Response of Ectomycorrhizal Fungus Sporocarp Production to Varying Levels and Patterns of Green-tree Retention Daniel L. Luoma1, Joyce L. Eberhart1, Randy Molina2, and Michael P. Amaranthus1 1Department of Forest Science Oregon State University Corvallis, Oregon 97331-7501 Daniel.Luoma@oregonstate.edu 2Pacific Northwest Research Station USDA Forest Service Corvallis, Oregon 97331-7501

We provide a brief overview of this work below. For full text see:

Luoma, D. L., J. L. Eberhart, R. Molina, and M. P. Amaranthus. 2004. Response of ectomycorrhizal fungus sporocarp production to varying levels and patterns of green-tree retention. Forest Ecology and Management 202:337-354.

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. Pre-treatment data were collected for 2-3 yr between 1993 and 1997 and post-treatment data for 3 yr 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 et al. 1999). Fresh specimens were identified to the lowest taxonomic level possible using a stereo microscope, then dried for 8-18 hr 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% aggregated and dispersed treatments and least in the 75% aggregated treatment. However, these effects varied 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 due to reduced edge effects.