Das Projekt "Why are climbing plants so invasive? - an experimental and biomechanical approach to study enhanced growth and competitiveness of climbing plants in the context of CO2 enrichment." wird vom Umweltbundesamt gefördert und von Universität Zürich, Institut für Pflanzenbiologie durchgeführt. Our current understanding of the ecology of lianas and their role in natural ecosystems falls well behind that of most of other plant groups. This gap in current knowledge has potentially serious consequences because (1) climbing plants are known to show significantly enhanced growth under CO2 enrichment (2) many climbing plant species are serious invasive elements in both tropical and temperate ecosystems and cultivated areas and (3) recent censuses of tropical lianas suggest that recent changes in climbing plant growth dynamics might be actually changing vegetation communities in the tropics. These issues therefore beg for detailed studies on the effects of CO2 enrichment on invasive climbing plants. The main aim of this study was to analyse the effects of elevated CO2 concentration on the development, biomass and mechanical properties of two selected invasive climbing species (Ipomoea triloba, Momordica charantia) and an agricultural C4 host plant (Sorghum bicolor) with a new approach on the interface of biophysics and ecophysiology. We investigated a) the effect of elevated CO2 on sorghum without climbers, b) the effect of elevated CO2 on developmental traits of the two invasive species and c) the effect of elevated CO2 on the interaction and crop/climbing plant competition with the effects on growth and yield. Sorghum bicolor plants were grown with two invasive climbing species under ambient (380 ppm) and elevated CO2 (750 ppm) in glasshouse conditions. The results are summarized in three main articles in preparation: First, Sorghum grown alone showed significant differences in biomass allocation between ambinet and elevated CO2, particularly between vegetative and reproductive components and a significant decrease in yield under elevated CO2. In terms of mechanical architecture sorghum plants grown without climbers showed no change in the stiffness of the leaf sheath at elevated CO2 despite increases in vegetative biomass. Second, both liana species showed changes in mechanical, morphological and photosynthetic traits under elevated CO2 resulting in enhanced growth (length + branching). Third, the results from the crop/climbing plant competition experiment demonstrated that the sorghum host plants are more affected under elevated CO2 than ambient CO2 leading to a weakened mechanical architecture and a decrease in panicle biomass and stem carbohydrate production. The results of this study provide fundamental knowledge for the effects of climate change on weed/crop competition and liana growth. Elevated CO2 can potentially increase the invasive climber threat for crops in future which should be taken in account for agricultural management.
Das Projekt "Gasaustausch in Aesten erwachsener Nadelbaeume im subalpinen Bereich, beeinflusst durch erhoehte CO2-Konzentration in der Luft" wird vom Umweltbundesamt gefördert und von Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft durchgeführt. Over several years, photosynthesis and transpiration in shoots of mature coniferous trees at natural subalpine sites (Seehornwald and Stillberg, Davos) have been measured using thermoelectrically climatized gas exchange chambers with different CO2 concentrations (ambient and ambient + 350ppm CO2). Maximum photosynthetic capacity of the shoots has been estimated periodically. In addition to the gas exchange measurements at ambient CO2 concentration, past measurements, taken at the same places, will serve as controls. Leading Questions: Are the photosynthetic rates of mature coniferous trees different at elevated CO2 concentrations? Are there changes in the water relations (transpiration, stomatal conductance) of shoots of mature coniferous trees exposed to elevated CO2 concentrations? In short-term experiments with elevated CO2 concentration, an increase in CO2 assimilation is observed. Is there, with time, an adaptation back to the present photosynthetic rates? Is the temperature optimum in shoots grown under elevated CO2 concentration different?