bluuebunny/crossref_metadata_2025 huggingface dataset:
Cultural and molecular characterization of photobionts of Peltigera Membranacea
Authors: Mioa V.P.W. , Rabenau A. , Lee A.
Published: September 2002

A molecular study was undertaken to clarify the identity of the photobiont in colourmorphs of the lichen, Peltigera membranacea. Two strains of cyanobacteria, identified as Nosroc sp. by morphology, were cultivated from each of two lichen specimens. Prokaryotic (16S) ribosomal RNA gene fragments were amplified by the polymerase chain reaction (PCR) from DNA extracted from the isolated strains and the lichens, and sequenced directly. Sequences were 98 1% identical between lichen specimens, TDI#AR94 and TDI#AR95, and highly similar to sequences published, or generated in this study from a type culture, for Nostoc. The 16S ribosomal RNA gene sequences (‘ 16S rDNA’) of all four lichen-derived cyanobacteria appeared the same, even though the lichen specimens from which they originated had different sequences. The 16S rDXA from strains 9A and 9B were different from that of specimen TDI#AR94, the thallus from which they were isolated, and instead were the same as that of strains 10A and 10B, and their source, specimen TDI#AR95. When primers selective for the strain 9A sequence were used, however, a small amount of PCR product corresponding to the 16S rDNA of strain 9A was obtained from lichen TDI#AR94. The results confirm that the photobionts of P. membranacea belong to Nostoc, and suggest that genetic differences in the photobiont may be a factor in the occurrence of colourmorphs among cyanolichens.
Fellhanera Viridisorediata, a New Sorediate Species From Sheltered Trees and Shrubs in Western Europe
Authors: Aptroot André , Brand Maarten , Spier Leo
Published: September 2002

Felihanera viridisorediata Aptroot, Brand & Spier, a corticolous sorediate species commonly found sterile, is described from fertile material on Juglans glabra in the Netherlands. It was also found with apothecia on, for example, twigs of Vaccinium myrtillus, Lonicera, and other trees. It seems to be common and rapidly spreading in sheltered habitats in Belgium, Germany and the Netherlands, also occasionally on wood, roofs, granite and brick. It is close to other Felihanera species, especially F. seroexpectata and F. viridis, but it differs in the paler soredia, smaller, 1-septate and constricted ascospores and the presence of roccellic acid.
Practice and Prejudice in Lichen Classification
Authors: Tibell Leif
Published: September 2002

Organismal species exist as historical entities, and essentialistic thinking about ‘ defining ’ species and higher taxa should be avoided. Lichens are biological phenomena that are best understood as processes, and they behave very differently from the model organisms of most systematic theories. Classification and phylogenetic reconstructions are seen as different endeavours, having different aims and languages. A hierarchical classification is supported, and recognition of superspecific taxa is seen as a matter of convenience. Superspecific taxa may be recognized as groups having correlated features, whereas the common recognition of such taxa by a priori cardinal characters should be abandoned. Superspecific taxa having correlated features are distinctive and are likely to be monophyletic. Distinctive and phylogenetically coherent grades may need naming to avoid nomenclatural instability. In classifications, the hypothesized monophyletic status of taxa may be indicated by some convention. Phylogenetic reconstruction by cladistic parsimony analyses includes assumptions that need scrutinizing and modifying to improve the methodology. Analyses should be examined with respect to robustness for changes in the frequently applied equal weighting assumption. For some types of data an a priori weight assignment might be possible, or equal weighting may be justified.
A Critical Appraisal of Modern Generic Concepts in Lichenology
Authors: Nimis Pier Luigi
Published: September 2002

After a brief historical survey, some current trends in the delimitation of lichen genera are discussed. A widespread tendency is that of elevating any supposedly monophyletic group of species to genus rank. As the term ‘ monophyletic ’ has no lower limit, this is likely to result in an explosive inflation of new genera, in a severe loss of the information carried by generic names and in a high degree of nomenclatural disorder. Five criteria are proposed for the acceptance or rejection of new generic segregates: (1) DNA testing for monophyly, (2) phylogenetic analysis, (3) number of characters used, (4) number of species considered, (5) information content of the new splittings. Upon a critical analysis of several recent generic segregations, a more flexible approach to taxonomic ranks is recommended, and particularly, when most of the suggested criteria are not fulfilled, a more frequent use of the subgeneric rank, which does not imply name changes.
Studies in the Lichen Family Pannariaceae VII. on Some Poorly Known Parmeliella-Like Species from the Southern Hemisphere
Authors: Jørgensen Per M.
Published: September 2002

Two Parmeliella-like lichen species are described as new: Santessoniella pulchella, known from warm temperate parts of eastern Australia and northern New Zealand, and Siphulastrum squamosum, a relatively common species on stumps ofNothofagus in southern Chile. Both differ from Parmeliella s. str. in the hemiamyloid, finally red-brown hymenial iodine reaction and the apical structures of the asci, as well as in thallus details (anatomy and chemistry). Parmeliella major Darb. is a synonym of P. thysanota (Sirt.) Zahlbr., which thus proves to be a circumpolar species in the Southern Hemisphere, though not yet discovered in South Africa. A new species, Parmeliella lacerate, is described from the Republic of South Africa, and related to Parmeliella chilensis (Hue) P. M. Jørg., comb. nov.
Hydrogen Sulphide and Epiphytic Lichen Vegetation: a Case Study on Mt. Amiata (Central Italy)
Authors: Tretiach Mauro , Ganis Paola
Published: September 2002

A survey aimed at studying the effects of hydrogen sulphide (H2S) on epiphytic lichen vegetation was carried out at Acquapassante (Mt. Amiata, Central Italy). In 1992, lichen vegetation was surveyed using a sampling grid often units, on 18 chestnut trees along a transect from a chimney emitting H2S to c. 200 m in the direction of the prevailing winds. A Lichen Biodiversity Index (LBI) was calculated as the sum of the frequencies of all species present within the grid. The same survey was repeated five years later. Concentration Analysis was applied to describe the data structure, and Procrustes Analysis was used to verify the congruence between the ordinations of 1992 and 1997. The statistically significant linear and non-linear regressions found between environmental variables (distance of relevés from the chimney, bark pH, lichen biomass of selected foliose and fruticose species, total sulphur content of Evernia prunastri, Hypogymnia physodes, Parmelia sulcata and Ramalina fastigiata) and the position of the relevé points on the ordination axes suggest that species distribution along the transect is related to differences in H2S tolerance. However, some crustose species (Lecanora cf. conizaeoides, L. saligna and Scolkiosporum umbrinum) should be probably excluded from the computation of the LBI for monitoring purposes, as their optimum is in the immediate vicinity of the H2S source.
Environmental Factors Affecting the Distribution of Lichens on Granitic Monuments in the Iberian Peninsula
Authors: Prieto B. , Rivas T. , Silva B.
Published: September 2002

The phytosociology of lichens colonizing granitic churches and dolmens in Galicia (N.W. Spain) and Alentejo (central Portugal) was studied so as to identify (a) a group of species whose frequency on these structures would make them potentially useful as test species for the evaluation of biocides used for conservation, (b) environmental factors likely to control species distribution, and (c) species that may be useful as bioindicators of environmental factors in this kind of construction in the region studied. Chief among the factors correlating with species distribution is the class of structure (church or dolmen), which is attributed to the probable influence of this factor on environmental parameters affected by structural complexity, the presence of non-granitic materials and the influence of man in the immediate surroundings. The bioindicator species most sensitive to this complex of parameters appear to be three species found only on churches (Caloplaca citrina, Sarcogyne davits and Verrucaria macrostoma) and the most widespread of the species found only on dolmens (Lasallia pustulata). Other important factors, probably affecting the influence of class of structure, are pH and the availability of nitrogen and moisture.
Pocsia Mucronata, a new Foliicolous Lichen from Lord Howe Island, Australia
Authors: McCarthy P. M.
Published: September 2002

Pocsia mucronata P. M. McCarthy sp. nov. (incert. sed.) is described from Lord Howe Island, New South Wales, Australia. This foliicolous lichen inhabits leaves of the endemic palm, Howea forsteriana.
Three New Species of Porina (Trichotheliaceae) from Thailand
Authors: McCarthy P. M.
Published: September 2002

Three species of Porina (Trichotheliaceae), P.kansriae P. M. McCarthy, P. siamensis P. M. McCarthy and P. wolseleyae P. M. McCarthy, are described from aquatic and semi-aquatic rocks in montane rainforest in north-eastern Thailand.
Pyrenocollema Montanum, A New Species from Tasmania
Authors: McCarthy P. M. , Kantvilas G.
Published: September 2002

Pyrenocollema montamnn P. M. McCarthy & Kantvilas sp. nov. (Xanihopyreniaceae) is described from moist and aquatic alpine rocks in south-western Tasmania.
Tasmidella, A New Lichen Genus from Tasmania, with A Revised Circumscription of the Family Megalariaceae
Authors: Kantvilas Gintaras , Hafellner Josef , Elix John. A.
Published: September 2002

The new crustose lichen genus Tasmidella, containing the species, T. variabilis sp. nov with two varieties, var. variabilis and var. inactiva var. nov., is described. Tasmidella is most closely related to Megalaria, from which it differs chiefly by having simple ascospores with a layered wall. Relationships with superficially similar genera are discussed. A revised circumscription of the family Megalariaceae is provided to take into account the inclusion of a second genus.
Fenestroconidia Caloplacae, A New Sporodochial Lichenicolous Fungus with Catenate Conidiogenous Cells
Authors: Calatayud Vicent , Etayo Javier
Published: September 2002

The genus Fenestroconidia is described to accommodate the new species Fenestroconidia caloplacae. This lichenicolous fungus produces black sporodochia, has comdiogenous cells arranged in chains, and simple, pale brown conidia with a subhyaline guttule-like zone. It is known only from central Spain (Cuenca province), growing in the apothecia of Caloplaca saxicola s.lat.
Key to the Saxicolous Taxa of Porina
Authors: McCarthy P. M.
Published: September 2002

A key is provided to the 81 saxicolous species and infraspecific taxa of Porina Ach. (Trichotheliaceae). It includes diagnostic characters, broad distributional and some habitat information, as well as references to more complete descriptions.
Lichenopeltella Coppinsii, A New Species on Verrucaria Muralis From the British Isles
Authors: Earland-Bennett P. M. , Hawksworth D. L.
Published: September 2002

Lichenopeltella coppinsii Earland-Bennett & D. Hawksw. is described as a new species growing on Verrucaria muralis in Norfolk. It is compared with other species of the genus occurring on pyrenocarpous lichens in particular, and is close to the species informally called ‘L. hydrophila R. Sant.’, a name that has never been validly published.
Where does Lecanora Demissa (Ascomycota, Lecanorales) Belong?
Authors: Arup Ulf , Grube Martin
Published: September 2002

Lecanora demissa (Körb.) Zahlbr. is a crustose, lobate lichen that produces soredia and conidiomata but no apothecia. Its placement in Lecanora has long been questioned but nothing better has been proposed. We have studied the nuclear rDNA of the ITS regions and the SSU of L. demissa. In an alignment of the ITS regions of several representatives of Lecanora s. lat. it could clearly be shown by a PAUP analysis, using Aspicilia caesiocinerea as outgroup, that L. demissa does not belong to Lecanora. In a PAUP analysis of sequences of the SSU from representatives of the order Lecanorales, using members of Saccharomycetales as outgroup, L. demissa clustered on a well-supported branch with Caloplaca chlorina. In a further analysis of the ITS sequences of L. demissa together with representatives of Caloplaca and Xanthoria using Protoparmelia as outgroup two most parsimonious trees were found. In these trees the L. demissa branch was well within a strongly supported clade with C. cerina, the type species of the genus Caloplaca. The sister taxon to L. demissa in this analysis was C. variabilis. Chemical data and characters of the conidiomata support the affinity with Caloplaca and the new combination C. demissa (Körb.) Arup & Grube is therefore proposed. A lectotype for Imbricaria demissa has been designated. The phylogenetic analysis of several representatives of the genera Caloplaca and Xanthoria suggests that these genera are not monophyletic as presently circumscribed. Two large, monophyletic groups of species could be recognized, one with Xanthoria species mixed with lobate and crustose members of Caloplaca, and one with mainly crustose Caloplaca, including both species with orange or black apothecia.
A New Bryophilous Porina from Tasmania, and Notes on the Diversity, Ecological Groups and Biogeographical Affinities of Tasmanian Trichotheliaceae
Authors: McCarthy P. M. , Kantvilas G.
Published: September 2002

Porina bryophila P. M. McCarthy & Kantvilas is described from living and moribund epiphytic bryophytes in Tasmanian rainforest. The diversity, ecological groups and biogeographical affinities of Tasmanian Trichotheliaceae, currently comprising 25 taxa, are discussed.
Evaluation of bio-indication methods using epiphytes by correlating with SO2-Pollution Parameters
Authors: Geebelen Wouter , Hoffmann Maurice
Published: September 2002

In order to evaluate the relative usefulness of the numerous bio-indication methods that use epiphytes as indicators for air pollution, a range of these different methods was applied within the same region (Flanders, Northern Belgium). The study area shows important air pollution gradients and little climatic differentiation. Ninety-one IAP indices were calculated with data collected in the immediate vicinity of SO⊂2 measuring stations on one randomly chosen tree, on ten neighbouring trees and in a sampling grid placed on the tree carrying the largest number of epiphytes. A large majority of indices showed a significant Spearman rank order correlation with mean SO⊂2 winter values over the 5 years 1990-94. Indices based on a selection of 17 lichens gave better results than those based on all lichens. The latter indices showed higher correlation than those using all epiphytes (including bryophytes). Indices using a quantitative estimate of cover or abundance or a combination of these did not result in a higher correlation. Sampling ten trees gave slightly higher correlation than the grid method or sampling of one tree. Taking into account supplementary evaluation criteria (time investment and degree of lichenological knowledge required), sampling of 17 bio-indicator species using a sampling grid is recommended within the study area. Monitoring the presence of all corticolous lichens within a sampling grid is recommended in general.
Dissolution of Weddellite, Calcium Oxalate Dihydrate, in Pyxine Subcinerea
Authors: Modenesi P. , Bombardi V. , Giordani P. , Brunialti G. , Corallo A.
Published: September 2002

On the thalline lobes of Pyxine subdnerea there are delimited patches of pruina consisting of bipyramidal prisms, bipyramids and druses of weddellite, i.e. calcium oxalate dehydrate (COD), as revealed by X-ray analysis and SEM observations. The disappearance of the crystals from older thalline areas is preceded by an increase in the frequency of corrosion figures, in the form of etch square pits, and a decrease in the number of crystals occurring on the thalline surface. These features follow a dissolution gradient from the lobe apex towards the proximal edges of the patches. The corrosion figures are linked to the thermodynamic metastability of COD. Partial dissolution of the crystals, performed in water and in EDTA, has confirmed this latter assumption. It is thought that the disappearance of pruina, which interferes with the transmission of light to the algal layer, may allow the formation of soredia in mature thalline portions.
Phytosociology of Terricolous Lichen Vegetation in the Cairngorm Mountains, Scotland
Authors: Fryday Alan M.
Published: September 2002

The results of an investigation into the lichen vegetation associated with vascular plant communities in the Scottish Highlands are presented. Most lichen species rarely occur in homogeneous stands of vascular plant vegetation, either occurring around the edges of recognized National Vegetation Classification (NVC) communities or in small-scale mosaics with them. However, some lichen species have a high fidelity to the more open NVC communities. The problems associated with applying NVC survey techniques to lichen assemblages are described and discussed.
Mapping and analysis of distribution patterns of lichens on rural medieval churches in north-eastern Germany
Authors: Weber Bettina , Büdel Burkhard
Published: September 2002

Lichen communities were examined on 62 churches in Mecklenburg–Vorpommern, Germany. Ninety-six lichen species and subspecies, and three species of lichenicolous fungi identified. Tylothallia biformigera and Lecanora campestris subsp. dolomitica are reported as new Germany, and another 20 species are considered as threatened. This implies that the stone walls churches represent an extremely important habitat in Mecklenburg–Vorpommern, where natural outcrops are rare. The distribution of lichen species was analyzed quantitatively in relation to several habitat factors. Aspect, substratum and inclination were found to be important factors for 35, 34 31 species, respectively. The height of the relevé was a significant factor for many species. Twenty-three species, which are described in the literature with oceanic to suboceanic distributions, occur significantly more frequently near the coast. The ways in which microclimate affects each these habitat factors and contributes to the presence or absence of a species or group of species discussed. Some species have narrow and specific habitat demands, whereas others thrive under wide range of environmental conditions. The advantages of a strictly schematic approach with detailed statistical analysis are discussed.
The vertical gradient of bark pH of twigs and macrolichens in a Picea abies canopy not affected by acid rain
Authors: Kermit Thale , Gauslaa Yngvar
Published: September 2002

The pH of 192 thin, even-aged twigs from 4 height levels of 12 randomly selected trees within a boreal Picea abies canopy naturally exposed to rainfall with a high pH (>5·2) was measured. The largest variation in bark pH was due to the height above the ground. However, a highly significant horizontal variation between trees was also found, apparently due to small-scale soil variations. The biomass of alectorioid lichens increased with increasing height above die ground to at least 12 m, a height interval with fairly constant pH values. The uppermost twigs had an unusually high pH and an abnormal species composition for P. abies, with dominance of the foliose Melanelia exasperatula. The canopy hosted several cyanobacterial lichens, but these were scattered and had low biomass, restricted to lower branches of the trees with the highest bark pH.
Molecular and morphological studies on the subantarctic genus Orceolina (Agyriaceae)
Authors: Poulsen R.S. , Schmitt I. , Søchting U. , Lumbsch H. T.
Published: September 2002

The subantarctic genus Orceolina is revised and two species are accepted, i.e. Orceolina antarctica Mull. Arg. R. S. Poulsen Søchting comb. nov. and Orceolina kerguelensis (Tuck.) Hertel. Descriptions of the species are provided. In addition the phylogeny of the genus Orceolina and allied taxa was investigated using nucleotide sequences of the LSU rRNA gene. Sequences from these regions of nine agyrialean fungi were aligned to those of four representatives of Pertusariales used as outgroup. The alignment was analysed cladistically using maximum parsimony. The two Orceolina clustered together within the Agyriaceae. The placement in the family is supported by high bootstrap values and the Kishino-Hasegawa test.
Chiodecton epiphyllum is a lichenicolous fungus on Coenogonium flavicans and belongs in the genus Plectocarpon (Arthoniales: Roccellaceae)
Authors: Cáceres Marcela E. S. , Diederich Paul , Lücking Robert , Sérusiaux Emmanuël
Published: September 2002

The biological status of Chiodecton epiphyllum (Arthoniales: Roccellaceae), described as a foliicolous lichen from Papua New Guinea, is reassessed, based on additional material from Brazil, Costa Rica, and Papua New Guinea. The species is a lichenicolous fungus growing on the foliicolous lichen Coenogonium flavicans (Gyalectales: Gyalectaceae). Furthermore, its ascomatal anatomy and lichenicolous growth habit suggest placement in the related genus Plectocarpon, instead of Chiodecton. We therefore propose the new combination Plectocarpon epiphyllum [Bas.: Chiodecton epiphyllum]. The species is further lectotypified on its ascomata since parts of the original description which denote vegetative characteristics refer to the sterile thallus of the host lichen.
Buellia Triseptata in the Iberian Peninsula
Authors: Giralt Mireia , Nordin Anders
Published: September 2002

Iberian records of Buellia triseptata A. Nordin are presented. This corticolous and lignicolous species was recently described from North America. A description based on the Iberian material is given, together with notes on ecology and distribution. Specimens belonging to B. triseptata were previously reported as B. disciformis, B. lauricassiae, B. pharcidia and B. triphragmia. The main distinguishing features between these taxa and B. triseptata are pointed out, and background to the misapplied names is given. Illustrations of the ascospores of B. triseptata and B. lauricassiae are presented. A distribution map of B. triseptata in the Iberian Peninsula is also provided.
Stratigraphic Evidence of a Pre-Wisconsinan Interglaciation in the Adirondack Mountains, New York
Authors: Muller Ernest H. , Sirkin Les , Craft Jesse L.
Published: September 2002

Multiple tills separated by interbedded lake sediments were temporarily exposed during open-pit mining at Sanford Hill, near Newcomb, in the central Adirondack Mountains of northeastern New York. Radiocarbon ages of wood fragments from brown clay between two tills at that site indicate an age older than 55,000 yr B.P. A pollen profile in the brown pond clay (Tahawus clay) records a transition from initial domination by pine, spruce, and birch to an oak pollen zone. The upward disappearance of spruce and decrease of pine and birch are accompanied by diversification and increase in hardwood pollen. This assemblage includes several warm-climate hardwood species that are not represented in the postglacial flora of the region, suggesting that the biota existed during an interglacial or interstadial interval that was warmer and/or longer than postglacial time. Accordingly, the Tahawus clay is tentatively assigned to the Sangamon interglaciation, and probably to marine oxygen isotope substage 5e. Truncation of the Tahawus clay by glacial erosion may account for the absence of a Sangamon paleosol.
Stable Isotopic Evidence for Latest Pleistocene and Holocene Climatic Change in North-Central Texas
Authors: Humphrey John D. , Ferring C. Reid
Published: September 2002

A paleoclimatic record for a southern Great Plains locality (the Aubrey Clovis site in north-central Texas) has been established using stable carbon and oxygen isotopes. Detailed composite stratigraphic sections, constrained by14C ages, place the age of these deposits between 14,200 and 1600 yr B.P. Calcium carbonate samples of lacustrine and pedogenic origin were analyzed. Oxygen isotopic compositions of most of thesein situcarbonates reflect equilibrium precipitation from local meteoric waters. Oxygen isotope values reflect changes in the composition of meteoric waters tied to changes in the isotopic composition of moisture derived from the Gulf of Mexico. Oxygen isotopic variability at the Aubrey site is coincident with marine isotopic records from the gulf that vary due to changes in Laurentide ice sheet volume and meltwater influx. The stable carbon isotopic record, reflecting changing biomass through time, corroborates humid versus arid interpretations based on sedimentology and rates of alluviation. A middle Holocene arid period was in contrast to moist early and late Holocene climate, affirming interpretations of other workers studying southern Great Plains Holocene climate history.
Remanence Characteristics of Different Magnetic Grain Size Categories at Xifeng, Central Chinese Loess Plateau
Authors: Liu Xiuming , Rolph Tim , Bloemendal Jan , Shaw John , Liu Tungsheng
Published: September 2002

Utilizing the thermal unblocking of low-temperature remanent magnetization in superparamagnetic (SP) ferrimagnets and the low-temperature demagnetization of multidomain (MD) magnetite remanences, the relative proportions of SP, MD, and singledomain (SD and SD-like) ferrimagnets are estimated in the topmost part of a loess section at Xifeng, China, which covers about the past 130,000 yr. SP ferrimagnets are commonly regarded as pedogenic (authigenic) products while the MD component is believed to have a detrital origin. These measurements, therefore, provide new data which improve our understanding of the characteristics and distribution of the different magnetic grain-size fractions present in loess and soils. In particular, our measurements indicate a larger MD fraction in soil than in loess, a result which indicates that although enhancement of the SP ferrimagnet fraction dominates the increased low-field magnetic susceptibility of paleosols, an enhancement of the MD fraction, probably through leaching, also plays an important role during pedogenesis.
Variation in Radiocarbon Ages of Soil Organic Matter Fractions from Late Quaternary Buried Soils
Authors: Martin Charles W. , Johnson William C.
Published: September 2002

Radiocarbon dating of three organic matter fractions (total, humic acid, and residue) isolated from late Quaternary buried soils of the central Great Plains reveals that there often are considerable differences among, but no consistent order to, the ages of fractions. For late Holocene soils, the residue fraction or the total fraction generally produces the oldest age; for late Pleistocene soils, however, no fraction was consistently the oldest. The absence of a consistent sequence of fraction ages is attributed to postburial contamination of soils. When bulk samples from the same soil were split and sent to two laboratories, different radiocarbon ages were usually obtained. The variability in radiocarbon ages of soil organic matter confirms that caution should be taken when using radiocarbon ages obtained from different laboratories to make regional stratigraphic correlations.
A Dendroclimatic Reconstruction of Annual Precipitation on the Western Canadian Prairies since A.D. 1505 from Pinus flexilis James
Authors: Case Roslyn A. , MacDonald Glen M.
Published: September 2002

Tree-ring chronologies from living and sub-fossil Pinus flexilis James (limber pine) trees extend back more than 500 yr on the western edge of the Great Plains in Alberta. Living trees were found to be as old as 526 yr. Tree-ring growth in Pinus flexilis is most sensitive to annual precipitation over the annualization period August to July. The longevity of the trees coupled with their sensitivity to variations in annual precipitation make them an important resource for constructing annually resolved multicentury records of paleohydrology on the northwestern Great Plains. A 487-yr reconstruction of annual precipitation in southwestern Alberta was produced from the tree-ring series. This is the longest dendroclimatological reconstruction of precipitation available from the northern plains. The reconstruction has some similarity to reconstructions from the western Great Plains of the United States. However, there are also many divergences in the timing of droughts. Some of this divergence may reflect the importance of orographic uplift in producing precipitation along the eastern flanks of the Rocky Mountains. Our reconstruction shows that the frequency of droughts in Alberta during the period of instrumental records, about the last 100 yr, has not been appreciably different from conditions of the preceding four centuries. In addition, the most severe drought of this century, which led to widespread farm abandonment between 1918 and 1922, was not the most severe drought in the past 487 yr.
Enhanced Age Resolution of the Marine Quaternary Record in the Arctic Using Aspartic Acid Racemization Dating of Bivalve Shells
Authors: Goodfriend Glenn A. , Brigham-Grette Julie , Miller Gifford H.
Published: September 2002

Aspartic acid (Asp) racemization occurs at a significantly higher rate than isoleucine epimerization and consequently provides better temporal resolution of Arctic marine deposits (from Alaska, Spitsbergen, and Baffin Island). Heating experiments (at 100°C) on the bivalves Mya and Hiatella show the Asp racemization rate decreases with increasing D/L values, as is typical for biogenic carbonates. Based on these experimental racemization rates and rates determined from racemization of samples radiocarbon dated to ca. 10,000–12,000 yr B.P., activation energies for Mya and Hiatella are estimated to be 30.6 and 30.0 kcal/mol, respectively, for Asp racemization, and 29.0 and 29.5 for isoleucine epimerization. Analysis of a time series of Plio–Pleistocene Hiatella from the north coast of Alaska shows that last-interglacial mollusks can be readily distinguished from modern samples by Asp but not by isoleucine. D/L Asp values indicate a younger age for the Fishcreekian transgression than does isoleucine epimerization. For Spitsbergen, D/L Asp shows a slight age difference (ca. 12,000 yr) between two units of the “episode B” interstadial and suggests that the age of these units may be closer to 65,000 than to 80,000 yr B.P., two possible ages suggested by other evidence. The age of the Loks Land Interstadial on Baffin Island is likely to be greater than that indicated by radiocarbon ages. Within deposits from each region, D/L Asp values are less variable among individual shells than isoleucine epimerization values. This may indicate better reliability of Asp for geochronology.
Characterization of the Soil Hydromorphic Conditions in a Paludified Dunefield during the Mid-Holocene Hemlock Decline near Québec City, Québec
Authors: Bhiry Najat , Filion Louise
Published: September 2002

The mid-Holocene eastern hemlock [Tsuga canadensis L. (Carr.)] decline has been recently attributed to the activity of insect defoliators. N. Bihiry and L. Filion, Quaternary Research 45,312–320 (1996). In this study, soil hydromorphic conditions were investigated for the period 6800–3200 yr B.P. using micromorphological data from a peat section from a swale in a paludified dunefield in southern Québec. After a short period of plant colonization in shallow pools between 6800 and 6400 yr B.P., mesic conditions predominated in the interdune before the decline (6400–4900 yr B.P.), as evidenced by strong bioturbation and abundance of excrements from the soil fauna. During the decline, a shift from mesic to wet conditions occurred (4900–4100 yr B.P.), although xeric to mesic conditions persisted on dune ridges until at least 4200 yr B.P. Wetness culminated when beaver occupied the site (4100–3750 yr B.P.). Hemlock needles with chewing damage typical of hemlock looper (Lambdina fiscellaria) feeding were identified at levels dated 4900, 4600, and 4200 yr B.P., respectively, implying that the hemlock decline was associated with at least three defoliation events. The ca. 400-yr interval between these events likely represents the time required for this late-sucessional tree species to recover.
Implications of Late Pleistocene Glaciation of the Tibetan Plateau for Present-Day Uplift Rates and Gravity Anomalies
Authors: Kaufmann Georg , Lambeck Kurt
Published: September 2002

Minimal and maximal models of Late Pleistocene Glaciation on the Tibetan Plateau are considered. The large ice sheet models indicate that disintegration of the ice sheet could have contributed up to 7 mm/yr of present vertical uplift and 2 mm/yr of horizontal extension. The former value can account for more than 50% of the observed uplift in central Tibet. The peak free-air gravity anomaly arising from the deglaciation would be around −5.4 mGal. In contrast, the smaller ice sheet models do not contribute significantly to the signals of present uplift and gravity anomalies. Modern geodetic measurements therefore have the potential to constrain the Late Pleistocene glaciation of the Tibetan Plateau. Assuming a large ice sheet over the Tibetan Plateau, the disintegration can contribute up to 6 m of eustatic sea-level rise.
Late Holocene Lake Sedimentology and Climate Change in Southern Alberta, Canada
Authors: Campbell Celina
Published: September 2002

Climatic changes in southern Alberta, Canada, for the past 4000 yr are reflected in a high-resolution record of lake sediment grain size. The proposed mechanism for this response is that outflow discharge removes fine-grained sediments, but increasingly fine sediments are retained and deposited as streamflow declines. At the same time, coarse sediments are brought in by high discharge entering the lake. The net effect of these two processes is to leave coarse, clay-deficient sediments during times of high streamflow and clay-rich sediments during times of low flow. The grain-size record from Pine Lake reflects historic climate fluctuations, as well as prehistoric fluctuations including the Little Ice Age and the Medieval Warm Period. Grain size at this site provides a simple, economical, and nonbiologically mediated paleoclimate proxy.
Multiple Sources for Sea-Rafted Loisels Pumice, New Zealand
Authors: Shane Phil , Froggatt Paul , Smith Ian , Gregory Murray
Published: September 2002

Sea-rafted Loisels Pumice is one of the few stratigraphic markers used to correlate late Holocene coastal deposits in New Zealand. Along with underlying sea-rafted products of the local Taupo eruption of ca. 1800 yr B.P., these events have been used to bracket the first arrival of humans at New Zealand. Loisels Pumice is dacitic to rhyolitic (SiO2 63–78 wt%) in composition, but individual clasts are homogeneous (SiO2 range ± 1 wt%). Characteristics include very low K2O (0.5–1.75 wt%) and Rb (<25 ppm) and a mineralogy dominated by calcic and mafic xenocrysts. Similar features are shared by pumices of the Tonga–Kermadec arc, suggesting a common tholeiitic oceanic source. Interclast diversity of Loisels Pumice suggests that it is the product of several eruptive events from different volcanoes. The differences in glass and mineral compositions found at various sites can be explained if the deposits are from different events. A multisource origin can also partially explain the discrepancy in reported 14C ages (ca. 1500–600 yr B.P.) from different localities. Therefore, the value of Loisels Pumice as a stratigraphic marker is questionable, and it does not constrain the arrival of humans. The predominant westward drift of historic Tonga–Kermadec arc pumices and prevailing ocean currents suggest a long anticlockwise semicircular transport route into the Tasman Sea before sea-rafted pumice arrival in New Zealand. The diversity of the pumices indicates that silicic eruptions frequently occur from the predominantly basic oceanic volcanoes.
Holocene Glacier Advances in the Headwaters of Sredniaya Avacha, Kamchatka, Russia
Authors: Savoskul Oxana S.
Published: September 2002

Holocene glacial deposits in Sredniya Avacha headwaters are subdivided into three age groups (events A, B, and C) based upon geomorphic features, tephrochronology, and lichenometry. Tephras of Opala volcano (1400–1500 yr B.P.), Ksudach volcano (1700–1800 and 6000 yr B.P.), and Zavaritskiy volcano (2800 yr B.P.) are used as stratigraphic markers. Rhizocarpon geographicum (L.) DC and Rhizocarpon section Alpicola growth curves are established using tephrochronologically dated and historical surfaces. The age of event A (pre-Hypsitermal?) moraines is constrained by an age of 6000 yr B.P. for overlying Ksudach-2 tephra and an age of 7200 (?) lichenometric (L) yr B.P. Event B (Neoglaciation) had a multiple nature, with the most prominent advances at 4300–3500, 3300–2800, 2600–2100, 1800–1400, and 1300–1100 (L) yr B.P.; the culmination occurred before 2800 yr B.P., as suggested by a date for Zavaritskiy volcano tephra found on the glacial and outwash deposits. Less-extensive glacier advances of event C (“Little Ice Age”), occurred at 800–600, 500–200, 180–110, and 90–40 (L) yr B.P. The ELA depression was 200–250, 100–150, 30–70 m during the culmination of events A, B, and C, respectively.
A 50,000-yr Pollen Record from Chile of South American Millennial-Scale Climate Instability during the Last Glaciation
Authors: Heusser Linda , Heusser Calvin , Kleczkowski Adam , Crowhurst Simon
Published: September 2002

High-resolution (∼≤100 yr sampling interval) Chilean pollen data between ∼10,000 and 60,000 cal yr B.P. exhibit systematic fluctuations in Subantarctic Parkland development. These variations are dominated by a 30,000–40,000-yr cycle similar to that in the Northern Hemisphere GISP2 δ18O data and other climatic records. Both Chilean and GISP2 data show oscillations in the 5000–12,000 and 1000–3000-yr period bands. The coherence is, however, generally low, and distribution of power spectra differs, with the dynamics of the pollen assemblage dominated by a combination of 12,000- and 5000-yr cycles. We suggest a preferential nonlinear response of Chilean vegetation to climatic forcing and interhemispheric differences as possible mechanisms underlying the resemblances and dissimilarities between both records.
Amino Acids and Stable Carbon Isotope Distributions in Taihu Lake, China, Over the Last 15,000 Years, and Their Paleoecological Implications
Authors: Jinquan Wang , Jinling Liu
Published: September 2002

Amino acid, organic nitrogen, and stable carbon isotope (13C/12C) profiles through a core from East Taihu Lake are interpreted in terms of paleoecology and paleoclimate over the last ca. 15,000 yr. Lower amino acid contents and higher δ13C values at the base of the core represent a cool and arid climate, and coincide with low organic productivity. A marked increase in total amino acids and organic nitrogen, with a decrease in δ13C values from 193 to 90 cm (ca. 6500–6000 yr B.P.), indicates a warmer and moist climate, and greater organic productivity. Amino acids then decrease in abundance, while δ13C values increase progressively, beginning at 73 cm (ca. 6000 yr B.P.), reflecting cooling and lower organic productivity. The average δ13C values from a core from West Taihu Lake are evidently higher than values from East Taihu Lake. The latter may reflect a stream environment, whereas the high δ13C values from West Taihu Lake likely reflect autotrophic carbon sources and a lacustrine environment since 11,000 yr B.P.
A Late Holocene Paleoecological Record from Torrey Pines State Reserve, California
Authors: Cole Kenneth L. , Wahl Eugene
Published: September 2002

Paleoenvironments of the Torrey Pines State Reserve were reconstructed from a 3600-yr core from Los Peñasquitos Lagoon using fossil pollen, spores, charcoal, chemical stratigraphy, particle size, and magnetic susceptibility. Late Holocene sediments were radiocarbon dated, while the historical sediments were dated using sediment chemistry, fossil pollen, and historical records. At 3600 yr B.P., the estuary was a brackish-water lagoon. By 2800 yr B.P., Poaceae (grass) pollen increased to high levels, suggesting that the rising level of the core site led to its colonization bySpartina foliosa(cord-grass), the lowest-elevation plant type within regional estuaries. An increase in pollen and spores of moisture-dependent species suggests a climate with more available moisture after 2600 yr B.P. This change is similar to that found 280 km to the north at 3250 yr B.P., implying that regional climate changes were time-transgressive from north to south. Increased postsettlement sediment input resulted from nineteenth-century land disturbances caused by grazing and fire. Sedimentation rates increased further in the twentieth century due to closure of the estuarine mouth. The endemicPinus torreyana(Torrey pine) was present at the site throughout this 3600-yr interval but was less numerous prior to 2100 yr B.P. This history may have contributed to the low genetic diversity of this species.
Use of Rubidium to Date Loess and Paleosols of the Louchan Sequence, Central China
Authors: Chen Jun , Ji Junfeng , Chen Yang , An Zhisheng , Dearing John A. , Wang Yongjin
Published: September 2002

Rb concentrations, analyzed at 20-cm intervals from the Luochuan sequence of loess and paleosols, are sensitive to the loess–paleosol alternation controlled by monsoon climate. Because it is geochemically immobile, Rb can be well preserved in the loess–paleosol sequence after deposition, and its concentration depends mainly on properties of the winter monsoon-blown dust and on intensity of the summer monsoon-induced pedogenesis. A curvilinear relation has been developed between the measured Rb-concentration and the apparent sedimentation rate for the last glacial–interglacial cycle. This relation provides a time scale that corresponds well with the presently accepted ages for paleomagnetic reversals of Brunhes/Matuyama and Jaramillo events. With allowance for reduced Rb concentrations caused by early Pleistocene climate, the Rb-based time scale is also consistent with the boundary ages of other major paleomagnetic reversals of the past 2.58 myr.
Variability of East Asian Winter Monsoon in Quaternary Climatic Extremes in North China
Authors: Lu Huayu , van Huissteden Ko , Zhou Jie , Vandenberghe Jef , Liu Xiaodong , An Zhisheng
Published: September 2002

In order to examine high-frequency variations of East Asian winter monsoon in Quaternary climatic extremes, two typical loess–paleosol sequences in the Chinese Loess Plateau were investigated. Sandy layers in the loess deposits, the “Upper sand” and “Lower sand” (layers L9 and L15, respectively), which represent a high-resolution record of paleomonsoon changes, have been sampled at intervals of 5–6 cm from sections at Luochuan and Xifeng. The grain size and magnetic susceptibility was measured for all samples. The grain-size results (a proxy of winter monsoon strength) indicate that the winter monsoon strength fluctuated on a millennial timescale during cold climatic extremes, with climatic events of a few hundred to a few thousand years. However, the winter monsoon was relatively stable during warm periods. The magnetic susceptibility signal (a proxy of summer monsoon intensity) is practically constant over the same period. This is tentatively explained by the assumption that the summer monsoon intensity was too low to be recorded in the magnetic susceptibility signal. The intensified winter monsoon events show periodicities in a range of 1000 to 2770 yr, with a dominant cycle of approximately 1450 yr. The detection of this oscillation in older glacial stages strongly suggests that it may be a pervasive cycle of the cold climatic phases of the Quaternary. Millennial-scale variations of the winter monsoon may be caused by instability of the westerly jet, which is determined by temperature differences between the polar and the equatorial regions.
Luminescence Dating of Sediments from the Luthern Valley, Central Switzerland, and Implications for the Chronology of the Last Glacial Cycle
Authors: Preusser Frank , Müller Benjamin U. , Schlüchter Christian
Published: September 2002

The advancing glaciers of the last glacial maximum either eroded or deeply buried older sediments in the Swiss Alpine Foreland. However, part of the Swiss Plateau was not covered by ice and is therefore an excellent area for investigating climate and environmental change during the Upper Pleistocene. Repeated fluvial sequences can be studied in several pits along the Luthern Valley. The chronological framework is based on lithostratigraphy, pollen analysis, U/Th dating, and recently, heavy mineral analysis and luminescence dating. The oldest unit, the Untere Zeller Schotter braided river deposit, represents cold climate conditions and presumably a glaciation prior to the Eemian Interglaciation. The last interglacial period and the very beginning of the last glacial cycle is represented by the Mittlere Zeller Schotter, sediments of a meandering fluvial system. Younger braided river sediments, the Obere Zeller Schotter, seem to correlate with the cold climate of oxygen isotope stage (OIS) 4. Weathering of the top of the Obere Zeller Schotter is likely to represent the OIS 3. The advancing Reuss glacier caused erosion of the recent Luthern Valley, cutting into older sediments, with local loess accumulation during the last glacial maximum as indicated by cover sediments on top of the fluvial sequence.
Late Quaternary Stratigraphy, Glacial Limits, and Paleoenvironments of the Marresale Area, Western Yamal Peninsula, Russia
Authors: Forman Steven L. , Ingólfsson Ólafur , Gataullin Valery , Manley William , Lokrantz Hanna
Published: September 2002

Stratigraphic records from coastal cliff sections near the Marresale Station on the Yamal Peninsula, Russia, yield new insight on ice-sheet dynamics and paleoenvironments for northern Eurasia. Field studies identify nine informal stratigraphic units from oldest to youngest (the Marresale formation, Labsuyakha sand, Kara diamicton, Varjakha peat and silt, Oleny sand, Baidarata sand, Betula horizon, Nenets peat, and Chum sand) that show a single glaciation and a varied terrestrial environment during the late Pleistocene. The Kara diamicton reflects regional glaciation and is associated with glaciotectonic deformation from the southwest of the underlying Labsuyakha sand and Marresale formation. Finite radiocarbon and luminescence ages of ca. 35,000 to 45,000 yr from Varjakha peat and silt that immediately overlies Kara diamicton place the glaciation >40,000 yr ago. Eolian and fluvial deposition ensued with concomitant cryogenesis between ca. 35,000 and 12,000 cal yr B.P. associated with the Oleny and the Baidarata sands. There is no geomorphic or stratigraphic evidence of coverage or proximity of the Yamal Peninsula to a Late Weichselian ice sheet. The Nenets peat accumulated over the Baidarata sand during much of the past 10,000 yr, with local additions of the eolian Chum sand starting ca. 1000 yr ago. A prominent Betula horizon at the base of the Nenets peat contains rooted birch trees ca. 10,000 to 9000 cal yr old and indicates a >200-km shift northward of the treeline from the present limits, corresponding to a 2° to 4°C summer warming across northern Eurasia.