bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long-Term Monitoring in the Netherlands Suggests that Lichens Respond to Global Warming
Authors: Herk C. M. van , Aptroot A. , Dobben H. F. van 
Published: September 2002

AbstractThere is evidence to suggest that part of the recent changes in the lichen flora of the Netherlands is attributable to an increase in temperature. Changes which have occurred over the last 22 years were studied in detail, and were subjected to a statistical treatment by comparing the change of species to their latitudinal distribution and to ecological determinants.All 329 epiphytic and terrestrial lichen species occurring in the Netherlands were considered in relation to their world distribution. Arctic-alpine/boreo-montane species appear to be declining, while (sub)tropical species are invading. The proportion of increasing species is by far the largest among the wide-tropical lichens (83%), and smallest among the arctic-alpine/boreo-montane lichens (14%). None of the wide-tropical species was found to decrease, while 50% of the arctic-alpine/boreomontane species show a decline.Long-term monitoring of the epiphytic lichen flora in the province of Utrecht from 1979 onwards shows that the total number of taxa present increased from 95 in 1979 to 172 in 2001, while the average number of taxa per site increased from 7·5 to 18·9. The rate of increase was greatest by far between 1989 and 1995. The majority of the species (152 taxa or 85%) show a gross increase, only 17 species (10%) show a decrease.A detailed analysis of these data using multiple regression suggests global warming as an additional cause for recent changes, next to decreasing SO⊂2 and increasing NH⊂3. Changes appear to be correlated initially (1979-1995) only with toxitolerance and nutrient demand. Changes between 1995 and 2001, however, appear positively correlated to both temperature and nutrient demand, indicating a recent and significant shift towards species preferring warm circumstances, independent from, and concurrent with changes due to nutrient availability.This is the first paper reporting long-term floristic changes for lichens that appear to be correlated significantly with increasing temperatures. We suggest that future lichen monitoring programmes also pay attention to effects of climatic change, instead of focusing on air pollution effects only.
New Species of the Lichen Family Thelotremataceae in SE Asia
Authors: Homchantara N. , Coppins B. J. 
Published: September 2002

AbstractThe lichen family Thelotremataceae was studied in Thailand and Malaysia (including one specimen from Indonesia). Of the 30 new species recognized, 26 are recorded from Thailand: Myriotrema grandisporum, M. khaoyaianum, M. khuntanense, M. rongklaense, M. subanamaliense, M. subgranulosum, M. subminutum, M. thailandicum, M. whalleyanum, Ocellularia brunneospora, O. diospyrosis, O. flavescens, O. inthanonensis, O. kansriae, O. krathingensis, O. melanophthalma, O. neoleucina, O. peremergens, O. pluriporoides, O. rhicnoporoides, O. subleucina, O. wolseleyana, Thelotrema laemense, T. mongkolsukii, T. phliuense and T. rhododiscum; and 4 from Sarawak: M. coppinsii, M. muluense, O. neoperforata, and O. roseotecta.Additional notes are provided on Ocellularia palaeoamplior Aptroot & Sipman and Thelotrema isidiophorum (Kremp.) Zahlbr.
Chronology of Taylor Glacier Advances in Arena Valley, Antarctica, Using in Situ Cosmogenic 3He and 10Be
Authors: Brook Edward J. , Kurz Mark D. , Ackert Robert P. , Denton George H. , Brown Erik T. , Raisbeck Grant M. , Yiou Francoise 
Published: September 2002

AbstractIn situ produced cosmogenic nuclides provide a new technique for constraining exposure ages of glacial deposits. In situ3He and 10Be in quartz sandstone boulders from Arena Valley, southern Victoria Land, Antarctica, provide chronological constraints for a sequence of moraines ("Taylor II-IVb" moraines) related to expansions of Taylor Glacier and the East Antarctic Ice Sheet. Mean 3He ages are 113,000 ± 45,000 yr, 208,000 ± 67,000 yr, 335,000 ± 187,000 yr, and 1.2 ± 0.2 myr, for Taylor II,III,IVa, and IVb moraines, respectively (mean ± 1σ). Corresponding mean 10Be ages for Taylor II and IVb moraines are 117,000 ± 51,000 yr and 2.1 ± 0.1 myr. For the older deposits the 3He ages are probably lower limits due to diffusive loss. Although the exposure ages appear consistent with the few previous age estimates, particularly with an isotope stage 5 age for Taylor II, each moraine exhibits a broad age distribution. The distribution probably results from a variety of factors, which may include prior exposure to cosmic rays, 3He loss, erosion, postdepositional boulder movement, and radiogenic production of 3He. Nonetheless, the exposure ages provide direct chronological constraints for the moraine sequence, and suggest a maximum thickening of Taylor Glacier relative to the present ice surface of ∼500 m since the late Pliocene-early Pleistocene.
Factors Affecting14C Ages of Lacustrine Carbonates: Timing and Duration of the Last Highstand Lake in the Lahontan Basin
Authors: Benson Larry 
Published: September 2002

AbstractTwo processes contribute to inaccurate14C age estimates of carbonates precipitated within the Lahontan basin, NevadaCalifornia: low initial14C/C ratios in lake water (reservoir effect) and addition of modern carbon to calcium carbonate after its precipitation. The mast reliable set of14C ages on carbonates from elevations > 1310 m in the Pyramid and Walker Lake subbasins indicate that lakes in all seven Lahontan subbasins coalesced ∼14,20014C yr B.P. forming Lake Lahontan. Lake Lahontan achieved its 1330-m highstand elevation by ∼13,80014C yr B.P. and receded to 1310 m by ∼13,70014C yr B.P. Calculations, based on measured carbonate-accumulation rates, of the amount of time Lake Lahontan exceeded 1310 and 1330 m (500 and 50 yr) are consistent with this chronology. The timing of the Lake Lahontan highstand is of interest because of the linkage of highstand climates with proximity to the polar jet stream. The brevity of the Lahontan highstand is interpreted to indicate that the core of the southern branch of the polar jet stream remained only briefly over the Lahontan basin.
Lake Evolution during the Last 3000 Years in China and Its Implications for Environmental Change
Authors: Fang Jin-Qi 
Published: September 2002

AbstractTaking China as a whole, lake expansion occurred 500 B.C. (?)-0 A.D., 650-950 A.D., and 1250-1650 A.D. over the past 3000 yr. The expansions were mainly due to climatic fluctuations and correspond to frequent flood reports. Three regional characteristics of lake development have been recognized. (1) Fluctuations of near-coastal lakes, and those in other regions as well, were out of phase during 500 B.C.-500 A.D., which possibly resulted from out-of-phase fluctuations of climate and sea level on 10- to 100-yr time scale. (2) As the lower Yellow River channel migrated southward, the lakes in the south of the North China Plain formed and reached their largest sizes much later than those in the north. (3) For the lakes in the middle and lower Yangtze River valley, the higher a lake basin lies above a neighboring river and the further the lake is from the river's mouth, in general, the younger the lake is. Through land reclamation, the ancient Chinese have changed most of the lakes greatly. However, human activities were also constrained in certain ways by the natural changes of the lakes. Reclamation usually was banned and farmland was abandoned to repair reservoirs while lakes were expanding.
A 1000-Year Record of Temperature and Precipitation in the Sierra Nevada
Authors: Graumlich Lisa J. 
Published: September 2002

AbstractTree-ring data from subalpine conifers in the southern Sierra Nevada were used to reconstruct temperature and precipitation back to A.D. 800. Tree growth of foxtail pine (Pinus balfouriana) and western juniper (Juniperus occidentalis ssp. australis) is influenced by nonlinear interactions between summer temperature and winter precipitation. Reconstruction of the separate histories of temperature and precipitation is feasible by explicitly modeling species and site differences in climatic response using response surfaces. The summer temperature reconstruction shows fluctuations on centennial and longer time scales including a period with temperatures exceeding late 20th-century values from ca. 1100 to 1375 A.D., corresponding to the Medieval Warm Period identified in other proxy data sources, and a period of cold temperatures from ca. 1450 to 1850, corresponding to the Little Ice Age. Precipitation variation is dominated by shorter period, decadal-scale oscillations. The long-term record presented here indicates that the 20th century is anomalous with respect to precipitation variation. A tabulation of 20- and 50-yr means indicates that precipitation equaling or exceeding 20th-century levels occurred infrequently in the 1000+-yr record.
AMS Radiocarbon Age of the Upper Mississippi Valley Roxana Silt
Authors: Leigh David S. , Knox James C. 
Published: September 2002

AbstractAccelerator mass spectrometer radiocarbon ages of the Roxana Silt (loess) along the Upper Mississippi Valley of Wisconsin and Minnesota indicate that loess sedimentation of the Roxana Silt occurred between about 55,000 and 27,000 14 C yr B.P. However, due to local environmental controls, the basal age at any given site may range from 55,000 to 35,000 14C yr B.P. The radiocarbon ages presented here are in agreement with previous radiocarbon ages for the Roxana Silt in its type area of west-central Illinois, but indicate that long-term sedimentation rates along the bluffline of the Upper Mississippi Valley were very slow (4-8 cm/1000 yr) compared to long-term sedimentation rates along the bluffline of the type area (40-70 cm/1000 yr). Comparison of radiocarbon ages for midcontinent middle Wisconsinan loess deposits indicates that sedimentation along the Mississippi River valley may have preceded loess sedimentation along the Missouri River valley by as much as 20,000 yr or that basal ages for middle Wisconsinan loess along the Missouri Valley are erroneously young. The bracketing ages for the Upper Mississippi Valley Roxana Silt indicate that the Mississippi River valley was receiving outwash sedimentation between 55,000 and 27,000 14C yr B.P.
Macrofossil and Tree-Ring Evidence for a Long-Term Forest Succession and Mid-Holocene Hemlock Decline
Authors: Filion Louise , Quinty François 
Published: September 2002

AbstractPaludified dune fields in southern Québec provided a unique opportunity to analyze a mid-Holocene forest succession, ranging from xero-mesophilous forests to treed peatlands, which registered the hemlock decline, a major biostratigraphic event in eastern North America. Our fossil-tree chronology established from 66 radiocarbon dates of tree stems indicates that white pine and hemlock were present at the study site about 6000-5700 yr B.P. Hemlock reached a maximum 4900-4800 yr B.P. and then declined between 4600 and 3800 yr B.P.; the species recovered around 3700 yr B.P. and then decreased when white pine and eastern latch dominated the site after 3000 yr B.P. and between 2600 and 2200 yr B.P., respectively. Tree-ring signatures of fossil hemlocks suggest the continuous influence of biotic factors, possibly insect defoliators, throughout the record, as shown by recurrent suppressed-growth pattern. Microscopic examination of the hemlock fossil stems disclosed no evidence of fungal disease. The hemlock decline was probably caused by regional posthypsithermal climatic changes, toward moister conditions.
Postglacial Vegetation and Fire History in the Chirripó Páramo of Costa Rica
Authors: Horn Sally P. 
Published: September 2002

AbstractPollen and charcoal analysis of a 5.6-m sediment core from Lago de las Morrenas (9°29′N, 83°29′W; 3480 m) provides evidence of postglacial vegetation and fire history in the highlands of the Cordillera de Talamanca, Costa Rica. The site is presently surrounded by treeless páramo vegetation and apparently has been so since deglaciation about 10,000 yr B.P. Pollen spectra suggest no pronounced changes in vegetation since ice retreat. Fires set by people or lightning have burned the páramo repeatedly, with fire activity probably highest during the late Holocene, but these fires have not carved páramo from forest. Pollen percentages for Gramineae and other páramo taxa decline upward, whereas percentages for certain subalpine, lower montane, and lowland forest taxa increase slightly; these changes may reflect the impact of prehistoric human activity or slight upslope migrations of forest taxa owing to climatic warming. There is no clear evidence of higher timberlines during the mid-Holocene.
Late Quaternary Pollen Record from Cheyenne Bottoms, Kansas
Authors: Fredlund Glen G. 
Published: September 2002

AbstractA sediment and pollen record from Cheyenne Bottoms, a large (166 km2) enclosed basin in central Kansas, provides evidence for local and regional vegetation and climate change during the late Quaternary (ca. 30,000 yr.). Although radiocarbon dating of the carbonate-rich lacustrine sediments remains problematic, a basic chronological framework for the section is established. Two major litho- and biostratigraphic units, a Farmdalian zone (ca. 30,000 to 24,000 yr B.P.) and a Holocene zone (ca. 11,000 yr B.P. to present), are separated by a major unconformity spanning the Woodfordian (ca. 24,000 to 11,000 yr B.P.). Pollen and sedimentary data indicate a period of basin-wide drying preceding this unconformity. The sustained absence of sediment accumulation within this playa-like basin suggests that early Woodfordian conditions were increasingly arid with strengthened surface winds. Before this, persistent shallow water marshland dominated the local basin-bottom vegetation. Regional upland vegetation was an open grassland-sage steppe throughout the Farmdalian with limited populations of spruce, juniper, aspen, birch, and boxelder in riparian settings and escarpments. Throughout the Holocene, water levels within the basin fluctuated. Changes in wetland vegetation resulting from water level fluctuation have increased during the last 3,000 yr indicating that periodic episodes of wetland loss and rebound are not unique to postsettlement conditions but are an ongoing phenomenon at Cheyenne Bottoms.
Chironomid Evidence for Late-Glacial Climatic Reversals in Maine
Authors: Cwynar Les C. , Levesque André J. 
Published: September 2002

AbstractPreviously published pollen studies from Maine have not identified any late-glacial reversals despite evidence for them from adjacent areas. The distribution and abundance of midge flies are strongly correlated with summer surface-water temperatures. We analyzed fossils of larval midge flies from the sediments of two ponds (Trout and Tilley) from Maine. Each site reveals a major and a minor oscillation during which inferred summer surface-water temperatures fell by 7-13°C and 2.1-2.6°C, respectively. We tentatively correlate these events with the Younger Dryas cooling and Killarney Oscillation reported from adjacent Maritime Canada, where they have been AMS14C-dated at 10,770-10,000 and 11,160-10,910 yr B.P., respectively. A third oscillation occurs at the northernmost site, Tilley Pond, and may represent the effects of a local ice advance in northern Maine.
Lake Michigan Beach-Ridge and Dune Development, Lake Level, and Variability in Regional Water Balance
Authors: Lichter John 
Published: September 2002

AbstractA sequence of northern Lake Michigan beach ridges records lake-level fluctuations that are probably related to changes in late Holocene climate. Historically, episodes of falling and low lake level associated with regional drought led to the formation of dune-capped beach ridges. The timing of prehistoric ridge formation, estimated by radiocarbon dating of plant macrofossils from early-successional dune species, shows that return periods of inferred drought, averaged for time intervals of 100 to 480 yr, ranged between 17 and 135 yr per drought during the last 2400 yr. In five of ten of these time intervals, the average return period ranged between 17 and 22 yr per drought. These intervals of frequent ridge formation and drought were associated with the development of parabolic dunes, which is indicative of high lake level and moist climate. This seeming paradox suggests that unusually moist decades alternated with unusually dry decades during these time intervals. Regional water balance probably varied less during the time intervals when ridges formed less often and the lake produced no evidence of high level.
High-Resolution Marine Record of Climatic Change in Mid-latitude Chile during the Last 28,000 Years Based on Terrigenous Sediment Parameters
Authors: Lamy Frank , Hebbeln Dierk , Wefer Gerold 
Published: September 2002

AbstractMarine sediment cores from the continental slope off mid-latitude Chile (33°S) were studied with regard to grain-size distributions and clay mineral composition. The data provide a 28,000-yr14C accelerator mass spectrometry-dated record of variations in the terrigenous sediment supply reflecting modifications of weathering conditions and sediment source areas in the continental hinterland. These variations can be interpreted in terms of the paleoclimatic evolution of mid-latitude Chile and are compared to existing terrestrial records. Glacial climates (28,000–18,000 cal yr B.P.) were generally cold–humid with a cold–semiarid interval between 26,000 and 22,000 cal yr B.P. The deglaciation was characterized by a trend toward more arid conditions. During the middle Holocene (8000–4000 cal yr B.P.), comparatively stable climatic conditions prevailed with increased aridity in the Coastal Range. The late Holocene (4000–0 cal yr B.P.) was marked by more variable paleoclimates with generally more humid conditions. Variations of rainfall in mid-latitude Chile are most likely controlled by shifts of the latitudinal position of the Southern Westerlies. Compared to the Holocene, the southern westerly wind belt was located significantly farther north during the last glacial maximum. Less important variations of the latitudinal position of the Southern Westerlies also occurred on shorter time scales.
Late Quaternary Geology and Geochronology of Diring Yuriakh, An Early Paleolithic Site in Central Siberia
Authors: Waters Michael R. , Forman Steven L. , Pierson James M. 
Published: September 2002

AbstractDiring Yuriakh, an archaeological site on the highest terrace of the Lena River in subarctic eastern Siberia, provides evidence for the oldest and northern-most Early Paleolithic occupation in Asia. Stratigraphic and sedimentological studies at the site show that artifacts occur on a single eolian deflation surface that is underlain by fluvial sediments with inset cryogenic sand wedges and overlain by eolian deposits. Thermoluminescence ages on the fine-grained extracts from the eolian sediments and sand wedges that bound the artifact level indicate that the occupation occurred >260,000 yr B.P. and may possibly date between 270,000 and 370,000 yr B.P. This study documents that the artifacts from Diring Yuriakh are an order of magnitude older than artifacts from any previously reported site from Siberia. The antiquity and subarctic location of Diring Yuriakh indicates that people developed a subsistence strategy capable of surviving rigorous conditions in Siberia by ≥260,000 yr B.P.
Implications for the Dating of Wisconsinan (Weichselian) Late-Glacial Events of Systematic Radiocarbon Age Differences between Terrestrial Plant Macrofossils from a Site in SW Ireland
Authors: Turney Chris S.M. , Coope G. Russell , Harkness Doug D. , Lowe J. John , Walker Michael J.C. 
Published: September 2002

AbstractAMS radiocarbon dates were obtained from Salix herbacea leaves, Carex seeds, and bulk organic detritus from a lake sediment profile of Wisconsinan (Weichselian) Lateglacial age in SW Ireland. There is a systematic age difference between the dated series from the two types of macrofossils, with ages obtained from Salix herbacea leaves being 900 to 1500 14C years younger than those obtained from Carex seeds. The latter tend to be more in accord with dates from the total organic detritus in the lake sediment, although the bulk organic fraction invariably registered the older ages. Intact survival of the fragile Salix leaves indicates that they are unlikely to have been physically transferred within the sediment matrix and/or otherwise reworked from the surrounding catchment. Hence, these macrofossils are the more likely to be contemporaneous with the time of deposition. However, there is no significant correlation between measured 14C age and depth in the Salix values, which scatter over a range of 700 14C years. In contrast, the age/depth relationship for Carex shows a significant reversal, possibly reflecting the redeposition of these macrofossils, and therefore giving radiocarbon ages that are anomalously old. The data have important implications for the dating of lake sediment sequences by AMS radiocarbon measurement of terrestrial plant macrofossils.
Late Pleistocene Climates of Beringia, Based on Analysis of Fossil Beetles
Authors: Elias Scott A. 
Published: September 2002

AbstractThirty-one fossil beetle assemblages from central and eastern Beringia (Alaska, the Yukon Territory, and the now-submerged Bering Land Bridge) have yielded seasonal temperature estimates for the interval 43,550–9250 14C yr before present (yr B.P.). Estimates of the mean temperature of the warmest (TMAX) and coldest (TMIN) months were derived by the Mutual Climatic Range method. Assemblages from northern and western sites show a mid-Wisconsin interstadial TMAX warming from 35,000–30,000 yr B.P.; this warming is less pronounced in assemblages for interior regions. There is little or no beetle evidence for the spread of coniferous forest in eastern Beringia during this interstade, except for in parts of the Yukon Territory. During the last glacial maximum TMAX values were depressed by about 2°–2.5°C in Arctic regions of Beringia, and by about 4°C in the interior; TMIN values were about 8°C colder in both regions. TMAX and TMIN values rose rapidly at northern sites after 12,000 yr B.P. Seasonal temperatures peaked at 11,000 yr B.P., just as the Bering Land Bridge was inundated. This was followed by a sharp climatic cooling between 11,000 and 10,000 yr B.P., the equivalent of a Younger Dryas cooling in eastern Beringia.
Sharp Decrease in Summer Monsoon Strength 4000–3500 cal yr B.P. in the Central Higher Himalaya of India Based on Pollen Evidence from Alpine Peat
Authors: Phadtare Netajirao R. 
Published: September 2002

AbstractAge-constrained pollen data and magnetic susceptibility of an alpine peat profile from the Garhwal Higher Himalaya display a continuous record of climate and monsoon trends for the past 7800 yr. About 7800 cal yr B.P., dominance of evergreen oak (Quercus semecarpifolia), alder (Alnus), and grasses in the pollen record reflect a cold, wet climate with moderate monsoon precipitation. From 7800 to 5000 cal yr B.P., vegetation was progressively dominated by conifers, indicating ameliorated climate with a stronger monsoon. A warm, humid climate, with highest monsoon intensity, from 6000–4500 cal yr B.P. represents the mid-Holocene climatic optimum. Between 4000 and 3500 cal yr B.P., the abundance of conifers sharply decreased, with the greatest increase in evergreen oak. This trend suggests progressive cooling, with a decrease in the monsoon to its minimum about 3500 cal yr B.P. Two relatively minor cold/dry events at ca. 3000 and 2000 cal yr B.P. marked step-wise strengthening of the monsoon until ca. 1000 cal yr B.P. After a cold/dry episode that culminated ca. 800 cal yr B.P., the monsoon again strengthened and continued until today. A sharp decrease in temperature and rainfall at 4000–3500 cal yr B.P. represents the weakest monsoon event of the Holocene record. This cold/dry event correlates with proxy data from other localities of the Indian subcontinent, Arabian Sea, and western Tibet.