This thesis is concerned with trace gas flux in tundra environments, the main subject of study being methane. Methane emission from tundra soils has in recent years attracted increasing attention due to the possible associated feed-back effect on man-made climate change. The presented data are primarily produced. during field work in Northern Alaska but it also includes work in Northern Sweden and laboratory studies in Copenhagen. Model experiments carried out on basis of the gathered data was carried out in cooperation with the Hadley Centre at the Meteorological Office in England. Chapter 1 describes the area of research and the general background for embarking on the project. It concludes by defining a number of questions which the research presented in the thesis will attempt to answer. The first two chapters in the main body of the thesis (Chapter 2 and 3) fonn an introduction to tundra ecology with emphasis on aspects which are directly related to controls on soil emission of trace gases. It is explained how trace gas balances of tundra soils primarily are climatically controlled. These dependencies form main subjects of study in the thesis. Chapters 4 and 5 contain an analysis of methane emission from tundra environments primaiily based on field work in Alaska and Sweden but also involving laboratory studies of soil cores from a boreal bog. The bulk of the data presented are flux measurements produced using a static chamber technique. Methane and carbon dioxide were also analysed for their isotopic signatures. The scale of methane emission and factors controlling the flux at temporal and spatial scales are investiga!ed and discussed in relation to the info1mation available in the literature. After identifying the controlling factors most useful as tools for predicting methane emission the thesis moves on to describe an attempt to model seasonal variations in flux at the main tundra site investigated (Chapter 6). This model forms prut of the Meteorological Office climate prediction programme. The model is used in a number of climate change experiments in order to assess the possible feed-back effect from tundra methane emission following different climate change scenarios. Finally a simultaneous multigas analysis of carbon dioxide, methane, nitrous oxide and carbon monoxide flux in a tundra environment is described (Chapter 7). This forms basis for a discussion of the potential for the tundra to play a significant role in the atmospheric budgets of these gases. In a concluding chapter the questions defined in Chapter 1 are answered based on the work presented in the six preceding chapters.