bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental evidence of reduced diversity of seedlings due to climate modification in a Mediterranean‐type community
Authors: Lloret Francisco , Peñuelas Josep , Estiarte Marc 
Published: December 2004

AbstractWe are still lacking in experimental evidence of the effects of climate change on the richness of plant species under field conditions. We report a decrease in the species richness of recruited seedlings in a Mediterranean shrubland in experimentally induced drought and warming over 4 consecutive years. Drought decreased the number of emerging seedlings and their respective species richness. Warming also decreased seedling species richness, but it did not affect the number of emerging seedlings. Species that produce fewer recruits are more likely to disappear in drier or warmer scenarios. However, when the effect of induced climate treatment was greatest, the more abundant species in control stands were not necessarily the ones least affected by treatment; in other words, species‐idiosyncratic responses may occur. These results show that demographic processes are sensitive to minor climate changes, with probable consequences on the diversity and structure of the future plant communities.
Vegetation structure characteristics and relationships of Kalahari woodlands and savannas
Authors: Privette J.L. , Tian Y. , Roberts G. , Scholes R.J. , Wang Y. , Caylor K.K. , Frost P. , Mukelabai M. 
Published: December 2004

AbstractThe Kalahari Transect is one of several International Geosphere–Biosphere Programme (IGBP) transects designed to address global change questions at the regional scale, in particular by exploiting natural parameter gradients (Koch et al., 1995). In March 2000, we collected near‐synoptic vegetation structural data at five sites spanning the Kalahari's large precipitation gradient (about 300–1000 mm yr−1) from southern Botswana (∼24°S) to Zambia (∼15°S). All sites were within the expansive Kalahari sandsheet. Common parameters, including plant area index (PAI), leaf area index (LAI) and canopy cover (CC), were measured or derived using several indirect instruments and at multiple spatial scales. Results show that CC and PAI increase with increasing mean annual precipitation. Canopy clumping, defined by the deviation of the gap size distribution from that of randomly distributed foliage, was fairly constant along the gradient. We provide empirical relationships relating these parameters to each other and to precipitation. These results, combined with those in companion Kalahari Transect studies, provide a unique and coherent test bed for ecological modeling. The data may be used to parameterize process models, as well as test internally predicted parameters and their variability in response to well‐characterized climatological differences.
Response of different decomposer communities to the manipulation of moisture availability: potential effects of changing precipitation patterns
Authors: Taylor Astrid Rita , Schröter Dagmar , Pflug Anne , Wolters Volkmar 
Published: December 2004

AbstractThe potential impacts of changes in precipitation patterns associated with global climate change on the relationship between soil community diversity and litter decomposition were investigated. For a period of ca. 5 months, two decomposer communities in litterbags (1000 and 45 μm mesh size) containing spruce litter were subjected to two irrigation treatments: constant and fluctuating (drying/rewetting) moisture conditions. The latter were expected to induce moisture stress on the decomposer communities. The two mesh sizes were used to exclude different faunal components from the decomposer communities. The 1000 μm mesh excluded only the macrofauna, whereas the 45 μm mesh excluded both the macro‐ and mesofauna. In the short‐term perspective of the present study, mesofauna abundance showed no response to imposed fluctuating moisture conditions. Irrespective of the presence of mesofauna, mass loss, microbial biomass and the control mechanisms, regulating carbon mineralization appeared unaffected by fluctuating moisture conditions. The reduction in the functional/structural diversity of the decomposer communities in the 45 μm litterbags resulted in strongly increased Nematoda abundance but it did not alter the response of Nematoda to fluctuating moisture conditions. Processes in the nitrogen (N)‐cycle and mass loss were sensitive indicators of changes in the structural and functional complexity of decomposer communities. However, a negative effect of fluctuating moisture conditions on extractable N was coupled to the presence of mesofauna. Extremes in rainfall patterns, generated by climate change, may have a negative impact on the availability of nutrients, particularly N, for plants. This effect could be amplified by an additional impoverishment in the structural and functional complexity of the respective decomposer communities.
Role of land cover changes for atmospheric CO2 increase and climate change during the last 150 years
Authors: Brovkin Victor , Sitch Stephen , Von Bloh Werner , Claussen Martin , Bauer Eva , Cramer Wolfgang 
Published: December 2004

AbstractWe assess the role of changing natural (volcanic, aerosol, insolation) and anthropogenic (CO2 emissions, land cover) forcings on the global climate system over the last 150 years using an earth system model of intermediate complexity, CLIMBER‐2. We apply several datasets of historical land‐use reconstructions: the cropland dataset by Ramankutty & Foley (1999) (R&F), the HYDE land cover dataset of Klein Goldewijk (2001), and the land‐use emissions data from Houghton & Hackler (2002). Comparison between the simulated and observed temporal evolution of atmospheric CO2 and δ13CO2 are used to evaluate these datasets. To check model uncertainty, CLIMBER‐2 was coupled to the more complex Lund–Potsdam–Jena (LPJ) dynamic global vegetation model.In simulation with R&F dataset, biogeophysical mechanisms due to land cover changes tend to decrease global air temperature by 0.26°C, while biogeochemical mechanisms act to warm the climate by 0.18°C. The net effect on climate is negligible on a global scale, but pronounced over the land in the temperate and high northern latitudes where a cooling due to an increase in land surface albedo offsets the warming due to land‐use CO2 emissions.Land cover changes led to estimated increases in atmospheric CO2 of between 22 and 43 ppmv. Over the entire period 1800–2000, simulated δ13CO2 with HYDE compares most favourably with ice core during 1850–1950 and Cape Grim data, indicating preference of earlier land clearance in HYDE over R&F. In relative terms, land cover forcing corresponds to 25–49% of the observed growth in atmospheric CO2. This contribution declined from 36–60% during 1850–1960 to 4–35% during 1960–2000. CLIMBER‐2‐LPJ simulates the land cover contribution to atmospheric CO2 growth to decrease from 68% during 1900–1960 to 12% in the 1980s. Overall, our simulations show a decline in the relative role of land cover changes for atmospheric CO2 increase during the last 150 years.
Nitrogen input mediates the effect of free‐air CO2 enrichment on mycorrhizal fungal abundance
Authors: Staddon Philip L. , Jakobsen Iver , Blum Herbert 
Published: December 2004

AbstractPlots containing Lolium perenne L., Trifolium repens L. or a mixture of both plant species were exposed to elevated atmospheric CO2 (eCO2) for 10 consecutive seasons using free‐air CO2 enrichment technology at ETH Zürich, Switzerland. The CO2 treatment was crossed with a two‐level nitrogen (N) fertilization treatment. In the tenth year, soil samples were collected on three occasions through the growing season to assess the impact of eCO2 and N fertilization on mycorrhizal fungal abundance. Soil moisture content, which varied with harvest date, was linked to the vegetation type and was higher under eCO2. Root weight density was affected by vegetation type: lower for clover, higher for grass. Root weight density was stimulated by eCO2 and decreased by high N fertilization. The percent root length colonized by mycorrhizal fungi was lowest in the clover plots and highest in the grass plots. High N significantly decreased root length colonized. There was no overall effect of eCO2 on root length colonized; however, there was a significant eCO2× N interaction: eCO2 increased root length colonized at high N, but decreased root length colonized at low N. Extraradical mycorrhizal hyphal density was linked to soil moisture content. Extraradical mycorrhizal hyphal density was not affected by eCO2 or high N individually, but as for root length colonized, there was a significant eCO2× N interaction: eCO2 increased extraradical mycorrhizal hyphal density at low N but not at high N. These environmental effects on root colonization and external mycorrhizal hyphae were independent of soil moisture content and root weight density. This field study demonstrated a significant mediating effect of N fertilization on the response of arbuscular mycorrhizal fungi to eCO2 irrespective of any change in root biomass.
Effects of climate on the growth of exotic and indigenous trees in central Zambia
Authors: Chidumayo E. N. 
Published: December 2004

AbstractAim Climate change has far‐reaching effects on species and ecosystems. The aims of this study were to determine how climate factors affect the growth pattern of indigenous and exotic trees in Zambia and to predict tree growth responses to a warmer climate with the use of mathematical models.Location Two savanna sites in central Zambia.Methods Diameter at breast height (1.3 m above ground, d.b.h.) of 91 permanently marked trees belonging to three indigenous and four exotic species was measured fortnightly for periods of 1–2 years from 1998 to 2003. Correlation and regression analysis was used to determine the effect of climate factors (minimum, maximum and average temperature and rainfall) on monthly daily d.b.h. increment of each species. Regression models were used to predict the growth behaviour of trees under a 0.5 °C warmer climate.Results Interactions between temperature and rainfall explained 60–98% of the variation in d.b.h. increment in all the tree species, except the exoticEucalyptus grandis. For deciduous species, stem expansion was delayed by 2–12 weeks following leaf‐flush and d.b.h. increment peaked during the rainy season. Evergreen and deciduous species could not be separated on the basis of annual d.b.h. increment because the higher growth rates of deciduous species compensated for the shorter growing period. Mathematical models predicted slight changes in d.b.h. growth pattern under a 0.5 °C warmer climate in five of the seven species. Significant changes in d.b.h. growth patterns were predicted in the indigenousBridelia micranthaand exoticGmelina arboreaunder a warmer climate. However, models failed to adequately represent potential soil water stress that might result from changes in tree growth patterns and a warmer climate.Main conclusions Climate factors explained a large proportion of the variation in diameter growth of both indigenous and exotic trees, rendering it possible to model tree growth patterns from climate data. Tree growth models suggest that a rise in temperature of 0.5 °C is unlikely to induce significant changes in the growth behaviour of the majority of the studied species. However, because the growth behaviour of some species may be substantially affected by climate change, it is recommended that strategies for the future production of such climate‐sensitive trees should incorporate aspects of climate change.
The biogeography of Hoffmannseggia (Leguminosae, Caesalpinioideae, Caesalpinieae): a tale of many travels
Authors: Simpson Beryl B. , Tate Jennifer A. , Weeks Andrea 
Published: December 2004

AbstractAim  The flowering plant genus Hoffmannseggia consists of 21 species distributed amphitropically between the arid regions of the south‐western United States and adjacent Mexico, and west‐central South America. This pattern of geographical disjunction is shared by numerous other angiosperm genera and has been the subject of discussions for more than a century with various authors advocating a northern origin for particular taxa and others advocating a southern origin. This study uses a well‐supported phylogeny of a genus with numerous species in each area to address the issues of a northern or southern origin and the facility with which organisms move between the two continents.Location  South‐western United States and northern Mexico, northern Chile and Argentina, southern Bolivia, and western Peru.Methods  Using DNA sequence data from the nuclear and chloroplast genomes, we generated a phylogenetic hypothesis for all species of Hoffmannseggia rooted with Zuccagnia and Balsamocarpon. Geographical data were optimized on the resultant tree to assess the probable continent of origin for the genus, the pattern of disjunctions between North and South America, and species radiations within the genus.Main conclusions  Hoffmannseggia arose in South America and initially split into a suffrutescent (somewhat woody) and an herbaceous clade. Within each of these major clades, there have been at least two exchanges between North and South America. There are no data to support an ancestral pan‐American range for Hoffmannseggia and we therefore ascribe the amphitropical disjunctions to long‐distance dispersal. The phylogeny clearly shows that all dispersals were from South to North America and they occurred at different times and thus the pattern is not the result of a single simultaneous set of dispersals.
Hair removal using an 800‐nm Diode Laser: Comparison at different treatment intervals of 45, 60, and 90 days
Authors: Bouzari Navid , Tabatabai Hossein , Abbasi Zahra , Firooz Alireza , Dowlati Yahya 
Published: December 2004

AbstractBackground  Some laser irradiation parameters such as wavelength, fluence, pulse duration, and spot size have been shown to influence the damage of any target inside the skin, however, the role of some patients’ factors such as hair growth cycle is still under debate.Objective  To determine the association of treatment interval and laser treatment outcome.Methods  In a retrospective chart review of 176 patients undergoing laser‐assisted hair removal with a diode laser 24 patients were selected. All accepted to cease the therapy, and be followed‐up for 5 months. At the end of the study the patients were questioned about the efficacy of the treatment as well as the adverse effects. Hair counting was also performed. The adverse effects (pain, blister or erosion, hyperpigmentation, hypopigmentation, and folliculitis) were questioned during the follow‐up period.Results  The mean hair reduction was 78.1%, 45.8%, and 28.7% in 45, 60, and 90‐day interval groups, respectively (P < 0.0001).Conclusion  The treatment interval was related to the treatment outcome in our study.
Skin diseases in south‐east Nigeria: A current perspective
Authors: Nnoruka E. N. 
Published: December 2004

AbstractBackground and objective  The incidence of skin diseases in south‐east Nigeria during the present decade was analyzed and compared with results from other parts of Nigeria, particularly those in the same zone, obtained more than 30 years ago. This study was carried out to update the recent clinical picture of skin diseases in our environment in view of the rapid development, urbanization and advances in the region.Patients and methods  Consecutive new patients seen at the dermatology clinic of the University of Nigeria, Teaching Hospital, Enugu, Nigeria, from February 1999 to March 2001 were included in this prospective study. Only cases seen and examined by the author were included in this study to ensure uniformity of diagnosis.Results  A total of 2871 patients were observed within the study period. Adults accounted for 69.7% and were aged between 18 and 73 years, while the male : female ratio was 1.3 : 1. Allergic skin diseases (24.9%) were the commonest skin disorders identified, as opposed to infestations which accounted for an extremely high result of 33.7% (for the same region between 1968 and 1971). In second place was infections/infestations (19.1%). A reversal of picture was thus observed. Within the allergic disorders; eczemas/dermatitis were found to be the most prevalent followed by follicular (13.7%) and pigmentary disorders (11.1%). Sexually transmitted diseases and HIV/AIDs have increased significantly and accounted for 5.4%. Blistering diseases (1.1%) and malignancies (0.5%) occurred less frequently, similar to results found in resent decades for the same region.Conclusion  The current picture of skin diseases in south‐east Nigeria has changed significantly from mere infections to allergic skin, follicular and pigmentary disorders. Cutaneous lesions secondary to STDs and HIV/AIDs have also increased. Skin lesions related to malnutrition, kwashiorkor and starvation were not observed nor were cutaneous tuberculosis, yaws or pediculosis, while blistering disorders and malignancies remained almost the same. The current picture is similar to that in other developing and Afro‐Caribbean countries. Primary‐care physicians and health‐care providers in Nigeria/Africa need to be aware of the globally changing pattern of skin diseases in the region to enable the allocation of necessary resources (financial, material and human) to manage these skin diseases.
Diatom biostratigraphy of the Cenozoic glaciomarine Pagodroma Group, northern Prince Charles Mountains, East Antarctica*
Authors: WHITEHEAD J. M. , HARWOOD D. M. , McKELVEY B. C. , HAMBREY M. J. , McMINN A. 
Published: December 2004

In the northern Prince Charles Mountains glaciomarine sediments of the Pagodroma Group outcrop on Fisher Massif (Mt Johnston and Fisher Bench Formations) and at the Amery Oasis (Battye Glacier and Bardin Bluffs Formations), at locations 300 and 250 km south of the Amery Ice Shelf edge, respectively. Most of the Pagodroma Group consists of ice‐proximal glaciomarine diamict, and a much subordinate (<2%) amount of more ice‐distal mudstone. Microfossil biostratigraphy based upon in situ and glacially reworked diatoms constrains the ages of the four formations, and identifies at least six intervals of marine fjordal deposition. Sparse diatoms in Mt Johnston Formation diamicts indicate an Early Oligocene age. However, it is unclear whether these diatoms are in situ or else are glacially reworked and represent either an immediately prior or more remote past interglacial. The Battye Glacier and Fisher Bench Formations contain in situ diatoms and are broadly time equivalent, the former dating between 10.7 and 9.0 Ma and the latter between 12.1 or 10.7 Ma and 8.5 Ma. In situ diatoms indicate the Bardin Bluffs Formation to have been deposited between 2.6 and either 1.8 or 0.99 Ma. Glacially reworked diatoms in the Bardin Bluffs and Fisher Bench Formations identify four depositional intervals. The reworked taxa are sourced from Eocene–Oligocene (>30.1 Ma), Middle Miocene (14.5–12.5 Ma and 12.1–11.5 Ma), Early Pliocene (4.9–3.6 Ma) and, tentatively, Late Pliocene (3.4–2.6 Ma) strata. These microfossil data further develop the interpretation that the Pagodroma Group formed during episodes of reduced glacial extent when, in the absence of an ice shelf, marine waters penetrated far southwards into the Lambert Graben of East Antarctica.
Depositional environment and taphonomy of the ‘strings of beads’: Mesoproterozoic multicellular fossils in the Bangemall Supergroup, Western Australia
Authors: MARTIN D. McB. 
Published: December 2004

Enigmatic Mesoproterozoic bedding‐plane structures, informally known as ‘strings of beads’, are common in the Bangemall Supergroup in Western Australia and the Belt Supergroup in North America. The Belt Supergroup structures are formally known as Horodyskia moniliformis, and age constraints show that they are more than 350 million years older than similar 1070 Ma structures in the Bangemall Supergroup. Strings of beads in the Bangemall Supergroup have previously been interpreted as fossils of multicellular organisms based on their morphology and on statistical comparisons with a range of organic and inorganic structures. However, details of their depositional environment and taphonomy, which can provide important insights into their origin, are poorly known. This study shows that strings of beads in the Backdoor Formation of the Bangemall Supergroup were deposited in a subtidal marine‐shelf environment in association with microbial mats and enigmatic dimple marks. The structures are preserved at the base of fine sandstone beds within shoaling‐upward shelfal mudstone and sandstone packages deposited below storm wave‐base. Following deposition from suspension, the strings of beads were bound to the sea floor by microbial mats and their associated mucilage, preventing realignment by palaeocurrents. Relationships between the strings of beads and dimple marks in offshore sandstones suggest that the latter may represent holdfasts to which the strings were originally attached.
A fatigue and creep study in austenitic stainless steel 316L used in exhaust pipes of naval gas turbines
Authors: MARTINS R. F. , BRANCO C. M. 
Published: December 2004

ABSTRACTExhaust pipes of naval gas turbines are made of thin wall tubing of stainless steel grade AISI 316L. The tubes are fabricated by butt welding of different sections with longitudinal and circumferential joints. The plate thickness is about 4.0 mm, and the working temperature varies between 600 °C and 400 °C in the critical zones of the pipe, in the lower and central areas, respectively. The loadings in the tube induce high‐temperature fatigue and creep‐fatigue cracks have nucleated and propagated in the tube near some welded joints. The paper presents FCGR data obtained in CT specimens of used material taken from the pipes and tested at RT, 335, 500 and 600 °C. Preliminary creep data obtained in tension, in thin‐sheet specimens (about 4 mm thickness), also taken from the conduct wall and tested at 500, 550 and 600 °C are also given. These results are crucial to perform a fatigue‐creep interaction life assessment of the critical parts of the structure in the near future. Finally, the paper presents results of research work to investigate carbide precipitation and formation in virgin thin‐sheet specimens subjected to several types of thermal exposures. In some cases, 3–4 d was the time interval between exposures. Grain size measurements were carried out together with microstructural observations in the SEM. The influence of time, temperature and time interval between thermal exposures was assessed comparing the microstructures.
Model complexity versus scatter in fatigue
Authors: SVENSSON T. 
Published: December 2004

ABSTRACTFatigue assessment in industry is often based on simple empirical models, such as the Wöhler curve or the Paris' law. In contrast, fatigue research to a great extent works with very complex models, far from the engineering practice. One explanation for this discrepancy is that the scatter in service fatigue obscures many of the subtle phenomena that can be studied in a laboratory. Here we use a statistical theory for stepwise regression to investigate the role of scatter in the choice of model complexity in fatigue. The results suggest that the amount of complexity used in different design concepts reflects the appreciated knowledge about input parameters. The analysis also points out that even qualitative knowledge about the neglected complexity may be important in order to avoid systematic errors.