Demonstration of Ecosystem Management Options Study

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Response of Ectomycorrhizal Fungus Sporocarp Production to Varying Levels and Patterns of Green-Tree Retention

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Ectomycorrhizal fungi (EMF) play an important role in maintaining forest productivity and recovery from disturbance; thus, the effects of variable-retention harvests on abundance and diversity of EMF is a key consideration for forest managers. Fungal sporocarps were sampled in three of the six DEMO blocks during peak spring and fall fruiting seasons. Pretreatment data were collected for 2 to 3 years between 1993 and 1997 and posttreatment data for 3 year between 1998 and 2001. A combination of fixed and temporary strip plots (2 x 50 m; see figure below) were established in each treatment unit within which both epigeous (mushroom) and hypogeous (truffles) sporocarps were sampled (Cazares, E.; Luoma, D.L.; Amaranthus, M.P. [et al.]. 1999. Interaction of fungal sporocarp production with small mammal abundance and diet in Douglas-fir stands of the southern Cascade Range. Northwest Science. 73(Special Issue): 64-76.). Fresh specimens were identified to the lowest taxonomic level possible by using a stereo microscope, then dried for 8 to 18 hours at 63 °C in a portable dehydrator until crisp-dry. Analyses were conducted separately for mushrooms and truffles based on total sporocarp standing-crop biomass (g/ha dry wt). Consideration of treatment effects at lower taxonomic levels is in progress.

A total of 150 mushroom and 58 truffle taxa were collected during the course of the study. Effects of treatments on the taxonomic diversity of EMF were generally proportional to the level of retention: compared to controls, the number of sporocarp-producing taxa was reduced most in the 15-percent aggregated and dispersed treatments and least in the 75-percent aggregated treatment. However, these effects differed by type of sporocarp and by season. Mushroom biomass was reduced in four of five harvested treatments in fall, but in only one of five treatments in spring. Truffle biomass was significantly reduced in three of five treatments in fall and all harvested treatments in spring. These results suggest that, in a given harvest unit, a combination of aggregated and dispersed retention may be most effective at maintaining the EMF community. Higher levels of retention maintained higher levels of sporocarp production. It is likely that dispersed retention ameliorates the detrimental effect of clearcutting on fungal diversity, and that forest aggregates embedded in dispersed retention will maintain sporocarp production owing to reduced edge effects.

US Forest Service - Pacific Northwest Research Station, Demonstration of Ecosystem Management Options
Last Modified: Thursday,27March2008 at12:39:04EDT