Massive Peatland Carbon Banks Vulnerable to Rising Temperatures

Peatlands contain one-third of the world’s soil carbon (C). If destabilized, decomposition of this vast C bank could accelerate climate warming; however, the likelihood of this outcome remains unknown. Here, we examine peatland C stability through five years of whole-ecosystem warming and two years of elevated atmospheric carbon dioxide concentrations (eCO2). Warming exponentially increased methane (CH4) emissions and enhanced CH4 production rates throughout the entire soil profile; although surface CH4 production rates remain much greater than those at depth. Additionally, older deeper C sources played a larger role in decomposition following prolonged warming. Most troubling, decreases in CO2:CH4 ratios in gas production, porewater concentrations, and emissions, indicate that the peatland is becoming more methanogenic with warming. We observed limited evidence of eCO2 effects. Our results suggest that ecosystem responses are largely driven by surface peat, but that the vast C bank at depth in peatlands is responsive to prolonged warming

Paleogene Radiation of a Plant Pathogenic Mushroom

Background: The global movement and speciation of fungal plant pathogens is important, especially because of the economic losses they cause and the ease with which they are able to spread across large areas. Understanding the biogeography and origin of these plant pathogens can provide insights regarding their dispersal and current day distribution. We tested the hypothesis of a Gondwanan origin of the plant pathogenic mushroom genus Armillaria and the currently accepted premise that vicariance accounts for the extant distribution of the species. Methods: The phylogeny of a selection of Armillaria species was reconstructed based on Maximum Parsimony (MP), Maximum Likelihood (ML) and Bayesian Inference (BI). A timeline was then placed on the divergence of lineages using a Bayesian relaxed molecular clock approach. Results: Phylogenetic analyses of sequenced data for three combined nuclear regions provided strong support for three major geographically defined clades: Holarctic, South American-Australasian and African. Molecular dating placed the initial radiation of the genus at 54 million years ago within the Early Paleogene, postdating the tectonic break-up of Gondwana. Conclusions: The distribution of extant Armillaria species is the result of ancient long-distance dispersal rather than vicariance due to continental drift. As these finding are contrary to most prior vicariance hypotheses for fungi, our result

Weak habitat specificity in ectomycorrhizal communities associated with Salix herbacea and Salix polaris in alpine tundra

This study explores mid-alpine ectomycorrhizal communities on Salix herbacea and Salix polaris in plant communities differing in nutrient status and snow conditions. Plant species were identified by tracking roots back to above ground structures while fungal species were identified using molecular methods. The fungi were identified to 34 molecular operational taxonomic units (MOTUs)/species but species accumulation curves indicated that the communities were only partially sampled. The estimated total species richness was 49 (±9 SD) MOTUs/species. No significant ectomycorrhizal community specificity was found between the two plant species and only weak specificity between different plant communities. Furthermore, no difference in proportion of colonized root tips could be demonstrated between plant communities. However, some fungal taxa showed tendencies to associate with specific environmental conditions. Sebacinaceae, Inocybe egenula, Russula cf. emetica, and a Tomentella sp. were found in meadow communities but not in the heath communities. Sistotrema cf. alboluteum and Tomentella cf. terrestris were only found in the dry and mesic heath communities. Classifications into exploration types showed that the contact type is more abundant in the dry heath community than the other communities. Cenococcum geophilum was the most common species but Cortinarius spp., Russula spp., Tomentella spp., and Lactarius spp. were also common. This study confirms that alpine communities are rich in ectomycorrhizal fungi including species from a wide variety of fungal lineages and also show that many dominant species have wide ecological amplitude.</p