Das Projekt "Alpine treelines in a CO2-rich and warm world" wird vom Umweltbundesamt gefördert und von Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft durchgeführt. We are experimentally increasing atmospheric CO2 concentrations (+200 ppm) and temperatures (+3K) at the alpine treeline and study the response of plant growth and soil processes. First results indicate that elevated CO2 rather affects the cycling rates than C pools in plants and soils. Rationale: The strong increase in atmospheric CO2 has changed ecosystems either directly through the CO2-effects on plant growth or indirectly through its impact on temperatures. It is likely that high altitude soils will respond particularly sensitive to the ongoing climatic changes. The temperature sensitivities of most biogeochemical processes are greater in the lower temperature range. Since alpine and montane soils contain great pools of labile C they play an important role in the response and feedbacks of the overall ecosystems C balance to the changing climate. Aims: to identify how and why does tree growth change to the increasing temperatures and CO2. to estimate how the climatic changes affects the concurrence between trees, dwarf shrubs, and grasses. to quantify the response of soil C fluxes (soil respiration, DOC leaching, accumulation in different SOM pools). to estimate the response of soil microbial community. to elucidate if the new plant-derived rapidly cycling soil C fraction or the older slower cycling soil C fraction responds more sensitive to climatic warming. to estimate if warming alters the partitioning of recent assimilates between plants and soils.
Das Projekt "The role of plant-soil-microbe interactions in the cycling of nitrogen in floodplains" wird vom Umweltbundesamt gefördert und von Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft durchgeführt. This project is part of the large multidisciplinary CCES project RECORD (Assessment and Modeling of Coupled Ecological and Hydrological Dynamics in the Restored Corridor of the River Thur). It deals with the role of microbial transformations and plant uptake in the cycling of nitrogen in different functional processing zones of a restored section of river Thur. The results will help to gain a better understanding of the filter function of restored river corridors and of their potential to emit greenhouse gases. Main hypothesis: Nitrogen fluxes and transformations in floodplains strongly depend on the specific response of microorganisms and dominant plants in different functional processing zones to the hydrologic conditions that vary with season and flooding events. Objectives: At the example of a restored section of river Thur, we want to gain a better insight into the role of riparian systems as sink or source of nitrogen species and the potential risks for drinking water sources and atmosphere. Specific objectives: - quantify the rates of microbial nitrogen transformations within the model floodplain: comparison between different functional processing zones, temporal variations due to seasonal climatic and biological effects and flooding events, dependence on governing soil parameters (temperature, moisture, redox potential). - quantify the rates of nitrogen species uptake by model plants (Phalaris arundinacea, Salix alba): potential uptake depending on nutrient availability and nutrient balance; effects of plant age and and temporary flooding. - measure and model nitrogen species concentrations in the soil solution and nitrous oxide emissions: comparison between different functional processing zones, temporal variations due to seasonal climatic and biological effects and flooding events. Methods: - Sampling and monitoring plots with a diameter of 8m have been set-up in different functional processing zones: (i) pasture in a neighboring non-restored section, (ii) river-forest transect including weakly colonized gravel, gravel covered by fine over-bank material densely overgrown with reed grass (Phalaris arundinacea) and other herbaceous species, zone planted with willow (Salix alba) during the restoration, mixed deciduous forest dominated by ash, (iii) old riparian willow forest. - Microbial nitrogen transformation rates are determined from soil samples taken from within the plots at specific times. Mineralisation immobilisation turnover (MIT) is determined by isotopic dilution, potential denitrification by acetylen-inhibition incubation. - Specific nitrate and ammonium uptake rates by model plants are determined in hydroponic treatments in the climate chamber. - Soil respiration and trace gas efflux/influx is measured by in-situ gas sampling from within large rings permanently installed on the plots followed by GC analysis. Etc.
Das Projekt "Critical Limits and Effect Based Approaches for Heavy Metals" wird vom Umweltbundesamt gefördert und von Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft durchgeführt. Heavy metals are emitted in the atmosphere by industrial activities, transported through long distances, they deposit and accumulate in terrestrial ecosystems. The problem of Long-Range Transboundary Air Pollution of Terrestrial Ecosystems (LRTAP) includes cadmium (Cd), mercury (Hg) and lead (Pb) and are priority metals in the United Nations / Economic Commission for Europe (UN/ECE) Convention from 1998. Increased accumulation of Cd, Hg and Pb from anthropogenic and geogenic sources in soils especially of forest soils has led to exceedances of the current guide values defined by the environmental legislation. Especially, Hg as a global pollutant is of high ecotoxicological concern. However, little information is available on rates of atmospheric deposition, distribution, mobility of Hg compounds (methylmercury) in soils and their transfer functions in the biosphere (bioaccumulation). An impact of current Hg (Cd and Pb) concentrations on the soil ecosystem is possible but still unknown. Aims: This study is part of a comprehensive investigation to determine Hg (Cd and Pb) levels in the soil matrix, soil solution, fungi, earthworms and their food sources (soil, leaf and root litter) and to evaluate the ecotoxicological effects of Hg on the soil microbial communities. What is the current situation of Cd, Hg and Pb in Swiss forest soils? What are the transfer functions of Cd, Hg and Pb from soil to earthworms and mushrooms? Which microbial parameters (microbial activities and/or bacterial community structures) are most suitable to reveal effects of Cd, Hg and Pb on forest soils? Which heavy metal species in soil can be considered as appropriate predictors of Cd, Hg and Pb bioavailability to microbial communities in soils? Which soil bacterial groups are affected by Cd, Hg and Pb? Are the current critical limits for the total dissolved Cd, Hg and Pb, suggested by the UN/ECE, in accordance with the values estimated for Swiss forest soils? Methods: - Determination of reactive heavy metal pool in soil: Water-extractable HM; Heavy metal specific bacterial biosensors (quantification of lux-gene); Modeling of free ions (WHAM 6). - Determination of microbial activity: - Soil respiration; Nitrification; Phosphatase, beta-Glycosidase. - Changes of total bacterial communities: T-RFLP and DGGE fingerprinting of 16S rRNA gene; Cloning and sequencing; Design of specific primers for detecting HM tolerant bacterial groups.