STUDIES OF PATHOGENIC AND ANTAGONISTIC MICROFUNGAL POPULATIONS AND THEIR POTENTIAL INTERACTIONS IN THE MYCORRHIZOPLANE OF NORWAY SPRUCE (PICEA-ABIES (L.) KARST.) AND BEECH (FAGUS-SYLVATICA L.) ON ACIDIFIED ANDLIMED PLOTS

Recent tree decline was hypothesized to be connected to root damage ca used by soil acidification and increased frequency of pathogenic root colonizing fungi. The rhizoplane is constituted by the mycorrhizal she ath and a high diversity of microfungi, some of which are known to beh ave antagonistically against pathogens. Disturbance of the balance bet ween pathogens and antagonists by soil acidification may endanger the health of tree roots. Liming may stabilize the interactions. The micro fungal populations connected to the mycorrhizoplane of Norway spruce ( Picea abies) and beech (Fagus sylvatica) were, therefore, investigated on experimental Norway spruce plots that had been treated with acidif ied water or were limed. Beech presented the original forest and was l eft untreated. Eight microfungal species known as either pathogenic or antagonistic, Trichoderma viride, T. hamatum, T. polysporum, Cylindro carpon destructans, Sesquicillium candelabrum, Mycelium radicis atrovi rens, Tolyplocladium geodes and Oidiodendron maius, were isolated from the mycorrhizoplanes and their abundance in the five different plots compared. Acidification enhanced the frequency of Mycelium radicis atr ovirens and Oidiodendron maius but reduced Trichoderma viride. Liming promoted Sesquicillium candelabrum and Cylindrocarpon destructans. Det ailed analysis of the population patterns indicated that changes in th e frequency of a particular fungal species may not only be caused by s hift of chemical soil factors but also by antagonistic interactions be tween the microfungi, thus reducing pathogenic attacks on rootlets.