Search for: All records

The functioning of mycorrhizal symbioses is tied to soil nutrient status, suggesting that nutrient availability should influence the reproduction of mycorrhizal fungi. To quantify the effects of nitrogen (N) and phosphorus (P) availability on ectomycorrhizal fungal fruiting, we collected >4000 epigeous sporocarps representing 19 families during the course of a season in a full factorial NxP addition experiment in six replicate forest stands. Nutrient effects on fruiting shifted as the season progressed, with early fruiting species responding more to P and late-fruiting species responding more to N. The composition of species fruiting in young successional forests differed more with nutrient addition than in mature forests. Sporocarp abundance and species richness were suppressed by N addition. This work shows that N and P availability affect ectomycorrhizal fungal fruiting, with these effects taking place within a context defined by stand age and the progression of fruiting across the season. 

Abstract Northern peatlands are a globally significant source of methane (CH₄), and emissions are projected to increase due to warming and permafrost loss. Understanding the microbial mechanisms behind patterns in CH₄production in peatlands will be key to predicting annual emissions changes, with stable carbon isotopes (δ¹³C‐CH₄) being a powerful tool for characterizing these drivers. Given that δ¹³C‐CH₄is used in top‐down atmospheric inversion models to partition sources, our ability to model CH₄production pathways and associated δ¹³C‐CH₄values is critical. We sought to characterize the role of environmental conditions, including hydrologic and vegetation patterns associated with permafrost thaw, on δ¹³C‐CH₄values from high‐latitude peatlands. We measured porewater and emitted CH₄stable isotopes, pH, and vegetation composition from five boreal‐Arctic peatlands. Porewater δ¹³C‐CH₄was strongly associated with peatland type, with δ¹³C enriched values obtained from more minerotrophic fens (−61.2 ± 9.1‰) compared to permafrost‐free bogs (−74.1 ± 9.4‰) and raised permafrost bogs (−81.6 ± 11.5‰). Variation in porewater δ¹³C‐CH₄was best explained by sedge cover, CH₄concentration, and the interactive effect of peatland type and pH (r² = 0.50,p < 0.001). Emitted δ¹³C‐CH₄varied greatly but was positively correlated with porewater δ¹³C‐CH₄. We calculated a mixed atmospheric δ¹³C‐CH₄value for northern peatlands of −65.3 ± 7‰ and show that this value is more sensitive to landscape drying than wetting under permafrost thaw scenarios. Our results suggest northern peatland δ¹³C‐CH₄values are likely to shift in the future which has important implications for source partitioning in atmospheric inversion models. 

ABSTRACT Hydrologic shifts due to climate change will affect the cycling of carbon (C) stored in boreal peatlands. Carbon cycling in these systems is carried out by microorganisms and plants in close association. This study investigated the effects of experimentally manipulated water tables (lowered and raised) and plant functional groups on the peat and root microbiomes in a boreal rich fen. All samples were sequenced and processed for bacterial, archaeal (16S DNA genes; V4), and fungal (internal transcribed spacer 2 [ITS2]) DNA. Depth had a strong effect on microbial and fungal communities across all water table treatments. Bacterial and archaeal communities were most sensitive to the water table treatments, particularly at the 10- to 20-cm depth; this area coincides with the rhizosphere or rooting zone. Iron cyclers, particularly members of the family Geobacteraceae , were enriched around the roots of sedges, horsetails, and grasses. The fungal community was affected largely by plant functional group, especially cinquefoils. Fungal endophytes (particularly Acephala spp.) were enriched in sedge and grass roots, which may have underappreciated implications for organic matter breakdown and cycling. Fungal lignocellulose degraders were enriched in the lowered water table treatment. Our results were indicative of two main methanogen communities, a rooting zone community dominated by the archaeal family Methanobacteriaceae and a deep peat community dominated by the family Methanomicrobiaceae . IMPORTANCE This study demonstrated that roots and the rooting zone in boreal fens support organisms likely capable of methanogenesis, iron cycling, and fungal endophytic association and are directly or indirectly affecting carbon cycling in these ecosystems. These taxa, which react to changes in the water table and associate with roots and, particularly, graminoids, may gain greater biogeochemical influence, as projected higher precipitation rates could lead to an increased abundance of sedges and grasses in boreal fens. 

Summary Drainage‐induced encroachment by trees may have major effects on the carbon balance of northern peatlands, and responses of microbial communities are likely to play a central mechanistic role.We profiled the soil fungal community and estimated its genetic potential for the decay of lignin and phenolics (class II peroxidase potential) along peatland drainage gradients stretching from interior locations (undrained, open) to ditched locations (drained, forested).Mycorrhizal fungi dominated the community across the gradients. When moving towards ditches, the dominant type of mycorrhizal association abruptly shifted from ericoid mycorrhiza to ectomycorrhiza atc.120 m from the ditches. This distance corresponded with increased peat loss, from which more than half may be attributed to oxidation. The ectomycorrhizal genusCortinariusdominated at the drained end of the gradients and its relatively higher genetic potential to produce class II peroxidases (together withMycena) was positively associated with peat humification and negatively with carbon‐to‐nitrogen ratio.Our study is consistent with a plant–soil feedback mechanism, driven by a shift in the mycorrhizal type of vegetation, that potentially mediates changes in aerobic decomposition during postdrainage succession. Such feedback may have long‐term legacy effects upon postdrainage restoration efforts and implication for tree encroachment onto carbon‐rich soils globally. 

Peatlands account for 15 to 30% of the world’s soil carbon (C) stock and are important controls over global nitrogen (N) cycles. However, C and N concentrations are known to vary among peatlands contributing to the uncertainty of global C inventories, but there are few global studies that relate peatland classification to peat chemistry. We analyzed 436 peat cores sampled in 24 countries across six continents and measured C, N, and organic matter (OM) content at three depths down to 70 cm. Sites were distinguished between northern (387) and tropical (49) peatlands and assigned to one of six distinct broadly recognized peatland categories that vary primarily along a pH gradient. Peat C and N concentrations, OM content, and C:N ratios differed significantly among peatland categories, but few differences in chemistry with depth were found within each category. Across all peatlands C and N concentrations in the 10–20 cm layer, were 440 ± 85.1 g kg -1 and 13.9 ± 7.4 g kg -1 , with an average C:N ratio of 30.1 ± 20.8. Among peatland categories, median C concentrations were highest in bogs, poor fens and tropical swamps (446–532 g kg -1 ) and lowest in intermediate and extremely rich fens (375–414 g kg -1 ). The C:OM ratio in peat was similar across most peatland categories, except in deeper samples from ombrotrophic tropical peat swamps that were higher than other peatlands categories. Peat N concentrations and C:N ratios varied approximately two-fold among peatland categories and N concentrations tended to be higher (and C:N lower) in intermediate fens compared with other peatland types. This study reports on a unique data set and demonstrates that differences in peat C and OM concentrations among broadly classified peatland categories are predictable, which can aid future studies that use land cover assessments to refine global peatland C and N stocks. 

Abstract Fungi are highly diverse organisms, which provide multiple ecosystem services. However, compared with charismatic animals and plants, the distribution patterns and conservation needs of fungi have been little explored. Here, we examined endemicity patterns, global change vulnerability and conservation priority areas for functional groups of soil fungi based on six global surveys using a high‐resolution, long‐read metabarcoding approach. We found that the endemicity of all fungi and most functional groups peaks in tropical habitats, including Amazonia, Yucatan, West‐Central Africa, Sri Lanka, and New Caledonia, with a negligible island effect compared with plants and animals. We also found that fungi are predominantly vulnerable to drought, heat and land‐cover change, particularly in dry tropical regions with high human population density. Fungal conservation areas of highest priority include herbaceous wetlands, tropical forests, and woodlands. We stress that more attention should be focused on the conservation of fungi, especially root symbiotic arbuscular mycorrhizal and ectomycorrhizal fungi in tropical regions as well as unicellular early‐diverging groups and macrofungi in general. Given the low overlap between the endemicity of fungi and macroorganisms, but high conservation needs in both groups, detailed analyses on distribution and conservation requirements are warranted for other microorganisms and soil organisms.