Productivity of matsutake [Tricholoma matsutake] in a natural forest of todo-fir [Abies sachallinensis] and environmental improvement for its occurrence

The fruit-body occurrence and the distribution of the shiro of Matsutake mushroom (Tricholoma matsutake) were studied in a natural forest of Todo-fir (Abies sachalinensis) in north-eastern part of Hokkaido, from 1987 to 2000. The productivity of Matsutake in the forest, and the effects of forest treatments for promotion of the fruit-body occurrence were discussed in this paper. A large number of shiros, 123 per hectare, was present in the investigation plot, but the fruit-bodies occurred per one shiro averaged only 1.5 a year. The poor mycelial growth (8.3-11.6 cm/year) of these shiros, even if healthy, may cause the poor productivity of Matstake in this plot. Many unvigorous or old-aged shiros present in this plot also suggested to cause the poor productivity of Matsutake. The crowded tree population, especially of the deciduous trees, the thick deposit of the raw humus, the distribution of the shiros of the harmful mycorrhizal fungi, and the uncontinuous depression in level at the base of the standing trees, were also considered to prevent the growth of the shiros and the fruit-body occurrence of Matsutake. For promotion of the fruit-body occurrence of Matsutake in this plot, it was desired to activate the unvigorous shiros, or to regenerate them to newly formed, productive ones. For this purpose, in 1993, the various treatments such as the thinning of the crowded trees, mainly of the deciduous trees, the removal of the litter and the raw humus, the replacement of the shiro soil of the antagonistic harmful fungi with the fresh, uninfected virgin soil, and the soil dressing at the base of the standing trees, were made in a multi-treated plot, and the thinning alone in a thinning plot. Both of these plots are called in this paper as the treated plots. Effects of these treatments were summarized as follows: (1) The fruit-body occurrence was promoted, especially in the multi-treated plot, in which plot the fruit-body production in one shiro increased and averaged 3.5 a year, and about 51 kg a year per hectare. (2) In the treated plots, Matsutake fruited in a larger number of shiros than in the untreated plot, mostly within 3 years after the treatments. (3) In the multi-treated plot, Matsutake had a thicker stem, which meaned a larger fruit-body, than in the untreated plot. (4) In the treated plots, the vigorous fruiting of Matsutake was recorded earlier or for a longer time than in the untreated plot. (5) Except for the very unvigorous and mortal shiros, the suppressed mycelial growth by the antagonistic mycorrhizal fungi or at the base of the standing trees, recovered within 4 years, after the replacement with the virgin soil. (6) In the multi-treated plot, one shiro observed in 2000 was probably newly formed. The treatments described in this paper were not only effective for the fruit-body occurrence in the unfructiferous shiros, but usefull to somewhat vigorous shiros for recovery of the mycelial growth in part and of the productivity of Matsutake. They were, however, not so effective for activation of the very unvigorous and mortal shiros. Further observations on the formation of the new shiros, will make it possible to regenerate the unvigorous or old-aged shiros, to the productive, new ones.