|Abstracts on Global Climate Change|
Impact of temperature on the arbuscular mycorrhizal (AM) symbiosis: growth responses of the host plant and its AM fungal partner
Heinemeyer, A Fitter, AH
JOURNAL OF EXPERIMENTAL BOTANY 55:396 525-534
The growth response of the hyphae of mycorrhizal fungi has been determined, both when plant and fungus together and when only the fungus was exposed to a temperature change. Two host plant species, Plantago lanceolata and Holcus lanatus, were grown separately in pots inoculated with the mycorrhizal fungus Glomus mosseae at 20/18degreesC (day/night); half of the pots were then transferred to 12/10degreesC. Plant and fungal growth were determined at six sequential destructive harvests. A second experiment investigated the direct effect of temperature on the length of the extra-radical mycelium (ERM) of three mycorrhizal fungal species. Growth boxes were divided in two equal compartments by a 20 mum mesh, allowing only the ERM and not roots to grow into a fungal compartment, which was either heated (+8degreesC) or kept at ambient temperature. ERM length (L-ERM) was determined on five sampling dates. Growth of H. lanatus was little affected by temperature, whereas growth of P. lanceolata increased with temperature, and both specific leaf area (SLA) and specific root length (SRL) increased independently of plant size. Percentage of colonized root (LRC) and L-ERM were positively correlated with temperature when in symbiosis with P. lanceolata, but differences in LRC were a function of plant biomass. Colonization was very low in H. lanatus roots and there was no significant temperature effect. In the fungal compartment L-ERM increased over time and was greatest for Glomus mosseae. Heating the fungal compartment significantly increased L-ERM in two of the three species but did not affect LRC. However, it significantly increased SRL of roots in the plant compartment, suggesting that the fungus plays a regulatory role in the growth dynamics of the symbiosis. These temperature responses have implications for modelling carbon dynamics under global climate change.
Spatial and temporal shifts in stable isotope values of the bottom-dwelling shrimp Nauticaris marionis at the sub-Antarctic archipelago
Pakhomov, EA McClelland, JW Bernard, K Kaehler, S Montoya, JP
MARINE BIOLOGY 144:2 317-325
Spatial and temporal dynamics of carbon and nitrogen stable isotope signatures of the bottom-dwelling caridean shrimp Nauticaris marionis were measured during April and May between 1984 and 2000 in the vicinity of Marion Island (the Prince Edward Islands, Southern Ocean). There was one trophic-level enrichment in bulk delta(15)N and delta(13)C signatures between small (<20 mm long) and large (>20 mm) specimens of N. marionis, suggesting distinct trophic differentiation among major shrimp size groups. Both delta(15)N and delta(13)C values of N. marionis increased with the depth, reflecting changes in their diet. There were no clear temporal trends in bulk delta(15)N signatures of N. marionis. However, compound-specific delta(15)N measurements of amino acids indicated that N. marionis from the inter-island realm occupied the trophic level of second order carnivores, while similarly sized shrimps in the near-shore realm were at the trophic level of first order carnivores. Compound-specific measurements also identified a change in the source of inorganic nitrogen at the base of the food web between the inter-island and near-shore realms. In contrast to the bulk delta(15)N values, a significant shift in bulk delta(13)C values of N. marionis was observed between 1984 and more recent years. This temporal change appears to be linked to changes in the overall productivity of the Prince Edward Island inter-island system, which could be linked to global climate change.
Greenhouse gas reduction and primary energy savings via adoption of a fuel cell hybrid plant in a hospital
Bizzarri, G Morini, GL
APPLIED THERMAL ENGINEERING 24:2-3 383-400
The Kyoto agreement, expressing great concern about global climate change, has stated emissions of greenhouse gases, especially CO2 from fossil fuel use, need to be reduced. According to this, existing plants have been required to cut emissions; moreover, there has been a greater emphasis on adopting efficient systems in order to reduce the energy losses. Among high efficiency technologies, fuel cells appear to be the most promising for their high efficiency and their very low environmental impact. This paper first reviews the state-of-the-art of fuel cells systems, then simulates the operation of a hybrid fuel cells plant in a “typical hospital” analysing how it could optimize the hospitals energetic requirements. Hospitals and sanitary structures are normally characterized by considerable energy demands not often suitable with resolute energy retrofit strategies. Both the considerable primary energy savings and the pollutant emissions reduction, achieved upgrading conventional systems to a fuel cell hybrid plant, have the potential to prompt national boards to support their business development, as long as they achieve a consolidated market penetration. (C) 2003 Elsevier Ltd. All rights reserved.
Effects of climate change on population persistence of desert-dwelling mountain sheep in California
Epps, CW McCullough, DR Wehausen, JD Bleich, VC Rechel, JL
CONSERVATION BIOLOGY 18:1 102-113
Metapopulations may be very sensitive to global climate change, particularly if temperature and precipitation change rapidly. We present an analysis of the role of climate and other factors in determining metapopulation structure based on presence and absence data. We compared existing and historical population distributions of desert bighorn sheep (Ovis canadensis) to determine whether regional climate patterns were correlated with local extinction. To examine all mountain ranges known to hold or to have held desert bighorn populations in California and score for variables describing climate, metapopulation dynamics, human impacts, and other environmental factors, we used a geographic information system (GIS) and paper maps. We used logistic regression and hierarchical partitioning to assess the relationship among these variables and the current status of each population (extinct or extant). Parameters related to climate-elevation, precipitation, and presence of dependable springs-were strongly correlated with population persistence in the twentieth century. Populations inhabiting lower, drier mountain ranges were more likely to go extinct. The presence of domestic sheep grazing allotments was negatively correlated with population persistence. We used conditional extinction probabilities generated by the logistic-regression model to rank native, naturally recolonized, and reintroduced populations by vulnerability to extinction under several climate-change scenarios. Thus risk of extinction in metapopulations can be evaluated for global-climate-change scenarios even when few demographic data are available.
Yellow-bellied marmots (Marmota flaviventris) hibernate socially
Blumstein, DT Im, S Nicodemus, A Zugmeyer, C
JOURNAL OF MAMMALOGY 85:1 25-29
Of 14 species of marmots (genus Marmota, Family Sciuridae), only 2, the woodchuck (M. monax) and yellow-bellied man-not (M. flaviventris), have not been reported to be obligate social hibernators. There is one published report of yellow-bellied man-not juveniles hibernating together at a subalpine site, and social hibernation was reported at a single high-alpine site. Solitary hibernation is expected in woodchucks because they do not share burrows during summer, but is unexpected in yellow-bellied marmots, a harem-polygynous species where females may share burrows and have extensive home-range overlap with female kin during summer. We documented emergence patterns in 13 matrilines to determine whether adult marmots hibernate socially. We found that adult males hibernated with 1 or more adult females, and mothers hibernated with their offspring. Therefore, we conclude that yellow-bellied marmots hibernate socially. There is, however, no evidence that suggests that yellow-bellied marmots receive social thermoregulatory benefits from social hibernation. Documenting social hibernation required us to quantify patterns of emergence from hibernation. Throughout our subalpine site, emergence appears to be getting earlier; a result consistent with a previous report based on 1 colony site and which suggests the effects of global climate change are affecting hibernation patterns.
Thinking aloud about trust: A protocol analysis of trust in risk management
RISK ANALYSIS 24:1 169-183
There are two general theories of trust in risk management. One, derived from normative considerations, claims that trust is based on universally applicable factors such as fairness and objectivity. According to the second, social-psychological theory, trust is based on agreement or similarity and is context specific. Although the first theory is normative, it also claims, along with the second, to be a descriptive account of how trust judgments are made. The present study was designed to test the adequacy of these two theories by using a think-aloud procedure to examine the thinking associated with trust judgments in an experimental simulation of a typical risk management context. Contrary to the universalist theory, results supported two hypotheses derived from the social-psychological theory. First, study participants-who read brief policy statements designed to address global climate change-based their trustjudgments on specific forms of agreement, ranging from agreement on the importance of the issue to agreement on values inferred from the policy statement. Second, the extent and depth of participants’ conscious information processing was negatively related to the level of trust. Disagreement and distrust generated more conscious consideration than agreement and trust. These results provide a more detailed understanding than previously available of how trust in risk management is based on local forms of agreement that vary across people, contexts, and time.
The global stationary wave response to climate change in a coupled GCM
Joseph, R Ting, MF Kushner, PJ
JOURNAL OF CLIMATE 17:3 540-556
The stationary wave response to global climate change in the Geophysical Fluid Dynamics Laboratory’s R30 coupled ocean-atmosphere GCM is studied. An ensemble of climate change simulations that use a standard prescription for time-dependent increases of greenhouse gas and sulfate aerosol concentrations is compared to a multiple-century control simulation with these constituents fixed at preindustrial levels. The primary response to climate change is to zonalize the atmospheric circulation, that is, to reduce the amplitude of the stationary waves in all seasons. This zonalization is particularly strong in the boreal summer over the Tropics. In January, changes in the stationary waves resemble that of an El Nino, and all months exhibit an El Nino-like increase of precipitation in the central tropical Pacific. The dynamics of the stationary wave changes are studied with a linear stationary wave model, which is shown to simulate the stationary wave response to climate change remarkably well. The linear model is used to decompose the response into parts associated with changes to the zonal-mean basic state and with changes to the zonally asymmetric “forcings” such as diabatic heating and transient eddy fluxes. The decomposition reveals that at least as much of the climate change response is accounted for by the change to the zonal-mean basic state as by the change to the zonally asymmetric forcings. For the January response in the Pacific-North American sector, it is also found that the diabatic heating forcing contribution dominates the climate change response but is significantly cancelled and phase shifted by the transient eddy forcing. The importance of the zonal mean and of the diabatic heating forcing contrasts strongly with previous linear stationary wave models of the El Nino, despite the similarity of the January stationary wave response to El Nino. In particular, in El Nino, changes to the zonal-mean circulation contribute little to the stationary wave response, and the transient eddy forcing dominates. The conclusions from the linear stationary wave model apparently contradict previous findings on the stationary wave response to climate change response in a coarse-resolution version of this model.
Isotopic estimates of new carbon inputs into litter and soils in a four-year climate change experiment with Douglas-fir
Hobbie, EA Johnson, MG Rygiewicz, PT Tingey, DT Olszyk, DM
PLANT AND SOIL 259:1-2 331-343
Because soil is a major reservoir of terrestrial carbon and a potential sink for atmospheric CO2, determining plant inputs to soil carbon is critical for understanding ecosystem carbon dynamics. We present a modified method to quantify the effects of global climate change on plant inputs of carbon to soil based on C-13:12C ratio (delta(13)C) analyses that accounts for isotopic fractionation between inputs and newly created soil carbon. In a four-year study, the effects of elevated CO2 and temperature were determined for reconstructed Douglas-fir ( Pseudotsuga mensiezii (Mirb.) Franco) ecosystems in which native soil of low nitrogen content was used. The d13C patterns in litter and mineral soil horizons were measured and compared to d13C patterns in live needles, fine roots, and coarse roots. From regression analyses, we calculated the isotopic enrichment in 13C of newly incorporated soil carbon relative to needle and root carbon at 4% and 2%, respectively. These enrichments must be considered when using shifts in soil d13C to calculate inputs of plant carbon into the soil, and are probably a major factor in the progressive enrichment in 13C with increasing depth in soil profiles. Relative to the total carbon in each layer, the proportion of new carbon from recent photosynthate in each soil layer was 13-15% in the A horizon, 7-9% in litter layers, and 4% in the B2 and C horizons. New carbon in the A horizon was estimated at 370 g C m(-2). Carbon concentrations and new carbon in A horizons were correlated (r(2) = 0.78, n = 12), but with a slope of 0.356, indicating that about 36% of net carbon accumulation in the A horizon was from inputs via roots, root exudates or mycorrhizal fungi and 64% of carbon was derived from surface litter decomposition. Under the nitrogen-limited growth conditions used in this study, neither elevated CO2 nor temperature affected soil carbon sequestration patterns.