Decomposition is a crucial process in terrestrial ecosystems, driving nutrient cycling and carbon storage dynamics. Considering the amount of fungal necromass produced in soils annually, its decomposition represents an important nutrient recycling process. Understanding the decomposition dynamics and associated microbial communities of fungal necromass is essential for elucidating ecosystem functioning, especially in environmentally sensitive regions such as the Arctic tundra, which remain under-explored. In a three-year field experiment conducted in the Svalbard archipelago, we investigated the decomposition of two types of fungal necromass with differing biochemical properties. We studied the decomposition rate, changes in chemical composition, and the succession of fungal and bacterial communities associated with the decaying fungal necromass. We discovered that up to 20% of fungal necromass remained even after three years of decomposition, indicating that the decomposition process was incomplete. Our results indicate the crucial role of Pseudogymnoascus in decomposing low-quality, highly melanized necromass with a high C:N ratio in Arctic soils, underscoring its importance in carbon cycling in the Arctic tundra. Notably, we observed dynamic changes in bacterial communities, with increasing richness over time and a shift from copiotrophic to oligotrophic species specializing in decomposing recalcitrant material. Our study indicates the strong potential that fungal necromass can play in carbon sequestration of arctic soils and reveals the distinct dynamics between rather stable fungal and rapidly changing bacterial communities associated with the decomposing fungal necromass in the Arctic tundra. These findings enhance our understanding of microbial succession during decomposition in extreme environments and highlight the potentially differing roles of fungi and bacteria in these processes.

• Klíčová slova
• Arctic tundra, Bacterial communities, Decomposition, Fungal communities, Fungal necromass,
• Publikační typ
• časopisecké články MeSH

Fine woody debris (FWD) represents the majority of the deadwood stock in managed forests and serves as an important biodiversity hotspot and refuge for many organisms, including deadwood fungi. Wood decomposition in forests, representing an important input of nutrients into forest soils, is mainly driven by fungal communities that undergo continuous changes during deadwood decomposition. However, while the assembly processes of fungal communities in long-lasting coarse woody debris have been repeatedly explored, similar information for the more ephemeral habitat of fine deadwood is missing. Here, we followed the fate of FWD of Fagus sylvatica and Abies alba in a Central European forest to describe the assembly and diversity patterns of fungal communities over 6 years. Importantly, the effect of microclimate on deadwood properties and fungal communities was addressed by comparing FWD decomposition in closed forests and under open canopies because the large surface-to-volume ratio of FWD makes it highly sensitive to temperature and moisture fluctuations. Indeed, fungal biomass increases and pH decreases were significantly higher in FWD under closed canopy in the initial stages of decomposition indicating higher fungal activity and hence decay processes. The assembly patterns of the fungal community were strongly affected by both tree species and microclimatic conditions. The communities in the open/closed canopies and in each tree species were different throughout the whole succession with only limited convergence in time in terms of both species and ecological guild composition. Decomposition under the open canopy was characterized by high sample-to-sample variability, showing the diversification of fungal resources. Tree species-specific fungi were detected among the abundant species mostly during the initial decomposition, whereas fungi associated with certain canopy cover treatments were present evenly during decomposition. The species diversity of forest stands and the variability in microclimatic conditions both promote the diversity of fine woody debris fungi in a forest.

• Klíčová slova
• canopy cover, deadwood, decomposition, ecology, fungal community, microclimate, succession, temperate forest,
• Publikační typ
• časopisecké články MeSH

Deadwood represents an important carbon stock and contributes to climate change mitigation. Wood decomposition is mainly driven by fungal communities. Their composition is known to change during decomposition, but it is unclear how environmental factors such as wood chemistry affect these successional patterns through their effects on dominant fungal taxa. We analysed the deadwood of Fagus sylvatica and Abies alba across a deadwood succession series of >40 years in a natural fir-beech forest in the Czech Republic to describe the successional changes in fungal communities, fungal abundance and enzymatic activities and to link these changes to environmental variables. The fungal communities showed high levels of spatial variability and beta diversity. In young deadwood, fungal communities showed higher similarity among tree species, and fungi were generally less abundant, less diverse and less active than in older deadwood. pH and the carbon to nitrogen ratio (C/N) were the best predictors of the fungal community composition, and they affected the abundance of half of the dominant fungal taxa. The relative abundance of most of the dominant taxa tended to increase with increasing pH or C/N, possibly indicating that acidification and atmospheric N deposition may shift the community composition towards species that are currently less dominant.

• Klíčová slova
• deadwood, decomposition, extracellular enzymes, fungal community, fungal ecology, mixed natural forest, succession,
• Publikační typ
• časopisecké články MeSH