Biological processes and transformations

The core methodology combines „traditional” methods for water, soil and sediment analysis with stable isotope methods and experimental manipulation in several spatiotemporal scales and modelling. Stable isotopes are work horses of recent ecological and biogeochemical research. We use natural abundance and labelling approaches to trace fate of N and C in terrestrial and aquatic ecosystems and their ecotones. The measurement of stable carbon (δ13C), nitrogen (δ15N) and oxygen (δ18O) isotopes in bulk material and in specific compounds are used in providing a novel insights in modern food web studies [Vander Zanden et al. 2016]. Addition of labelled substrates in combination with biomarker analyses enables direct identification of microbes involved in specific processes and also allows the incorporation of bacteria into food web studies [Boschker & Middelburg 2002]. C and N isotopes are used for determining the origin of organic C in soils, soil and stream water, and sediments. These isotopes are applied in exploration of soil OM stabilisation and mineralization, source partitioning of OM in soil and sediments. Stable isotopes δ2H and δ18O

are used to estimate water residence time in water bodies and in soil, in estimation of runoff pathways, and vegetative water sources [Gaj et al. 2016; Oshun et al. 2016]. The RP1 takes benefit from availability of lysimeters and aquatic mesocosm that allow do ecosystem level manipulation in mesoscale and track necessary fluxes of nutrients and of OM in gas and liquid form which allow complete budget of the nutrients and OM. Mesoscale experiments are supplied by possibility of large scale field experiments where all relevant fluxes are monitored in similar level as in mesoscale. The RP1 in collaboration with all other RPs puts large effort to establish the large scale mesocosms and experimental catchment, the world-wide unique facility, from which also future research of all teams will highly benefit. These experimental approaches are combined with availability of long-term data from several model catchment, part of CZ LTER network which are operated by the members of the SoWa RI. The interpretation and exploration of these data are done by modelling of nutrient and OM fluxes. The MAGIC is the principal modelling tool to explain nutrient fluxes on landscape level.