Digital Commons Network^™

Soil Respiration In A Northeastern Us Temperate Forest: A 22‐Year Synthesis, M. A. Giasson, A. M. Ellison, R. D. Bowden, Patrick M. Crill, Erik A. Davidson, J. E. Drake, Serita D. Frey, J. L. Hadley, M. Lavine, J. M. Melillo, J. W. Munger, K. J. Nadelhoffer, L. Nicoll, Scott V. Ollinger, K. E. Savage, P. A. Steudler, J. Tang, Ruth K. Varner, S. C. Wofsy, D. R. Foster, A. C. Finzi

Faculty Publications

To better understand how forest management, phenology, vegetation type, and actual and simulated climatic change affect seasonal and inter‐annual variations in soil respiration (Rs), we analyzed more than 100,000 individual measurements of soil respiration from 23 studies conducted over 22 years at the Harvard Forest in Petersham, Massachusetts, USA. We also used 24 site‐years of eddy‐covariance measurements from two Harvard Forest sites to examine the relationship between soil and ecosystem respiration (Re).

Rs was highly variable at all spatial (respiration collar to forest stand) and temporal (minutes to years) scales of measurement. The response of Rs to experimental manipulations mimicking …

Microbes In Nature Are Limited By Carbon And Energy: The Starving-Survival Lifestyle In Soil And Consequences For Estimating Microbial Rates, John E. Hobbie, Erik A. Hobbie

Faculty Publications

Understanding microbial transformations in soils is important for predicting future carbon sequestration and nutrient cycling. This review questions some methods of assessing one key microbial process, the uptake of labile organic compounds. First, soil microbes have a starving-survival life style of dormancy, arrested activity, and low activity. Yet they are very abundant and remain poised to completely take up all substrates that become available. As a result, dilution assays with the addition of labeled substrates cannot be used. When labeled substrates are transformed into 14CO2, the first part of the biphasic release follows metabolic rules and is not affected by …

A Source Of Terrestrial Organic Carbon To Investigate The Browning Of Aquatic Ecosystems, Jay T. Lennon, Stephen K. Hamilton, Mario E. Muscarella, A. Stuart Grandy, Kyle Wickings, Stuart E. Jones

Faculty Publications

There is growing evidence that terrestrial ecosystems are exporting more dissolved organic carbon (DOC) to aquatic ecosystems than they did just a few decades ago. This “browning” phenomenon will alter the chemistry, physics, and biology of inland water bodies in complex and difficult-to-predict ways. Experiments provide an opportunity to elucidate how browning will affect the stability and functioning of aquatic ecosystems. However, it is challenging to obtain sources of DOC that can be used for manipulations at ecologically relevant scales. In this study, we evaluated a commercially available source of humic substances (“Super Hume”) as an analog for natural sources …

Field And Lab Conditions Alter Microbial Enzyme And Biomass Dynamics Driving Decomposition Of The Same Leaf Litter, Zachary L. Rinkes, Robert L. Sinsabaugh, Daryl L. Moorhead, A. Stuart Grandy, Michael N. Weintraub

Faculty Publications

Fluctuations in climate and edaphic factors influence field decomposition rates and preclude a complete understanding of how microbial communities respond to plant litter quality. In contrast, laboratory microcosms isolate the intrinsic effects of litter chemistry and microbial community from extrinsic effects of environmental variation. Used together, these paired approaches provide mechanistic insights to decomposition processes. In order to elucidate the microbial mechanisms underlying how environmental conditions alter the trajectory of decay, we characterized microbial biomass, respiration, enzyme activities, and nutrient dynamics during early (<10% mass loss), mid- (10–40% mass loss), and late (>40% mass loss) decay in parallel field and laboratory litter bag incubations for deciduous tree litters …

Multiyear Measurements Of Ebullitive Methane Flux From Three Subarctic Lakes, Martin Wik, Ruth K. Varner, David Bastviken

Faculty Publications

Ebullition (bubbling) from small lakes and ponds at high latitudes is an important yet unconstrained source of atmospheric methane (CH4). Small water bodies are most abundant in permanently frozen peatlands, and it is speculated that their emissions will increase as the permafrost thaws. We made 6806 measurements of CH4 ebullition during four consecutive summers using a total of 40 bubble traps that were systematically distributed across the depth zones of three lakes in a sporadic permafrost landscape in northernmost Sweden. We identified significant spatial and temporal variations in ebullition and observed a large spread in the bubbles' CH4 concentration, ranging …

Methane Adsorption On Aggregates Of Fullerenes: Site-Selective Storage Capacities And Adsorption Energies, Alexander Kaiser, Samuel Zottl, Peter Bartl, Christian Leidlmair, Andreas Mauracher, Michael Probst, Stephan Denifl, Olof Echt, Paul Scheier

Faculty Publications

Methane adsorption on positively charged aggregates of C60 is investigated by both mass spectrometry and computer simulations. Calculated adsorption energies of 118–281 meV are in the optimal range for high‐density storage of natural gas. Groove sites, dimple sites, and the first complete adsorption shells are identified experimentally and confirmed by molecular dynamics simulations, using a newly developed force field for methane–methane and fullerene–methane interaction. The effects of corrugation and curvature are discussed and compared with data for adsorption on graphite, graphene, and carbon nanotubes.

History Of Nutrient Inputs To The Northeastern United States, 1930–2000, Rebecca L. Hale, Joseph H. Hoover, Wilfred M. Wollheim, Charles J. Vorosmarty

Faculty Publications

Humans have dramatically altered nutrient cycles at local to global scales. We examined changes in anthropogenic nutrient inputs to the northeastern United States (NE) from 1930 to 2000. We created a comprehensive time series of anthropogenic N and P inputs to 437 counties in the NE at 5 year intervals. Inputs included atmospheric N deposition, biological N2 fixation, fertilizer, detergent P, livestock feed, and human food. Exports included exports of feed and food and volatilization of ammonia. N inputs to the NE increased throughout the study period, primarily due to increases in atmospheric deposition and fertilizer. P inputs increased until …

Riverine Ecosystem Services And The Thermoelectric Sector: Strategic Issues Facing The Northeastern United States, Ariel Miara, Charles J. Vorosmarty, Robert J. Stewart, Wilfred M. Wollheim, Bernice Rosenzweig

Faculty Publications

Major strategic issues facing the global thermoelectric sector include environmental regulation, climate change and increasing electricity demand. We have addressed such issues by modeling thermoelectric generation in the Northeastern United States that is reliant on cooling under five sensitivity tests to evaluate losses/gains in power production, thermal pollution and suitable aquatic habitat, comparing the contemporary baseline (2000–2010) with potential future states. Integral to the analysis, we developed a methodology to quantify river water availability for cooling, which we define as an ecosystem service.

Projected climate conditions reduce river water available for efficient power plant operations and the river's capacity to …

Controls On Dissolved Organic Carbon Quantity And Chemical Character In Temperate Rivers Of North America, Kevin W. Hanley, Wilfred M. Wollheim, Joseph Salisbury, Thomas Huntington, George Aiken

Faculty Publications

Understanding the processes controlling the transfer and chemical composition of dissolved organic carbon (DOC) in freshwater systems is crucial to understanding the carbon cycle and the effects of DOC on water quality. Previous studies have identified watershed‐scale controls on bulk DOC flux and concentration among small basins but fewer studies have explored controls among large basins or simultaneously considered the chemical composition of DOC. Because the chemical character of DOC drives riverine biogeochemical processes such as metabolism and photodegradation, accounting for chemical character in watershed‐scale studies will improve the way bulk DOC variability in rivers is interpreted. We analyzed DOC …

Horizontal Cooling Towers: Riverine Ecosystem Services And The Fate Of Thermoelectric Heat In The Contemporary Northeast Us, Robert J. Stewart, Wilfred M. Wollheim, Ariel Miara, Charles J. Vorosmarty, Balazs M. Fekete, Richard B. Lammers, Bernice Rosenzweig

Faculty Publications

The electricity sector is dependent on rivers to provide ecosystem services that help regulate excess heat, either through provision of water for evaporative cooling or by conveying, diluting and attenuating waste heat inputs. Reliance on these ecosystem services alters flow and temperature regimes, which impact fish habitat and other aquatic ecosystem services. We demonstrate the contemporary (2000–2010) dependence of the electricity sector on riverine ecosystem services and associated aquatic impacts in the Northeast US, a region with a high density of thermoelectric power plants. We quantify these dynamics using a spatially distributed hydrology and water temperature model (the framework for …

Endothelial Activation Microparticles And Inflammation Status Improve With Exercise Training In African Americans, Dianne M. Babbitt, Keith M. Diaz, Deborah L. Feairheller, Kathleen M. Sturgeon, Amanda M. Perkins, Praveen Veerabhadrappa, Sheara T. Williamson, Jan Krezschmar, Chenyi Ling, Hojun Lee, Heather Grimm, Sunny R. Thakkar

Faculty Publications

African Americans have the highest prevalence of hypertension in the world which may emanate from their predisposition to heightened endothelial inflammation. The purpose of this study was to determine the effects of a 6-month aerobic exercise training (AEXT) intervention on the inflammatory biomarkers interleukin-10 (IL-10), interleukin-6 (IL-6), and endothelial microparticle (EMP) CD62E+ and endothelial function assessed by flow-mediated dilation (FMD) in African Americans. A secondary purpose was to evaluate whether changes in IL-10, IL-6, or CD62E+ EMPs predicted the change in FMD following the 6-month AEXT intervention. A pre-post design was employed with baseline evaluation including office blood pressure, FMD, …

Adsorption Of Hydrogen On Neutral And Charged Fullerene: Experiment And Theory, Alexander Kaiser, Christian Leidlmair, Peter Bartl, Samuel Zottl, Stephan Denifl, Andreas Mauracher, Michael Probst, Paul Scheier, Olof Echt

Faculty Publications

Helium droplets are doped with fullerenes (either C60 or C70) and hydrogen (H2 or D2) and investigated by high-resolution mass spectrometry. In addition to pure helium and hydrogen cluster ions, hydrogen-fullerene complexes are observed upon electron ionization. The composition of the main ion series is (H2)nHCm+ where m = 60 or 70. Another series of even-numbered ions, (H2)nCm+, is slightly weaker in stark contrast to pure hydrogen cluster ions for which the even-numbered series (H2)n+ is barely detectable. The ion series (H2)nHCm+ and (H2)nCm+ exhibit abrupt drops in ion abundance at n = 32 for C60 and 37 for C70, …

Oneironaut: New And Used Poems, Mark Bonica

Faculty Publications

From dream invading penguins to retired poker players, Hermes on a skateboard and Dionysus drinking Mad Dog, butterflies and stock markets, astronomy explained with Jell-O, flying pianos and elves who work at the grocery store - this second collection of poetry from Mark Bonica, following up on "Accounting, An Introduction", explores a variety of emotions, moods, and life moments using devices from the understated ordinary to the fantastical.

Joint Analysis Of Stressors And Ecosystem Services To Enhance Restoration Effectiveness, J. David Allan, Peter B. Mcintyre, Sigrid D. P. Smith, Benjamin S. Halpern, Gregory L. Boyer, Andy Buchsbaum, G. A. Burton Jr., Linda M. Campbell, W. Lindsay Chadderton, Jan J. H. Ciborowski, Patrick J. Doran, Tim Eder, Dana M. Infante, Lucinda B. Johnson, Christine A. Joseph, Adrienne L. Marino, Alexander A. Prusevich, Jennifer G. Read, Joan B. Rose, Edward S. Rutherford, Scott P. Sowa, Alan D. Steinman

Faculty Publications

With increasing pressure placed on natural systems by growing human populations, both scientists and resource managers need a better understanding of the relationships between cumulative stress from human activities and valued ecosystem services. Societies often seek to mitigate threats to these services through large-scale, costly restoration projects, such as the over one billion dollar Great Lakes Restoration Initiative currently underway. To help inform these efforts, we merged high-resolution spatial analyses of environmental stressors with mapping of ecosystem services for all five Great Lakes. Cumulative ecosystem stress is highest in near-shore habitats, but also extends offshore in Lakes Erie, Ontario, and …

Climate And Demographic Change In Arctic Alaska, Lawrence C. Hamilton

Faculty Publications

No abstract provided.