Observations of an ash lagoon spill on the new River,Virginia

An estimated 7 million liters of slightly alkaline water (pH = 7.7) and ash entered New River on 23 July 1973 near Pearisburg, Virginia. The rate of dispersion, 1.4 km/hr, allowed qualitative collections of fishes and macroinvertebrates to be made immediately before and after the biological impact of the spill. Diversity and relative abundance indicated that fishes and macroinvertebrates were little affected. Physicochemical parameters from the flyash lagoon, as projected from 1971–1972 data, were within the known tolerance ranges of aquatic biota common to New River.     

Defining the twig fungal communities of Fraxinus species and Fraxinus excelsior genotypes with differences in susceptibility to ash dieback

Ash dieback disease (caused by Hymenoscyphus fraxineus) has affected European ash species (Fraxinus spp.) in recent decades. However, some Asian and American species of Fraxinus and certain genotypes of Fraxinus excelsior are less affected by the disease. We used ITS1-metabacoding to explore the drivers influencing diversity and composition of the twig fungal communities of Fraxinus species and F. excelsior genotypes. Our results revealed that fungi in the classes Eurotiomycetes and Dothideomycetes were among the most prevalent taxa in both Fraxinus species and F. excelsior genotypes. The diversity of the fungal communities differed significantly among Fraxinus species and could be explained by seed origin. Neither host genotype nor season had a significant effect on the community diversity of F. excelsior genotypes. On the other hand, the composition of twig fungal communities differed significantly among host species and among F. excelsior genotypes, and in F. excelsior there was also a significant effect of season on the composition of the fungal community. We did not find a clear effect of ash dieback susceptibility on either diversity or composition of fungal communities in twigs of Fraxinus species, although the effect was significant on the composition of fungal communities among F. excelsior genotypes. Our results demonstrated differences in fungal communities among species of Fraxinus and of F. excelsior genotypes, suggesting specific relationship between individual host genotypes and endophytic fungi.     

Effects of available P and N:P ratios on non-symbiotic dinitrogen fixation in tallgrass prairie soils

Summary Prescribed burning is a major control over element cycles in Tallgrass prairie (Eastern Kansas, USA). In this paper we report potential effects of fire on nonsymbiotic nitrogen fixation. Fire resulted in additions of available P in ash, which may stimulate nitrogen fixation by terrestrial cyanobacteria. Cyanobacterial nitrogenase activity and biomass responded positively to additions of ash or P in laboratory assays using soil. Further assays in soil showed that cyanobacteria responded to changes in available N:available P ratio (aN:P) across a range of concentrations. Nitrogen fixation rate could be related empirically to aN:P via a log-linear relationship. Extrapolation of laboratory results to the field yielded a maximal estimate of 21 kg N ha^-1 y^-1. Results support arguments from the marine and terrestrial literature that P availability is central to regulation of ecosystem N budgets.