Digital Commons Network^™

Nitrogen Fertilization Has A Stronger Effect On Soil Nitrogen-Fixing Bacterial Communities Than Elevated Atmospheric Co2, Sean T. Berthrong, Chris M. Yeager, Laverne Gallegos-Graves, Blaire Steven, Stephanie A. Eichorst, Robert B. Jackson, Cheryl R. Kuske

Scholarship and Professional Work - LAS

Biological nitrogen fixation is the primary supply of N to most ecosystems, yet there is considerable uncertainty about how N-fixing bacteria will respond to global change factors such as increasing atmospheric CO₂ and N deposition. Using the nifH gene as a molecular marker, we studied how the community structure of N-fixing soil bacteria from temperate pine, aspen, and sweet gum stands and a brackish tidal marsh responded to multiyear elevated CO₂ conditions. We also examined how N availability, specifically, N fertilization, interacted with elevated CO₂ to affect these communities in the temperate pine forest. Based on data …

Agricultural Management And Labile Carbon Additions Affect Soil Microbial Community Structure And Interact With Carbon And Nitrogen Cycling, Sean T. Berthrong, Daniel H. Buckely, Laurie E. Drinkwater

Scholarship and Professional Work - LAS

We investigated how conversion from conventional agriculture to organic management affected the structure and biogeochemical function of soil microbial communities. We hypothesized the following. (1) Changing agricultural management practices will alter soil microbial community structure driven by increasing microbial diversity in organic management. (2) Organically managed soil microbial communities will mineralize more N and will also mineralize more N in response to substrate addition than conventionally managed soil communities. (3) Microbial communities under organic management will be more efficient and respire less added C. Soils from organically and conventionally managed agroecosystems were incubated with and without glucose (¹³C) …

Afforestation Alters The Composition Of Functional Genes In Soil And Biogeochemical Processes In South American Grasslands, Sean T. Berthrong, Christopher W. Schadt, Gervasio Piñeiro, Robert B. Jackson

Scholarship and Professional Work - LAS

Soil microbes are highly diverse and control most soil biogeochemical reactions. We examined how microbial functional genes and biogeochemical pools responded to the altered chemical inputs accompanying land use change. We examined paired native grasslands and adjacent Eucalyptus plantations (previously grassland) in Uruguay, a region that lacked forests before European settlement. Along with measurements of soil carbon, nitrogen, and bacterial diversity, we analyzed functional genes using the GeoChip 2.0 microarray, which simultaneously quantified several thousand genes involved in soil carbon and nitrogen cycling. Plantations and grassland differed significantly in functional gene profiles, bacterial diversity, and biogeochemical pool sizes. Most grassland …

A Global Meta-Analysis Of Soil Exchangeable Cations, Ph, Carbon, And Nitrogen With Afforestation, Sean T. Berthrong, Esteban G. Jobbagy, Robert B. Jackson

Scholarship and Professional Work - LAS

Afforestation, the conversion of non-forested lands to forest plantations, can sequester atmospheric carbon dioxide, but the rapid growth and harvesting of biomass may deplete nutrients and degrade soils if managed improperly. The goal of this study is to evaluate how afforestation affects mineral soil quality, including pH, sodium, exchangeable cations, organic carbon, and nitrogen, and to examine the magnitude of these changes regionally where afforestation rates are high. We also examine potential mechanisms to reduce the impacts of afforestation on soils and to maintain long-term productivity.

Across diverse plantation types (153 sites) to a depth of 30 cm of mineral …

Environmental Controls On The Landscape-Scale Biogeography Of Stream Bacterial Communities, Noah Fierer, Jennifer L. Morse, Sean T. Berthrong, Emily S. Bernhardt, Robert B. Jackson

Scholarship and Professional Work - LAS

We determined the biogeographical distributions of stream bacteria and the biogeochemical factors that best explained heterogeneity for 23 locations within the Hubbard Brook watershed, a 3000-ha forested watershed in New Hampshire, USA. Our goal was to assess the factor, or set of factors, responsible for generating the biogeographical patterns exhibited by microorganisms at the landscape scale. We used DNA fingerprinting to characterize bacteria inhabiting fine benthic organic matter (FBOM) because of their important influence on stream nutrient dynamics. Across the watershed, streams of similar pH had similar FBOM bacterial communities. Streamwater pH was the single variable most strongly correlated with …

The Uptake Of Amino Acids By Microbes And Trees In Three Cold-Temperate Forests, Adrien C. Finzi, Sean T. Berthrong

Scholarship and Professional Work - LAS

Amino acids are emerging as a critical component of the terrestrial N cycle, yet there is little understanding of amino acid cycling in temperate forests. This research studied the uptake and turnover of amino acid N by soil microbes and the capacity of forest trees to take up the amino acid glycine in comparison to NH₄⁺ and NO₃⁻. This research was conducted in three temperate forests located in northwest Connecticut, USA. The three forests differed in soil parent material and canopy tree species composition. At all three sites, amino acids were released from soil organic …