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A diverse array of fungi take part in decomposition, but the variability of their decomposing ability is not fully understood. A total of 49 isolates of Ascomycota and Basidiomycota were obtained from bleached areas of leaf litter in a subtropical forest in southern Japan, and their ability to decompose leaves and recalcitrant compounds was quantified in pure culture. Mass loss of leaves of Castanopsis sieboldii (Fagaceae) and Schima wallichii (Theaceae) was evaluated at 20 C for 12 wk in vitro. Fungi caused a loss of -0.4% to 34.3% of the original leaf mass. The greatest mass loss was caused by four isolates of Mycena (Tricholomataceae). Isolates of Lachnocladiaceae caused greater mass loss of recalcitrant compounds, registered as acid-unhydrolyzable residue (AUR), which includes lignin, relative to Xylariaceae. Isolates of Rhytismataceae, Lachnocladiaceae, Marasmiaceae, and Omphalotaceae exhibited selective decomposition of AUR, Mycena exhibited simultaneous decomposition of AUR and components other than AUR, and Xylariaceae exhibited selective decomposition of components other than AUR. Mass losses of leaves and AUR caused by each fungal isolate were similar for C. sieboldii and S. wallichii . The Mycena isolates obtained from C. sieboldii caused greater mass losses of leaves and AUR than those obtained from the other tree species, suggesting a "home-field advantage" of decomposing potentialities, with implications for natural interactions beyond the in vitro system evaluated here.

Fungal assemblages in live, newly shed and partly decomposed leaves of Camellia japonica were investigated with a clone library analysis to assess the fungal diversity and succession in a subtropical forest in southern Japan. Partly decomposed leaves were divided into bleached and adjacent nonbleached portions to estimate the fungi functionally associated with lignin decomposition in the bleached portions, with an emphasis on Coccomyces sinensis (Rhytismataceae, Ascomycota). From 144 cloned 28S ribosomal DNA (rDNA) sequences, 48 operational taxonomic units (OTUs) were defined based on a sequence similarity threshold of 98%. Forty-one (85%) of the 48 OTUs belonged to the Ascomycota and seven OTUs (15%) to the Basidiomycota. Twenty-six OTUs (54%) were detected only once (singletons). The number of OTUs and the diversity indices of the fungal assemblages in the different leaves were in this order: live leaves > newly shed leaves > bleached portions > nonbleached portions of partly decomposed leaves. The fungal assemblages were similar in newly shed leaves and the bleached portions of partly decomposed leaves. Ligninolytic fungi of the genera Coccomyces, Lophodermium and Xylaria were frequently detected in the bleached portions. OTU3, identified as Coccomyces sinensis, was detected in live and newly shed leaves and the bleached portions of partly decomposed leaves, suggesting that this fungus latently infects live leaves, persists after leaf fall and takes part in lignin decomposition.

We tested the decay abilities of 28 isolates from 28 lignicolous fungal species (Basidiomycota, Ascomycota and Zygomycota) with the pure culture test. We used beech wood powder in varying moisture conditions and decay stages (nondecayed, intermediately decayed and well decayed) as substrates. The weight loss in wood powder was -0.2-17.8%. Five isolates of Basidiomycota (Bjerkandera adusta, Mycena haematopus, Omphalotus guepiniformis, Trametes hirsuta, Trametes versicolor) caused high weight losses in nondecayed wood. We detected significant effects of decay stage on weight loss in wood in most isolates tested, whereas moisture content rarely had an effect on weight loss. Among Basidiomycota and Xylariaceae in Ascomycota weight loss was greater for nondecayed wood than for intermediately and well decayed wood. In contrast four isolates in Ascomycota (Scytalidium lignicola, Trichoderma hamatum, T. harzianum, T. koningii) caused substantial weight loss in intermediately and well decayed wood, although they rarely caused weight loss in nondecayed wood. Zygomycota caused low weight loss in wood. Wood decay stages also affected decomposition of wood chemical components. Acid-unhydrolyzable residue (AUR) decomposition was reduced, whereas holocellulose decomposition was stimulated by some strains of Basidiomycota and Ascomycota in well decayed wood. T. harzianum in particular caused significant weight loss of holocellulose in well decayed wood, although this fungus caused negligible weight loss of both AUR and holocellulose in nondecayed wood. We discuss these changes in the decay patterns of AUR and holocellulose with varying wood decay stages in relation to the role of fungal decomposition of woody debris in forests.

Seasonal and leaf age-dependent variations in the endophytic and epiphytic phyllosphere fungal assemblages of Camellia japonica were examined and compared. Live leaves of C. japonica were collected in four seasons (May, Aug, Nov, Feb), and fungi were isolated from healthy-looking leaves of 0, 1, 2 and 3 y old. The infection rate and total number of endophytic fungi increased May-Feb, and species richness of endophytes increased as leaves aged. In contrast the infection rate of epiphytic fungi was 100% for all leaf ages at every sampling date. The total number of epiphytic fungi isolated was greatest in May and lowest in Aug. The species richness of epiphytes did not differ significantly by season or leaf age. Eight fungal species were recorded as major phyllosphere fungi of C. japonica. Seasonal variations were detected for the frequencies of Colletotrichum gloeosporioides, C. acutatum, and epiphytes Pestalotiopsis sp.1, Aureobasidium pullulans, Phoma sp.1 and Ramichloridium sp., whereas the frequency of the endophyte Geniculosporium sp.1 varied with leaf age. The frequency of the epiphyte Cladosporium cladosporioides varied with both season and leaf age.

The effect of litter type and incubation temperature on the ability of fungi to decompose leaf litter of subalpine trees was examined by a pure-culture test. Mass loss of Abies needle and Betula leaf litter and utilization patterns of lignin and carbohydrates were investigated under two temperature conditions (20 C and 10 C) and compared for 29 species in basidiomycetes, ascomycetes and zygomycetes. The decomposing ability was generally higher in basidiomycetes than in ascomycetes and zygomycetes. Mass loss (% original mass) of litter was higher in Betula than in Abies and higher at 20 C than at 10 C. The 29 fungi were divided into lignocellulose decomposers, cellulose decomposers and sugar fungi based on their substrate utilization in Abies and Betula litter. Mass loss of lignin and carbohydrates by lignocellulose and cellulose decomposers was higher in Betula than in Abies. Mass loss of carbohydrates was higher at 20 C than at 10 C, but the temperature did not influence mass loss of lignin, indicating lignin decomposition by fungi was less sensitive to temperature than carbohydrate decomposition. Lignin/carbohydrate loss ratio (L/C) of Collybia spp. that caused selective delignification was lower at 20 C than at 10 C. These results indicate that the decomposability of litter, lignin and carbohydrate was different between Abies and Betula and that temperature affected not only the rate at which fungi decompose litter but also the ability of fungi to use lignin and carbohydrates.

Decomposition processes of Swida controversa leaves were investigated in initially sterilized (fungi-excluded) and nonsterilized freshly fallen leaves to examine the relationship between chemical changes and fungal succession during decomposition and the effect of exclusion of previously established phyllosphere fungi from leaves on subsequent decomposition and fungal succession. Fifteen species were isolated frequently from decomposing leaves with surface-disinfection and washing methods. These fungi were divided into early and late colonizers according to their occurrence during decomposition. The 1.5 y decomposition process was divided into three stages characterized by different dominant organic chemical constituents. A clear relationship was demonstrated between chemical changes and fungal succession. Total hyphal length and frequencies of some early colonizers were reduced in initially sterilized leaves at 3 wk, but this had no significant effect on loss of litter mass or chemical changes during the first 3 wk or on the subsequent decomposition and fungal succession.

Functional biodiversity of fungi in larch (Larix leptolepis) forests needle-litter decomposition was examined by a pure-culture test. Weight loss of larch-needle litter, utilization pattern of lignocellulose and chemical composition of remaining litter were investigated and compared for 31 isolates in 27 species of basidiomycetes and ascomycetes. Weight loss (% original weight) of litter ranged from -2.0% to 14.2%. Mean weight loss of litter caused by the basidiomycetes was not significantly different from that caused by the ascomycetes. Basidiomycetes caused loss of lignin and carbohydrates in variable proportions, while ascomycetes exclusively attacked carbohydrates without delignification. The content of lignin and nitrogen in remaining litter was not significantly correlated when both basidiomycetes and ascomycetes were included. However, the correlation coefficient was significant when the relationship was examined separately for basidiomycetes, indicating that the degree of selective delignification determined the final nitrogen content in litter. Possible effects of fungal colonization on needle-litter decomposition in larch forests are discussed.

The litter decomposing ability of 79 fungal isolates (41 genera, 60 species) was assessed with the pure culture decomposition test. The isolates were collected qualitatively in a cool temperate deciduous forest in Japan during a 21-mo period. Loss of original weight of sterilized litter ranged from 0.1% to 57.6%. Six isolates in the Basidiomycota caused high weight losses ranging from 15.1% to 57.6%. Fourteen isolates in Xylaria and Geniculosporium (the Xylariaceae and its anamorph) also caused high weight losses ranging from 4.0% to 14.4%. Other isolates in the Ascomycota and associated anamorphs and in the Zygomycota caused low weight losses on mean. Six fungi in the Basidiomycota, and all in the Xylariaceae showed a bleaching activity of the litter and caused lignin and carbohydrate decomposition. Mean lignin/weight loss ratios (L/W) and lignin/carbohydrate loss ratios (L/C), were 0.9 and 0.7 for the Basidiomycota and 0.7 and 0.4 for the Xylariaceae, respectively. Significant differences were found in L/W and L/C between the two groups when the result of Xylaria sp. that showed marked delignification was excluded. These differences in lignin and carbohydrate utilization patterns are discussed in relation to the structural and the chemical properties of the decomposed litter and to the implications for organic chemical changes during litter decomposition processes.