bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acclimation of a pleurocarpous moss Pleurozium schreberi (Britt.) Mitt. to enhanced ultraviolet radiation in situ
Authors: LAPPALAINEN NIINA M. , HUTTUNEN SATU , SUOKANERVA HANNE 
Published: July 2010

AbstractWe investigated the responses of ultraviolet (UV)‐absorbing compounds, chlorophylls a and b, carotenoids and the growth responses of the pleurocarpous moss Pleurozium schreberi (Britt.) Mitt. to enhanced UV radiation in situ. The moss was exposed to a 52% elevation above the ambient level of erythemally weighted UV‐B radiation, simulating an approximate 20% reduction in the ozone column, in a dry pine forest in Sodankylä, Finland (67 °22′N, 26 °38′E), under arrays of lamps filtered with cellulose diacetate, which transmitted both UV‐B and UV‐A radiation. The moss was also exposed to elevated UV‐A radiation under control arrays of lamps filtered with Melinex polyester and to ambient radiation under arrays with no lamps in them. Effects of enhanced UV radiation on P. schreberi were recorded during the first 3 years of exposure. Enhanced UV‐B radiation did not affect the segment height growth of the moss. The annual dry mass after the second growing season was higher in the UV‐A control than in the other treatments, and dry mass decreased significantly during the third treatment year in both UV treatments compared with the ambient. The specific leaf area of the UV‐B‐treated mosses was significantly higher than the ambient control mosses during the first 2 years. An increase of UV‐absorbing compounds was found in the mosses under enhanced UV‐B radiation compared with the UV‐A control mosses during the first year. Even though the treatment effect on UV‐absorbing compounds was transient, the concentrations of these compounds correlated with the amount of UV‐A and UV‐B radiation received under the elevated UV‐B treatment. A correlation with the irradiation of previous days and preceding month of the sampling day was found. A seasonal reduction occurred in the amount of UV‐absorbing compounds from the beginning of the summer to late summer. The amount of photosynthetic pigments correlated with the amount of photosynthetically active radiation. The moss P. schreberi was thus found to tolerate increasing UV‐B radiation. Our data indicate that P. schreberi tolerates a 52% increase in erythemally weighted UV‐B radiation above ambient, responding during the first few years of exposure by increasing UV‐absorbing compounds and specific leaf area, and decreasing annual dry mass, and then acclimating to its altered radiation environment.
Climate warming causes phenological shift in Pink Salmon, Oncorhynchus gorbuscha, behavior at Auke Creek, Alaska
Authors: TAYLOR SIDNEY G. 
Published: July 2010

AbstractThirty‐four years (1972–2005) of water temperature data and extensive biological observations at Auke Creek, Alaska indicate a general warming trend that affected the native pink salmon (Oncorhynchus gorbuscha) population. Serial environmental records at nearby Auke Bay, Alaska over 46 years show trends of increasing air and sea surface temperatures. Trends of increased total precipitation and earlier date of ice out on nearby Auke Lake also occurred, but not at significant rates. Average water temperatures during the incubation of pink salmon in Auke Creek increased at a rate of 0.03 °C yr−1 over the 34‐year period. For the 1972–2005 broods, midpoints of fry migrations from Auke Creek ranged between April 2 and May 7, and there was a trend of earlier migration of pink salmon fry at a rate of − 0.5 days yr−1. The migration timing of adult salmon into Auke Creek also showed a trend toward earlier timing. The earlier adult migration combined with warmer incubation temperatures are related to earlier migration of pink salmon fry. If the observed warming trend continues, Auke Creek may become unsuitable habitat for pink salmon. Given the trend for salmon fry to migrate earlier, a larger portion of the population may become mismatched with optimum environmental conditions during their early marine life history. If salmon adults continue to migrate into the creek earlier when water temperatures are commonly high, it will result in increased prespawning mortality.
Predicting differential effects of climate change at the population level with life‐cycle models of spring Chinook salmon
Authors: CROZIER LISA G. , ZABEL RICHARD W. , HAMLET ALAN F. 
Published: July 2010

AbstractHabitat conditions mediate the effects of climate, so neighboring populations with differing habitat conditions may differ in their responses to climate change. We have previously observed that juvenile survival in Snake River spring/summer Chinook salmon is strongly correlated with summer temperature in some populations and with fall streamflow in others. Here, we explore potential differential responses of the viability of four of these populations to changes in streamflow and temperature that might result from climate change. First, we linked predicted changes in air temperature and precipitation from several General Circulation Models to a local hydrological model to project streamflow and air temperature under two climate‐change scenarios. Then, we developed a stochastic, density‐dependent life‐cycle model with independent environmental effects in juvenile and ocean stages, and parameterized the model for each population. We found that mean abundance decreased 20–50% and the probability of quasi‐extinction increased dramatically (from 0.1–0.4 to 0.3–0.9) for all populations in both scenarios. Differences between populations were greater in the more moderate climate scenario than in the more extreme, hot/dry scenario. Model results were relatively robust to realistic uncertainty in freshwater survival parameters in all scenarios. Our results demonstrate that detailed population models can usefully incorporate climate‐change predictions, and that global warming poses a direct threat to freshwater stages in these fish, increasing their risk of extinction. Because differences in habitat may contribute to the individualistic population responses we observed, we infer that maintaining habitat diversity will help buffer some species from the impacts of climate change.
Rice yield enhancement by elevated CO2 is reduced in cool weather
Authors: SHIMONO HIROYUKI , OKADA MASUMI , YAMAKAWA YASUHIRO , NAKAMURA HIROFUMI , KOBAYASHI KAZUHIKO , HASEGAWA TOSHIHIRO 
Published: July 2010

AbstractThe projected increase of atmospheric CO2 concentration ([CO2]) is expected to increase rice yield, but little is known of the effects of [CO2] at low temperature, which is the major constraint to growing rice in cool climates. We grew rice under two levels of [CO2] (ambient and elevated by 200 μmol mol−1) and two nitrogen (N) fertilization regimes in northern Japan in 2003 (cool weather) and 2004 (warm weather) in the field in a free‐air CO2 enrichment (FACE) system. Elevated [CO2] significantly increased grain yield in both years in both N regimes, but the magnitude of the increase differed between years: 6% in 2003 vs. 17% in 2004, with a significant interaction between [CO2] and year. This difference resulted from responses of spikelet number and ripening percentage to elevated [CO2]. Enhancement of dry matter production and N uptake at heading by elevated [CO2] was smaller in 2003 than in 2004, although at maturity there was no difference between years. No significant interaction between N regime and [CO2] was detected in yield and yield components. The results suggest that yield gain due to elevated [CO2] can be reduced by low temperature.
Frost in a future climate: modelling interactive effects of warmer temperatures and rising atmospheric [CO2] on the incidence and severity of frost damage in a temperate evergreen (Eucalyptus pauciflora)
Authors: WOLDENDORP GEMMA , HILL MICHAEL J. , DORAN RUTH , BALL MARILYN C. 
Published: July 2010

AbstractAlthough plants are more susceptible to frost damage under elevated atmospheric [CO2], the importance of frost damage under future, warmer climate scenarios is unknown. Accordingly, we used a model to examine the incidence and severity of frost damage to snow gum (Eucalyptus pauciflora) in a sub‐alpine region of Australia for current and future conditions using the A2 IPCC elevated CO2 and climate change scenario. An existing model for predicting frost effects on E. pauciflora seedlings was adapted to include effects of elevated [CO2] on acclimation to freezing temperatures, calibrated with field data, and applied to a study region in Victoria using climate scenario data from CSIRO's Global Climate Model C‐CAM for current (1975–2004) and future (2035–2064) 30 years climate sequences. Temperatures below 0 °C were predicted to occur less frequently while the coldest temperatures (i.e. those below −8 °C) were almost as common in the future as in the current climate. Both elevated [CO2] and climate warming affected the timing and rates of acclimation and de‐acclimation of snow gum to freezing temperatures, potentially reducing the length of time that plants are fully frost tolerant and increasing the length of the growing season. Despite fewer days when temperatures fall below 0 °C in the future, with consequently fewer damaging frosts with lower average levels of impact, individual weather sequences resulting in widespread plant mortality may still occur. Furthermore, delayed acclimation due to either warming or rising [CO2] combined with an early severe frost could lead to more frost damage and higher mortality than would occur in current conditions. Effects of elevated [CO2] on frost damage were greater in autumn, while warming had more effect in spring. Thus, frost damage will continue to be a management issue for plantation and forest management in regions where frosts persist.
The lightning–biota climatic feedback
Authors: SHEPON ALON , GILDOR HEZI 
Published: July 2010

AbstractWe investigate a negative climatic feedback which involves an increase in deposition of lightning‐produced nitrogen compounds into ecosystems as a response to a global temperature rise. This increases primary production on both land and ocean, which reduces atmospheric carbon dioxide (CO2), and consequently global temperature in return. Large uncertainties in numerous processes and parameters in this feedback exist and therefore its importance is unclear. This feedback is investigated using a conceptual dynamical model, including assessing its role in counteracting anthropogenic‐induced warming by reducing the rate of accumulation and concentration of atmospheric CO2. Overall, this study suggests that this feedback is of mild strength in the climate system, but raises the intriguing possibility that it should be considered in long‐term climate simulations. Further work in investigating this climatic feedback is required.
Effects of soil bulk density and strength on seedling growth of annual ryegrass and tall fescue in controlled environment
Authors: Bartholomew P. W. , Williams R. D. 
Published: July 2010

AbstractGrasses sown with minimal tillage commonly exhibit slower establishment and lower herbage yield than those sown into a conventionally tilled seedbed. Some of the difference in performance may be attributed to differences in bulk density between tilled and untilled ground. It is not known if performance rankings of grass cultivars established in clean‐tilled ground remain valid in more compacted soil characteristic of no‐till seeding. Seedlings of five cultivars of Italian ryegrass (Lolium multiflorum Lam.) [IRG] and five cultivars of tall fescue [Festuca arundinacea Schreb. also known as Lolium arundinaceum Schreb. (Darbysh.)] [TF] were grown in pots of Coyle or Stephenville series soils (sandy loam and loamy sand respectively) packed to 0·75, 0·88 or 1·00 of maximum packing densities, established as 1·47 and 1·68 g cm−3 for Coyle and Stephenville soil respectively. Leaf appearance was measured until seedling harvest at 540 growing degree days after emergence. Increased bulk density decreased leaf appearance rates, reduced final leaf and tiller numbers and aerial and root biomass at harvest in both IRG and TF. Among cultivars within species, there was no difference (P > 0·05) in response to measured parameters to change in bulk density. Seedling growth and development of IRG were consistently greater than that of TF but showed greater reduction in response to increased soil bulk density. Soil strength provided a better indicator of likely seedling response to soil compaction than bulk density. The results suggest that cultivar rankings obtained under conventional tillage are likely to be valid with no‐till planting.
Ecological differentiation between coexisting sexual and asexual strains of Daphnia pulex
Authors: Lehto Mikko P. , Haag Christoph R. 
Published: July 2010

Summary 1. The widespread occurrence of sexual reproduction indicates that the benefits of sex can overcome its costs relative to asexual reproduction. Many closely related sexual and asexual taxa have different geographic distributions suggesting that their relative fitness may depend on the environment. However, support for such ecological differentiation is mainly based on correlative evidence, with experimental support being scarce, especially from the wild. 2. We studied ecological differentiation between asexual (obligate parthenogenetic) and sexual (cyclical parthenogenetic) Daphnia pulex in Southern Finland, where the two forms (‘reproduction types’) coexist regionally in a metapopulation. We found differences in several environmental factors between ponds inhabited by sexual and asexual populations (pH, calcium, oxygen, conductivity and absorbance). 3. A reciprocal competition experiment carried out directly in the natural ponds confirmed that sexuals and asexuals were ecologically differentiated; their relative fitness was found to depend on pH and calcium titres of the ponds. 4. Our study provides clear experimental evidence for the coexistence of closely related sexual and asexual taxa being mediated by ecological differentiation. In addition, the results of our competition experiment suggest that each of the reproduction types has a larger fundamental niche (absence of competition) than a realized niche (presence of competition). Thus, by temporarily creating competition‐free space, metapopulation turnover may allow the reproduction types to occur in a wider range of habitats than under more stable population dynamics, and may thus further contribute to stabilize regional coexistence.
Predicting invasive alien plant distributions: how geographical bias in occurrence records influences model performance
Authors: Wolmarans René , Robertson Mark P. , van Rensburg Berndt J. 
Published: July 2010

AbstractAim  To investigate the impact of geographical bias on the performance of ecological niche models for invasive plant species.Location  South Africa and Australia.Methods  We selected 10 Australian plants invasive in South Africa and nine South African plants invasive in Australia. Geographical bias was simulated in occurrence records obtained from the native range of a species to represent two scenarios. For the first scenario (A, worst‐case) a proportion of records were excluded from a specific region of a species’ range and for the second scenario (B, less extreme) only some records were excluded from that specific region of the range. Introduced range predictions were produced with the Maxent modelling algorithm where models were calibrated with datasets from these biased occurrence records and 19 bioclimatic variables. Models were evaluated with independent test data obtained from the introduced range of the species. Geographical bias was quantified as the proportional difference between the occurrence records from a control and a biased dataset, and environmental bias was expressed as either the difference in marginality or tolerance between these datasets. Model performance [assessed using the conventional and modified AUC (area under the curve of receiver‐operating characteristic plots) and the maximum true skill statistic] was compared between models calibrated with occurrence records from a biased dataset and a control dataset.Results  We found considerable variation in the relationship between geographical and environmental bias. Environmental bias, expressed as the difference in marginality, differed significantly across treatments. Model performance did not differ significantly among treatments. Regions predicted as suitable for most of the species were very similar when compared between a biased and control dataset, with only a few exceptions.Main conclusions  The geographical bias simulated in this study was sufficient to result in significant environmental bias across treatments, but despite this we did not find a significant effect on model performance. Differences in the environmental spaces occupied by the species in their native and invaded ranges may explain why we did not find a significant effect on model performance.
Tree diversity on islands: assembly rules, passive sampling and the theory of island biogeography
Authors: Burns K. C. , Berg Jenny , Bialynicka‐Birula Ada , Kratchmer Sabrina , Shortt Katelyn 
Published: July 2010

AbstractAim  Species diversity is distributed heterogeneously through space, for reasons that are poorly understood. We tested three hypotheses to account for spatial variation in coniferous tree species diversity in a temperate island archipelago. The theory of island biogeography (ToIB) predicts that island area affects species diversity both directly (by increasing habitat diversity) and indirectly (by increasing abundances, which in turn reduce extinction rates). The ToIB also predicts that island isolation directly affects species diversity by reducing immigration rates. The passive sampling hypothesis predicts that island area and isolation both affect species diversity indirectly, by increasing and decreasing abundances, respectively. Community assembly rules (i.e. even partitioning of conifer abundances among islands) might also reduce tree species diversity beyond the core predictions of ToIB and the passive sampling hypothesis.Location  Barkley Sound, British Columbia, Canada.Methods  The abundances of eight coniferous tree species were quantified on 34 islands and two (1 ha) mainland plots. The predictions of the ToIB and the passive sampling hypothesis were tested using path analysis, and null models were used to test for abundance‐based assembly rules and to further test the passive sampling hypothesis.Results  Path analysis showed that island area and isolation did not have direct, statistical effects on tree species diversity. Instead, both geographic variables had direct statistical effects on total tree abundances, which in turn predicted tree diversity. Results from several passive sampling null models were correlated with observed patterns in species diversity, but they consistently overestimated the number of tree species inhabiting most islands. A different suite of null models showed support for community assembly rules, or that tree species often reached higher abundances on islands that housed fewer heterospecific trees.Main conclusions  Results were inconsistent with the ToIB. Instead, patterns in tree diversity were best explained by a combination of stochastic (passive sampling) and deterministic (assembly rules) processes. Stochastic and deterministic processes are commonly considered to be exclusive explanations for island community structure, but results from this study suggest that they can work synergistically to structure island tree communities.
High Arctic plant community resists 15 years of experimental warming
Authors: Hudson James M. G. , Henry Greg H. R. 
Published: July 2010

Summary 1. Identifying plant communities that are resistant to climate change will be critical for developing accurate, wide‐scale vegetation change predictions. Most northern plant communities, especially tundra, have shown strong responses to experimental and observed warming. 2. Experimental warming is a key tool for understanding vegetation responses to climate change. We used open‐top chambers to passively warm an evergreen‐shrub heath by 1.0–1.3 °C for 15 years at Alexandra Fiord, Nunavut, Canada (79 °N). In 1996, 2000 and 2007, we measured height, plant composition and abundance with a point‐intercept method. 3. Experimental warming did not strongly affect vascular plant cover, canopy height or species diversity, but it did increase bryophyte cover by 6.3% and decrease lichen cover by 3.5%. Temporal changes in plant cover were more frequent and of greater magnitude than changes due to experimental warming. 4. Synthesis. This evergreen‐shrub heath continues to exhibit community‐level resistance to long‐term experimental warming, in contrast to most Arctic plant communities. Our findings support the view that only substantial climatic changes will alter unproductive ecosystems.
Operating room cost for coronary artery bypass graft procedures: does experience or severity of illness matter?
Authors: Chung Wei‐Ching , Fan Pao‐Luo , Chiu Herng‐Chia , Yang Chun‐Yuh , Huang Kun‐Lun , Tzeng Dong‐Sheng 
Published: July 2010

AbstractObjective  Very few studies have addressed the magnitude of the effect of the condition of the patients and the surgical volume on possible cost savings in coronary artery bypass grafting (CABG). The objectives of this study were to analyse and compare the costs of the CABG operating room (OR) between two hospitals, and to examine the effect of surgical volume and severity of illness on the OR costs.Method  The charts of patients who were diagnosed with coronary artery disease and who underwent CABG at two acute tertiary care hospitals in 2004 were reviewed retrospectively. Data on patient demographics, length of stay (LOS) and the American Society of Anesthesiologists Physical Status (ASAPS) score were extracted from the patient records. Cost information was obtained from detailed billing charges and from the financial accounting divisions of the hospitals.Results  The high‐volume hospital consumed fewer resources than the low‐volume hospital (US$5411 vs. US$6407). The age of the patients, surgical volume, operating hours and LOS were associated with the OR cost. Patient age and ASAPS score, hospital, and surgical volume were associated with LOS. Patient age, the number of diseased vessels, doctor volume and pump used or not were positively associated with the operation time. The LOS and the operation time may be the mediators of the relationship between the ASAPS score and cost, and may moderate the association of volume with cost.Conclusions  This study supports the saying that ‘practice makes perfect’. The knowledge and experience of the surgeons and the hospital management team are equally important in the supply of health services to patients with varying severity of illness, and are needed to maintain the competitive position of a hospital.