Bio

Alexandra Hedgpeth is a biogeochemist whose research explores how soil carbon cycling in peatlands responds to environmental change. Her work focuses on understanding the mechanisms that regulate carbon storage and greenhouse gas production in both tropical and boreal wetlands, with a particular emphasis on the vulnerability of deep, ancient carbon to modern surface inputs and hydrologic shifts.

Through her Ph.D. research at the University of California, Los Angeles, Alex has developed and applied novel isotopic and geochemical approaches—including implementing radiocarbon dating, stable isotope analyses, and high-resolution molecular characterization—to trace the sources and fates of carbon in peat soils. Her fieldwork spans a range of ecosystems, from ombrotrophic bogs in the Arctic to saturated tropical peat domes in Central America. This comparative framework allows her to identify unifying controls on carbon preservation and loss across climate zones.

Alex's research integrates field measurements, laboratory experiments, and synthesis of global datasets. She is a key contributor to multi-institutional efforts to model peatland carbon cycling under climate change scenarios, including DOE- and NSF-supported initiatives. Her work helps clarify the role of peatlands as both long-term carbon sinks and potential sources of atmospheric CO₂ and CH₄ under future disturbance.

In addition to her scientific contributions, Alex is committed to collaborative, interdisciplinary research and has worked closely with partners at national laboratories, the Smithsonian Tropical Research Institute, and international data synthesis networks. She is especially interested in questions with high uncertainty and high relevance to climate feedbacks—such as thresholds in biogeochemical function and the persistence of deep soil carbon under hydrologic change.

Stanford Advisors

Contact

  • Academic
    hedgpea@stanford.edu
    University - Scholar Department: Department of Earth System Science Position: Postdoctoral Scholar

Additional Info

All Publications

  • From the top: surface-derived carbon fuels greenhouse gas production at depth in a peatland BIOGEOSCIENCES Hedgpeth, A., Hoyt, A. M., Cavanaugh, K. C., McFarlane, K. J., Cusack, D. F. 2025; 22 (11): 2667-2690

    View details for DOI 10.5194/bg-22-2667-2025

    View details for Web of Science ID 001507507200001

  • Root Characteristics Vary with Depth Across Four Lowland Seasonal Tropical Forests ECOSYSTEMS Cordeiro, A. L., Cusack, D. F., Dietterich, L. H., Hockaday, W. C., Mcfarlane, K. J., Sivapalan, V., Hedgpeth, A., Neupane, A., Colburn, L., Konwent, W., Oppler, G., Reu, J. C., Valdes, E., Wright, S. 2024; 27 (8): 1104-1122

    View details for DOI 10.1007/s10021-024-00941-w

    View details for Web of Science ID 001345366200001

  • High methane concentrations in tidal salt marsh soils: Where does the methane go? Global change biology Capooci, M., Seyfferth, A. L., Tobias, C., Wozniak, A. S., Hedgpeth, A., Bowen, M., Biddle, J. F., McFarlane, K. J., Vargas, R. 2024; 30 (1): e17050

    Abstract

    Tidal salt marshes produce and emit CH4 . Therefore, it is critical to understand the biogeochemical controls that regulate CH4 spatial and temporal dynamics in wetlands. The prevailing paradigm assumes that acetoclastic methanogenesis is the dominant pathway for CH4 production, and higher salinity concentrations inhibit CH4 production in salt marshes. Recent evidence shows that CH4 is produced within salt marshes via methylotrophic methanogenesis, a process not inhibited by sulfate reduction. To further explore this conundrum, we performed measurements of soil-atmosphere CH4 and CO2 fluxes coupled with depth profiles of soil CH4 and CO2 pore water gas concentrations, stable and radioisotopes, pore water chemistry, and microbial community composition to assess CH4 production and fate within a temperate tidal salt marsh. We found unexpectedly high CH4 concentrations up to 145,000 μmol mol-1 positively correlated with S2- (salinity range: 6.6-14.5 ppt). Despite large CH4 production within the soil, soil-atmosphere CH4 fluxes were low but with higher emissions and extreme variability during plant senescence (84.3 ± 684.4 nmol m-2  s-1 ). CH4 and CO2 within the soil pore water were produced from young carbon, with most Δ14 C-CH4 and Δ14 C-CO2 values at or above modern. We found evidence that CH4 within soils was produced by methylotrophic and hydrogenotrophic methanogenesis. Several pathways exist after CH4 is produced, including diffusion into the atmosphere, CH4 oxidation, and lateral export to adjacent tidal creeks; the latter being the most likely dominant flux. Our findings demonstrate that CH4 production and fluxes are biogeochemically heterogeneous, with multiple processes and pathways that can co-occur and vary in importance over the year. This study highlights the potential for high CH4 production, the need to understand the underlying biogeochemical controls, and the challenges of evaluating CH4 budgets and blue carbon in salt marshes.

    View details for DOI 10.1111/gcb.17050

    View details for PubMedID 38273533

  • Effects of experimental and seasonal drying on soil microbial biomass and nutrient cycling in four lowland tropical forests BIOGEOCHEMISTRY Dietterich, L. H., Bouskill, N. J., Brown, M., Castro, B., Chacon, S. S., Colburn, L., Cordeiro, A. L., Garcia, E. H., Gordon, A., Gordon, E., Hedgpeth, A., Konwent, W., Oppler, G., Reu, J., Tsiames, C., Valdes, E., Zeko, A., Cusack, D. F. 2022; 161 (2): 227-250

    View details for DOI 10.1007/s10533-022-00980-2

    View details for Web of Science ID 000865398500001

  • Age and chemistry of dissolved organic carbon reveal enhanced leaching of ancient labile carbon at the permafrost thaw zone BIOGEOSCIENCES McFarlane, K. J., Throckmorton, H. M., Heikoop, J. M., Newman, B. D., Hedgpeth, A. L., Repasch, M. N., Guilderson, T. P., Wilson, C. J. 2022; 19 (4): 1211-1223

    View details for DOI 10.5194/bg-19-1211-2022

    View details for Web of Science ID 000765881600001

  • Reducing climate impacts of beef production: A synthesis of life cycle assessments across management systems and global regions. Global change biology Cusack, D. F., Kazanski, C. E., Hedgpeth, A., Chow, K., Cordeiro, A. L., Karpman, J., Ryals, R. 2021; 27 (9): 1721-1736

    Abstract

    The global demand for beef is rapidly increasing (FAO, 2019), raising concern about climate change impacts (Clark et al., 2020; Leip et al., 2015; Springmann et al., 2018). Beef and dairy contribute over 70% of livestock greenhouse gas emissions (GHG), which collectively contribute ~6.3 Gt CO2 -eq/year (Gerber et al., 2013; Herrero et al., 2016) and account for 14%-18% of human GHG emissions (Friedlingstein et al., 2019; Gerber et al., 2013). The utility of beef GHG mitigation strategies, such as land-based carbon (C) sequestration and increased production efficiency, are actively debated (Garnett et al., 2017). We compiled 292 local comparisons of "improved" versus "conventional" beef production systems across global regions, assessing net GHG emission data from Life Cycle Assessment (LCA) studies. Our results indicate that net beef GHG emissions could be reduced substantially via changes in management. Overall, a 46 % reduction in net GHG emissions per unit of beef was achieved at sites using carbon (C) sequestration management strategies on grazed lands, and an 8% reduction in net GHGs was achieved at sites using growth efficiency strategies. However, net-zero emissions were only achieved in 2% of studies. Among regions, studies from Brazil had the greatest improvement, with management strategies for C sequestration and efficiency reducing beef GHG emissions by 57%. In the United States, C sequestration strategies reduced beef GHG emissions by over 100% (net-zero emissions) in a few grazing systems, whereas efficiency strategies were not successful at reducing GHGs, possibly because of high baseline efficiency in the region. This meta-analysis offers insight into pathways to substantially reduce beef production's global GHG emissions. Nonetheless, even if these improved land-based and efficiency management strategies could be fully applied globally, the trajectory of growth in beef demand will likely more than offset GHG emissions reductions and lead to further warming unless there is also reduced beef consumption.

    View details for DOI 10.1111/gcb.15509

    View details for PubMedID 33657680

    View details for PubMedCentralID PMC8248168

  • Expert assessment of future vulnerability of the global peatland carbon sink NATURE CLIMATE CHANGE Loisel, J., Gallego-Sala, A., Amesbury, M. J., Magnan, G., Anshari, G., Beilman, D. W., Benavides, J. C., Blewett, J., Camill, P., Charman, D. J., Chawchai, S., Hedgpeth, A., Kleinen, T., Korhola, A., Large, D., Mansilla, C. A., Muller, J., van Bellen, S., West, J. B., Yu, Z., Bubier, J. L., Garneau, M., Moore, T., Sannel, A. K., Page, S., Valiranta, M., Bechtold, M., Brovkin, Cole, L. S., Chanton, J. P., Christensen, T. R., Davies, M. A., De Vleeschouwer, F., Finkelstein, S. A., Frolking, S., Galka, M., Gandois, L., Girkin, N., Harris, L., Heinemeyer, A., Hoyt, A. M., Jones, M. C., Joos, F., Juutinen, S., Kaiser, K., Lacourse, T., Lamentowicz, M., Larmola, T., Leifeld, J., Lohila, A., Milner, A. M., Minkkinen, K., Moss, P., Naafs, B. A., Nichols, J., O'Donnell, J., Payne, R., Philben, M., Piilo, S., Quillet, A., Ratnayake, A. S., Roland, T. P., Sjogersten, S., Sonnentag, O., Swindles, G. T., Swinnen, W., Talbot, J., Treat, C., Valach, A. C., Wu, J. 2021; 11 (1): 70-+

    View details for DOI 10.1038/s41558-020-00944-0

    View details for Web of Science ID 000598987000002

https://orcid.org/0000-0002-4004-007X