The new method 'micromapping' a means to study species-specific associations and exclusions of ectomycorrhizae

Ectomycorrhizae (ECM) are obligate symbiotic associations between higher fungi and most tree species of the temperate and boreal forests, and of some tree families in tropical areas. As the anatomical features of these symbiotic organs are very diverse and suggested to improve tree growth differently efficient, their frequency and natural distribution in the soil, as well as the differentiation and amount of their substrate exploiting extramatrical mycelia, are of special ecological interest. The soil with its heterogeneous assemblage of micro-niches certainly provokes ectomycorrhizal fungi to compete for such micro-sites. We therefore applied the method 'micromapping' to record the ectomycorrhizae in their natural position with the following question in mind: Do indicators exist for an exclusion of or an association with other ectomycorrhizal species or not? Thoroughly excavated and carefully cleaned ectomycorrhizae of the OF horizon of a Picea abies stand were drawn in their natural position on perspex plates of 5 x 5 cm mapping area with ink of different colours. They were afterwards removed and specified. Following scanning of the micro maps, a special computer program was applied to analyse their distribution. ... mehrThe spatial relations of the ECM were calculated according to the 'growing grid method'. The results suggest that the ECM of Russula ochroleuca and Piceirhiza internicrassitunicatihyphis show no common occurrence within short distances. This apparently applies also for Russula ochroleuca in comparison to Piceirhiza cinnbadiosimilis, for Elaphomyces granulatus in comparison to Xerocomus badius, and Lactarius decipiens in comparison to Piceirhiza cinnbadiosimilis. Russula ochroleuca and Xerocomus badius show a rather high value of common occurrence. The same has been found for the combination of Cortinarius obtusus with Piceirhiza internicrassitunicatihyphis and Piceirhiza internicrassitunicatihyphis with Xerocomus badius. However, due to the relatively small number of realisable replications, the standard deviations are high, which is not unusual for rhizosphere studies. The spatial relations of these ECM are compared with their ecologically important features of hydrophoby and hydrophily as well as in consideration of their types of exploration. This method is a useful tool to analyse spatial relations of ECM in the soil. Possible reasons for exclusions and associations of ECM are briefly discussed.