Fungal diversity in Norway spruce: a case study

The majority of microbes living on forest trees are still unnamed and our k nowledge of their species richness is vague. This paper describes the funga l diversity of the above ground parts of a 61 year old Norway spruce tree l acking visible signs of damage or disease. The problem involved with identi fication of the fungi to named species was circumvented by classifying them into operational chemotaxonomic units (OCTUs) by using their combined fatt y acid and sterol profiles (FAST-profiles). The variation of these units wa s chosen to correspond to a wit-hin-species-variation determined for severa l morphologically defined taxonomic species occurring on Norway spruce. Nin ety-nine OCTUs were identified from 666 fungal isolates obtained. Bacteria were found only occasionally from the inner bark samples (three isolates) a nd from needles (five isolates). Models describing the accumulation of OCTU s against the number of samples taken were used for extrapolation of the to tal number of fungal OCTUs in the above ground parts of the tree. Our resul ts suggest that an undamaged, apparently healthy Norway spruce, harbours in its above ground parts nearly two hundred fungal species. The majority wer e estimated to be needle epiphytes. At the large forest area scale, the spe cies richness may be one order of magnitude higher.