Oral Presentation Society for Freshwater Science 2025 Annual Meeting

Connecting stream CO2 dynamics to landscape mosaics and hydrologic regimes (117099)

Erin R Hotchkiss 1 , Frances Iannucci 1 , Ashif Hasan Abir 2 , Hannah Conroy 3 , Kristin Kraus 4 , David Butman 3 , Kaelin Cawley 5 , Keli Goodman 5 , Jeremy B Jones 4 , Wilfred M Wollheim 2
  1. Virginia Tech, Blacksburg, VA, USA
  2. University of New Hampshire, Durham, NH, USA
  3. University of Washington, Seattle, WA, USA
  4. University of Alaska Fairbanks, Fairbanks, AK, USA
  5. National Ecological Observatory Network, Battelle, Boulder, CO, USA

Water moves landscape-derived materials to stream networks; stream biogeochemical signals thus offer insights to better understand terrestrial carbon cycling, landscape export dynamics, consequences of hydrologic disturbances, and associated patterns of in-stream biology. We selected five National Ecological Observatory Network (NEON) stream monitoring sites with nearby NEON terrestrial sites in different eco-regions of the United States: an Appalachian temperate forest stream with large autumn leaf fall inputs and wet winters (WALK), a tallgrass prairie stream with intermittent flow (KING), a Rocky Mountain forest stream that freezes annually and has a high flow snowmelt period (COMO), a temperate rainforest stream with wet winters (MART), and a boreal stream draining discontinuous permafrost that freezes annually (CARI). Each site has distinct climate and hydrologic regimes and thus, unique patterns of landscape carbon storage, land-water fluxes, and in-stream carbon cycling. We integrated new high-frequency in-stream CO2 measurements with NEON data from upland soils, shallow riparian groundwater wells, and streams to assess drivers of CO2 regimes in each of our five study streams. All streams had highest pCO2 concentrations during lower streamflows (site-specific discharge-CO2 linear model R2 values ranged from 0.1 to 0.8), as a consequence of stream drying (KING), and during ice-covered periods of the year (COMO, CARI). The morphology of stream corridors generated differences in riparian shallow groundwater pCO2 relative to upland soils, thus influencing the relative synchrony of pCO2 in soils, riparian wells, and streams at annual timescales. For example, growing season patterns in CARI stream pCO2 were more similar to the deepest upland soil pCO2 (10cm depth) than riparian wells and springs. In contrast, WALK stream pCO2 and shallow soil pCO2 (3cm depth) were most similar across seasons. Ongoing research is using these and other time series data to integrate and model land-water carbon fluxes, weathering, streamflow-carbon dynamics, & in-stream CO2 production by aerobic respiration.