Human impact on Mediterranean wetland Coleoptera: an historical perspective at Tourves (Var,France)

Very little is known about the Neolithic human impact on the coleopteran fauna in the Mediterranean region. The site of Tourves provides an exceptional opportunity to document this major event in Provence because it offers a continuous upper Holocene sedimentary record, showing unambiguous pollen signals for anthropic activities during the Atlantic and Subboreal periods. The level dated 4310 BP is marked by a drastic change in the coleopteran assemblages: a rich marshy fauna is suddenly replaced by an impoverished fauna in which running-water elements suggest a change in the hydrological regime, probably induced by drainage of the site which may be attributed to human activities. Some wetland species such as Odacantha melanura and Cerapheles lateplagiatus, present below the level dated 4310 years BP, are now extinct in the area.     

Palynological evidence for drier phases during the historical period recorded in the Etang de Berre lagoon,south-eastern France

A pollen profile from Marais du Sagnas at the northern edge of the Etang de Berre lagoon, west of Marseille, is compared and correlated with a profile (C10) from the southern margin of the lagoon. This new profile extends the pollen record for the area to recent times. The palaeoecological data now available indicate distinct phases of marine influence in the lagoon from about 900 A.D. (non-calibrated) to the 16/17 century. These correspond to historically known drier periods during which it appears that reduced freshwater input facilitated increased influx of saline water.     

天山乌鲁木齐河源区3.6 ka BP以来的植被变化和环境变迁:以大西沟剖面为例

天山乌鲁木齐河源区大西沟剖面孢粉鉴定结果表明:在3.6～3.2 ka BP,该区气候较今温暖湿润;在3.2～2.0 ka BP,气候变为寒冷干燥,这一时期乌鲁木齐河源地区曾出现一次冰进;在2.0～1.4 ka BP,气候又转为暖湿;在1.4～0.5 ka BP,出现了3.6 ka BP以来气候最适宜的时期.整个剖面自下而上都有一定量的淡水水生植物出现,这反映了该剖面3 ka BP以来一直处于淡水沼泽的环境中.通过对云杉属生态习性、传播特性等综合分析,认为剖面中的云杉丰值可能与林线上移、山谷风搬运以及冰川退缩等有一定的相关性.通过对孢粉样品中炭屑浓度统计以及磁化率测试结果的综合研究,提出在0.5 ka BP左右,该地区可能出现过多次火灾;炭屑的峰值可能与人类活动有关.     

The potential of stomata analysis in conifers to estimate presence of conifer trees: examples from the Alps

To estimate whether or not a plant taxon found in the fossil record was locally present may be difficult if only pollen is analyzed. Plant macrofossils, in contrast, provide a clear indication of a taxon’s local presence, although in some lake sediments or peats, macrofossils may be rare or degraded. For conifers, the stomata found on pollen slides are derived from needles and thus provide a valuable proxy for local presence and they can be identified to genus level. From previously published studies, a transect across the Alps based on 13 sites is presented. For basal samples in sandy silt above the till with high pollen values of Pinus, for example, we may distinguish pine pollen from distant sources (samples with no stomata), from reworked pollen (samples with stomata present). The first apparent local presence of most conifer genera based on stomata often but not always occurs together with the phase of rapid pollen increase (rational limit). An exception is Larix, with its annual deposition of needles and heavy poorly dispersed pollen, for it often shows the first stomata earlier, at the empirical pollen limit. The decline and potential local extinction of a conifer can sometimes be shown in the stomata record. The decline may have been caused by climatic change, competition, or human impact. In situations where conifers form the timberline, the stomata record may indicate timberline fluctuations. In the discussion of immigration or migration of taxa we advocate the use of the cautious term “apparent local presence” to include some uncertainties. Absence of a taxon is impossible to prove.     

Towards the reconstruction of the Holocene vegetation history of Lower Provence: two new pollen profiles from Marais des Baux

Two new¹⁴C-dated Holocene pollen profiles from Marais des Baux, Bouches-du-Rhône, France, are presented. The record begins in the Younger Dryas, when the vegetation consisted mainly of grasses and mugwort (Artemisia). The Preboreal was marked by a transitory expansion of pine forests and was followed by the establishment of a rich deciduous oak-forest that included hazel (Corylus) and elm (Ulmus). During the Boreal, hazel played a dominant role within the oak-forest. The oak forests, which includedQuercus ilex, achieved a major expansion during the Atlantic period. The Subboreal was characterised by the regional establishment of, firstly, fir (Abies) and then beech (Fagus). The spread and expansion of beech coincides with the first clear evidence for farming. Agricultural activities brought about the decline of deciduous oak-forest. During the Subatlantic, forests in the vicinity of Marais des Baux were cleared for farming. Cereal growing, which included rye cultivation, was of considerable importance. Three noteworthy characteristics that serve to differentiate the Holocene vegetation history of the low-lying Provence region from other French regions are as follows: 1) the early establishment (from the onset of Preboreal) of low altitude mixed forest; 2) the expansion during the Subboreal of fir and beech in low altitude areas with a Mediterranean climate and, 3) the exceptional taxonomic richness of the pollen assemblages (120 identified taxa) and the presence of borealalpine and Euro-Siberian taxa that no longer exist in Lower Provence.     

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.     

A comparison of modern and presettlement pollen from southern Michigan (U.S.A.)

Use of samples of modern pollen to interpret assemblages of fossil pollen requires that the effects of man's impact be identified in the modern pollen. A comparison of the modern and presettlement pollen in 23 short cores taken within the lower peninsula of Michigan reveals a varied effect of man's activities on the vegetation. When obvious indicators of human activity (such as ragweed pollen) are removed from the pollen sum, many differences in the composition of the arboreal pollen are still evident between presettlement and modern records. When compared to presettlement data, birch, elm, and willow pollen in the modern data appear in proportionately higher quantities throughout the state, whereas beech, maple, and hemlock are in lower quantities. Within the region of primeaval pine forests, white pine values are much lower and oak values show an increase. Despite these differences in the pollen record, the modern pollen reflect the same basic patterns in the vegetation as the presettlement pollen. Principal component analysis shows the same patterns to exist in the modern data as are in the presettlement pollen.     

The Bias and Signal Attenuation Present in Conventional Pollen-Based Climate Reconstructions as Assessed by Early Climate Data from Minnesota,USA

The inference of past temperatures from a sedimentary pollen record depends upon the stationarity of the pollen-climate relationship. However, humans have altered vegetation independent of changes to climate, and consequently modern pollen deposition is a product of landscape disturbance and climate, which is different from the dominance of climate-derived processes in the past. This problem could cause serious signal distortion in pollen-based reconstructions. In the north-central United States, direct human impacts have strongly altered the modern vegetation and hence the pollen rain since Euro-American settlement in the mid-19^th century. Using instrumental temperature data from the early 1800s from Fort Snelling (Minnesota), we assessed the signal distortion and bias introduced by using the conventional method of inferring temperature from pollen assemblages in comparison to a calibration set from pre-settlement pollen assemblages and the earliest instrumental climate data. The early post-settlement calibration set provides more accurate reconstructions of the 19^th century instrumental record, with less bias, than the modern set does. When both modern and pre-industrial calibration sets are used to reconstruct past temperatures since AD 1116 from pollen counts from a varve-dated record from Lake Mina, Minnesota, the conventional inference method produces significant low-frequency (centennial-scale) signal attenuation and positive bias of 0.8-1.7°C, resulting in an overestimation of Little Ice Age temperature and likely an underestimation of the extent and rate of anthropogenic warming in this region. However, high-frequency (annual-scale) signal attenuation exists with both methods. Hence, we conclude that any past pollen spectra from before Euro-American settlement in this region should be interpreted using a pre-Euro-American settlement pollen set, paired to the earliest instrumental climate records. It remains to be explored how widespread this problem is when conventional pollen-based inference methods are used, and consequently how seriously regional manifestations of global warming have been underestimated with traditional pollen-based techniques.     

天山乌鲁木齐河源区3．6ka BP以来的植被变化和环境变迁：以大西沟剖面为例

天山乌鲁木齐河源区大西沟剖面孢粉鉴定结果表明：在3．6～3．2ka BP,该区气候较今温暖湿润;在3.2～2．0ka BP,气候变为寒冷干燥,这一时期乌鲁木齐河源地区曾出现一次冰进;在2．0～1．4ka BP,气候又转为暖湿;在1．4～0．5ka BP,出现了3．6ka BP以来气候最适宜的时期。整个剖面自下而上都有一定量的淡水水生植物出现,这反映了该剖面3ka BP以来一直处于淡水沼泽的环境中。通过对云杉属生态习性、传播特性等综合分析,认为剖面中的云杉丰值可能与林线上移、山谷风搬运以及冰川退缩等有一定的相关性。通过对孢粉样品中炭屑浓度统计以及磁化率测试结果的综合研究,提出在0．5ka BP左右,该地区可能出现过多次火灾;炭屑的峰值可能与人类活动有关。     

Contribution of upwind pollen sources to the characterization of Juniperus ashei phenology

Local and long-range components of Juniperus ashei pollen deposition were isolated to provide a more accurate record of local pollination activity in the Arbuckle Mountains of south central Oklahoma. An aerobiological sampler recorded airborne pollen concentrations and deposition at the sample site from mid-December 1998 to the end of January 1999. Grid-based weather data was used to model the movement, position, and elevation (air mass trajectories) across the region. While a normal concentration distribution is expected for a pollination event at a single site, "very high" concentrations (>1500 pollen grains per cubic meter) creating "peaks" in the deposition record were identified using bi-hourly sample analysis of the pollen registrations in the sampler. These occurrences happened over a 2 1/2 week period beginning January 11 and are coincident with the occurrence of southerly winds throughout the region. Modeled trajectories indicate that the air masses associated with those occurrences traveled at ground level through the J. ashei population on the Edwards Plateau, some 200 kilometers to the south in Texas, then gained altitude prior to crossing the sample site, thus introducing a long-range pollen component at the sample site. Peaks with "high" concentrations (90 to 1500 pollen grains per cubic meter) were evaluated using the same methodology. Those peaks associated with trajectories having the potential of introducing a long-range component to the pollen deposition record were removed from the aerobiological record. The resulting adjusted aerobiological record shows a more normal pollen concentration distribution, reduced hourly variability, and a marked shift in the pollination initiation date. Based on the comparison of non-adjusted and adjusted aerobiological records, contributions from upwind pollen sources account for 55% of the total pollen record.     

Establishing a fossil record for the perianthless Piperales: Saururus tuckerae sp. nov. (Saururaceae) from the Middle Eocene Princeton Chert

Investigations of small permineralized flowers from the Middle Eocene Princeton Chert, British Columbia, Canada have revealed that they represent an extinct species of Saururus. Over 100 flowers and one partial inflorescence were studied, and numerous minute perianthless flowers are borne in an indeterminate raceme. Each flower is subtended by a bract, and flowers and bracts are borne at the end of a common stalk. Five stamens are basally adnate to the carpels. Pollen is frequently found in situ in the anthers. Examined under SEM and TEM, pollen grains are minute (6-11 μm), monosulcate, boat-shaped-elliptic, with punctate sculpturing and a granulate aperture membrane. The gynoecium is composed of four basally connate, lobed carpels with recurved styles and a single ovule per carpel. Flower structure and pollen are indicative of Saururaceae (Piperales), and in phylogenetic analyses using morphological characters, the fossils are sister to extant Saururus. The fossil flowers are described here as Saururus tuckerae sp. nov. These fossil specimens add to the otherwise sparse fossil record of Piperales, represent the oldest fossils of Saururaceae as well as the first North American fossil specimens of this family, and provide the first evidence of saururaceous pollen in the fossil record.     

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.     

Vegetation history of Lago Battaglia (eastern Gargano coast,Apulia, Italy) during the middle-late Holocene

A pollen and charcoal record from Gargano (southern Italy) provides new information on the vegetation history and environmental change in southern Italy during the middle to late Holocene. The chronological framework is provided by six AMS radiocarbon dates carried out on plant macroremains. Pollen diagrams record a Mediterranean vegetation along the coastland and a stable mixed oak forest at higher elevations between ca. 5900 and 4200 cal b.p. A sharp and dramatic fall of tree pollen concentrations and a change in fire frequencies occurred from approximately 4200 cal b.p. suggesting a climate change towards drier conditions. This event is coherent with regional and extra-regional palaeoclimatic records that suggest that a mid-Holocene dry period was experienced in southern Italy, southern Spain, and perhaps further afield. Human impact on vegetation seems to have occurred since about 2700 cal b.p.     

Late Quaternary environmental history of the south-eastern Tibetan Plateau inferred from the Lake Naleng non-pollen palynomorph record

A 17.81 m sediment core from Lake Naleng, a freshwater lake in the south-eastern part of the Tibetan Plateau was examined for its non-pollen palynomorph (NPP) composition. The frequencies of 15 NPPs and three aquatic pollen types were determined in 160 samples. Since the origin of several NPP types is still unknown, multivariate analysis, supported by findings from the corresponding fossil pollen flora, was carried out to extract information about their ecological environments. The analysis allowed a classification of all microfossils in four groups of environmental response, which provided an approach to tracing lake history and palaeoclimatic changes in the area since the Late Glacial (since 17,700 cal years b.p.). Unstable lake conditions and a low organic productivity were reconstructed for the Late Glacial before 14,600 cal years b.p. with high inputs of terrestrial material. Climate conditions became wetter during the Bølling/Allerød interval indicated by high productivity in the lake. After a short climate deterioration (12,500–11,500 cal years b.p.), stable lake conditions were inferred from the record. During the late Holocene (since 2,700 cal years b.p.) changes in the NPP composition might be related to human impact, the latter being inferred from the pollen data through the presence of grazing indicators.     

Seasonal distribution of pollen in the atmosphere of Darwin,tropical Australia: Preliminary results

Pollen loads in the atmosphere of Darwin, a city located in the wet‐dry tropics of Australia, have been monitored for the period March 2004 to November 2005 as part of a large research program looking at atmospheric particles and human health. Seven pollen types dominate the pollen spectrum, the herbaceous families of Poaceae (grasses) and Cyperaceae (sedges), as well as several native tree and shrub taxa, Acacia, Callitris, Casuarina, Arecaceae and Myrtaceae. The pollen loads were found to have a strong seasonal component associated with the alternating wet (November to March) and dry (April to October) seasons of the region. Seventy percent of the yearly pollen load is captured during the dry season, with the peak pollen period occurring at the onset of the dry season (April–May) when most grasses are in flower. The daily pollen concentration decreases as the dry season progresses, accompanied by a change in composition; fewer herbaceous but increasing woody taxa. Preliminary health outcomes reveal a positive association between hay fever, Poaceae and Acacia pollen, as well as a significant association between total fungal spore concentrations and asthma. The Darwin record contrasts significantly with surveys conducted in the subtropical and temperate cities of Australia where temperature as opposed to rainfall and the prevalence of northern hemisphere exotic tree species have a greater influence over the seasonality and composition of the pollen loads.     

Vegetation in the mountains of northwest Iberia during the last glacial-interglacial transition

A new core taken from a site in the Sierra de Courel range of mountains in the northwest Iberian peninsula, Spain, enables a palaeoenvironmental reconstruction to be made of the biological events resulting from climatic changes and human activities during the last 17,000 years in the area. The sequence begins with a phase characterised by the dominance of Gramineae (Poaceae) and Pinus. A markedly arid period with prevalence of Artemisia pollen occurred between 17,5000 and 15,500 uncal. B.P. Subsequently, a succession of woodlands with Betula, Pinus and other mesophilous and thermophilous trees was recognised during the period 15,500-13,500 uncal. B.P. Between 13,500 and 10,300 uncal. B.P. herbaceous vegetation formations indicating moister conditions dominated the pollen record, although a maximum of Gramineae has been dated during the period 11,300-10,300 uncal. B.P. Comparison with other pollen data from neighbouring mountains allows an interpretation of the vegetation changes during the glacial/interglacial transition in the mountains of northwest Iberia. The Holocene pollen record from the site does not differ markedly from other records in the area, tree expansion occurring before 10,000 uncal. B.P. and high values of deciduous Quercus mixed with other trees and shrubs persisting until 3500 uncal. B.P., when increased human activities are shown by a fall of the tree pollen percentages. Received July 7, 1999 / Accepted May 22, 2000     

Vegetation history,human impact and climate change during the last 700 years recorded in annually laminated sediments of Lac Pavin,France

This paper presents a 1.80-m-long varved sediment record documenting the vegetation history by pollen and diatom analysis recovered from Lake Pavin, a volcanic crater lake in the Auvergne (French Massif Central). High-resolution sampling and a varve-based age model allowed the reconstruction of ecosystem responses to both regional climate change and human impact. According to the present varve chronology, the Lake Pavin sequence covers the last 700 years, thus representing the late Subatlantic period (i.e. from the Late Medieval onwards). The pollen record largely reflects intensive human influence (clearing, cultivation and grazing) on the lake surrounding area. The arboreal pollen spectrum of the entire sequence is co-dominated by Fagus and Quercus, except during the 20th century. However, whilst the Quercus record is relative stable, several major fluctuations are discernable in the Fagus curve. An increase in Pinus and Picea shortly before of the turn the 20th Century, indicates afforestation by conifers. The varve counting indicates that the most prominent signal in the Fagus curve occurs during the period between about 1540 and 1670 AD. During this interval, the initial drop in the Fagus curve is estimated to have taken 5–10 years, with the subsequent recovery occurring over a similar period. Since there is no clear evidence of tree population replacement, such rapid signals imply that the fluctuations in the Fagus curve reflect variations in pollen production, being influenced by the cooler temperatures experienced during a cold spell of the Little Ice Age.     

A late Holocene pollen diagram from the Megaris,Greece, giving possible evidence for cultivation of<Emphasis Type="Italic"> Ceratonia siliqua</Emphasis> L. during the last 2000 years

A late Holocene pollen profile from the Megaris on the eastern Gulf of Corinth shows a vegetation which was strongly influenced by human impact throughout. A Pistacia-Phillyrea maquis, which is reflected in the older parts of the profile, changed later to a more degraded vegetation type. In the uppermost part Pinus dominates the pollen spectrum. A continuous record of Ceratonia siliqua pollen older than cal a.d. 100 is of special interest.     

Human impact on vegetation at the Alpine tree-line ecotone during the last millennium: lessons from high temporal and palynological resolution

Three mires and a small lake in the Swiss and Austrian Alps were studied palynologically at high resolution, covering the last 1,000, 400, 50 and 1,200 years, respectively. Methodological lessons include: (1) Sub-decadal resolution in upper, little-decomposed peat layers reveals recurrent marked fluctuations in both percentages and influx of regional tree-pollen types, reflecting variations in pollen production rather than in plant-population sizes. (2) Intermittent, single-spectrum pollen maxima in samples of sub-decadal resolution indicate pollen transport in clumps. This type of pollen transport may remain unrecognized in sections with lower sampling resolution, which may then lead to inappropriate interpretation in terms of plant-population sizes. (3) The detection of short-lived phases of human impact in decomposed peat requires sampling intervals as close as 0.2 cm. (4) PAR (pollen influx) may reflect vegetation dynamics more faithfully than percentages. Reliable PAR, however, is difficult to achieve in Alpine mires due to past human impact on peat growth, even when complex depth–age modelling techniques are used. Critical comparison of PAR with percentages is therefore essential. (5) Careful consideration of spatial scales in pollen signals (local–regional and subdivisions) is essential for a realistic palaeo-ecological interpretation. Results in terms of past human impact on vegetation are summarized as follows: (1) Trends in pollen types reflecting regional human action are in general agreement with earlier findings for the western Swiss Alps, allowing for regional differences. (2) All mires in the Alps investigated here and in an earlier study experienced human impact during the last millennium. The studied small lake, lying in sub-alpine pasture, records forest dynamics at a lower elevation since a.d. 800.     

Is Phillyrea angustifolia L. (Oleaceae) an androdioecious species?

LEPART, J. & DOMMEE B., 1992. Is Phillyrea angustifolia L. (Oleaceae) an androdioecious species? Observations during two or three years on three natural populations of Phillyrea angustifolia growing in contrasting environments in southern France show that two distinct phenotypes occur in approximately equal proportions: hermaphrodites, which produce pollen and seeds, and males, which produce pollen only. The populations studied are thus morphologically androdioecious. Biometric investigation of the two morphs shows that they are clearly distinguished by (1) the shape of the stigma and (2) the ovary which is well developed in hermaphrodites and aborted in males. Neither size of anthers and corolla, nor pollen germination, differ between the two sexes. In the Camargue, where P. angustifolia is presently an invader, controlled crosses between hermaphrodites (selfing and inter-individual) are partially successful. In contrast, such crosses are sterile in the well-established population of the La Gardiole. Hence the Camargue population appears to be functionally androdioecious and La Gardiole functionally dioecious. This breeding system is particularly puzzling, since the occurrence of anemogamy and possible selfing do not fit classical explanations of androdioecy. The ability of hermaphrodites to be functionally male and female could be particularly adaptive in founding populations. Since functional hermaphroditism occurs in expanding populations of the Camargue population, we consider that the androdioecy of P. angustifolia could be a kind of leaky dioecism.