Mattias Edman

LOCAL DISPERSAL SOURCES STRONGLY AFFECT COLONIZATION PATTERNS OF WOOD-DECAYING FUNGI ON SPRUCE LOGS

Coarse woody debris (CWD) is an important habitat for many species in forest ecosystems. However, forestry has decreased the abundance of CWD so that many wood-dependent species have become threatened. To alleviate this problem, guidelines for a more biodiversity-oriented forestry focus on increasing CWD in managed forests. Un- fortunately, how this increase is to be allocated on a landscape scale is not well understood. The present study reports an experiment in which freshly cut logs of varying sizes were placed in stands with contrasting abundance of natural CWD and subsequently varying pools of wood-inhabiting species. The first six years of colonization by wood fungi show that local abundance and composition of the fungal flora strongly influenced colonization. Higher species richness was observed in CWD-rich sites, and several species were more frequent on the experimental logs at CWD-rich sites. The strong within-site effect is in- terpreted as resulting from high spore deposition from the local species pool. This is supported by spore deposition estimates of Fomitopsis rosea, a red-listed species that only occurred on experimental logs at the CWD-rich sites. F. rosea had a 9-180 times higher spore deposition at the CWD-rich sites compared to the CWD-poor sites. The species richness and composition on small logs differed from that of large logs with higher richness on the latter. The results strongly suggest that restoration efforts would be more efficient if directed toward sites close to CWD-rich sites and that preferably large logs should be created.

Spatial pattern of downed logs and wood‐decaying fungi in an old‐growth Picea abies forest

. Since many wood-living forest species are influenced by the dynamics of coarse woody debris (CWD), information about the spatial pattern of CWD under natural conditions is essential to understand species distributions. In this study we examined the spatial pattern of downed logs and wood-decaying fungi in an old-growth boreal Picea abies forest in northwestern Sweden that is governed by gap-phase dynamics. The spatial pattern of wood-decaying fungi was studied to draw conclusions about species dispersal abilities. A total of 684 logs with a diameter > 10 cm were mapped and analysed with Ripleys K-function. The distribution of all logs taken together displayed a significant aggregated pattern up to 45 m. The different decay stages also deviated from random expectations. Fairly fresh logs and logs in the middle decay stage were clumped up to about 25 and 35 m respectively, and late decayed logs aggregated up to 95 m. Logs with diameters from 10–29 cm were aggregated up to 25 m, whereas logs ≥30 cm diameter were randomly distributed. The result suggests that gap-dynamics do have an impact on the spatial pattern of the CWD, creating fine-scale clumping. The random distribution of large logs may result from the slightly regular spacing of large living trees. The spatial patterns of 16 species (n > 20) of wood-decaying fungi were analysed with Ripleys K-function. Three patterns were aggregated, for Gloeophyllum sepiarium, Coniophora olivacea and Vesiculomyces citrinus. These results indicate that the distribution of most species at the stand level is generally not influenced by dispersal limitations.

Temporal variation of wood-fungi diversity in boreal old-growth forests : implications for monitoring

Monitoring programs that supply reliable and sufficient information on numbers and types of organisms are essential for following changes in biodiversity. In boreal Fennoscandia, forest-dwelling sp ...

FUNGI AND WIND STRONGLY INFLUENCE THE TEMPORAL AVAILABILITY OF LOGS IN AN OLD-GROWTH SPRUCE FOREST

Coarse woody debris (CWD) is a key habitat for many species in forest ecosystems. To ensure the long-term survival of such species, forest management regimes must include measures that promote dead wood dynamics similar to those of natural forests. Thus, information on CWD dynamics under natural conditions is required, including data pertaining to the underlying agents of disturbance. This study examines modes of mortality, decay rates, and temporal patterns in the availability of Picea abies logs in a Swedish old-growth forest affected by internal, small-scale disturbance. All 684 logs in a 6.6-ha plot were mapped and classified into one of six decay classes. Logs in the early stages of decay were examined for the presence of heart-rot fungi. Six years later all logs were re-inventoried, including newly formed logs. Matrix models based on the transition rates between decay classes showed that it took about 60 years for 90% of the logs to decay beyond class 6 (a deformed trunk with soft wood). Large logs (> 26 cm) decayed 40% more slowly than small logs (< 25 cm). The initial volume of logs was 37.6 m3/ha but increased to 44.8 m3/ha after six years. In addition, there was a large shift in the decay-class distribution. The volume of logs in early and late decay classes increased by 71% and 45%, respectively, while the volume of logs in the intermediate decay classes decreased by 32%. The fluctuations appear to result from pulses in mortality, driven by a combination of strong winds and the heart-rot fungus, Phellinus chrysoloma, which was present in more than 30% of all logs at an early stage of decay. These results show that large temporal fluctuations in dead wood also occur in the absence of large-scale disturbance, and that heart-rot fungi are important factors driving the overall dynamics of dead wood. Since many wood-inhabiting species are naturally rare and have very specific substrate demands, such temporal variability in dead wood availability may have effects on biodiversity and should be taken into account when designing small, protected forest areas.

Diverse ecological roles within fungal communities in decomposing logs of Picea abies

Fungal communities in Norway spruce (Picea abies) logs in two forests in Sweden were investigated by 454-sequence analyses and by examining the ecological roles of the detected taxa. We also investigated the relationship between fruit bodies and mycelia in wood and whether community assembly was affected by how the dead wood was formed. Fungal communities were highly variable in terms of phylogenetic composition and ecological roles: 1910 fungal operational taxonomic units (OTUs) were detected; 21% were identified to species level. In total, 58% of the OTUs were ascomycetes and 31% basidiomycetes. Of the 231 337 reads, 38% were ascomycetes and 60% basidiomycetes. Ecological roles were assigned to 35% of the OTUs, accounting for 62% of the reads. Wood-decaying fungi were the most common group; however, other saprotrophic, mycorrhizal, lichenized, parasitic and endophytic fungi were also common. Fungal communities in logs formed by stem breakage were different to those in logs originating from butt breakage or uprooting. DNA of specific species was detected in logs many years after the last recorded fungal fruiting. Combining taxonomic identification with knowledge of ecological roles may provide valuable insights into properties of fungal communities; however, precise ecological information about many fungal species is still lacking.

Wood-disk traps provide a robust method for studying spore dispersal of wood-decaying basidiomycetes

Spore traps consisting of disks containing monokaryotic mycelia as bait were tested to find a robust, long-time sampling method for studying dispersal of wood-decaying basidiomycetes. In total, 288 disks, 48 for each of six fungal species, were exposed 2 wk at 12 sites in northern Sweden. Both common and rare fungi were used, and the longest distance to a potential dispersal source exceeded 3 km. After 3–16 wk of incubation in the laboratory, the disks were investigated for spore hits. These were detectable both microscopically, by the presence of hyphal clamps, and macroscopically, by mycelial incompatibility zones. Spore traps resisted rain and freezing temperatures well, and spore hits from all species were found at all 12 sites. We argue that lengthy sampling makes it possible to detect low rates of spore deposition, aiding in the study of long-distance dispersal and dispersal of rare species. In addition, because several spore hits can be recognized in the same trap, spore deposition of wood-decaying fungi can be characterized with quantitative data.

Competitive outcomes between wood-decaying fungi are altered in burnt wood.

Fire is an important disturbance agent in boreal forests where it creates a wide variety of charred and other types of heat-modified dead wood substrates, yet how these substrates affect fungal community structure and development within wood is poorly understood. We allowed six species of wood-decaying basidiomycetes to compete in pairs in wood-discs that were experimentally burnt before fungal inoculation. The outcomes of interactions in burnt wood differed from those in unburnt control wood for two species:Antrodia sinuosanever lost on burnt wood and won over its competitor in 67% of the trials compared to 40% losses and 20% wins on unburnt wood. In contrast, Ischnoderma benzoinumwon all interactions on unburnt wood compared to 33% on burnt wood. However, the responses differed depending on the identity of the competing species, suggesting an interaction between competitor and substrate type. The observed shift in competitive balance between fungal species probably results from chemical changes in burnt wood, but the underlying mechanism needs further investigation. Nevertheless, the results indicate that forest fires indirectly structure fungal communities by modifying dead wood, and highlight the importance of fire-affected dead wood substrates in boreal forests.

Increased CO2 evolution caused by heat treatment in wood-decaying fungi

Wood-decaying fungi are regarded as the main decomposers of woody debris in boreal forests. Given that fungal respiration makes a significant contribution to terrestrial carbon flows, it is important to understand how the wood-decaying fungal metabolism is regulated in relation to different environmental conditions and disturbances. In the present study, we investigated the effect of temperature stress on wood decomposition rate in 18 species of wood-decaying fungi, representing a broad range of species–habitat associations. Heat shock duration and temperature were calibrated to match the conditions of a forest fire. We found a general increase in fungal decay rate after heat shock; the response was more pronounced in species associated with fire-prone forests. The underlying mechanism is unclear, but possibly relates to an up-regulation at the cellular level in response to heat shock. Our results show that the decomposition rate of dead wood can be strongly affected by environmental triggers.

Assemblage composition of fungal wood-decay species has major influence on how climate and wood quality modify decomposition

The interactions among saprotrophic fungal species, as well as their interactions with environmental factors, may have a major influence on wood decay and carbon release in ecosystems. We studied the effect that decomposer diversity (species richness and assemblage composition) has on wood decomposition when the climatic variables and substrate quality vary simultaneously. We used two temperatures (16 and 21°C) and two humidity levels (70% and 90%) with two wood qualities (wood from managed and old-growth forests) of Pinus sylvestris. In a 9-month experiment, the effects of fungal diversity were tested using four wood-decaying fungi (Antrodia xantha, Dichomitus squalens, Fomitopsis pinicola and Gloeophyllum protractum) at assemblage levels of one, two and four species. Wood quality and assemblage composition affected the influence of climatic factors on decomposition rates. Fungal assemblage composition was found to be more important than fungal species richness, indicating that species-specific fungal traits are of paramount importance in driving decomposition. We conclude that models containing fungal wood-decay species (and wood-based carbon) need to take into account species-specific and assemblage composition-specific properties to improve predictive capacity in regard to decomposition-related carbon dynamics.