1. Laboratory of Isotope Biogeochemistry, Bayreuth Center of Ecology and Environmental Research (BayCEER) University of Bayreuth 95440 Bayreuth Germany
2. Faculty of Science University of South Bohemia Branišovská 31 370 05 České Budějovice Czech Republic
3. Imperial College London and Royal Botanic Gardens Kew TW9 3DS UK