Document: GRA-3-58-37

Diversity and consistency of fungal fruiting over three years along clearcut center to forest interior transects in western Washington.

SPARKS, G.B.*, J.A.AMMIRATI and R.L.EDMONDS

University of Washington, Seattle, WA 98195 USA ¹

Abstract:
Timber harvesting in the Pacific Northwest has led to dramatic changes in age and structural complexity of forest stands, and has altered forest patterns at the landscape level as well. We are investigating fungal sporocarp production in mature second-growth conifer stands and adjacent recent clearcuts, particularly as affected by distance from edge. We positioned 1 by 4 m² sampling plots at set distances along thirteen different transects running from forest interiors to clearcut centers, and collected mushrooms from those plots during autumn in 1995-1997. Sporocarps were identified and classified by functional group and size: Ectomycorrhizal (receive carbon from tree hosts via roots), large fleshy decomposers (often found on coarse woody debris such as stumps), or small decomposers (commonly colonizing fallen needles). Each taxon on each plot also received a score for consistency, ranging from 1 to 3, depending upon how many years it was found fruiting. Total diversity per plot was occasionally greater than 30 taxa, unexpectedly high for second-growth forests. Average mycorrhizal diversity was consistently high throughout forests, but declined gradually between 1 to 10 meters into clearcuts. Deep in forest interiors (>200 m from edge), relatively few new mycorrhizal taxa were found on plots during the second or third years of sampling. At forest edges, however, nearly equal numbers of new taxa appeared each year. Diversity of large decomposers was low inside forests, but rose abruptly at forest edges and into clearcuts. Small decomposers were equally diverse everywhere along the transects, except for a marked decline in the very centers of clearcuts. Consistency of fruiting showed a similar pattern: In areas where their functional group exhibited high diversity, individual taxa also fruited more reliably from year to year. However, small decomposers were more consistent than either large decomposers or mycorrhizal taxa at any location. It appears that both diversity and consistency of fungal fruiting depends to a large extent upon resource availability, and also upon microclimatic conditions, both of which can vary considerably, sometimes over only a few meters, along forest-to-clearcut transects.

Keywords: ectomycorrhizal fungi, decomposer fungi, forest edges, sporocarp diversity

This abstract is being presented at: 3:30 PM in session:
MICROBIAL ECOLOGY