Fungal decomposition of attached angiosperm twigs

summary Many fungi commonly isolated (>5% isolation frequency) from dead attached ash ( Fraxinus excelsior L.), beech ( Fagus sylvatica L.) and oak ( Quercus robur L.) twigs were capable of growth at water potentials below – 6 MPa, including Phomopsis spp., Cryptosporiopsis spp., Libertella fraxinea Oganova, Fusarium lateritium Nees. and Aureobasidium pullulans (De Bary) Arnaud. Several of these underwent morphological switches at low water potentials. Growth of almost all basidiomycetes common in dead twigs, including Peniophora spp. and Vuilleminia comedens (Nees.: Fr.) Maire, was inhibited at water potentials below –4 MPa. The ecology of fungi commonly isolated from dead ash twigs was studied in greater detail. All except Peniophora lycii (Pers.) V. Hohn & Litch and L. fraxinea , survived in wood for 1 yr at extremely low water potentials (below − 200 MPa). P. lycii was the only species that grew at low temperatures (<5 °C). Water potential was a major determinant of decay rate. Generally, even at high water potentials, decay by individual fungi over a 1 yr period was limited to 20–30 % dry weight losses. However, at −0.05 and −0.8 MPa P. lycii caused 70 % weight loss, and L. fraxinea caused 50% weight loss at −4.1 MPa (its optimal water potential for decay). At water potentials between −4 and −9 MPa L. fraxinea, Phomopsis platanoidis Died, and unidentified sp. 12 were capable of producing significant lignocellulose decay.