CARBON TRANSLOCATION IN MYCELIAL CORD SYSTEMS OF PHANEROCHAETE-VELUTINA (DC, PERS) PARMASTO

Movement of radiotracer was monitored in mycelial cord systems developed from wood block inocula, precolonized by Phanerochaete velutina (DC.: Pers.) Parmasto grown on unsterile soil. In short-term studies, reproducible but low-level loading of radiotracer was observed which was independent of the extent of cord systems. Carbon translocation velocities ranged from 132 to 336 cm h-1, whilst fluxes were estimated to range from 35 to 66 nmol cm-2 h-1 (as glucose). When cord systems were supplied with a range of potential carbon resources as baits considerable movement of carbon was detected over 9 wk. More than 80% of exogenously supplied carbon was retained in resource units rather than being allocated to extra-resource mycelium. The direction and extent of carbon movement, and partitioning of decay between inocula and baits within cord systems, was dependent upon the type and size of bait and whether or not combinations of baits included wood pre-colonized by other saprotrophic fungi. There was evidence for coordinated use of resources within cord systems and that carbon movement was not a function of mycelial growth. Respiratory carbon losses were greatest when baits included sterile leaf litter packs and least when sterile wood baits were supplied. The results are discussed in terms of nutrient conservation and cycling in cord systems.