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In two plots, domin~ted by Erica tetralix and Molinia caerulea, respectively, carpophores ofmacrofungi were counted during 7 successive years with fortnightly intervals. The changes in the number of species, number of carpophores, carpophore productivity and productivity of dominant species are described and discussed. In addition, the periodicity of some species is treated. It appears that quantitative and qualitative changes in the two stands do not parallel each other. The changes are mainly interpreted as fluctuations, whereas in the Molinia stand also successional trends are demonstrated. Also between the investigated species important differences exist. No simple relationships could be found with the prevailing weather conditions. fNTRODUCTTON This paper is based on mycocoenological research, carried out between 1974 and 1980. Mycocoenology comprises the quantitative and qualitative analysis of communities of larger fungi and the study of relations between these communities and environmental factors under field conditions. This discipline was introduced in The Netherlands by Barkman, who also made important contributions to the methodology (Barkman 1976(Barkman , 1987. This paper deals with the results in two plots, in moist heath lands dominated by Erica tetralix and Molinia caerulea, respectively. The absence of replicate plots does not enable stati stical treatment of the data.The aims of this study are to establish qualitative and quantitative changes in fruiting of macrofungi, and to relate the results to environmental conditions. Few investigations have been carried out in this field in proportion to studies on the dynamics of phanerogamic communities. Fluctuations in fruiting of macrofungi are often much stronger because of(i) the sensitivity of both primordia and mature carpophores to dessication and low temperatures (Ellenberg eta!. 1986); (ii) the limited life-span of carpophores, for most species in the order of a few days or weeks (Richardso.n 1970).Most mycocoenological studies last 2-4 years, which is too short to draw conclusions on the dynamics of the macrofungal flora (Winterhoff 1984). A few studies involve a longer series of observations. Holownia (1983) counted the carpophores of the saprophyte Collybia peronata in a Pinus-Quercus forest in Poland during I 0 successive years. She 29 1

The importance of private and commercial harvest of wild edible mushrooms in Europe and North America is briefly outlined. Possible negative effects of harvesting on the production of sporocarps are discussed. There is no evidence that picking of mushrooms is harmful for subsequent fruiting, except in some cases where mycelia are destroyed. Changes in frequency of edible mushrooms in Europe are described with special emphasis on The Netherlands. The occurrence of edible species on Red Lists of threatened fungi in Europe is discussed. The decline of many ectomycorrhizal species is supposed to be mainly caused by environmental pollution. Relations between harvesting of edible mushrooms, forest management and nature conservation are indicated. Key words: edible mushrooms, mushroom picking, decline of fungi, forest management.