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WEI SUN, VÍCTOR RESCO and DAVID G. WILLIAMS Environmental and physiological controls on the carbon isotope composition of CO2 respired by leaves and roots of a C3 woody legume (Prosopis velutina) and a C4 perennial grass (Sporobolus wrightii) Plant, Cell & Environment 35

Article first published online: 24 OCT 2011 | DOI: 10.1111/j.1365-3040.2011.02436.x

The δ13C value of CO2 respired from roots (δ13CR_root) and leaves (δ13CR_leaf) is important for tracing C fluxes at the ecosystem scale, however the mechanisms underlying temporal variation in these isotopic signals are not fully resolved. We tested hypotheses that short-term variation in δ13CR_leaf and δ13CR_root are regulated by the δ13C values of primary respiratory substrates and changes in apparent respiratory fractionation associated with variation in substrate availability. We found that nighttime decreasing in δ13CR_leaf value is controlled by substrate availability associated changes in respiratory apparent fractionation but not δ13C of primary respiratory substrates; however, diurnal variation in Prosopis velutinaδ13CR_root is likely influenced by both changes in δ13C of primary respiratory substrates and variation in respiratory apparent fractionation. These findings are important for incorporating short term variation in δ13CR_leaf and δ13CR_root into the interpreting of δ13C value of ecosystem-atmosphere CO2 exchange and partitioning of net ecosystem CO2 exchange into its components.

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