ABUNDANCE OF ARBUSCULAR MYCORRHIZAL FUNGI SPORES AT DIFFERENT NATIVE SITES IN DEPENDENCE ON SEWAGE-SLUDGE APPLICATIONS

Soil samples of different soils from eleven native sites in Hesse (Ger many) with and without sewage sludge treatments were collected. The so ils were examined for heavy metal contents and additionally for spore density of arbuscular mycorrhizal fungi. The sludge applications incre ased the EDTA-soluble heavy metal contents in most soils and predomina ntly in the case of Zn. The differences of metal concentrations betwee n the sites were greater than the variations found from sludge applica tion. Populations of the endophytes in the soils were rather high with spore densities of 31 to 97 per gram of dry soil. The effect of sludg e on the population of spores differed between the habitats. The signi ficant correlations between the density of spores and the organic matt er (r = 0,72) partly explained the higher degree of soilborne endophyt es in some sludge treated soils. At some locations, decreasing mycorrh iza populations occured with sludge fertilisation. A possible explanat ion could be the higher sensitivity of mycorrhiza fungi to heavy metal contents and especially to Zn. The differential results shows specifi c ecological adaptation of mycorrhizal populations.