The biosphere has a significant impact on the composition of the atmosphere. One of the greatest uncertainties of future climate predictions is the impact of anthropogenic activities on the dynamic exchange processes between the atmosphere and the biosphere.

Main objectives of the Biosphere Research Area of IMK-IFU are

• to study the impacts of changes in climate, atmospheric deposition of nutrients/pollutants and land use (Global Changes) on the terrestrial biosphere,
• to quantify global change effects on ecosystem C/N stocks and exchange processes between the terrestrial biosphere, the atmosphere and hydrosphere with a specific focus on C and N trace gases, and
• to understand better the complex feedback mechanisms between the biosphere and atmosphere under changing environmental conditions.

Our aim is to improve our understanding of the biosphere as a system by application of an integrated research approach of process studies, field studies, and process modelling. The data sets gained in the laboratory, at longterm field stations and selected satellite sites are used to develop further, to improve and validate process-based models.

The work focuses on the microbial and plant biological processes and key populations involved in N and C cycling, exchange and storage, and how they are affected by Global Change. The work includes the formation processes of biogenic volatile organic compounds (BVOC), the microbial N and C transformations, the regulation of these processes in dependence of biotic and abiotic environmental factors, and their role in the interactions between the biosphere and atmosphere.

The work encompasses the molecular and biochemical characterization of C and N metabolic pathways, and the highly complex inter- and intraspecific interactions, e.g. between microorganisms and plants, with respect to their co-action within the C and N cycles and, thus, for ecosystem stability and functioning. For this challenge, state-of-the-art methods in molecular biology (e.g. microarrays, genetically modified organisms), stable isotope techniques and mass spectrometry (e.g., LC-IRMS, PTR-MS) are applied.

The work focuses on the detailed analyses and quantification of C and N matter fluxes in natural ecosystems sensitive to changes in climate, land use and management and their exchange of matter with the adjacent compartments atmosphere and pedosphere. Special emphasis is given to long-term observation of environmental parameters in order to get resilient datasets for evaluating Global Change effects on the terrestrial biosphere.

The activities comprise

• the establishment and operation of longterm measuring stations and satellite sites for the determination of the exchange of environmentally important trace substances (CO₂, CH₄, VOC, N₂O, N₂, NO, NO₂) between the pedo-, phyllo- and atmosphere with high temporal and spatial resolution applying chamber and micrometeorological techniques and
• the development/improvement of innovative measuring techniques for the quantification of ecosystem C and N transformations/-fluxes.

The activities concentrate on the development and validation of process-oriented numerical models for the simulation of the coupled ecosystem C and N transformations, the C and N storage and of the C and N exchange between terrestrial ecosystems and the atmosphere and hydrosphere on the basis of the results obtained from the process and field studies. By coupling to geographical information systems the models are applied to

• calculate emission/deposition inventories of environmentally important trace substances, by which the reliability of global and regional climate predictions is improved and a contribution is made to the Kyoto process, and
• provide decision support for adaptation and prevention strategies with regard to greenhouse gas balances and sustainable use of the biosphere, in particular of ecosystems sensitive to changes in climate and use/management (forests, grasslands, savannas, wetlands).