Modeling Whole-Tree Carbon Assimilation Rate Using Observed Transpiration Rates And Needle Sugar Carbon Isotope Ratios

  • Sites: US-NR1
  • Publication Type: JOUR
  • Authors: Hu, J.; Moore, D. J.; Riveros-Iregui, D. A.; Burns, S. P.; Monson, R. K.

  • • Understanding controls over plant–atmosphere CO 2 exchange is important for
    quantifying carbon budgets across a range of spatial and temporal scales. In this
    study, we used a simple approach to estimate whole-tree CO 2 assimilation rate
    (A Tree ) in a subalpine forest ecosystem.
    • We analysed the carbon isotope ratio (d 13 C) of extracted needle sugars and
    combined it with the daytime leaf-to-air vapor pressure deficit to estimate tree
    water-use efficiency (WUE). The estimated WUE was then combined with obser-
    vations of tree transpiration rate (E) using sap flow techniques to estimate A Tree .
    Estimates of A Tree for the three dominant tree species in the forest were combined
    with species distribution and tree size to estimate and gross primary productivity
    (GPP) using an ecosystem process model.
    • A sensitivity analysis showed that estimates of A Tree were more sensitive to
    dynamics in E than d 13 C. At the ecosystem scale, the abundance of lodgepole pine
    trees influenced seasonal dynamics in GPP considerably more than Engelmann
    spruce and subalpine fir because of its greater sensitivity of E to seasonal climate
    variation.
    • The results provide the framework for a nondestructive method for estimating
    whole-tree carbon assimilation rate and ecosystem GPP over daily-to weekly time
    scales.


  • Journal: New Phytologist
  • Funding Agency: NSF, NICCR
  • Citation Information:
  • Volume: 185
  • No: 4
  • Pages: 1000-1015
  • Publication Year: 2010/03
  • DOI: 10.1111/j.1469-8137.2009.03154.x
  • https://doi.org/10.1111/j.1469-8137.2009.03154.x