GLOBAL FOREST SYSTEMS - AN UNCERTAIN RESPONSE TO ATMOSPHERIC POLLUTANTS AND GLOBAL CLIMATE-CHANGE

Forest systems cover more than 4.1 x 10(9) ha of the Earth's land area . The future response and feedbacks of forest systems to atmospheric p ollutants and projected climate change may be significant. Boreal, tem perate and tropical forest systems play a prominent role in carbon (C) , nitrogen (N) and sulfur (S) biogeochemical cycles at regional and gl obal scales. The timing and magnitude of future changes in forest syst ems will depend on environmental factors such as a changing global cli mate, an accumulation of CO2 in the atmosphere, and increase global mi neralization of nutrients such as N and S. The interactive effects of all these factors on the world's forest regions are complex and not in tuitively obvious and are likely to differ among geographic regions. A lthough the potential effects of some atmospheric pollutants on forest systems have been observed or simulated, large uncertainty exists in our ability to project future forest distribution, composition and pro ductivity under transient or nontransient global climate change scenar ios. The potential to manage and adapt forests to future global enviro nmental conditions varies widely among nations. Mitigation practices, such as liming or fertilization to ameliorate excess NOx or SOx or for est management to sequester CO2 are now being applied in selected nati ons worldwide.