bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lichenized Species of Omphalina (Tricholomataceae) in the Iberian Peninsula
Authors: Barrasa José María , Rico Víctor J. 
Published: September 2002

AbstractA taxonomic revision of the lichenized species of the genus Omphalina in the Iberian Peninsula is presented, based upon fungal and lichen herbarium material, as well as on fresh collections. Relevant morphological and ecological features are discussed and a diagnostic key is provided. Four lichenized species, O. ericetorum, O. hudsoniana, O. meridionalis and O. velutina are recognized. A squamulose vegetative thallus (Coriscium-type) is present only in O. hudsoniana, while the other three species form a thallus of hyphal globules (Botrydina-type). Anatomical features of the vegetative thallus cannot be used to distinguish between these last three species. Whilst O. hudsoniana is known only from the montane belt of the Eurosiberian Region and O. meridionalis seems to restricted to the Mediterranean Region, living in more or less humid sites of the Supramediterranean belt, the other two species, O. ericetorum and O. velutina, are widespread.
Early development of Hypogymnia physodes (L.) Nyl. in response to emissions from a copper smelter
Authors: Mikhailova Irina N. , Scheidegger Christoph 
Published: September 2002

AbstractThe early development of Hypogymnia physodes from soredia to the formation of stratified lobes has been studied experimentally in the vicinity of a copper-smelting plant in theMiddle Urals. SEM investigations combined with life table analyses of early developmental stages revealed decreases in soredial survival and developmental rate in polluted localities. Non-stricatified pre-thallus stages without an epicortex were tolerant to toxic impact and were able to survive even in the zone with the highest pollution (lichen desert zone). The sensitivity of developmental stagesancreased after stratified lobes had developed.
Paralethariicola aspiciliae (Ostropales, Odontotremataceae), a new genus and species of lichenicolous fungi
Authors: Calatayud V. , Etayo J. , Diederich P. 
Published: September 2002

AbstractThe generic name Paralethariicola gen. nov. is introduced for a lichenicolous fungus very similar to Lethariicola, but differing by the presence of excipular hairs, asci with a hemiamyloid apical ring and a more flattened apex, curved or slightly helicoid ascospores with ± pointed ends, and thicker paraphyses. The single species, Paralethariicola aspiciliae sp. nov., is lichenicolous on Aspicilia, and is known from continental Spain and Sardinia.
Measurement of Significant Marine Paleotemperature Variation Using Black Abalone Shells from Prehistoric Middens
Authors: Arnold Jeanne E. , Tissot Brian N. 
Published: September 2002

AbstractThe archaeological record from the last millennium in southern California indicates that a period of significant cultural change was associated with a reported marine paleoenvironmental disruption ca. 1150-1250 A.D. A lengthy warm-water anomaly may have in part precipitated more complex sociopolitical and economic responses. We develop independent verification of the perturbation (originally deduced from sediment core data) using archaeological data. Respiratory pore number allometry in the black abalone shell is known to vary clinally in modern populations in response to temperature-induced variation in rate of growth. We use developmental trajectories of abalone from dated, stratified archaeological deposits to reconstruct prehistoric seawater temperatures.
Vegetation Response to Upper Pliocene Glacial/Interglacial Cyclicity in the Central Mediterranean
Authors: Combourieu-Nebout Nathalie 
Published: September 2002

AbstractNew detailed pollen analysis of the lower part of the Upper Pliocene Semaforo section (Crotone, Italy) documents cyclic behavior of vegetation at the beginning of the Northern Hemisphere glaciations. The competition between four vegetation units (subtropical humid forest, deciduous temperate forest, altitudinal coniferous forest, and open xeric assemblage) probably reflects modifications of vegetation belts at this montane site. Several increases in herbaceous open vegetation regularly alternate with subtropical humid forest, which expresses rapid climatic oscillations. The complete temporal succession—deciduous forest (rich inQuercus), followed by subtropical humid forest (Taxodiaceae andCathaya), then altitudinal coniferous forest (Tsuga, Cedrus, Abies,andPicea), and finally herbaceous open vegetation (Graminae, Compositae, andArtemisia)—displays the climatic evolution from warm and humid interglaciation to cold and dry glaciation. It also suggests an independent variation of temperature and humidity, the two main climatic parameters. The vegetation history of southern Calabria recorded in the Semaforo section have been correlated with the ∂18O signal established in the Atlantic Ocean.
Late Quaternary Vegetation and Climate Changes in Central Texas Based on the Isotopic Composition of Organic Carbon
Authors: Nordt Lee C. , Boutton Thomas W. , Hallmark Charles T. , Waters Michael R. 
Published: September 2002

AbstractStable carbon isotope analysis of organic carbon in alluvial deposits and soils of three streams in central Texas reveals significant shifts in the ratio of C3 to C4 plant biomass production during the past 15,000 yr. These temporal changes in vegetation appear to be in response to changes in climate. During the late Pleistocene, C4 plants comprised only about 45 to 50% of the vegetative biomass in this area, suggesting that conditions were cooler and wetter than at any time during the past 15,000 yr. The time between 11,000 and 8000 yr B.P. is interpreted as transitional between late Pleistocene conditions and warmer and drier Holocene conditions based on a slight increase in the abundance of C4 plant biomass. During the middle Holocene, between approximately 6000 and 5000 yr B.P., mixed C3/C4 plant communities were replaced almost completely by C4-dominated communities, indicating prairie expansion and warmer and drier climatic conditions. By 4000 yr B.P., the abundance of C4 plant biomass decreased to levels similar to the early Holocene transitional period, suggesting a return to cooler and wetter climatic conditions. No significant shift in the ratio of C3 to C4 productivity has occurred during the last 4000 yr, except for a slight increase in the abundance of C4 plant biomass around 2000 yr B.P. The results of this investigation correlate well with other regional late Quaternary climatic interpretations for central and north Texas, the Southern Plains region, and with other portions of the Great Plains.
Radiocarbon Evidence for Rates of Lateral Expansion in Raised Mires in Southern Finland
Authors: Korhola Atte A. 
Published: September 2002

AbstractRadiocarbon ages from the bottom peat deposits and detailed morphometric measurements at five peatlands in the boreal region of southern Finland were used to reconstruct the Holocene patterns of raised mire development. The results suggest that the areal expansion of the mires has been extremely rapid at times—up to several hundreds hectares per millennium—but the periods of more rapid expansion were not coincident among the mires. The rate of lateral extension was shown to depend mainly on the topography of the mineral substrate. Horizontal expansion did not always correlate with vertical growth. Mires expanded slowly between ca. 6000 and 4000 yr B.P., probably as a consequence of drier climatic conditions at that time. The mires also expanded slowly during the two to three recent millennia, the reason for this most probably lying in steepening of the bottom gradient toward the marginal areas of the present mires, The results point to a substantial measure of local environmental control over the lateral extension in raised mire ecosystems.
Lake Evolution in the Tengger Desert, Northwestern China, during the Last 40,000 Years
Authors: Pachur Hans-Joachim , Wünnemann Bernd , Zhang Hucai 
Published: September 2002

AbstractClimatic changes inferred from lacustrine deposits and lake-level fluctuations in northwestern and central China are mainly based on paleoclimatic records from the Tibetan Plateau, while there is still a lack of data relating to the semiarid/arid desert regions of Inner Mongolia. In the Tengger Desert, different paleolake levels at Baijian Hu are documented by six paleoshorelines and stratified lake carbonates. The highest lake level occurred ca. 39,000 14C yr B.P. and prevailed over about 16,000 km2. From sediment structure, geochemical composition, and ostracods we infer humid/cool conditions until 23,000 14C yr B.P. In the northern Badanjilin Desert at Gaxan Nur/Sogu Nur, high lake levels can be deduced from mollusc-bearing paleobeaches and lake carbonates, which have been dated to 34,000 14C yr B.P. and indicate a lake that covered some 32,000 km2. After ca. 20,000 yr B.P. the climate became dry with increased eolian activity and decreasing lake levels. Reestablishment of wet conditions occurred ca. 13,000 yr B.P. The Holocene is represented by stratified lake deposits that alternate with fluvial and eolian deposits, indicating a longterm oscillating trend toward arid conditions. The existence of widespread freshwater lakes during the late Pleistocene indicates a semihumid climate without an accompanying fall in temperature to arctic conditions.
Late Holocene Coastal Plain Stratigraphy and Sea-Level History at Hanalei, Kauai, Hawaiian Islands
Authors: Calhoun R. Scott , Fletcher Charles H. 
Published: September 2002

AbstractFluvial, marine, and mixed fluvial-marine deposition on the coastal plain of Hanalei Bay on the north shore of Kauai, Hawaii, records a middle- to late-Holocene fall of relative sea level. Radiocarbon dating of the regression boundary preserved in the stratigraphy of the coastal plain documents a seaward shift of the shoreline beginning at least 4800–4580 cal yr B.P. and continuing until at least 2160–1940 cal yr B.P. Marine sands stranded in the backshore and coastal plain environment are buried by fluvial floodplain and channel sands, silts, and muds. In places, erosion at the regression contact exposed older marine sands thus increasing the hiatus at the regression disconformity. The shoreline regression is best explained as the result of a fall in relative sea level. The age and elevation of the cored regression boundary at sites that have not been influenced by erosion are consistent with a middle- to late-Holocene highstand of relative sea level as predicted by geophysical models of whole Earth deformation related to deglaciation.
Ochotona (Lagomorpha) from Late Quaternary Cave Deposits in Eastern North America
Authors: Mead Jim I. , Grady Frederick 
Published: September 2002

AbstractPikas (Ochtona)—small gnawing mammals, related to rabbits—range today throughout parts of the Northern Hemisphere, but had a wider distribution during the Pleistocene. Nine caves from northeastern North America (a region not occupied by pikas today) have Pleistocene deposits containing remains of Ochotona. We examine 526 fossil specimens (ranging in age from approximately 850,000 to 8670 yr B.P.) from five of these caves. Two morphological forms of Ochotona lived in northeastern North America during the late Pleistocene—a large species (probably O. whartoni) and a small species (probably O. princeps).Ochotona of glacial age are not necessarily indicative of talus slopes and mesic communities. O. princeps-like of the Irvingtonian of West Virginia were living with an amphibian-reptilian assemblage found in the area today, implying winters not much, if at all, colder than at present. Late glacial and postglacial change in climate south of the ice sheets in effect would have isolated Ochotona in eastern North America, where they were unable to retreat to the west or north. Whereas western pika had the option of moving up in elevation, into boreal islands, eastern forms became restricted to ever-diminishing habitats, culminating in extinction and extirpation. Radiocarbon ages imply that Ochotona lived in eastern North America during the late Pleistocene (late Rancholabrean) and into the earliest Holocene. We describe the youngest remains of Ochotona in eastern North America and the youngest for the extinct large form, O. whartoni.
Sediment Characterization and Porewater Isotope Chemistry of Quaternary Deposits from the St. Clair Delta, Ontario, Canada
Authors: Cumming John D. , Al-Aasm Ihsan S. 
Published: September 2002

AbstractWalpole Island is part of a large freshwater delta located at the St. Clair River mouth in southwestern Ontario. Quaternary deposits on the island consist of Lake Nipissing to Lake St. Clair stage deltaic sediments underlain by a thick sequence of Late Wisconsin glaciolacustrine rhythmites and massive clayey till. These sediments overlie a thin freshwater aquifer resting on Paleozoic bedrock. Porewater δ18O, δD, and δ13CDICprofiles of cores taken from northern and central Walpole Island show that older (>10,000 yr B.P.), deeper glaciogenic porewaters have mixed with, and have been displaced by, younger modern surficial water. In contrast, isotopic profiles from a core taken from southern Walpole Island indicate that modern St. Clair River waters have penetrated the entire 20-m core via fractures, effectively displacing all glaciogenic porewater. Fracturing and faulting are clearly visible throughout the southern core, and their presence may be attributed to its location on the trend of the Electric Fault. These features are interpreted as the product of renewed Holocene fault movement. Porewater Na+, K+, Ca2+, and Mg2+concentration gradients are consistent with the presence of upwardly diffusing deep brine, for which the Electric Fault may serve as a conduit.
Folsom Drought and Episodic Drying on the Southern High Plains from 10,900–10,20014C yr B.P
Authors: Holliday Vance T. 
Published: September 2002

AbstractThe paleoenvironments of late Pleistocene and early Holocene time on the Southern High Plains have been studied for decades, but regionally extensive or long-term, easily recoverable proxy climate indicators are difficult to find. The stratigraphy of valley fill and upland eolian deposits and stable-carbon isotope data, in addition to geographically limited paleontological data, now provide clues to the environment during this time, which includes the earliest, or Paleoindian period (∼11,200–800014C yr B.P.) of human occupation. During the Clovis occupation (∼11,200–10,90014C yr B.P.), valleys contained perennial streams. This was followed in Folsom time (10,900–10,20014C yr B.P.) by an abrupt change to lakes and ponds (with water levels fluctuating between several meters depth and no surface water) and marshes and accumulation of sheet sands on uplands, starting the earliest phase of construction of the regional dune fields. These changing conditions indicate a shift from relatively wetter to relatively drier conditions with episodic drought. Stable-C isotopes further indicate that warming characterized the Clovis–Folsom transition. During the rest of the Paleoindian period the environment was relatively cool but fluctuated between wetter and drier conditions with an overall trend toward drying that resulted in further enlargement of the dune fields and culminated in the warm, dry Altithermal beginning ∼800014C yr B.P. Clovis time probably was the wettest of any Paleoindian period in terms of runoff and spring discharge. The Folsom period was drier and was the earliest episode of regional wind erosion and eolian deposition and may have been the warmest of Paleoindian times. Evidence of a previously hypothesized “Clovis drought” in this region is sparse.
Origin of Eolian Sand Mobilization during the Past 2300 Years in the Mu Us Desert, China
Authors: Sun Jimin 
Published: September 2002

AbstractEolian sand dunes and sand sheets are extensive in the semiarid regions of northern-central China. Previous studies indicated that these eolian sands mainly formed during historical times. However, the sand sources and their reworking processes have not been well studied, and even the reasons for their occurrence are still controversial. Field investigation and sedimentary evidence indicate that both the inner Mu Us Desert and its southern marginal region, both sources of modern eolian sand, are largely associated with reworking of sands of the last glaciation. Based on geological, documentary, and archaeological data, three phases of land cultivation during the past 2300 years, together with historical droughts, high wind energy, and the easily reworked sand sources, largely account for the occurrence of active sand dunes and sand sheets in the Mu Us Desert.
Late- and Postglacial Sea-Level Change and Paleoenvironments in the Oder Estuary, Southern Baltic Sea
Authors: Müller Anne 
Published: September 2002

AbstractKnowledge of sea-level change in the southern Baltic Sea region is important for understanding the variations in late Pleistocene and Holocene sea-level change across northern Europe. These variations are a consequence of the response of the Earth's crust to the deglaciation of Fennoscandia and of the water added to the oceans from the melting of all Pleistocene ice sheets. The sedimentological and geochemical composition of five sediment cores from the lagoonal Oder Estuary offers new observational evidence for sea-level change and coastal development in the southern Baltic Sea region. The combined use of several geochemical proxies (organic carbon, nitrogen, calcium carbonate and biogenic opal contents, Corg/S and Corg/N ratios, δ13C values of organic matter, and δ15N values) is a new approach for the study area. The chemical evidence of this multiproxy approach allows clear identification of several stages in the development of the lagoonal environment: postglacial lake stages with sandy sedimentation during the Older Dryas and the Allerød stades, lacustrine phases with high autochthonous productivity during the Atlantic stade, terrestrial stages with peat formation at the beginning of the Subboreal stade, sedimentation as a result of marine transgression, and brackish sedimentation after the formation of sand spits and barrier islands during the Subatlantic stade. The stages are the result of regional sea-level change owing to complex shoreline development. They support the tentative sea-level curve proposed nearly 20 years ago for the region. In addition, changes in Oder River input in response to climate conditions is monitored. Whereas high terrigenous input of organic matter from the Oder River occurred during periods of humid climate during the Allerød, Atlantic, and Subatlantic stades, Oder River discharge decreased with drier and cooler climate conditions during the Subboreal stade. Furthermore, the geochemical evidence points to local anomalies such as the significance of river input and additional sulfate supply into the Oder lagoon for the composition of the sediments. Overall, the results provide a framework for future studies, which would allow for a more detailed comparison with other, similar environments.
Paleovegetation Simulations of Lowland Amazonia and Implications for Neotropical Allopatry and Speciation
Authors: Cowling Sharon A. , Maslin Mark A. , Sykes Martin T. 
Published: September 2002

AbstractPaleovegetation modeling simulations of the lowland Amazon basin were made to assess the relative importance of glacial climate and atmospheric CO2 for altering vegetation type and structure, as well as to explore the potential physiological mechanisms underlying these ecosystem-level responses. Modeling results support the view that widespread invasion of grasslands into the Amazon lowlands during the last glaciation was not likely. Glacial cooling was probably responsible for maintaining glacial forest cover via its effects in reducing photorespiration and decreasing evapotranspiration, which collectively improve plant carbon and water relations. Modeling results confirm that leaf area index (LAI), a common proxy for canopy density, is highly sensitive to independent and interactive changes in climate and low concentration of atmospheric CO2, and the results show considerable region-to-region variation during the last glaciation. Heterogeneous variations in glacial vegetation LAI may have promoted allopatric speciation by geographically isolating species (called vicariance) in the forest (sub)canopy. The proposed vicariance hypothesis incorporating spatial variations in canopy density conforms to many of the essential tenets addressed by previous neotropical speciation models, but also helps to overcome some of their inconsistencies.
Paleoecology and Geochronology of Uruguayan Coastal Marine Pleistocene Deposits
Authors: Martı́nez Sergio , Ubilla Martı́n , Verde Mariano , Perea Daniel , Rojas Alejandra , Guérèquiz Rosario , Piñeiro Graciela 
Published: September 2002

AbstractMinimum radiocarbon ages of marine Pleistocene molluscs from Uruguay range from 29,500±600 to 35,500±1900 14C yr B.P. Because knowledge of the marine Quaternary stratigraphy of Uruguay remains inadequate, no attempt is made to correlate between these deposits and recognized lithostratigraphic units. Analysis of the temperature and salinity ranges of the various molluscs suggests the establishment of a poly-euhaline fauna that inhabited waters warmer than present at the same latitude. This is supported by a northward retreat in the recent distribution of Chrysallida cf. C. gemmulosa, Nioche subrostrata, and probably Anomalocardia brasiliana. These marine Pleistocene deposits can probably be correlated with the last interglaciation (oxygen-isotopic substage 5e). At that time the fluvial-marine front of the Rio de la Plata was displaced much further northwestward than previously supposed. Chrysallida cf. C. gemmulosa and Limaria sp. are recorded in Uruguayan Quaternary deposits for the first time.
Dependence of Near-Surface Magnetic Susceptibility on Dust Accumulation Rate and Precipitation on the Chinese Loess Plateau
Authors: Porter Stephen C. , Hallet Bernard , Wu Xihao , An Zhisheng 
Published: September 2002

AbstractMagnetic susceptibility (MS) of surface sediment varies systematically across the Loess Plateau in central China, decreasing exponentially from >200×10−8 m3/kg at the northern margin of the Qinling Shan to ≤30×10−8 m3/kg near the southern margin of the Mu Us Desert. MS correlates highly with loess median grain size (r2=0.79), which decreases south-southeastward across the plateau. It also correlates with mean annual temperature (MAT) and mean annual precipitation (MAP) (r2=0.58 and 0.60, respectively), and with their product MAT×MAP (r2=0.83), which is considered a measure of potential pedogenic activity. Because regional isopleths depicting grain size and the primary meteorological parameters are nearly parallel, it is difficult to determine their relative influence on MS. A simple MS model, based on the observed spatial variation in loess thickness, permits quantitative assessment of the effect of the dust accumulation rate on the MS signal of surface sediment and isolates the likely role of climate in the production of magnetic minerals. The model suggests that 84% of the loess MS variance is dictated by the diluting effect of dust and 10–11% is associated with meteorological factors, primarily precipitation. The observed and modeled relationships support hypotheses that attribute variations in MS in the loess-paleosol succession to varying rates of dust deposition and in situ production of magnetic minerals in the accretionary soils, both of which are controlled by monsoon climate.