• Contributors: Sonia Wharton
  • Publication Type: JOUR
  • Authors: Taylor, A.J., Lai, C.-T., Hopkins, F.M., Wharton, S., Bible, K., Xu, X., Phillips, C., Bush, S., Ehleringer, J.R.

  • Temperate forests play an important role in the global
    carbon cycle, and are thought to currently be a sink for
    atmospheric CO2. However,we lack understanding of
    the drivers of forest carbon accumulation and loss,
    hampering our ability to predict carbon cycle
    responses to global change. In this study,we used CO2
    flux and radiocarbon (14C) measurements to investigate
    the role of seasonal drivers on soil respiration.
    Radiocarbon measurements of CO2 evolved during
    incubation of fine roots and root-free soils at the
    beginning and end of the growing season (April and
    August) showed that these two soil respiration sources
    (fine roots vis-a`-vis soils) have different mean residence
    times that stayed constant between seasons.
    Radiocarbon measurements show that root respiration
    was made up of carbon fixed 3–5 years prior to
    sampling, and that heterotrophic respiration was
    made up of carbon fixed 7–10 years prior. The difference
    in radiocarbon signature between the two soursources
    allowed us to partition autotrophic and
    heterotrophic respiration sources for soil respiration
    measurements in the field. We observed a small but
    significant increase in D14C of soil respiration between
    April and August, suggesting an increase in heterotrophic
    respiration sources over the growing season.
    Using a two end-member mixing model, we estimate
    that 55 ± 22% of soil respiration originated from
    autotrophic (root) sources in April, but their contribution
    dropped to 38 ± 21% in August. These findings
    suggest that the contribution of root respiration
    increases at a time of high productivity and/or as a
    result of relatively low microbial respiration in the
    early spring in this old-growth coniferous forest.


  • Journal: Ecosystems
  • Funding Agency:
  • Volume: 18
  • No:
  • Pages: 459-470
  • Publication Year: 2015
  • DOI:
  • ISBN: