bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Lichens Of Rarotonga, Cook Islands, South Pacific Ocean II: Parmeliaceae
Authors: Simone Louwhoff H. J. J. , Elix John A. 
Published: September 2002

AbstractTen parmelioid taxa in five genera were identified from Rarotonga, Cook Islands, South Pacific Ocean. These comprise: three species of Bulbothrix, one species of Canoparmelia, four species of Parmotrema, one species of Rimelia and one species of Xanthoparmelia. Canoparmelia rarotongensis Louwhoff & Elix is described as new, being distinguished from other species of this genus by its unique secondary chemistry (lecanoric acid) and conspicuous, inflated isidia. The majority of parmelioid lichens on Rarotonga have cosmopolitan and pantropical distributions. Bulboihrix is reported for the first time from the Polynesian region.
Sulcopyrenula, A New Pyrenocarpous Lichen Genus (Pyrenulaceae, Lichenized Ascomycota)
Authors: Harada H. 
Published: September 2002

AbstractSulcopyrenida H. Harada gen. nov. is described. It differs from other genera of Pyrenulaceae by having longitudinally sulcate spores. The genus is represented by two species: S. canellae-albae (Fée) H. Harada comb. nov. and S. staurospora (Tuck.) H. Harada comb. nov. Both species have been previously reported from N. and S. America, and the latter species is now reported from Asia.
Proposal for a Standardized Nomenclature and Characterization Of Insoluble Lichen Pigments
Authors: Meyer Barbara , Printzen Christian 
Published: September 2002

AbstractA method for the characterization of insoluble lichen pigments is presented. The method relies on pH–dependent colour reactions before and after pretreatment with HNO3. Diagnostic reactions for 22 different pigments and a key for their identification are given. A standardized nomenclature and a procedure similar to the typification of species in systematic botany is proposed in order to avoid ambiguous naming.
Bark pH and susceptibility to toxic air pollutants as independent causes of changes in epiphytic lichen composition in space and time
Authors: van Herk C. M. 
Published: September 2002

AbstractThe lichen composition on wayside Quercus robur in the Netherlands was related tobark properties (pH, EC, NH4+, SO42-, NO3-)and levels of air pollution (SO2 and NH3). The pH of the bark and the susceptibility to toxic substances appear to be the two major primary factorsaffecting epiphytic lichen composition. These factors have independent effects on the lichen composition.Most of the so-called nitrophytic species appear to have a low sensitivity to toxiceffects of SO2; their only requirement being a high bark pH. An increased bark pH appears to be the primary cause of the enormous increase in nitrophytic species and the disappearance of acidophytic species over the last decade in the Netherlands. Measurements of ambient NH3 concentrations in air show that there is a nearly linear relationship between the NH3concentration andthe abundance of nitrophytes on Quercus. The abundance of nitrophytes was not correlated with SO2 concentrations. Most of the acidophytic species appear very sensitive to NH3 since in areas with concentrations of 35 µg m-3 or more, all acidophytic species have disappeared. Current methods using species diversity to estimate or monitor SO2 air pollution need some modification, otherwise the air quality may be erroneously considered to be relatively good in areas with high NH3 levels.
A new method for the accurate in situ monitoring of chlorophyll a fluorescence in lichens and bryophytes
Authors: Schlensog Mark , Schroeter Burkhard 
Published: September 2002

AbstractA new method has been developed to measure chlorophyll a fluorescence of bryophytes and lichens in situ in the field. Specially designed aluminium stands fixed to rocks or other suitable substrata allow several cryptogam thalli to be measured sequentially with only one pulse amplitude modulated (PAM) chlorophyll a fluorescence analyser. The stands guarantee a fixed position for the fluorescence probe in relation to the thallus surface and also provide the possibility to darken the thalli so that both the apparent and the potential quantumefficiency of PSII (▵F/Fm′ and Fv/Fm) can be measured. A detailed analysis of chlorophyll a quenching parameters (qP, qN, NPQ) can also be performed with only minimal changes in the environmental conditions. The method allows easy detection of periods of metabolic activity and inactivity of the poikilohydric organisms. In combination with gas–exchange and microclimatic measurements the carbon balance also can be calculated. The method is described in detail and examples of its application in the field are presented
Subdivision of Late Pleistocene Moraines in the Cordillera Blanca, Peru, Based on Rock-Weathering Features, Soils, and Radiocarbon Dates
Authors: Rodbell Donald T. 
Published: September 2002

AbstractThe progressive development of unusual rock-weathering features and soils and minimum-limiting radiocarbon dates provide a basis for subdividing four groups of late Pleistocene moraines on the west side of the Cordillera Blanca, northern Peru (9°20′1°000′S, 77°10′-77°30′W). Boulders on the youngest late Pleistocene moraines have 10 to 14-cm-tall weathering posts; soils on these moraines yield mean profile development index (PDI) values of 0.05 ± 0.04 (±1σ). These moraines date between ca. 13,500 and 9700 ± 500 yr B.P., older than previously postulated. The next older moraines have boulders with weathering-post heights between 20 and 25 cm and soils with PDI values of 0.08 ± 0.07, and were deposited prior to 13,280 ± 190 yr B.P., probably during the last glacial maximum (marine isotope stage 2). Moraines from an older glaciation have boulders with weathering posts between 39 and 50 cm high, soils that yield PDI values of 0.21 ± 0.07, and are older than 19,700 ± 340 yr B.P. Boulders on moraines from a still older glaciation have lost ca. 50% of their above-ground volume, and have weathering posts between 62 and 70 cm high. PDI values for soils on these moraines are 0.32 ± 0.06. Linear and logarithmic models of weathering-post and soil development with time are used to estimate minimum and maximum ages for the two oldest moraine groups. Linear models suggest that the second oldest moraines are between ca. 20,500 and 46,500 yr B.P., and that the oldest moraines are between ca. 29,000 and 72,000 yr B.P. In contrast, logarithmic models suggest ages of greater than ca. 75,500 yr B.P. and greater than ca. 500,000 yr B.P., respectively.
Asynchronous Droughts in California Streamflow as Reconstructed from Tree Rings
Authors: Earle Christopher J. 
Published: September 2002

AbstractStreamflow since 1560 A.D. for four rivers within the Sacramento River Basin, California, has been reconstructed dendroclimatically. Both the highest and the lowest reconstructed streamflows occurred during the historical period, with high flows from 1854 to 1916 and low flows from 1917 to 1950. Prolonged (decade-scale) excursions from the mean have been the norm throughout the reconstructed period. The periods of high and low streamflow in the Sacramento Basin are generally synchronous with wet and dry periods reconstructed by dendroclimatic studies in the western United States. The record indicates a number of asynchronous droughts or wet years. The strongest contrasts are developed between northern (western Washington and Oregon or the Columbia Basin) and southern (the Sacramento Basin or central California) climate regions. These asynchronous events may be due to variation in the latitude of the subtropical high and in the latitudinal position of winter storms coming off the Pacific. No association was found with El Niño-Southern Oscillation events.
Toba Ash on the Indian Subcontinent and Its Implications for Correlation of Late Pleistocene Alluvium
Authors: Acharyya Subhrangsu Kanta , Basu Prabir Kumar 
Published: September 2002

AbstractThe Toba ash occurs extensively in the Indian subcontinent and marks a ca. 74,000-yr-old event. In the Bay of Bengal and Indian Ocean it is about 10 cm thick, whereas in several alluvial basins, it is usually 1-3 m thick. The latter occurs in a partly reworked state but as nearly chemically pure first-cycle sediments, The ash has a broad northwesterly dispersal pattern. Samples of ash from the Indian subcontinent compare closely with the youngest (74,000 yr B.P.) Toba Tuff and the deep-sea Toba ash in bulk chemical composition, REE signature, and bubble-wall shard morphology. However, a more proximally located and thicker (2-5 m) ash-bed, from the alluvial basins in the gneissic area and close to east coast, has a lower magnitude negative Eu anomaly, possibly because of minor contamination by feldspathic silt. Quaternary sediments in the central Narmada and middle Son basins contain rich late and middle Pleistocene mammalian and cultural records. Based on the presence of the ash layer marker and stratigraphic relations, late Pleistocene sediments within the subcontinent can be correlated with those from central India and the deep sea.
Quaternary Glaciations in the Río Mendoza Valley, Argentine Andes
Authors: Espizua Lydia E. 
Published: September 2002

AbstractIn the Río Mendoza valley, five Pleistocene drifts and one Holocene drift are distinguished by multiple relative-age criteria, including surface-rock weathering, development of rock varnish, moraine morphology, soil-profile development, and stratigraphic relationships. Several absolute ages suggest a preliminary chronology. During the oldest (Uspallata) glaciation, a system of valley glaciers flowed 110 km from the Andean drainage divide and 80 km from Cerro Aconcagua to terminate at 1850 m. Drift of this ice advance is older than a widespread tephra dated by fission-track at 360,000 ± 36,000 yr. During the Punta de Vacas advance, ice terminated at 2350 m, while during the subsequent Penitentes advance, the glacier system ended at 2500 m. A travertine layer overlying Penitentes Drift has U-series age of 24,200 ± 2000 yr B.P. The distribution of Horcones Drift, which is inferred to represent the last glacial maximum, delimits an independent ice stream that flowed 22 km down Horcones valley to 2750 m. A later readvance (Almacenes) reached 3250 m. Confluencia Drift is considered to be Neoglacial in age and extends downvalley to 3300 m. The moraine sequence is compared with those studied by Caviedes (1972) along Río Aconcagua on the Chilean flank of the Andes.
Climate-Volcanism Feedback and the Toba Eruption of ∼74,000 Years Ago
Authors: Rampino Michael R. , Self Stephen 
Published: September 2002

AbstractA general feedback between volcanism and climate at times of transition in the Quaternary climate record is suggested, exemplified by events accompanying the Toba eruption (∼74,000 yr ago), the largest known late Quaternary explosive volcanic eruption. The Toba paroxysm occurred during the δ18O stage 5a-4 transition, a period of rapid ice growth and falling global sea level, which may have been a factor in creating stresses that triggered the volcanic event. Toba is estimated to have produced between 1015 and 1016 g of fine ash and sulfur gases lofted in co-ignimbrite ash clouds to heights of at least 32 ± 5 km, which may have led to dense stratospheric dust and sulfuric acid aerosol clouds. These conditions could have created a brief, dramatic cooling or "volcanic winter," followed by estimated annual Northern Hemisphere surface-temperature decreases of ∼3° to 5°C caused by the longer-lived aerosols. Summer temperature decreases of ⩾10°C at high northern latitudes, adjacent to regions already covered by snow and ice, might have increased snow cover and sea-ice extent, accelerating the global cooling already in progress. Evidence for such climate-volcanic feedback, following Milankovitch periodicities, is found at several climatic transitions.
Evidence for Regional Stream Aggradation in the Central Oregon Coast Range during the Pleistocene-Holocene Transition
Authors: Personius Stephen F. , Kelsey Harvey M. , Grabau Paul C. 
Published: September 2002

AbstractLow, nearly continuous terraces of similar age are present along streams in drainage basins that range in size from Drift Creek (190 km2) to the Umpqua River (11,800 km2) in the Oregon Coast Range. Radiocarbon ages from near the bose of fluvial sediments underlying these terraces are clustered at about 9000-11,000 14C yr B.P. Beveled bedrock surfaces (straths) that underlie the fluvial sediments are 1-8 m above summer stream levels and are present along most of the nontidal reaches of the rivers that we studied. Where exposed, the bedrock straths are overlain by 2-11 m of fluvial sediment that consists of a bottom-stratum (channel) facies of sandy pebble-cobble gravel and a top-stratum (overbank) facies of sandy silt or silt. Eight radiocarbon ages from the fluvial sediments allow correlation of the lowest continuous terrace over a wide area and thus indicate that a regional aggradation episode occurred in Coast Range drainage basins during the Pleistocene-Holocene transition. The cause of such widespread aggradation is unknown but may be related to climate-induced changes in the frequency of evacuation of colluvium from hollows, which are common in all drainage basins in the region.
Paleoclimatic Significance of the Stable Isotopic Composition and Petrology of a Late Pleistocene Stalagmite from Botswana
Authors: Holmgren Karin , Karlén Wibjörn , Shaw Paul A. 
Published: September 2002

AbstractHigh-resolution δ18O and δ13C analyses of a stalagmite from Lobatse II Cave reveal late Pleistocene environmental changes in Botswana. Large shifts in δ18O and δ13C are observed between two main periods of deposition. The first period, between 51,000 and 43,000 yr B.P., was warm and humid and may have been associated with some C3 vegetation. The second period, between 27,000 and 21,000 yr B.P., had temperatures approximately 2°C lower, and vegetation dominated by drought-adapted C4 plants. The intervening period, between 43,000 and 27,000 yr B.P., bounded by two major hiatuses in stalagmite growth, produced discontinuous speleothem formation, probably under dry conditions. New 230 Th/234U mass spectrometry age determinations for the stalagmite generally agree with previously measured 230 Th/234U ages.
Dynamical Processes on Desert Pavements and the Healing of Surficial Disturbances
Authors: Haff Peter K. , Werner B.T. 
Published: September 2002

AbstractMature desert pavements are traditionally regarded as hallmarks of stability, but their stability is dynamic, not static. In a study aimed at documenting this dynamic stability and its role in healing surface disturbances, experiments were performed over a 5-yr period on small cleared patches, or plats, on pavement surfaces in Panamint Valley, California. These experiments show that stones from plat edges begin to resurface the clearing at rates of about 1% per year on 40-cm-square plats and 10% per year on 10-cm-square plats. Stones contributing to the regenerated pavement have smaller average diameters than stones on the surrounding pavement. Cavities 5–10 cm deep, formed in mature pavement by removal of embedded boulders, fill by ravel and slope failure. After five years, cavity depth has been reduced by as much as 60%. Forty-year-old boulder cavities are nearly completely refilled and have been repaved by smaller than average pavement stones. Gaps caused by removal of small stones (2–3 cm) have completely healed in 5 yr. Displacement of surface stones by small animals is a major component of the healing process.
Termination of the Last Glaciation in the Iberian Peninsula Inferred from the Pollen Sequence of Quintanar de la Sierra
Authors: Peñalba M. Cristina , Arnold Maurice , Guiot Joël , Duplessy Jean-Claude , de Beaulieu Jacques-Louis 
Published: September 2002

AbstractA 4.5-m-thick late-glacial pollen sequence, supported by 17 AMS 14C dates, has been investigated at the Quintanar de la Sierra marshland (Iberian cordillera, north-central Spain). Pollen zones were defined that correspond to successive phases in vegetation history during the end of the Late Würm, late-glacial interstade, and Younger Dryas periods. A transfer function approach has been adopted to derive quantitative climate estimates from the pollen assemblage data. A first expansion ofJuniperus and Hippophae, about 13,500 14C yr B.P., indicates the beginning of the late-glacial interstade which is characterized by a Juniperus–Betula–Pinus succession that suggests higher temperatures and moisture than during full-glacial time. The Younger Dryas interval is recorded by a 120-cm-thick sediment unit that is dominated by herbaceous pollen. Transfer function estimates suggest that the climate during this period was cold, with low precipitation during most of the year, although not in summer. The Holocene arboreal recolonization in the area started about 10,000 14C yr B.P., with a renewed Juniperus–Betula–Pinus succession related to a strong increase in annual temperature and precipitation. The start of this process was synchronous with mean sea-surface temperature changes, as recorded from the nearby SU 81-18 marine core. The strong affinity with other European late-glacial pollen sequences demonstrates that the pattern of climatic changes during the last glacial–interglacial transition was similar in both northwestern and southwestern Europe.
Late Holocene Sea Temperatures along the Central California Coast
Authors: Jones Terry L. , Kennett Douglas J. 
Published: September 2002

AbstractMussel shells from central California coastal archaeological sites record changes in sea surface temperatures in the past 2000 years. Water temperatures, inferred from oxygen isotopes in the shells, were about 1°C cooler than present and stable between 2000 and 700 yr ago. Between about 700 and 500 yr ago, seasonal variation was greater than present, with extremes above and below historic levels. Water temperatures were 2–3°C cooler than today 500–300 yr ago. The interval of variable sea temperatures 700–500 yr ago partially coincided with an interval of drought throughout central California. A coincident disruption in human settlement along the coast suggests movements of people related to declining water sources. Quantities of fish bone in central coast middens dating to this same period are high relative to other periods, and the remains of northern anchovies, a species sensitive to changing oceanographic conditions, are also abundant. The continued use of local fisheries suggests that changes in settlement and diet were influenced more by drought than by a decrease in marine productivity, as fish provided a staple during an interval of low terrestrial productivity.
Fluctuations of Outlet and Valley Glaciers in the Southern Andes (Argentina) during the Past 13,000 Years
Authors: Wenzens Gerd 
Published: September 2002

AbstractIn the southern Argentine Andes, ten advances of valley glaciers were used to reconstruct the late-glacial and Holocene glacier history. The accumulation areas of these glaciers lie in the Precordillera and are thus independent of fluctuations of the South Patagonian Icefield. Like the Viedma outlet glacier, the valley glaciers advanced three times during late-glacial time (14,000–10,000 yr B.P.). The youngest advance correlates with the Younger Dryas Stade, based on two minimum AMS14C dates of 9588 and 9482 yr B.P. The second oldest advance occurred before 11,800 yr B.P. During the first half of the Holocene, (ca. 10,000–5000 yr B.P.), advances culminated about 8500, 8000–7500, and 5800–5500 yr B.P. During the second half of the Holocene, advances occurred between ca. 4500 and 4200 yr B.P., as well as between 3600 and 3300 yr B.P. In the Rı́o Cóndor valley three subsequent advances have been identified.
Late Pleistocene Glaciation of the Southwestern Ahklun Mountains, Alaska
Authors: Briner Jason P. , Kaufman Darrell S. 
Published: September 2002

AbstractGlacial deposits in the southwestern Ahklun Mountains, southwestern Alaska, record two major glacier advances during the late Pleistocene. The Arolik Lake and Klak Creek glaciations took place during the early and late Wisconsin, respectively. During the Arolik Lake glaciation, outlet glaciers emanated from an ice cap centered over the central portion of the Ahklun Mountains and expanded beyond the present coast. During the Klak Creek glaciation, ice-cap outlet glaciers terminated ∼60 km upvalley from Arolik Lake moraines. The area also supported numerous alpine glaciers that expanded from small massifs. During both episodes of glaciation, these alpine glaciers apparently reached their maximum positions sometime after the retreat of the ice-cap outlet glaciers. Equilibrium-line altitudes for reconstructed alpine glaciers of the Klak Creek glaciation average ∼390 ± 100 m elevation in the western Ahklun Mountains, which is at most 500 m, and possibly only 200 m, below the estimated modern equilibrium-line altitude. The maximum late Pleistocene advance in the southwestern Ahklun Mountains occurred during the early Wisconsin, similar to advances elsewhere in western Alaska, but in contrast to the isotopic signal in the deep-sea record of global ice volume. The restricted extent of Klak Creek glaciers might reflect the increased distance to the Bering Sea resulting from eustatic sea-level regression and decreased evaporation resulting from lower sea-surface temperatures and increased sea-ice extent.
The Full-Glacial Forests of Central and Southeastern Europe
Authors: Willis Katherine J. , Rudner Edina , Sümegi Pal 
Published: September 2002

AbstractThe presence of trees in central and southern Europe during the last full-glaciation has long been a matter of debate. A low but persistent presence of fossil tree pollen in central and southern European full-glacial paleoecological sequences has been interpreted either as representing long-distance pollen transport from southerly refuges or as representing in situ refugial populations. Here we present macroscopic charcoal results from 31 sequences located throughout Hungary that provide unequivocal evidence for the presence of at least seven different tree types between approximately 32,500 and 16,500 14C yr B.P. This evidence is presented in conjunction with molluscan and pollen analyses to indicate that during the last full-glaciation, trees grew as far north as Hungary, probably in microenvironmentally favorable sites. These areas provided an important cold-stage refugium for the European flora and fauna.
Long-Term Temperature Trends and Tree Growth in the Taymir Region of Northern Siberia
Authors: Jacoby Gordon C. , Lovelius Nikolai V. , Shumilov Oleg I. , Raspopov Oleg M. , Karbainov Juri M. , Frank David C. 
Published: September 2002

AbstractThe northernmost conifers in the world are located well above the Arctic Circle in the Taymir region of northern Siberia and have been recording the thermal environment for centuries to millennia. The trees respond to temperatures beyond the narrow season of actual cambial cell division by means of root growth, photosynthesis, lignification of cell walls, and other biochemical processes. Data from annual tree-ring widths are used to reconstruct May–September mean temperatures for the past four centuries. These warm-season temperatures correlate with annual temperatures and indicate unusual warming in the 20th century. However, there is a loss of thermal response in ring widths since about 1970. Previously the warmer temperatures induced wider rings. Most major warming and cooling trends are in agreement with other high-latitude temperature reconstructions based on tree-ring analyses with some regional differences in timing of cooling in the late 18th century and of warming in the late 19th century.