Northern flying squirrel mycophagy and truffle production in fir forests in northeastern California.

In this paper we summarize the results of four studies in which we either examined the feeding habits of the northern flying squirrel (Glaucomys sabrinus), a mycophagous (consuming fungi) small mammal, or compared the abundance of truffles (sporocarps of hypogeous mycorrhizal fungi) among different types of fir (Abies) forest. The studies were conducted within the Lassen National Forest in northeastern California between 1990 and 1994. In the first study, we found that abundance of northern flying squirrels was significantly less in old-growth fir stands that had been shelterwood-logged 6 to 7 years previously than in nearby, unlogged old-growth and mature fir stands. Truffles were common in the diet of flying squirrels, truffle frequency was low in the shelterwood-logged stands compared to the unlogged old-growth and mature stands, and abundance of flying squirrels was correlated with truffle frequency across the 12 stands in which we estimated both. In the second study, we found no significant effects on total truffle frequency and biomass of truffles from commercial thinning or broadcast burning that had occurred about 10 years previously, but there were significant effects of thinning on frequencies of individual truffle genera. In the third study, we compared food preferences of captive northern flying squirrels among sporocarps of five species of fungi, two species of lichens, and fir seeds. Foods most preferred were two species of truffles, and consumption rate differed significantly among the five species of fungi. In the fourth study, we found that total truffle frequency and biomass and species richness did not differ significantly between old-growth and nearby, mature fir stands. We also observed that abundance of truffles (pooled across species) was not significantly associated with decayed wood, depth of the organic soil, or other habitat features. We collected 46 species of truffles in these floristically simple forests, however, and there was significant association between age class and frequencies of individual truffle species. Our data suggest that the effects of disturbance on truffle assemblages are species specific, and that predicting the effects of forest management on mycophagous small mammals may be difficult until more is known about the effects of disturbance on truffle production and the nutritional values of different truffle species. ' An abbreviated version of this paper was presented at the California Forest Soils Council Conference on Forest Soils Biology and Forest Management, February 23-24, 1996, Sacramento, California. 2 Wildlife Biologist, Research Forester, and Research Wildlife Biologist, respectively, Pacific Southwest Research Station, USDA Forest Service, 1700 Bayview Drive, Arcata, CA 95521. Current address of Kevin McKelvey: Rocky Mountain Research Station. Forest Service, U.S. Department of Agriculture, 800 E. Beckwith, Missoula, MT 59801. 3 Assistant Professor, Department of Forest Science, Oregon State University, Corvallis, OR 97331. USDA Forest Service Gen. Tech. Rep. PSW-GTR-178. 2000. 73 Northern Flying Squirrel Mycophagy and Truffle Production—Waters, McKelvey, Zabei, Luoma