Fungal successions on pine needles fallen at different seasons: The succession of surface colonizers

Field experiments were carried out to investigate influences of seasonal change on the fungal succession occurring on the surface of decaying pine needles at a moder site in Japan. At different seasons, the needles fallen for a short period were collected and marked, then placed on the surface of the O horizon. The needles were removed at intervals and their fungal communities were examined by using a washing technique. Unlike the successions of interior colonizers studied at the same time, those of surface colonizers observed on the fallen needles at four different times are roughly similar to each other.Thysanophora penicillioides was the major first colonizer on the sample needles from the O horizon, andTrichoderma species followed it. In an experiment started in late autumn, three dematiaceous fungi,Chloridium viride var.chlamydosporis, Sporidesmium omahutaense, andChalara sp., commonly occurred and contributed to the darkening of colonized needles. Seasonal variation in climate may have a stronger effect on internal colonizers than external colonizers of needles. Contributions from Sugadaira Montane Research Center, No. 165.     

Mycofloral succession onPinus densiflora needles on a moder site

Mycofloral succession on decaying pine needles in aPinus densiflora forest on a moder site was investigated in Sugadaira, Nagano Pref., central Japan. Dead needles on the tree, fallen needles obtained from two recognizable sublayers of the L layer and the upper sub-layer of the F₁ layer in the organic horizon were examined for their fungal flora using both washing and surface sterilization techniques. The major interior colonizer in freshly fallen needles varied with the season:Chaetopsina fulva in summer andSelenosporella curvispora in the other seasons.Thysanophora penicillioides was a remarkable external colonizer of freshly fallen needles in summer, while soil fungi were external colonizers of such needles in the other seasons. A possible successional change of major fungi with the needle decay was suggested. The observed seasonal alternation of the species colonizing freshly fallen needles was discussed in relation to climatic conditions. Contributions from Sugadaira Montane Research Center, No. 152.     

Fungal succession on pine needles in Germany

The mycofloral succession on the needles ofPinus sylvestris was investigated in Tübingen, southwest Germany. Dead needles attached to the branches (D-type), those caught on branches (C-type) and three types of fallen needles, i.e., freshly fallen (L-type), slightly discolored (OL-type) and almost black needles (F-type) were examined for their fungal flora. Common primary saprophytes were rich on the dead needles on the tree, and on the L-type needles. They were replaced by successive species that contained the well-known species preferring pine needles as their substratum, such asVerticicladium trifidum orSympodiella acicola. Their ecological niches in pine leaf litter and their distribution patterns from a biogeographical viewpoint were discussed.     

Enzyme activities of fungi associated with Picea abies needles

Decomposition of Picea abies needles and production of extracellular enzymes involved in decomposition of lignin, cellulose, hemicelluloses and other organic compounds were studied in fungal strains of interior needle colonizers isolated from needles in different stages of decomposition (attached to trees, and early and late decomposition stages in the litter horizon). In total, 12 strains of ascomycetes (members of Helotiales, Hypocreales, Dothideales, Diaporthales and Eurotiales) and four basidiomycetes (Polyporales, Agaricales and Russulales) were tested. Significant decomposition of needles was recorded for all fungal isolates. All isolates produced cellobiohydrolase, β-glucosidase, β-xylosidase, N-acetylglucosaminidase, α-glucosidase, phosphatase and arylsulfatase and most fungi also produced endocellulase, endoxylanase and laccase in needle litter. In addition, other hemicellulases were produced by all strains. Mn-peroxidase was only produced by two basidiomycetes. Although enzyme activities varied, fungi associated with needles on fallen trees exhibited enzyme production comparable with later litter colonizers, and there was no significant difference in enzyme production between ascomycete and basidiomycete strains.     

Colonization and succession of fungi during decomposition of Swida controversa leaf litter

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.     

Succession of fungi and fauna during decomposition of needles in a small area of Scots pine litter

During micromorphological investigations on Scots pine litter, several decomposition stages have been recognized on fallen pine needles, each being associated with the activity of animal and microbial organisms, both. To well-known fungal successions that have been so far described by mycologists we must add succession of animal groups such as nematodes, amoebae, enchytraeids, sciarid larvae, oribatid mites and earthworms. A bacterial development was observed in the L₂ layer, following penetration by microfauna (nematodes, amoebae). After that stage pine needles were actively tunnelled by enchytraeids, sciarid larvae and oribatid mites and at the same time were nibbled on by epigeic earthworms (L₂ and F₁ layers). When the fine root system of pine developed through accumulated old needles (F₁ layer), mycorrhizal fungi penetrated the needles and seemed to impede any further bacterial development. Pine foliar tissues were progressively incorporated into the fecal material of earthworms and other members of the soil fauna. A more realistic scheme was suggested for plant litter decomposition in moder humus.     

Dematiaceous hyphomycetes inhabiting decaying blackish needles ofAbies firma and their distribution in the Kanto district, Japan

Dematiaceous mitosporic fungi darkening decaying fir needles on the ground were studied. Fungal communities on decaying, blackish fir needles were investigated in nine sites of the Kanto district, Japan, using a washing method. A total 108 taxa was recorded from 540 sampled needles. Among abundantly occurring dematiaceous fungi,Anungitea continua, A. uniseptata andEndophragmiella uniseptata were recognized as the major colonizers, forming a hyphal network on the surface of decaying fallen needles and darkening them. The effects of climate on the distributions of seven dematiaceous fungi included the major colonizers were analyzed. The abundance (proportion of needles colonized by a fungal species) ofChaetopsina fulva showed a significantly positive correlation with annual mean air temperature at each sampling site. No other significant correlations between the selected climatic factors and the distributions of dematiaceous fungi were recognized. Contribution No. 176 from Sugadaira Montane Research Center, University of Tsukuba.     

Decomposition of cellulose by the species of the fungal succession degrading Abies alba needles

Abstract Fifteen species of the fungal succession degrading Abies alba Mill. needles were tested for their ability ti decompose filter paper cellulose. Pure cultures with or without C-cosubstrates or with aqueous green needle extracts as culture medium were set up. Cellulolytic species were found throughout the succession. The activities of fungi colonizing only aged litter were inhibited by natural water soluble condensed tannins. The activities of fungi which colonize senescing needles were not inhibited. Biochemical microenvironmental factors seemed to be important determinants of the fungal community structure.     

Interactions between needles of Pinus resinosa and ectomycorrhizal fungi

Relatively little is known about the factors controlling ectomycorrhizal fungal communities. One possible factor is forest litter chemistry. In a series of experiments we demonstrated that the growth of ectomycorrhizal fungi able to colonize red pine ( Pinus resinosa Ait.) are differentially affected by red pine needles and needle chemical components. For example, water extracts of pine needles stimulated the growth of Suillus intermedius (Smith & Thiers) Smith & Thiers and inhibited the growth of Amanita rubescens Pers. Catechin and epicatechin gallate, components of the water extract, acted similarly to the extract. The volatile compounds α- and β-pinene also had differential effects on the growth of the various species of ectomycorrhizal fungi. Our results suggest that forest litter chemistry has the potential differentially to affect the growth of ectomycorrhizal fungal species and so could affect the structure of ectomycorrhizal fungal communities.     

Fungal Diversity of Norway Spruce Litter: Effects of Site Conditions and Premature Leaf Fall Caused By Bark Beetle Outbreak

Fungi play an important role in leaf litter decomposition due to their ability to break down the lignocellulose matrix, which other organisms are unable to digest. However, little is known regarding the factors affecting components of fungal diversity. Here, we quantified richness of internal fungi in relation to litter nutrient and phenolic concentrations, sampling season (spring or fall), and premature leaf shedding due to low precipitation and infestation of bark beetles (mainly Ips typographus and Ips duplicatus). The study was conducted in 37-year-old Norway spruce [Picea abies (L.) Karst.] stands, with three plots each in mixed forest (MF) and coniferous forest (CF) site conditions in south-central Poland. Fifty-four species of sporulating fungi were identified in 2,330 freshly fallen needles sampled during 2003-2005, including 45 species in MF and 31 in CF. The significantly higher number of species in MF was likely related to moister conditions at that site. Among isolated fungi, 22% (12 species) were identified as endophytes of Norway spruce in prior studies. During spring of 2005, we found less than half the number of isolates and fungal species at each forest site as compared to fall for the two prior years. This pattern was observed in typical soil fungi (e.g., Penicillium daleae, Penicillium purpurogenum) and endophytes/epiphytes (e.g., Aureobasidium pullulans, Alternaria alternata, Cladosporium spp., and Lophodermium piceae). Premature shedding of needles was the most likely cause of this decline because it shortened the time period for fungi to infect green needles while on the tree. For all sites and sampling periods, richness of internal fungi was strongly and positively related to the age of freshly fallen litter (assessed using needle Ca concentration as a needle age tracer) and was also negatively related to litter phenolic concentration. Richness of internal fungi in freshly fallen litter may be adversely affected by low soil moisture status, natural inhibitors slowing fungal colonization (e.g., phenolics) and biotic (e.g., insect infestation) and abiotic (e.g., drought) factors that shorten leaf life span.     

Colonization,Species Composition,and Conidial Production of Aquatic Hyphomycetes on Chirpine Needle Litter in a Freshwater Kumaun Himalayan Stream

Aquatic hyphomycetes colonizing the submerged chirpine (pinus roxburghii SARG .) needle litter in a high altitude, Kumaun Himalayan stream were studied. 15 species belonging to different genera of aquatic Hyphomycetes have been recognized as the colonizers of chirpine needle litter. Clavariopsis aquatica, Heliscus lugdunensis, Lunulospora cymbiformis, Triscelophorus acuminatus and T. monosporus were found with a high frequency of occurrence. The conidial production was highest in Flagellospora penicillioides, however, Campylospora chaetocladia, L. cymbiformis and T. acuminatus had less number of conidia per unit area of pine needles. The chirpine needle litter decomposition in the freshwater habitat is also discussed.     

Phyllosphere fungi on living and decomposing leaves of giant dogwood

Phyllosphere fungi on living leaves and their succession on decomposing leaves were studied on giant dogwood (Swida controversa). A total of 12 and 34 fungal species were isolated from the interior and surface, respectively, of living leaves, and 15 frequent species were considered as phyllosphere fungi. Six of these 15 species were also frequent on decomposing litter. Characteristic successional trends were observed in the 6 phyllosphere fungi during decomposition. The sum of frequencies of endophytes decreased as decomposition progressed, and no endophytes were isolated from the litter at the 11th month of decomposition. The sum of frequencies of epiphytes increased as decomposition progressed. Endophytes and epiphytes showed different responses to litter mass loss and concentrations of nitrogen, lignin, and total carbohydrates during the decomposition process. These results suggested that epiphytes may survive on decomposing leaves as primary decomposers on the ground, thereby excluding endophytes by competition for available energy sources, and that epiphytes may have a greater contribution to decomposition than endophytes in dogwood leaves.     

Fungal succession in the needle litter of a montane Picea abies forest investigated through strain isolation and molecular fingerprinting

Precise knowledge of the fungal succession in the litter of coniferous forests will facilitate understanding litter decomposition, in which fungi play a major role. We investigated the development of a fungal community during 3 yr of Picea abies litter decomposition in three control forest sites and three sites where bark-beetle attacks had killed adult trees and stopped the yearly input of fresh litter, using both cultivation from needles and terminal restriction-fragment length polymorphism analysis. The two methods revealed similar dominant species during the fungal succession. Members of the Dothideales, Eurotiales and Helotiales predominated during the initial stage of decay, whereas members of Agaricales appeared only occasionally during this stage. The onset of the latter began from the seventh month, with a peak occurring after 1 yr. Bark-beetle attacks hastened litter decomposition and decreased fungal diversity only during the initial stages of decomposition.     

Succession of microfungi during Pistacia lentiscus litter decomposition in a Sardinian Mediterranean maquis

Abstract

Changes in the microfungal community developing on Pistacia lentiscus L. leaf litter were monitored from February 2001 (senescent leaves) to December 2002 using litter bags. The Principal component analysis of the 16 samples showed a microfungal succession related to the progressive decomposition of the substratum. The Correspondence analysis of fungal colonizers with Rf > 10 revealed three main groups succeeding during the study period. The co-occurrence relationships (on the same leaf) among the major colonizers were analysed. The specialized saprotrophs on P. lentiscus litter: Asterostomella sp. 1 and Endophragmiella boewei were identified as principal colonizers in the mature community.     

Changes in fungal community of Scots pine (Pinus sylvestris) needles along a latitudinal gradient in Sweden

Conifer needles are typically long lived and can host a diverse community of fungal species with various effects on their host tree. The purpose of this study was to analyse shifts in the fungal community of Scots pine (Pinus sylvestris) needles on different spatial scales using 454 pyrosequencing. The fungal community composition changed gradually along a north-south gradient through Sweden, representing boreal to temperate vegetation zones. OTU richness and Shannon's diversity index increased with increasing latitude, but only in naturally regenerated forests. On the tree level, needles with symptoms of disease hosted a more diverse mycobiota compared to healthy needles, presumably supporting more pathogenic or saprotrophic species. This study provides a better insight into the patterns of fungal communities of Scots pine needles and highlights the need for further experimental research to identify specific environmental factors shaping the abundance of different fungal species.     

Cellulase activities in senescent conferous needles and in needle litter naturally colonized by various fungi

Abstract Cellulase activity and phenol content were measured in water extracts from needles collected from Abies alba Mill. forest. Variations in cellulolytic activities in senescent needles and litter were due to the diversity of fungal colonizers and to interspecific differences in activities over the course of colonization. Phenol content was transformed quantitatively and quanlitatively in presence of fungi, therefore the biochemical environment in which cellulolytic enzymes were active had been modified.     

Nitrogen availability affects saprotrophic basidiomycetes decomposing pine needles in a long term laboratory study

Fungi, especially basidiomycetous litter decomposers, are pivotal to the turnover of soil organic matter in forest soils. Many litter decomposing fungi have a well-developed capacity to translocate resources in their mycelia, a feature that may significantly affect carbon (C) and nitrogen (N) dynamics in decomposing litter. In an eight-month long laboratory study we investigated how the external availability of N affected the decomposition of Scots pine needles, fungal biomass production, N retention and N-mineralization by two litter decomposing fungi – Marasmius androsaceus and Mycena epipterygia. Glycine additions had a general, positive effect on fungal biomass production and increased accumulated needle mass loss after 8 months, suggesting that low N availability may limit fungal growth and activity in decomposing pine litter. Changes in the needle N pool reflected the dynamics of the fungal mycelium. During late decomposition stages, redistribution of mycelium and N out from the decomposed needles was observed for M. epipterygia, suggesting autophagous self degradation.     

Patterns of Richness and Abundance in a Tropical African Leaf‐litter Herpetofauna1

I compared species richness and habitat correlates of leaf‐litter herpetofaunal abundance in undisturbed and selectively logged forests, and an abandoned pine plantation in Kibale National Park, Uganda. I sampled 50 randomly located 25 m² litter plots in each area during the wet and dry seasons in 1997. Ten anuran, five lizard, and three snake species were captured in plots over the study. Assemblage composition was most similar at logged and unlogged sites. The logged forest herpetofauna had higher species richness and abundance than the unlogged forest, but diversity was greater in the unlogged forest due to greater evenness. In contrast, the pine plantation site had the highest richness, abundance, and evenness of the three study sites, but species composition was distinct from the other areas. Herpetofaunal densities were significantly lower in all three areas during the dry season than in the wet season. During the dry season, soil moisture, litter mass, topography, shrub cover, and number of fallen logs were significant positive predictors of herpetofaunal presence in litter plots, but only soil moisture was significant in the wet season. The interaction of moisture and topography appears to be important in determining seasonal patterns of litter herpetofaunal distribution. Comparison of litter herpetofaunal studies across the tropics have shown that mid‐elevation faunas generally support fewer species than lowland faunas. Compared with other tropical mid‐elevation litter faunas, Kibale supports an intermediate number of species, but at lower densities than observed at any other mid‐elevation site reported in the literature.     

Microfungi associated with Abies needles and Betula leaf litter in a subalpine coniferous forest

We investigated microfungal assemblages on leaf litter within a subalpine forest in central Japan and their variation with season, litter depth, and litter species. Microfungal assemblages were compared for Abies needles and Betula leaf litter collected from litter and fermentation layers of the forest floor during the growing season in spring, summer, and autumn. A total of 35 and 42 species were isolated from Abies needles and Betula leaf litter, respectively. The observed variation in microfungal assemblages was primarily attributable to seasonal differences. The frequencies of Trichoderma viride, Volutella ciliata, Mucor sp., and Umbelopsis ramanniana increased in summer, leading to a high degree of similarity of microfungal assemblages in different litter depths and litter species. Microfungal assemblages on Abies needles in spring and autumn and those on Betula leaves in spring were characterized by Trichoderma viride, V. ciliata, Thysanophora penicillioides, Trichoderma polysporum, and (or) Mortierella alpina. Microfungal assemblages on Betula leaves in autumn were characterized by the absence of these species and the occurrence of Cladosporium cladosporioides. The results were discussed with an emphasis on the role of microfungi in decomposition processes and the impact on fungi of predicted future increases in global temperature.     

Organic chemical and nutrient dynamics in decomposing beech leaf litter in relation to fungal ingrowth and succession during 3-year decomposition processes in a cool temperate deciduous forest in Japan

Decomposition processes of beech leaf litter were studied over a 3-year period in a cool temperate deciduous forest in Japan. Organic chemical and nutrient dynamics, fungal biomass and succession were followed on upper (Moder) and lower (Mull) of a forest slope. Litter decomposition rates were similar between the sites. Nutrient dynamics of the decomposing litter was categorized into two types: weight changes in nitrogen and phosphorus showed two phases, the immobilization (0–21 months) and the mobilization phase (21–35 months), while those in potassium, calcium and magnesium showed only the mobilization phase. The rate of loss of organic chemical constituents was lignin < holocellulose < soluble carbohydrate < polyphenol in order. The changes in lignocellulose index (LCI), the ratio of holocellulose in lignin and holocellulose, were significantly correlated to the changes in nitrogen and phosphorus concentrations during the decomposition. During the immobilization phase, increase in total fungal biomass contributed to the immobilization of nitrogen and phosphorus. The percentage of clamp-bearing fungal biomass (biomass of the Basidiomycota) to total fungal biomass increased as the decomposition proceeded and was significantly correlated to LCI. Two species in the xylariaceous Ascomycota were dominantly isolated by the surface sterilization method from decomposing litter collected in the 11th month. The organic chemical, nitrogen and phosphorus dynamics during the decomposition were suggested to be related to the ingrowth, substrate utilization and succession of the Xylariaceae and the Basidiomycota. Twenty-one species in the other Ascomycota and the Zygomycota isolated by the washing method were classified into three groups based on their occurrence patterns: primary saprophytes, litter inhabitants and secondary sugar fungi. These species showed different responses to LCI and soluble carbohydrate concentration of the litter between the groups.