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Harvard Forest REU Symposium Abstract 2022

  • Title: Forest Carbon Cycling Belowground: Changes in Root-Based Carbon Flux Under Warming Temperatures
  • Author: Cristina L Winters (Humboldt State University)
  • Abstract:

    Terrestrial soils are Earth’s largest organic carbon sink; however, the effect that warming temperatures have on soil carbon cycling as it relates to roots and their mycorrhizal (fungal) associates is not well understood. Shifts in plant species composition under climate change, specifically in northeastern temperate forests (a critical U.S. carbon sink) may have significant consequences for soil carbon storage. Plant roots and their fungal associates regulate carbon flux belowground via root exudation (release of organic compounds into soil) and root respiration (release of carbon dioxide), and warming may affect both metabolisms uniquely. We investigate (1) how long-term soil warming alters the relationships between root exudation and respiration; and (2) if roots associated with different mycorrhizal types experience the change in the relationship between exudation and respiration differently. This is important as species composition in New England forests shifts toward a greater proportion of arbuscular-associated trees, especially maples. In forested plots that are warmed using buried heating cables, we took paired root exudation and respiration measurements from arbuscular- and ectomycorrhizal-associated tree species in response to long term soil warming at the Harvard Forest Long Term Ecological Research (LTER) site in Petersham, MA. Additionally, we measured the respiration levels of these fine root systems once exudate collection was complete. We expected the slope of the relationship between root exudation and respiration to increase under warming, indicating a greater proportion of root exudates immediately respired and potentially decreasing the total belowground exudate-based carbon storage. This could have ecosystem-scale consequences for total carbon storage.

  • Research Category: Soil Carbon and Nitrogen Dynamics