Abstracts on Global Climate Change

Feb 2005

Effect of temperature, elevated carbon dioxide, and drought during seed development on the isoflavone content of dwarf soybean [Glycine max (L.) Merrill] grown in controlled environments

Caldwell, CR Britz, SJ Mirecki, RM


The effects of elevated temperature, carbon dioxide, and water stress on the isoflavone content of seed from a dwarf soybean line [Glycine max (L.) Merrill] were determined, using controlled environment chambers. Increasing the temperature from 18 degreesC during seed development to 23 degreesC decreased total isoflavone content by about 65%. A further 5 degreesC increase to 28 degreesC decreased the total isoflavone content by about 90%. Combining treatments at elevated temperature with elevated CO2 (700 ppm) and water stress to determine the possible consequences of global climate change on soybean seed isoflavone content indicated that elevated CO2 at elevated temperatures could partially reverse the effects of temperature on soybean seed isoflavone content. The addition of drought stress to plants grown at 23 degreesC and elevated CO2 returned the total isoflavone levels to the control values obtained at 18 degreesC and 400 ppm CO2. The promotive effects of drought and elevated CO2 at 23 degreesC on the 6”-O-malonygenistin and genistin levels were additive. The individual isoflavones often had different responses to the various growth conditions during seed maturation, modifying the proportions of the principal isoflavones. Therefore, subtle changes in certain environmental factors may change the isoflavone content of commercially grown soybean, altering the nutritional values of soy products.

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Arctic sea ice trends and narwhal vulnerability

Laidre, KL Heide-Jorgensen, MP


Conservation measures related to global climate change require that species vulnerability be incorporated into population risk models, especially for those that are highly susceptible to rapid or extreme changes due to specialized adaptation. In the case of Arctic cetaceans, effects of climate change on habitat and prey availability have been subject to intense speculation. Climate perturbations may have significant impacts on the fitness and success of this group, yet measuring these parameters for conservation purposes is complicated by remote and offshore preferences. The narwhal (Monodon monoceros) in Baffin Bay occupies a habitat where reversed (increasing) regional sea ice trends have been detected over 50 years. We used a combination of long-term narwhal satellite tracking data and remotely sensed sea ice concentrations to detect localized habitat trends and examine potential vulnerability. Spatial and temporal variability in the fraction of open water were examined on two narwhal wintering grounds between November and April, 1978-2001 using approximate sea ice concentrations derived from microwave SSMR/SSMI passive brightness temperatures. Less than 3% open water was available to narwhals between 15 January and 15 April, and reached minima of 0.5% open water at the end of March (125 km(2) out of a 25,000 km(2) area). Decreasing trends in the fraction of open water, together with increasing trends in interannual variability, were detected on both wintering grounds, significantly in northern Baffin Bay (-0.04% per year, SE 0.02). The limited number of leads and cracks available to narwhals during the winter, in combination with localized decreasing trends in open water and high site fidelity, suggests vulnerability to changes in Arctic sea ice conditions. Increasing risk of ice entrapments, many of which may go undetected in remote offshore areas, should be incorporated into population risk assessments as this may exceed the natural response capacity of the species. (C) 2004 Elsevier Ltd. All rights reserved.

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Terrestrial C sequestration at elevated-CO2 and temperature: The role of dissolved organic N loss

Rastetter, EB Perakis, SS Shaver, GR Agren, GI


We used a simple model of carbon-nitrogen (C-N) interactions in terrestrial ecosystems to examine the responses to elevated CO2 and to elevated CO2 Plus warming in ecosystems that had the same total nitrogen loss but that differed in the ratio of dissolved organic nitrogen (DON) to dissolved inorganic nitrogen (DIN) loss. We postulate that DIN losses can be curtailed by higher N demand in response to elevated CO2, but that DON losses cannot. We also examined simulations in which DON losses were held constant, were proportional to the amount of soil organic matter, were proportional to the soil C:N ratio, or were proportional to the rate of decomposition. We found that the mode of N loss made little difference to the short-term (<60 years) rate of carbon sequestration by the ecosystem, but high DON losses resulted in much lower carbon sequestration in the long term than did low DON losses. In the short term, C sequestration was fueled by an internal redistribution of N froth soils to vegetation and by increases in the C:N ratio of soils and vegetation. This sequestration was about three times larger with elevated CO2 and warming than with elevated CO2 alone. After year 60, C sequestration was fueled by a net accumulation of N in the ecosystem, and the rate of sequestration was about the same with elevated CO, and warming as with elevated CO2 alone. With high DON losses, the ecosystem either sequestered C slowly after year 60 (when DON losses were constant or proportional to soil organic matter) or lost C (when DON losses were proportional to the soil C:N ratio or to decomposition). We conclude that changes in long-term C sequestration depend not only on the magnitude of N losses, but also on the form of those losses.

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Responses of a beaded Arctic stream to short-term N and P fertilisation

Benstead, JP Deegan, LA Peterson, BJ Huryn, AD Bowden, WB Suberkropp, K Buzby, KM Green, AC Vacca, JA


1. Oligotrophic Arctic streams are likely to be sensitive to changes in hydrology and nutrient inputs predicted to occur as a consequence of future climate and land use change. To investigate the potential consequences of nutrient enrichment for low-order Arctic streams, we added ammonium-N and phosphorous to a second-order beaded, tundra stream on Alaska’s north slope. We measured responses in nutrient chemistry, chlorophyll a standing crop, and in the breakdown and macroinvertebrate colonisation of leaf litter over a 38-day summer period. 2. During the addition, nutrient concentrations immediately downstream of the dripper averaged 6.4 mum ammonium-N and 0.45 muM soluble reactive P. Concentrations upstream of the dripper averaged 0.54 muM ammonium-N and 0.03 muM soluble reactive P. Uptake of both nutrients was rapid. Concentrations were reduced on average to 28 % (ammonium-N) and 15 % (inorganic P) of maximum values within 1500 m. Standing crops of chlorophyll a on standardised samplers were significantly higher by the end of the experiment. Breakdown rates of senescent willow (Salix sp.) and sedge (Carex sp.) litter and associated fungal biomass were also significantly increased by nutrient addition. 3. Fertilisation resulted in four- to sevenfold higher macroinvertebrate abundance and two-to fourfold higher macroinvertebrate biomass in litter bags, as well as an increase in late-summer body mass of larval Nemoura stoneflies. 4. Our results are consistent with those of similar studies of larger streams in the high-Arctic region. Based on our short-term experiment, increased inputs of nutrients into these ecosystems, whether caused by climate change or more local disturbance, are likely to have profound ecological consequences. Longer-term effects of enrichment, and their interaction with other components of future change in climate or land use, are more difficult to assess.

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Brazilian energy policies side-effects on CO2 emissions reduction

Szklo, AS Schaeffer, R Schuller, ME Chandler, W

ENERGY POLICY 33:3 349-364

This study focuses on some of the programs and measures Brazil has undertaken over the past two or three decades in order to mitigate economic or environmental problems, which have also had positive effects on the reduction of the country’s carbon dioxide emissions. Results show that, in the year 2000 alone, some 11% in CO2 emissions from energy use in Brazil have been reduced compared to what would have been emitted that year had the actions reviewed here not been implemented in good time. As these actions have not been motivated as a strategy to curb global climate change, if their benefits related to avoided carbon emissions are not fully appraised in the near future, chances are that these policies may be discontinued. For instance, in the case of the business-as-usual scenario drawn up by the Ministry of Mines and Energy in 2001, the discontinuity of the policies analyzed here would result in CO2 emissions 20% higher by 2020, compared to what would happen were these policies kept over the long term. Therefore, the perspective presented here spotlights some of the hidden benefits of the programs and measures underway in the country, justifying their continuation or even intensification. (C) 2003 Elsevier Ltd. All rights reserved.

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Aerosol properties and their spatial and temporal variations over North China in spring 2001

Xia, XA Chen, HB Wang, PC Zong, XM Qiu, JH Gouloub, P


Aerosol properties and their spatial and temporal variations over North China were analysed based on ground- based radiometer data for spring 2001. On the basis of the retrievals from sun/ sky radiance and broad- band radiation measurements at four AERONET stations and eight first- class radiation stations over North China, the analysis comprised a detailed description of aerosol loading, size and absorption in this period. The impact of dust events on aerosol properties over the downwind region was emphasized. Heavy aerosol loading and notable temporal variation over North China were revealed by both datasets. The average aerosol optical depth at 750 nm at the eight radiation stations ranged from 0.32 in Ejinaqi to 0.68 in Beijing, with the averaged coefficient of variation being 70%. Aerosol optical depth was dominantly contributed to by dust over western China, with 68% ( +/- 5%) of aerosol optical depth at 550 nm being attributed to large dust aerosols. A dramatic increase in aerosol optical depth associated with the remarkable decrease in the Angstrom wavelength exponent was observed in Beijing and Xianghe during the dust episode. This indicated that a huge number of large particles were emitted into the atmosphere during the dust period, with the result that the contribution to aerosol optical depth from coarse particles approached the value observed in the dust source region. Anthropogenic pollution also frequently contributed to the high aerosol optical depth in Beijing and Xianghe, but this was characterized by fine particles, with more than 70% of aerosol optical depth at 550 nm being attributed to fine particles. Pure desert aerosol in Chinese dust source regions absorbs much less solar radiation than predicted by known aerosol models. The retrieved single- scattering albedo was around 0.98 ( +/- 0.01) and had little wavelength dependence, which is in agreement with the ground- based and satellite retrievals in other dust source regions. Contrarily, anthropogenic aerosol exhibits much stronger absorption in the urban region, with the single- scattering albedo ranging from 0.89 +/- 0.04 (at 440 nm) to 0.83 +/- 0.05 (at 1020 nm). Due to the large difference in the absorption between dust and anthropogenic aerosol, the consequence of the input of a large volume of dust aerosols is not only to enhance the aerosol loading but also to reduce the aerosol absorption. Retrievals in Beijing showed that the single- scattering albedo increased to about 0.90 and had little spectral dependence when anthropogenic pollution and a dust event together affected Beijing; as for the pure dust period, it ranged from 0.92 at 440 nm to 0.97 at 1020 nm. The significant decrease in the aerosol absorption due to the dust outbreak can result in a decrease in aerosol atmospheric heating efficiency; this warrants further research since the increasing trend of aerosol loading with strong absorption in China is supposed to play an active role in regional and global climate change and the hydrological cycle.

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Effects of carbon markets on the optimal management of slash pine (Pinus elliottii) plantations

Stainback, GA Alavalapati, JRR


Global climate change is a growing concern among many policy makers. This concern has led to substantial interest in using forests as one option to mitigate climate change. In this article, the effect of internalizing carbon sequestration benefits on the optimal management of slash pine plantations is explored. Results suggest that without carbon bene is, it is optimal to use herbicide and bedding but not fertilizer because the increase in timber yield does notjustib7 the high cost offertilizer. With carbon benefits, however, the use of fertilizer becomes profitable. Thus a carbon market would likely induce plantation owners to increase their management intensity, which may in turn also have significant impacts on the amount of carbon sequestered. For example, by allowing the management regime to vary in addition to rotation age, the amount of carbon sequestered decreased from 204 to 164 metric tons of carbon per acre when carbon prices increased from $40 to $200 per metric ton. Thus increasing carbon sequestration on the intensive margin may be less feasible than previously supposed, but increasing on the extensive margin may be highly practicable.

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Interactive effects of carbon dioxide, temperature, and ultraviolet-B radiation on soybean (Glycine max L.) flower and pollen morphology, pollen production, germination, and tube lengths

Koti, S Reddy, KR Reddy, VR Kakani, VG Zhao, DL


Plant reproduction is highly vulnerable to global climate change components such as carbon dioxide concentration ([CO2]), temperature (T), and ultraviolet-B (UV-B) radiation. The objectives of this study were to determine the effects of season-long exposure to treatments of [CO2] at 360 (control) and 720 mumol mol(-1) (+CO2), temperature at 30/22degreesC (control) and 38/30degreesC (+T) and UV-B radiation 0 (control) and 10 W m(-2) d(-1) (+UV-B) on flower and pollen morphology, pollen production, germination, and tube lengths of six soybean genotypes (D 88-5320, D 90-9216, Stalwart III, PI 471938, DG 5630RR, and DP 4933RR) in sunlit, controlled environment chambers. The control treatment had 360 mumol mol(-1) [CO2] at 30/22degreesC and 0 W UV-B. Plants grown either at +UV-B or +T, alone or in combination, produced smaller flowers with shorter standard petal and staminal column lengths. Flowers so produced had less pollen with poor pollen germination and shorter tube lengths. Pollen produced by the flowers of these plants appeared shrivelled without apertures and with disturbed exine ornamentation even at +CO2 conditions. The damaging effects of +T and +UV-B were not ameliorated by +CO2 conditions. Based on the total stress response index (TSRI), pooled individual component responses over all the treatments, the genotypes were classified as tolerant (DG 5630RR, D 88-5320: TSRI >-790), intermediate (D 90-9216, PI 471938: TSRI <-790 to >-1026), and sensitive (Stalwart III, DP 4933RR: TSRI <-1026). The differences in sensitivity identified among genotypes imply the options for selecting genotypes with tolerance to environmental stresses projected to occur in the future climates.

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Effects of water stress and high nocturnal temperature on photosynthesis and nitrogen level of a perennial grass Leymus chinensis

Xu, ZZ Zhou, GS

PLANT AND SOIL 269:1-2 131-139

Water deficit and high temperature are important environmental factors restricting plant growth and photosynthesis. The two stresses often occur simultaneously, but their interactions on photosynthesis and nitrogen level have been less studied. In the present experiment, we measured photosynthetic parameters, stomatal density, and nitrogen levels, as well as soluble sugar content of leaves of a perennial grass, Leymus chinensis, experiencing two day/night temperature regimes of 30/20 degrees C and 30/25 degrees C, and five different soil moisture contents (the soil relative-water content ranged from 80% to 25 %). Leaf relative water content, leaf biomass, whole plant biomass, the ratio between the leaf biomass and total plant biomass, and the photosynthetic rate, as well as water-use efficiency decreased at high night temperature, especially under severe water stress conditions. Stomatal index was also increased by soil water stress except very severe water stress, and high nocturnal temperature decreased the leaf stomatal index under soil water stress. Nocturnal warming decreased nitrogen concentration in the leaves and increased it in the roots, particularly when plants were subjected to severe water stress. There were significant positive correlations between the photosynthetic rate and both soluble sugar concentration and nitrogen concentration at low nocturnal temperature. It is suggested that nocturnal warming significantly exacerbates the adverse effects of soil water stress, and their synergistic interactions might reduce the plant productivity and constrain its distribution in the region dominated by L. chinensis, based on predictions of global climate change.

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Australia-wide predictions of soil properties using, decision trees

Henderson, BL Bui, EN Moran, CJ Simon, DAP

GEODERMA 124:3-4 383-398

This paper describes the construction of Australia-wide soil property predictions from a compiled national soils point database. Those properties considered include pH, organic carbon, total phosphorus, total nitrogen, thickness. texture, and clay content. Many of these soil properties are used directly in environmental process modelling including global climate change models. Models are constructed at the 250-m resolution using decision trees. These relate the soil property to the environment through a suite of environmental predictors at the locations where measurements are observed. These models are then used to extend predictions to the continental extent by applying the rules derived to the exhaustively available environmental predictors. The methodology and performance is described in detail for pH and summarized for other properties. Environmental variables are found to be important predictors, even at the 250-m resolution at which they are available here as they can describe the broad changes in soil property. (C) 2004 Elsevier B.V. All rights reserved.

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