Das Projekt "Stratospheric ozone: halogen impacts in a varying atmosphere (SHIVA)" wird vom Umweltbundesamt gefördert und von Universität Heidelberg, Institut für Umweltphysik durchgeführt. Objective: SHIVA aims to reduce uncertainties in present and future stratospheric halogen loading and ozone depletion resulting from climate feedbacks between emissions and transport of ozone depleting substances (ODS). Of particular relevance will be studies of short and very short-lived substances (VSLS) with climate-sensitive natural emissions. We will perform field studies of ODS production, emission and transport in understudied, but critical, regions of the tropics using ship, aircraft and ground-based instrumentation. We will parameterize potential climate sensitivities of emissions based on inter-dependencies derived from our own field studies, and surveys of ongoing work in this area. We will study the chemical transformation of ODS during transport from the surface to the tropical tropopause layer (TTL), and in the stratosphere, using a combination of aircraft and balloon observations together with process-oriented meso-scale modelling. These investigations will be corroborated by space-based remote sensing of marine phytoplankton biomass as a possible proxy for the ocean-atmosphere flux of ODS. From this a systematic emission inventory of VSLS ODS will be established to allow construction of future-climate scenarios. The impact of climate-sensitive feedbacks between transport and the delivery of ODS to the stratosphere, and their lifetime within it, will be studied using tracer observations and modelling. Further global modelling will assess the contribution of all ODS, including VSLS (which have hitherto normally been excluded from such models) to past, present and future ozone loss. Here, the sensitivity of natural ODS emissions to climate change parameters will be used in combination with standard IPCC climate model scenarios in order to drive measurement-calibrated chemical transport model (CTM) simulations for present and future stratospheric ozone; to better predict the rate, timing and climate-sensitivity of ozone-layer recovery.
Das Projekt "Swiss Canopy Project: Dissolved organic matter dynamics in a mature deciduous forest under elevated CO2" wird vom Umweltbundesamt gefördert und von Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft durchgeführt. The exposure of a 100 year-old mixed broadleaf forest to elevated CO2 has little effects on dissolved organic matter. Our results suggest that CO2 enrichment can stimulate initial mineralization and leaching of C from litter by altering its quality, but these effects will be short-term and much smaller than any change in species composition. Rationale: The continued rise in atmospheric CO2 changes ecosystem functioning. Most CO2 enrichment experiments were conducted in young expanding ecosystem, much less is known on the response of older ecosystems. We are measuring DOM cycling within a unique CO2 enrichment study experiment - the Swiss Canopy Project - led by the Institute of Botany, University of Basel (Prof. Körner). Here, a 100 year-old forest with beech, oak, hornbeam, cherry, maple, and linden trees is exposed to elevated CO2 with a so-called Web-Face which was woven into the tree crowns with the help of a crane. The added CO2 is depleted in 13C as compared to normal air, allowing to trace assimilated CO2 through the tree and soil system and to gain insight into soil C cycling. Aims: The objectives of our contribution are (1) to quantify the response of DOM leaching to increasing atmospheric CO2 and (2) to trace the input of recent photosynthates (root exudates, litter) into dissolved organic carbon (DOC) of mature forests. Methods: We are collecting soil solutions under the litter layer and at 5 and 15 cm depth along three transects from un-treated trees to CO2-erniched trees (at 30 locations). We measure concentrations DOC, DON, hydrophobic/hydrophilics, phenolics and d13C signatures. In a lab study, we measured initial C mineralization and leaching rates of DOC, DON and biodegradable DOC from litter of eight tree species from the CO2 enrichment experiments in the deciduous forest and at the treeline. Results: In the field, DOC and DON concentrations were largely unaffected by elevated CO2. The laboratory study indicated that CO2 enrichment of forests can stimulate initial mineralization and leaching of C from litter by altering its quality, but these effects will be short-term and much smaller than any change in species composition (Hagedorn & Machwitz, 2007).
Das Projekt "Effect- and Risk-Assessment of Ozone Air Pollution on Forest Vegetation in Switzerland" wird vom Umweltbundesamt gefördert und von Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft durchgeführt. Many studies investigating the negative impacts of ozone on biomass production and physiological functions have demonstrated the relationships between ozone exposure and reductions in both growth and physiological gas exchange leading to an increasing interest in effects of ozone exposure expressed as a critical cumulative exposure of 10000 ppb hrs above the threshold of 40 ppb (AOT40). Ozone effects on plants, mainly depend on atmospheric transport and stomatal uptake. Thus ozone risk assessments should not only use measured ozone concentrations, but should also account for the influence of atmospheric conditions and soil moisture on stomatal conductance and non-stomatal ozone deposition. Following the Level II approach, this study aims to provide a model to estimate the ozone flux for forest ecosystems throughout Switzerland. Project Aims (2002-2005): 1) Conduct an ozone risk assessment with the development of an ozone deposition model for forest ecosystems based on the existing ODEM (Nussbaum et al., in press) model for crops, 2) The screening and validation of ozone sensitive plant species combined with studies investigating the physiological above- and below-ground plant response under controlled conditions within the validation- and learning center Lattecaldo, 3) The assessment of visible ozone injury in the field, i.e. Level II plots throughout Switzerland and Level I plots in Canton Ticino, applying the UN/ECE ICP-Forests guidelines, and 4) The development of a data bank based web page on visible foliar ozone injury for extension activities. Although these objectives are investigating different aspects within the proposed research, they are complementary and intended to strengthen the collaboration with our national and international partners, working in the field of ozone effects on vegetation. Methods: Within the following three years, we intend to continue and foster the collaboration with our international research partners (USA, Spain, Italy, ICP-Forests, UN/ECE) and to use the different ongoing studies within the Lattecaldo OTC research facility, on the long term monitoring Level II plots, as well as on the Level I plots of the Canton Ticino to approach our objectives. In addition to the previous years, we will emphasize the risk assessment of ozone effects on forest plants by developing an ozone deposition model for forest ecosystems based on the existing ODEM for agricultural areas and in close collaboration with the Swiss Federal Research Station for Agroecology and Agriculture FAL, with METEOTEST, and with international collaborators such as Lisa Emberson and Mike Ashmore (University of York). The main challenge will be to combine the different simultaneous studies in a way to take advantage of synergies.
Das Projekt "Auswirkung erhöhter Ozonbelastung auf die Stabilität des Waldes" wird vom Umweltbundesamt gefördert und von Institut für angewandte Pflanzenbiologie durchgeführt. Untersuchungen des Wachstums und der C-Allokation und C-Speicherung (Zucker, Stärke) in Spross und Wurzeln bei Buchen und Fichten unter gleichzeitig erhöhter O3- und N-Belastung anhand eines epidemiologischen Ansatzes (Gradientenstudie in festen Walddauerbeobachtungsflächen) und von Experimenten (O3-Begasung, N-Düngung). Die aktuelle O3-Belastung in der Schweiz hemmt und die N-Deposition fördert den Zuwachs bei Buchen. Ozon hemmt die C-Allokation vom Spross in die Wurzeln. Die N-Düngung bindet erhöht Kohlenhydrate in den Sprossorganen. Bei gleichzeitiger O3- und N-Belastung resultieren sowohl antagonistische als auch synergistische Effekte.