Holmquist James R.

No Thumbnail Available
Last Name
Holmquist
First Name
James R.
ORCID

Filters

2018 - 2019 4 2020 - 2023 1
5
5
Reset filters

Settings

Search Results

Now showing 1 - 5 of 5
  • Article
    Author Correction : Accuracy and precision of tidal wetland soil carbon mapping in the conterminous United States
    (Nature Publishing Group, 2018-10-09) Holmquist, James R. ; Windham-Myers, Lisamarie ; Bliss, Norman B. ; Crooks, Stephen ; Morris, James T. ; Megonigal, J. Patrick ; Troxler, Tiffany G. ; Weller, Donald ; Callaway, John ; Drexler, Judith ; Ferner, Matthew C. ; Gonneea, Meagan E. ; Kroeger, Kevin D. ; Schile-Beers, Lisa ; Woo, Isa ; Buffington, Kevin ; Breithaupt, Joshua ; Boyd, Brandon M. ; Brown, Lauren N. ; Dix, Nicole ; Hice, Lyndie ; Horton, Benjamin P. ; MacDonald, Glen M. ; Moyer, Ryan P. ; Reay, William ; Shaw, Timothy ; Smith, Erik ; Smoak, Joseph M. ; Sommerfield, Christopher K. ; Thorne, Karen ; Velinsky, David ; Watson, Elizabeth ; Wilson Grimes, Kristin ; Woodrey, Mark
    This Article corrects an error in Equation 1
  • Article
    Carbon budget of tidal wetlands, estuaries, and shelf waters of eastern North America
    (John Wiley & Sons, 2018-04-04) Najjar, Raymond G. ; Herrmann, Maria ; Alexander, Richard ; Boyer, Elizabeth W. ; Burdige, David J. ; Butman, David ; Cai, Wei-Jun ; Canuel, Elizabeth A. ; Chen, Robert F. ; Friedrichs, Marjorie A. M. ; Feagin, Russell A. ; Griffith, Peter C. ; Hinson, Audra L. ; Holmquist, James R. ; Hu, Xinping ; Kemp, William M. ; Kroeger, Kevin D. ; Mannino, Antonio ; McCallister, S. Leigh ; McGillis, Wade R. ; Mulholland, Margaret R. ; Pilskaln, Cynthia H. ; Salisbury, Joseph E. ; Signorini, Sergio R. ; St-Laurent, Pierre ; Tian, Hanqin ; Tzortziou, Maria ; Vlahos, Penny ; Wang, Zhaohui Aleck ; Zimmerman, Richard C.
    Carbon cycling in the coastal zone affects global carbon budgets and is critical for understanding the urgent issues of hypoxia, acidification, and tidal wetland loss. However, there are no regional carbon budgets spanning the three main ecosystems in coastal waters: tidal wetlands, estuaries, and shelf waters. Here we construct such a budget for eastern North America using historical data, empirical models, remote sensing algorithms, and process‐based models. Considering the net fluxes of total carbon at the domain boundaries, 59 ± 12% (± 2 standard errors) of the carbon entering is from rivers and 41 ± 12% is from the atmosphere, while 80 ± 9% of the carbon leaving is exported to the open ocean and 20 ± 9% is buried. Net lateral carbon transfers between the three main ecosystem types are comparable to fluxes at the domain boundaries. Each ecosystem type contributes substantially to exchange with the atmosphere, with CO2 uptake split evenly between tidal wetlands and shelf waters, and estuarine CO2 outgassing offsetting half of the uptake. Similarly, burial is about equal in tidal wetlands and shelf waters, while estuaries play a smaller but still substantial role. The importance of tidal wetlands and estuaries in the overall budget is remarkable given that they, respectively, make up only 2.4 and 8.9% of the study domain area. This study shows that coastal carbon budgets should explicitly include tidal wetlands, estuaries, shelf waters, and the linkages between them; ignoring any of them may produce a biased picture of coastal carbon cycling.
  • Article
    Uncertainty in United States coastal wetland greenhouse gas inventorying
    (IOP Science, 2018-11-12) Holmquist, James R. ; Windham-Myers, Lisamarie ; Bernal, Blanca ; Byrd, Kristin B. ; Crooks, Stephen ; Gonneea, Meagan E. ; Herold, Nate ; Knox, Sara H. ; Kroeger, Kevin D. ; McCombs, John ; Megonigal, J. Patrick ; Lu, Meng ; Morris, James T. ; Sutton-Grier, Ariana E. ; Troxler, Tiffany G.
    Coastal wetlands store carbon dioxide (CO2) and emit CO2 and methane (CH4) making them an important part of greenhouse gas (GHG) inventorying. In the contiguous United States (CONUS), a coastal wetland inventory was recently calculated by combining maps of wetland type and change with soil, biomass, and CH4 flux data from a literature review. We assess uncertainty in this developing carbon monitoring system to quantify confidence in the inventory process itself and to prioritize future research. We provide a value-added analysis by defining types and scales of uncertainty for assumptions, burial and emissions datasets, and wetland maps, simulating 10 000 iterations of a simplified version of the inventory, and performing a sensitivity analysis. Coastal wetlands were likely a source of net-CO2-equivalent (CO2e) emissions from 2006–2011. Although stable estuarine wetlands were likely a CO2e sink, this effect was counteracted by catastrophic soil losses in the Gulf Coast, and CH4 emissions from tidal freshwater wetlands. The direction and magnitude of total CONUS CO2e flux were most sensitive to uncertainty in emissions and burial data, and assumptions about how to calculate the inventory. Critical data uncertainties included CH4 emissions for stable freshwater wetlands and carbon burial rates for all coastal wetlands. Critical assumptions included the average depth of soil affected by erosion events, the method used to convert CH4 fluxes to CO2e, and the fraction of carbon lost to the atmosphere following an erosion event. The inventory was relatively insensitive to mapping uncertainties. Future versions could be improved by collecting additional data, especially the depth affected by loss events, and by better mapping salinity and inundation gradients relevant to key GHG fluxes. Social Media Abstract: US coastal wetlands were a recent and uncertain source of greenhouse gasses because of CH4 and erosion.
  • Article
    Accuracy and precision of tidal wetland soil carbon mapping in the conterminous United States
    (Nature Publishing Group, 2018-06-21) Holmquist, James R. ; Windham-Myers, Lisamarie ; Bliss, Norman B. ; Crooks, Stephen ; Morris, James T. ; Megonigal, J. Patrick ; Troxler, Tiffany G. ; Weller, Donald ; Callaway, John ; Drexler, Judith ; Ferner, Matthew C. ; Gonneea, Meagan E. ; Kroeger, Kevin D. ; Schile-Beers, Lisa ; Woo, Isa ; Buffington, Kevin ; Breithaupt, Joshua ; Boyd, Brandon M. ; Brown, Lauren N. ; Dix, Nicole ; Hice, Lyndie ; Horton, Benjamin P. ; MacDonald, Glen M. ; Moyer, Ryan P. ; Reay, William ; Shaw, Timothy ; Smith, Erik ; Smoak, Joseph M. ; Sommerfield, Christopher K. ; Thorne, Karen ; Velinsky, David ; Watson, Elizabeth ; Wilson Grimes, Kristin ; Woodrey, Mark
    Tidal wetlands produce long-term soil organic carbon (C) stocks. Thus for carbon accounting purposes, we need accurate and precise information on the magnitude and spatial distribution of those stocks. We assembled and analyzed an unprecedented soil core dataset, and tested three strategies for mapping carbon stocks: applying the average value from the synthesis to mapped tidal wetlands, applying models fit using empirical data and applied using soil, vegetation and salinity maps, and relying on independently generated soil carbon maps. Soil carbon stocks were far lower on average and varied less spatially and with depth than stocks calculated from available soils maps. Further, variation in carbon density was not well-predicted based on climate, salinity, vegetation, or soil classes. Instead, the assembled dataset showed that carbon density across the conterminous united states (CONUS) was normally distributed, with a predictable range of observations. We identified the simplest strategy, applying mean carbon density (27.0 kg C m−3), as the best performing strategy, and conservatively estimated that the top meter of CONUS tidal wetland soil contains 0.72 petagrams C. This strategy could provide standardization in CONUS tidal carbon accounting until such a time as modeling and mapping advancements can quantitatively improve accuracy and precision.
  • Article
    Mapping methane reduction potential of tidal wetland restoration in the United States
    (Nature Research, 2023-10-05) Holmquist, James R. ; Eagle, Meagan ; Lee Molinari, Rebecca ; Nick, Sydney K. ; Stachowicz, Liana C. ; Kroeger, Kevin D.
    Coastal wetlands can emit excess methane in cases where they are impounded and artificially freshened by structures that impede tidal exchange. We provide a new assessment of coastal methane reduction opportunities for the contiguous United States by combining multiple publicly available map layers, reassessing greenhouse gas emissions datasets, and applying scenarios informed by geospatial information system and by surveys of coastal managers. Independent accuracy assessment indicates that coastal impoundments are under-mapped at the national level by a factor of one-half. Restorations of freshwater-impounded wetlands to brackish or saline conditions have the greatest potential climate benefit of all mapped conversion opportunities, but were rarer than other potential conversion events. At the national scale we estimate potential emissions reduction for coastal wetlands to be 0.91 Teragrams of carbon dioxide equivalents year−1, a more conservative assessment compared to previous estimates. We provide a map of 1,796 parcels with the potential for tidal re-connection.