Pollen analysis from two littoral marshes (Bourdim and Garaat El-Ouez) in the El-Kala wet complex (North-East Algeria). Lateglacial and Holocene history of Algerian vegetation

The study of two pollen sequences from El-Kala marshes allowed the reconstruction of the regional vegetation history supported by eight radiocarbon dates. Pollen assemblages from Bourdim site were dominated by local input of Alnus and Salix, while regional vegetation was characterized by scattered Quercus suber forests with a well-developed Erica arborea matorral. While the vegetation dynamics recorded at Bourdim is recent (Late Holocene), the majority of the pollen diagram from Garaat El-Ouez is contemporaneous to the Late Pleniglacial and is characterized by open woodlands with Pinus, Poaceae and several heliophilous herbs. The significant values of Cedrus pollen identified in this period indicate that the region of El-Kala most probably played the role of a refugium for this tree.     

Late-glacial and early Holocene climatic events and chronology of vegetation development in the Netherlands

The Weichselian Late-glacial marks the transition from the Weichselian Late Pleniglacial to the warmer Holocene. During this period climate changed rapidly, as did vegetation and the abiotic landscape. For analysis of the relationship between these changes, accurate chronologies are essential. In the Netherlands, a compilation has been made of over 250 palynologically investigated sites relating to this period. A regional zonation has been constructed based on common trends in vegetation development. On palynological grounds, not only the classical Late-glacial sub-division but also minor changes can be recognized within the Allerod, Late Dryas and Early Preboreal. After a critical evaluation of the available radiocarbon dates this zonation has been attached to the¹⁴C timescale. Palynological changes which can be attributed to episodes of climatic cooling are recorded at 12 100, 11 500, 10 950 and 9950 B.P. The chronological framework made it possible to compare vegetation development with other proxy records. Climatic events recorded in oxygen-isotope records from Swiss lake sediments and the Greenland ice cores are also reflected in the regional vegetation development in the Netherlands. The regional trends in vegetation development expressed by the pollen zones are considered to be related to changes in climate, while anomalies reflect other, local environmental changes.     

Investigations into the late Pleistocene and Holocene history of vegetation and climate in Santa Catarina (S Brazil)

Palynological studies have been carried out on three highland peat bogs, and one situated on the Atlantic coastal plain. In the highlands, the late Pleistocene (14,000 - 10,000 uncal B.P.) vegetation was dominated by campos (grassland). Scattered stands of Araucaria forests were preserved in deep valleys. In the region of the sites at Morro da Igreja and Serra do Rio Rastro, the dominance of campos vegetation continued until about 1000 B.P. while at the Serra da Boa Vista site there was an expansion of Atlantic pluvial forest elements followed by Araucaria forests at the beginning of the Holocene. A general expansion of A. angustifolia, clearly related to a change towards an increasingly moist climate, can be dated to the present millenium. On the coastal plains, the late Pleistocene vegetation was dominated by Myrtaceae which were replaced by tropical taxa in the Holocene. The lowland profile (Poço Grande) also covers part of the upper Holocene, where the rich flora of the Atlantic pluvial forests can be characterized by taxa including Alchornea, Urticales and Rapanea. Close to the coring site, there was a repeated alternation between two different dune communities (4840 - 4590 B.P.), followed by a lake stage with aquatic plant succession (4590 - 4265 B.P.), plant communities dominated by Rapanea (4265 - 4230 B.P.) and the spread of Alchornea (4230 - 3525 B.P.). Late Pleistocene climate conditions (14,000 - 10,000 B.P.) can be described as cold and relatively dry, possibly including an equivalent of the Younger Dryas period. In the Holocene, there were changes from a warm and drier climate (10,000 -3000 B.P.) to a cool and more moist regime (ca. 3000 -ca. 1000 B.P.) and finally to a cool and very moist period (from around 1000 B.P.).     

A high-resolution Late-Glacial – Holocene pollen diagram from Pian di Gembro (Central Alps, Northern Italy)

The local and regional history of vegetation and climate, from the Late Glacial to the present, is represented in a new, high-resolution pollen diagram from Pian di Gembro (1350 m asl), ten ¹⁴C dates providing a reliable time control. An open pioneer vegetation dominated by Artemisia, Gramineae, and and Chenopodiaceae followed the retreat of the glaciers after the Last Glacial Maximum. Shrub vegetation with Juniperus, Alnus viridis, and Salix expanded soon after. Denser Betula-Pinus forests were present in Pian di Gembro around 12,320 B.P. Their extent was greatly reduced by the climatic cooling of the Younger Dryas, when open vegetation spread again. The beginning of the Holocene was marked by a considerable expansion in mixed oak taxa. Corylus immigrated to the site at 9,250 B.P. Picea and Abies expanded at 7,370 B.P., recording an abrupt change in the structure of the vegetational belts. A coeval climatic change is evidenced in the GRIP records and also detectable through oscillations of the timberline. Signs of human impact are present since late Atlantic, becoming more intense around 2,200 B.P. As pasture lands increased, Abies and Fagus slowly disappeared. The introduction of Castanea and Juglans is dated to Roman times, and Secale to the Middle Ages. Received February 4, 2002 / Accepted August 2, 2002     

Vegetationsverhältnisse und Naturumwelt des Beckens Jestřebská kotlina am Ende des Spätglazials und im Holozän (Doksy-Gebiet)

The method of pollen analysis was used to study a profile sample taken from the Jest?ebské blato mire, the Doksy District (northern Bohemia). The aim of the palacobotanical analyses was to perform a reconstruction of vegetation and environment for geobotanical and archaeological research purposes. Sediments dating back to the end of the Late Glacial and to both the Early and Middle Holocene were pollenanalytically studied. The results of the pollen analyses recorded the development of vegetation during the end of the Late Glacial, Preboreal, Boreal and Atlantic Periods. Parkline pine stands of the end of the Late Glacial developed to closed pine forests, during the Preboreal. Even during the Boreal, the dominant pine formed forest communities were typical of the area under study, though trees with greater demands on temperature and moisture conditions continued to penetrate the existing communities. During the Lower and the first half of the Upper Atlantic Period, spruce forests and alder woods formed the dominant forest communities in mire. Nevertheless,Pinus was still dominant on extreme sites (both from the edaphic and geomorphological points of view). An early occurrence ofAlnus andPicea is another characteristic feature of the studied area. The conclusions drawn from pollenanalytical results were used for the reconstruction of the past environment of the Mesolithic and Neolithic Ages.     

A 10,000-year temperature record from Gotland,Sweden

The sediment of Lake Tingstdäde Träsk, a shallow Chara-dominated lake onm the island of Gotland in the middle of the Baltic, was analyzed as to its ^1*O and ¹³C content. The lake carbonate (Chara lime) was precipitate due to the assimilation of CO₂ by Chara during the summer months. The isotope curves give a very detaile record of the temperature fluctuations from 10, 700 to 1000 B.P. The depth scale was converted to absolute age via numerous identified levels. The ¹⁸O curve was converted to temperature (mean summer temperature of the lake) via the relation between measured lake temperature and corresponding isotopes composition of the water. The corresponding mean air temperature was calculated. The temperature record shows: (1) a low temperature during the Younger Dryas Stadial: (2) a very rapid rise at the Pleistocene/Halocene Halocene boundary; (3) a rapid rise through the early Holocene with present-day values reached at about 9, 300 B.P.; (4) a Holocene optimum of 1.5-1.2°C higher temperature than today, ending with a 2°C temperature fall at the Subboreal/Subatlantic transition at about 2500 B.P.; and (5) a fluctuating Holocene temperature with warm and cold peaks at the same chronological levels as known eustatic and global climatic fluctuations.     

Modelling Mediterranean oak palaeolandscapes using the MaxEnt model algorithm: The case of the NE Iberia under the Middle Holocene climatic scenario

The Mediterranean Basin is a global biodiversity hotspot, and oak tree species play an important role in it. Since the beginning of the Holocene (∼11.4 kyr BP), the distribution of forests has not occurred uniformly, resulting in diverse types of vegetation landscapes. In this study, we used a maximum entropy algorithm (MaxEnt) to obtain the ecological niche model (ENM) of two sub-Mediterranean oak species, Quercus pubescens Willd. (pubescent oak) and Quercus ilex subsp. ilex (holm oak), both in the present day in the Iberian Peninsula and within a Middle Holocene (8.2–4.2 kyr BP) climatic scenario in the NE Iberian Peninsula. Moreover, we used the locations of Neolithic archaeological sites containing anthracological data to analyze the relationship between human occupations and oak habitats. Our results suggest that the two oaks have responded differently to the climatic conditions that have occurred, and show changes in both potential distributions. The palaeolandscape vegetation map shows a denser vegetation cover in the lowlands and a more open landscape in the highlands, with a higher dominance of Quercus pubescens in the septentrional areas, while Quercus ilex was more restricted to certain coastal areas. Temperature and precipitation factors, mainly seasonal climatic conditions, have had a greater impact on the distribution of vegetation than other factors. We found a good overlap between the ENM of the two oaks and the locations of the Neolithic sites analysed, and determined that the distribution of Neolithic archaeological sites is not random. The Neolithic populations in the study area depended heavily on the resources of the deciduous and evergreen sub- Mediterranean forest, although they also exploited the resources of the mountain pine forest. Neolithic sites distribution suggests that Neolithic human groups were aware of the potential of forests and probably gathered woody resources in their surroundings.     

Vegetation history and lake-level changes from the Younger Dryas to the present in Eastern Pyrenees (France): pollen, plant macrofossils and lithostratigraphy from Lake Racou (2000 m a.s.l.)

A multi-proxy palaeoecological investigation including pollen, plant macrofossil, radiocarbon and sedimentological analyses, was performed on a small mountain lake in the Eastern Pyrenees. This has allowed the reconstruction of: (1) the vegetation history of the area based on five pollen diagrams and eight AMS¹⁴C dates and (2) the past lake-level changes, based on plant macrofossil, lithological and pollen analysis of two stratigraphical transects correlated by pollen analysis. The palaeolake may have appeared before the Younger Dryas; the lake-level was low and the vegetation dominated by cold steppic grasslands. The lake-level rose to its highest level during the Holocene in the Middle Atlantic (at ca. 5060±45 b.p.). Postglacial forests (Quercetum mixtum and Abieto-Fagetum) developed progressively in the lower part of the valley, while dense Pinus uncinata forests rapidly invaded the surroundings of the mire and remained the dominant local vegetation until present. The observed lowering of the lake levels during the Late Atlantic and the Subboreal (from 5060 ± B.P. to 3590±40 b.p.) was related to the overgrowth of the mire. The first obvious indications of anthropogenic disturbances of the vegetation are recorded at the Atlantic/Subboreal boundary as a reduction in the forest component, which has accelerated during the last two millennia.     

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.     

First report on new evidence for the occurrence of Podocarpus and possible human presence at the mouth of the Amazon during the Late-glacial

Palynological studies on late Quaternary lake sediments from the region of the Amazon estuary, 100 km north-east of Belém, Pará State, Brazil, enable reconstruction of lowland Amazonian rain forest during the Late-glacial and Holocene periods. Late-glacial forests included populations of Podocarpus which suggests a distinct climatic cooling. Ilex was abundant in the early Holocene. Records of the mangrove taxon, Rhizophora, indicate rapid Atlantic sea-level rise in the beginning of the Holocene. High charcoal representation may reflect the first arrival of Amerindians in the Amazon coastal area, probably about 10 800 B.P.     

Holocene vegetation and water level history in two bogs of the Cordillera de Talamanca, Costa Rica

Pollen records of Holocene sediment cores from the Costa Rican Cordillera de Talamanca (La Chonta bog, 2310 m and La Trinidad bog, 2700 m) show the postglacial development of the montane oak forest zone from ca. 9500 to 1500 yr BP. During the early Holocene (ca. 9500–700 yr BP), alder vegetation covered the La Chonta and La Trinidad bogs and their adjacent hills. The upper forest line is inferred to be at 2800–3000 m elevation. A Podocarpus-Quercus forest characterised the middle Holocene (ca. 7000–4500 yr BP). The upper forest line is located at >3000 m reaching the present-day altitudinal distribution. A Quercus forest characterised the late Holocene (ca. 4500–1500 yr BP). Compared to modern conditions, the early Holocene has similar average temperatures, but the moisture level was probably higher. Pollen evidence for the late Holocene indicates drier environmental conditions than today. In order to improve the paleoecological interpretation, we described the local vegetation and used moss samples as pollen traps at both montane bogs along strong soil moisture gradients.The Netherlands Centre for Geo-ecological Research, ICG     

The Holocene and Upper Pleistocene pollen sequence of Carihuela Cave, southern Spain

A new pollen sequence (ca. 15,700-1250 yr BP) is presented for three stratigraphical sections of Carihuela Cave (Granada, southeastern Spain), thus completing a record that covers from the last Interglacial to late Holocene. The Late Glacial is characterized by open landscapes with junipers and early colonisation of Quercus, while the Holocene is depicted by mixed oak forests, with a diversity of broad-leaf trees and scrub, which decrease after ca. 5470 yr BP synchronously with the expansion of xerophytes and occurrence of indicators of anthropogenic disturbance. The whole pollen record of Carihuela fits into the general trends described for reference pollen sites of southern Europe, including Padul in the province of Granada, and other sequences from Mediterranean Spain, through which the heterogeneity of environmental change increases from mid to late Holocene. We conclude that, in contrast with other regions of Spain, deciduous Quercus-dominated forests are very old in eastern Andalusia, thus conflicting with floristic phytosociological models of vegetation change that imply that monospecific Q. ilex/rotundifolia woodlands are the potential mature forest in the region. Dating results suggest that the last Neanderthals of Carihuela lived between ca. 28,440 and 21,430 yr BP, which agrees with the postulation that southern Spain was the latest refugium for this human species in Europe.     

Late Quaternary vegetation history of the Mexican highland

Results of pollenanalytical investigations in the Highlands of Mexico (area of Puebla — Tlaxcala) are presented together with a survey of the last 35 000 years of vegetation history. After 3 pine periods from 35 000 to about 7 000–8 000 B. P., according to high and late Pleistocene condition, the Holocene vegetation history becomes more diversified: periods of alder, pine, fir and mixed oak forests alternate and end in a period of cultivated landscape.     

On the holocene history of vegetation in SE Bulgaria (Lake Arkutino,Ropotamo region)

Palynological studies and investigations on macrofossil remains have been carried out on two profiles of the Holocene sediments of Lake Arkutino situated near to the Black Sea coast of SE Bulgaria. Lake Arkutino is a freshwater lake with shallow water. The lake is separated from the Black Sea by a dune barrier. Sedimentation started at about 6100 B.P. No marine or brackish influence could be traced in the sediments although the lake level is around sea level. The history of vegetation does not display major fluctuations except for the lake vegetation itself and for the swamp forests (Longos forests) surrounding the lake. Forests on normal mineral soils were mainly occupied by deciduous oaks throughout the last 6100 years. Deciduous oaks are represented in the pollen diagrams by the Quercus robur type and the Quercus cerris type. Until about 5800 B.P., one of the two pollen diagrams indicates that forests still contained more Pinus and Corylus than afterwards. After 5800 B.P., Fagus and a hundred years later together with Carpinus betulus became more important in addition with submediterranean elements as Carpinus orientalis, Fraxinus ornus and Phillyrea. After 5200 B.P., Carpinus betulus became somewhat less important. Indicators for human influence are rare. The archaeological record speaks for a small population in the area under study since the 12th century B.C. Swamp forests of the so-called Longos forests type started to develop at about 3000 B.P. The macrofossil record offers possibilities to trace hydrological changes by tracing the history of hydrophyte and reed plant comminties. From about 5100 to at least 4000 B.P., the record for Lemnetea and Potametea communities is poor and the processes of terrestrialization was interrupted. It can be assumed that the highest Black Sea transgression which is dated to 5700–4000 B.P. and which showed a sea level 3–4 m higher than today heavily influenced Lake Arkutino. That may have resulted in a higher lake level and in some water supply from the nearby river Ropotamo which would explain certain changes in the sediments and in the composition of hydrophyte communities.     

Past distribution and ecology of the cork oak (Quercus suber) in the Iberian Peninsula: a pollen-analytical approach

Abstract.  This study presents pollen-analytical data from continental and offshore Iberian Peninsula sites that include pollen curves of Quercus suber , to provide information on the past distribution and ecology of the cork oak ( Q. suber ). Results centre on a new pollen record of Navarrés (Valencia, eastern Spain), which shows that the cork oak survived regionally during the Upper Pleistocene and was important during a mid-Holocene replacement of a local pine forest by Quercus -dominated communities. This phenomenon appears linked to the recurrence of fire and reinforces the value of the cork oak for reforestation programmes in fire-prone areas. In addition to Navarrés, other Late Quaternary pollen sequences (Sobrestany, Casablanca-Almenara, Padul, SU 8103, SU8113, 8057B) suggest last glacial survival of the cork oak in southern and coastal areas of the Peninsula and North Africa. Important developments also occur from the Late Glacial to the middle Holocene, not only in the west but also in the eastern Peninsula. It is suggested that, in the absence of human influence, Q. suber would develop in non-monospecific forests, sharing the arboreal stratum both with other sclerophyllous and deciduous Quercus and Pinus species.     

Early Holocene environmental change in the Kreekrak area (Zeeland, SW-Netherlands): A multi-proxy analysis

Detailed botanical (microfossil and macroremain), zoological and geochemical analyses (major and trace elements including C, Al, S, Ca, Fe, P, As, Zn, U, Ba and Rare Earth Elements) of organic deposits provide new insights into Early Holocene environmental change in the Kreekrak area (southwestern Netherlands). The age assessment of the record is based on high resolution AMS ¹⁴C wiggle-match dating (WMD). For the first time an AMS ¹⁴C WMD based chronology covering the Late Glacial/Holocene transition and early Preboreal is introduced for a site in The Netherlands.The Kreekrak botanical record reflects the end of the Younger Dryas to early Boreal and can be well correlated with pollen records from other sites in The Netherlands and Belgium. The palaeo-topography showed that the Kreekrak deposits formed in an abandoned channel of the River Schelde. Around ca. 11,490 cal BP, at the end of the Late Glacial/Holocene transition, infilling of the lake started with predominantly organic deposits in slowly running water. As a result of the warmer climate the area became forested with birch and poplar during the Friesland Phase (ca. 11,490-11,365 cal BP). Biological productivity of the lake and its surroundings increased. Aquatic vegetation developed in the lake, while shrubs of willow, reed swamps and grasslands fringed the shores. Precipitation increased, which caused a rise in the lake water table and an increase in the supply of oxic surface (= river) water into the Kreekrak lake. During this period, the Kreekrak lake was fed by inflowing river water, run-off, precipitation and seepage of Fe-rich groundwater. Around ca. 11,435 cal BP the water became stagnant probably as result of a total cut-off of the river channel. Inflow of river water ceased, while the supply of reduced Fe-rich groundwater became dominant. During the Rammelbeek Phase (ca. 11,365-11,250 cal BP), the climate was more continental and the abundance of grasslands and open herbaceous vegetation increased. Biological productivity remained high. In the lake, the supply of Fe-rich groundwater continued, the water level slightly decreased but aquatic vegetation remained present. At the end of the Rammelbeek Phase a sudden reduction in the supply of Fe-rich reduced groundwater caused a lowering of the groundwater level in the area, resulting in the development of a hiatus. Due to this hiatus, the Late Preboreal (11,250-10,710 cal BP) is absent from the record. During the early Boreal (10,710-10,000 cal BP) the landscape became densely forested and accumulation of peat in the former lake resumed due to a slowly rising groundwater level. The Boreal was a relatively stable period with low sedimentation rates.The combination of palaeobotanical and geochemical analyses in the Kreekrak record shows a close interrelation between landscape development and geochemistry. It appears that the environmental development of this area during the Late Glacial/Holocene transition and Early Holocene was largely influenced (directly or indirectly) by major climatic changes that occurred during this period, which determined local phenomena such as the composition and density of the vegetation, occurrence of seepage and river activity. Further research of this type has the potential to develop the application of major- and trace element geochemistry in palaeoenvironmental reconstructions.     

High vegetation and environmental diversity during the Late Glacial and Early Holocene on the example of lowlands in the Czech Republic

The diversity of vegetation and the environment in the Late Glacial period in the Elbe region is illustrated by a comparison of three palynological localities. The localities differ in their history, profile lithology and position relative to the Elbe river. The Hrabanovská ?ernava profile holds a record of the development of a shallow lake, which was surrounded by a cold continental steppe in the Early Dryas. Evidence of a pine forest in the Late Glacial period is captured in the surroundings of the profile Chrást. The Mělnický úval — P?ívory locality is an interdune infill, where marl sediments redeposited in shallow water. The surrounding vegetation was diffuse and influenced by erosion. In the Early Holocene, the landscape was covered by an open birch-pine forest. Broad-leaved woody species appeared later. Localities in the Elbe region share a high proportion of Pinus throughout the Holocene as a result of the spread of drift and terrace sands. The human impact in the mid Holocene manifests as evidence of intensive charring of localities.     

New palynological and tephrostratigraphical investigations of two salt lagoons on the island of Mljet, south Dalmatia, Croatia

In the sediments of both of the investigated lakes, the tephra from the Mercato-Ottaviano eruption (Vesuvius, southern Italy) (ca. 7900 B.P.) could be identified. The palynological investigations show that from ca. 9000-7200 B.P. (8000-6000 cal B.C.) deciduous oak forests predominated, with only a few representatives of Mediterranean vegetation. At the transition to the central European Atlantic Period those forests changed to an open vegetation type, dominated byJuniperus andPhillyrea. At about 5500 B.P. (4400 cal B.C.), theJuniperus-Phillyrea vegetation was replaced byQuercus ilex woodland that still occurs on the island of Mljet today and is considered to be the natural vegetation of the Dalmatian coastland. The associated vegetation of theQ. ilex forests changed several times. At the beginning of theQ. ilex period,Juniperus values were still high, but soon they decreased andErica spread. In more recent times theQ. ilex forests were partially replaced by plantations ofPinus halcpensis. Indicators of human impact are sparse throughout the pollen record. Clear evidence for human influence exists only from ca. 3100 B.P. (1300 cal B.C.) whenJuglans andPinus halepensis were introduced to the area. Later,Olea andSecale cultivation can be suggested and further spreading ofJuniperus indicates use of the land as pasture.     

Postglacial vegetation history as recorded from the subalpine Lake Ribno (NW Rila Mts), Bulgaria

A pollen analysis conducted on a 600 cm core from Lake Ribno (2184 m) in the Northwestern Rila Mountains, supplemented by 13 radiocarbon dates, has revealed the basic stages in its postglacial vegetation dynamics. The lateglacial vegetation, composed of Artemisia, Chenopodiaceae and Poaceae, with stands of Pinus and Juniperus-Ephedra shrubland, dominated in the stadials and partly retreated during the B?lling/Aller?d interstadial (14700–12900 cal. yrs. BP). The afforestation in the early Holocene (11600–7800 cal. yrs. BP) started with pioneer Betula forests, with groups of Pinus and Juniperus at mid-high altitudes, and Quercus forests with Tilia, Ulmus, Fraxinus, Corylus below the birch zone. A coniferous belt composed of Pinus sylvestris, P. peuce and Abies was shaped under the conditions of a more humid climate (7800–5800 cal. yrs. BP). The last trees that invaded the study area were Fagus after 4300 cal. yrs. BP and Picea abies after 3400 cal. yrs. BP. Evidence for destructive changes in the vegetation and indications of agricultural and stock-breeding activities (pollen of Triticum, Secale, Plantago lanceolata, Rumex, Juglans) was continuously recorded since the Late Bronze Age (3400–3200 cal. yrs. BP). The postglacial vegetation history in the Northwestern Rila Mountains demonstrated close similarities with that of the Northern Pirin Mountains.     

Vegetation and fire history of coastal north-eastern Sardinia (Italy) under changing Holocene climates and land use

Little is known about the vegetation and fire history of Sardinia, and especially the long-term history of the thermo-Mediterranean belt that encompasses its entire coastal lowlands. A new sedimentary record from a coastal lake based on pollen, spores, macrofossils and microscopic charcoal analysis is used to reconstruct the vegetation and fire history in north-eastern Sardinia. During the mid-Holocene (c. 8,100–5,300 cal bp), the vegetation around Stagno di Sa Curcurica was characterised by dense Erica scoparia and E. arborea stands, which were favoured by high fire activity. Fire incidence declined and evergreen broadleaved forests of Quercus ilex expanded at the beginning of the late Holocene. We relate the observed vegetation and fire dynamics to climatic change, specifically moister and cooler summers and drier and milder winters after 5,300 cal bp. Agricultural activities occurred since the Neolithic and intensified after c. 7,000 cal bp. Around 2,750 cal bp, a further decline of fire incidence and Erica communities occurred, while Quercus ilex expanded and open-land communities became more abundant. This vegetation shift coincided with the historically documented beginning of Phoenician period, which was followed by Punic and Roman civilizations in Sardinia. The vegetational change at around 2,750 cal bp was possibly advantaged by a further shift to moister and cooler summers and drier and milder winters. Triggers for climate changes at 5,300 and 2,750 cal bp may have been gradual, orbitally-induced changes in summer and winter insolation, as well as centennial-scale atmospheric reorganizations. Open evergreen broadleaved forests persisted until the twentieth century, when they were partly substituted by widespread artificial pine plantations. Our results imply that highly flammable Erica vegetation, as reconstructed for the mid-Holocene, could re-emerge as a dominant vegetation type due to increasing drought and fire, as anticipated under global change conditions.