Surface Area of Wood Influences the Effects of Fungal Interspecific Interaction on Wood Decomposition-A Case Study Based on Pinus densiflora and Selected White Rot Fungi.

Wood decomposer basidiomycetes are the major agents of lignocellulose decomposition in dead wood. As their interspecific interaction affects wood decomposition, difference in interaction area may alter the magnitude of the effects. This study examines the effects of wood surface area on decomposition by interacting basidiomycetes using laboratory incubation experiments with pine sapwood as a model. Two types of pine wood blocks with equal volume but identical surface area were prepared for colonization by one of four white rot basidiomycete species. The colonized wood blocks were then placed on agar media already colonized by the same strain or one of the other species, simulating fungal monoculture and interspecific interactions on wood surface. Results demonstrated that the decay rate of wood was greater in wood with larger surface, and wood decay was accelerated by the interaction of two fungal species in wood with larger surface but not in wood with smaller surface. In contrast, lignin decomposition was influenced by the competitor in wood with smaller surface but not in wood with larger surface. These results suggest that the observed promotion of decay by fungal interspecific interaction might not be attributable to the resource partitioning between fungal species but to the accelerated carbon of competition cost compensation in this case.

Timing of Resource Addition Affects the Migration Behavior of Wood Decomposer Fungal Mycelia.

Studies of fungal behavior are essential for a better understanding of fungal-driven ecological processes. Here, we evaluated the effects of timing of resource (bait) addition on the behavior of fungal mycelia when it remains in the inoculum and when it migrates from it towards a bait, using cord-forming basidiomycetes. Experiments allowed mycelium to grow from an inoculum wood across the surface of a soil microcosm, where it encountered a new wood bait 14 or 98 d after the start of growth. After the 42-d colonization of the bait, inoculum and bait were individually moved to a dish containing fresh soil to determine whether the mycelia were able to grow out. When the inoculum and bait of mycelia baited after 14 d were transferred to new soil, there was 100% regrowth from both inoculum and bait in Pholiota brunnescens and Phanerochaete velutina, indicating that no migration occurred. However, when mycelium was baited after 98 d, 3 and 4 out of 10 replicates of P. brunnescens and P. velutina, respectively, regrew only from bait and not from inoculum, indicating migration. These results suggest that prolonged periods without new resources alter the behavior of mycelium, probably due to the exhaustion of resources.

Effects of wood resource size and decomposition on hyphal outgrowth of a cord-forming basidiomycete, Phanerochaete velutina.

To assess the relationship between resource use and hyphal growth in a cord-forming basidiomycete, Phanerochaete velutina, soil microcosm experiments were conducted using wood blocks of three different sizes in three different soil quantities, thereby simulating the different amounts of available nutrients. The highest percentage weight loss was observed in the smallest wood blocks after a 27-d incubation period in soil microcosms, although the percentage weight loss over the 2-month pure culture colonization prior to inoculation was not significantly different among various block sizes. The greatest hyphal outgrowth was also observed in the smallest wood blocks and was positively associated with wood decay. The slopes of the regression lines between hyphal coverage and percentage wood mass loss were identical among different wood sizes, but the slopes between hyphal coverage and absolute wood mass loss were steeper in the smaller wood blocks than that in largest one. These results suggest that the level of intensity of mycelial foraging for new resources in the soil depends on the percentage of the amount of wood resource utilized, and not on the absolute amount of carbon obtained from the wood.