A Mediterranean Holocene restricted coastal lagoon under arid climate: Case of the sedimentary record of Sabkha Boujmel (SE Tunisia)

The Holocene sedimentary record of Sabkha Boujmel (SE Tunisia) is expressed by a shallowing-upward carbonate lagoon-tidal flat cycle (2.3 m thick) unconformably overlying continental silt-sandy sediment, Late Würmian in age. The sedimentary package of this cycle starts with transgressive marginal shallow marine (intertidal to subtidal) bioclastic sands grading upwards to black mudstone, rich in organic matter (T.O.C. up to 1.3%) deposited within a lagoon protected from the sea by Upper Pleistocene lithified sand spits.The uppermost part of the cycle is represented by oobioclastic carbonate sands covered with dead biodegraded microbial mats and/or reddish sands of aeolian origin deposited in intertidal to supratidal environments. The facies arrangement, particularly the spatial distribution of the ancient and the more recent microbial mats, records the progressive infilling of the lagoon as well as the progradation of the shoreline during the last 2000 years. The organic-rich facies which provide an age varying between 4130 and 6800 yr B.P. were deposited when the Boujmel lagoon started to be progressively separated from the Mediterranean Sea.The main factors controlling the facies and the thickness variation are the local topographic sea-floor irregularities most likely controlled by the inheritance morphology resulting from an important fluviatile digging that occurred during the last glacial maximum, the relative sea-level fluctuations, the hydro-isostatic rebound and the climate.     

Holocene vegetation and climate evolution of Corpus Christi and Trinity bays: Implications on coastal Texas source-to-sink deposition

The Texas coastline stretches 595 km across almost 4° of latitude and is home to diverse coastal vegetation assemblages, yet only a handful of studies have documented the climate and vegetative change of this region through the Holocene. We provide a detailed palynological record of Holocene climate for coastal Texas, based upon three subaqueous sediment cores from Corpus Christi Bay and Trinity Bay. Cluster analysis and correspondence analysis were used to investigate changes in palynological assemblages through time within each core. Common to both bays are nonarboreal taxa including Asteraceae (mainly Ambrosia and Helianthus), Chenopodium, Poaceae, and arboreal taxa such as Carya, Pinus, and Quercus. Our record shows that the coastal environments of central Texas began a transition from herbaceous (nonarboreal) dominated vegetation to arboreal vegetation as early as 8.4 ka within Corpus Christi Bay, and 3.8 ka within Trinity Bay. We note flooding events at 8.2, 5.4, and 3.6 ka in Corpus Christi Bay, and at 1.7, 1.2, and 0.8 ka in Trinity Bay. These events were caused by storms, sea level changes including flooding of relict river terraces, and changes in sediment delivery to the bays. The pollen record also shows evidence for changes in fluvial discharge to Corpus Christi Bay at 4.1 and 2.2 ka, and at 1.8 ka in Trinity Bay. We also see Zea mays in Trinity Bay, indicating local Native American agriculture. We observe no significant changes during the middle Holocene Climatic Optimum, and subtle but not statistically significant evidence of more variable climate oscillations than other records from more interior sites in Texas available for the late Holocene. This indicates that coastal Texas’ climate has operated semi-independently from central Texas regions, and was primarily driven by a coast-wise gradient of precipitation and evapotranspiration.     

Marine saline ponds as sedimentary archives of late Holocene climate and sea-level variation along a carbonate platform margin: Lee Stocking Island, Bahamas

A 1500-year, late Holocene history of coastal and lacustrine carbonate sedimentation is preserved in shallow ponds on Lee Stocking Island, Exuma Cays, Bahamas. Details of environmental change have been extracted by integrating lithostratigraphy, biostratigraphy (macrobiota, foraminifers, ostracodes), and chemical stratigraphy (C, O isotopes of foraminiferal and molluscan skeletal carbonate; MgO wt% of ostracode calcite) with a well defined ¹⁴C AMS radiocarbon chronology. Carbonate deposition began within physically restricted, euryhaline coastal embayments, with several pronounced changes in salinity defined by biotic and calculated salinity variation (from MgO wt% in shells of Cyprideis americana). By about 700–740 yr B.P., embayment closure occurred possibly related to changed longshore deposition associated with sea level rise and/or regional change in climate (previously documented). With closure, the initial euryhaline foraminifer assemblage was replaced by a predominant hypersaline biofacies (e.g., Triloculina sp.); with progressive basin fill, ostracode assemblages, calculated salinities, and variation in abundance of the gastropod Cerithidea sp. may resolve higher-order (and some extreme) salinity fluctuations throughout the remaining history of saline pond development. Foraminiferal isotope stratigraphy is compatible with that expected for hydrologically closed lake basins. Carbonate accumulation was effectively shut-down <200 years ago, replaced by stromatolitic growth. Present-day salinities vary according to water balance governed by rainfall and evaporation. A centuries-scale (300–400 year) flux of abraded (reworked), marine-derived bioclasts, admixed with skeletal remains of indigenous biota, is also preserved in these ponds. Allochthonous sediment was transported by hurricane storm surges or related to abrupt transgressive events superimposed on an overall gradual rise in global sea level. We discuss evidence for both as controls on sedimentation. Our study illustrates that saline ponds on Bahamian islands are excellent sedimentary archives of local, regional, and possibly global paleoclimatic events of late Holocene age.     

Trace element levels in mollusks from clean and polluted coastal marine sites in the Mediterranean, Red and North Seas

The trace element contamination levels in mollusks were evaluated for different marine coastal sites in the Mediterranean (Israeli coast), Red (Israeli coast) and North (German coast) Seas. Three bivalve species (Mactra corallina, Donax sp, and Mytilus edulis) and two gastropod species (Patella sp.and Cellana rota) were sampled at polluted and relatively clean sites, and their soft tissue analyzed for Hg, Cd, Zn, Cu, Mn and Fe concentrations. Representative samples were screened for organic contaminants [(DDE), polychlorinated biphenyls PCBs and polycyclic aromatic hydrocarbons (PAHs)] which exhibited very low concentrations at all sites. In the Red Sea, the gastropod C. rota showed low levels of Hg (below detection limit) and similar Cd concentrations at all the examined sites, while other trace elements (Cu, Zn, Mn, Fe) were slightly enriched at the northern beach stations. Along the Mediterranean coast of Israel, Hg and Zn were enriched in two bivalves (M. corallina and Donax sp.) from Haifa Bay, both species undergoing a long-term decrease in Hg based on previous studies. Significant Cd and Zn enrichment was detected in Patella sp. from the Kishon River estuary at the southern part of Haifa Bay. In general, Patella sp. and Donax sp. specimens from Haifa Bay exhibited higher levels of Cd compared to other sites along the Israeli Mediterranean coast, attributed to the enrichment of Cd in suspended particulate matter. Along the German coast (North Sea) M. edulis exhibited higher concentrations of Hg and Cd at the Elbe and Eider estuaries, but with levels below those found in polluted sites elsewhere. Received: 25 February 1999 / Received in revised form: 22 April 1999 / Accepted: 30 April 1999     

Profiles of trace elements and stable isotopes derived from giant long-lived Tridacna gigas bivalves: Potential applications in paleoclimate studies

This study investigates the environmental and biological controls on trace element partitioning and stable isotope composition of modern giant long-lived bivalves (Tridacna gigas) with the aim to use these archives for paleoclimatic reconstructions. Firstly, the intra-shell variability is studied by measuring time equivalent profiles in the different shell layers characterised by different growth rates. Secondly, the inter-site variability is studied by comparing profiles derived from three modern specimens collected in sites across the Indo-Pacific region characterised by different ranges of temperature and productivity.These results show that δ¹⁸O profiles are highly reproducible across the shell regardless of significantly different growth rates. Shell δ¹⁸O is primarily controlled by water δ¹⁸O and temperature. Comparison of intra shell Mg/Ca profiles shows a clear and systematic partitioning where inner layer Mg/Ca values are a least 2–3 times higher than outer layer and hinge areas. Inner layer Mg/Ca shows seasonal oscillations but superimposed on an ontogenetic trend with increasing values and increasing amplitude Mg/Ca oscillations with age. The Sr/Ca profiles do not show clear reproducible seasonal trends in the different shell zones. It is concluded that Mg/Ca and Sr/Ca profiles appear to reflect a combination of biological and environmental controls that will need to be disentangled before using these proxies in paleoclimatic studies.Finally, intra shell Ba/Ca profiles are reproducible in great detail for all modern specimens studied. Inter-site comparison shows that the amplitude and the timing of the Ba/Ca peaks appear to reflect the timing and the amplitude of the chlorophyll peaks associated with phytoplankton blooms at each locality making this tracer a potential paleoproductivity indicator.     

The effects of glacio-eustatic sea-level change on Pleistocene cold-water ostracod assemblages from the Japan Sea

The Pleistocene palaeo-habitats and the extinction history of cold-water ostracods in the Japan Sea are recorded in its coastal strata. The presence of now-extinct species in the Omma Formation of central Japan (1.5 Ma) indicates that such species predominated in a shallow, open sea environment. The tolerance ranges of these species as to water temperature and salinity are inferred to have been narrower than those of most extant cold-water species in the same families that live in shallow open water, as well as in brackish inner bays. The horizons in the Omma Formation with peak relative abundances of now-extinct species differ from the horizons with peak abundances of living Japan Sea species. We therefore suggest that the now-extinct species were adapted to optimum temperature and salinity conditions that differ from those in the modern Japan Sea. The observation that few now-extinct species survived after 0.4 Ma may be explained by the hypothesis that physicochemical properties of the water masses changed. We argue that, during the glacial periods with increased amplitude (0.9–0.4 Ma), the salinity decreased as the result of glacio-eustatic changes and the closure of shallow straits owing to low sea levels, causing the extinctions.     

Comparison of trace element and stable isotope approaches to the study of migratory connectivity: an example using two hirundine species breeding in Europe and wintering in Africa

Analyses of stable isotopes and trace elements in feathers may provide important information about location and habitat use during molt, thereby enabling the investigation of migratory connectivity and its ecological consequences in bird species that breed and winter in different areas. We have compared the conclusions arrived at based on the use of these two methods on the same samples of feathers from two migratory birds, the Sand Martin Riparia riparia and the Barn Swallow Hirundo rustica. We investigated the effects of location, age and sex on stable isotope (δ¹³C, δ¹⁵N, δD) and trace element profiles (As, Cd, Mg, Mn, Mo, Se, Sr, Co, Fe, Zn, Li, P, Ti, V, Ag, Cr, Ba, Hg, Pb, S, Ni and Cu). The feathers of adults at the breeding grounds were removed, forcing in birds to grow new feathers at the breeding grounds; this enabled a comparison of composition of feathers grown in Europe and Africa by the same individual. Stable isotope and trace element profiles varied geographically, even at micro-geographic scales, and also among age classes. The results of both methods suggest that food composition and/or source differs between adults and nestlings in the breeding area and that food and/or molting location changes with the age of individuals in Africa. In an attempt to determine the usefulness of data obtained from composition of feathers, we performed discriminant function analyses on information obtained on stable isotopes and trace elements in order to assess the correctness of the classification of group membership. When feathers molted in Africa were compared to those molted in Europe, trace element profiles of the 22 elements generally had a much greater resolution than the stable isotope profiles based on three stable isotopes. The proportion of correctly classified samples was also greater for analyses based on trace elements than for those based on stable isotopes.     

Stable isotope analyses of mammal skeletal remains of Holocene age from European Russia: A way to trace dietary and environmental changes

Fifty-five samples of human and animal fossil skeletal remains (sheep, cattle, horse and deer) collected at six different sites in European Russia were measured for the oxygen isotopic composition of bone phosphate (δ¹⁸Op) and for the carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic composition of bone collagen. The age of these samples ranges from 10 500 to 200 BP covering a time period of about 10 000 years. The samples come from the steppe area of southern European Russia, from the northern Black Sea coast and from an area near Moscow. From the results obtained it can be suggested that the steppe tribes were nomads, at least after 4000 BP, and that they probably moved from east to west and vice-versa (i.e. from the Volga area to the Black Sea coast). C₄ plants were present in the steppe area since 5000 BP. On the contrary, in the area near Moscow and on the Black Sea coast no C₄ species are documented at least until 5000 and 6000 BP respectively. Arid environmental conditions dominate the steppe area even though the N isotope values suggest a climatic improvement-taking place from 5000 BP towards present in terms of more humid conditions. As regards diet, it seems that the subsistence of the steppe populations was based mainly on terrestrial food and in particular on sheep with a minor contribution of fish. The populations from the Moscow area probably had a permanent economy mainly based on fishing.     

The Massaciuccoli Holocene pollen sequence and the vegetation history of the coastal plains by the Mar Ligure (Tuscany and Liguria,Italy)

A 90 m deep core from the Massaciuccoli lake basin (Tuscany, Italy) offers new material for improving the knowledge of the Holocene vegetation history in the coastal plains in Tuscany and Liguria bordering the Mar Ligure (Ligurian sea). In this paper, an assessment of the upper part of the core is presented. During the Holocene, the area was covered by woodlands whose composition changed in time. Numerous oscillations of the tree taxa were recorded which can probably be connected to sea level variations that had a strong influence on the depth of the water table. Human impact is evident particularly at ca. 4200–2500 b.p. when traces of opening of the woodland accompanied by noticeable pollen percentages of Vitis could suggest an early agricultural practice favouring this native plant. The new data have been integrated with previous palaeobotanical and archaeobotanical research. The occurrence of coastal wetlands has been shown. Throughout the Holocene, Mediterranean evergreen vegetation is generally poorly represented; it becomes widespread only in the late Holocene, suggesting that its establishment was probably favoured by the management practices in the coastal plains, particularly land reclamations, starting from the Roman period.     

Reconstruction of climate change during the Holocene in western and central Europe based on pollen records of indicator species

On the basis of distribution maps showing the first pollen occurrences in the Holocene of the well-known climate indicators Hedera, Ilex and Viscum as well as data for Corylus, a series of maps have been prepared that show summer and winter isotherms at various time intervals during the Holocene. From these maps climate curves for Amsterdam, the Netherlands have been set out. These were compared with curves for the Eemian at the same site. In both of these warm periods there is evidence for increased seasonality in the early phases which were relatively continental. Changes in insolation could account for such differences. Summer optima occurred earlier than winter optima. Changes in land-sea distribution are important, especially with regard to the patterns in winter climate. During the latter half of the Eemian, the climate was distinctly more oceanic than in the Holocene. Early in the Holocene, an influx of warm ocean water resulted in higher winter temperatures in the Gulf of Biscay, the Irish Sea, and areas east of Skagerrak-Kattegat. Temperature decline after the climatic optimum was greatest in the north, i.e. at 60°N, where a depression in the order of 2°C in summer and 2–3°C in winter occurred. Temperature decline was less farther south, i.e. at ca. 50°N, where a distinct west-east gradient in temperature change can be observed.     

6000 years of environmental changes recorded in Blue Lake, South Australia, based on ostracod ecology and valve chemistry

A 4 m long core taken from the freshwater Blue Lake crater near the township of Mount Gambier in southeastern South Australia provided a high-resolution palaeoclimatic record for the last six millennia. Accelerator Mass Spectrometry (AMS) radiocarbon (¹⁴C) dates were obtained from organic plant fibres and biogenic carbonates from the laminated sequence of the core and from a modern water sample. Large discrepancies between the radiocarbon ages determined from plant fibres and biogenic carbonates indicate the presence of a time-variable lacustrine reservoir, which is consistent with what is known of the lake's hydrology.Ostracod assemblages, associated with stable isotope (δ¹³C, δ¹⁸O) analyses and, in combination with Mg/Ca, Sr/Ca and Na/Ca analyses done on ostracod valves, infer salinity, temperature and water level changes in Blue Lake over the last 6 millenia. The influence of local aquifers through time has also been determined from the Na/Ca of ostracod valves. Approximately 900 year cycles are evident in the δ¹³C record from 5.4 ka to 1.8 ka.The history of Blue Lake records an initial period of high hydrological variability around 6 ka, becoming increasingly deeper as groundwater flowed into the basin. By 4 ka, the lake had reached steady state with the lake level fluctuating by as much as 9 m, although significant geochemical variations represent temperature fluctuations until European settlement near the lake in 1839.     

Impacts of permethrin contamination on nematode density and diversity: A microcosm study on benthic meiofauna from a Mediterranean coastal lagoon

A microcosm experiment was used to examine the response of nematode in terms of density and diversity at different levels of permethrin contamination. The sediments were contaminated with three permethrin concentrations [P1: low (5 mg kg⁻¹), P2: medium (25 mg kg⁻¹) and P3: high (250 mg kg⁻¹)] and the effects were evaluated after 30 days. The results from univariate and multivariate analyses showed significant differences between nematode assemblages from uncontaminated control and those from permethrin treatments. All univariate indices changed significantly at all the levels of permethrin contamination. In fact, the total nematode abundance (I), Shannon-Weaner index (H′), species richness (d), evenness (J′) and number of species (S) decreased significantly in all the contaminated microcosms. In addition, the results from multivariate analyses of the species abundance data demonstrated that permethrin affects the responses of nematode species. These significant modifications in nematode community structures with response to permethrin contamination were the consequences of a different specific tolerance to this pesticide. Thus, Araeolaimus bioculatus, Calomicrolaimus honestus, Oncholaimus campylocercoides and Theristus pertenuis characterized by increased abundances in all treated replicates, appeared to be “permethrin-resistant” species. Daptonema trabeculosum was eliminated in all the doses tested and seemed to be a very sensitive species to permethrin contamination.     

Lateglacial and Holocene vegetation change on the Isle of Skye: new data from three coastal locations

Detailed lithostratigraphical and biostratigraphical studies from three contrasting coastal sites on the Isle of Skye were undertaken to investigate spatial variations in vegetation development on the island since the Lateglacial. The pollen profiles were then compared with the published pollen data for Skye. The new data reveal broadly similar trends for the sites studied and show that these correspond well to the previously established chronology. A date of ca. 10110 radiocarbon years B.P. has been obtained for the rational rise in Corylus, a date of ca. 8850 uncal B.P. for the appearance of Ulmus and a date of ca. 6600 uncal B.P. for the rise in Alnus. However, significant variations were evident and these were due to (a) coastal proximity, which directly affects vegetation composition through the low but persistent presence of Armeria and Chenopodiaceae, (b) altitude, which determines the effect of rising groundwater that may be related to relative sea level rise, and (c) aspect and position in relation to central Cuillin mountain range, through exposure to SW winds that restrict the development of thermophilous woodland and encourage the acidification of heathlands and development of herb-rich grasslands from ca. 4000 B.P.. This study reveals that the range of variation caused by these local factors is as great as the variation found throughout the island. This has negative implications for the reconstruction of regional patterns of vegetation change but highlights the range of local habitats and wild resources available to early inhabitants of the island.     

The influence of productivity and width of littoral zone on the trophic position of a large-bodied omnivore

Omnivory is common in many food webs. Omnivores in different habitats can potentially change their feeding behaviour and alter their trophic position and role according to habitat conditions. Here we examine the trophic level and diet of the omnivorous signal crayfish (Pacifastacus leniusculus) in gradients of trophic status and lake size, both of which have been previously suggested to affect trophic position of predators separately or combined as productive space. We found the trophic position of omnivorous crayfish to be positively correlated with lake trophic status, but found no evidence for any influence of lake size or productive space on crayfish trophic position. The higher trophic position of crayfish in eutrophic lakes was largely caused by a shift in crayfish diet and not by an increase in trophic links in basal parts of the food web. Hence, our results support the “productivity hypothesis,” suggesting that food chains can be longer in more productive systems. Furthermore, stable isotope data indicated that larger crayfish are more predatory than smaller crayfish in lakes with wider littoral zones. Wider littoral zones promoted the development of intrapopulation differences in trophic position whereas narrow littoral zones did not. Hence, differences in habitat quality between and within lakes seem to influence the trophic positions of omnivorous crayfish. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Studies on the zooplankton community of a shallow lagoon of the Southern Baltic Sea: long-term trends,seasonal changes,and relations with physical and chemical parameters

The Darß-Zingst Lagoon, a coastal inlet of the southern Baltic Sea, was subject to extended monitoring. The biomass data of zooplankton from 1969 to 2001 were used to analyze long-term trends and to correlate zooplankton biomass with abiotic factors. The dominant species in the lagoon were the calanoid copepods Eurytemora affinis and Acartia tonsa, and the rotifer Keratella cochlearis f. tecta. In the long-term trend, two pronounced changes in zooplankton biomass and species composition were observed. They are discussed in connection with a shift in dominance from macrophytes to phytoplankton and the invasion of a polychaet species into the lagoon. Significant relations between zooplankton data and abiotic parameters were found. While temperature, precipitation and NAO winter index correlated positively with copepods and negatively with rotifers, the relationships were inversely for pH-value and duration of ice cover.     

The Middle Miocene climatic transition in the Southern Ocean: Evidence of paleoclimatic and hydrographic changes at Kerguelen plateau from planktonic foraminifers and stable isotopes

Middle Miocene (14.8–11.9 Ma) deep-sea sediments from ODP Hole 747A (Kerguelen Plateau, southern Indian Ocean) contain abundant, well-preserved and diverse planktonic foraminiferal assemblages. A detailed study of the climatic and hydrographic changes that occurred in this region during the Middle Miocene Climatic Transition led to the identification of an intense cooling phase (the Middle Miocene Shift). Abundance fluctuations of planktonic foraminiferal species with different paleoclimatic affinities, and oxygen and carbon stable isotopes have been integrated in a multi-proxy approach. Reconstruction of changes in foraminiferal faunal composition and diversity through time were the basis for identification of three foraminiferal biofacies. The most prominent faunal change took place at 13.8 Ma, when a fauna with warm-water affinity (marked by high abundance of Globorotalia miozea group and Globoturborotalita woodi plexus) was replaced by an oligotypic, opportunistic fauna with typical polar characters and dominated by neogloboquadrinids. This faunal change is interpreted as the result of foraminiferal migration from adjacent bioprovinces, caused by modifications in climate and hydrography. A positive 2.0‰ shift in δ¹⁸O (interpreted as the Mi3 event) and a related positive 1.0‰ shift in δ¹³C (corresponding to the CM6 event) accompanied this faunal turnover. These are interpreted to reflect substantial reorganization of Southern Ocean waters, the northward migration of the Polar Front and a strong increase in primary productivity. The second faunal change took place at 12.9 Ma and was characterized by the gradual decrease in abundance of the neogloboquadrinids and the recovery of Globorotalia praescitula/scitula group and Globigerinita glutinata. A positive 1.5‰ shift in δ¹⁸O (interpreted as the Mi4 event) and a concurrent gradual negative shift in δ¹³C accompanied this faunal change, witnessing further modifications of the climate/ocean system. Variations in sea surface temperature, considered as the main factor causing changes of surface hydrography at the Kerguelen Plateau, seem to have been driven by obliquity and long-term eccentricity, thus suggesting a key role played by the astronomical forcing on the evolution of Southern Ocean dynamics during the Middle Miocene. Also an evident 1.2 Myr modulation of the δ¹³C record suggests a main control of the long-term obliquity cycles on the carbon cycle dynamics. Particularly, the Mi3/CM6 events exactly fit with a node of the 1.2 Myr modulation cycles. This confirms the key role played by orbital parameters on high-latitude temperatures and Antarctic ice volume, and indirectly on global carbon burial and/or productivity. This climatic transition was marked also by changes in surface hydrography. From 14.8 to 13.8 Ma an intermediate-strength thermocline controlled by seasonality developed just below the photic zone. Weaker seasonality characterized the interval from 13.8 to 12.9 Ma, when the thermocline became shallower and sharper and favored intermediate-water foraminifers. From 12.9 Ma, seasonality increased again and an intermediate-strength thermocline re-developed.     

Late-glacial and Holocene climate dynamics at the steppe/forest ecotone in southernmost Patagonia, Argentina: the pollen record from a fen near Brazo Sur, Lago Argentino

We present a pollen record from a fen at the eastern shore of Brazo Sur south of Lago Argentino, Argentina (core BRS 1/06, 50°34′54″S, 72°54′52″W, 198 m a.s.l.). The coring site is located in the transition zone from humid grass steppe to Andean Nothofagus forest. With the exception of a mid-Holocene sand layer, the record covers the interval between 13,350 and 1,700 cal b.p., indicating that there could have been no recurrence of Late-glacial conditions in Brazo Sur, as has been suggested in the literature as having been contemporary with the Younger Dryas interval in the northern hemisphere. The Late-glacial and early Holocene periods at Brazo Sur are characterized by fluctuations between humid grass-dominated steppe associations and drier ones dominated by Asteraceae and Ericaceae. At the start of the Holocene, the pollen influx increased. Nothofagus dominance began by 7,700 cal b.p. probably due to increasing moisture. Present-day closed Nothofagus forest developed around 2,500 cal b.p., related to a further increase in moisture.     

Charcoal analysis, a method to study vegetation and climate of the Holocene: The case of Lago di Pergusa (Sicily, Italy)

The direct comparison between microcharcoal and pollen data from the Holocene sediment core of Lago di Pergusa (central Sicily, Italy) led us to investigate the linkages between fire, vegetation, and climate in the Mediterranean Basin. The role of human populations in shaping the environment of the last millennia was closely examined as well. Pollen and charcoal were extracted using a standard pollen methodology and both identified from the same pollen slides. At Lago di Pergusa the importance of fire in maintaining and favouring a Mediterranean vegetation, a basic concept in ecology, seems to be inconsistent, as important fires took place in the open environments with xeric vegetation at the beginning of the Holocene well before the expansion of evergreen vegetation. On the contrary some big fires seem to have happened in the period (around 8000 years BP) in which the greatest wetness, the thickest forest canopy, and the most important expansion of submontane vegetation of the record are found. A probable explanation of this phenomenon can be found in the precipitation regime, in the increased available biomass and in the resulting increase in combustible material, indicating also that the highest humidity achieved in central Sicily during the Holocene was not strong enough to prevent fires. During this period drops in arboreal pollen concentration match in minima in the charcoal curves. Fires were practically absent during the Neolithic and Eneolithic periods and not responsible for the general trend towards aridification identified in the pollen record, at times in which prehistoric populations are generally believed to have caused forest clearance by burning. Important and frequent burnings are documented for the Bronze and Iron Ages and probably not all of them were fires of living trees, but burning of wood for producing metals, cooking or heating. The occurrence of a fire around 3700 years BP temporarily caused a minor decrease of arboreal pollen concentration. In the open landscapes of the two last millennia an almost continuous sign of regional burnings is recognized, confirming the historical evidence of an intense land use in central Sicily at least since Roman times.     

Pollen and macrofossil analyses of a unique peat remnant of the former extensive peat bogs in West Friesland,The Netherlands: a detailed record of coastal raised bog formation

Of the former extensive peat bog in West Friesland, only small, buried and often cutover remains are left, scattered over a wide region. The results of pollen and macrofossil analyses of the most complete peat profile found to date in this district is presented in this paper. The vegetation development during the final stage of marine sedimentation in the vicinity of the analysed profile is reconstructed in some detail, as well as the subsequent formation of the lower layers of the mire, including the ombrotrophic peat. Apart from these aspects, the study also contributes to our knowledge of the Holocene palaeogeography of the coastal region of the Netherlands.     

Autogenic succession, land-use change, and climatic influences on the Holocene development of a kettle-hole mire in Northern Poland

We reconstructed the Holocene developmental history of a kettle-hole peatland in the Tuchola Forest of Northern Poland, using pollen, testat amoebae and plant macrofossil indicators. Our aims were to determine the timing and pattern of autogenic succession and natural and anthropogenic influences on the peatland. Northern Poland is under mixed oceanic and continental climatic influences but has so far been less studied in a palaeoecological context than more oceanic regions of Europe. In the first terrestrial developmental phase of the mire, the testate amoebae-inferred depth to water table revealed two major dry shifts at ca. 9400 (end of lake phase) and ca. 7100 cal BP (a period of global cooling and dry shift in Western Europe). Conditions became wetter again in two steps at ca. 6700 and ca. 5800 BP after a dry event at ca. 6100 BP. The timing of the wet shift at 5800 BP corresponds to wet periods in Western Europe. Peat accumulation rates were low (0.1 mm yr^− 1) between ca. 5600 and ca. 3000 BP when sedges dominated the peatland. In the last 2500 yrs surface moisture fluctuated with wet events at ca. 2750–2400, and 2000 BP, and dry events at ca. 2250–2100 and 1450 BP. After 1450 BP a trend towards wetter conditions culminated at ca. 500 cal BP, possibly caused by local deforestation. Over the mire history, pH (inferred from testate amoebae) was mostly low (around 5) with two short-lived shifts to alkaline conditions (7.5) at ca. 6100 and 1450 BP indicating a minerotrophic influence from surface run-off into the mire. Up to about 1000 BP the ecological shifts inferred from the three proxies agree with palaeoclimatic records from Poland and Western Europe. After this date, however correlation is less clear suggesting an increasing local anthropogenic impact on the mire. This study confirms that kettle-hole peatlands can yield useful palaeoenvironmental data as well as recording land-use change and calls for more comparable studies in regions are the interface between major climate influences.