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2015 | Carbon Fluxes

Ariel View of Streams

FACULTY SEED GRANT | Global Change Center

Surface-subsurface connectivity in karst landscapes: implications for terrestrial water and carbon fluxes

  • Dr. Ryan Stewart, Crop & Soil Environmental Science
  • Dr. Madeline Schreiber, Geosciences
  • Dr. Daniel McLaughlin, Forest Resources & Environmental Conservation

Karst landscapes – characterized by soluble limestone bedrock – encompass 20% of the earth’s landmass and provide water for 20-25% of the world’s population. In addition, caves within karst systems are home to great biodiversity, including endangered (and often endemic) species such as isopods, amphipods, spiders, and fish. However, karst systems worldwide are experiencing lowered water levels and pollution, and it is predicted that climate and land use change will exacerbate both of these conditions. At the same time, due to the high carbonate content of bedrock and soils, karst systems may potentially act as large-scale sinks of atmospheric carbon, though the magnitude and timing of subsurface carbon fluxes in karst areas are poorly understood.

Our group seeks to study how the hydrologic connectivity between terrestrial ecosystems and underlying geology affects subsurface carbon storages and fluxes in karst landscapes, using the James Cave field site in southwest Virginia. In 2007, we instrumented this cave to study karst hydrology, and since then, our group has collected over eight years of data on the timing, magnitude, and chemistry of recharge (drip water) within the cave. However, to understand couplings between hydrologic (e.g., evapotranspiration and recharge) and carbon fluxes, we also need to measure the temporal and spatial dynamics of water and carbon within the soil profile above the cave. Therefore, in this study we will install soil CO2 sensors and water content sensors above the cave. We will also deploy a solar-powered data logger to collect and store data to continue hydrologic and geochemical monitoring within the cave.

With these high-resolution data, we seek to elucidate the dynamic role of hydrologic connectivity (and disconnectivity) on carbon fluxes in the karst “critical zone”, with attendant local (dissolution) and global (C-sequestration) implications.

The additional instrumentation provided by this seed grant will move us towards our ultimate goal of establishing the James Cave site as a world-class observatory for surface-subsurface hydrologic and biogeochemical interactions. Though currently focused on hydrology and biogeochemistry, the James Cave site has tremendous potential for collaborative research on topics such as paleoclimatology and cave biodiversity.