Showing papers by "Potsdam Institute for Climate Impact Research published in 1995"

Modelling present and potential future ranges of some European higher plants using climate response surfaces : The ecologist and environmental history : a British perspective

Abstract: It is hypothesized that the principal features of higher plant distributions at continental scales are determined by the macroclimate. Bioclimate data have been computed on a 50 km grid across Europe. Along with published maps of higher plant distributions based upon the same grid, these data have been used to derive climate response surfaces that model the relationship between a species' distribution and the present climate. Eight species representative of a variety of phytogeographic patterns have been investigated. The results support the hypothesis that the European distributions of all eight species are principally determined by macroclimate and illustrate the nature of the climatic constraints upon each species. Simulated future distributions in equilibrium with 2 x CO 2 climate scenarios derived from two alternative GCMs show that all of the species are likely to experience major shifts in their potential range if such climatic changes take place. Some species may suffer substantial range and population reductions and others may face the threat of extinction. The rate of the forecast climate changes is such that few, if any, species may be able to maintain their ranges in equilibrium with the changing climate. In consequence, the transient impacts upon ecosystems will be varied but often may lead to a period of dominance by opportunist, early-successional species. Our simulations of potential ranges take no account of such factors as photoperiod or the direct effects of CO2, both of which may substantially alter the realized future equilibrium.

Productivity and water use of wheat under free‐air CO2 enrichment

Abstract: A free-air CO2 enrichment (FACE) experiment was conducted at Maricopa, Arizona, on wheat from December 1992 through May 1993. The FACE apparatus maintained the CO2 concentration, [CO2], at 550 μmol mol−1 across four replicate 25-m-diameter circular plots under natural conditions in an open field. Four matching Control plots at ambient [CO2] (about 370 μmol mol−1) were also installed in the field. In addition to the two levels of [CO2], there were ample (Wet) and limiting (Dry) levels of water supplied through a subsurface drip irrigation system in a strip, split-plot design. Measurements were made of net radiation, Rn; soil heat flux, Go; soil temperature; foliage or surface temperature; air dry and wet bulb temperatures; and wind speed. Sensible heat flux, H, was calculated from the wind and temperature measurements. Latent heat flux, λET, and evapotranspiration, ET, were determined as the residual in the energy balance. The FACE treatment reduced daily total Rn by an average 4%. Daily FACE sensible heat flux, H, was higher in the FACE plots. Daily latent heat flux, λET, and evapotranspiration, ET, were consistently lower in the FACE plots than in the Control plots for most of the growing season, about 8% on the average. Net canopy photosynthesis was stimulated by an average 19 and 44% in the Wet and Dry plots, respectively, by elevated [CO2] for most of the growing season. No significant acclimation or down regulation was observed. There was little above-ground growth response to elevated [CO2] early in the season when temperatures were cool. Then, as temperatures warmed into spring, the FACE plants grew about 20% more than the Control plants at ambient [CO2], as shown by above-ground biomass accumulation. Root biomass accumulation was also stimulated about 20%. In May the FACE plants matured and senesced about a week earlier than the Controls in the Wet plots. The FACE plants averaged 0.6 °C warmer than the Controls from February through April in the well-watered plots, and we speculate that this temperature rise contributed to the earlier maturity. Because of the acceleration of senescence, there was a shortening of the duration of grain filling, and consequently, there was a narrowing of the final biomass and yield differences. The 20% mid-season growth advantage of FACE shrunk to about an 8% yield advantage in the Wet plots, while the yield differences between FACE and Control remained at about 20% in the Dry plots.

Carbon balance of bioenergy from logging residues

Abstract: Bioenergy as a substitute for fossil energy is regarded a possibility to reduce the energy related carbon dioxide emissions to the atmosphere, because ‘the carbon, which is set free from biomass combustion, is taken up again by regrowing plants and thus the carbon cycle of bioenergy is closed’, as it is often argued. In a more detailed analysis of bioenergy strategies, two main effects have to be investigated: on the one hand, carbon in fossil fuels is substituted and thus not emitted to the atmosphere, while on the other hand, the use of biofuels might result in a reduction of carbon stored in the biosphere (plants, litter and soil). One of the possibilities to use biomass for energy is to burn logging residues from conventional forestry for heat and/or power production. For this type of bioenergy strategy, a model has been developed which allows one to calculate the change in carbon storage in three soil carbon pools and the carbon fluxes to and from these pools. The model results indicate that the carbon stored in the forest soil is reduced when logging residues are removed for bioenergy to displace fossil fuels. However, this effect is limited, as eventually a new equilibrium of carbon storage in the forest soil is reached, while fossil fuel substitution is continued further on. The time-dependent characteristic value ‘carbon neutrality’ (CN), which is the ratio of net emission reduction (fossil fuel substitution minus carbon losses of the soil) to the ‘saved’ carbon emissions from the substituted reference energy system, reflects this effect. CN equal to one means that bioenergy is completely ‘CO2-neutral’. For bioenergy from logging residues, CN is very low at the beginning when bioenergy is introduced, increases continuously and approaches one at infinity. According to the results of parameter studies, CN of bioenergy from logging residues in temperate and boreal forests lies between 0.49 and 0.82 after 20 years and between 0.75 and 0.88 after 100 years.

River flooding in Germany: Influenced by climate change?

Abstract: The debate over whether the recent floods in Germany were partly generated or aggravated by anthropogenically caused changes of the climatic system, of vegetation and land-use or of the river systems was the occasion for the German Science Foundation to initiate an expert meeting to discuss the existing knowledge about “Flooding and its Links to Global Changes”, the results of which form a basis of this paper. Climatic change is mainly affecting the meteorological conditions and — to a lesser extent — the situation of the catchment surface, such as vegetation and soil conditions. The state of the river system and the damage potential in the catchment are not affected by climatic changes. Discussing the rainfall-runoff processes causing floods requires the distinction of different space and time scales: high intensity, locally restricted rainfall events (thunder storms), and long lasting rainfall, covering large areas. Quantitative general statements about the changes of flooding risk due to climatic change are hardly possible. One has to deal with a very complex, highly nonlinear and space-time variable system which is exposed to the natural driving forces topography, soil, vegetation, climate, ground water level and river conditions. The current knowledge of climatic change effects on river flooding in Germany is summarised. The paper ends with an overview of open questions and research needs.

Coupling global models of vegetation structure and ecosystem processes

Abstract: Many currently available biogeochemical ecosystem process models capture the essential processes of trace gas fluxes between atmosphere and ecosystems, as well as the associated changes in net primary productivity. When used in climate change impact scenarios, one of the most serious limitations of these models is due to the fact that the structure of the ecosystem itself is prescribed from a global data base. Significant shifts of the major biomes of the globe are likely to occur under changed climatic conditions, and, hence, the assumption of stable ecosystem structure could fail. To overcome this problem, we have coupled an ecosystem structure model (BIOME) with a biogeochemical ecosystem process model (the Frankfurt Biosphere Model, FBM). Here we present results for high-latitude ecosystems. The coupled model has an average npp of 343.4 g C m -2 a -1 . The application of the coupled model under a GCM based scenario of changing temperature and precipitation results in major changes of the biome boundaries at these high latitudes. The resulting average npp decreases by 8.8%. If the model is run with changed climate but unchanged biome distribution the average npp decreases by 5.4% only. DOI: 10.1034/j.1600-0889.47.issue1.20.x

Possible impacts of global warming on tundra and boreal forest ecosystems - comparison of some biogeochemical models

Abstract: Global warming affects the magnitude of carbon, water and nitrogen fluxes between biosphere and atmosphere as well as the distribution of vegetation types. Biogeochemical models, global as well as patch models, can be used to estimate the differences between the mean values of annual net primary production (NPP) for present and for future climate scenarios. Both approaches rely on the prescribed pattern of vegetation types. Structural, rule-based models can predict such patterns, provided that vegetation and climate are in equilibrium. The coupling of biogeochemical and structural models gives the opportunity of testing the sensitivity of biogeochemical processes not only to climatic change but also to biome shifts. Whether the annual mean NPP of a vegetation type increases or decreases depends strongly on the assumptions about a CO2 fertilization effect and nitrogen cycling. Results from our coupled model show that, given that direct CO2 effects are uncertain, (i) average NPP of these northern biomes might decrease under global warming, but (ii) total NPP of the region would increase, due to the northward shift of the taiga biome.

Domestic Politics and European Acid Rain Regulation

Abstract: International environmental regulation can be conceptualized as reactions of national governments to international pollution exchange and domestic political processes. While there has been a proliferation of theories and studies of the impact of pollution on a country’s preferences for international environmental regulation (see below), very little is known about the domestic political processes which are associated with the regulation of the international environment. The purpose of this article is to contribute to filling this gap in social science knowledge on the protection of the international environment.

Reaktionen und thermisches Verhalten oxofreier Vanadium(IV)-Komplexe. Kristallstrukturen von Methoxo-oxo[thenoyltrifluoraceton-salicylhydrazonato(2−)]vanadium(V) und Methoxo-oxo[benzoylaceton-salicylhydrazonato(2−)]vanadium(V)

Abstract: Die Bestandigkeit oxofreier Vanadium(IV)-Komplexe mit dreizahnigen diaciden Liganden in Dichlormethan/Methanol/Wasser wurde UV/VIS-spektroskopisch untersucht. Als Reaktionsprodukte wurden Methoxo-oxo-[thenoyl-trifluoraceton-salicylhydrazonato(2–)]vanadium(V) sowie Methoxo-oxo-[benzoylaceton-salicylhydrazonato(2–)]vanadium(V) isoliert und rontgenstrukturanalytisch charakterisiert. Das thermische Verhalten der oxofreien Vanadium(IV)-Komplexe wurde analysiert. Methoxo-oxo-[thenoyltrifluoraceton-salicylhydrazonato(2–)]-vanadium(V), Raumgruppe P21/a2, Z = 4, 3 124 beobachtete unabhangige Reflexe, R = 0,0579, Gitterabmessungen bei 25°C; a = 800,0(2) pm, b = 2 027,3(6) pm, c = 1 165,0(3) pm, β = 109,03(2)° Methoxo-oxo-[benzoylaceton-salicylhydrazonato(2-)]vanadium(V) Raumgruppe P21/c, Z = 4, 2 312 beobachtete unabhangige Reflexe, R = 0,031, Gitterabmessungen bei 25°C: a = 1 122,6(1) pm, b = 772,96(9) pm, c = 2 021,2(4) pm, β = 95,32(1)°. Reactions and Thermal Behaviour of Nonoxo Vanadium(IV) Complexes. Crystal Structures of Methoxo-oxo[thenoyltrifluoroacetone-salicylhydrazonato(2–)]vanadium(V) and Methoxo-oxo[benzoylacetone-salicylhydrazonato(2–)]vanadium(V) The persistence of non-oxo vanadium(IV) complexes in dichlormethane/methanol/water solutions was studied by UV/VIS spectroscopy. The reaction products methoxo-oxo-[thenoyltrifluoroacetone-salicylhydrazonato(2–)]vanadium(V) and methoxo-oxo[benzoylacetone-salicylhydrazonato(2–)]vanadium(V) were isolated and characterized by X-ray analysis. The thermal behaviour of non-oxo vanadium(IV) complexes was checked.

Continuing occurrence of eosinophilia myalgia syndrome in canada

Abstract: Eosinophilia myalgia syndrome (EMS), was defined by the Centers for Disease Control (CDC) as eosinophilia > 1000 mm3 and incapacitating myalgia without infection or neoplasm. Studies suggested that use of L-tryptophan (L-T), was a risk factor. We conducted a pharmacoepidemiological survey in Canada where access to L-T is limited. Using the active surveillance method, a 100% sample of potentially involved specialists and a 15% sample of family physicians from Ontario and Quebec were surveyed regarding treatment of patients with severe myalgia within the past year. Follow-up amplified clinical and laboratory information. Overall response rates were 61.4%. Thirty-eight per cent of respondents reported at least one patient. Of 6423 patients assessed, 19 'definite' and 25 'possible' EMS cases were identified. Information from physicians did not suggest use of L-T in patients with definite or possible EMS. It was considered that the cases found an underestimate of the incidence of EMS. Its continuing occurrence in Canada brings causal interpretations of earlier studies into question.