Mycelial cord systems of Phanerochaete velutina
(DC.: Pers.) Parmasto grown from 4 cm3 inocula on a nutrient-depleted
non-sterile soil in compartmentalized laboratory microcosms were baited
after 13 d
of growth with either fresh, non-sterile 4 cm3
wood blocks or control Perspex® blocks of the same contact area. After
112 d, mature
mycelial systems, which were in senescent phase, were subjected to
disturbance by supplying a new fresh wood
bait diametrically opposite the existing bait and, after 126 d, to nutrient
regime amendment by application of NPK
solution. At harvest (186 d) there was a significant (P[les ]0·001)
linear relationship between extra-resource mycelial
biomass and total wood decay over the preceding 74 d. Nutrient amendment
alone did not significantly (P>0·05)
affect extra-resource mycelial biomass production or wood decay rates in
either disturbed or undisturbed cord
systems. However, both mycelial biomass production and resource decay
were significantly (P[les ]0·05) enhanced
when nutrient amendment and disturbance treatments were applied
concurrently. Bi-directional phosphorus
translocation to inocula and wood baits (determined non-destructively)
was
assessed by labelling the NPK solution
applied distal or proximal to the initially supplied bait with
32P. In both disturbed and undisturbed cord systems
the rate of 32P uptake from a local supply was two orders of
magnitude higher than from a distal supply. In
disturbed cord systems uptake of 32P by inocula, which
were midway between the two radiotracer supply points,
was significantly (P[les ]0·05) higher when the supply point
contained a newly supplied wood bait. Net translocation
of 32P to newly supplied wood baits increased with time at the
expense of translocation to inocula and existing wood
baits. The switch in direction of net phosphorus translocation, the
importance of localized nutrient scavenging and
the partitioning of wood decay are discussed in relation to the ecological
significance of mycelial cords.