Regeneration of natural forests was studied in the Nakagawa Experiment Forest of Hokkaido University using age distribution surveys made by the clear felling method.In Plot 1 (30 m • 65 m), Abies sachalinensis dominated the canopy layer but there were also a few Betula ermanii trees. Sasa senanensis densely covered the forest floor. Most of the canopy trees were from 122 to 195 years old. Seedlings younger than 50 years old of A. sachalinensis were found on fallen logs and root bases. There were, however, few trees from 50 to 120 years old. The present canopy trees seemed to have regenerated after competitive pressure from old canopy and Sasa disappeared 180 years ago. Plot 2 (50 m • 100 m) on serpentinite soil was dominated by Picea glehnii. Sasa kulirensis covered the floor but not as densely as S. senanensis in Plot 1. The ages of P. glehnii ranged from 1 to 586 years old, and the age distribution ofA. sachalinensis was L-shaped.A small gap in the canopy formed about 290 years ago, and it gradually extended. Conifers regenerated continuously in the extending gap but B. ermanii did not. One hundred thirty years ago, part of Plot 2 was again destroyed and A. saehalinensis and B. ermanii regenerated. Thus, two types of regeneration were found. One regenerated both conifers and Betula after a sudden disturbance of canopy layer or death of Sasa, and the other, under an extending gap, regenerated only conifers.

Gastrodia elata was collected from July to August 1992 in Hokkaido forests. A total of 22 diploid isolates were paired with haploid testers of the biological Armillaria species reported in Hokkaido. One isolate was identified as A. ostoyae, 10 as /I. gallica, three as A. jezoensis, three as A. sinapina, and five as A. singula. These isolates were compatible with the respective Hokkaido testers of these species. With the exception of A. ostoyae, these species are known as saprophytes, which form abundant rhizomorphs in soil.Clear isozyme profiles of esterases were obtained with all isolates except one. Interspecific variations were more important than intraspeeifie variations. The esterase profiles could be used for identification of the Armillaria species in Hokk.^ido as a useful complement to the mating-type method.U. S.

The frequency of occurrence of the litter-decomposing basidiomycetes of Picea abies and P. glehnii forest floors in Hokkaido was investigated. In both the P. abies and P. glehnii forest plots (each 10 m x 10 m), litter-decomposing basidiomycetes of the genera Collybia and Mycena were frequently observed. Species composition, frequency of occurrence, and basidioma numbers of each species were different between the two forest plots, but several species were common to both. Seven species isolated from the P. glehnii forest plot (C. acervata, C. pinastris, Marasmius pallidocephalus, Ma. wettsteinii, My. aurantiidisca, My. clavicularis, Mycena sp. 1) and four species from the P. abies forest plot (C. pinastris, My. alphitophora (= My. osmundicola), Mycena sp. 1, My. vulgaris) were tested for their ability to degrade lignin by a simple plate test for extracellular phenoloxidases and by measuring Klason lignin loss from needle litter of spruce. All the strains of the litter-decomposing fungi tested showed positive reactions on the plate test.Lignin contained in the needle litter was degraded by all strains tested (only My. alphitophora was not tested), and rates varied from 9% to 40% over a two-month period in vitro. Seven species with ligninolytic ability in the P. glehniiforest plot and four such species in the P. abies forest plot were found respectively in 77% and 60% of the 100 subplots in each plot. The results of this study suggest that lignin decomposition of needle litter by Utter-decomposing basidiomycetes in the forest floor is a common event in the studied Picea forests of Hokkaido and that the diversity of the ligninolytic activity among the species or strains may cause spatial heterogeneity of litter decomposition in the Picea forest floor.

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To determine the phylogenetie positions of two new speeies, Armillaria jezoensis and Armillaria singula, and one new subspecies, Armillaria mellea suhsp. nipponica, the nueleotide sequetices ot the intergenic spacers (IGS) ot their ribosomal DNA were investigated, and compared with those of tour other Armillaria species trom Japan, and those of nine Armillaria speeies from Europe and North Ameriea. We conclude that Armillaria jezoensis, and Armillaria singula belong to the Armillaria galliea cluster :is Armillaria cepistipes, Armillaria gaUica An<\ Armitlaria sinapina i\-om]i\p.\n.'Xwo\so\s.x.c^ oi Armillaria ostoyae front Japan were placed witliin the Armillaria ostoyae duster. Armillaria mellea stibsp. nipponiea had an IGS sequence as long as the IGS ot Armillaria mellea trom Europe and North Ameriea. However, the IGS sequences oi Armillaria mellea subsp. nipponiea, whose basidium base laeks a elamp conneetion eould not be satisfaetorily aligned with the IGS sequenees of other speeies possessing this morphological teature.