bluuebunny/crossref_metadata_2025 huggingface dataset:
Two histories of environmental change and human disturbance in eastern lowland Amazonia
Authors: Bush Mark B. , Miller Michael C. , De Oliveira Paulo E. , Colinvaux Paul A.
Published: January 2003

Two long palaeoecological records (pollen, diatoms, 14C, chemistry and charcoal) provide a detailed record of Holocene environmental conditions in the lowlands of the lower Amazon. Changes in the composition of the terra firme forest are evident but a forest cover is maintained throughout. Fluctuations in lake level and changes in seasonality are tracked in both sedimentary sequences. Rising early-Holocene sea levels and the consequent rise of local water tables probably caused the flooding of one of the sites. A stepped increase in precipitation is suggested with increases evident at 8800 yr BP, 7400 BP and between 6100 and 5800 yr BP. Increased storminess is suggested between|7400 yr BP and|6100 yr BP. Human disturbance is manifested in the palaeoecological records at one study site as early as 5500 yr BP ( c. 6500 years ago), and an intensification, or onset, of agriculture is evident at c. 3350 yr BP. The terminating phase of the long record of disturbance is a period of forest regrowth that may correlate to the depopulation of Amazonia following Euro pean contact.
A comparative study of optical properties of NaOH peat extracts: implications for humi®cation studies
Authors: Caseldine Chris J. , Baker Andy , Charman Dan J. , Hendon Dawn
Published: January 2003

Assessment of the degree of decay of peat (humification) in ombrotrophic mires has become a standard technique for palaeoclimatic reconstruction, based on the finding that decay is primarily determined by surface wetness and temperature at the time of peat deposition. Determination of humification is undertaken by colorimetric measurement of an alkali extract of the peat at 540 nm. Humification is proportional to the amount of humic matter dissolved by this extraction process, although few researchers convert results to a quantitative measure of humification expressing results as percentage light transmission through the peat. This paper uses luminescence spectroscopy to assess the chemical composition of these extracts. Luminescence excitation and emission wavelengths suggest that high molecular weight acids (‘humic acids’) are altered by the extraction procedure to form lower molecular weight acids (‘fulvic acids’), amino acids and polysaccharides. Percentage transmission is principally related to luminescence emission wavelength and thus to molecular weight of the compounds present. Luminescence emission shows much more sensitivity to peat composition and demonstrates that different plant species may be affected to different degrees by the NaOH extraction process. The findings broadly support the underlying principle of colorimetric determination of ‘humification’ whereby transmission levels decrease with increasing plant breakdown, but show that it is based on an inadequate understanding of the chemical processes occurring in peat decay and preparation procedures. Luminescence spectroscopy provides a technique for resolving these issues.
Holocene tidal levels and sedimentation rates using a diatom-based palaeoenvironmental reconstruction: the Tees estuary, northeastern England
Authors: Plater A. J. , Horton B. P. , Haworth E. Y. , Appleby P. G. , Zong Y. , Wright M. R. , Rutherford M. M.
Published: January 2003

An established diatom-based tidal level transfer function is used in combination with the present day relationship between sedimentation rate and altitude to reconstruct Holocene tidal sediment accretion for the Tees estuary, northeastern England. The results from five cores reveal two periods of enhanced sedimen tation, the earlier of which (8000–6000 cal. BP) is related to relatively rapid sea-level rise and increasing tidal range. The later phase of increased tidal sedimentation also reflects an enhanced marine influence after c. 3000 cal. BP, but may also be attributed to climate and human-induced changes in terrestrial sediment flux to the coastal zone. Comparison of the reconstructed sediment accretion rates with actual rates calculated from radi ocarbon and luminescence dated sedimentary horizons reveals that this diatom-based approach overestimates sediment accretion by a factor of three. This overestimation is considered to be due to the contemporary sediment flux being an inappropriate analogue for the mid to late Holocene rather than to any significant methodological flaws in the approach.
A palaeoecological attempt to classify fire sensitivity of trees in the southern Alps
Authors: Tinner Willy , Conedera Marco , Gobet Erika , Hubschmid Priska , Wehrli Michael , Ammann Brigitta
Published: January 2003

Using pollen percentages and charcoal influx to reconstruct the Holocene vegetation and fire history, we differentiate six possible responses of plants to fire of medium and high frequency: fire-intolerant, fire damaged, fire-sensitive, fire-indifferent, fire-enhanced and fire-adapted. The fire sensitivity of 17 pollen types, representing 20 woody species in the southern Alps, is validated by comparison with today's ecological studies of plant chronosequences. A surprising coincidence of species reaction to fire of medium frequency is character istic for completely different vegetation types, such as woodlands dominated by Abies alba (7000 years ago) and Castanea sativa (today). The temporal persistence of post-fire behaviour of plant taxa up to thousands of years suggests a generally valid species-related fire sensitivity that may be influenced only in part by changing external conditions. A non-analogous behaviour of woody taxa after fire is documented for high fire frequencies. Divergent behaviour patterns of plant taxa in response to medium and high fire frequencies (e.g., increases and decreases of Alnus glutinosa) also indicate that post-fire plant reactions may change with increasing fire fre quency.
Mire-development pathways and palaeoclimatic records from a full Holocene peat archive at Walton Moss, Cumbria, England
Authors: Hughes P. D. M. , Mauquoy D. , Barber K. E. , Langdon P. G.
Published: January 2003

Plant macrofossil data have been used to identify the successive mire communities occupying both central and marginal locations in the Walton Moss peatland complex, during the last 10 500 years. The reconstructed pathways of mire development indicate that early-Holocene fen and fen-carr communities were succeeded by species indicative of deep mire water tables and oligotrophic conditions. The character of the fen/bog transition (FBT) is compared with similar records of peatland development from Britain and Scandinavia and with independent climate data for the early Holocene. The ‘pseudohochmoor’ of central Europe is suggested as an approximate modern analogue for the dry pioneer oligotrophic mire type and alternative explanations for its presence are explored. The first major increase in ombrotrophic Sphagna occurred at c. 7800 cal. BP. Overlying Sphagnum peats provide a continuous record of climate change, inferred from fluctuations in raised mire surface wetness. The proxy palaeoclimate record, reconstructed using Detrended Correspondence Analysis, registers wet shifts commencing at c. 7800, c. 5300, 4410–3990 (2s range), c. 3500, 3170–2860 (2s range), 2320–2040 (2s range), c. 1750, c. 1450, c. 300 and c. 100 cal. BP. This climate record is compared with a similar one from Bolton Fell Moss and spectral analysis of the time-series gives periodicities of c. 1100 years and c. 600 years between wet shifts.
Fire frequency and forest structure at a dry site between AD 440 and 1110 based on charcoal and pollen records from a laminated lake sediment in eastern Finland
Authors: Pitkänen Aki
Published: January 2003

The fire history of a dry Boreal forest site in eastern Finland before settlement in the area was studied by means of charcoal and pollen analysis of annually laminated lake sediments. The average estimated local fire interval of 70-80 years corresponds to values quoted in a few earlier Finnish studies based on annually laminated lake sediments from more mesic sites. The fire interval is longer than expected from dendrochronological results obtained for dry sites in Fennoscandian forests, suggesting human influence during the periods studied by the dendrochronological method. The high representation of Picea pollen preceding the period of slash-and-burn cultivation at this and some other dry sites suggests a mixed coniferous forest structure at dry forest sites before significant human influence. The charcoal influx reflected estimated climatic shifts, suggesting that the fires increased during the warmer climatic periods. A small test comparing charcoal records on pollen slides with thin sections was included in this study. Large macroscopic charcoal particles were so scarce in the sediment of Lake Laukunlampi that two local fires discernible in the pollen and microscopic charcoal records could not be detected in the thin sections.
Patterns of isostatic land uplift during the Holocene: evidence from mainland Scotland
Authors: Smith David E. , Cullingford Robin A. , Firth Callum R.
Published: January 2003

Preliminary results of a lengthy and detailed investigation into middle- and late-Holocene raised shorelines in mainland Scotland indicate that three shorelines are sufficiently widely distributed to permit an examination of their extent and of the patterns of uplift which they indicate. The shorelines are the Storegga Tsunami Shoreline, reached at c. 7100 14C years BP, at the culmination of the Main Postglacial Transgression; and the Blairdrummond Shoreline, reached after the Main Postglacial Shoreline, at c. 2000–4200 14C years BP, at the time of a tsunami believed to have been caused by the Second Storegga submarine slide; the Main Postglacial Shoreline, reached at c. 5800–6850 14C years BP. The Main Postglacial Shoreline, previously believed to be the highest Holocene raised shoreline in Scotland, is now believed to be overlapped around the periphery of the uplifted area by the later Blairdrummond Shoreline. Isobase models, based upon quadratic trend surface analysis of available comparable height data consisting of altitudes on former estuarine surfaces and related to the local High Water Mark of Ordinary Spring Tides, depict the pattern of uplift for each shoreline. These models are probably more accurate than previous models of land uplift for the period studied, and indicate a consistent and unchanging uplift pattern during the middle and late Holocene.
The distribution of cluster pine (Pinuspinaster) in Spain as derived from palaeoecological data: relationships with phytosociological classification
Authors: Carrió J. S. , Navarro C. , Navarro J. , Munuera M.
Published: January 2003

New pollen-analytical data from the Navarrés peatbog (Valencia, eastern Spain) show a synchronous Late-Quaternary fluctuation of P. pinaster- (cluster pine) and Quercus- (oak) dominated assemblages. During glacial times, P. pinaster survived in refugia together with other trees such as Corylus, Fraxinuv Quercus, and a number of Mediterranean shrubs such as Arbutus, Erica arboreal Olea, Phyllirea, Pistacia terebinthus, Myrtus communis and Viburnum finus. These nuclei of vegetation expanded around c. 30 000-27 000 BP invading areas formerly occupied by pine forests. P. pinaster retreated considerably during the last glacial maximum and the Younger Dryas event, but not as much as Quercus. During c. 10 00-6000 BP, a local pine forest resisted possible oak and P. pinaster invasion. Around 6000 BP, P. pinaster was involved in a post-fire change towards oak-dominated vegetation. This work supports the contention that P. pinaster is native to the Iberian Peninsula and that well-developed P. pinaster forests, particularly if mixed with oaks, are a natural feature of the landscape. The data presented here disagree with the floristic-phytosociological assumption that considers that the forest patches of P. pinaster and other Mediterranean species of pines are incidental and mainly derived from afforestation.
Evidence for Mediaeval soil erosion in the South Hams region of Devon, UK
Authors: Foster I. D.L. , Mighall T. M. , Wotton C. , Owens P. N. , Walling D. E.
Published: January 2003

A major theme of research into the causes of past and present soil erosion has been to determine the relative importance of climate and land-use change in influencing Holocene erosion rates. Previous work suggests that land-use change, especially the conversion of woodlands into agricultural land, is the main factor influencing long-term increases in soil erosion. A study of an extensive minerogenic sediment deposit in a wetland at Slapton Ley in Devon suggests that agricultural intensification occurred before the onset of sedimentation (a silty-clay layer c. 40 cm thick) in the valley-bottom wetland of the Slapton Sewage Works marsh. The base of the silty-clay layer lies at an altitude of between 2.2 and 2.6 m AOD and has been radiocarbon dated at two locations. Conventional radiocarbon ages (± 2 σ) were 910 ± 160 yr and 960 ± 140 yr BP. Successful radiocarbon dating of the upper surface of this minerogenic layer at one location yielded a conventional radiocarbon age of 730 ± 120 yr BP. Within the errors associated with radiocarbon dating, the onset of sedimentation appears to be associated with a period of climatic deterioration towards the end of the Mediaeval Climatic Optimum. While agriculture plays an important role in exposing unprotected soil at certain times of the year, an increase in the magnitude and frequency of wet and severe winters may have led to a substantial increase in the risk of erosion. Contemporary analogues serve to illustrate the complex relationships which may exist between agricultural practices, climate and weather conditions and to explain why erosion is often localized and episodic in nature.
Holocene history of the Baltic Sea as a background for assessing records of human impact in the sediments of the Gotland Basin
Authors: Andrén Elinor , Andrén Thomas , Kunzendorf Helmar
Published: January 2003

Sediment cores from the Gotland Basin were studied for their siliceous microfossil assemblages and organic carbon content to compare recent environmental changes in the Baltic Sea with its natural long-term history. Age models were constructed using 210Pb, 137Cs and corrected and calibrated 14C dates. The transgression that marks the onset of the Ancylus Lake stage is recorded in the sediments as a small increase in organic carbon coinciding with a peak in diatom abundance and increased diatom diversity. A minor occurrence of brackish-freshwater diatoms is recorded in the Ancylus Lake c. 9950–9750 cal. yr BP ( c. 8900–8800 14C yr BP), correlating with the onset of the Initial Litorina Sea in the Bornholm Basin. A high-productivity event is recorded in the end of the Post-Litorina Sea and corresponds to the Mediaeval warm event. An alteration in the diatom assemblage contemporaneous with a decrease in organic carbon, interpreted as representing a deterioration in the climate, correlates with the start of the ‘Little Ice Age’ about 850–700 cal. yr BP. A change dated to ad 1950–1960 is probably an effect of increased nutrient availability in the open Baltic Sea. This effect of eutrophication was probably caused by increased discharge of nutrients deriving from fertilizers, as the responding diatom species partly indicate a cold climate rather than a warm one, as would have been expected if this had been only a response to the warmer climate documented during the last 100 years or so.
Lateglacial and Holocene vegetation and climatic change on Auckland Island, Subantarctic New Zealand
Authors: McGlone Matt S. , Wilmshurst Janet M. , Wiser Susan K.
Published: January 2003

Auckland Island is a small uninhabited Subantarctic island south ( c.51°S) of the New Zealand mainland. It is the southernmost outpost of tall forest in the southwest Pacific. Pollen analysis of two closely adjacent peat cores near tree-line documents climate change and forest dynamics during the Lateglacial and Holocene. After the retreat of glaciers before 15 000 14C yr BP, mountain tundra communities dominated on mineral soils under a cooler ( c.3°C lower) climate than now. By 11 000 14C yr BP, a transition to Chionochloa14C yr BP shrub/grassland became dominant. Forest tree species ( Metrosideros umbellata, Dracophyllum longifolium and Raukaua simplex) spread slowly from 10–000 14C yr BP, but did not form tall forest until 5500–4000 14C yr BP, despite southern ocean temperatures being warmer in the early Holocene. We suggest that warm, cloudy, low-radiation environments inhibited forest growth during the early Holocene in this intensely oceanic setting, through promoting saturated soils and reducing net photosynthesis. It was only in the later Holocene, when increased westerly windflow brought sunnier, although cooler and windier, climates, that forest expansion occurred on sheltered lowland sites. The forest at the study site collapsed to scrub at least twice within the last 2000 years, most likely because of extended periods of saturated soils.
Tropical rain-forest history from the Colombian Pacific area: a 4200-year pollen record from Laguna Jotaordó
Authors: Berrío Juan Carlos , Behling Hermann , Hooghiemstra Henry
Published: January 2003

Pollen analysis of a 5 m long core from Lake Jotaordó, located in northern ‘Chocó biogeographic area’ (5°48[.minute] N, 76°42[.minute] W) along the Pacific coast of Colombia, shows the environmental history of the rain forest during the last 4200 years. Time control has been based on 6 AMS 14C dates ranging from 4230 to 365 14C yr BP. The period of 4230 to 4053 14C yr BP shows sandy deposits and river influence and represents at that time the initial phase of the lake. The composition of the rain forest was different compared to the last 1400 years. Pioneer taxa belonging to Cecropia, Melastomataceae/Combretaceae and Moraceae/Urticaceae dominated the forest. A 30 cm thick organic rich clay from 440 to 410 cm core depth spans a period of 2600 years (from 4050 to 1450 14C yr BP), pointing to a hiatus in the sediment record, possibly caused by riverine erosion of previously deposited sediments. During the last 1400 years rain forest is characterized by Mauritiella, Euterpe/Geonoma, Iriartea, Pachira aquatica and Malpighiaceae. Floral composition of the rain forest is not constant. Abiotic dynamics caused changes in the drainage system. The presence of human settlements during the last 1000 yrs is evidenced by Zea mays and possibly also by the increase of palms.
Response of small New England ponds to historic land use
Authors: Francis Donna R. , Foster David R.
Published: January 2003

This palaeolimnological study addresses whether the timing, magnitude and nature of lake-ecosystem changes closely track changes in land-use intensity and forest cover in the watershed, and the extent to which lakes retuni to pre-disturbance states following the substantial long-term declinie in human activity that is typical for much of the rural eastern United States. Land-use intensity in the watersheds increased rapidly witlh European settleminent and forest clearance, peaked in the mid-nineteenth century when 60-80% of the land was cleared for agriculture, and then declined to the present as natural reforestation resulted in 65-90% forest cover. Land-use intensity in the three watersheds studied ranged from limited logging to extensive clearance for pasturing and to total clearance for pasture and tillage. In contrast to many studies in which human activity continues to increase throughout the settlement period, all three watersheds now support mature, growing forest and are in their most natural condition in the last 200 years. Dated cores from three ponds were analysed for pollen, fossil chironomids, percenit organic matter and sedimentation changes to compare lake and vegetation change among sites. Increased sedimenit-accumulation rates and small increases in productivity occurred in all lakes during the settlement period. Both tremain higher thani pre-settlement levels, indicating that despite lengthy periods without disturbance and a return to completely forested conditions, the systems and sediment records have not returned to pre-disturbance states. In contrast with results from many other palaeolimnological studies, the magnitude of lake response was slight, probably due to the low intensity of nineteenth-century agriculture and the small watershed sizes.
Dental indicators of seasonal hunan presence at the Danish Boreal sites of Holmegaard I, IV and V and Mullerup and the Atlantic sites of Tybrind Vig and Ringkloster
Authors: Carter Richard J.
Published: January 2003

Important new seasonal evidence has been derived from four early Holocene Danish Mesolithic sites based upon tooth-deselopment stages in dentally immature red deer (Cervus elaphus) and roe deer (Capreolus Capreolus). Radiographs of the developing molars aind premolars have been used to provide an indicationl of age at death by comparisons with modem known-age specimens. Knowledge of their age when killed indicates at what time of the year humans were present at the sites. Determining whether a site was occupied seasonally or year-round is critical to subsequent interpretations of human economic and social activity. Based on this new line of enquiry there is strong evidenice for the killing of red aind roe deer during the warmer months of the year at all the Boieal sites. At the Atlantic coastal site of Tybrind Vig red deer were killed in both winteand summer, while at the traditionally winter inland site of Ringkloster esvidence of red deer being killed during the summer months has been found.
Using tephrochronology to date temperate ice: correlation between ice tephras on Livingston Island and eruptive units on Deception Island volcano (South Shetland Islands, Antarctica)
Authors: Pallàs Raimon , Smellie John L. , Casas Josep M. , Calvet Jaume
Published: January 2003

Tephra layers are interstratified in the ice caps of the South Shetland Islands. Although previously poorly investigated, they are potential targets for the application of tephrochronology and, hence, may provide temporal constraints on glaciological models for the region. Several tephra layers crop out in the coastal ice-cliffs and ablation ramps of Livingston Island. Using stratigraphical position, granulometry and bulk sample geochemistry, the tephra layers can be divided into three groups (TPH1, TPH2 and TPH3, from top to base). The source for all of the tephras is unequivocally identified as Deception Island, a large active volcano in Bransfield Strait, situated about 35 km south of Livingston Island. TPH1 (a single layer) is strongly correlated compositionally with tephra erupted in 1970 from centres close to Telefon Bay. This is the first time it has been possible to correlate a distal tephra with a pyroclastic unit in the source volcano in the Antarctic Peninsula region. TPH2 (usually two layers, sometimes only one) was probably erupted from a tuff cone centre within the Crater Lake cluster of vents. From historical accounts, it is deduced that the numerous co-eruptive Crater Lake vents were active prior to 1829 and, from their relatively fresh appearance, an eighteen-century age for the eruptions is possible. TPH3 comprises at least four discrete tephra layers with a much wider compositional range than either TPH1 or TPH2. It may have been erupted during successive months or years. Compositional comparisons of TPH3 with possible source vents on Deception Island are ambiguous, but there is a reasonably good similarity with tephras erupted at Wensleydale Beacon and/or Vapour Col. However, it is also conceivable that the source(s) for TPH3 are no longer preserved on Deception Island. The age of the TPH3 eruptions is unknown but it must be prior to 1829 and is unlikely to be more than a few centuries.
The Holocene history of Pinnus forests in the Spanish Northern Meseta
Authors: Múgica Fáima Franco , Antón Mercedes García , Ruiz Javier Maldonado , Juaristi Carlos Morla , Ollerol Helios Sainz
Published: January 2003

Pollen analysis from a 14.1 m core recoverecd from a vally mire at Espinosa de Cerrato (Palencia, Spain), suggests that Pinus woodland has dominated thils area of the Northern meseta throughout almost the entire Holocene in contrast to many other locations in lbetia where early-Holocene conifer woodland was progressively replaced by deciduous taxa. This unique pattern ofvegetationi developmenit is attributable to a combination of continental climate, edaphic condition of thesas. Mesetas. and perhaps fire. These data suggest that vegetation in this area has been remarkably stable over an extended timescale and that arguments aconcerning Pinus communities not being native in the region are unfounded. Anthropogenic impact can be detected at c. 4500 14C yr BP, affecting evergreen Quercus woodlands, and between c. 3000 and 2000 14C yr BP affecting Pinus woodlands. The pine forests were replaced by plant communities resembling the present-day landscape (shrubs and cereals) from c. 1500 14C yr BP.
Holocene glacier fluctuations of Flatebreen and winter-precipitation changes in the Jostedalsbreen region, western Norvay, based on glaciolacustrine sediment records
Authors: Nesje Atle , Matthews John A. , Dahl Svein Olaf , Berrisford Mark S. , Andersson Carin
Published: January 2003

The history of Holocene glacier variations of Flatebreen, an independent glacier close to the SW part of the Jostedalsbreen ice cap, has been reconstructed from lacustrine sediments in the proglacial lake Jarbuvatnet. The sedimentary succession shows evidence of three maini episodes of Holocene glacier expansion. The first is recorded in the basal part of the core up to 370 cm. According to the age/depth relationship in the sediment core (based on 12 AMS radiocarbon dates), this glacier expansion episode terminated about 10200 cal. yr BP. The second major glacier phase lasted from 8400 to 8100 cal. yr BP, while the third was initiated around 4000 cal. yr BP and has continued up to the present. At 43 cm in the core, the medium silt content increases significantly, accompanied by a minor increase in the sand content. This textural change is interpreted as the first time that the tenninus of Flatebreen extended inlto an] upstream lake at 1083 m a.s.l. The age model suggests that this event took place around 800 cal. yr BP (-AD 1150), as a response to the initial ‘Little Ice Age’ glacier expansion after the ‘Mediaeval Warm Period’. By using a Holocene-inferred summer-temperature curve from central southern Norway in the exponential relationship between annual winter precipitation (snow) and ablation-season temperature at the ELA, periods of higher winter precipitation than the 1961-90 nomial in the Jostedalsbreen region are inferred for 9700-9400, 9200-8300, 8200-6500, 5700-5100, 4700-4600, 4500-4300, 3800-3000, 2100-1800, 1600-1300 and 1200-1000 cal. yr BP, and from 900 cal. yr BP to the present. The intervening periods of lower than normal winter precipitation correlate with periods of enhanced ice-rafting in the North Atlantic.
Late-Holocene climatic change recorded in sediment cores from Ellis Fjord, eastern Antarctica
Authors: McMinn Andrew , Heijnisj Henk , Harle Kate , McOrist Gordon
Published: January 2003

An analysis of diatom assemblages, Total Organic Carbon (TOC), carbon-nitrogen ratio, δ13C, biogenic silica and carboniate in two marine sediment cores from Ellis Fjord, eastern Anitarctica, reveals episodes of climatic change at 3600, 2500. 2000 and 1000 yr BP. Using the diatom data, principal component analysis, the fast-ice index (FI), benthic index (BI) and snow index (SI) (which are derived from the diatom data). a period of reduced temporal sea-ice cover is identified prior to 2500 BP. There was a large increase in sea-ice extent between 2500 and 2000 BP followed by a smaller decline. Tenmporal sea-ice extent after 2000 BP was still significantly greater than prior to 2500 BP. Both cores xvere taken from anoxic basins within the fjJord. It was found that the better preservationi allowed the recognition of taxa such as Clraetocelos vegetative cells, which are inot usually preserved. This enabled the distinction between ice-edge blooms, dominated by Fragilariopsis curta, and open-water blooms dominated by Chaeitoceros. Even though Watts Basin receives a significant summer meltwater input each year, it has not been possible to recognize this signal in the sedimiient core.
Twentieth-century climatic warming in China in the context of the Holocene
Authors: Wang Shaowu , Gong Daoyi , Zhu Jinhong
Published: January 2003

Development of an annual mean temperature series of China for the period of AD 1880-1998 indicated that 1998 was thie wanrest year since 1880. During 1998, temperature was 1.38C higher than the normal (1961-90). Annual mean temperatures of China were found using a weighted average of 10 regional series, whliich covei-ed the xvhole lanid ai-ea of the coutliry fromii Xinjiang and Tibet iI the west to Tailwan i the eCast. Gaps in temperatture obseivations were filled by USing ice-core i' 0 and tie iing data for thice regions in the west. and docuimenitary data for scven regions in the east. Since 1 951. only obser X ational data were usecl. Fiftyyear mean teiimperatture anomnalies were calculated trom the ninth to trwentietlh cernturies. The series do not show any conisistenit warm peiliod in west China durinig the 'Mediaeval Warmii Period (AD 900 to 1300), but temiperatures in east China in At) 850-1099 anid 1200-99 were abouit 0.2C higher than the average for recent years. Centurv-mean ternperatures combininlg west and east re0}ions fi-rom t'he niintlh to twentieth centuries slhowed thlat the twenitieth centLiry was 0.4 C wa5-5.1mid than the imieani of the wshole period. Tempeiatures of the ninith, tenith, clev entli amdI thli-tcentirh cintl aes i xx're oily Slight)y .O.05---0. 0"C) I:mchr thn tl' x avragW. The-retce. tl e twentieth century seems the wamiiest one in China for the last ilmilleniiitiniu or miiore. The last imiillenniumi xvas not the wannest one in comparing with others for the last 10 miilleiinia. Ten regional temperatuLre series from 1O ka BP to the p-esent xweccanalysed wcith the same time r-esolutioni (205ra) awld identical normiial (I 880 1 9791. Gaps in a few ser-ies were filled by the data fromii preViois woirk. Average temperatures were also founid on the hasis of area xveiehting of regional series, showing that the Megatlhemmial was maniifested xwell in China, witli teriiperatures for thie period of 8.0 to 3.0 ka BP fromi 1 5 to 2.)0C liglher tlhani the presenit. Studies of the relationship between temperature and precipitatioti indicated no consistenit correlation. I-loxever, warmdiy dominated oxer wanrm-wet climiiate in niorth Chilna. but the opposite is the case in the very south anid in the west. In east Chinla, the twenitietlh cenltury was probably tIre driest one dur-ing the last millenlnium. Severe droughts occurred itn 20 of the 100 scimmiiiiers of 1900-1999, hut the miieani frequiecy xwas only 10.6 per ceinttiry.
Chronology of the Palmer Deep site, Antarctic Peninsula: a Holocene palaeoenvironmental reference for the circum-Antarctic
Authors: Domack E. , Leventer A. , Dunbar R. , Taylor F. , Brachfeld S. , Sjunneskog C.
Published: January 2003

Palmer Deep sediment cores are used to produce the first high-resolution, continuous late Pleistocene to Holocene time-series from the Antarctic marine system. The sedimentary record is dated using accelerator mass spectrometer radiocarbon methods on acid insoluble organic matter and foraminiferal calcite. Fifty-four radiocarbon analyses are utilized in the dating which provides a calibrated timescale back to 13 ka BP. Reliability of resultant ages on organic matter is assured because duplicates produce a standard deviation from the surface age of less than laboratory error (i.e., ±50 years). In addition, surface organic matter ages at the site are in excellent agreement with living calcite ages at the accepted reservoir age of 1260 years for the Antarctic Peninsula. Spectral analyses of the magnetic susceptibility record against the age model reveal unusually strong periodicity in the 400,–200 and 50-70 year frequency bands, similar to other high-resolution records from the Holocene but, so far, unique for the circum-Antarctic. Here we show that comparison to icecore records of specific climatic events (e.g., the ’Little Ice Age‘, Neoglacial, Hypsithermal, and the Bølling/Allerød to Younger Dryas transition) provides improved focus upon the relative timing of atmosphere/ocean changes between the northern anid southern high latitudes.
Palaeohydrological records derived from testate amoebae analysis from peatlands in northern England: within-site variability, between-site comparability and palaeoclimatic implications
Authors: Hendon D. , Charman D. J. , Kent M.
Published: January 2003

Testate amoebae analysis was undertaken on eight cores from three mires within a restricted geographical area of northern England. This was used to assess, first, the amount of autogenically produced variability in palaeohydrological records from ombrotrophic mires, and, second, to determine whether a palaeoclimatic signal can be derived from testate amoebae analysis from peatlands. Past mean annual water tables were reconstructed by calibrating the testate amoebae record with an existing transfer function. There is a good degree of replicability between the water table reconstructions for the upper peats within each site (especially since cal. AD 600) and the magnitude and timing of most changes are similar. The results show that autogenic factors have a relatively minor control on palaeohydrological records from ombrotrophic peatlands, even for marginal locations where these effects should be greatest. Records from the centres of peatlands are compared to assess the replicability of hydrological changes between the sites to determine which of these changes are attributable to climate. The major fluctuations are well replicated in all central cores, especially for the last 2000 years, suggesting that these shifts are climatically forced and that there is an increasing climatic influence through time, even at the valley mire site. Comparisons with other proxy climatic records suggest that mire surface wetness changes occurred in concert across a broad region of northern England and southern Scotland during at least the last 2000 years.
Holocene development of the Rogovaya River peat plateau, European Russian Arctic
Authors: Oksanen P. O. , Kuhry P. , Alekseeva R. N.
Published: January 2003

In this study, the Holocene development of a peat plateau area in the east-European Russian Arctic is reconstructed based on detailed macrofossil, physico-chemical and radiocarbon analyses from two peat sequences. Basal dates from these two, c. 2 m long, peat profiles are c. 9420 BP and c. 9250 BP. From another six peat sequences gross-stratigraphic descriptions and additional radiocarbon dates are available. Basal dates from two short (<1 m) peat profiles indicate further peatland expansion at c. 3635 BP and c. 1285 BP. The oldest macrofossils of tree birch are dated to c. 9500 BP and those of conifers, presumably spruce, to c. 8000 BP. Tree stands became rare in the study area after c. 2800 BP, but occasionally occur until present. Peatlands formed through terrestrialization of ponds or paludification of forested uplands. Between 9000 and 3100 BP the peatlands were wet rich fens. Beginning from c. 3100 BP there are marked changes in their surface hydrology, connected with climatic cooling and permafrost aggradation. Sphagnum species started to play a dominant role. Permafrost aggradation at the six peat plateau sites is tentatively dated to c. 3100 BP, c. 2200 BP and <600 BP. Nowadays the area is mostly dry peat plateau with interspersed thermokarst lakes. Generally, peat accumulation rates are lower in the upper layers, which consist mostly of Sphagnum peat, than in the lower layers of sedge/brown moss peat. This is most probably due to ceased accumulation or even erosion in the currently widespread dry lichen stage in the peat plateau. Very high accumulation rates are recorded from moist sites with incipient permafrost. This study supports previous multiproxy climate reconstructions in the area according to which temperatures were at least 2-3°C higher during the mid-Holocene compared to present.
Correlation of fluctuations in cladoceran planktonic:littoral ratio between three cores from a small lake in southern Finland: Holocene water-level changes
Authors: Sarmaja-Korjonen K.
Published: January 2003

The main aim of the study was to test the cladoceran planktonic:littoral (P/L) method in Holocene lake-level studies with three cores from a small lake (Iso Lehmälampi, 60°21 'N, 24°36'E), in southern Finland. The cores were analysed for pollen, diatoms and Cladocera, which provided marker horizons, such as appearance level and maxima of species, for correlation with the fluctuations in P/L ratio in the cores. P/L fluctuations appeared to be corresponding and contemporaneous in all three cores and suggested that there were changes of lake level during the Holocene. Water level was high c. 9000-8000 14C yr BP and low c. 7000 BP. The time from c. 4000 BP to modern times is characterized by several short-term fluctuations in water level. The P/L record appeared to be most informative in cores taken outside the shallow littoral area where redeposition may ‘smooth’ the curves. The chydorid species composition was rather uniform in the three cores and showed that analysis from only one core can give a reliable picture of species succession. Although the same P/L fluctuations could be found in all cores, there were large differences in the amplitude of fluctuations in the curves; this suggested that it is not possible to reconstruct the magnitude of lake-level change with this method.
The Holocene record of lake levels of Mansell Pond, central Maine, USA
Authors: Almquist Heather , Dieffenbacher-Krall Ann C. , Flanagan-Brown Riley , Sanger David
Published: January 2003

A palaeohydrological study of Mansell Pond, a small (4 ha), closed-basin lake in central Maine, revealed distinct changes in lake levels throughout the Holocene. We examined the texture, organic content and macrofossils of eight cores and obtained 29 radiocarbon dates on transitions between sedimentary units. The water level fell between about 8000 14 C yr BP and 6000 14 C yr BP, and remained low until after 5000 14 C yr BP. The water level may have begun rising as early as 4750 14 C yr BP, with the most rapid increase occurring from 3225 14 C yr BP to 2780 14 C yr BP. This interpretation varies at some points from an earlier assessment of Mansell Pond's Holocene lake levels that was based on pollen and charcoal evidence from a single core. Records of Holocene lake levels from eastern Canada, the Lake Ontario region and southern New England are inconsistent with each other, suggesting that the influence of dominant air masses has been highly localized in this region
New evidence of Lateglacial cereal cultivation at Abu Hureyra on the Euphrates
Authors: Hillman Gordon , Hedges Robert , Moore Andrew , Colledge Susan , Pettitt Paul
Published: January 2003

Hitherto, the earliest archaeological finds of domestic cereals in southwestern Asia have involved wheats and barleys dating from the beginning of the Holocene, 11–12000 calendar years ago. New evidence from the site of Abu Hureyra suggests that systematic cultivation of cereals in fact started well before the end of the Pleistocene by at least 13000 years ago, and that rye was among the first crops. The evidence also indicates that hunter-gatherers at Abu Hureyra first started cultivating crops in response to a steep decline in wild plants that had served as staple foods for at least the preceding four centuries. The decline in these wild staples is attributable to a sudden, dry, cold, climatic reversal equivalent to the ‘Younger Dryas’ period. At Abu Hureyra, therefore, it appears that the primary trigger for the occupants to start cultivating caloric staples was climate change. It is these beginnings of cultivation in the late Pleistocene that gave rise to the integrated grain-livestock Neolithic farming systems of the early Holocene.
Holocene palaeoecology and formation of the Shoalhaven River deltaic-estuarine plains, southeast Australia
Authors: Umitsu Masatomo , Buman Melanie , Kawase Kumiko , Woodroffe Colin D.
Published: January 2003

The Shoalhaven River is one of the largest rivers on the south coast of New South Wales, and the deltaic-estuarine plains associated with its mouth represent a mature stage of infill of a barrier estuary. The stratigraphy of sediments from more than 60 drillholes from the plains indicates that the area has infilled during the mid-Holocene as a result of input of marine sands associated with a sand barrier on the high-energy coast, and fluvial mud and sands from the Shoalhaven River. Molluscan assemblages indicate that marine influence was initially widespread throughout the eastern and southern parts of the embayment, and that most of the plains infilled under estuarine conditions. Prominent levees across the plains surface are interpreted to be part of a birdsfoot delta distributary complex, and individual floodbasins accreted progressively as they were encapsulated by distributary extension. These former tidal environments mean that there are extensive potential acid sulphate soil conditions beneath the plains. The upper occurrence of Notospisula in drillholes records the cessation of tidal influence, and diatoms from the top of one drillhole record the transition from brackish conditions to freshwater alluvial sedimentation. Radiocarbon dating provides a chronology of mid-Holocene ecological changes on the plains.
Pre-Columbian land-use history in Costa Rica: a 3000-year record of forest clearance, agriculture and fires from Laguna Zoncho
Authors: Clement Rachel M. , Horn Sally P.
Published: January 2003

We analysed pollen and charcoal in a lake-sediment core from Laguna Zoncho, a small mid-elevation lake in southernmost Costa Rica. The record provides evidence of 3000 years of human occupation, forest clearance, agriculture and fires in the area. Laguna Zoncho is located 2 km from the Las Cruces Biological Station, and results are relevant to understanding the likely extent of prehistoric disturbance within the premon tane rain forests of this biological reserve. Pollen grains of Zea mays in the basal sediments of the Zoncho core constitute the oldest botanical evidence of maize cultivation in southern Costa Rica. The presence of maize pollen in almost every sample analysed indicates nearly continuous occupation of the lake basin for 3000 years. Charcoal abundances and percentages of pollen grains and spores of forest and disturbance taxa fluctuate strongly downcore, reflecting variable intensities of past human impact. Forest clearance and burning by indigenous people were most marked between 3240 and 460 cal. yr BP. Sediments deposited subsequently indicate forest regeneration and few, if any, fires. However, indigenous cultivation of maize continued on a small scale until European settlement in the twentieth century.
Comparison of pollen-slide and sieving methods in lacustrine charcoal analyses for local and regional fire history
Authors: Carcaillet Christopher , Bouvier Martine , Fréchette Bianca , Larouche Alayn C. , Richard Pierre J.H.
Published: January 2003

The charcoal content from laminated lake sediments in Québec, Canada, was estimated from pollen slides and by a sieving method. The resulting charcoal series are compared to estimate the suitability of these two methods to provide a local or regional fire history. The replication of five different charcoal series from the sieving method shows that this method is suitable for fire-history reconstruction. In our laminated sediments, 1cm3 is representative of the charcoal content of the sediment. The large charcoal fragments above 15600 mm2are too scarce, however, to provide a significant charcoal series. Comparison of the sieving charcoal series versus the pollen-slide charcoal-series shows that the two series display a roughly similar pattern. The differences between the two series probably result from the accumulation of small particles that have a regional source area and are transported by air over long distances and from high fragmentation rates due to laboratory treatment. Spectral analysis for the last 2000 years shows that the sieving charcoal series have no significant periodic accumulation rate, whereas the spectral analysis of the pollen-slide charcoal series shows a significant period of about 500 years. Because the charcoal particles from the sieving method are larger than those from the pollen-slide method, which are potentially windborne over long distances, our study suggests that the sieving method series is a proxy of local fire history, whereas the pollen-slide method is more suitable for detecting regional trends in fire history.
Mediaeval climatic warming recorded by radiocarbon dated alpine tree-line shift on the Kola Peninsula, Russia
Authors: Hiller A. , Boettger T. , Kremenetski C.
Published: January 2003

Studies of the tree-line history in northern Fennoscandia provide useful evidence about the Holocene environment and the region's climatic history. Here we report on late-Holocene alpine tree-line movement in the Khibiny low mountains on the Kola Peninsula, northwestern Russia. A highly representative collection of subfossil woods above the modern tree-line was obtained and 49 pine samples were radiocarbon dated. Their radiocarbon ages range from c. 1400 to 3000 yr BP with a distinct maximum between c. 800 and 1000 yr BP (about cal. ad 1000 to 1300). We conclude that, especially during the Mediaeval climatic optimum, pine forests grew at least 100–140 m above the modern pine tree-line in the Khibiny mountains.
Tree-ring and summer-temperature response to volcanic aerosol forcing at the northern tree-line, Kola Peninsula, Russia
Authors: Gervais Bruce R. , MacDonald Glen M.
Published: January 2003

Potential linkages between volcanic activity and a 403-year record of Pinus sylvestris L. (Scots pine) growth and summer temperatures estimated from tree-ring widths are evaluated from an Arctic tree-line site on the Kola Peninsula, northwestern Russia. The joint occurrence of volcanic eruptions and severe negative ring-width values is more than four times that expected by chance. A composite average of temperatures indicates that a 0.72°C temperature reduction is typical for the year immediately following volcanic eruptions, while tree growth is reduced for up to two decades. The Greenland Ice Sheet Project 2 (GISP2) volcanic sulphate record shows a small but significant correlation with summer temperatures. Volcanic aerosols originating at low and middle latitudes appear to cause the greatest ring-width reduction and cooling.