Fungal Ecology最新文献

Hollow trees are crucial for forest biodiversity but are becoming increasingly rare in many ecosystems, including the Scots pine forests of northern Europe. Here, we inoculated heartwood of live Scots pine trees with the fungal keystone species Porodaedalia pini to initiate tree hollowing. The fungus was inoculated in 50-, 110- and 170-year old stands, using wood dowels containing mycelia. Three different strains were used to test for intraspecific variation. Molecular analysis of samples from inoculated trees seven years after treatment showed that 67% were successfully colonised, with no differences between stands. Fungal strain had no effect on colonisation success. Our findings suggest that inoculation with P. pini has the potential to be an efficient method to restore a key ecological process, tree hollowing, in degraded Scots pine forests. The possibility of initiating the process even in young trees may be a way to accelerate the formation of hollow pines in younger forests.

Morchella galilaea is unique among morels by its autumnal fruiting and a worldwide but disjunct distribution, strongly biased towards islands. The drivers of this reversed seasonality and transcontinental dispersal remain poorly understood. New records of M. galilaea from several islands of the Mediterranean, and from the Reunion Island in the Indian Ocean, all unveiled here, invited us to revisit and discuss the biogeography, phenology and ecology of this intriguing morel. Our ecological and molecular findings do not support recent anthropogenic introductions as causal for the tropism of M. galilaea for islands. Instead, we postulate a tentative model of evolution in which the paleotropical origins of the species may be responsible for the release of strict seasonality constraints inherited early during the genus’ evolutionary history.

A transect in the German limestone Alps was monitored over ten years for nivicolous myxomycetes to test if species display stable altitudinal belts for fruiting. The data set comprised 1368 barcoded specimens assigned to 112 ribotypes forming 51 ribogroups. Ribogroups were largely consistent with 35 identified morphospecies, although in eleven cases a morphospecies included several ribogroups. Fructification abundance correlated with duration of the snow cover inferred from data loggers placed at ground height. Morphospecies, ribogroups, and ribotypes showed a peak of fructification abundance at different elevations in different years. Species composition, not abundances, showed a high overlap with soil metabarcoding data. Thirteen ribogroups detected in the metabarcoding data set were never found as fructifications. This survey demonstrates that nivicolous myxomycetes are opportunists, which are likely to persist as trophic or resting stages independent from snow cover, but fruit only in altitudes and years with snow cover stable over several months.

Although the anthropogenic decline in atmospheric carbon stable isotope ratios (δ¹³C) over the last 150 years (termed the Suess effect) is well-studied, how different terrestrial trophic levels and modes reflect this decline remains unresolved. To evaluate the Suess effect as an opportunistic tracer of terrestrial forest carbon cycling, this study analyzed the δ¹³C in herbarium specimens collected in Minnesota, USA from 1877 to 2019. Our results suggest that both broadleaf trees and ectomycorrhizal fungi relied on recent photosynthate to produce leaves and sporocarps, while saprotrophic fungi on average used carbon fixed from the atmosphere 32–55 years ago for sporocarp construction. The δ¹³C values of saprotrophic fungal collections were also sensitive to the age of their plant carbon substrate, with sporocarps of twig specialists tracking changes in atmospheric δ¹³C more closely than saprotrophs growing on logs. Collectively, this study indicates that natural history collections can quantitatively track carbon cycling among plants and fungi over time.

Mycelium-bound composites are normally made of discrete lignocellulosic substrate elements bound together by filamentous fungal hyphae. They can be formed into bespoke components of desired geometries by moulding or extrusion. Mycelium-bound composites with live fungi have been shown to be electrically conductive with memfractive and capacitive attributes. They can be integrated into electrical circuits with nonlinear electrical properties. Advancing fungal electronics, we studied the AC conductive properties of mycelium-bound composites and fungal fruit bodies at higher frequencies across three overlapping bands; 20 Hz to 300 kHz, 10 Hz to 4 MHz and 50 kHz to 3 GHz. Measurements indicate that mycelium-bound composites typically act as low-pass filters with a mean cut-off frequency of ∼500 kHz; with ∼−14 dB/decade roll-off, and mean attenuation across the pass band of $<$1 dB. Fruiting bodies have between one or two orders of magnitude lower mean cut-off frequency (5 kHz–50 kHz depending on species); with −20 dB/decade to −30 dB/decade roll-off, and mean attenuation across the pass band of $<$3 dB. The mechanism for the frequency-dependent attenuation is uncertain; however, the high water content, which is electrically conductive due to dissolved ionisable solids is probably a key factor. The potential for mycelium-bound composites and fruiting bodies in analog computing is explored.

Low temperatures near alpine treelines limit microbial release of soil nitrogen and tree growth. Ectomycorrhizal fungi can increase nitrogen supply for trees, but the importance of this exchange of carbon for nitrogen at the treeline remains unclear. Our bomb radiocarbon measurements indicated that trees transferred carbon fixed <2 years previously to fungi. The allocated carbon likely included sugars involved in starch synthesis, as δ¹³C in fungal caps closely resembled that of fine-root starch. Mass balance of nitrogen isotopes along the plant-fungi-soil continuum revealed that Larix decidua trees relied less on fungal nitrogen (0–35% of N uptake), compared to Pinus mugo trees (up to 41%). We estimated that treeline trees allocate up to 18% of photoassimilates to fungi. Our findings suggest that at alpine treelines, trees allocate to ectomycorrhizal symbionts relatively high amount of carbon compared to the reverse nitrogen flux, but the exact exchange is tree species-specific.

To identify the functional advantages of hyphal connections in fungal mycelial networks, we evaluated the wood decaying abilities of the mycelia of a saprotrophic basidiomycete, Phanerochaete velutina, in soil dishes with wood baits. The dishes were surrounded by water, allowing the mycelia to access water. Dishes with two or three baits were placed adjacent to or distant from each other, representing the ease of creating hyphal bridges between the two dishes. After 8 months of incubation, the weight loss of the wood bait was significantly larger in the adjacent pairs of dishes compared to the distant pairs. Mycelia in the adjacent dishes had higher chances to access the water and thus increase water content of the wood, which was the primary factor related to wood weight loss. These results suggest that hyphal connections increase decay ability of P. velutina possibly due to water transfer across the mycelial network.

The majority of studies exploring the ecology of saprotrophic fungi have worked with individual logs as homogenous sampling units, neglecting the presence of microhabitats and inner complexity. Based on close to 7000 sporocarp records of more than 450 fungal taxa from 134 decaying beech logs we investigated microhabitat preferences in macrofungi and linked these to sporocarp traits. The respective microhabitats were defined by the local wood decay stage, vertical position on the fallen log and special habitat features (hollows, fracture surfaces, woody material fallen from the log). We found microhabitat associations to be non-random in relation to fungal community composition and sporocarp morphology, indicating an evolutionary link between dead wood niche and sporocarp morphology. While log-level fungal species richness peaked at intermediate decay stages, taxa with significant indicator values were skewed towards early and late decay stages, when defined at microhabitat decay level. This suggests that the commonly found peak in fungal species richness on dead logs in intermediate decay stages expresses a peak in niche diversity rather than a peak in taxa decay stage preferences.

Free-living saprotrophic fungi and symbiotic mycorrhizal fungi affect organic matter dynamics differently because of contrasting ecological adaptations. We investigated how mass-loss, C:N-ratio and stable isotope dynamics of leaf litter and humus substrates depended on presence of living tree roots and associated fungal communities in a forest-to-tundra ecotone over three years. Litter mass-loss was stimulated by tree roots, contrary to a Gadgil effect. Increases in the litter nitrogen pool and δ¹⁵N suggested import of nitrogen from deeper soil by the dominating saprotrophic fungi. Over time, humus first lost, then gained, mass, and corresponding shifts in δ¹⁵N and δ¹³C suggested fluctuating pools of fine roots and fungal mycelium. Ectomycorrhizal tree roots consistently reduced longer-term humus mass-gain, counteracting positive effects of ericoid roots and associated fungi. Across all substrates, mass dynamics correlated with the balance between ectomycorrhizal and litter-saprotrophic fungi, both linked to mass-loss, and ericaceous shrubs and associated fungi, linked to mass-gain.

Wood-decay fungi are adapted to growth under different climate conditions and on various host tree species, but little is known about intraspecific variation in growth, substrate specificity and decay rates under different climatic conditions. Such knowledge is relevant to understand how wood-decay fungi will respond to climate change. Here, we investigate whether populations of the widespread brown-rot fungus Fomitopsis pinicola grow at different rates under different temperatures and water availabilities and whether the decay rate of the two wood substrates, Alnus incana and Picea abies, differs across populations. We isolated 72 cultures from fruit bodies collected in nine geographic localities across Norway, representing different climate conditions and substrates. We conducted in vitro growth experiments to assess the level of intraspecific phenotypic variability in temperature-dependent growth. All populations showed a strong but similar response in mycelial growth rates to different temperatures and water potentials. There were no consistent differences between populations in growth rates across temperatures, but larger variation between populations at the higher temperatures. Similarly, we observed no significant differences in wood decay rates across the nine populations and no signs of substrate specific adaptation to P. abies and A. incana. Our results indicate that local adaptation to different climates or substrates, as revealed by in vitro growth experiments, has to a limited extent, taken place during the few thousand years Fomitopsis pinicola has been present in this area.