Holocene vegetation and fire dynamics in the supra-Mediterranean belt of the Gredos Range (central Iberian Peninsula)

Abstract

High-resolution pollen, macrofossil and charcoal data, combined with multivariate analysis, were used to reconstruct Holocene vegetation and fire dynamics at Manaderos. The studied mire is located in a highly valued location in the supra-Mediterranean belt of the Gredos Range (central Iberian Peninsula). The record started at 1260?calendar years (cal yrs) BP, according to eight radiocarbon dates, with the occurrence of an open Quercus pyrenaica forest and Pinus nigra stands. The palynological data show a dramatic change ～380?cal yrs BP, when the oak forest was progressively replaced by a maritime pine one. The interpretation of this record is related to an increase in agricultural and livestock activities and changes in the role of fire, thus Pyrenean oak canopy was consumed by fires providing openings for Pinus pinaster, better adapted to fire. The results are compared with other sequences from the Spanish Central System in order to better understand the past dynamics of the main forest constituents and to provide a critical view of the role of fire, anthropic dynamics and climatic events.     

Palynology of late Pleistocene hyrax middens,southwestern Cape Province,South Africa: A preliminary report

Botanical remains, especially pollen, preserved in dung middens of rock‐dwelling hyraxes (herbivorous mammals belonging to the genus Procavia) have been studied in the Southern African winter‐rainfall area. Seven middens from a single rock shelter on the north‐eastern side of the Cederberg mountain range, Cape Province, are dated by 15 radiocarbon age determinations to between about 19,700 and 1370 yr BP. Plant remains in the middens are mainly fine, partly digested fragments. Identifiable macro‐botanical rests like seeds are scarce, therefore this preliminary investigation is focused on analysis of abundant pollen grains. The results show changes in a Southern Hemisphere equivalent of the Mediterranean macchia vegetation, viz. “fynbos”;. Although “fynbos”; prevailed at the site throughout the studied period, an altitudinal lowering of vegetation belts is indicated during the Last Glacial Maximum, while an increase in arboreal pollen types, especially Dodonea is shown during terminal Pleistocene and Holocene times.     

Pollen analytical evidence of ‘landnam’ from two Scottish sites

Summary

Stratigraphic, relative pollen analytical data and pollen concentration data are presented from two cores collected from a lowland infilled lake basin in the eastern Scottish Borderlands. The stratigraphic sequence between 1·30 m and 2·16 m shows an oscillation of open water and deep water sediments indicating lake-level changes. This is supported by the pollen analytical data which show a markedly changing pollen sedimentation rate and a hiatus in Flandrian II due to changing lake-levels and an overall reduction in water-level. Supporting evidence is also drawn from Din Moss, a nearby radiocarbon dated profile.     

A 12 000-year record of environmental change in the Lomond Hills, Fife, Scotland: Vegetational and climatic variability

The Lomond Hills of Fife, an isolated upland area rising to over 500 m, provide an opportunity to investigate the effect of altitude on vegetation and climate in an area otherwise dominated by lower-lying land. The West Lomond site contains sediments of the Devensian Late-glacial period; they reveal a well-defined sequence of Bolling-Older Dryas-Allerod-Younger Dryas events, commencing ca. 12 190 radiocarbon years B.P. and a probable Amphi-Atlantic Oscillation between ca. 11 040 and 10 800 B.P. The Holocene record is constrained by low sediment input but does reveal a woodland presence at this altitude, dominated byBetula andCorylus. Size statistics forBetula pollen are presented and the implications of the vegetational and climatic record are discussed. The traditional view of a smooth progress towards more temperate conditions following the Younger Dryas is not supported; between 10 180 and 9120 B.P., three cooler periods are inferred, the earliest of which may belong to a terminal phase of the Younger Dryas. Comparative pollen ‘influx’ data strongly suggest thatQuercus,Ulmus andAlnus were not present locally. As a working hypothesis, it is suggested that the demise of woodland, from ca. 5950 B.P., was a result of exposure. Pollen indicative of human impact was probably derived from areas of lowland agricultural activity from ca. 5330 B.P. onwards.     

Extinction pattern of Alpine cave bears - new data and climatological interpretation

ABSTRACT

Cave bears have disappeared from the Alps from different altitudes at different times. The temporal progression of the HDEL (Height Dependent Extinction Line) – a compilation of the geologically most recent radiocarbon dates per altitude level – is not consistent with the general cooling of the temperatures from about 45 ka BP. The cave bear sites of the Northern Alps with the most recent radiocarbon ages are not situated in the lowlands but in caves in altitudes of 1,500 m to 1,700 m above sea level (a.s.l.).

Cave bears fed almost exclusively on herbs and leaves. It was assumed that with the general cooling in the OIS 3 since about 45 ka BP also the migration of the alpine elements into the lowlands took place. It could be recognized that the populations in the lower situated cave bear site became earlier extinct than the cave bear population in the higher altitudes.

With new radiocarbon dates, done at the Curt-Engelhorn-Center Archaeometry at the Reiss-Engelhorn-Museen in Mannheim (Germany), the HDEL can be determined much more precisely and the causes of gradual extinction are also better understood.     

Climatic and human effects on the post-glacial dynamics of <Emphasis Type="Italic">Fagus</Emphasis> <Emphasis Type="Italic">sylvatica</Emphasis> L. in NW Iberia

Our aim is to determine the population dynamics of Fagus sylvatica L. during the last 4,000 cal. BP in NW Iberia and the causes of its spatial and temporal patterns, previous palaeoecological studies having shown that between the Upper Pleistocene and the recent Holocene Fagus survived in this region. A number of pollen sites have allowed a reconstruction of the regional dynamics of Fagus from the Last Glaciation to the present. Specifically, two high-resolution pollen sequences located in both extremes of the Cantabrian region were analysed to discuss the beech forest dynamics during the last four millennia. Beech pollen percentages increased progressively to dominant species levels in eastern Cantabria, but only brief, minor increases are recorded in the west, where they never exceeded 2%. The expansion in the east shows three well-defined stages: an initial increase that lasted up to about 2,500 cal. BP, coinciding with a general increase in total tree pollen throughout the Cantabrian Mountains; a stage lasting between 2,500 and 1,500 cal. BP, in which Fagus pollen levels fluctuated while total tree pollen percentages began to decline and Ericaceae to increase; and a final further increase peaking around 1,250 cal. BP. The first stage (ca. 4,000–2,500 cal. BP) probably formed part of the final ascent of the tree line at the end of the mid-Holocene as the consequence of climatic improvement. Its maintenance during the second stage, while other tree species began to recede under unstable environmental conditions, is attributable to displacement of other genera such as Corylus and Quercus. Its final peak may have been facilitated by human disturbance of woodland, Fagus being a competitive species readily able to take advantage of such disturbances. That no such process occurred in the western Cantabrian area may be due to both the direct biological influence of harsher climatic conditions, and the lack of interest by human populations in settling highlands, which is attributable both to this climatic factor and to the fact that, compared with the east, this area has a greater extent of lowland and wide flat valleys where settlements were concentrated.     

A mid-Holocene vegetational and anthropogenic record in the Guanabara Bay region,Rio de Janeiro State,SE Brazil,assessed by palynological and charcoal data

Palynological and charcoal fragment analyses of Guanabara Bay sediments, as well as radiocarbon dating, were carried out on one 220 cm long sedimentary core collected from the northeast sector of the bay, near the São Gonçalo coast. This study aims at recognising and explaining the environmental history of this region during the mid-Holocene, and to identify the anthropogenic influences on it. The palynological data indicate the predominance of ombrophilous forest vegetation in the Guanabara Bay Hydrographic Basin at c. 6500 calendar years bp. During this period (pollen zone 1), the concentrations of pollen grains and spores may still have been controlled by the Holocene Maximum Transgressive Event. After a phase of low concentrations of palynomorphs, there was a considerable increase in the accumulation patterns of pollen and spore grains (pollen zone 2). This increase can probably be related to the retreat of the sea level event after the Holocene Maximum Transgressive Event. The 75 cm of the core top (pollen zone 3) provide clear evidence of human influence in the area, which is inferred from the significant reduction in ombrophilous forest pollen grains, the significant increase in herbaceous pollen grains, the presence of exotic pollen types (Eucalyptus and Pinus), and high concentration of carbonaceous particles.     

The vegetational history of the northern Apennines, Italy: information from three new sequences and a review of Regional vegetational change

Abstract. The results of pollen analysis and radiocarbon dating are presented from three northern Apennine sequences; Lago Padule in northern Tuscany and Lago Pratignano and Ospitale in the Emilia-Romagnan Apennines. This is the first detailed pollen stratigraphic information from sites in Emilia-Romagna and north Tuscany and extends eastwards the area from which information on vegetational history is available. The sequence from Lago Padule is one of the most complete Holocene records known from the northern Apennine region. Lago Pratignano has the deepest sequence of organic sediments (1544 cm) and the fastest rates of sediment accumulation (up to 28 cm per 100 years) providing the highest resolution record for the mid to late Holocene periods in the region. High rates of sedimentation have also occurred at Ospitale where organic sediments are 780 cm deep and began to form at approximately 5500 bp. The record from Lago Padule is compared with Holocene records from two nearby sites and a series of Regional Pollen Assemblage Zones is defined for the eastern area of the northern Apennines. The main features of vegetational change identified are: (i) a‘pioneer’phase of rapid forest development during the early Holocene followed by the establishment of an upper forest belt dominated by Abies, and a belt of mixed deciduous forest at lower altitudes; (ii) the appearance and rapid expansion of Fagus between approximately 5200 bp and 2900 bp forming a mixed Abies-Fagus association in the upper forest belt; and (iii) the overall reduction of forest cover, and dominance of Fagus in the arboreal vegetation from around 2900 bp. The scheme of Regional PAZs for the eastern area is used as a framework for the review of pollen stratigraphic information and radiocarbon dates from other sites in the northern Apennine region. Characteristics of pollen records which can be identified in sequences from across the region are identified and the chronology of similar changes in pollen stratigraphy is examined. The scheme of four regional PAZs for the Holocene period is shown to be valid for the entire northern Apennine region. The examination of a series of pollen records shows that Fagus appeared earlier in the western than the eastern part of the region during the mid Holocene and became dominant in the northern Apennine forests post 3000 bp. The impact of anthropogenic activity and climatic change on the spread and development of Fagus are discussed. The palynological evidence which is now available from the northern Apennines is compared with information for the region shown in the‘European pollen maps’of Huntley & Birks (1983). This study provides an updated review of the representation of different tree taxa in Holocene pollen records from the northern Apennines and illustrates the role of the northern Apennines as a refugium for trees during the Wurmian Lateglacial.     

Late quaternary vegetation dynamics and human impact on Alexander Selkirk Island, Chile

Aim To reconstruct the history of vegetation and environments using pollen, charcoal and sediment analysis, and to identify the timing and nature of climate change and human impact on the vegetation of a remote Pacific island. Location Cerro de Los Inocentes, 1000 m above sea level, Alexander Selkirk Island (33°45′S, 80°45′W), Chile. The westernmost island of the Juan Fernandez Archipelago, south‐east Pacific Ocean. Methods A 150‐cm long sediment core comprising 87 cm dark brown peat overlying 63 cm of yellow grey clay was extracted from a shallow depression on the southern slopes of Cerro de Los Inocentes. Pollen, charcoal, sediment and accelerator mass spectrometry radiocarbon analyses were used to construct a record of vegetation change through time. Numerical analysis of multispecies data allowed the classification of fossil assemblages into distinct pollen zones. Results Pollen and spores are preserved throughout the sediment with high concentrations coinciding with the beginning of organic sediment accumulation at around 8000 ¹⁴C yr BP. Prior to 8000 ¹⁴C yr BP, the deposition of clays, presumably from upslope erosion, occurred in a landscape sparsely vegetated by grasses, ferns and Pernettya rigida heath, including several plants that are only found 100–200 m above the site today (Zone CI‐1). After 8000 ¹⁴C yr BP, a P. rigida heath was the dominant vegetation (Zone CI‐2). A shift to a wet heath–shrubland (Zone CI‐3) occurred at 6000 ¹⁴C yr BP and was followed by a transition to a treefern–shrubland mosaic accompanied by periodic burning (Zone CI‐4) after 4500 ¹⁴C yr BP. The impact of human occupation is evident in Zone CI‐5 at 450 ¹⁴C yr BP with the loss of forest species, increased burning and invasion of the exotic plant Rumex. Main conclusions The pollen and charcoal record provides the first evidence of vegetation changes spanning at least the last 8000 ¹⁴C yr BP from the high altitude environment of Alexander Selkirk Island. Prior to 8000 ¹⁴C yr BP, the altitudinal ranges of different plant species may have been suppressed by a cooler and drier climate. Increasing precipitation and temperatures at the end of the last glacial period may have mobilized exposed sediments in a sparsely vegetated upland environment, altering local drainage patterns, eventually leading to slope stabilization and deposition of organic detritus under an increasing density of heath and shrub vegetation. The subalpine heath–shrubland persisted until 4500 ¹⁴C yr BP when first evidence for sustained burning is found in association with the establishment of a more open treefern–shrubland vegetation pattern. In the absence of human occupation at this time, the influence of increased climatic variability associated with more frequent El Niño‐Southern Oscillation events during the mid to late Holocene is considered one of the main driving forces behind increased vegetation disturbance during this period. The record provides evidence that island vegetation patterns have been highly dynamic over millennial to decadal time‐scales and that the flora has persisted through periods of rapid and major climate change. This changed with the discovery of the island by European explorers in the late sixteenth century and the subsequent introduction of goats and exploitation and burning of forests, which resulted in the progressive destruction of native vegetation and the invasion of introduced plants. There is evidence that reduced burning and control of the goat population within the last 50 years has resulted in marginal recovery of some high altitude native plant species.     

Holocene coastal vegetation changes at the mouth of the Amazon River

Wetland dynamics in the eastern Amazon region during the past 7000 years were studied using pollen, textural and structural analyses of sediment cores, as well as AMS radiocarbon dating. Four sediment cores were sampled from Marajó Island, which is located at the mouth of the Amazon River. Marajó Island is covered mainly by Amazon coastal forest, as well as herbaceous and varzea vegetation. Three cores were sampled from Lake Arari, which is surrounded by herbaceous vegetation flooded by freshwater. One core was sampled from a herbaceous plain located 15 km southeast of Lake Arari. Pollen preservation in the sedimentary deposits from this lake and from its drainage basin suggests significant vegetation changes on Marajó Island during the mid- and late-Holocene. Between 7328–7168 and 2306–2234 cal. yr BP, mangrove vegetation was more widely distributed on the island than it is today. During the past 2306–2234 cal. yr BP herbaceous vegetation expanded. Sedimentary structures and pollen data suggest a lagoon system until ~ 2300 cal. yr BP. The current distribution of mangroves along the Pará littoral, together with the presence of mangrove pollen and the sedimentary structures of the cores, indicates greater marine influence during the mid-Holocene. This may be attributed to the association between the eustatic sea-level change and the dry period recorded in Amazonia during the early- and mid-Holocene, followed by a wet phase over the past 2000 years.     

Phillips Spring, 23HI216:

Abstract

The Phillips Spring Site is situated on a Holocene terrace of the Pomme de Terre River in northern Hickory County, Missouri. Eleven. radiocarbon dates provide a good chronologie framework for the four cultural components recognized at the site. There are three Archaic components which span the period 4280 to 1990 BP. The initial Archaic occupation coincides with the establishment of the present vegetation pattern in the area. A single Late Woodland assemblage, dating from 1410 to 1000 BP, is comparable in cultural content to components of the HighlandAspect.     

Late Pleistocene and Holocene whale remains (Cetacea) from Denmark and adjacent countries: Species,distribution, chronology,and trace element concentrations

We describe and review the subfossil whale bones (mammalian order Cetacea) material from the southern Scandinavian area, that is, Skagerrak, Kattegat, the inner Danish waters and the southwestern Baltic Sea. Fifteen species were identified from the subfossil records of which all, except for the bowhead whale (Balaena mysticetus), have also been encountered in the modern times. Fifty-one specimens were radiocarbon dated covering 12 of the subfossil species. The dates fell in three distinct clusters with a few specimens before the last glacial maximum (LGM), a large group between LGM and the Pleistocene/Holocene boundary (ca. 17.0–11.7 cal. kyr BP), and another large group from ca. 8.0 cal. kyr BP onward. Seventeen of the radiocarbon dated specimens have been subjected to trace element analysis by Instrumental Neutron Activation Analysis. Cross plots of the concentrations of Fe and Zn, and Fe and Co show that it is possible to distinguish crayfish eaters from fish/squid eaters. This can be used as a novel and independent method for the determination to species of whale remains of otherwise uncertain speciation.     

Chronological and Isotopic data support a revision for the timing of cave bear extinction in Mediterranean Europe

Abstract

The Cave Bear, Ursus spelaeus (sensu lato), was one of many megafaunal species that became extinct during the Late Pleistocene in Europe. With new data we revisit the debate about the extinction and paleoecology of this species by presenting new chronometric, isotopic and taphonomic evidence from two Palaeolithic cave bear sites in northeastern Italy: Paina Cave and Trene Cave. Two direct radiocarbon dates on well-preserved collagen have yielded ages around 24,200–23,500 cal yr BP, which make them the latest known representatives of the species in Europe. The carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic values of bone collagen exhibit values similar to those of older cave bears from Swabian Jura and France, suggesting that the feedings preferences of cave bears remained unchanged until the disappearance of this species in Europe. Several bear remains preserved traces of human modification such as cut marks, which enables a reconstruction of the main steps of fur recovery and the butchering process. The broad range of plant types available and the favorable location of Berici Hills may have played an important role in the range expansion of cave bears and their interaction with the Paleolithic hunters settled the same area.     

History of Late Holocene vegetation at Quintana Roo,Caribbean coast of Mexico

A pollen record of a Late Holocene sediment core from the Mexican Caribbean coast (Quintana Roo) shows the development and changes of a mangrove system. Humid conditions seem to have persisted for the period approximately 2500–1500 ¹⁴C yr BP (pollen zone I), and mangrove Rhizophora mangle dominated with a good representation of elements from the nearby semi-evergreen tropical forest. During the period approximately 1500–1200 ¹⁴C yr BP (pollen zone II) the mangrove Conocarpus erecta dominated. R. mangle almost disappeared and other taxa appeared, suggesting drier climatic conditions and generally more open vegetation. This dry period coincided with the period of the Maya cultural decline. The following period (pollen zone III, approximately 1200–1000 ¹⁴C yr BP) was characterized by the recovery of R. mangle, indicating more humid conditions than in the preceding pollen zone. Pollen zone IV (approximately 1000 ¹⁴C yr BP till present) suggests a drier period reoccuring with C. erecta; this marks the transition to present day conditions.     

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.     

Relating postglacial relict plants and Holocene vegetation dynamics in the Balearic Islands through field surveys,pollen analysis and GIS modeling

Abstract

An inventory of the current Balearic plants occurring in mesophyllous environments, with climatic conditions similar to those in the first half of the Holocene, was compiled. The presence of these floristic elements, extending mainly into the postglacial time, has been related to pollen records of different localities in the Balearic Islands. GIS techniques have been applied in order to map the past and the present-day vegetation suitability of some of these mesophyllous species using pollen surface samples, forest inventory data and Digital Climatic Models. We integrated the information provided by field survey, pollen records and suitability mapping in order to discuss the vegetation dynamics of different habitats. We focused on the nature and the possible causes of the vegetation landscape change that occurred approximately 5000 – 6000 uncal. years BP, when Fagus, Corylus and Buxus formations were replaced by xeric-type formations with Olea dominance.     

Visualisation of transglutaminase-mediated cross-linking activity in germinating pollen by laser confocal microscopy

Abstract

Transglutaminases (TGs) are a multigenic family of calcium-dependent protein cross-linking enzymes, which are present in animal and plant cells. We have previously reported the presence of TGs in the cytosol and, more recently, in the cell wall of Malus domestica pollen, where it may be involved in pollen germination and pollen–stylar interactions. In this report we describe a simple method for the in situ visualisation of TG activity in germinating pollen. The method is based on the incorporation, mediated by pollen TG, of a fluorescently labelled exogenous diamine substrate of TG (fluorescein-cadaverine) into endogenous pollen substrates. Following the in situ TG activity reaction, the presence of cross-linked pollen proteins was visualised in fixed specimens of germinated pollen by laser confocal microscopy. Our data indicate the presence of TG cross-linking activity mainly at the apical part of the pollen tube, in the region proximal to the grain, and in the pollen grain itself. In planta, the products of this activity may provide strength to the pollen tube migrating through the style.     

A Compendium of Radiocarbon Dates for Iowa Archaeological Sites

Abstract

This report represents a compendium of radiocarbon dates for archaeological sites in the state of Iowa. The compendium is in tabular form and contains the following information: (1) the site name and number; (2) the radiocarbon date in both BP and BC/AS; (3) the laboratory sample number; (4) the type of sample or material dated; (5) cultural affiliation; and (6) published and unpublished references pertaining to the date and to the site or culture.     

Scanning electron microscopic studies of Centaurea L. s.s. pollen

Abstract

The purpose of this study is to analyse, by means of Scanning Electron Microscopy (SEM), the validity of the typification of the pollen of Centaurea L. s.s., carried out by Wagenitz (1955) with light microscopy and based on the exine structure and sculpturing. The pollen of six species have been analyzed: one species for every type of pollen present in Italy: C. sempervirens L., C. alpina L., C. scabiosa L., C. alba L., C. montana L., C. cyanus L.

The validity of the pollen typification suggested by Wagenitz has been confirmed also at the ultramicroscopic level. The ultrastructure and the sculturing of the sporoderm are described in detail and some discrepancies, mainly due to the different potentialities offered by the two methods, are pointed out.     

Flowering and morphological characterization of Dendrocalamus asper androecium and pollen grains

Abstract

Little is known about the reproduction of Dendrocalamus asper because it flowers only every 100 to 120 years. In the present work we describe some reproductive features of this bamboo and characterise flowers and pollen at various developmental stages. Number of pollen grains and ovules per flower, pollen/ovule ratio, in vitro twinning and pollen grain viability in vivo were evaluated and the different stages of floral development identified. Further, we performed a morphological analysis of androecium and pollen development. Seven distinct stages of flower development were identified; four initial stages, a pre-anthetic stage, and two stages of anthetic. Dendrocalamus asper pseudospikelets avoid inbreeding by means of protogyny. The floral and pollen characteristics suggest that the species is anemophilous. The ultrastructural characteristics of free microspores (stage two of floral development), vacuolated microspores (stage five) and mature pollen (anthetic) were analysed. During maturation, pollen grains accumulate larger and more numerous amyloplasts and organelles such as mitochondria. Pollen disperse in the tricellular development stage. Pollen is monoporate with an operculum-like pore, with a rugulate structure and a spinose tectum.