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Catchment‐Scale Shifts in the Magnitude and Partitioning of Carbon Export in Response to Changing Hydrologic Connectivity in a Northern Hardwood Forest
Author(s) -
Senar Oscar E.,
Webster Kara L.,
Creed Irena F.
Publication year - 2018
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1029/2018jg004468
Subject(s) - environmental science , ecotone , drainage basin , wetland , carbon cycle , hydrology (agriculture) , soil carbon , dissolved organic carbon , climate change , carbon fibers , soil water , ecology , ecosystem , soil science , geology , geography , materials science , cartography , geotechnical engineering , shrub , composite number , composite material , biology
The capacity of forest soils to store organic carbon is influenced by changing hydrologic connectivity. We hypothesized that hydrologic connectivity, the water‐mediated transfer of matter and energy between different landscape positions, controls the partitioning between aquatic and atmospheric soil carbon fates. Results from a 5‐year study of a northern hardwood forested catchment indicated that hydrologic connectivity affected both the magnitude and fate of carbon export. Atmospheric carbon export was the major export pathway from the catchment; its rate was regulated by topographic position (i.e., uplands, ecotones, and wetlands) but enhanced or supressed through changes in soil moisture and hydrologic connectivity. Wetter soil conditions reduced CO 2 flux from the ecotones and wetlands where microbial respiration was oxygen‐limited, whereas drier soil conditions that decreased hydrologic connectivity increased CO 2 flux by relieving the oxygen limitation. In contrast, aquatic carbon export was a minor export pathway from the catchment and was driven by hydrologic connectivity, with less carbon export during relatively low discharge years. Past trends suggest a shift to a warmer climate and changes in the timing, duration, and intensity of hydrologic connectivity that are leading to an increase in annual atmospheric carbon export but a decrease in annual aquatic carbon export, despite the intensification of autumn storms. The increase in atmospheric carbon export creates a positive feedback for climate warming that will further disrupt hydrologic connectivity and aquatic carbon export, with consequences for downstream streams and lakes.