THE EMBARRASSMENT OF RICHES - ATMOSPHERIC DEPOSITION OF NITROGEN AND COMMUNITY AND ECOSYSTEM PROCESSES

Anthropogenic sources of nitrogen have exceeded, and will continue to exceed, annual inputs of nitrogen produced by natural processes. Nitro gen enrichment may initiate changes in plant tissue chemistry and micr obial decomposition processes, as well as affecting rates of herbivory , all of which may be expected to result in changes in plant species a ssemblages. individual concepts, such as nitrogen saturation and criti cal load, used to describe the effects of enrichment on soil, communit y, ecosystem processes and species assemblages, cannot accommodate eas ily the range of interactions between nitrogen acid different environm ental processes. A number of approaches need to be used in tandem. Maj or gaps in knowledge are rates of transfer of anthropogenic nitrogen w ithin and between different ecosystems and how these rates affect popu lation dynamics of individual species and trophic relationships. Witho ut this information, predictions of biological effects of enrichment a pe difficult to make.