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

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.     

Effect of soil and litter type on outgrowth patterns of mycelial systems of Phanerochaete velutina

Abstract: The outgrowth patterns of Phanerochaete velutina from woody resources varied depending on the soil/litter type. There were clear differences in mycelial extension rate, time between contact with and emergence from baits, mycelial biomass, and extra-resource mycelial responses to contact with new resources depending on soil type, though there was little difference between fractal dimension, i.e. space filling, of mycelia with time or soil/litter type. In a few replicates, particularly in components from the Lawson's cypress stand, mycelia sometimes became brownish colour, ceased growth and eventually disintegrated. In litter the pattern of mycelial development was quite different from that in soil due to subsurface growth in which needles were often colonised. In humus, mycelial development was somewhat similar to that in soil.     

Translocation of 32P between wood resources recently colonised by mycelial cord systems of Phanerochaete velutina

Abstract The basidiomycete fungus Phanerochaete velutina was inoculated centrally into trays of compressed, non-sterile woodland soil on precolonised 1 cm³ beech wood blocks. Mycelial systems developed from this and colonised two ‘baits’ (wood blocks or inert plastic controls), one on either side of the inoculum block. ³²P-orthophosphate was supplied to a bait and its appearance in the other bait was monitored non-destructively with time, and destructively by liquid scintillation counting 60 or 70 days after addition of the radioisotope. Phosphorus was taken up by the first bait, translocated back to the inoculum block and onwards to the second bait. When the second bait was added 10 days after the first, translocation to the former was much more rapid indicating a large demand for phosphorus during early stages of colonisation. The size of the bait to which the ³²P was added appeared to determine the amount taken up by the whole system, and the size of the second bait determined how much ³²P was translocated to it. Decayed and/or small baits had less demand for phosphorous. The ecological relevance of these findings is discussed.     

A fractal model for the characterization of mycelial morphology

A new technique based on a fractal model has been developed for the quantification of the macroscopic morophology of mycelia. The morphological structuring is treated as a fractal object, and the fractal dimension, determined by an ultrasonic scattering procedure developed for the purpose, serves as a quantitative morphological index. Experimental observations reported earlier and simulations of mycelial growth, carried out using a probabilistic-geometric growth model developed for the purpose, both validate the applicability of the fractal model. In experiments with three different species, the fractal dimensions of pelletous structures were found to be in the range 1.45-2.0 and those of filamentous structures were in the range 1.9-2.7, with values around 2.0 representing mixed morphologies. Fractal dimensions calculated from simulated mycelia are in rough agreement with these ranges. The fractal dimension is also found to be relatively insensitive to the biomass concentration, as seen by dilution of the original broths. The relation between morphology and filtration properties of the broths has also been studied. The fractal dimension shows a strong correlation with the index of cake compressibility and with the Kozeny constant, two filtration parameters that are known to be morphology dependent. This technique could thus be used to develop correlations between the morphology, represented by the fractal dimension, and important morphology-dependent process variables. (c) 1993 John Wiley & Sons, Inc.