Review and synthesis

Abstract Studies of trace gases in the atmosphere, their sources, sinks, and mechanisms of transport, have developed rapidly in the last few decades. This has been driven partly by increasing recognition that particular gases are associated with problems such as acidification, eutrophication, and global warming, but also by the developing enthusiasm for multidisciplinary research in which scientists from many disciplines collaborate to explore biological, geochemical, and atmospheric cycles and to understand how human action disturbs such cycles. Major international programs such as the International Biological Program (IBP) and the International Geosphere-Biosphere Program (IGBP) have been very influential in generating and encouraging this new way of working. To answer these complex environmental research questions, scientists have needed to develop new field instrumentation, or at least to modify instruments normally used in the laboratory. Equally, mathematical simulation models are increasingly being used at scales ranging from cellular to global to allow complex computations that would have been unthinkable even a decade ago. The papers in this proceedings illustrate some of the exciting developments taking place in the study of the exchange of trace gases between the atmosphere and the land. They describe new understanding of the processes in soils, plants and the atmosphere that control gases important in the carbon and nitrogen cycles, they summarize new techniques and instrumentation that allow field studies at scales ranging from soil grains to landscapes, and they present results of mathematical models that allow us to explore consequences of global changes that may yet come.