THE CONTRIBUTIONS OF MYCORRHIZAL FUNGI TO THE DETERMINATION OF PLANT COMMUNITY STRUCTURE

While it is now widely accepted, even by ecologists, that most plants in the majority of ecosystems are infected by mycorrhizal fungi, few e xperiments have been designed to investigate the function of the mutua lism at the community level. Those involved with mycorrhizal research have been largely preoccupied with questions of the mineral, particula rly phosphorus, nutrition of individual plants, while plant community ecologists have too often found it convenient, even when acknowledging the presence of infection, to ignore its possible function in the eco system. This presentation examines a selected number of seminal papers written by plant community ecologists and highlights some of 'the mos t striking mysteries' which they reveal. It describes experiments desi gned to determine whether knowledge of the presence and activity of th e mycorrhizal mycelium can help us to unravel the 'mysteries' which th ey define. It is revealed that by having direct adverse effects upon s eedlings of many 'r' selected species, while at the same time being be neficial, if not essential, to those that are 'K' selected, the activi ties of the mycelium of VA fungi have a direct bearing upon community composition. The extent to which 'turf compatibility' is actually a re flection of the compatibility of plant species with the VA mycorrhizal mycelium is discussed and the possible role of the mycelium in consig ning some species to the ruderal habit is considered. It is concluded that those attempting scientifically to understand, or managerially to manipulate, plant communities, without recognizing the role of the my corrhizal mycelium, do so at their peril, and it is recommended that s cientists involved in research on mycorrhiza extend their vision beyon d the limited horizons which are currently so often defined by conside rations of the phosphorus nutrition of individual host plants.