bluuebunny/crossref_metadata_2025 huggingface dataset:
Human-environment interactions during the Holocene: new data and interpretations from the Oban area, Argyll, Scotland
Authors: Macklin Mark G. , Bonsall Clive , Davies Fay M. , Robinson Mark R.
Published: January 2003

Investigations of the archaeological, geochemical, microscopic charcoal and palynological records from five localities in the Oban area, along an altitudinal transect from coast to upland, have provided new information on human–environment interactions during the Holocene. Some of the results are at variance with previous interpretations of Mesolithic human impacts and the timing of the transition to farming in Atlantic Scotland. High charcoal values and the occurrence of cereal-type pollen grains, which have commonly been used to infer human activity during the Mesolithic, appear in the Oban area at least to be related to climate change. However, the greater frequency of woodland-decline episodes in inland and upland areas prior to 5000 BP is more easily explained in terms of human impact. Archaeological and palynological evidence indicates that the Mesolithic–Neolithic transition in the Oban area occurred at c. 5000 BP and, on evidence from elsewhere in northern Britain, coincided with a marked shift to drier climatic conditions. Up until c. 1000 BP agricultural communities appear to have had comparatively little impact on the environment. Thereafter, there was rapid and permanent deforestation possibly linked to the development of a distinctive land-use strategy and settlement pattern that survived until the nineteenth century ad.
Establishing a chronology for the last 1000 years of laminated sediment accumulation at Lake Barrine, a tropical upland maar lake, northeastern Australia
Authors: Walker D. , Head M. J. , Hancock G. J. , Murray A. S.
Published: January 2003

Radiocarbon dates from the uppermost 115 cm of laminated mud beneath the centre of a small crater lake are affected by the residence-time in the marginal shallows of the organic detritus which, after transport to deep water, forms alternate layers in the sediment column. The delay is estimated from radiocarbon ages of source materials, trapped seston and the upper levels of the sediment column based on the ‘post-bomb’ atmospheric radiocarbon flux. The ‘contaminating’ component does not reside uniquely in any specific fraction of a mud sample, defined by alkali solubility and particle size, but is generally associated with the detrital layers. The lead-210 method, together with proxy indications from charcoal, exotic Solanum pollen and meteorological correlations, effectively replace radiocarbon for the dating of the sediment column from ad 1987 back to 1965. Beyond that, the selection of the youngest radiocarbon age from those in each of eight depth intervals leads to an acceptable estimate of accumulation rate to ad 1060.
The sensitivity of a Tanzanian crater lake to catastrophic tephra input and four millennia of climate change
Authors: Barker Philip , Telford Richard , Merdaci Ouassila , Williamson David , Taieb Maurice , Vincens Annie , Gibert Elisabeth
Published: January 2003

Diatom genera in many large East African lakes change little throughout the Holocene period suggesting relatively stable ecological conditions and some resilience to environmental change. Ecosystem stability is less common in smaller, more sensitive lakes, such as those within volcanic craters, where external impacts can cause abrupt and rapid fluctuations. A 4100-year diatom and cyanobacteria pigment record from Lake Massoko, a volcanic crater lake in southern Tanzania, is used to illustrate important switches in resource ratios following tephra deposition 1190 years ago. It is hypothesized that the tephra reduced the rate of P diffusion from the sediments and increased the Si:P ratio in the lake. A period of acute change in planktonic diatom communities resulted from the tephra impact and lasted c. 110 years. The magnitude of the change shown by the diatoms and their slow recovery from the tephra may be due in part to a coincident fall in lake level caused by a reduction in regional rainfall. The statistical significance of the tephra impact relative to that of catchment and climate change has been tested using variance partitioning and rate-of-change analysis. Multiproxy indicators show an important period of positive water balance 1700 ago and a relatively dry episode persisting between 1000 and 400 years ago. The lake ecosystem is shown to be highly sensitive to both climate change and tephra deposition.
Palaeolimnological evidence for marked Holocene environmental changes on Signy Island, Antarctica
Authors: Jones V. J. , Hodgson D. A. , Chepstow-Lusty A.
Published: January 2003

Lake-sediment cores from Heywood and Sombre Lakes on Signy Island (South Orkney Islands), Antarctica, have yielded a conformable radiocarbon chronology for the Holocene and a high-resolution record of environmental change. The lakes share a common climate and geology but have distinct catchments. This provides an opportunity for using lake sediments to differentiate between local, within lake/catchment, events and those at a regional scale. Analyses of various biological and physical remains from the lakes suggest that both catchments have undergone considerable changes during the last 5700 years. Macrofossils (moss and crustacean remains) are more abundant in the late Holocene, being associated with a period of high sediment accumulation, which is related to diatom evidence for more nutrient-rich conditions at the sites. This is interpreted as a response to a Holocene‘climate optimum' at c. 3800–1300 14C yr BP. The record is consistent with other lake, ice and ocean core studies, although the climate optimum appears to have persisted for a longer period at Signy Island.
River sedimentation and fluvial response to Holocene environmental change in the Yorkshire Ouse Basin, northern England
Authors: Taylor M. P. , Macklin M. G. , Hudson-Edwards K.
Published: January 2003

Holocene alluvial sediment sequences and floodplain geomorphological histories from three valley-floor sequences in the Yorkshire Ouse Basin have been determined using a variety of field evidence and laboratory methods: geomorphological mapping, sediment coring and trenching, physical and chemical analysis of sedimentary units, and 14C dating. The application of multiple methods has revealed contrasting phases of river erosion, alluviation and depositional styles during the Late Quaternary at each of the individual study reaches. The gravel bedded River Swale at Catterick has been characterized by progressive valley-floor incision during the late Holocene with major phases of incision occurring during the cooler and wetter phase of the 'Little Ice Age’. Within the last c. 245 years, substantial thicknesses (up to 2 m) of overbank alluvium contaminated by metalliferous mining have been deposited across thefloodplain. In contrast, floodplain development in the lower reaches of the River Swale at Myton and the River Aire at Beal has predominantly been one of relative channel stability and vertical aggradation. Here, low floodplain gradients, wide valley floors, stable channels and limited lateral floodplain erosion have combined to produce thick (c.10 m) sequences of finegrained alluvium deposited in overbank environments. Mining-related contamination in lowland floodplains is much lower than at Catterick with limited amounts of historically contaminated alluvium being deposited across the floodplain. Although environmental change has been important in controlling Holocene floodplain development, the upper and lower reaches of the Yorkshire Ouse basin have responded differently to these effects because of reach-scale geomorphic controls. Caution needs to be applied before relating broad-scale environmental change to river response across a whole river basin.
Environmental change and political-economic upheaval in precolonial western Uganda
Authors: Taylor D. , Robertshaw P. , Marchant R. A.
Published: January 2003

This paper reassesses available evidence for environmental and cultural changes in western Uganda since 1000 bc. The period of study includes the introduction of iron working in the region, as well as the transition to nucleated settlement patterns and the apparent decline of these settlements, prior to the colonial period. Several oscillations in climate conditions, from relatively dry to relatively wet, are recorded by palaeo-climate data. Some of these can be linked to variations in vegetation cover, apparent in pollen records from a number of locations. There is a difficulty in establishing cause–effect relationships here, because human impact can have a similar impact on moist forests to increases in climatic aridity. However, there are three cases where the explication of changes in climate, vegetation and the level of human impact are possible. The first occurred towards the end of the first millennium ad and coincided with the beginning of the Later Iron Age. This was a period of major changes in cultural relationships and settlement pattern, during which variations in environmental conditions may have influenced rather than forced a process of political centralization. Increased climatic aridity and problems of soil exhaustion may have driven a subsequent change in the pattern of settlement, towards the beginning of the ad 1500s. Agricultural shortfalls and consequent problems of food insecurity among large, sedentary populations, towards the end of a relatively dry period during the late ad 1600s and early 1700s, may explain the decline of nucleated settlements.
Holocene vegetation history at Vätsäri, Inari Lapland, northeastern Finland, with special reference to Betula
Authors: Mäkelä Eeva , Hyvärinen Hannu
Published: January 2003

A Holocene sediment series from a lake in the northern birch forest region of eastern Finnish Lapland was studied pollen-analytically. In addition to conventional pollen analysis, birch pollen measurements were carried out. Betula pollen diameters were measured systematically. The resulting size-frequency distributions were analysed statistically to infer their species composition and to reconstruct the local history of birch. The results indicate pine arrival about 7500 14C years BP. Even during its optimum period of 7000–6000 BP, pine cover seems to have been thin and discontinuous. Pine and birch started to retreat soon after the pine optimum. In the interpretation of the birch pollen-size frequency distributions, no continuous record of Betula tortuosa was found. B. pendula seems to have had a more northerly distribution in the past than it has today.
Variations in the carbon isotope composition of late-Holocene plant macrofossils: a comparison of whole-leaf and cellulose trends
Authors: Rundgren M. , Loader N. J. , Beerling D. J.
Published: January 2003

Stable carbon isotope measurements (δ13C) made on Quaternary sequences of terrestrial plant subfos sils are frequently used to infer palaeoclimatic trends. However, differential decomposition of individual con stituents during incorporation of plant material into lake sediments could influence these interpretations. There fore, we investigated down-core variations in the carbon isotope composition (δ13C) of subfossil leaves of Salix herbacea L., and their holocellulose component, from a late-Holocene ( c. 0–3300 years ago) site in northern Sweden. Locally weighted regression curves fitted to bothδ13C data sets showed similar but conserved temporal patterns of change, and there was no evidence for systematic shifts in the holocellulose yields or C:N ratios of leaves with age. Small d13C variations over the past 3300 years probably reflect natural variations in microclimate within the lake catchment area. This interpretation is quantitatively consistent with the variability determ ined from measurements made on leaves of modern S. herbacea plants growing at the same site. Overall these results imply that, under conditions of uniform decomposition,δ13C measurements made on late-Holocene sequences of whole leaves provide an interpretation of the pattern and direction of change consistent with that obtained from holocellulose isolated from the same leaves.
Late-Quaternary cryostratigraphy of a coastal cliff at Martha Point, southwest Banks Island, western Canadian Arctic
Authors: Worsley Peter
Published: January 2003

A 5 m thick unlithified sequence consisting of sands, silts and minor peats crop out in a coastal cliff within continuous permafrost. A well-exposed 70 m long section displayed a range of epigenetic ice wedges. These could be classified into three generations, each at a different stratigraphic level. The oldest was truncated by a major thaw unconformity which was overlain by a bed of highly involuted silts with peat clasts, interpreted as evidence of a deep palaeoactive layer and associated thermokarst. This bed forms part of a regionally extensive thermokarst phase, correlated with an early-Holocene Climatic Optimum. The other two ice-wedge horizons postdate the thermokarst event with the youngest approximating to the base of the modern active layer.
Allochthonous and autochthonous mire deposits, slope instability and palaeoenvironmental investigations in the Borve Valley, Barra, Outer Hebrides, Scotland
Authors: Ashmore P. , Brayshay B. A. , Edwards K. J. , Gilbertson D. D. , Grattan J. P. , Kent M. , Pratt K. E. , Weaver R. E.
Published: January 2003

This paper suggests that sediment depth-age anomalies, and the lithological and palaeoecological properties of a peat core from Borve mire on the Outer Hebridean island of Barra, reflect the episodic impacts of rapid mass-movement of superficial peats and mineral soils from the adjacent hillslopes in the period 3000 to 1750 14C years BP. Alternative explanations such as mismeasurement of radiocarbon or contamination by floods, are thought less likely. The research implies that there is a general need for caution in the interpretation of mire deposits from sites which are adjacent to steep peat-covered hillslopes and which have not been investigated with the support of substantial radiocarbon and lithological studies programmes. The environmental and vegetational history of this exposed and isolated Atlantic island is shown to have not been one of treeless homogeneity. A variety of deciduous and coniferous tree species colonized early in the Holocene, with distinctive birch-hazel woodland developing at one point in time. The landscape became increasingly treeless in the Bronze Age, with most but not all trees having been lost by the Medieval period. Valley side peats provide palynological evidence of pastoral and arable farming on poor soils in the Dark Age-Early Medieval period, at sites beyond the present limits of cultivation.
Drought and dust deposition in the West African Sahel: a 5500-year record from Kajemarum Oasis, northeastern Nigeria
Authors: Street-Perrott F. A. , Holmes J. A. , Waller M. P. , Allen M. J. , Barber N. G. H. , Fothergill P. A. , Harkness D. D. , Ivanovich M. , Kroon D. , Perrott R. A.
Published: January 2003

A high-resolution, multiproxy palaeolimnological record from the Manga Grasslands, northeastern Nigeria, spanning the last 5500 calendar years, reveals the episodic deterioration in Sahelian climate as significant biogeophysical thresholds were crossed. Desert-dust deposition began to increase 4700 cal. BP. Rainfall during the summer-monsoon season declined permanently after 4100 cal. BP. A further significant change in atmospheric circulation, giving rise to multidecadal to centennial-scale droughts and enhanced dust deposition, occurred 1500 cal. BP. Hence, the post-1968 Sahel drought is not unique. The prolonged arid episode that occurred around 1200–1000 cal. BP in Ethiopia, the Sahel and tropical Mexico may have been linked to an abrupt cooling event in the North Atlantic and to a cluster of intense El Niño-Southern Oscillation events in the Eastern Equatorial Pacific.
Climatic change in Chile at around 2700 BP and global evidence for solar forcing: a hypothesis
Authors: van Geel Bas , Heusser Calvin J. , Renssen Hans , Schuurmans Cor J.E.
Published: January 2003

Palaeoecological and geological evidence for changing atmospheric circulation patterns in Chile indicates that equatorward and poleward shifts of the Southern Westerlies (Pacific precipitation source) were an important factor during Weichselian and Holocene climate change. We focus on the evidence and possible causes of considerable climate change in the Holocene at around 2700 BP, which was associated with a steep rise in atmospheric radiocarbon content, indicating an abrupt decrease in solar activity. Climate change may have been caused by the lowering of solar irradiation through two amplifying factors, namely (1) increased cosmic ray intensity, stimulating cloud formation and precipitation, and (2) reduced solar UV intensity, causing a decline of stratospheric ozone production and cooling as a result of less absorption of sunlight. A decrease in the latitudinal extent of Hadley Cell circulation may have occurred with concomitant equatorward relocation of mid-latitude storm tracks, which brought about northward movement of vegetation belts and advance of glaciers.
Mongolian tree-rings, temperature sensitivity and reconstructions of Northern Hemisphere temperature
Authors: D'Arrigo Rosanne , Jacoby Gordon , Pederson Neil , Frank David , Buckley Brendan , Nachin Baatarbileg , Mijiddorj R. , Dugarjav Chultamiin
Published: January 2003

Much of northern Asia is lacking in high-resolution palaeoclimatic data coverage. This vast region thus represents a sizeable gap in data sets used to reconstruct hemispheric-scale temperature trends for the past millennium. To improve coverage, we present a regional-scale composite of four tree-ring width records of Siberian pine and Siberian larch from temperature-sensitive alpine timber-line sites in Mongolia. The chrono logies load closely in principal components analysis (PCA) with the first eigenvector accounting for over 53% of the variance from ad 1450 to 1998. The 20-year interval from 1974 to 1993 is the highest such growth period in this composite record, and 17 of the 20 highest growth years have occurred since 1946. Thus these trees, unlike those recently described at some northern sites, do not appear to have lost their temperature sensitivity, and suggest that recent decades have been some of the warmest in the past 500 years for this region. There are, however, comparable periods of inferred, local warmth for individual sites, e.g., in 1520– 1580 and 1760–1790. The percent common variance between chronologies has increased through time and is highest (66.1%) in the present century. Although there are obvious differences among the individual chrono logies, this result suggests a coherent signal which we consider to be related to temperature. The PCA scores show trends which strongly resemble those seen in recent temperature reconstructions for the Northern Hemi sphere, very few of which included representation from Eurasia east of the Ural Mountains. The Mongolia series therefore provides independent corroboration for these reconstructions and their indications of unusual warming during the twentieth century.
Multi-proxy Holocene palaeoclimatic record from a saline lake in the Canadian Subarctic
Authors: Pienitz Reinhard , Smol John P. , Last William M. , Leavitt Peter R. , Cumming Brian F.
Published: January 2003

Multi-proxy palaeolimnological analyses of a postglacial sedimentary sequence at a centennial-scale resolution from an athalassic saline lake in the Yukon were conducted to infer patterns of Holocene climatic change in the Canadian Subarctic, using sediment mineralogy and biostratigraphy (diatoms, pigments). Diatominferred quantitative estimates of palaeosalinity were obtained by use of transfer functions developed from a calibration set of 219 lakes from western North America. The sediment mineralogy and fossil pigments at the base of the core indicated a moderately deep non-stratified lake dominated by clastic influx, probably in a basin fed by glacial meltwater. The early-Holocene history ( c. 11 000–8100 14C yr BP) was characterized by a relatively deep mesosaline lake with diatom-inferred salinities approximating 20 g L-1. The occurrence of both aragonite and dolomite, as well as elevated concentrations of chlorophyll and carotenoid pigments, support the interpretation of deepwater anoxia and possibly strong chemical stratification. High concentrations of the chemically stable b-carotene suggest that total algal abundance was particularly high during the early Holocene, when planktonic Cyclotella cf. choctawhatcheeana and Chaetoceros muelleri were the most common diatom taxa. Relatively fresh (2–15 g L-1) eutrophic conditions prevailed during the mid-Holocene period ( c. 8000– 2000 yr BP), with four periods of alternating fresh and saline conditions. The diatom-inferred salinity profile reveals significant fluctuations within these cycles, but overall they indicate humid climatic conditions compared to today. Algal abundance is inferred to have declined three-fold relative to the early Holocene, particularly in the case of eukaryotic algae (e.g., diatoms, cryptophytes, chlorophytes). The recent history of the lake (about 2000 years BP until the present day) was marked by important changes in ionic composition (e.g., occurrence of gypsum and Mg-carbonates) and hydrologic conditions. The lakewater composition during the last two millennia was characterized by hypersaline Mg-SO4 brines. The palaeolimnological evidence from most proxies indicates a trend towards drier conditions during the past 2000 years. The various indicators reveal a complex history of frequent and rapid shifts in palaeosalinity and lake palaeoproductivity during the Holocene, and the effects of the Younger Dryas and ‘Little Ice Age’ episodes may be recorded in the palaeoclimate proxy data. The palaeoclimatic interpretation emerging from this high-latitude lake corroborates existing broad trends based on palynological studies in this region but provides evidence for more dynamic climatic change during the mid- and late Holocene.
Bransfield Basin fine-grained sediments: late-Holocene sedimentary processes and Antarctic oceanographic conditions
Authors: Fabrés J. , Calafat A. , Canals M. , Bárcena M. A. , Flores J. A.
Published: January 2003

The Antarctic Peninsula is sensitive to climatic change due to its northerly position and to the relatively reduced volume and character of its ice cover. High-resolution palaeoclimatic records from the Ant arctic Peninsula ice cores extend back only 500 years. A climatic record of 2850 years in the Bransfield Basin is investigated through the analysis of sediment gravity cores from the floor of the central subbasin (core GEBRA-1) and the slope of the eastern subbasin (core GEBRA-2). Sedimentological, mineralogical and geo chemical properties have been systematically measured, together with Accelerator Mass Spectrometry (AMS) radiocarbon dating. The fine-grained sediments result from two main processes: hemipelagic settling from resuspensions and primary productivity, and turbidity currents. Hemipelagic sediments were selected to investi gate the oceanographic and climatic conditions of the northern Antarctic Peninsula region during the last three millennia. Cold climatic periods are characterized by millimetric laminations and/or black layers with higher organic carbon, nitrogen and opal contents. Warm periods are recorded as massive to diffuse laminated facies with lower biogenic contents. The results include the ‘Little Ice Age’ (LIA) cold pulse as well as several 200– 300 year long fluctuations within the LIA and before this major climatic event of the Holocene.
Effects of burning and grazing on carbon sequestration in a Pennine blanket bog, UK
Authors: Garnett M. H. , Ineson P. , Stevenson A. C.
Published: January 2003

Terrestrial ecosystems contain large amounts of carbon (C) and have the potential to significantly increase atmospheric carbon dioxide (CO2) concentrations. Peatlands are particularly important for C storage, although little is known about the effects of anthropogenic activities on C balance in these ecosystems. Sheep-grazing and rotational burning are widely practised on blanket peat moorlands in the United Kingdom. The effects of these activities on C sequestration in peat has been investigated with a long-term randomized block experiment with treatments: (a) grazed + unburnt; (b) grazed + burnt every ten years; (c) ungrazed + unburnt. C accumulation under these treatments was compared by identifying a chronologically synchronous horizon within the peat common to all treatment plots. This fixed point was defined by the ‘take-off’ in concentration of spheroidal carbonaceous particles and was supported by the record of charcoal fragments. There was no significant difference in recent C accumulation rates between lightly grazed and ungrazed plots. In contrast, after 30 years there was significantly less C stored in the blanket peat in plots which had been burned every ten years. The results indicate that light sheep-grazing at this site did not affect rates of C accumulation in blanket peat, but decadal burning of moorland reduced C sequestration.
New radiocarbon dates from a Holocene aeolianite, Isla Cancun, Quintana Roo, Mexico
Authors: McLaren Sue , Gardner Rita
Published: January 2003

This paper reports on nine new radiocarbon dates from marine shells collected at various heights within a Holocene aeolianite sequence on Isla Cancun in the Yucatan Peninsula, Mexico. The ages obtained from the shells provide an improved understanding of some of the geomorphological and sedimentological processes operating during the upper mid-Holocene on Isla Cancun. Carbonate sand dunes were accreting at rates in the order of 0.28 cm yr-1 between about 3570 and 4000 years BP. By around 4000 years BP sea levels were close to present-day shorelines evidenced by the presence of marine shells (SRR-5790) within a small wedge of beach material cut into the Cancun aeolianite at a height of +1.5 m above present-day sea levels. Cessation of dune growth is known to have occurred before 2500 years BP as shells (SRR-5793a, SRR-5793b, SRR-5794a and SRR-5794b) from a midden deposit overlying the aeolianite provide a minimum age for the end of dune activity. Dune formation appears, therefore, to be associated with the end of the postglacial transgression in sea level. At least one other sample is thought to be from a midden and the dates obtained from this site provide information on localized human occupation in the area during the Holocene between 4082 and 2349 years BP.
Effect of pollen from regional vegetation on stand-scale forest reconstruction
Authors: Parshall Tim , Calcote Randy
Published: January 2003

To investigate the influence of regional pollen inputs on reconstructing local vegetation, we compared modem pollen assemblages deposited in forest hollow sediments from two study areas, Michigan and Wisconsin. Local forest-stand composition (within 50 m) at all sites is dominated by hemlock and northern hardwood trees, but the regional abundance of tree taxa in the two study areas is not the same. Modern pollen assemblages differ between the two study areas, corresponding with differences in regional vegetation. Oak and pine pollen are more abundant in Wisconsin samples, whereas sugar maple, birch and hemlock pollen are more abundant in Michigan samples. Pollen assemblages differed most between study areas for hardwood stands, reflecting lower pollen production of sugar maple and basswood, which exaggerates regional pollen inputs. However, within each study area, surface pollen assemblages are sufficiently different to permit differentiation of hemlock and hardwood stand types, suggesting that regional pollen inputs are similar on the scale of tens of kilometres. Therefore, stand-scale forest histories can be derived from forest-hollow sediments using modern analogues, but our results emphasize the importance of understanding the regional vegetation context and inferring how regional vegetation has changed in the past.
The Mjáuvøtn tephra and other Holocene tephra horizons from the Faroe Islands: a link between the Icelandic source region, the Nordic Seas, and the European continent
Authors: Wastegård Stefan , Björck Svante , Grauert Marianne , Hannon Gina E.
Published: January 2003

Six different tephra horizons were found in peat and lacustrine sediments on the Faroe Islands in the North Atlantic. Their geochemistry showed that they were of Icelandic origin. Three of these can be correlated with previously described tephra horizons from the Faroe Islands: the Saksunarvatn tephra ( c. 9000 BP), the Hekla-4 ( c. 3800 BP) and Hekla-Selsund ( c. 3600 BP). A previously unrecorded basaltic tephra dated to c. 5700-5300 BP was found in two lacustrine successions. This horizon is named the Mjáuvøtn tephra after Mjáuvøtn Lake on the island of Streymoy. Two further tephras were recorded: the basaltic phase of the ‘Landnám’ tephra (VIIa, c. AD 870s), and the rhyolitic Tjørnuvik tephra. These were found in sediments deposited shortly after the first phase of human settlement at Tjørnuvik, which is AMS dated to AD 675-861 (calibrated age). The Faroe Islands are an important link between the volcanic sources on Iceland, and the established tephrochronological frameworks on the British Isles, Scandinavia and Germany. Their position within a sensitive region of the northeastern branch of the North Atlantic Drift make the Faroe Islands ideal for registering climate changes during the Holocene. The establishment of a modern tephrochronology may provide a tool for more precisely dating and correlating regional climate events in and around the Nordic Seas.
A varve record of increased ‘Little Ice Age’ rainfall associated with volcanic activity, Arctic Archipelago, Canada
Authors: Lamoureux Scott F. , England John H. , Sharp Martin J. , Bush Andrew B.G.
Published: January 2003

Varved sediments from Nicolay Lake, Canadian High Arctic, record major summer rainfall events over the last five centuries. Increased incidences of summer rainfall occurred during the coldest periods of the ‘Little Ice Age’ and were strongly clustered in the years immediately following major volcanic events. Comparison of the summer rainfall and proxy air temperature records thus provides a fuller understanding of the nature and causes of natural climate variability in the Arctic. Study of the synoptic conditions associated with the two most recent large summer rainfall events suggests that they are associated with the incursion of cold low-pressure systems from the Arctic Ocean Basin. Volcanic activity may produce atmospheric conditions more conducive to the formation of such low-pressure systems, which generate rainfall at low elevations and summer snowfall at higher elevations, thus explaining the correlation between rainfall and summer snow accumulation recorded in ice cores from high-elevation ice caps.
A shift from natural to human-driven fire regime: implications for trace-gas emissions
Authors: Saamak Christopher F.
Published: January 2003

Vast aleas of the West Afiican savannas are burnied annua,iiv (lcnaCuLCt d U., 1991. Naural. lint ning-caused fires hiave existed for millions of years, but today 99",o, of the fires are of anthropogenic origin. The trace-gas emissions from these fires have not beein addressed with as much interest as the tropical-forest burninlgs. since the net CO, c0 eissions from savanna flies are zero. I'lossvxer. the burning of anx x cgetativx matter to a lesser or higher degree emits other importanit greenhouse or greenhouse-related trace gases such as Cl-4 and CO depending oni the burning efficiency of the fires. The but-ninig etfficiency of fire decreases with increased moistuire content, and recent findings have shown that the seasonal variation in non-CO, aases are A significanit as a finctioni of the varianice in the moisture content. Since natural fires occur xhen the fuel is diy, H Olocene and most human fires are ignited while the fuel is still moist, the slhift iu fire regime may hiave tripled the Research emissionis of non-CO2 gases.
Reconstruction of summer temperatures from tree-rings of Scots pine (Pinus sylvestris L.) in coastal northern Norway
Authors: Kirchhefer Andreas J.
Published: January 2003

At the coast of northern Norway, 69°N, tree-ring chronologies from Scots pine (Pinus sylvestris L.) were constructed at Forfjorddalen in the Vesterålen archipelago (AD 1358-1992), Stonglandseidet on Senja (AD 1548-1994) and Vikran near Tromsø (AD 1700-1992). All chronologies reflect July-August temperatures. At the most northern site, Vikran, the response was more confined to July temperatures, resulting in a strong tree-ring and climate signal. The chronology from a steep, south-facing slope at Stonglandseidet showed signs of drought sensitivity. At the most oceanic locality, Forfjorddalen, mild winters appear to suppress tree growth on a decadal scale. Growth variations were consistent between the three sites for 1700-1910 but the amount of low-frequency variability decreased towards the most oceanic site. The seventeenth century, the coldest period of the ‘Little Ice Age’, experienced three cycles of summer temperatures, with minima around 1605, 1640 and 1680. An extended warm period occurred around 1475-1540. Temperature reconstruction showed secular trends similar to those observed east of the Scandes, but differed in the magnitude and timing of the extremes. At Forfjorddalen, there was no evidence of pine regeneration around 1575-1650. The latter site is likely to have been affected by logging activity in the seventeenth century.
A vegetation and fire history in a subalpine woodland and rain-forest region, Solomons Jewel Lake, Tasmania
Authors: Dodson J. R.
Published: January 2003

Solomons Jewel Lake occurs in an area of subalpine woodland with patches of cool temperate rain forest and the conifer Athrotaxis cupressoides, which is found mainly along stream channels. A pollen record shows that the main vegetation types have not varied throughout the last 4000 years but subtle changes are evident in some elements. Apart from a reduction in Eucalyptus for about 300 years, beginning around 3500 BP, the sclerophyll vegetation has remained relatively unchanged. A small decline in rainforest taxa began around 1700 BP, followed by an expansion of Sphagnum from 1200 BP, then Athrotaxis cupressoides and Cyperaceae from 800-900 BP. These trends probably represent a chain of events associated with a cooling which reduced rain forest and allowed wetland areas to expand. These then provided additional habitat for Athrotaxis cupressoides which expanded because the wetlands provided additional protection from fire.
Postglacial history of subalpine forests, Olympic Peninsula, Washington, USA
Authors: Gavin Daniel G. , Mclachlan Jason S. , Brubaker Linda B. , Young Kyle A.
Published: January 2003

To investigate subalpine vegetation history on the Olympic Peninsula, Washington (USA), two pollen, macrofossil and charcoal records were studied in climatically distinct zones: Martins Lake (1415 m) in the moist Tsuga mertensiana zone and Moose Lake (1508 m) in the drier Abies lasiocarpa zone. The interpretation of fossil pollen assemblages was aided by comparisons with 308 modern assemblages from the Olympic Peninsula and western North America. Both pollen records show a cold/dry period following deglaciation (.10000 radiocarbon years BP) with sparse tundra and little similarity to any modern pollen assemblage. In the early Holocene, when summer temperatures are thought to have been higher than present, high percentages of Alnus sinuata-type pollen at both lakes suggest increased avalanche activity. At Martins Lake warmer summers were not accompanied by forest establishment, possibly because persistent spring snow pack, snow avalanches, and/or edaphic constraints limited tree establishment at this site. The Martins Lake record shows a steplike shift in vegetation to modern Tsuga mertensiana Abies amabilis parkland across the Mazama tephra (6730 BP). In contrast to Martins Lake, Abies lasiocarpa forest quickly established at Moose Lake in the early Holocene, though forests were probably initially open and fires may have been frequent. From 7800 to 5100 BP forests near Moose Lake shifted gradually to cooler and moister species composition, with the addition of Chamaecyparis nootkatensis, Tsuga mertensiana and Pinus, though Abies lasiocarpa remained dominant. Forest cover was probably greatest during this transition, with parklike conditions at Moose Lake beginning at c. 5100 BP. The major differences in the records between the two sites may be due to differences in the local expression of regional climatic change and/or differences in soil development and stabilization.
Dendroclimatic reconstruction of precipitation for sites in the southern Canadian Rockies
Authors: Watson Emma , Luckman Brian H.
Published: January 2003

Seven Douglas fir ( Pseudotsuga menziesii) tree-ring chronologies were developed from sites in Banff and Jasper National Parks, Alberta, and near Cranbrook, British Columbia. The chronologies ranged in length from 191 to 691 years and display a strong precipitation signal. Multiple regression models were developed that calibrate .50% of the variance in the instrumental records and were used to reconstruct annual (pAugust– July or pJuly–June) precipitation for Banff, Jasper and Cranbrook. Comparison of these reconstructions with records from adjacent areas indicates that periods of reduced precipitation occurred over this region in c. ad 1760–1775, the 1790s, the 1840s–1870s, the 1890s and c. 1920–1945. Periods of significantly greater precipi-tation occurred during the 1880s–1920s and in the latter half of the twentieth century. The Banff reconstruction extends back to ad 1430 and also shows major drier intervals c. 1470–1510, the 1570s and 1615–1660. These reconstructions indicate regionally coherent precipitation patterns that fluctuate on decadal timescales and may be linked to changes in atmospheric circulation patterns.
Are Holocene wood-charcoal fragments stratified in alpine and subalpine soils? Evidence from the Alps based on AMS 14C dates
Authors: Carcaillet Christopher
Published: January 2003

The possible stratification of charcoal particles buried in well-drained soil in the subalpine and alpine belts in an inner valley of the northwestern Alps (Savoy, France) is examined. Radiocarbon dating and quantification of charcoal fragments more than 400 μm in diameter were used to analyse the soil-depth distribution of charred wood particles between 1700 and 2600 m a.s.l. in two study areas 10 km apart in the same valley. Above 2100 m a.s.l. in both study areas, charcoal concentrations are low and mainly contained in the upper horizons, and all dated charcoal fragments are older than 2300 cal. yr BP. Below 2100 m, the greatest charcoal concentration is located in the topmost 30 cm of the soil profiles, and the 14C dates yield late-Holocene ages (1600 to 75 cal. yr BP). When profiles have an elevated charcoal concentration in deeper horizons the charcoal dates are mid-Holocene (6360–2770 cal. yr BP). Radiocarbon dates of charcoal fragments do not reveal an age/depth relationship, although charcoal mass concentrations suggest a coarse stratification of charcoal particles in the soils below 2100 m at forested sites. This difference may be due to the charcoal dating on a single fragment which is not representative of the charcoal assemblage containing a few tens to thousands of fragments. The lack of stratification probably results from soil bioturbation by soil fauna, soil reworking by uprooted trees, and freeze-thaw processes. At higher elevation in the alpine belt, charcoal is concentrated in the topmost soil due to a low bioturbation rate. From a pedological point of view, the 14C dating and the quantification of charcoal concentration per soil level provides a time range estimate for soil-particle reworking by anecic earthworms, dung beetles and other biota. This has application in pedogenesis studies to estimate the rapidity of processes of soils dynamics. These data suggest that soils in the Alps have limited potential for palaeoecological studies based on a stratigraphic assumption but have more applications in precise spatial studies.
Holocene stable-isotope stratigraphy at Lough Gur, County Limerick, Western Ireland
Authors: Ahlberg Karin , Almgren Elisabeth , Wright H. E. , Ito Emi
Published: January 2003

After the pronounced fluictuation of 4‰ in δ18O during the Younger Dryas and the 1‰ dip during the Preboreal Oscillation, values for δ18O decreased very steadily from -2.5 to -5.3‰ from 9300 to about 8000 14C yr BP (uncal.). This early-Holocene decrease of almost 3‰ is interpreted as a result of a declinle of almost 6°C in the temperature of precipitation. The previous high temperature of much of the Lateglacial and the Preboreal (12000-9300 yr BP uncal.) may reflect warm summers related to greater insolation and warm winters caused by the influence of the Laurentide ice sheet on atmospheric circulation. After 8000 yr BP a disconformity interrupts the sequence, but after about 5000 yr BP the δ18O and δ13C are irregular because of a low lake level, as shown by the occurrence of littoral shells and woody detritus in the littoral core, and because of anthropogenic factors, as inferred from pollen indicators of forest disturbance and farming found in both the littoral and offshore cores.
1300-year tree-ring width and density series based on living, dead and subfossil black spruce at tree-line in Subarctic Quebec, Canada
Authors: Wang Lily , Payette Serge , Bégin Yves
Published: January 2003

Living, dead and subfossil trees of black spiruce (Picea mariina [Mill.] BSP were used to build a 1300-year chronology based on ring width and wood density. All density sariables (maximcum, minimum, earlywood and latewood densities) among the three types of trees were simlilar, whereas ring width was significantly Higher in liviing trees thani in deacd and subfossil trees. Correlition of the indexed series from liviing and dead trees and from dead and subfossil trees that grew during the samiie periods were higher for Maximum density (r = 0.70, 0.63) and mean latewood density (r = 0.65, 0.66) than for Minimum density (r = 0.16. 0.35 and ring with (r=0.15, 0.49). respctively. Maximum density and mean latewood density were significantly correlated with all temperature variables: mean annual (January-December) and growing season (May September) temperatures, sum of degree days and frost-free days. Accordingly, Maximum and latewood density in tree-rings of spruce stem at tree-linec can be conisidered as a function Of summner-temnperature distributions and different types of trees can be combined for the reconstruction of long-term climatic trends due to theii synchronous variations.
Changes in glacier extent on north Novaya Zemlya in the twentieth century
Authors: Zeeberg Jaapjan , Forman Steven L.
Published: January 2003

Glacier retreat on north Novaya Zemlya for the past century was documented by registering glacier terminus positions from expedition and topographic maps and remotely sensed images. Recession of tidewater calving glaciers on north Novaya Zemlya in the first half of the twentieth century was relatively rapid (>300 m yr-1), consistent with post-‘Little Ice Age’ warming documented by a 122-year instrumental record from Malye Karmakuly. The glaciers completed 75 to 100% of the net twentieth-century retreat by 1952. Between 1964 and 1993 half of the studied glaciers were stable; the remainder retreated modest distances of <2.5 km. This stability coincides with decreasing average temperatures, especially during the winter, which is counter to model prediction. There is a statistically significant covariance of unfiltered winter and summer temperatures from Novaya Zemlya and a smoothed 88-year record of SSTs in the southern Barents Sea (r>0.75). Elevated SST in the Barents Sea appear to reflect increased advection of warm North Atlantic water associated with a positive North Atlantic Oscillation index (NAO). Winter temperatures are periodically correlated with the NAO (r = 0.75 to 0.9) reflecting repeated penetration of Atlantic cyclones into the Arctic. During the twentieth century, an overall positive glacier mass balance trend at Novaya Zemlya is associated with a positive phase of the NAO, elevated southern Barents Sea SST, and a concomitant increase of winter precipitation. Strong NAOs enhance winter precipitation and (3–5 yr delayed) summer temperatures on Novaya Zemlya and have a variable effect on Novaya Zemlya glaciers.
Diatoms as indicators of wetland salinity in the Upper South East of South Australia
Authors: Taffs Kathryn H.
Published: January 2003

Wetland degradation in the Upper South East of South Australia is an urgent management concern. Scant recent environmental data is available for the region and long-term monitoring data is lacking. Usually a palaeoecological analysis is able to reveal environmental change in the medium-to long-term past. However, the region is not conducive to palaeoecological investigation due to a fluctuating upper groundwater aquifer and alkaline soils whiclh have destroyed most microfossils. It was found that the diatom assemblage was preserved in the wetlands of the region for the period of European settlement. Analysis of the diatom assemblage enabled production of an inferred salinity curve. In combination with a small amount of historical information that was available, the salinity trend for the wetlands, for the period of European agricultural activities, was identified. It was found that, while groundwater salinity has been increasing, the wetland areas have experienced a freshening of surface water. This is due to an increase of throughflow of surface water, a result of constructed drainage systems flushing salts from the wetlands. Despite the freshening of wetlands they continue to degrade due to the changed hydrology, an impact of the drainage structures.
Past distribution of Aleppo pine (Pinus halepensis) in the mountains of Israel (Palestine)
Authors: Liphschitz Nili , Biger Gideon
Published: January 2003

It was widely accepted that, in the past, forests of Aleppo pine, Pinus halepensis (‘Jerusalem pine’ in Hebrew), were common in Israel-Palestine and covered vast areas of its mountains. However, an interdisci plinary research project, using botanical, historical and geographical evidence, shows a different picture. The pine is mentioned only once in the Bible, and rarely in other religious sources. Descriptions of pine forests, or even isolated stands, by pilgrims and travellers who visited the Holy Land up to and during the nineteenth century, are rare. Palynological investigations in the area do not reveal any significant amounts of pine pollen except for the twentieth century. Investigations of wood remains from archaeological excavations show that Aleppo pine was rather rare, and constituted only a minute percentage of the wood assemblage. It can therefore be assumed quite safely that the Aleppo pine, which covered in the 1980s about 50% of the planted forests of Israel, was rare in the native arboreal vegetation of Israel in the past.