Mycelial foraging by Resinicium bicolor: interactive effects of resource quantity, quality and soil composition.

The mycelial response of the wood-rotting basidiomycete Resinicium bicolor to the nutritional status of its environment, the interactive effects of food base quantity and quality and of soil composition were investigated in trays of forest soil. Effects on mycelial extension, hyphal coverage and mycelial morphology (described by fractal dimensions, D) were quantified. Mycelial extension rate, rate of increase in hyphal coverage and D all increased with increasing inoculum size. Inoculum quality affected development: extension and rate of increase of hyphal coverage were faster when inocula had been originally colonised by cultures growing on malt agar than on water agar, and by inocula colonised for 3 months rather than 12 months. Soil carbon status and/or structure also affected development, with the slowest extension and hyphal coverage occurring on ashed and unamended soils with the lowest carbon status. Morphology was dramatically altered on ashed soils (zero carbon), where extremely crooked cords developed in contrast to relatively straight, occasionally branching cords which formed in non-ashed soils. Results are discussed in relation to fungal foraging.