Individual study: Effects of picking on the sustainability of edible mushroom harvests at Chanéaz fugus reserve, Genève, Switzerland
Egli S., Peter M., Buser C., Stahel W. & Ayer F. (2006) Mushroom picking does not impair future harvests – results of a long-term study in Switzerland. Biological Conservation, 129, 271-276
Forest fungi have important ecosystem functions, such as decomposing organic matter and and pathogen resistance of their host trees. Picking their fruiting bodies for food is a popular past time in many countries, and is sometimes commercially important. The expansion of commercial harvesting has led to widespread concern about over-harvesting and possible damage to fungi populations. Several countries have introduced legal restrictions on harvesting. In Switzerland there are weight limits on harvests, a measure, which has proved controversial due the lack of scientific evidence regarding the effectiveness of such restrictions. In this case, the long-term effects of picking or cutting mushrooms on future mushroom harvests are described.
Experimental design: The study was carried out in Chanéaz, a 74 ha fungus reserve in southwestern Switzerland. The area comprises mixed old-growth forest dominated by beech Fagus sylvatica, pedunculate oak Quercus robur, Norway spruce Picea abies, silver fir Abies alba, Scots pine Pinus sylvestris, Eastern white pine Pinus strobus and European larch Larix decidua.
Experimental design: The study was conducted over a 27-year period (1977-2003). Five 300 m2 blocks were divided into three 10 m × 10 m plots containing three treatments:
1) harvesting by picking
2) harvesting by cutting
3) a control
In treatment plots, all edible mushrooms were plucked or cut weekly throughout every fruiting season (May – December) in a manner mimicking that of a mushroom harvester. Plucking mushrooms entailed removing the cap and stipe (stem) from the soil with some damage to the mycelium. Cutting mushrooms entailed slicing the stipe with a knife close to the ground, thus avoiding damage to the mycelium. All observation plots were surrounded by fences to avoid disturbance by mushroom pickers.
Sampling: All fruiting bodies (i.e. cap and stipe) of soil-inhabiting macromycete fungi were identified and counted at weekly intervals from May to December. When first recorded, the fruiting bodies were marked with a harmelss dye (methylene blue) on the cap to avoid double counting. Thirty-nine species that form large quantities of very small fruiting bodies (but which are still harvested) were excluded to avoid counting difficulties, as were 12 taxonomically indistinct species to avoid possible irregularities due to uncertain identification.
A total of 436 species were counted, comprising 97,700 fruiting bodies. Of these, 53,863 fruit bodies of 103 species belonged to edible fungi.
Selective harvesting of ground-dwelling, edible macromycete fungi did not decrease relative to unharvested non-edible ones with respect to either the abundance of fruiting bodies or species richness. Over the 27-year duration of the study, no different trends in fruting body production were detected between the harvested and non-harvested sites, irrespective of the harvesting technique deployed. Furthermore, average species richnes and average abundance of fruiting bodies over the entire 27-year period did not differ significantly between treatments (see Table 1, attached).
Conclusions: In this study, no difference in species richness or abundance of species of edible fungi (that are collected by mushroompickers) was evident in the harvested compared with the non-harvested sites. Since harvesting fungal fruiting bodies effectively removes the spores, either adequate numbers of spores were recruited from neighbouring areas or fungi reproduced asexually through the spread of mycelium. The results raise questions about the usefulness of harvest quotas. However, as widescale harvesting fungi may deplete the availability of spores over large areas, further information about spore dispersal is needed before the impacts of such harvesting on fungi populations can be determined.
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