The biosphere is the ultimate sink for air pollutants and is also the source of many precursors for the formation of photo-oxidants. In any analysis of air pollution and for determining source-receptor relationships, reliable emission and pollutant concentrations or depositions must be taken into account, together with their interactions between the atmosphere and the biosphere. This book presents a number of authoritative review articles covering topics which include biosphere-atmosphere exchange of ammonia, nitrogen oxides, ozone and sulfur-containing gases, the biological mechanisms involved in the exchange of trace gases, as well as generalizations of deposition over Europe.