Effects of mushroom harvest technique on subsequent American matsutake production

Abstract

The commercial harvest of American matsutake ( Tricholoma magnivelare) is a multi-million dollar industry in the Pacific Northwest region of North America. How to best manage for sustainable mushroom production is uncertain and concerns remain about the cumulative effects of picking in the same areas year-after-year and whether raking of surface litter and mineral soil layers to find mushrooms will reduce subsequent fruiting. Here, we evaluate the effects of several mushroom harvest techniques on American matsutake production. This study was established in the Oregon Cascades in 1994 with the selection of 18 shiros of similar mushroom production. Six mushroom harvest treatments were implemented in 1995: (1) control, (2) best management practice (BMP), (3) shallow rake, litter replaced, (4) shallow rake, no replacement, (5) deep rake, litter replaced, (6) deep rake, no replacement. These treatments were pooled into three litter disturbance groups for analysis: (a) no raking of the litter, (b) litter raked with replacement, and (c) litter raked without replacement. Matsutake production on additional shiros was monitored to further compare the control and BMP treatments. Our results demonstrate that careful picking (BMP) was not detrimental to mushroom production during the initial 10 years of mushroom harvest activity. One-time treatments in which the forest floor litter layers were removed and not replaced were strongly detrimental to matsutake production and the effects have persisted for 9 years. Matsutake production was reduced to an intermediate degree by the raking with litter replacement treatments. Damage to shiros caused by repeated raking was not tested, however we expect that the effects of repeated raking would be more severe than those reported here. Negative treatment effects were particularly noticeable in years with abundant fruiting. When environmental conditions are poor for fruiting all shiros experience low production, thereby obscuring treatment effects. Within-year and year-to-year variation in fruiting is a major challenge to studies of matsutake ecology, particularly with regard to documenting treatment effects. Further studies spanning years or even decades will likely be needed to quantify production, effects of management activities, and investigate the biology of Tricholoma magnivelare. Because this study was limited to one habitat type, extension of the results to substantially different habitats types must be made with caution. However, we speculate that since the underlying biology of matsutake fruiting is similar across a wide range of habitats, careful picking should generally not hinder subsequent fruiting when other substantial disturbance to the shiro is absent.