1999. 103: 1353-1359.
Early effects of prescribed fire on the structure of the
ectomycorrhizal fungal community in a Sierra Nevada ponderosa pine
Stendell, E.R.1, T.R.
Horton2 and T.D. Bruns
Medical College of Wisconsin, 8701 Watertown Plank Road,
Milwaukee, Wisconsin 53226, USA
Department of Forest Science, Oregon State University,
Corvallis, OR 97331, USA
Department of Plant and Microbial Biology, 111 Koshland Hall,
University of California, Berkeley, California, 94720, USA
The effects of a prescribed fire on the presence of
ectomycorrhizal fungi on the root tips of ponderosa pine were
investigated one year after a prescribed ground fire.
Ectomycorrhizae were sampled within one square meter plots before
and one year after the fire, and in nearby control plots that were
not burned. The cores were divided into litter/organic, upper
mineral, and lower mineral layers. The total ectomycorrhizal
biomass in the control plots did not differ between year one and
year two samples for any core layer, while in the fire plots the
destruction of the litter/organic layer resulted in an eight-fold
reduction in total ectomycorrhizal biomass. Mycorrhizal biomass
in the two mineral layers was not significantly reduced by the
fire. We used molecular tools to identify fungi directly from the
ectomycorrhizas. In unburned plots members of the Russulaceae and
Thelephoraceae were among the most frequent and abundant
ectomycorrhizal types; species of most other taxa were rare. In
the control plots these two families were among the dominant
species in both years, but patchiness on a fine spatio-temporal
scale caused some major changes in ranking of individual species
between sample years. Rhizopogon subcaerulescens was the most
pronounced example; its biomass in the control plot samples was
seven times greater in year two than in year one because of an
exceptionally large cluster of mycorrhizas encountered in a single
core. The effect of fire on individual species was difficult to
assess because of this patchiness and because all species were low
in abundance after the fire. The most abundant pre-fire species
were reduced to undetectable post-fire levels, while several less
abundant species, including Rhizopogon subcaerulescens, Cenococcum
geophilum, and several unknown types were not substantially
reduced by the fire. We speculate that the more abundant species,
Martellia sp., thelephoroid 1, and Tomentella sublilacina, were
differentially affected because their dominance was most prominent
at the litter and organic layers. In any case, a short-term
effect of this fire appears to be increased species evenness.
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