INSIGHTS INTO THE DYNAMICS OF FOREST SUCCESSION AND NONMETHANE HYDROCARBON TRACE GAS EMISSIONS

Natural biogenic non-methane hydrocarbon (NMHC) emissions significantl y influence the concentrations of free hydroxyl and peroxy radicals, c arbon monoxide and tropospheric ozone. Present concerns with air pollu tion and the global carbon balance call for a better understanding of the respective roles of climate dynamics and vegetation succession in determining NMHC emissions. This constitutes the focus of the present paper. The approach consists in coupling the Energy, Water and Momentu m Exchange and Ecological Dynamics model, a climatically sensitive, ph ysically based gap phase forest dynamics model, and NMHC trace gas emi ssion algorithms to assess possible changes in NMHC emissions from for ests under stationary and changing climatic conditions. In summary, it is possible to follow the temporal evolution of foliar emissions over centuries using a vegetation dynamics model coupled with an NMHC emis sions module. Significant changes in isoprene and terpene emissions ca n take place as vegetation succession occurs under stationary climatic conditions and as climatic perturbations of the type and magnitude fo reseen for global change alter the local microclimate. As illustrated by two examples, emissions may decrease or increase depending on the l ocal climate and vegetation. The respective actions of changes in spec ies absolute and relative abundance and changes in temperature interac t very non-linearly making changes in emissions difficult to predict. None the less, coupled models of the kind described here may provide u seful insights into the direction of such changes.