Experimental Open Air Burning of Vegetation Enhances Organic Matter Chemical Heterogeneity Compared to Laboratory Burns.

Wildfires produce solid residuals that have unique chemical and physical properties compared to unburned materials, which influence their cycling and fate in the natural environment. Visual burn severity assessment is used to evaluate post-fire alterations to the landscape in field-based studies, yet muffle furnace methods are commonly used in laboratory studies to assess molecular scale alterations along a temperature continuum. Here, we examined solid and leachable organic matter characteristics from chars visually characterized as low burn severity that were created either on an open air burn table or from low-temperature muffle furnace burns. We assessed how the different combustion conditions influence solid and dissolved organic matter chemistries and explored the potential influence of these results on the environmental fate and reactivity. Notably, muffle furnace chars produced less leachable carbon and nitrogen than open air chars across land cover types. Organic matter produced from muffle furnace burns was more homogeneous than open air chars. This work highlights chemical heterogeneities that exist within a single burn severity category, potentially influencing our conceptual understanding of pyrogenic organic matter cycling in the natural environment, including transport and processing in watersheds. Therefore, we suggest that open air burn studies are needed to further advance our understanding of pyrogenic organic matter's environmental reactivity and fate.

Landscape Topography and Regional Drought Alters Dust Microbiomes in the Sierra Nevada of California.

Dust provides an ecologically significant input of nutrients, especially in slowly eroding ecosystems where chemical weathering intensity limits nutrient inputs from underlying bedrock. In addition to nutrient inputs, incoming dust is a vector for dispersing dust-associated microorganisms. While little is known about dust-microbial dispersal, dust deposits may have transformative effects on ecosystems far from where the dust was emitted. Using molecular analyses, we examined spatiotemporal variation in incoming dust microbiomes along an elevational gradient within the Sierra Nevada of California. We sampled throughout two dry seasons and found that dust microbiomes differed by elevation across two summer dry seasons (2014 and 2015), which corresponded to competing droughts in dust source areas. Dust microbial taxa richness decreased with elevation and was inversely proportional to dust heterogeneity. Likewise, dust phosphorus content increased with elevation. At lower elevations, early season dust microbiomes were more diverse than those found later in the year. The relative abundances of microbial groups shifted during the summer dry season. Furthermore, mutualistic fungal diversity increased with elevation, which may have corresponded with the biogeography of their plant hosts. Although dust fungal pathogen diversity was equivalent across elevations, elevation and sampling month interactions for the relative abundance, diversity, and richness of fungal pathogens suggest that these pathogens differed temporally across elevations, with potential implications for humans and wildlife. This study shows that landscape topography and droughts in source locations may alter the composition and diversity of ecologically relevant dust-associated microorganisms.

Depth dependence of climatic controls on soil microbial community activity and composition.

Subsoil microbiomes play important roles in soil carbon and nutrient cycling, yet our understanding of the controls on subsoil microbial communities is limited. Here, we investigated the direct (mean annual temperature and precipitation) and indirect (soil chemistry) effects of climate on microbiome composition and extracellular enzyme activity throughout the soil profile across two elevation-bioclimatic gradients in central California, USA. We found that microbiome composition changes and activity decreases with depth. Across these sites, the direct influence of climate on microbiome composition and activity was relatively lower at depth. Furthermore, we found that certain microbial taxa change in relative abundance over large temperature and precipitation gradients only in specific soil horizons, highlighting the depth dependence of the climatic controls on microbiome composition. Our finding that the direct impacts of climate are muted at depth suggests that deep soil microbiomes may lag in their acclimation to new temperatures with a changing climate.

Endophyte-Promoted Phosphorus Solubilization in Populus.

Phosphorus is one of the essential nutrients for plant growth, but it may be relatively unavailable to plants because of its chemistry. In soil, the majority of phosphorus is present in the form of a phosphate, usually as metal complexes making it bound to minerals or organic matter. Therefore, inorganic phosphate solubilization is an important process of plant growth promotion by plant associated bacteria and fungi. Non-nodulating plant species have been shown to thrive in low-nutrient environments, in some instances by relying on plant associated microorganisms called endophytes. These microorganisms live within the plant and help supply nutrients for the plant. Despite their potential enormous environmental importance, there are a limited number of studies looking at the direct molecular impact of phosphate solubilizing endophytic bacteria on the host plant. In this work, we studied the impact of two endophyte strains of wild poplar (Populus trichocarpa) that solubilize phosphate. Using a combination of x-ray imaging, spectroscopy methods, and proteomics, we report direct evidence of endophyte-promoted phosphorus uptake in poplar. We found that the solubilized phosphate may react and become insoluble once inside plant tissue, suggesting that endophytes may aid in the re-release of phosphate. Using synchrotron x-ray fluorescence spectromicroscopy, we visualized the nutrient phosphorus inside poplar roots inoculated by the selected endophytes and found the phosphorus in both forms of organic and inorganic phosphates inside the root. Tomography-based root imaging revealed a markedly different root biomass and root architecture for poplar samples inoculated with the phosphate solubilizing bacteria strains. Proteomics characterization on poplar roots coupled with protein network analysis revealed novel proteins and metabolic pathways with possible involvement in endophyte enriched phosphorus uptake. These findings suggest an important role of endophytes for phosphorus acquisition and provide a deeper understanding of the critical symbiotic associations between poplar and the endophytic bacteria.

Phosphorus Speciation in Atmospherically Deposited Particulate Matter and Implications for Terrestrial Ecosystem Productivity.

Chemical forms of phosphorus (P) in airborne particulate matter (PM) are poorly known and do not correlate with solubility or extraction measurements commonly used to infer speciation. We used P X-ray absorption near-edge structure (XANES) and 31P nuclear magnetic resonance (NMR) spectroscopies to determine P species in PM collected at four mountain sites (Colorado and California). Organic P species dominated samples from high elevations, with organic P estimated at 65-100% of total P in bulk samples by XANES and 79-88% in extracted fractions (62-84% of total P) by NMR regardless of particle size (≥10 or 1-10 µm). Phosphorus monoester and diester organic species were dominant and present in about equal proportions, with low fractions of inorganic P species. By comparison, PM from low elevation contained mixtures of organic and inorganic P, with organic P estimated at 30-60% of total P. Intercontinental PM transport determined from radiogenic lead (Pb) isotopes varied from 0 to 59% (mean 37%) Asian-sourced Pb at high elevation, whereas stronger regional PM inputs were found at low elevation. Airborne flux of bioavailable P to high-elevation ecosystems may be twice as high as estimated by global models, which will disproportionately affect net primary productivity.

An Evaluation of Provincial Infectious Disease Surveillance Reports in Ontario.

CONTEXT: Public Health Ontario (PHO) publishes various infectious disease surveillance reports, but none have yet been formally evaluated. OBJECTIVE: PHO evaluated its monthly and annual infectious disease surveillance reports to assess public health stakeholders' current perception of the products and to develop recommendations for improving future products. DESIGN: An evaluation consisting of an online survey and a review of public Web sites of other jurisdictions with similar annual reports. SETTING: For the online survey, stakeholder organizations targeted were the 36 local public health units and the Health health ministry in Ontario, Canada. PARTICIPANTS: Survey participants included epidemiologists, managers, directors, and other public health practitioners from participating organizations. MAIN OUTCOME MEASURES: Online survey respondents' awareness and access to the reports, their rated usefulness of reports and subsections, and suggestions for improving usefulness; timeliness of select annual reports from other jurisdictions based on the period from data described to report publication. RESULTS: Among 57 survey respondents, between 74% and 97% rated each report as useful; the most common use was for situational awareness. Respondents ranked timeliness as the most important attribute of surveillance reports, followed by data completeness. Among 6 annual reports reviewed, the median time to publication was 11.5 months compared with 23.2 months for PHO. CONCLUSION: Recommendations based on this evaluation have already been applied to the monthly report (eg, focusing on the most useful sections) and have become key considerations when developing future annual reports and other surveillance reporting tools (eg, need to provide more timely reports). Other public health organizations may also use this evaluation to inform aspects of their surveillance report development and evaluation. The evaluation results have provided PHO with direction on how to improve its provincial infectious disease surveillance reporting moving forward, and formed a basis for future work in surveillance product development and evaluation.

Temporal aspects of the visuotactile congruency effect.

We report an experiment designed to investigate the temporal dynamics of the visuotactile crossmodal congruency effect. Vibrotactile targets were presented randomly to the index finger (top side of a hand-held cube) or thumb (bottom side) of either hand while visual distractors were presented randomly from one of the same four possible locations. The stimulus onset asynchrony (SOA) between the vibrotactile target and the visual distractor was varied on a trial-by-trial basis. Participants made speeded discrimination responses regarding the elevation of the vibrotactile targets (i.e., upper versus lower) while trying to ignore the visual distractors. The largest crossmodal congruency effects (defined as the difference in performance between incongruent and congruent elevation distractor trials) were obtained when the visual distractor preceded the vibrotactile target by 50-100 ms, although significant effects were also reported when the distractor followed the target by as much as 100 ms. These results are discussed in terms of the conjoint influence of response competition, crossmodal perceptual interactions (i.e., the ventriloquism effect), and exogenous spatial attention on the crossmodal congruency effect. The distinct temporal signatures of each of these effects are also highlighted.