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Modeling whole‐tree carbon assimilation rate using observed transpiration rates and needle sugar carbon isotope ratios
Author(s) -
Hu Jia,
Moore David J. P.,
RiverosIregui Diego A.,
Burns Sean P.,
Monson Russell K.
Publication year - 2010
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.2009.03154.x
Subject(s) - transpiration , environmental science , atmospheric sciences , water use efficiency , primary production , vapour pressure deficit , ecosystem , carbon cycle , ecology , photosynthesis , botany , biology , geology
Summary• 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 (δ 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 observations 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 δ 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.