Compensatory growth of Phanerochaete velutina mycelial systems grazed by Folsomia candida (Collembola)

Abstract

Phanerochaete velutina is a major agent of wood decomposition in temperate forests. It grows out of woody resources in search of other resources and is then vulnerable to grazing by invertebrates. The aim of this study was to determine how continuous grazing and grazing for only 2 days by different densities of collembola, Folsomia candida, affect mycelial development (radial extension, hyphal coverage and fractal dimension) of P. velutina growing across non-sterile soil. High density (80 collembola) continuous grazing resulted in different mycelial foraging patterns compared to controls and lower density (20 and 40 collembola) continuous grazing: radial extension rate was reduced from 8.4 mm day(-1) (control) to 6.9 mm day(-1) (80 collembola), hyphal coverage was reduced to 81% of controls and mass fractal dimension increased from 1.68 (control) to 1.72 (80 collembola). There was evidence of over-compensatory growth: when high density grazing ceased the new growth was considerably greater (38%) than in controls. Grazing also resulted in growth stimulation: at low density continuous grazing (20 collembola) hyphal coverage was 15.6% greater than in controls. The ecological implications of compensatory and stimulatory growth in fungal-invertebrate interactions are considered.