RESOURCE ACQUISITION BY THE MYCELIAL-CORD-FORMER STROPHARIA-CAERULEA - EFFECT OF RESOURCE QUANTITY AND QUALITY

Saprotrophic mycelial-cord-forming basidiomycetes, which extend betwee n organic substrata on the forest floor, exhibit remarkable patterns o f reallocation of biomass and nutrients when encountering new resource s. These have been equated with foraging strategies, and differ betwee n species, resources quality and quantity. Stropharia caerulea occupie s more disturbed sites than the fungi previously examined, and the res ponses of its mycelial foraging systems were investigated non-destruct ively by image analysis. Resource quantity and quality affected extens ion rate, extra-resource biomass production and distribution, as quant ified by box-count fractal dimension. When mycelia grew from 0.5 cm(3) beech (Fagus sylvatica) wood inocula across compressed, non-sterile s oil to 0.06-4 cm(3) uncolonised sterile beech wood ''baits'' extension rate fell after contact with large wood baits but biomass production and mycelial distribution was unaffected. In contrast, extension rates of cord systems grown from 0.15 cm(3) U. dioica rhizome inocula to 0. 1-1.2 cm(3) rhizome ''baits'' were unaffected after contact with equal or larger sized baits, but biomass production rates fell and mass fra ctal dimension increased. Mycelial morphology was affected by inoculum age; systems grown from 84 day old 0.5 cm(3) beech wood inocula took 10 days longer achieving the fractal values of systems developing from 22 day old inocula. Foraging strategies and resource relations of myc elial cord systems are discussed.