Atmospheric Nitrogen - Pollutant or Fertiliser?

The nitrogen cycle operates on a pan-continental scale, and the issues concerned with maintaining homeostasis are global (Thomas 1998). Nature functions as a balancing act. Human activities disrupt this balance by uncoupling the availability of N from the users of N, both temporally and spatially. Longdistance transport of N from industrial, agricultural and densely populated conurbations has the potential to transform biological communities in remote areas that have evolved under low N availability, through eutrophication. Locally the increasing intensity of farming activities can pollute forests within close proximity. This chapter is concerned with the effects of human manipulation of the N cycle on forest productivity and vitality, and on the environmental conditions that modify the impact of N.