bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulated climate change: are passive greenhouses a valid microcosm for testing the biological effects of environmental perturbations?
Authors: KENNEDY ANDREW D. 
Published: April 2006

AbstractThis paper considers the use of passive greenhouse apparatus in field experiments investigating the biological consequences of climate change. The literature contains many accounts of such experiments claiming relevance of greenhouse treatment effects to global change scenarios. However, inadequacies in microclimate monitoring, together with incomplete understanding of greenhouse modes of action, cast doubt upon such claims. Here, treatment effects upon temperature (magnitude, range, variation, rates of change), moisture (humidity, precipitation, soil water content), light (intensity, spectral distribution), gas composition, snow cover, and wind speed are reviewed in the context of Intergovernmental Panel on Climate Change (IPCC) predictions. It is revealed that greenhouses modify each of these potentially limiting factors in a complex and interactive manner, but that the relationship between this modification and forecast conditions of climate change is poor. Interpretation of biological responses, and their extrapolation to predictive models, is thus unreliable. In order that future greenhouse experiments may overcome criticisms of artefact and lack of rigour, two amendments to methodology are proposed: (1) objective‐orientated design of greenhouse apparatus (2) multiple controls addressing individual environmental factors. The importance of a priori testing of microclimate treatment effects is stressed.
Growth response of subalpine fir (Abies lasiocarpa) to climate in the Olympic Mountains, Washington, USA
Authors: ETTL GREGORY J. , PETERSON DAVID L. 
Published: April 2006

AbstractGrowth response of subalpine fir (Abies lasiocarpa) to climate was studied across its local geographical and elevation range in the Olympic Mountains, Washington. A dendroecological analysis of subalpine fir across a range of elevations (1350‐1850 m) and annual precipitation (125‐350 cm y−1), was used to compare environmental factors affecting growth. Climate‐growth relationships were explored using Pearson product‐moment correlation coefficients; partial correlation analysis was used to assess relationships among site chronologies and climatic variables. Radial growth is negatively correlated with winter precipitation at high elevation and wet sites, but not at low and middle elevation dry sites. Growth is positively correlated with current growing season temperature at all sites; however, growth is negatively correlated with previous year August temperature, indicating that climate affects growth in subsequent years. Positive correlations between growth and summer precipitation during the growing season at low and middle elevation dry sites suggest that soil moisture is partially limiting to growth on these sites. If the climate of the Pacific Northwest becomes warmer and drier, then subalpine fir growth may increase at high elevation and wet sites, but may decrease at lower elevation dry sites in the Olympic Mountains. However, the growth response of subalpine fir to potentially rapid climate change will not be uniform because subalpine fir grows over a wide range of topographic features, habitats, and local climates at different geographical scales. A comparison of growth response to current growing season temperature suggests that the temperature‐related growth response of subalpine fir is not adequately described by the parabolic curve used in JABOWA‐based models.
A new technique for estimating rates of carboxylation and electron transport in leaves of C3 plants for use in dynamic global vegetation models
Authors: BEERLING D.J. , QUICK W.P. 
Published: April 2006

AbstractThe possible responses of the terrestrial biosphere to future CO2 increases and associated climatic change are being investigated using dynamic global vegetation models (DG VMs) which include the Farquhar et al. (1980) biochemical model of leaf assimilation as the primary means of carbon capture. This model requires representative values of the maximum rates of Rubisco activity, Vmax, and electron transport, Jmax, for different vegetation types when applied at the global scale. Here, we describe an approach for calculating these values based on measurements of the maximum rate of leaf photosynthesis (Amax) 13C discrimination. The approach is tested and validated by comparison with measurements of Rubisco activity assayed directly on wild‐type and transgenic Nicotiana tabacum (tobacco) plants with altered Rubisco activity grown under ambient and elevated CO2 mole fractions with high and low N‐supply. Vmax and Jmax values are reported for 18 different vegetation types with global coverage. Both variables were linearly related reinforcing the idea of optimal allocation of resources to photosynthesis (light harvesting vs. Rubisco) at the global scale. The reported figures should be of value to the further development of vegetation and ecosystem models employing mechanistic DGVMs.
The influence of elevated CO2 on community structure, biomass and carbon balance of mediterranean old‐fleld microcosms
Authors: NAVAS MARIE‐LAURE , GUILLERM JEAN‐LOUIS , FABREGUETTES JACQUES , ROY JACQUES 
Published: April 2006

AbstractWe studied the effects of a doubling of atmospheric CO2 concentration on intact monoliths of Mediterranean grassland in growth chambers where climatic field conditions were simulated. During the six month growing season, changes in community structure were monitored by quantifying species richness and cover. The CO2 exchange of microcosms was measured continuously and the resulting quantity and quality of biomass were evaluated. Species richness and cover did not respond to elevated CO2. After one month of treatment, CO2 exchange measured during the day did not differ between CO2 levels but the night respiration was two‐fold higher under elevated CO2. Stimulations of both day and night CO2 flux by short‐term CO2 enrichment were recorded several times during the growing season. These results suggest that despite some downward adjustment of photosynthesis, net canopy photosynthesis was stimulated by elevated CO2, but this stimulation was compensated for by an increased respiration. The 20% stimulation of final phytomass under elevated CO2 was not significant: it resulted from unchanged live plant matter but a significant, 100% increase in litter accumulation. These results suggest that in low‐productivity Mediterranean herbaceous systems, the greatest effect of CO2 is not on the storage of carbon in biomass but on the turnover of the carbon in the plants.
Collembolan water relations and environmental change in the maritime Antarctic
Authors: BLOCK WILLIAM , HARRISSON PAUL M. 
Published: April 2006

AbstrachThe water status of the collembolan Cryptopygtus antarcticus (Willem) was investigated from April 1984 to December 1987 at Signy Island, maritime Antarctic, by monthly field sampling to determine body water content. Water content, expressed either as the weight of water per unit dry weight or as a proportion of fresh weight, exhibited both a seasonal cycle and an upward trend over the 44‐month study, both of which were highly significant. On an annual basis, body water content was at a minimum (1.21 g g−1) in July and maximal (1.98 g g−1) in September, whilst over the entire study water contents increased from 1.3 to 2.0 g g−1 (or 57‐66% of fresh weight) calculated from the fitted linear regression line. Field water contents were below those found for this species in culture (2.9‐5.9 g g−1). Individual C. antarcticus survived experimental loss of 20% of their body water with a resultant significant rise in haemolymph osmolarity from 285 to 397 mOsm L−1 and there was no evidence of osmoregulation under the experimental conditions of 20 °C and 35% relative humidity. The cuticular permeability (mean conductance) of individual Collembola in dry air increased exponentially with temperature over the range D‐45 °C (Q10= 2.0) showing no control of water loss.The physiological response of C. antarcticus suggests that it experiences water stress in its maritime Antarctic habitats with significant seasonal variations of body water content, which correlate with annual cycles of water availability. It is concluded that the significant rise in its mean body water content over the 44‐month field study was associated with increased glacial ablation due to higher levels of irradiation and windspeed making available more liquid water. Analyses of climate records for Signy Island from 1947 to 1990 showed that mean monthly air temperature rose by 0.93 °C over this period and by 2.29 °C during the 1980s, both statistically significant increases. Mean monthly windspeeds also increased significantly during 1970–90, and it is suggested that this parameter is the primary climatic driving force behind the increase in glacial ablation during the last two decades. The field water status of species such as C. antarcticus may reflect changes in the patterns of atmospheric circulation, associated with the circumpolar vortex, through increased ozone depletion due to increased tropospheric concentrations of halocarbons.
Whole plant respiration and photosynthesis of wheat under increased CO2 concentration and temperature: long‐term vs. short‐term distinctions for modelling
Authors: GIFFORD ROGER M. 
Published: April 2006

AbstractShort‐ and long‐term effects of elevated CO2 concentration and temperature on whole plant respiratory relationships are examined for wheat grown at four constant temperatures and at two CO2 concentrations. Whole plant CO2 exchange was measured on a 24 h basis and measurement conditions varied both to observe short‐term effects and to determine the growth respiration coefficient (rg), dry weight maintenance coefficient (rm), basal (i.e. dark acclimated) respiration coefficient (rg), and 24 h respiration:photosynthesis ratio (R:P). There was no response of rg to short‐term variation in CO2 concentration. For plants with adequate N supply, rg was unaffected by the growth‐CO2 despite a 10% reduction in the plant's N concentration (%N). However, rm was decreased 13%, and rb was decreased 20% by growth in elevated CO2 concentration relative to ambient. Nevertheless, R:P was not affected by growth in elevated CO2. Whole plant respiration responded to short‐term variation of ± 5 °C around the growth temperature with low sensitivity (Q10= 1.8 at 15 °C, 1.3 at 30 °C). The shape of the response of whole plant respiration to growth temperature was different from that of the short term response, being a slanted S‐shape declining between 25 and 30 °C. While rm, increased, rg decreased when growth temperature increased between 15 and 20 °C. Above 20 °C rm became temperature insensitive while rg increased with growth temperature. Despite these complex component responses, R:P increased only from 0.40 to 0.43 between 15° and 30 °C growth temperatures. Giving the plants a step increase in temperature caused a transient increase in R:P which recovered to the pre‐transient value in 3 days. It is concluded that use of a constant R:P with respect to average temperature and CO2 concentration may be a more simple and accurate way to model the responses of wheat crop respiration to ‘climate change’ than the more complex and mechanistically dubious functional analysis into growth and maintenance components.
Significance of ocean carbonate budgets for the global carbon cycle
Authors: HOLLIGAN PATRICK M. , ROBERTSON JANE E. 
Published: April 2006

AbstractChanges in the trace gas composition of the atmosphere over glacial–interglacial cycles are linked to changes in the oceanic carbon cycle. This paper examines the role of biologically driven fluxes of organic and inorganic carbon in modifying the carbon dioxide chemistry of the oceans, and the corresponding implications for the partitioning of CO2 between the atmosphere and ocean. Relevant details of the marine carbon system are presented together with an assessment of the significance of remineralization and dissolution processes. Recent estimates of the marine carbonate fluxes show significant uncertainties and inconsistencies which must be resolved in order to assess fully the role of the oceans' biota in the marine carbon system. Various types of ocean carbon cycle models have been developed in order to interpret the changes in past atmospheric carbon dioxide. Some take account of the role of the oceans' biota, focussing in the main on the cycling of organic matter. Relatively few have considered the role of the carbonate pump and the subtle interactions between organic and inorganic carbon cycling. The significance of carbonate formation and dissolution, and of the effects of global change on the marine carbonate system, for air–sea fluxes of CO2 are discussed. Finally some recommendations for future research are made in order to improve our understanding of how spatial and temporal variation in marine carbonate fluxes, in conjunction with processes determining the oxidation and burial of organic matter in the oceans, affect levels of CO2 in the atmosphere.
Effects of growth under elevated UV‐B on photosynthesis and isoprene emission in Quercus gambelii and Mucuna pruriens
Authors: HARLEY PETER , DEEM GREG , FLINT STEPHAN , CALDWELL MARTYN 
Published: April 2006

AbstractIncreasing surface levels of UV‐B resulting from stratospheric ozone reduction directly affect tropospheric photochemistry. There may also be indirect tropospheric effects due to changes in emission of organic compounds from vegetation. We treated woody and herbaceous isoprene‐emitting species in the field with supplemental UV‐B simulating 30% ozone depletion. For Quercus gambelii, photosynthesis and isoprene emission were significantly greater in elevated UV‐B treatments when expressed on a leaf area basis, but not on a leaf mass basis. Leaves of Mucuna pruriens, however, showed no significant differences in photosynthesis or isoprene emission between treatments, nor when exposed for 45 min to acute high levels of UV‐B. Elevated UV‐B during growth did not elicit significant isoprene emission from Acer platanoides, a non‐emitting species. Other potential UV‐B effects, such as changes in leaf area or species composition, which may influence regional isoprene emissions, should be examined.
Growth at elevated carbon dioxide concentration reduces hydraulic conductance in alfalfa and soybean
Authors: BUNCE JAMES A. 
Published: April 2006

AbstractHydraulic conductances of alfalfa and soybean plants grown in controlled environment chambers at the current ambient carbon dioxide concentration and at twice the current ambient concentration were determined from measurements of transpiration rate and leaf and stem water potentials in the growth conditions. Growth at elevated carbon dioxide concentration reduced both transpiration rate and hydraulic conductance from the soil to the leaf in both species. Hydraulic conductance from the soil to the base of the stem was also lower at elevated carbon dioxide in soybean, but not alfalfa. These measurements identified the stem to leaf hydraulic pathway as a major target of the carbon dioxide effect in both species. The conductance of excised stem segments was much less in plants grown at elevated carbon dioxide in soybeans.
Effects of ultraviolet radiation on corals and other coral reef organisms
Authors: SHICK J. MALCOLM , LESSER MICHAEL P. , JOKIEL PAUL L. 
Published: April 2006

AbstractThe discovery of the importance of solar ultraviolet radiation (UVR) as a factor affecting the biology of coral reefs dates only to about 1980. Interest has heightened during the past five years owing to the demonstration of loss of stratospheric ozone through human activities. We have only begun to document gross, qualitative effects of UVR on coral reef organisms, usually in experiments comparing the biological response to the presence or absence of UVR through the use of UV‐cutoff filters, or to varying levels of UVR in transplantation studies. Most such studies have not distinguished between the effects of UVA (320–400 nm) and those of UVB (290–320 nm), although in the context of global change involving stratospheric ozone loss, it is the latter wavelengths that are relevant. To date we have been addressing physiological and ecological questions, not yet attempting to evaluate quantitatively the impact of forecast increases in solar UVB penetration. Interacting and synergistic effects of UVR with increased temperature, pollutants, sedimentation, visible light, etc. have scarcely been studied but will be essential to understanding and predicting the fate of coral reefs under conditions of global change.Here we comprehensively review the effects of UVR on corals and other reef macroorganisms, mindful that although much is known of proximal effects, little of this knowledge is directly useful in making long‐term predictions regarding the health of coral reefs. We conclude that even small anthropogenic increases in UVB levels will have sublethal physiological manifestations in corals and other reef organisms, but that this will have relatively small impact on the distribution of reef corals and coral reefs, perhaps affecting their minimum depths of occurrence.
Seasonal net carbon dioxide exchange of a beech forest with the atmosphere
Authors: VALENTINI R. , De ANGELIS P. , MATTEUCCI G. , MONACO R. , DORE S. , MUCNOZZA G. E. SCARASCIA 
Published: April 2006

AbstractThe seasonal carbon dioxide exchange of a beech forest of Central Italy was studied by means of the eddy covariance technique. Additional measurements of biomass respiration with cuvettes and relationship of carbon dioxide exchanges with temperature and light were used to interpolate missing data during the dormant and part of the growing season.The net ecosystem production of the forest equals 472 g C m−2 y−1 while the gross ecosystem production 1016 g C m−2 y−1 and respiration 544 g C m−2 y−1. These estimates are compared with the net primary production determined by direct biomass sampling which amounts to 802 g C m−2 y−1.
A feasible Global Carbon Cycle Observing System: a plan to decipher today's carbon cycle based on observations
Authors: TANS PIETER P. , BAKWIN PETER S. , GUENTHER DOUGLAS W. 
Published: April 2006

AbstractA design is presented to continuously monitor the transfers of carbon between the atmosphere and the terrestrial biosphere and oceans on large spatial scales. A consideration of the expected signal‐to‐noise suggests that a very cost effective method is to perform repeated measurements of the mixing ratios of trace gases in the atmospheric column at an increased number of sites compared to the present geographical coverage. This can be accomplished with existing technology, provided that more automation is applied to the sampling process as well as to the analytical procedures. The resulting data will be crucial to test extrapolations based on direct flux measurements to regional and global scales.
Effects of enhanced UV‐B radiation on pea (Pisum sativum L.) grown under field conditions in the UK
Authors: MEPSTED R. , PAUL N.D. , STEPHEN J. , CORLETT J. E. , NOGUÉS S. , BAKER N. R. , JONES H. G. , AYRES P. G. 
Published: April 2006

AbstractA new modulated lamp system is described. This system has successfully provided an ultraviolet‐B (UV‐B) supplement in proportion to ambient UV‐B. The modulated system was used to simulate the UV‐B environment resulting from an annual mean reduction of 15% in the stratospheric ozone under UK field conditions, but taking account of seasonal variation in depletion. The effects of this enhanced level of UV‐B on the growth, physiology and yield of four cultivars of pea were assessed.Enhanced UV‐B resulted in small reductions in the number of stems and total stem length per plant (respectively 4.7 and 8.7%). There were also significant decreases in the dry weight of peas (10.1%), pods (10.3%) and stems (7.8%) per plant. UV‐B treatment had no effect on the number of peas per pod or average pea weight, but did significantly reduce (12.1%) the number of pods per plant. This decrease in pod number was partly due to enhanced abscission of pods during the final month of plant growth. UV‐B treatment had no significant effect on chlorophyll fluorescence characteristics or CO2assimilation rate per unit leaf area. These results are consistent with previous controlled environment experiments, and suggest that reduction in yield may be due to direct effects of UV‐B on plant growth rather than a decrease in photosynthetic capacity per unit leaf area.
Effects of elevated CO2 on model calcareous grasslands: community, species, and genotype level responses
Authors: LEADLEY P. W. , STÖCKLIN J. 
Published: April 2006

AbstractWe investigated the responses of model calcareous grassland communities to three CO2concentrations: 330, 500, and 660 μL L‐1, The communities were composed of six species, Bromus erectus Hudson, Festuca ovina L., Prunella vulgaris L., Prunella grandiflora (L.) Scholler, Hieracium pilosella L., and Trifolium repens L., that are native to the calcareous grasslands of Europe. Genotypic variation in CO2 response was studied in Bromus erectus and Festuca ovina. Plants were harvested after c. 126 days of growth. We found that:

At the community level, there were marginally significant (0.1≥P > 0.05) increases in leaf and litter dry weight with increasing CO2 concentration.
There were significant differences between species in CO2 response, including both negative and positive responses. Prunella vulgaris had a significant negative response; Hieraciunt pilosella and Festuca ovina had significant positive responses; Prunella grandiflora had a marginally significant positive response; and Bromus erectus and Trifotium repens did not have significant responses.
There was significant variation among genotypes in the response to elevated CO2 in Bromus erectus, but not in Festuca ovina.
Based on the observed species‐ and genotype‐level variation in CO2 response of calcareous grassland plants in this and other studies, we speculate that increasing atmospheric CO2 concentrations will alter community structure in calcareous grasslands.
Possible impacts of environmental change on pelagic fish recruitment: modelling anchovy transport by advective processes in the southern Benguela
Authors: SHANNON LYNNE J. , NELSON GREVILLE , CRAWFORD ROBERT J. M. , BOYD ALAN J. 
Published: April 2006

AbstractClimate change may influence pelagic fish by altering advective processes or by changing where fish choose to spawn. Using a simulation model, the effects of altered advection and spatial distribution of spawning by anchovy on recruitment off South Africa were explored. Cape anchovy Engraulis capensis spawn on the region of the Agulhas Bank, south of South Africa. Currents transport eggs and larvae to nursery areas. Transport of eggs and larvae was modelled using a flow field based on averaged Acoustic Doppler Current Profile data, Feasible Scenarious of altered advection were modelled. For modelling purposes, the ocean surrounding South Africa was divided into blocks with dimensions of a quarter‐degree latitude by a quarter‐degree longitude. Acoustically measured distributions of spawner biomass for the years 1986–92 were used to calculate egg production per block. In the model, batches were released from each of these blocks each day of the spawning season. The modelling study indicates that passive transport of young anchovy may account for a substantial proportion of year‐class variability. Model results show that distribution of spawners influences the distribution of young of the year, as well as the number and the location of advective losses across offshore boundaries.