Influence of decay fungi, construction characteristics, and environmental conditions on the quality of wooden check-dams

Wooden crib dams are widely used for torrent control in mountainous regions. Their life span is limited by geomorphological processes and decay. We examined the species composition and population structures of basidiomycetes in crib dams in the northern Swiss Alps and related the presence of the dominating fungi to specific ecological conditions within such constructions. The most dominant fungi were (in decreasing order) Fomitopsis pinicola, Antrodia serialis, Sistotrema brinkmannii s.1., Gloeophyllum sepiarium, Armillaria cepistipes, and Gloeophyllum odoratum, amounting to 75 percent of all basidiomycetes. Presence of these fungi correlated strongly with the degree of wood deterioration. The decay fungi occurred more frequently on the wings of the dams than on the lateral abutments or on those parts which were constantly covered by flowing water. Correspondingly, decay was most advanced in the wings. Decay of check dams in south facing torrents was more pronounced than in those in channels facing north and decay was more intense in check dams below elevations of 900 m asl. The diameter of the logs, the age of the check dams and the wood species, Norway spruce (Picea abies) or European white fir (Abies alba), did not affect either the degree of decay or the presence of any species of fungi. Most individual mycelia (genets) were small (up to 87 genets of F. pinicola were found on a single dam) and spread of individual thalli to adjacent logs was very rare. The implications of these findings for constructing and maintaining crib dams are discussed.