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Wildfire affects our planet's biogeochemistry both by burning biomass and by driving changes in ecological communities and landcover. Some plants and ecosystem types are threatened by increasing fire pressure while others respond positively to fire, growing in local and regional abundance when it occurs regularly. However, quantifying total ecosystem response to fire demands consideration of impacts not only on aboveground vegetation, but also on soil microbes like fungi, which influence decomposition and nutrient mineralization. If fire‐resistant soil fungal communities co‐occur with similarly adapted plants, these above‐ and belowground ecosystem components should shift and recover in relative synchrony after burning. If not, fire might decouple ecosystem processes governed by these different communities, affecting total functioning. Here, we use a natural experiment to test whether fire‐dependent ecosystems host unique, fire‐resistant fungal communities. We surveyed burned and unburned areas across two California ecosystem types with differing fire ecologies in the immediate aftermath of a wildfire, finding that the soil fungal communities of fire‐dependent oak woodlands differ from those of neighbouring mixed evergreen forests. We discovered furthermore that the latter are more strongly altered compositionally by fire than the former, suggesting that differences in fungal community structure support divergent community responses to fire across ecosystems. Our results thus indicate that fire‐dependent ecosystems may host fire‐resistant fungal communities. [ABSTRACT FROM AUTHOR]

Soil microbial communities regulate and respond to key biogeochemical cycles and influence plant community patterns. However, microbial communities also respond to disturbance events, motivating an assessment of the relative roles of decadal multi‐factor global change, disturbance and plant community structure on microbial community responses.We used high‐throughput amplicon sequencing to characterize the diversity and composition of bacterial and fungal communities in bulk soil (0–7 cm) collected in 2014 from the Jasper Ridge Global Change Experiment, a full‐factorial field experiment in which ambient and elevated levels of nitrogen deposition (+7 g N m−2 yr−1 calcium nitrate), CO2 concentration (+275 ppm), temperature (+1–2°C) and precipitation (+50% volume with +3 weeks duration) were applied to a California annual grassland from 1998 to 2014. We used linear mixed‐effects modelling to test for the effects of global change on microbial diversity (observed richness, Shannon index). We also used generalized dissimilarity modelling (GDM) to study controls on compositional dissimilarity in fungal and bacterial communities.Bacterial community composition was best explained by exposure to fires in 2003 and 2011, whereas fungal community composition was best explained by plant community composition. The richness of fungi increased under elevated nitrogen deposition; bacterial diversity metrics decreased under warmer temperatures. Interactions between global change factors were statistically insignificant or weak.Synthesis. Our results indicate that even on decadal time‐scales, the effects of fire history and plant community composition on bacterial and fungal community composition, respectively, outweigh the effects of multi‐factor global change. Furthermore, global change factors have mostly additive effects on microbial diversity patterns. Our results show that highly variable mediators such as fire history and plant community composition limit the generalizability of soil microbial responses to long‐term global change. [ABSTRACT FROM AUTHOR]

Abstract: Interactions with symbiotic microbes, such as mycorrhizal fungi, have the potential to greatly influence plant growth, but it is unclear whether field variation in symbiont availability is common and, if so, sufficient to influence interspecific plant competition. In a greenhouse experiment using natural field soils, I varied the timing of ectomycorrhizal inoculation and the presence of an arbuscular mycorrhizal plant competitor, and measured their effects on pine seedling growth. I found that ectomycorrhizal colonization was absent in some field soils, and that in soils without mycorrhizal inoculum, delayed arrival of ectomycorrhizal spores progressively reduced pine seedling growth and favoured growth of the competitor. Competition had significant negative effects on pine seedling growth, but the competition effect was much smaller than the effect of delayed mutualist arrival. Synthesis. The importance of mycorrhizal spore arrival time on pine growth suggests that plants may experience mutualist limitation more frequently than previously expected, and the relative magnitude of seedling responses to mycorrhizal fungi and competing plants show that in some systems mutualism is likely of equal or greater importance compared with interspecific competition in affecting plant community assembly. [ABSTRACT FROM AUTHOR]

Recent advancements in sequencing technology allowed researchers to better address the patterns and mechanisms involved in microbial environmental adaptation at large spatial scales. Here we investigated the genomic basis of adaptation to climate at the continental scale in Suillus brevipes, an ectomycorrhizal fungus symbiotically associated with the roots of pine trees. We used genomic data from 55 individuals in seven locations across North America to perform genome scans to detect signatures of positive selection and assess whether temperature and precipitation were associated with genetic differentiation. We found that S. brevipes exhibited overall strong population differentiation, with potential admixture in Canadian populations. This species also displayed genomic signatures of positive selection as well as genomic sites significantly associated with distinct climatic regimes and abiotic environmental parameters. These genomic regions included genes involved in transmembrane transport of substances and helicase activity potentially involved in cold stress response. Our study sheds light on large-scale environmental adaptation in fungi by identifying putative adaptive genes and providing a framework to further investigate the genetic basis of fungal adaptation. [ABSTRACT FROM AUTHOR]

The supply of nitrogen (N) constrains primary productivity in many ecosystems, raising the question 'what controls the availability and cycling of N'? As a step toward answering this question, we evaluated N cycling processes and aspects of their regulation on a climate gradient on Kohala Volcano, Hawaii, USA. The gradient extends from sites receiving <300 mm/yr of rain to those receiving >3,000 mm/yr, and the pedology and dynamics of rock-derived nutrients in soils on the gradient are well understood. In particular, there is a soil process domain at intermediate rainfall within which ongoing weathering and biological uplift have enriched total and available pools of rock-derived nutrients substantially; sites at higher rainfall than this domain are acid and infertile as a consequence of depletion of rock-derived nutrients, while sites at lower rainfall are unproductive and subject to wind erosion. We found elevated rates of potential net N mineralization in the domain where rock-derived nutrients are enriched. Higher-rainfall sites have low rates of potential net N mineralization and high rates of microbial N immobilization, despite relatively high rates of gross N mineralization. Lower-rainfall sites have moderately low potential net N mineralization, relatively low rates of gross N mineralization, and rates of microbial N immobilization sufficient to sequester almost all the mineral N produced. Bulk soil δ15N also varied along the gradient, from +4‰ at high rainfall sites to +14‰ at low rainfall sites, indicating differences in the sources and dynamics of soil N. Our analysis shows that there is a strong association between N cycling and soil process domains that are defined using soil characteristics independent of N along this gradient, and that short-term controls of N cycling can be understood in terms of the supply of and demand for N. [ABSTRACT FROM AUTHOR]

Nonpathogenic foliar fungi (i.e. endophytes and epiphytes) can modify plant disease severity in controlled experiments. However, experiments have not been combined with ecological studies in wild plant pathosystems to determine whether disease-modifying fungi are common enough to be ecologically important., We used culture-based methods and DNA sequencing to characterize the abundance and distribution of foliar fungi of Populus trichocarpa in wild populations across its native range (Pacific Northwest, USA). We conducted complementary, manipulative experiments to test how foliar fungi commonly isolated from those populations influence the severity of Melampsora leaf rust disease. Finally, we examined correlative relationships between the abundance of disease-modifying foliar fungi and disease severity in wild trees., A taxonomically and geographically diverse group of common foliar fungi significantly modified disease severity in experiments, either increasing or decreasing disease severity. Spatial patterns in the abundance of some of these foliar fungi were significantly correlated (in predicted directions) with disease severity in wild trees., Our study reveals that disease modification is an ecological function shared by common foliar fungal symbionts of P. trichocarpa. This finding raises new questions about plant disease ecology and plant biodiversity, and has applied potential for disease management. [ABSTRACT FROM AUTHOR]

A gasteroid bolete collected recently in Sarawak on the island of Borneo is described as the new species Spongiforma squarepantsii. A comprehensive description, illustrations, phylogenetic placement and a comparison with [...]