Effects of wood mixtures on deterioration by a filamentous brown-rot fungus

Wood-degrading fungi import elements to meet physiological demands in wood, but little is known about interactions with different wood types. This is despite increased use of wood composites, in which durability can be tested but not well predicted. Blocks of nondurable aspen and spruce and moderately durable eastern white pine were degraded using the brown-rot fungus Gloeophyllum trabeum in soil- and agar-block microcosms for 16 wk. Block configurations were either a single species (monosubstrate) or mixed (polysubstrate). At 8 and 16 wk, total wood weight losses were the same in monosubstrate and polysubstrate microcosms; however, white pine degradation was consistently less in polysubstrates than in monosubstrates with decay in aspen and spruce compensating to achieve equal overall weight loss. Nondegraded pine had higher extractives and lower nitrogen levels as compared with the other woods. Carbon fractions and cation contents in degraded pine were typical of brown rot, suggesting the fungus reallocated resources to less durable aspen and spruce when given the option. Data demonstrate that wood durability can be influenced significantly by other wood types. Although this could influence the spatial pattern of decay in mixed materials, overall durability in small-particle size wood composites may also be predictable based on single-species performance.