Boberg J, Finlay RD, Stenlid J, Näsholm T, Lindahl BD
Glucose and ammonium additions affect needle decomposition and carbon allocation by the litter degrading fungus Mycena epipterygia.
Soil Biology and Biochemistry: 2008 40:995-999
Saprotrophic microorganisms in soils have traditionally been assumed to
be carbon (C) limited, since additions of readily assimilable
carbohydrates usually result in increased respiration. In many forest
soils, however, rapid nitrogen (N) immobilization and increased
microbial growth in response to N addition indicate N limitation. Here
we test whether this apparent contradiction could be explained by
changes in C allocation between microbial growth and respiration (i.e.
changed C-use efficiency) under controlled conditions in laboratory
microcosms. Respiration, mycelial production and needle mass loss were
monitored after application of glucose or ammonium sulphate to Pinus sylvestris needles inoculated with the litter decomposer fungus Mycena epipterygia.
Addition of ammonium resulted in a 32% increase in respiration, 31%
increase in needle mass loss and increased mycelial production,
indicating that both growth and activity of the fungus were N limited.
In spite of N limitation, additions of glucose resulted in a 19%
increase in respiration but had no effect on mycelial production and
led to a 17% decrease in needle mass loss, indicating a reduced C-use
efficiency of the fungus. The capacity of individual fungi to adapt
their C-use efficiency to C availability implies that additions of
labile C could increase respiration even under N-limited conditions.
e-link to journal