XVI International Botanical Congess

Through the emission of a great variety of trace gases the biosphere has a large impact on the chemistry of the atmosphere. Large emission of non-methane hydrocarbons (NMHC), especially isoprene from tropical forests, lead to a lowering of hydroxyl (OH) and ozone concentration, not only regionally but also via production of more long-lived CO, over much larger regions of the background troposphere, which contain only little of NO and NO2. In regions which are affected by air pollution (industrial or biomass burning), the emission of NO, on the other hand will cause ozone and hydroxyl concentrations to increase. Altogether, current model calculations indicate that natural NMHC emissions cause a reduction in the oxidizing power of the atmosphere, that is a lowering of a globally averaged OH radical concentrations.