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This chapter reviews recent scientific information concerning the impacts of increasing UV-B exposure on biogeochemical cycles. This is a broad area of research that deals with the complex and often long term interaction of biological, chemical, and physical processes that control the exchange and recycling of matter and energy at and near the Earth's surface.Various controlled laboratory and field studies over the past four years have provided further evidence that enhanced UV-B radiation can affect biogeochemical cycles. However, there have been no appropriate in situ studies addressing the extent to which biogeochemical cycles have already been affected by ozone depletion. This assessment therefore emphasizes potential effects should ozone continue to be depleted. Our focus is on the effects of enhanced UV on carbon and mineral nutrient cycling in terrestrial and aquatic ecosystems (Figure 1) and on the exchange of radiatively- and chemically-important gases between the biosphere and the atmosphere. More detailed treatments of UV-B effects on terrestrial and aquatic ecosystems appear in Chapters 3 and 4.

Fig. 5.1 Conceptual model illustrating the potential effects of enhanced UV radiation on biogeochemical cycles in freshwater, marine and terrestrial ecosystems. The effects involving living organisms, e.g. reduced plant growth, are species- and/or exposure-dependent.

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