Book of Abstracts (PDF) - International Mycological Association

IMC7 Thursday August 15th Lectures
further study would be needed to extrapolate this
information into general trends, boreal hot springs appear
to offer unique opportunity to study the potential impacts
of climate change on boreal fungi and plants.
315 - Biomass of ectomycorrhizal mycelia at different
soil depths and along nutrient gradients in the boreal
forest
H. Wallander * , L.-O. Nilsson, S. Mahmood & S. Erland
Department of Microbial Ecology, Lund University,
Ecology Building, 223 62 Lund, Sweden. - E-mail:
Hakan.Wallander@mbioekol.lu.se
Nutrient uptake by forest trees is greatly dependent on
ectomycorrhizal (EcM) fungi. We quantified the
production of EcM mycelia in the field by the use of ingrowth
mesh bags. Mesh bags were placed at different soil
depths (5-15-30 cm) in spruce and mixed spruce/deciduous
forests in southern Sweden and in the humus layer along a
natural nutrient gradient in northern Sweden. Spruce stands
produced 590 kg EcM biomass ha -1 while mixed forests
produced 420 kg ha -1 . The delta-13C value of mycelia
collected from mesh bags was similar to values of EcM
fruitbodies, and it was not influenced by soil depth,
indicating that the mycelia were of EcM origin. The delta-
13C value in mycelia from mixed forests suggested that the
mycelia received more carbon from spruce trees than from
oak trees. The production of EcM mycelia decreased with
soil depth. The decrease was more accentuated in mixed
stands compared to pure spruce stands. In the natural
nutrient gradient (low N and low pH changed gradually to
high N and high pH) the production of EcM biomass
decreased when moving from the nutrient poor to the
nutrient rich end. We identified some of the EcM species
that colonized the mesh bags with PCR/RFLP analysis of
ribosomal DNA. We found a low level of similarity
between EcM species found on root tips outside the mesh
bags and EcM species found as mycelia or rhizomorphs
inside the mesh bags. Fast growing species such as Paxillus
involutus were common in mesh bags but rare on root tips.
316 - New perspectives on the ecological distribution of
epiphytic hair lichens (Bryoria) in northern forests
T. Goward
Enlichened Consulting Ltd., Edgewood Blue, Box 131,
Clearwater, B.C. V0E 1N0, Canada. - E-mail:
tgoward@interchange.ubc.ca
Caribou biologists working in the high-elevation conifer
forests of inland British Columbia have long observed that
hair lichens in the genus Bryoria attain much heavier
loadings in oldgrowth stands than in adjacent younger
stands. In an attempt to account for this phenomenon, I
examined Bryoria species composition in regenerating
forests along successional and within-stand vertical
100
Book of Abstracts
gradients. Bryoria appears to enter regenerating stands in
two phases. In the first phase, to about 70-100 years, B.
fuscescens and B. glabra dominate throughout the canopy.
These are small, sorediate lichens with a relatively high
tolerance for prolonged wetting. After ca. 100 years, these
species are increasingly replaced, at least in the upper
canopy, by the non-sorediate B. fremontii and B.
pseudofuscescens. These are large, relatively xerophytic
hair lichens favoured by open, well-ventilated conditions.
B. fremontii and B. pseudofuscescens have indeterminate
growth; once established in the upper canopy, they tend to
fragment, thereby being continuously 'parachuted' into the
lower canopy. It is the gradual accumulation of these nonsorediate
species at all levels of the canopy that ultimately
leads to an elevated Bryoria biomass in oldgrowth forests.
The ability of B. fremontii and B. pseudofuscescens to
persist in the lower canopy does vary considerably from
year to year, depending on the occurrence of 'die-back'
events associated with prolonged dampness.
317 - Implications of fungal translocation for nutrient
cycling in boreal forest ecosystems
B.D. Lindahl
Dept. of Forest Mycology and Pathology, SLU, Box 7026,
SE-750 07 Uppsala, Sweden. - E-mail:
bjorn.lindahl@mykopat.slu.se
Most current models of nutrient cycling have been
developed with a vague concept of 'microorganisms' in
mind, generally relating to bacteria. In boreal forest
ecosystems, fungi probably play a more important role than
bacteria in the decomposition of organic matter. Most fungi
differ from bacteria in that they are multicellular and able
to translocate resources throughout their mycelia. Current
nitrogen cycling models are centred around mineralisation;
as substrates with a low C/N-ratio are degraded, nitrogencontaining
organic compounds are thought to be used as an
energy source, leaving ammonium as an undesired
biproduct that is released. Fungi may, however, degrade
substrates with a low energy content, using carbohydrates
that are translocated from external sources such as woody
debris, litter or living roots in the case of mycorrhizal
fungi. Obtained nutrients may be translocated back in the
opposite direction to support colonisation and degradation
of the nitrogen-poor wood or litter, or to support a
mycorrhizal host plant. Translocation of resources thus
enables fungi to utilise resources of various qualities more
efficiently, conserving nutrients within their mycelia
instead of exuding them. In light of the capacity of boreal
forest plants to access organic forms of nitrogen via their
mycorrhizal associates, it is likely that a significant fraction
of the nitrogen recycling from organic matter back to plants
takes place without the nitrogen ever being mineralised.