Jessica Ernakovich, Assistant Professor in Natural Resources and the Environment (COLSA) travel to Sweden

Professor Ernakovich joined UNH Professor Ruth Varner\u27s summer field campaign to Abisko, Sweden to study climate change on the landscape

Pesticide seed treatments containing neonicotinoids have limited effect on soil microbial community structure under different tillage regimes

Pesticide seed treatments (PST) which contain fungicides and insecticides are commonly used in agriculture; however, little is known about their effect on soil microbial communities and soil health. Neonicotinoids – controversial insecticides which are common in PST – have received criticism due to potential non-target effects. While fungal pathogens need to be moderated, PST have the potential to disturb broader fungal communities which could lead to reduced nutrient cycling and poor soil health. Given the broad use of PST, their effect on soil fungi needs to be studied within the context of other agricultural management practices. For example, tillage regimes can result in distinct fungal communities which may respond differently to PST. An experimental site was established in 2013 with a corn-soy rotation under three tillage treatments: Full-till, Strip-till, and No-till. Since 2016, seeds with or without PST (fungicides and insecticides) were planted under each tillage regime in a fully factorial design. In 2018, bulk soil was collected from within rows while soy was growing. A range of soil physicochemical variables were measured, and soil function was determined with substrate-induced respiration and enzyme assays. DNA was extracted from soil and the ITS region was sequenced to determine fungal community structure and diversity. While tillage significantly affected fungal community structure (p \u3c 0.01), there was no effect of PST on either community structure (p = 0.59) or diversity (p = 0.52). This indicates that PST does not affect bulk soil fungal communities; however, they may have an impact at different temporal or spatial scales than those studied here. Across all treatments, fungal community structure correlated with soil water holding capacity (rs = 0.23, p = 0.04) and electrical conductivity (rs = 0.26, p = 0.01). Despite not finding an effect of PST on fungal communities, we did find that PST increased potentially mineralizable nitrogen under no-till and shifted community level physiological profiles determined by substrate-induced respiration. These results suggest that while PST can affect certain aspects of soil health, there are no clear effects on the soil fungal community

Soil microbial communities vary in composition and functional strategy across soil aggregate size class regardless of tillage

The physicochemical environment within aggregates controls the distribution of carbon and microbial communities in soils. Agricultural management, such as tillage, can disrupt aggregates and the microscale habitat provided to microorganisms, thus altering microbial community dynamics. Categorizing microbial communities into life history strategies with shared functional traits—as has been done to understand plant community structure for decades—can illuminate how the soil physicochemical environment constrains the membership and activity of microbial communities. We conducted an aggregate scale survey of microbial community composition and function through the lens of the yield–acquisition–stress (Y–A–S) tolerator life history framework. Soils collected from a 7-year tillage experiment were separated into 4 aggregate size classes and enzyme activity, multiple-substrate-induced respiration, and carbon use efficiency were measured to reveal trade-offs in microbial resource allocation. Microbial community structure was interrogated with bacterial and fungal marker gene sequencing, and metagenomic features such as community weighted genome size and traits conferring stress tolerance were predicted using PICRUSt2. Consistent with our hypothesis, aggregates of different size classes harbored distinct microbial communities manifesting distinct life history strategies. Large macroaggregate communities \u3e2 mm were classified as acquisition strategists based on increased enzyme activity relative to other aggregate size classes. Small and medium microaggregate (0.25–2 mm) communities did not show a strong tendency toward any particular life history strategy. Genes conferring stress tolerance were significantly enriched in microaggregates \u3c0.25 mm (indicative of stress tolerators); however, these communities also had the highest carbon use efficiency (indicative of yield strategists). We found trade-offs in resource allocation between communities classified as yield and acquisition strategists consistent with the Y–A–S framework. Tillage did not alter life history strategies within aggregates, suggesting that the aggregate physicochemistry plays a larger role than agricultural management in shaping microbial life history at the scale studied

Dominance of Diffusive Methane Emissions From Lowland Headwater Streams Promotes Oxidation and Isotopic Enrichment

Inland waters are the largest natural source of methane (CH4) to the atmosphere, yet the contribution from small streams to this flux is not clearly defined. To fully understand CH4 emissions from streams and rivers, we must consider the relative importance of CH4 emission pathways, the prominence of microbially-mediated production and oxidation of CH4, and the isotopic signature of emitted CH4. Here, we construct a complete CH4 emission budgets for four lowland headwater streams by quantifying diffusive CH4 emissions and comparing them to previously published rates of ebullitive emissions. We also examine the isotopic composition of CH4 along with the sediment microbial community to investigate production and oxidation across the streams. We find that all four streams are supersaturated with respect to CH4 with diffusive emissions accounting for approximately 78–100% of total CH4 emissions. Isotopic and microbial data suggest CH4 oxidation is prevalent across the streams, depleting approximately half of the dissolved CH4 pool before emission. We propose a conceptual model of CH4 production, oxidation, and emission from small streams, where the dominance of diffusive emissions is greater compared to other aquatic ecosystems, and the impact of CH4 oxidation is observable in the emitted isotopic values. As a result, we suggest the CH4 emitted from small streams is isotopically heavy compared to lentic ecosystems. Our results further demonstrate streams are important components of the global CH4 cycle yet may be characterized by a unique pattern of cycling and emission that differentiate them from other aquatic ecosystems

Microtopography Matters: Belowground CH4 Cycling Regulated by Differing Microbial Processes in Peatland Hummocks and Lawns

Water table depth and vegetation are key controls of methane (CH4) emissions from peatlands. Microtopography integrates these factors into features called microforms. Microforms often differ in CH4 emissions, but microform-dependent patterns of belowground CH4 cycling remain less clearly resolved. To investigate the impact of microtopography on belowground CH4 cycling, we characterized depth profiles of the community composition and activity of CH4-cycling microbes using 16S rRNA amplicon sequencing, incubations, and measurements of porewater CH4 concentration and isotopic composition from hummocks and lawns at Sallie\u27s Fen in NH, USA. Geochemical proxies of methanogenesis and methanotrophy indicated that microforms differ in dominant microbial CH4 cycling processes. Hummocks, where water table depth is lower, had higher porewater redox potential (Eh) and higher porewater δ13C-CH4 values in the upper 30 cm than lawns, where water table depth is closer to the peat surface. Porewater δ13C-CH4 and δD-CH3D values were highest at the surface of hummocks where the ratio of methanotrophs to methanogens was also greatest. These results suggest that belowground CH4 cycling in hummocks is more strongly regulated by methanotrophy, while in lawns methanogenesis is more dominant. We also investigated controls of porewater CH4 chemistry. The ratio of the relative abundance of methanotrophs to methanogens was the strongest predictor of porewater CH4 concentration and δ13C-CH4, while vegetation composition had minimal influence. As microbial community composition was strongly influenced by redox conditions but not vegetation, we conclude that water table depth is a stronger control of belowground CH4 cycling across microforms than vegetation

The emergence of convergence

Science is increasingly a collaborative pursuit. Although the modern scientific enterprise owes much to individuals working at the core of their field, humanity is increasingly confronted by highly complex problems that require the integration of a variety of disciplinary and methodological expertise. In 2016, the U.S. National Science Foundation launched an initiative prioritizing support for convergence research as a means of “solving vexing research problems, in particular, complex problems focusing on societal needs.” We discuss our understanding of the objectives of convergence research and describe in detail the conditions and processes likely to generate successful convergence research. We use our recent experience as participants in a convergence workshop series focused on resilience in the Arctic to highlight key points. The emergence of resilience science over the past 50 years is presented as a successful contemporary example of the emergence of convergence. We close by describing some of the challenges to the development of convergence research, such as timescales and discounting the future, appropriate metrics of success, allocation issues, and funding agency requirements

The emergence of convergence

Science is increasingly a collaborative pursuit. Although the modern scientific enterprise owes much to individuals working at the core of their field, humanity is increasingly confronted by highly complex problems that require the integration of a variety of disciplinary and methodological expertise. In 2016, the U.S. National Science Foundation launched an initiative prioritizing support for convergence research as a means of “solving vexing research problems, in particular, complex problems focusing on societal needs.” We discuss our understanding of the objectives of convergence research and describe in detail the conditions and processes likely to generate successful convergence research. We use our recent experience as participants in a convergence workshop series focused on resilience in the Arctic to highlight key points. The emergence of resilience science over the past 50 years is presented as a successful contemporary example of the emergence of convergence. We close by describing some of the challenges to the development of convergence research, such as timescales and discounting the future, appropriate metrics of success, allocation issues, and funding agency requirements

What is Microbial Dormancy?

Life can be stressful. One way to deal with stress is to simply wait it out. Microbes do this by entering a state of reduced activity and increased resistance commonly called ‘dormancy’. But what is dormancy? Different scientific disciplines emphasize distinct traits and phenotypic ranges in defining dormancy for their microbial species and system-specific questions of interest. Here, we propose a unified definition of microbial dormancy, using a broad framework to place earlier discipline-specific definitions in a new context. We then discuss how this new definition and framework may improve our ability to investigate dormancy using multi-omics tools. Finally, we leverage our framework to discuss the diversity of genomic mechanisms for dormancy in an extreme environment that challenges easy definitions – the permafrost

Decomposability of soil organic matter over time: the Soil Incubation Database (SIDb, version 1.0) and guidance for incubation procedures

The magnitude of carbon (C) loss to the atmosphere via microbial decomposition is a function of the amount of C stored in soils, the quality of the organic matter, and physical, chemical, and biological factors that comprise the environment for decomposition. The decomposability of C is commonly assessed by laboratory soil incubation studies that measure greenhouse gases mineralized from soils under controlled conditions. Here, we introduce the Soil Incubation Database (SIDb) version 1.0, a compilation of time series data from incubations, structured into a new, publicly available, open-access database of C flux (carbon dioxide, CO2, or methane, CH4). In addition, the SIDb project also provides a platform for the development of tools for reading and analysis of incubation data as well as documentation for future use and development. In addition to introducing SIDb, we provide reporting guidance for database entry and the required variables that incubation studies need at minimum to be included in SIDb. A key application of this synthesis effort is to better characterize soil C processes in Earth system models, which will in turn reduce our uncertainty in predicting the response of soil C decomposition to a changing climate. We demonstrate a framework to fit curves to a number of incubation studies from diverse ecosystems, depths, and organic matter content using a built-in model development module that integrates SIDb with the existing SoilR package to estimate soil C pools from time series data. The database will help bridge the gap between point location measurements, which are commonly used in incubation studies, and global remote-sensed data or data products derived from models aimed at assessing global-scale rates of decomposition and C turnover. The SIDb version 1.0 is archived and publicly available at https://doi.org/10.5281/zenodo.3871263 (Sierra et al., 2020), and the database is managed under a version-controlled system and centrally stored in GitHub (https://github.com/SoilBGC-Datashare/sidb, last access: 26 June 2020)