Tsuneo Igarashi

Regeneration process of coniferous forests in northern Hokkaido I.Abies sachalinensis forest andPicea glehnii forest

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 fewBetula 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 ofA. 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 andSasa disappeared 180 years ago. Plot 2 (50 m × 100 m) on serpentinite soil was dominated byPicea glehnii. Sasa kulirensis covered the floor but not as densely asS. senanensis in Plot 1. The ages ofP. 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 butB. ermanii did not. One hundred thirty years ago, part of Plot 2 was again destroyed andA. sachalinensis andB. ermanii regenerated. Thus, two types of regeneration were found. One regenerated both conifers andBetula after a sudden disturbance of canopy layer or death ofSasa, and the other, under an extending gap, regenerated only conifers.

Lignin-degrading ability of litter-decomposing basidiomycetes from Picea forests of Hokkaido

The frequency of occurrence of the litter-decomposing basidiomycetes ofPicea abies andP. glehnii forest floors in Hokkaido was investigated. In both theP. abies andP. glehnii forest plots (each 10 m×10 m), litter-decomposing basidiomycetes of the generaCollybia andMycena 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 theP. glehnii forest plot (C. acervata, C. pinastris, Marasmius pallidocephalus, Ma. wettsteinii, My. aurantiidisca, My. clavicularis, Mycena sp. 1) and four species from theP. 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 (onlyMy. alphitophora was not tested), and rates varied from 9% to 40% over a two-month period in vitro. Seven species with ligninolytic ability in theP. glehnii forest plot and four such species in theP. 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 litter-decomposing basidiomycetes in the forest floor is a common event in the studiedPicea forests of Hokkaido and that the diversity of the ligninolytic activity among the species or strains may cause spatial heterogeneity of litter decomposition in thePicea forest floor.

Biological species and morphological characteristics of Armillaria mellea complex in Hokkaido: A. sinapina and two new species, A. jezoensis and A. singula.

Three intersterility groups ofArmillaria mellea sensu lato were discovered by examining all pairwise combinations of monosporous isolates of basidiomes collected in Hokkaido. One of them, group IV, was identified asA. sinapina by mating it with tester strains. Two new species, groups III and V, were namedA. jezoensis andA. singula, respectively. Their morphological forms and the ecology of their basidiomes are described.

A note on Armillaria mellea subsp. nipponica subsp. nov. in Japan

Basidiomes of homothallicArmillaria mellea complex were discovered in the forests of Hokkaido. Their monosporous isolates showed partial compatibility with North AmericanA. mellea s. str. haploid testers. The morphological characteristics of basidiomes differed from other temperateA. mellea s. str. in several aspects. Here, JapaneseA. mellea s. str. is reclassified asA. mellea subsp.nipponica and its basidiome morphologies and habitats are described.

Armillaria jezoensis, a new symbiont of Galeola septentrionalis (Orchidaceae)in Hokkaido

NineArmillaria isolates obtained from the roots ofGaleola septentrionalis in Hokkaido were identified asA. jezoensis by means of mating tests. Cultures of these isolates were similar in colony morphology, mycelial growth and rhizomorph formation on each of malt extract-dextrose agar (MDA), potato-dextrose agar (PDA), andG. septentrionalis root extractdextrose agar (GDA) media, showing better mycelial growth and rhizomorph formation on GDA medium.

Negative trend between seed size and adult leaf size throughout the geographical range of Fagus crenata

Abstract:Geographic variation in seed size of Japanese beech (Fagus crenata Blume) was examined. Seed size was not significantly correlated with climatic factors, such as mean annual temperature, warmth index, annual rainfall, latitude, number of days with snow depth ≥ 50 cm per year, but showed a significant negative correlation with adult leaf size. It is suggested that the variation resulted from trade-off relationship between reproductive and vegetative organs or genetic constraints.

Mycorrhizae of Monotropastrum giobosum growing in a Fagus crenata forest

The achlorophyllousMonotropastrum globosum was found growing in aFagus crenata forest. Samples ofM. globosum and their interpenetrating root systems ofF. crenata were collected to investigate the mycorrhizal association.Monotropastrum globosum mycorrhizae showed thick sheaths, invasion of the epidermal cells by fungal pegs, and Hartig nets, which reached only the first layer of cortical cells. TheF. crenata mycorrhizae also showed thick sheaths, but Hartig nets penetrated deep into the cortex and intracellular hypha were seen in the outer cortical cells. The similarities observerd in the mantle inner plan view and emanating hypha suggest that both mycorrhizae are formed by the same fungus.

Spatial distribution of Collybia pinastris sporophores in a Picea abies forest floor over a 5-year period

Collybia pinastris is a relatively common litter-decomposing basidiomycete in spruce forests in Hokkaido, Japan. The spatial distribution of sporophores of C. pinastris was investigated for 5 years within a plot of 3 m × 10 m in size (subdivided into 0.5 m × 0.5 m subplots) in a pure stand of Picea abies. There were significant differences in the total numbers of sporophores during the sampling years. The total number of subplots in which sporophores occurred were also significantly different during the sampling years. However, the spatial distribution of the subplots with sporophores showed agreement with the distributions in subsequent years. There was no significant correlation between the number of sporophores and the thickness of the litter layer in the subplots, whereas the litter layers in the subplots with sporophores were significantly thinner than those without sporophores. These results suggested that perennial or renewable mycelia of C. pinastris occupied the same or close locations year to year for at least 5 years and that the spatial distribution in this plot was restricted not by a shortage of substrates but by other factors.

Occurrence and types of ectomycorrhizae present in seedlings of Picea glehnii in a natural forest in Hokkaido

Picea glehnii seedlings whose ages ranged from 2 to 5 years and which were growing in aP. glehnii-Abies sachalinensis natural forest where the surface had been scarified 6 years before, were assessed for the occurrence and types of ectomycorrhizae. Based on the macro- and microscopic characteristics, 34 types of ectomycorrhizae were classified. The basidiomycetes were clearly dominant and it was common to observe more than one type of mycorrhiza occurring in the same root tip. The diversity of mycorrhizal types and the presence of at least one type of ectomycorrhiza in a single seedling, observed in this work, indicate a very dynamic system of mycorrhizal formation inP. glehnii seedlings, which allows them to survive and grow in a forest surface subjected to soil scarification.

Collybia biformis and C. pinastris new to Japan

Two species ofCollybia are recorded for the first time from Japan:C. biformis from Hokkaido, andC. pinastris from Hokkaido and Honshu (Nagano Prefecture). Macro- and microscopical descriptions and illustrations are provided for each species.