Pacific Southwest

Title: Standing crop and animal consumption of fungal sporocarps in Pacific Northwest forests

Author: North, Malcolm; Trappe, James; Franklin, Jerry

Date: 1997

Source: Ecology, Vol. 78(5): 1543-1554

Description: Although fungal fruiting bodies are a common food supplement for many forest animals and an important dietary staple for several small mammals, changes in their abundance and consumption with forest succession or disturbance have not been quantified. Above- and belowground fungal fruiting bodies (epigeous and hypogeous sporocarps) were sampled for 46 mo in managed-young, natural-mature, and old-growth western hemlock (Tsuga heterophylla) stands in Washington State. Screen exclosures were placed over the surface of half of the sample plots to prevent aboveground predation of sporocarps. Standing crop of epigeous sporocarps was low in most seasons and then increased 30-fold to a mean of 2.28 kg/ha in the fall. Epigeous biomass varied little between stand types, and animal consumption of these sporocarps was low. Standing crop of hypogeous sporocarps was 0.78 kg/ha in managed-young stands, compared to 4.51 and 4.02 kg/ha in natural-mature and old-growth stands. In all stands, standing crop peaked in the summer and was lowest in the winter. Mean animal consumption of hypogeous sporocarps was 0.64 kg/ha, a value that exceeded the available standing crop quantity of 0.36 kg/ha in managed-young stands during the winter. In natural-mature and old-growth stands, truffle biomass remained high year-round and exceeded consumption in all seasons. Low hypogeous sporocarp biomass in the managed-young stands resulted from the general absence of large clusters of Elaphomyces granulatus, which made up .90% of the biomass in older stands. This absence in managed-young stands may be associated with the thin organic layer that has developed following harvest and burning 60 yr ago. The consistent level of animal consumption indicates that truffles may be an important and readily available year-round food source, compared to the ephemeral fruiting of epigeous sporocarps. Changes in forest composition and age due to natural disturbance or human management influence fungal sporocarp productivity and diversity and, consequently, affect food availability for animals dependent on hypogeous sporocarps.

Keywords: Elaphomyces granulatus, epigeous fungi, exclosures, hypogeous sporocarps, mycophagy, northern flying squirrel, old growth, small mammals, truffles

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Citation

North, Malcolm; Trappe, James; Franklin, Jerry  1997.  Standing crop and animal consumption of fungal sporocarps in Pacific Northwest forests.   Ecology, Vol. 78(5): 1543-1554.