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Harvard Forest REU Symposium Abstract 2021

  • Title: Exudate in, Carbon out: the effect of specific root exudates on soil carbon dynamics
  • Author: Arturo A Aguilar (Harvard University)
  • Abstract:

    Soil organic matter (SOM) dynamics hold considerable influence over soil carbon cycling and sequestration of carbon from the atmosphere. Specifically, a portion of SOM chemically binds with minerals to form mineral-associated organic matter (MAOM), resulting in the immobilization of carbon for decades to centuries. Plant root exudates, low-molecular-weight organic carbon compounds such as carbohydrates, organic acids, and amino acids, are thought to influence the formation and loss of SOM. The effect of root exudates on SOM pools is known to vary between specific exudate types. To quantify this varying effect, we analyzed data from an artificial root experiment that isotopically traced exudate carbon in SOM pools. We then integrated the data from this experiment into a quantitative review of studies on the effect of specific root exudates on soil carbon dynamics. The experimental results show that exudate type had no significant effect on the change in MAOM carbon of soil samples. However, the allocation of labeled carbon was significantly higher in the carbohydrate treatment. Data from the quantitative review found that carbohydrate exudate causes a small net increase in SOM carbon while amino acid and organic acid exudates exert a net negative effect on SOM pools. These results suggest that exudate inputs cause an overall increase in the amount of carbon lost from soil. The findings of this study contribute to a better understanding of root exudation’s role in the global carbon cycle and may improve future carbon cycle modeling.

  • Research Category: Soil Carbon and Nitrogen Dynamics