cereals, was introduced to the area at ca. 1800 cal. B.C., but it was only at ca. 500 cal. B.C. that it assumed an important role in the farming economy.Secale cereale (rye) was introduced during the Roman Iron Age, intensive rye cultivation started at the end of the Iron Age, at ca. cal. A.D. 800. Ever increasing farming pressures triggered the formation of openalvars. Open landscape similar to that of today has persisted, with minor forest regeneration phases, since at least 500 cal. B.C.     

Late Holocene mangrove dynamics of Marajó Island in Amazonia,northern Brazil

Two sediment cores from the eastern coastal region of Marajó Island, Pará State, northern Brazil have been studied by pollen analysis to reconstruct late Holocene mangrove dynamics and environmental changes. Seven AMS radiocarbon dates provide time control. Mangrove vegetation became established at the Barra Velha site at about 2750 B.P. (2880 cal B.P.) and at the Praia do Pesqueiro site at about 650 B.P. (670 cal B.P.). Rhizophora was the dominant mangrove tree throughout the recorded period, while Avicennia and Laguncularia were rare. Existing remnants of the former coastal Amazon rain forest were replaced by mangrove in the Barra Velha area between about 2750 and 740 B.P. (2880–760 cal B.P.) and at Praia do Pesqueiro area between about 650 and 530 B.P. (670–540 cal B.P.), suggesting a rise in relative sea level or, alternatively, an increase in discharge from the river Amazon. Areas of coastal shrub and herb vegetation, the so-called restinga vegetation, also became slightly reduced during the late Holocene. The largest area of mangrove at the two sites suggests that the highest sea level was probably reached during the last 200–250 years. The only evidence of human activity at the two sites is an indication of cattle pastureland at the Barra Velha area during the last decades.