Fulweiler Robinson W.

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Fulweiler
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Robinson W.
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  • Article
    Soil warming accelerates biogeochemical silica cycling in a temperate forest.
    (Frontiers Media, 2019-09-11) Gewirtzman, Jonathan ; Tang, Jianwu ; Melillo, Jerry M. ; Werner, William J. ; Kurtz, Andrew C. ; Fulweiler, Robinson W. ; Carey, Joanna C.
    Biological cycling of silica plays an important role in terrestrial primary production. Soil warming stemming from climate change can alter the cycling of elements, such as carbon and nitrogen, in forested ecosystems. However, the effects of soil warming on the biogeochemical cycle of silica in forested ecosystems remain unexplored. Here we examine long-term forest silica cycling under ambient and warmed conditions over a 15-year period of experimental soil warming at Harvard Forest (Petersham, MA). Specifically, we measured silica concentrations in organic and mineral soils, and in the foliage and litter of two dominant species (Acer rubrum and Quercus rubra), in a large (30 × 30 m) heated plot and an adjacent control plot (30 × 30 m). In 2016, we also examined effects of heating on dissolved silica in the soil solution, and conducted a litter decomposition experiment using four tree species (Acer rubrum, Quercus rubra, Betula lenta, Tsuga canadensis) to examine effects of warming on the release of biogenic silica (BSi) from plants to soils. We find that tree foliage maintained constant silica concentrations in the control and warmed plots, which, coupled with productivity enhancements under warming, led to an increase in total plant silica uptake. We also find that warming drove an acceleration in the release of silica from decaying litter in three of the four species we examined, and a substantial increase in the silica dissolved in soil solution. However, we observe no changes in soil BSi stocks with warming. Together, our data indicate that warming increases the magnitude of silica uptake by vegetation and accelerates the internal cycling of silica in in temperate forests, with possible, and yet unresolved, effects on the delivery of silica from terrestrial to marine systems.
  • Article
    Ideas and perspectives: a strategic assessment of methane and nitrous oxide measurements in the marine environment
    (European Geosciences Union, 2020-11-26) Wilson, Samuel T. ; Al-Haj, Alia N. ; Bourbonnais, Annie ; Frey, Claudia ; Fulweiler, Robinson W. ; Kessler, John D. ; Marchant, Hannah K. ; Milucka, Jana ; Ray, Nicholas E. ; Suntharalingam, Parvadha ; Thornton, Brett F. ; Upstill-Goddard, Robert C. ; Weber, Thomas S. ; Arévalo-Martínez, Damian L. ; Bange, Hermann W. ; Benway, Heather M. ; Bianchi, Daniele ; Borges, Alberto V. ; Chang, Bonnie X. ; Crill, Patrick M. ; del Valle, Daniela A. ; Farías, Laura ; Joye, Samantha B. ; Kock, Annette ; Labidi, Jabrane ; Manning, Cara C. ; Pohlman, John W. ; Rehder, Gregor ; Sparrow, Katy J. ; Tortell, Philippe D. ; Treude, Tina ; Valentine, David L. ; Ward, Bess B. ; Yang, Simon ; Yurganov, Leonid N.
    In the current era of rapid climate change, accurate characterization of climate-relevant gas dynamics – namely production, consumption, and net emissions – is required for all biomes, especially those ecosystems most susceptible to the impact of change. Marine environments include regions that act as net sources or sinks for numerous climate-active trace gases including methane (CH4) and nitrous oxide (N2O). The temporal and spatial distributions of CH4 and N2O are controlled by the interaction of complex biogeochemical and physical processes. To evaluate and quantify how these mechanisms affect marine CH4 and N2O cycling requires a combination of traditional scientific disciplines including oceanography, microbiology, and numerical modeling. Fundamental to these efforts is ensuring that the datasets produced by independent scientists are comparable and interoperable. Equally critical is transparent communication within the research community about the technical improvements required to increase our collective understanding of marine CH4 and N2O. A workshop sponsored by Ocean Carbon and Biogeochemistry (OCB) was organized to enhance dialogue and collaborations pertaining to marine CH4 and N2O. Here, we summarize the outcomes from the workshop to describe the challenges and opportunities for near-future CH4 and N2O research in the marine environment.
  • Preprint
    Modeling denitrification in aquatic sediments
    ( 2008-10-10) Fennel, Katja ; Brady, Damian C. ; DiToro, Dominic ; Fulweiler, Robinson W. ; Gardner, Wayne S. ; Giblin, Anne E. ; McCarthy, Mark J. ; Rao, Alexandra ; Seitzinger, Sybil P. ; Thouvenot-Korppoo, Marie ; Tobias, Craig R.
    Sediment denitrification is a major pathway of fixed nitrogen loss from aquatic systems. Due to technical difficulties in measuring this process and its spatial and temporal variability, estimates of local, regional and global denitrification have to rely on a combination of measurements and models. Here we review approaches to describing denitrification in aquatic sediments, ranging from mechanistic diagenetic models to empirical parameterizations of nitrogen fluxes across the sediment-water interface. We also present a compilation of denitrification measurements and ancillary data for different aquatic systems, ranging from freshwater to marine. Based on this data compilation we reevaluate published parameterizations of denitrification. We recommend that future models of denitrification use (1) a combination of mechanistic diagenetic models and measurements where bottom waters are temporally hypoxic or anoxic, and (2) the much simpler correlations between denitrification and sediment oxygen consumption for oxic bottom waters. For our data set, inclusion of bottom water oxygen and nitrate concentrations in a multivariate regression did not improve the statistical fit.
  • Article
    Does elevated CO2 alter silica uptake in trees?
    (Frontiers Media, 2015-01-13) Fulweiler, Robinson W. ; Maguire, Timothy J. ; Carey, Joanna C. ; Finzi, Adrien C.
    Human activities have greatly altered global carbon (C) and Nitrogen (N) cycling. In fact, atmospheric concentrations of carbon dioxide (CO2) have increased 40% over the last century and the amount of N cycling in the biosphere has more than doubled. In an effort to understand how plants will respond to continued global CO2 fertilization, long-term free-air CO2 enrichment experiments have been conducted at sites around the globe. Here we examine how atmospheric CO2 enrichment and N fertilization affects the uptake of silicon (Si) in the Duke Forest, North Carolina, a stand dominated by Pinus taeda (loblolly pine), and five hardwood species. Specifically, we measured foliar biogenic silica concentrations in five deciduous and one coniferous species across three treatments: CO2 enrichment, N enrichment, and N and CO2 enrichment. We found no consistent trends in foliar Si concentration under elevated CO2, N fertilization, or combined elevated CO2 and N fertilization. However, two-thirds of the tree species studied here have Si foliar concentrations greater than well-known Si accumulators, such as grasses. Based on net primary production values and aboveground Si concentrations in these trees, we calculated forest Si uptake rates under control and elevated CO2 concentrations. Due largely to increased primary production, elevated CO2 enhanced the magnitude of Si uptake between 20 and 26%, likely intensifying the terrestrial silica pump. This uptake of Si by forests has important implications for Si export from terrestrial systems, with the potential to impact C sequestration and higher trophic levels in downstream ecosystems.