The biosphere is substantially involved in the production and consumption of reactive trace gases such as volatile organic compounds, nitrogen oxides and reduced sulphur compounds, thereby significantly contributing to chemical processes in the atmosphere. There are major uncertainties associated with descriptions of the processes controlling surface-atmosphere trace gas exchange on all scales from biological production to primary emissions up to flux measurements on larger scales. Therefore, biological processes and exchange regulations involved in the production and release as well as deposition and consumption of all these compounds are actually under intensive investigation in order to understand and model exchange processes and atmospheric chemistry in a more reliable way. The session is open to all contributions related to aspects of biosynthesis of reactive trace compounds, their consumption and exchange regulation as well as exchange studies at various spatial and temporal scales ranging from enclosure measurements to turbulent flux measurement and boundary layer profiling techniques.