Suchergebnisse

Drying soil samples before DNA extraction is commonly used for specific fungal DNA quantification and metabarcoding studies, but the impact of different drying procedures on both the specific fungal DNA quantity and the fungal community composition has not been analyzed. We tested three different drying procedures (freeze-drying, oven-drying, and room temperature) on 12 different soil samples to determine (a) the soil mycelium biomass of the ectomycorrhizal species Lactarius vinosus using qPCR with a specifically designed TaqMan® probe and (b) the fungal community composition and diversity using the PacBio® RS II sequencing platform. Mycelium biomass of L. vinosus was significantly greater in the freeze-dried soil samples than in samples dried at oven and room temperature. However, drying procedures had no effect on fungal community composition or on fungal diversity. In addition, there were no significant differences in the proportions of fungi according to their functional roles (moulds vs. mycorrhizal species) in response to drying procedures. Only six out of 1139 operational taxonomic units (OTUs) had increased their relative proportions after soil drying at room temperature, with five of these OTUs classified as mould or yeast species. However, the magnitude of these changes was small, with an overall increase in relative abundance of these OTUs of approximately 2 %. These results suggest that DNA degradation may occur especially after drying soil samples at room temperature, but affecting equally nearly all fungi and therefore causing no significant differences in diversity and community composition. Despite the minimal effects caused by the drying procedures at the fungal community composition, freeze-drying resulted in higher concentrations of L. vinosus DNA and prevented potential colonization from opportunistic species. ; This work was supported by a STSM Grant from COST Action FP1203 and by the Spanish Ministry of Economy and Competitivity (MINECO) through the project AGL 2012-40035-C03. Carles Castaño received support from the Secretaria d'Universitats i Recerca del Departament d'Economia i Coneixement de la Generalitat de Catalunya through the program of Doctorats Industrials, funded by the European Union and the European Social Fund. Josu G. Alday was supported by Juan de la Cierva fellowships (IJCI-2014-21393).

Soil microclimate is a potentially important regulator of the composition of plant‐associated fungal communities in climates with significant drought periods. Here, we investigated the spatio‐temporal dynamics of soil fungal communities in a Mediterranean Pinus pinaster forest in relation to soil moisture and temperature. Fungal communities in 336 soil samples collected monthly over 1 year from 28 long‐term experimental plots were assessed by PacBio sequencing of ITS2 amplicons. Total fungal biomass was estimated by analysing ergosterol. Community changes were analysed in the context of functional traits. Soil fungal biomass was lowest during summer and late winter and highest during autumn, concurrent with a greater relative abundance of mycorrhizal species. Intra‐annual spatio‐temporal changes in community composition correlated significantly with soil moisture and temperature. Mycorrhizal fungi were less affected by summer drought than free‐living fungi. In particular, mycorrhizal species of the short‐distance exploration type increased in relative abundance under dry conditions, whereas species of the long‐distance exploration type were more abundant under wetter conditions. Our observations demonstrate a potential for compositional and functional shifts in fungal communities in response to changing climatic conditions. Free‐living fungi and mycorrhizal species with extensive mycelia may be negatively affected by increasing drought periods in Mediterranean forest ecosystems. ; This work was supported by the Spanish Ministry of Economy and Competitivity (MINECO) (grant number AGL2015‐66001‐C3). C.C. received support from the Secretaria d'Universitats i Recerca del Departament d'Economia i Coneixement de la Generalitat de Catalunya through the program of Doctorats Industrials, funded by the European Union and the European Social Fund. J.G.A. was supported by Juan de la Cierva (Grant number IJCI‐2014‐21393) and Ramon y Cajal fellowships (RYC‐2016‐20528) and J.A.B. benefits from the Serra‐Hunter Fellowship.

Predicted changes in global climate might negatively affect the soil microbiome and associated ecosystem processes in Mediterranean forests. Forest treatments, such as forest thinning, have been suggested to mitigate climate change impacts on vegetation by reducing competition between trees, thus increasing water availability. Studies addressing the combined effects of climate and forest thinning on belowground fungal communities are still scarce, being fundamental to elaborate adaptive strategies to global warming. The aim of this study was to evaluate the tree density reduction effects on soil fungal communities and their response to inter-annual changes in weather conditions. The temporal dynamics of soil fungal communities in relation to these two drivers (i.e., forest management and weather conditions) were studied from 2009 until 2014 in a set of 12 pairs of thinned and un-thinned plots dominated by Pinus pinaster Ait. Thinning (from 30% up to 70% reduction in stand basal area) was conducted in 2009 and soil fungal community composition was studied during 4 years. Here, we used autumn precipitation and temperature to describe the impact of inter-annual weather changes. We used Pacific Biosciences sequencing of fungal ITS2 amplicons to study fungal communities in soil samples. Forest thinning did not significantly affect fungal community composition nor fungal species richness and diversity, indicating that the soil fungal community is resistant to forest thinning regardless of its intensity. However, fungal species composition changed progressively across years, both at the species level and with regards to functional guilds. These changes in community composition were partly driven by inter-annual variation in precipitation and temperature, with free-living fungi increasing in abundance under wetter conditions, and symbiotic fungi being more prominent under drier and colder conditions. The results indicate that mycorrhizal communities in Mediterranean forest ecosystems can resist forest thinning, if enough trees and functional roots from thinned trees are retained. ; This work was supported by the Spanish Ministry of Economy and Competitivity (MINECO) [grant number AGL2015-66001-C3] and by the Collaborative European project ERANET-INFORMED (PCIN-2014-050). Carles Castaño received the support of the Doctorats Industrials program, funded by the European Union and the European Social Fund. Sergio de-Miguel was supported by the European Union's Horizon 2020 MultiFUNGtionality Marie Skłodowska-Curie [Grant number IF-EF No-655815]. Josu G. Alday was supported by Ramon y Cajal fellowship [Grant number RYC-2016-20528] and José Antonio Bonet benefited from a Serra-Húnter Fellowship provided by the Generalitat of Catalunya. The authors are very grateful to the PNIN of Poblet for its considerable help with the process of installing and maintaining the experimental plots. We thank Liu Bing, Daniel Oliach, Francesc Bolaño, Jordi Margalef, Josep Miró and Jewel Yurkewich for their assistance with sampling the plots and processing the samples. The constructive comments and suggestions of two anonymous reviewers were improved substantially this manuscript.