Abiotic variables effect differential expression of latent infections in beech (Fagus sylvatica)

Effects of temperature and gaseous regimes on development of fungal communities, from latent infections in twigs, branches and stems of European beech (Fagus sylvatica ), were investigated through controlled drying. Hypoxylon fragiforme was identified as a latent invader within the xylem of all orders of host stem and branch material. Explanations for the incongruence of this finding with results from previous experiments are considered. Incubation under an atmosphere of 100% CO2 prevented the growth of the endophytic fungi present, despite drying of the wood. Fungal growth at low temperatures and at low oxygen tensions was less than could be explained through direct effects, and there was evidence for an indirect effect involving active host defence. Elevated temperatures favoured establishment of the early-colonizing ascomycete Biscogniauxia nummularia and the late-colonizing basidiomycete Coniophora puteana, while low oxygen tensions favoured colonization by Trichoderma sp. The ecological significance of these observations is discussed.