Mycelial responses of Hypholoma fasciculare to collembola grazing: effect of inoculum age, nutrient status and resource quality

The effects of grazing by the collembolan Folsomia candida on mycelial foraging patterns of Hypholoma fasciculare growing from beech (Fagus sylvatica) wood block inocula in trays of non-sterile soil was investigated. The wood inocula differed in size, state of decay (time for which wood has been colonized: 2 yr, 1 yr, 6 and 3 months) and nutrient status (inocula colonized on malt agar or nutrient agar). Mycelia were most luxuriant, had greater hyphal coverage and extended more rapidly from 2 yr old than younger inocula, from 4 cm3 than 1 cm3 inocula, and from inocula colonized on malt extract agar rather than on distilled water agar. Grazing dramatically reduced coverage and extension, especially in the less luxuriant systems characterized by many fine hyphae and fewer mycelial cords. Grazing by collembola often resulted in points of more rapid outgrowth as cords with a fanned margin. Results are discussed in terms of fungal foraging strategies.