Paoay Lake,northern Luzon,the Philippines: a record of Holocene environmental change

The last 7000 years of environmental history for Paoay Lake and its surrounding landscape is examined through the analysis of pollen, diatoms, charcoal, mineral magnetics and AMS dating. Basal sediments contain shells of Cerithiidae and the saline‐tolerant diatom Diploneis indicating that this was an estuarine environment before becoming a freshwater lake after 6000 bp . Pollen analysis shows that submontane forests, characterized by Pinus pollen, underwent a major disturbance around 5000 years ago, recovering to previous levels by 1000 years ago. Charcoal as an indicator of fire is abundant throughout record, although the highest levels occur in the earlier part of the record, between 6500 and 5000 years ago. An aspect of the project was to examine whether there is evidence of land clearance and agricultural development in the region during the late Holocene. While a clear signal of human impact in the record remains equivocal, there appears to be a correspondence between submontane forest decline and mid‐Holocene ocean data that depict warmer and possibly drier conditions for the region. The study highlights the vulnerability of these montane forests to forecasts of a warmer and drier climate in the near future.     

A new Late-glacial and Holocene record of vegetation and fire history from Lago del Greppo, northern Apennines, Italy

Detailed Late-glacial and Holocene palaeoenvironmental records from the northern Apennines with a robust chronology are still rare, though the region has been regarded as a main area of potential refugia of important trees such as Picea abies and Abies alba. We present a new high-resolution pollen and stomata record from Lago del Greppo (1,442 m a.s.l., Pistoia, northern Apennines) that has been dated relying on 12 terrestrial plant macrofossils. Late-glacial woodlands became established before 13000 cal b.p. and were dominated by Pinus and Betula, although more thermophilous taxa such as Quercus, Tilia and Ulmus were already present in the Greppo area, probably at lower altitudes. Abies and Picea expanded locally at the onset of the Holocene at ca. 11500 cal b.p. Fagus sylvatica was the last important tree to expand at ca. 6500 cal b.p., following the decline of Abies. Human impact was generally low throughout the Holocene, and the local woods remained rather closed until the most recent time, ca. a.d. 1700–1800. The vegetational history of Lago del Greppo appears consistent with that of previous investigations in the study region. Late-glacial and Holocene vegetation dynamics in the northern Apennines are very similar to those in the Insubrian southern Alps bordering Switzerland and Italy, across the Po Plain. Similarities between the two areas include the Late-glacial presence of Abies alba, its strong dominance during the Holocene across different vegetation belts from the lowlands to high elevations, as well as its final fire and human-triggered reduction during the mid Holocene. Our new data suggest that isolated and minor Picea abies populations survived the Late-glacial in the foothills of the northern Apennines and that at the onset of the Holocene they moved upwards, reaching the site of Lago del Greppo. Today stands of Picea abies occur only in two small areas in the highest part of the northern Apennines, and they have become extinct elsewhere. Given the forecast global warming, these relict Picea abies stands of the northern Apennines, which have a history of at least 13,000 years, appear severely endangered.     

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.     

Postglacial vegetational and fire history: pollen, plant macrofossil and charcoal records from two Alaskan lakes

Pollen, plant macrofossil and charcoal analyses of sediments from two Alaskan lakes provide new data for inferring Lateglacial and Holocene environmental change. The records span the past 14,700 years at Lost Lake, 240 m a.s.l., central Alaska, north of the Alaska Range and 9600 years at Grizzly Lake, 720 m a.s.l., Copper River Plateau, south of the Alaska Range. Salix shrubs expanded in the herb tundra about 14,400 cal b.p., and Betula shrub tundra became established at ca. 13,200 cal b.p. Diminished Betula shrub cover in association with the increased abundance of herbaceous taxa occurred at 12,500–11,600 cal b.p., although the timing of these changes is not well constrained. Populus expanded at 11,200 cal b.p. and formed dense stands until 9600–9400 cal b.p. when Picea glauca forests or woodlands became established at both sites. The abundance of Alnus viridis increased markedly around 8500 cal b.p. at both sites, marking the development of alder shrub thickets around the lakes and on mountain slopes in these areas. Boreal forests dominated by Picea mariana became established around 7200 cal b.p. at Grizzly Lake and 5700 cal b.p. at Lost Lake. At Grizzly Lake, marked vegetational oscillations occurred within the past 8500 years; for example, A. viridis expanded at 2750 cal b.p. and 450 cal b.p. and declined at 150 cal b.p. Some of these oscillations coincide with large-scale climatic events, such as the Little Ice Age cooling (LIA), and they probably reflect vegetational sensitivity to climatic change at this high site. Microscopic charcoal at Lost Lake suggests that fire was important in the lateglacial birch tundra, probably because of severe moisture deficits of the regional climate and/or high abundance of fine fuels. On the basis of the Grizzly Lake microscopic charcoal record, regional fires were common between 8500 and 6800 cal b.p. and between 450 and 150 cal b.p. Around Grizzly Lake, the mean return intervals of local fires estimated from macroscopic charcoal were ∼386 years between 6800 and 5500 cal b.p. when Picea glauca dominated over P. mariana, ∼254 years between 5500 and 3900 cal b.p. when P. mariana was more abundant than P. glauca, and ∼200 years after 3900 cal b.p. in both P. glauca and P. mariana dominated forests. Correlation analysis of pollen and microscopic charcoal at Grizzly Lake reveals that increased fire activity led to the reductions of P. glauca, P. mariana, and tree Betula in association with the expansions of A. viridis, Epilobium, Lycopodium clavatum, and L. annotinum.     

The relationships between the concentrations of airborne pollen and allergic symptoms in Trieste (Northern Italy) in 1989

Summary Concentrations of airborne pollens recorded in Trieste in 1989 are evaluated in relation to allergic complaints in 113 patients with skin prick tests positive to one pollen species. Analysis of the result enable the two most important allergens to be confirmed as: Poaceae in 70.7% of patients and Parietaria in 18.6%. Few people had monosensitation to Compositae (Artemisia), Corylaceae and Fagaceae.Sympotoms are related to the flowering period when pollen levels climbed to daily averages of 15–20 grains/m³ but they started later than airborne peak concentrations and finished later than pollen decline. Pollen concentration recording can be a useful way to predict the clinical manifestation in sensitive patients but other factors are involved in determining symptoms like subjective mucosal reactions, polysensitization, patients living and working environment.     

Rhinacanthus spiciformis,a new species of Acanthaceae from northern Vietnam

Rhinacanthus spiciformis Y. F. Deng, Z. L. Lin & D. V. Hai, a new species from northern Vietnam previously misidentified as R. calcaratus is described and illustrated. This new species differs from all other Asian species of Rhinacanthus in the inflorescence being unbranched or comprised of trifurcate-branched spikes, and the lower lip of corolla with conspicuous purple stripes near throat and on lobes. The pollen morphology and chromosome number are presented. It is proposed to be accessed as Least Concern (LC) according to the IUCN categories and criteria.     

Holocene vegetation history of the Sahel: pollen, sedimentological and geochemical data from Jikariya Lake, north-eastern Nigeria

Aim This study aims to separate regional and local controls on Holocene vegetation development and examine how well pollen records reflect climate change in a semi‐arid region. The relative importance of climate and human activity as agents of vegetation change in the Sahel during the late Holocene is also considered. Location Jikariya Lake, an inter‐dune depression in the Manga Grasslands of north‐eastern Nigeria. Methods Pollen and charcoal were used to provide a record of Holocene vegetation history. Palaeoclimate and hydrological changes were reconstructed from sedimentary and geochemical data. Regional and local influences were separated by comparing the evidence obtained from Jikariya Lake with previously published data from the Manga Grasslands. Results The Manga Grasslands experienced a prolonged wet period during the early and mid‐Holocene, during which swamp forest vegetation with Guinean affinities (Alchornea, Syzygium, Uapaca) occupied the inter‐dune depressions. However, variation in the pollen records between sites suggests that their establishment was dependent on conditions being locally favourable, rather than being directly coupled to regional climate. The pollen records from the Manga Grasslands are more consistent in suggesting the colonization of the dunefields by trees associated with Sudanian savanna (Combretaceae, Detarium) c. 8700 cal. yr bp . The Jikariya Lake pollen data are in accordance with the sedimentological and geochemical data from the region in indicating that the onset of arid conditions occurred progressively during the late Holocene (from c. 4700 cal. yr bp ). Abrupt changes in pollen stratigraphy, recorded at other Manga Grasslands sites 3500 cal. yr bp , appear to be the product of the local passing of ecological thresholds. The dunefield vegetation (Sahelian savanna) appears to have been resilient to (or at least palynologically silent regarding) to the climatic variability of the late Holocene. Main conclusions While climate appears to have been the primary control on vegetation development in the Manga Grasslands during the Holocene, local conditions (particularly depression size and sand influx) had a strong influence on the timing of pollen stratigraphic changes. Anthropogenic influences are difficult to detect, even during the late Holocene.     

A new contribution to the Holocene vegetation history of the West African Sahel: pollen from Oursi,Burkina Faso and charcoal from three sites in northeast Nigeria

A pollen diagram from Oursi in Burkina Faso is compared with anthracological (charcoal analysis) results from three sites in northeast Nigeria (Konduga, Gajiganna, Lantewa). The present-day vegetation at all four sites is Sahelian or Sahelo-Sudanian and under heavy human impact. At Oursi, a closed grassland with only few trees and almost no Sudanian elements can be reconstructed for the middle Holocene. At the Nigerian sites, on the other hand, Sudanian woody plants were present during this period. We assume that the Sahel was not a uniform zone during the middle Holocene but rather a mosaic of different vegetation types according to local site conditions. In the light of these results, a simple model of latitudinally shifting vegetation zones is not applicable. Around 3000 B.P. the closed grassland at Oursi was opened by agro-pastoral activities, and at Gajiganna, plants characteristic of pasture lands can be directly related with the presence of cattle. Human impact seems to have been the dominant factor in the vegetation history of the Sahel from 3000 B.P. until today, masking possible effects of climatic change.     

Predicting the start of the birch pollen season at London, Derby and Cardiff, United Kingdom, using a multiple regression model, based on data from 1987 to 1997

Recent changes in weather in North-West Europehave been reflected in the start dates ofpollen seasons. It is therefore necessary toupdate previous models, such as the oneproduced by Jones (1995), so that the modelwill be weighted by current weather patterns. Birch pollen data, collected over a period ofeleven years (1987 to 1997 inclusive) fromthree pollen counting stations in the UK,London, Derby and Cardiff, were analysed todetermine the start dates using the Sum75method. The start dates of the birch pollenseasons of the eleven-year period were thentested for significance against ten-dayaggregated variables of temperature andrainfall for each site. The significantvariables were entered into multiple regressionmodels until the most valid equation for eachsite was found. The models were then tested onthree years not included in their data sets. The models showed mean differences betweenactual and predicted start dates, for theeleven years used, of 1.5, 3 and 5 days atDerby, Cardiff and London respectively. Forthe test years the mean difference was 1, 4.5and 7.5 days at Derby, Cardiff and Londonrespectively. The most powerful model was forDerby where the corresponding meteorologicalstation is at 0.5 km distance and the weakestwas for London where the correspondingmeteorological station is much further away at21 km distance. Weather variables from earlyFebruary to mid March were found to be the mostinfluential on the start dates of the birchpollen season at the three sites.     

Vertebrate-rich Plattenkalk of Pietraroia (Lower Cretaceous,Southern Apennines,Italy): a new model

The Lower Cretaceous Pietraroia Plattenkalk is a fossiliferous, fine-grained cherty limestone from the Matese Mountains – Southern Apennines, Italy. The deposits are well known for the exceptional state of vertebrate fossil preservation. First considered as shallow lagoonal deposits or as intra-platform basin-fill, the Pietraroia Plattenkalk sequences are here interpreted as abandon deposits of a submarine channel (Pietraroia Channel) documenting a major transgressive event. Transgression was associated with the development of suboxic to anoxic conditions at the seafloor which favoured the preservation of fossils, as well as the deposition of coprolith-rich and bituminous layers. A peculiar paleogeographic and paleotopographic setting, which was strongly controlled by local tectonic, experienced the contiguity of wide emerged areas with a relatively deep-water channelised area where fossiliferous Plattenkalk sequences were deposited.     

Sedimentary filling of a wedge-top basin and relationship with the foredeep (Middle Miocene Marnoso-arenacea Formation, northern Apennines)

The Middle Miocene Marnoso-arenacea Formation at Deruta in the northern Apennines of Italy rests unconformably on an orogenic wedge adjacent to the Adriatic foredeep. Based on a detailed facies analysis, the succession reveals two genetically related depositional systems: a distal delta-fed sand-rich system and a more proximal fan-delta slope system. Petrographic data confirm the genetic relationship between the two depositional systems, with the fan-delta slope feeding the basinward sand-rich system. The Deruta depositional setting shows a multi-step sedimentary evolution controlled by tectonically induced relative sea-level changes. The first stage, corresponding to a sea-level rise, promoted deposition in a wedge-top basin of pebbly sand and sand lobes (delta-fed). The second stage, characterized by intense tectonic activity (uplift) and sea-level fall, promoted accumulation of a prograding fan-delta slope replacing the sand-rich lobes. This phase was dominated by mass failures and methanogenic cold seepages. During these two stages, the wedge-top basin was isolated from the adjacent foredeep. Only during the third stage was a connection established, with the development of a deep-sea fan in the foredeep, fed by a deltaic depositional system.     

中国狭麦蛾属Stenolechia分类研究及三新种记述(鳞翅目:麦蛾科:特麦蛾族)

本研究对中国狭麦蛾属Stenolechia Meyrick,1894进行了分类研究,共记述7种,包括3新种:长瓣狭麦蛾Stenolechia longivalva sp.nov.,弯瓣狭麦蛾Stenolechia curvativalva sp.nov.和楔狭麦蛾Stenolechia cuneata sp.nov.,...     

Eemian and Early Weichselian vegetation and climate history in Central Europe: A case study from the Klinge section (Lusatia, eastern Germany)

The paper presents vegetation and climate reconstructions for Eemian and Early Weichselian in Central Europe based on detailed pollen data of the Klinge section. The sediments exposed in this profile were accumulated from the Saalian termination up to the Early Weichselian glaciation. A succession of forest communities, typical for the Eemian interglacial has been recorded. Pollen data indicate some oscillations during the very end of the Eemian (biozone E7). The climatic reconstructions show the heat supply rising gradually from the beginning of the interglacial to its middle part. A long-term cooling trend in January temperature was reconstructed for the second half of the interglacial. The difference between the optimum (zone E4b) and Pinus-Picea-Abies zone (E6) amounts to 4 °C, during the Pinus zone (E7) the temperature further decreased by 8 °C. The changes in July temperature were not so dramatic (about 3 °C).     

Holocene mangrove dynamics and sea-level changes in northern Brazil, inferences from the Taperebal core in northeastern Pará State

A 450 cm sediment core from Taperebal, in the mangrove region of northeastern Pará State in northern Brazil has been studied through pollen analysis in order to reconstruct mangrove development and dynamics and to infer relative sea-level (RSL) changes during the Holocene. Six AMS radiocarbon dates, which provide a somewhat limited age control with some uncertainties, suggest early and late Holocene deposits interrupted by a hiatus between them. A patchy vegetation of coastal Amazon rain forest, restinga, salt marsh and some mangrove, which was dominated by Avicennia, covered the study area during the early Holocene period. The occurrence of an early Avicennia dominated mangrove phase has not been reported so far from other sites in northern Brazil. During the mid Holocene mangroves mostly replaced the former coastal Amazon rain forest, restinga and some salt marsh vegetation, reflecting the rise in the RSL. Rhizophora trees expanded markedly and Avicennia became rare. In the sediment core there is apparently a gap between the depths of 115 and 85 cm (possibly starting between 5900 and 5750 b.p.). The deposits above 85 cm are of modern age and were probably deposited during the last decades. This gap can be explained by the lowering of the RSL as is shown for other northern Brazilian coastal sites. The deposition of sediments during the last decades suggests that the modern RSL is high compared to other periods in the Holocene. Pollen data from these deposits show that Rhizophora trees dominate the mangrove forests, also indicating a high RSL.     

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     

An example of Holocene vegetation stability from Camerons Lagoon,a near treeline site on the Central Plateau,Tasmania

Abstract A discontinuous record of vegetation over the past 7500 years was obtained through pollen analysis of pond sediments from an extensive treeless plain on the relatively dry Central Plateau of Tasmania. The results demonstrate continuity of treeless conditions, which probably persisted from the Pleistocene throughout the Holocene, up to the present day. Some changes to the structure of the grassland were observed, especially over the past 200 years. Analysis of carbonized particles showed that fires had been infrequent over the period examined. It seems that this area, close to the altitudinal tree limit, has remained a natural grassland, and the hypothesis of Jackson (1973), that unreliable summer conditions may be a major factor in maintaining open conditions, is supported. Parts of the Central Plateau may thus preserve plant communities with some of the floristic elements and structure of widespread Bassian grasslands of the Late Pleistocene.