FUNCTIONAL DIVERSITY OF DECOMPOSER ORGANISMS IN RELATION TO PRIMARY PRODUCTION

The term 'biodiversity' is claimed to lack connections to a serious sc ientific background. In this work, we approached the concept of biodiv ersity from a functional point of view by asking: ''At what level of t he ecological organization (species, trophic species/feeding guilds, t rophic levels etc.) should reduction in biodiversity matter to bring a bout visible changes in ecosystem performance?'' We investigate the co ncepts of 'functional diversity' and 'ecosystem performance' in relati on to feeding habits (such as fungivory, detritivory etc.) of soil fau na and plant growth. After analysing the results of a number of microc osm studies, we came into the following conclusions: (i) trophic level diversity has clear impacts on primary production - more so when the number of trophic levels is low; (ii) manipulation of large predators at the top of the food chain had no influence on plant growth, whereas smaller mesostigmatid predators generally showed a negative impact on plant growth and nutrient uptake; (iii) declining species diversity a lters carbon mineralization in heterotrophic systems due to changing i nteractions between trophic levels; (iv) species composition within a functional group can affect biomass production of plants; (v) inclusio n of ectomycorrhizal fungi in model ecosystems may be of fundamental i mportance to understanding the most significant interactions between p rimary producers and organisms in detrital food webs. (C) 1998 Elsevie r Science B.V.