bluuebunny/crossref_metadata_2025 huggingface dataset:
gp120-mediated induction of the MAPK cascade is dependent on the activation state of CD4+ lymphocytes
Authors: Kinet Sandrina , Bernard Fréderic , Mongellaz Cédric , Perreau Matthieu , Goldman Frederick D. , Taylor Naomi
Published: September 2002

The capacity of the HIV-1 envelope glycoprotein gp120 to induce intracellular signals is thought to contribute to HIV-1 pathogenesis. Here, we report that gp120 binding resulted in activation of the mitogen-activated protein kinase (MAPK) in CD4+lymphocytes prestimulated through their T-cell receptor (TCR). However, gp120 did not activate this pathway in either freshly isolated quiescent T cells or nonproliferating CD4+ lymphocytes prestimulated with the interleukin-7 (IL-7) cytokine. This response was not solely dependent on proliferation per se because proliferating IL-7–prestimulated umbilical cord (UC)–derived T lymphocytes did not exhibit significant MAPK activation upon gp120 binding. Nevertheless, like peripheral blood lymphocytes, MAPK recruitment was induced by gp120 in UC T cells following TCR prestimulation. The lack of a gp120-mediated signaling response was not due to decreased gp120 receptor levels; CD4 expression was modified neither by IL-7 nor by TCR engagement, and high levels of functional CXCR4 were present on IL-7–treated lymphocytes. In addition to CD4 and CXCR4, recent evidence suggests that glycosphingolipids in raft microdomains serve as cofactors for HIV-1 fusion. The ganglioside GM1, a marker of rafts, was augmented in TCR-stimulated but not IL-7–stimulated T lymphocytes, and disruption of rafts inhibited gp120-induced signaling. Thus, stimulation of a mitogenic pathway by gp120 appears to require receptor binding in the context of membrane microdomains. These studies reveal a mechanism via which gp120 may differentially modulate the fate of activated and quiescent T cells in vivo.
Activation of Phosphatidylinositol 3-Kinase Contributes to Insulin-Like Growth Factor I-Mediated Inhibition of Pancreatic β-Cell Death
Authors: Liu Wenli , Chin-Chance Catherine , Lee Eun-Jig , Lowe William L.
Published: September 2002

To begin to determine whether IGF-I treatment represents a potential means of enhancing the survival of islet cell grafts after transplantation, the present studies established a model of β-cell death secondary to loss of trophic support and examined the ability of IGF-I to prevent cell death. The studies were performed using the rat pancreatic β-cell line, INS-1. Incubating INS-1 cells in RPMI 1640 and 0.25% BSA for 48 h increased cell death, as determined by lactate dehydrogenase release, compared with that of cells maintained in RPMI and 10% fetal calf serum. Addition of 100 ng/ml IGF-I to the serum-free medium decreased lactate dehydrogenase release to a level comparable to that found in cells maintained in fetal calf serum. Similar results were seen using a mouse β-cell line, MIN6, infected with an adenovirus expressing IGF-I. Examination of IGF-I-stimulated signaling demonstrated that IGF-I increased the phosphorylation of protein kinase B in both cell lines, whereas IGF-I-induced phosphorylation of the MAPKs, ERK1 and -2, was observed only in INS-1 cells. The effect of IGF-I on phosphorylation of substrates of phosphatidylinositol 3-kinase (PI 3-kinase) or protein kinase B was also examined in INS-1 cells. IGF-I increased the phosphorylation of glycogen synthase kinase 3β, BAD, FKHR, and p70S6 kinase. Another pathway that has been shown to mediate the protective of IGF-I in some cell types is activation of cAMP response element-binding protein (CREB). IGF-I increased CREB phosphorylation at a concentration as low as 10 ng/ml, and this effect was inhibited by H89, a PKA inhibitor, and PD98059, a MAPK kinase inhibitor. Consistent with the effect of IGF-I on CREB phosphorylation, IGF-I increased the transcriptional activity of CREB, although it had no effect on CREB binding to DNA. Use of inhibitors of the PI 3-kinase (LY 294002) or ERK (PD98059) pathways or CREB phosphorylation (H89) in the cell death assay demonstrated partial abrogation of the protective effect of IGF-I with LY 294002. These data demonstrate that IGF-I protects pancreatic β-cells from cell death secondary to loss of trophic support and that, although IGF-I activates several signaling pathways that contribute to its protective effect in other cell types, only activation of PI 3-kinase contributes to this effect in β-cells.
Two New Species of the Lichen Genus Immersaria (Porpidiaceae)
Authors: Calatayud V. , Rambold G.
Published: September 2002

Immersaria olivacea, its lichenicolous fungus Polycoccum decolorans, and Immersaria mehadiana are described as new species from Spain and Romania, respectively. A new combination, Immersaria cupreoatra is proposed, and a revised concept of the genera Bellemerea and Immersaria is supplied.
Ascoma Ontogeny: is this Character Set of any Use in the Systematics of Lichenized Ascomycetes?
Authors: Döring Heidi , Lumbsch H. Thorsten
Published: September 2002

The use of ascoma ontogeny in the systematics of lichenized ascomycetes is reviewed briefly. Two recently studied examples are discussed to illustrate the use of ontogenetic studies to discover phylogenetic relationships. As one example, the Agyriaceae was mainly circumscribed by the ascus type and included diverse genera. Xylographa is characterized by lirelliform apothecia. However, the ascoma development shares the ontogenetic pattern observed in Trapelia and its placement in the family was confirmed. In contrast, Anamylopsora exhibited a substantially different apothecial development and was separated as a family of its own. As a second example, the Candelariaceae is based on chemical characters. With the detection of pulvinic acid derivatives also in the genus Lecanora, the distinction of the Candelariaceae and Lecanoraceae became doubtful. Therefore, the ascoma ontogeny was employed to evaluate this classification and is illustrated here in detail for Candelaria fibrosa. The substantial similarity of the ascoma development found in both families suggests that both might be better united. Finally, a general discussion of the significance of ontogenetic characters in lichen taxonomy is included.
What Molecular Biology has to Tell us at the Species Level in Lichenized Fungi
Authors: Bridge Paul D. , Hawksworth David L.
Published: September 2002

Molecular biological techniques now provide many opportunities for determining relationships between organisms. In lichen-forming fungi, polymerase chain reaction (PCR) amplification can be undertaken with primers that have enhanced specificity for fungi, allowing the recovery of precise regions of the genome of the fungal partner. Such PCR techniques are suitable for the analysis of both fresh and dried specimens of great age, and as the techniques require only minimal amounts of starting material, they are suitable for the analysis of large numbers of specimens. PCR can be used to examine both conserved and variable regions of the fungal genome that may be taxonomically significant, and variability in these sequences can be used to describe species boundaries. The ease of analysis of large numbers of specimens without the need to purify or culture the fungal partner makes analysis and comparison of infra- and inter-specific relationships possible, and provides valuable information into their genetic background. Most molecular analyses undertaken with lichen-forming fungi have considered variation within ribosomal RNA clusters, and in this paper we consider the application and interpretation of such PCR-based analysis in the circumscription of species and in determining concepts for individuality and infra-specific groupings.
The Use of Metabolic Data in Lichenology at the Species and Subspecific Levels
Authors: Lumbsch H. Thorsten
Published: September 2002

The different views on the taxonomic use of chemical characters in lichenology are reviewed using the opposing opinions of W. L. Culberson and Rogers and the somewhat intermediate position of Hawksworth as examples. The differing significance of secondary metabolites is illustrated with two examples in the genus Lecanora. In L. campestris and similar species, the chemistry has been useful to differentiate morphologically similar species, which subsequently were found to differ in minute anatomical differences as well. However, in L. caesiorubella, a remarkable chemical variation can be observed that is not correlated with other differences and is thus interpreted as intraspecific variation. An a posteriori valuation of the taxonomic significance of metabolic data is preferred.
Aspects of the Integration of the Taxonomy of Lichenized and Non-Lichenized Pyrenocarpous Ascomycetes
Authors: Aptroot André
Published: September 2002

The integration of the taxonomy of lichenized and non-lichenized pyrenocarpous ascomycetes is still in progress. Within this group, at least 12 lichenization events, three re-lichenizations and at least 24 de-lichenization events, are supposed to have occurred during evolution. This is evident from the increasing amount of information regarding phylogeny and classification of pyrenocarpous fungi. The total number of lichenization events, including re- and de-lichenization, within all fungi is estimated to be at least 100. However, the vast majority of the pyrenocarpous lichens are concentrated in a few relatively large, presumably monophyletic, groups. In some cases, proposed integrations have proven to be untenable, for example Microtheliopsis and with the Herpotrichiellaceae, Flavobathelium with the Dimeriaceae and most notably the Normandina thallus with the basidiomycetes and its ascocarps with Sphaendina in the Mycosphaerellaceae. The same true for many cases where lichenized taxa were unwittingly included in otherwise non-lichenized groups, such as Didymosphaeria and Massarina, or even described new, presumably non-lichenized, genera like Holstiella, Starbaeckiella and Titanella.
Aspicilia Crespiana, a new Lichen Species from Southern Europe
Authors: Rico Victor J.
Published: September 2002

Aspicilia crespiana Rico is described as a new species from central Spain and Sardinia (Italy). In central Spain it is common and has a well-defined ecology. It is found at middle to high altitudes (from 400 to 1900 m), overgrowing mosses on exposed and horizontal to more or less vertical siliceous rocks. Closely related to the A. contorta (Hoffm.) Kremp. complex, A. crespiana differs in its muscicolous habit and thallus development, consisting of a network of lichenized squamules interlinked by fungal rhizomorphs.
Porina Otagensis (Trichotheliaceae), A New Semi-Aquatic Lichen from Southern New Zealand
Authors: McCarthy P. M.
Published: September 2002

Porina otagensis P. M. McCarthy (Trichotheliaceae) is described from semi-aquatic rocks near Dunedin in the South Island of New Zealand. It has perithecia with a thin, applanate to convex, spreading involucrellum, rather short but broad, 7-septate ascospores that lack a gelatinous sheath, and comparatively broad conidia.
Santessoniella Rugosa (pannariaceae), A New Species from Tasmania
Authors: Henssen Aino , Kantvilas Gintaras
Published: September 2002

Santessoniella rugosa Henssen & Kantvilas is described from south-west Tasmania. The granulose to subfruticose thallus is strongly gelatinous, composed of terete, wrinkled lobes, and bears numerous small, orange apothecia. The species differs from other members of the genus in details of external and internal thallus morphology.
Notes on Some Corticolous and Lignicolous Buellia Species From the Iberian Peninsula
Authors: Giralt Mireia , Barbero Mercedes , Elix John A.
Published: September 2002

The morphology, anatomy, chemistry and ecology of some corticolous and lignicolous species of Buellia from the Iberian Peninsula that contain secondary lichen compounds are discussed, including B. chloroleuca, B. disciformis, B. erubescens, B. hyperbolica and B. leptoclinoides. These species are compared with other corticolous Buellia species that occur outside the study area, including B. arnoldii, B. insignis, B. regularis and B. sanguinolenta. The misunderstood B. zahlbruckneri J. Steiner and B. jorgei, are synonyms of B. erubescens, and the invalid taxon B. zahlbruckneri sensu Schauer non Steiner and B. poeltii, are synonyms of B. chloroleuca. New chemical data on several taxa are reported. A key to the pecies and illustrations of their ascospores are provided.
Fossil Parmelia in new World Amber
Authors: Poinar G. O. , Peterson E. B. , Platt J. L.
Published: September 2002

Two new fossil species (Parmelia ambra Poinar, E.B. Peterson & Platt and P. isidiiveteris Poinar, E.B. Peterson & Platt) are described from Dominican amber. The potential evolutionary value of lichens preserved in amber is discussed.
The Lichen Vegetation of Lake Margins in Britain
Authors: Gilbert Oliver , Giavarini Vince
Published: September 2002

The lichen flora of 40 lakes in England, Scotland and Wales is described and related to ecological variables. A zonation scheme consisting of four overlapping bands of lichen vegetation related to height above water level has been adopted. Due to the lack of scour, and the influence of wave action, they do not correspond exactly to the zones identified beside streams, so have been named ‘splash zones’. About a hundred species are involved, a number being rarely recorded aquatic specialists. The flora of all zones is strongly influenced by the alkalinity and pH of the water which have provided a framework for arranging the communities. Lichens are reliable indicators of the sequence: acid, very soft, soft and medium hard water bodies. An investigation into the effect of man-induced eutrophication was undertaken. Other factors of ecological importance are shade and humidity. The conservation of the lake habitat is discussed and a comparison made between streamside and lakeside communities.
Edge Effects on the Epiphytic Lichen Flora of Picea Abies in Middle Boreal Finland
Authors: Kivistö Laura , Kuusinen Mikko
Published: September 2002

The edge effect of large clear-cuts on the epiphytic lichen flora of Picea abies in old-growth forest fragments was studied at three south-exposed and four north-exposed forest clear-cut edges in middle boreal Finland. The sampling of the species cover on trunk bases was carried out along four transects parallel to the forest margin: (1) at the forest margin, (2) 10 m from the margin, (3) 20 m from the margin and (4) 50 m from the margin. In addition, control trees were sampled > 100 m from nearest edge. Our results showed that the epiphytic lichen species diversity was lower at the forest margin than in the forest interior for sunny south-facing edges, while the species diversity in north-exposed edges was independent of the distance from the forest margin. The cover of a common and abundant lichen species, Parmeliopsis ambigua, was slightly higher at the forest edge and decreased inside the forest for both south-exposed and north-exposed edges.
The Minimal Area of a Foliicolous Lichen Community of Woessia Vasakii
Authors: Bricaud Olivier , Roux Claude
Published: September 2002

The minimal area of a foliicolous lichen community of Woessia vasakii in southern France (West Languedoc, Department of Gard) was studied by the method of the mean similarity coefficients of Sørensen and of Kulcinsky. The determination of the qualitative and quantitative minimal areas, which are c. 30–50 cm2 and 50–80 cm2, respectively, allows the phytosociological study of the foliicolous communities of southern France by the method of integral sampling.
Phylogenetic Reconstruction of Character Development in Physciaceae
Authors: Nordin A. , Mattsson J.-E.
Published: September 2002

A cladistic analysis of the Physciaceae, based on morphological and chemical data, is presented. In the resulting phylogenetic reconstruction two major clades are formed, one containing the foliose genera (Anaptychia, Dirinana, Heterodermia, Hyperphyscia, Physcia, Phaeophyscia, Physconia, Pyxine) and the fruticose Tornabea and the other containing the remaining, mainly crustose genera. Rinodina appears as paraphyletic with representatives both at the base of the tree, at the same level as the two major clades and at the base of the crustose clade. Also Mobergia has a basal position. The characters used and their distribution in the phylogenetic trees are discussed as well as their significance for the identification of monophyletic groups. The history of the family is also briefly hinted at and characters of importance for the recognition of new genera are surveyed. Relevant publications and the variation in secondary chemistry are presented in tables.
The Role of Lichens in Inhibiting Erosion of a Soluble Rock
Authors: Mottershead Derek , Lucas Gerald
Published: September 2002

Soluble rocks undergo erosion by solution when rain falls on an unprotected rock surface. Lichens may act to protect the surface from such erosion, and the protected area may subsequently emerge from the surrounding lowering surface to form an area of higher relief. Specimens of Aspicilia calcarea and Diploschistes diacapsis act in this way on a gypsum surface, creating conical or rounded mounds up to 15 mm in height. In the case of Aspicilia, the lichen centre decays, re-exposing to surface solution the central area, which then corrodes to create a cratered gypsum cone. The gradient of the cone side-slopes is a function of the relative rates of lichen radial growth and rock surface lowering.
Molecular Data Suggest that the Lichen Genus Pertusaria is not Monophyletic
Authors: Thorsten Lumbsch H. , Schmitt Imke
Published: September 2002

The phylogeny of the genus Pertusaria and allied taxa was investigated using nucleotide sequences of the LSU rRNA gene. Sequences from these regions of 15 pertusarialean fungi were aligned to those of three representatives of Agyriales used as outgroup. The alignment was analysed cladistically using maximum parsimony. The Pertusariaceae appear paraphyletic bearing the monophyletic Coccotremataceae on a clade including Ochrolechia and Pertusaria subg. Monomuratae, but monophyly of the family cannot be rejected. The genus Pertusaria is polyphyletic, with the subgenus Monomuratae more closely related to the Coccotremataceae and Ochrolechia than to taxa of the subgenera Pertusaria and Pionospora. Monophyly of the genus Pertusaria is rejected. The monophyly of the subgenera Pertusaria and Pionospora is also rejected. The distribution of selected characters in the Pertusariales is investigated and it is shown that apothecial form and spore wall number have changed in parallel within Pertusaria. The Pertusaria-type ascus is plesiomorphic within the Pertusariaceae and thus cannot be used to circumscribe Pertusaria. The presence of chlorinated xanthones is restricted to Pertusaria s. str
A New Xanthone-Containing Micarea from Northwest Europe and the Pacific Northwest of North America
Authors: Coppins B. J. , Tønsberg T.
Published: September 2002

Micarea xanthonica sp. nov. is described from the western British Isles, westernmost Norway and the Pacific Northwest of North America. It belongs to the M. prasina group, but differs from related species in possessing xanthones in the thallus.
Molecular data support rejection of the generic concept in the Coccotremataceae (Ascomycota)
Authors: Schmitt Imke , Messuti María Ines , Feige G. Benno , Lumbsch H. Thorsten
Published: September 2002

The Coccotremataceae is a small family including two genera: Coccotrema with a crustose, granulate to verrucose thallus and Lepolichen with terete lobes and rhizines. The generic concept based on this morphological difference was re-evaluated using three molecular markers, mt SSU rDNA, nu LSU rDNA, and the nu ITS region. The analysis of the ITS region does not provide sufficient resolution within the Coccotremataceae, while the other two data sets contradict the current generic concept. The mt SSU and nu LSU data sets and the combined analysis of the two data sets all place Lepolichen within Coccotrema. However, an alternative topology with monophyletic Coccotrema cannot be rejected when the ITS data set is included in the combined analyses. This shortcoming of the ITS data set can be overcome by the combined analysis of all three data sets, where monophyletic Coccotrema can be rejected using parametric bootstrapping, as in the mt SSU and nu LSU data sets and combination thereof. It is proposed to reduce Lepolichen into synonymy with Coccotrema. The correct name for the only species previously placed in Lepolichen is Coccotrema coccophontm (Mont.) I. Schmitt, Messuti & Lumbsch.
Cladonia monomorpha, a neglected cup lichen from Europe
Authors: Aptroot A. , Sipman H.J.M. , van Herk C.M.
Published: September 2002

Cladonia monomorpha is recognized as a distinct species in the Cladonia pyxidata group. It is characterized by thallus lobes with narrowly recurved margins, by the presence of discoid, bullate plates on the podetial surface and by long and sometimes branched proliferations of the scyphus margins supporting the apothecium discs. It is described from the Netherlands, where it occurs in acid inland sand dune areas with the highest terrestrial lichen diversity. It appears to be widespread in Europe on siliceous rock and acid sand.
Caloplaca thuringiaca sp. nov., a species from the Caloplaca holocarpa complex
Authors: Søchting Ulrik , Stordeur Regine
Published: September 2002

Caloplaca thuringiaca Søchting & Stordeur is described from detritus on dry south-exposed slopes in Thuringia, central Germany. The species belongs to the Caloplaca holocarpa complex, but is different from the other terricolous taxa described in the complex, which all have alpine or polar distributions.
Use of 14C/C Ratios to Provide Insights into the Magnitude of Carbon Turnover in the Crustose Saxicolous Lichen Caloplaca Trachyphylla
Authors: Bench G. , Clark B. M. , Mangelson N. F. , Clair L. L. St. , Rees L. B. , Grant P. G. , Southon J. R.
Published: September 2002

14C/C ratios in samples from radial transects across individual thalli of Caloplaca trachyphylla collected at two sites were measured and the results used to investigate whether 14C/C data might provide some insight into the magnitude of carbon turnover in this lichen species. The 14C/C data suggest that significant internal recycling/translocation of carbon is unlikely in the sampled thalli. However, converting the 14C/C data for the larger intact thalli sampled at each site to calendar years, using the atmospheric ⊃14C record, does not yield constant or even monotonically varying growth rates. Since crustose lichen growth rates are constant or decrease with thallus size, and since the 14C/C data from these larger thalli show a relatively small spread in 14C/C data values compared to the Northern Hemisphere atmospheric ⊃14C record over the past 50 years, the 14C/C data suggest that carbon turnover may be occurring. Carbon turnover was modelled starting with the atmospheric ⊃14C record. Turnover was incorporated so that for each year in the record a constant percentage of the total carbon was lost annually and replaced by new photosynthetically fixed carbon with a 14C/C ratio equal to that of the contemporary atmosphere. The 14C/C data from the radial samples were then converted to a calendar year using the model record. Constant annual carbon turnover values of 0, 0·5, 1, 1·5, 2, 2·5, 3, 3·5, 4, 4·5, 5, 5·5, 6, 7, 8, 9, 10, 15, 20, 25 and 50% were modelled. Carbon turnover values between 3 and 6% created ⊃14C model records that when applied to 14C/C data from the thalli produced constant radial growth rates that were: (1) identical for all lichens at a given site, and (2) independent of lichen size at a given site. The 14C/C data further indicate that annual carbon turnover in this species of lichen is <10%, independent of the nature of thallus radial growth. The data and modelling suggest that carbon turnover might provide a simple explanation for the 14C/C data from the thalli and might explain the discrepancies between the standard atmospheric ⊃14C record and the 14C/C ratios observed in C. trachyphylla.
Surface-Exposure Chronology Using in Situ Cosmogenic 3He in Antarctic Quartz Sandstone Boulders
Authors: Brook Edward J. , Kurz Mark D.
Published: September 2002

In situ-produced cosmogenic helium (3Hec) provides a new tool for constraining histories of Quaternary geomorphic surfaces. Before general application of the technique, however, the systematics and production rates of 3Hec must be well understood. In a companion study, 3He and 10Be data from sandstone and granite boulders in the Dry Valleys region of Antarctica have been used to constrain the ages of an important moraine sequence formed by the Taylor Glacier. Data from these deposits also provide information about the systematics of 3He in quartz that has important implications for geochronology based on 3Hec. In contrast to previous results from olivine and clinopyroxene, crushing quartz in vacuo releases helium with high 3He/4He ratios (up to 148 × Ra, where Ra is the atmospheric 3He/4He ratio), indicating that crushing cannot be used to determine the isotopic composition of trapped (i.e., noncosmogenic) helium in quartz. Analysis of 3He in different size fractions of the same samples indicates significant 3 He loss not predicted by existing 3He diffusion data for quartz. The origin of the discrepancy is not clear, but loss from these samples is not as significant as suggested by the limited data of previous studies.
Are Soil Tongues in Northeastern Indiana Periglacial Relics or Active Fingering Zones?
Authors: Hinkel Kenneth M.
Published: September 2002

Soil tongues, or soil fingers, have been identified along the walls of an active gravel pit in northeastern Indiana. Locally enhanced pedogenesis, primarily carbonate leaching and clay illuviation, has resulted in wedge- and cone-shaped extensions of the B horizon into the underlying calcareous glaciofluvial sediments. Although previously described in the literature, the features at this site are considered unusual both for the numerous well-defined tongues and for the regularity of tongue spacing, which gives the illuviation front the appearance of a high-amplitude sinusoidal wave train. Depth to the illuviation front was measured at 0.25-m intervals along a 40-m exposure. Statistical tests indicate that the spatial pattern is nonrandom. The data were transformed using Fourier methods, and the resulting variance spectrum show a peak intensity at wavelengths bracketing 1.5 m. The results of these analyses suggest a surficial or near-surface topographic control. Climatic conditions following local glacier recession favored periglacial activity, and there is some evidence to suggest development of thermal contraction cracks and nonsorted or poorly sorted polygons 1.5 m in diameter. As an alternative hypothesis, laboratory experiments suggest that regularly spaced fingers can develop in homogeneous materials when instability occurs at the wetting front. In this case, soil tongues cannot be used as relict indicators of periglacial activity.
Southern Oscillation Signal in South American Palaeoclimatic Data of the Last 7000 Years
Authors: Martin Louis , Fournier Marc , Mourguiart Philippe , Sifeddine Abdelfatah , Turcq Bruno , Flexor Jean-Marie , Absy Maria Lucia
Published: September 2002

During strong El Niño events, rainfall anomalies and changes in wind patterns are observed in different regions of South America. Along the central Brazilian coast, during the 1983 El Niño year, the frontal systems were blocked to the south, provoking a reversal of the longshore sand transport. Long-duration reversals of longshore transport were also recorded in Holocene beach-ridge terraces from the Rio Doce coastal plain. This led to the formulation of a model relating these reversals of longshore transport to El Niño-like conditions. El Niño-like conditions are past average climate situations that generate the same perturbations as the strong El Niño events observed during the last decade. They are likely to correspond to the long-duration low phase of the Southern Oscillation. To confirm this hypothesis we compared the Holocene beach-ridge record with other palaeoenvironmental records from regions where strong El Niño events would have a substancial signal as well: (1) water-level fluctuations of Lake Titicaca, (2) a pollen and sediment record in an eastern Amazonian lake, (3) changes of the Rio Xingu discharge in eastern Amazonia, and (4) variations of sand supply at the Rio Piura and Rio Chira outlets in the Sechura Desert. The occurrences of El Niño-like conditions were numerous before 3900-3600 yr B.P., absent between 39003600 and 2800-2500 yr B.P., and infrequent after 2800-2500 yr B.P.
Revised Ages for Laminated Sediment and a Holocene-Marker Diatom from the Northern California Continental Slope
Authors: Hemphill-Haley Eileen , Gardner James V.
Published: September 2002

Conventional and accelerator mass spectrometry 14C ages indicate that laminated sediment in three cores from the northern California continental slope near 38°N and 39°N were deposited between 42,000 and 25,000 yr B.P. This revises and refines our previous estimates that laminated sediment accumulated during the late Pleistocene to early Holocene (J. V. Gardner and E. Hemphill-Haley, 1986, Geology 14, 691-694). Preservation of laminated sediment on the upper slope in this area suggests a period of intense coastal upwelling, high primary productivity, and resultant depletion of oxygen in bottomwaters preceding the onset of global glacial conditions. The transition from Pleistocene to Holocene conditions, and the establishment of a modern climatic regime driven by the California Current, included the incursion of the subtropical diatom, Pseudoeunotia doliola. P. doliola is common in sediment younger than about 10,000 yr and thus is a reliable marker species for identifying Holocene deposits off northern California.
Fossil Arthropods from a Full-Glacial Site in Northeastern Italy
Authors: Foddai Donatella , Minelli Alessandro
Published: September 2002

Fossil remains of beetles and oribatid mites from a peat deposit dated 18,870 ± 300 yr B.P. near Verona, northeastern Italy, represent the first insect fauna of its kind from the last glacial maximum to be described from Italy. The assemblage includes the ground beetleAmara alpina,whose distribution today in Europe is restricted to mountains in Scandinavia and Scotland. Ecological requirements and geographic distribution of recent populations of the identified species suggest mesic habitats with standing water and peat bogs during the glacial maximum. The paleoenvironment was comparable to present-day lowland moors in Scandinavia or mesic environments above 1000 m altitude on the southern slopes of the Alps. The climate is inferred to have been colder and wetter than today. Mean July temperature may have been 8-9°C lower than at present.
Middle Pleistocene Climate Change in the Colorado Rocky Mountains Indicated by Fossil Mammals from Porcupine Cave
Authors: Wood David L. , Barnosky Anthony D.
Published: September 2002

Fossiliferous sediments from The Pit Locality in Porcupine Cave, Park County, Colorado, span multiple glacial and interglacial cycles between ca. 800,000 and 400,000 yr B.P. at 2900 m elevation. The uppermost cycle probably represents oxygenisotope glacial Stage 12 (stratigraphic Levels 4 and 3) and interglacial Stage 11 (Levels 3, 2, and 1) as determined by arvicoline biostratigraphic data that place the sequence between 487,000 and 365,000 yr B.P. A no-analog assemblage comprising the bog lemmingMictomys meltoni(of theM. borealislineage) and the sagebrush voleLemmiscus curtatus(=Lagurus curtatus) characterizes both the glacial and the interglacial deposits. Climatographs for these two species suggest that, compared to present conditions, the following local climatic limits can be imposed on oxygenisotope Stages 12 and 11: (1) January effective moisture was greater, resulting from average temperatures of at least 5°C cooler and/or at least 15 mm more precipitation; (2) January solar radiation was lower by at least 75 Langleys; (3) effective July solar radiation might have been lower by at least 50 Langleys. Seasonal temperature extremes were not necessarily different from those of the present, but seasonal precipitation was more equable. Relative abundance of mammal taxa and sedimentological data indicate that aridity increased at the onset of the interglacial.
Tectonic Speleogenesis of Devils Hole, Nevada, and Implications for Hydrogeology and the Development of Long, Continuous Paleoenvironmental Records
Authors: Riggs Alan C. , Carr W.J. , Kolesar Peter T. , Hoffman Ray J.
Published: September 2002

Devils Hole, in southern Nevada, is a surface collapse into a deep, planar, steeply dipping fault-controlled fissure in Cambrian limestone and dolostone. The collapse intersects the water table about 15 m below land surface and the fissure extends at least 130 m deeper. Below water, most of the fissure is lined with a >30-cm-thick layer of dense maxillary calcite that precipitated continuously from groundwater for >500,000 yr. The thick mammillary calcite coat implies a long history of calcite-supersaturated groundwaters, which, combined with the absence of dissolutional morphologies, suggests that Devils Hole was not formed by karst processes. Devils Hole is located in a region of active extension; its tectonic origin is shown by evidence of spreading of its planar opening along a fault and by the orientation of its opening and others nearby, perpendicular to the northwest-southeast minimum principal stress direction of the region. Most Quaternary tectonic activity in the area, including seismicity and Quaternary faults and fractures, occurs on or parallel to northeast-striking structures. The hydrogeologic implications of this primarily structural origin are that fracture networks and caves opened by extensional tectonism can act as groundwater flowpaths functionally similar to those developed by karst processes and that, during active extension, transmissivity can be maintained despite infilling by mineral precipitation. Such extensional environments can provide conditions favorable for accumulation of deposits preserving long, continuous paleoenvironmental records. The precipitates in Devils Hole store chronologies of flow system water-level fluctuations, hydrochemistry, a half-million-yr proxy paleoclimate record, evidence of Devils Hole's tectonic origin, and probably atmospheric circulation.
Long Pleistocene Pollen Records from the Praclaux Crater, South-Central France
Authors: Reille Maurice , de Beaulieu Jacques-Louis
Published: September 2002

A 46-m core of lake sediments, obtained from the center of the explosion crater of Praclaux (Haute-Loire, Velay, France), was studied on the basis of 368 pollen spectra. Five temperate forest episodes alternating with phases indicative of glacial climates are recorded. Two of these episodes show vegetation successions representative of full interglaciations; the oldest is contemporaneous with the Holsteinian interglaciation. A thick trachytic tephra permits correlation to be established with the pollen sequence from Lac du Bouchet. This comparison indicates the presence of two complete interglaciations between the Holsteinian and the Eemian that are the equivalents of marine isotope stages 7 and 9. The Holsteinian therefore corresponds to isotope stage 11.
Simulating Magnetic Susceptibility Profiles in Loess as an Aid in Quantifying Rates of Dust Deposition and Pedogenic Development
Authors: Anderson Robert S. , Hallet Bernard
Published: September 2002

Magnetic susceptibility profiles χ(z) in loess sequences reflect a combination of two climatically modulated processes: dust deposition and pedogenic development. Prominent soils with high χ values, for example, likely reflect periods of slow dust deposition, and warm wet conditions favorable for rapid chemical weathering. To refine our understanding of the climate records contained in loess, we develop a numerical model as a tool for exploring quantitatively the integrated record of the temporal variation in rates of loess aggradation and soil development contained in χ profiles. In our model, the aggrading loess is pedogenically altered in a reactive zone near the ground surface. The strength of the χ signal is dictated by both the depth-dependent intensity of pedogenic processes and the rate of dust accumulation, which dictates the total time a loess parcel spends in the near-surface reactive zone. The model can accommodate both pedogenic production of magnetically susceptible minerals and arrival of magnetically susceptible grains as eolian dust. To explore the model performance and develop a sense of time and length scales implicit in χ profiles, we first examine simple synthetic cases with idealized steady and cyclic climatic forcing. Reported χ profiles in three Chinese loess sequences at varying distances from the western China dust source are then modeled in two illustrative ways: (i) by imposing a specific dust deposition rate history that is proportional to the dust accumulation rate history reported from western Pacific deep-sea cores, allowing the time variation of pedogenic rates to be calculated directly from χ profiles; and (ii) by imposing both dust accumulation and pedogenic rate histories that are independently scaled by the deep-sea δ18O history, which reflects global climate cycles to which regional climate forcing is linked. We find that the zone of pedogenic activity is roughly 0.5–1.0 m thick, both deposition rate and pedogenic intensity have varied dramatically over the last 140,000 yr, the age structure of the Luochuan loess sequence is best fit by driving the model with the δ18O record, and environmental conditions must have been anomalously favorable for pedogenesis during isotope stage 3 at all three sites. Finally, we advocate the assembly of a variety of data types at a suite of sites within any loess field that taken together will better constrain the temporal and spatial patterns of climatically modulated deposition and pedogenic processes.
Implications for Deglaciation Chronology from New AMS Age Determinations in Central West Greenland
Authors: van Tatenhove Frank G. M. , van der Meer Jaap J. M. , Koster Eduard A.
Published: September 2002

New evidence has been obtained for the age of the Umı̂vı̂t/Keglen and Ørkendalen moraine systems close to the present ice sheet margin in central West Greenland. The Umı̂vı̂t/Keglen moraine system is dated at 7500 to 650014C yr B.P., which is older than the previously assumed date of 7300 to 600014C yr B.P. The Ørkendalen system is now dated at 6200 to 560014C yr B.P. against earlier estimates of 300 to 70014C yr B.P. The new age is based on AMS radiocarbon-dated organic material within depressions between morainic ridges belonging to the Ørkendalen system. A major implication of the new age is that ice margin positions prevailed for about 6000 years behind the present ice sheet margin. The retreat behind the present margin could be substantial, and in the light of deglaciation rates prior to the Ørkendalen phase, may be ca. 10's of kilometers rather than kilometers. Circumstantial evidence is found for the retreat of the ice sheet margin behind its present position during the Holocene climatic optimum. The results, placed into a time frame of deglaciation since the last glacial maximum, enable comparison with Greenland ice sheet models and ice core records.
Late Pleistocene and Holocene Seasonal Temperatures Reconstructed from Fossil Beetle Assemblages in the Rocky Mountains
Authors: Elias Scott A.
Published: September 2002

Mutual Climatic Range (MCR) analysis was applied to 20 fossil beetle assemblages from 11 sites dating from 14,500 to 400 yr B.P. The fossil sites represent a transect of the Rocky Mountain region from northern Montana to central Colorado. The analyses yielded estimates of mean July and mean January temperatures. The oldest assemblage (14,500 yr B.P.) yielded mean July values of 10–11°C colder than present and mean January values 26–30°C colder than present. Postglacial summer warming was rapid, as indicated by an assemblage dating 13,200 yr B.P., with mean July values only 3–4°C cooler than modern. By 10,000 yr B.P., several assemblages indicate warmer-than-modern mean summer and winter values. By 9000 yr B.P., MCR reconstructions indicate that both summer and winter temperatures were already declining from an early Holocene peak. Mean July values remained above modern levels and mean January values remained below modern levels until 3000 yr B.P. A series of small-scale oscillations followed.
Radiocarbon Ages and Environments of Deposition of the Wono and Trego Hot Springs Tephra Layers in the Pyramid Lake Subbasin, Nevada
Authors: Benson Larry V. , Smoot Joseph P. , Kashgarian Michaele , Sarna-Wojcicki Andrei , Burdett James W.
Published: September 2002

Uncalibrated radiocarbon data from core PLC92B taken from Wizards Cove in the Pyramid Lake subbasin indicate that the Trego Hot Springs and Wono tephra layers were deposited 23,200 ± 300 and 27,300 ± 30014C yr B.P. (uncorrected for reservoir effect). Sedimentological data from sites in the Pyramid Lake and Smoke Creek–Black Rock Desert subbasins indicate that the Trego Hot Springs tephra layer was deposited during a relatively dry period when Pyramid Lake was at or below its spill point (1177 m) to the Winnemucca Lake subbasin. The Wono tephra layer was deposited when lake depth was controlled by spill across Emerson Pass sill (1207 m) to the Smoke Creek–Black Rock Desert subbasin.18O data from core PLC92B also support the concept that the Trego Hot Springs tephra fell into a relatively shallow Pyramid Lake and that the Wono tephra fell into a deeper spilling lake.
Is There Evidence for Solar Forcing of Climate in the GISP2 Oxygen Isotope Record?
Authors: Stuiver M. , Braziunas T. F. , Grootes P. M. , Zielinski G. A.
Published: September 2002

Changes in solar constant over an 11 yr cycle suggest a certain, but limited, degree of solar forcing of climate. The high-resolution climate (oxygen isotope) record of the Greenland GISP2 (Greenland Ice Sheet Project 2) ice core has been analyzed for solar (and volcanic) influences. The atmospheric 14C record is used as a proxy of solar change and compared to the oxygen isotope profile in the GISP2 ice core. An annual oxygen isotope profile is derived from centimeter-scale isotope measurements available for the post-A.D. 818 interval. Associated extreme summer and winter isotope ratios were found to yield similar climate information over the last millennium. The detailed record of volcanic aerosols, converted to optical depth and volcanic explosivity change, was also compared to the isotope record and the oxygen isotope response calibrated to short-term volcanic influences on climate. This calibration shows that century-scale volcanic modulation of the GISP2 oxygen isotope record can be neglected in our analysis of solar forcing. The timing, estimated order of temperature change, and phase lag of several maxima in 14C and minima in18O are suggestive of a solar component to the forcing of Greenland climate over the current millennium. The fractional climate response of the cold interval associated with the Maunder sunspot minimum (and 14C maximum), as well as the Medieval Warm Period and Little Ice Age temperature trend of the past millennium, are compatible with solar climate forcing, with an order of magnitude of solar constant change of ∼0.3%. Even though solar forcing of climate for the current millennium is a reasonable hypothesis, for the rest of the Holocene the century-scale events are more frequent in the oxygen isotope record than in the 14C record and a significant correlation is absent. For this interval, oceanic/atmospheric circulation forcing of climate may dominate. Solar forcing during the surprisingly strong 1470 yr climate cycle of the 11,000–75,000 yr B.P. interval is rather hypothetical.
Evidence of Dry and Cold Climatic Conditions at Glacial Times in Tropical Southeastern Brazil
Authors: Behling Hermann , Lichte Martin
Published: September 2002

Last-glacial paleoenvironments have been reconstructed from a pollen and charcoal record analyzed in organic sediments and dated between ca. 18,000 and >48,00014C yr B.P. The site is located near the village Catas Altas in the lower highland region of southeastern Brazil. The last-glacial landscape was covered by extensive areas of subtropical grasslands and small areas of gallery forests along the rivers, where tropical semideciduous forests and cerrado ecosystems exist today. The subtropical gallery forests were composed ofAraucariaforest trees such asAraucaria angustifolia, Podocarpus, Drimys, Ilex,andSymplocos.Paleofires were frequent. The record indicates that subtropical grassland vegetation, which today is found in patches on the highlands in southern Brazil (especially in the state of Santa Catarina), expanded from southern Brazil to southeastern Brazil, over a distance of more than 750 km, from latitudes of about 28° S to at least 20° S. The completely different last-glacial environment, in comparison to the present-day environment, reflects a dry and cold climate with strong frosts during the winter months. Temperatures of 5°–7°C below those of the present are inferred for the last glaciation.
A 40,000-yr Pollen and Diatom Record from Lake Tritrivakely, Madagascar, in the Southern Tropics
Authors: Gasse Françoise , Van Campo Elise
Published: September 2002

Links between southern and northern hemisphere climates during the Late Quaternary are poorly known, partly due to the scarcity of continuous climatic records in the southern tropics. Pollen and diatom evidence from Lake Tritrivakely (19°47′S) provides information on vegetational and hydrological changes in the central highlands of Madagascar over the past 40,000 yr. Most of the record reflects natural environmental variability since humans arrived on the island ca. 2000 yr B.P. During glacial times, the migration of mountain plants toward lower altitudes is consistent with a temperature decrease and with reduced atmospheric CO2levels. In the lake, a positive mean annual hydrologic balance, from 38,000 to 36,000 and from 17,500 to 9800 cal yr B.P., coincided with periods of decreasing summer insolation and preceded by several millennia lake rises in the northern tropics. A negative hydrologic budget during periods of maximum seasonal contrast in solar radiation is partly attributed to high summer evaporation rate. The last glacial maximum was cool and dry. The deglacial warming occurred in two steps. The first step, accompanied by an increase in wetness, occurred abruptly at ca. 17,000 cal yr B.P., about two millennia earlier than in the northern hemisphere. It is abundantly documented in southern terrestrial data. The second step, at 15,000 cal yr B.P., was in phase with the first major temperature change in the northern hemisphere.