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Variation in the carbon and oxygen isotope composition of plant biomass and its relationship to water‐use efficiency at the leaf‐ and ecosystem‐scales in a northern G reat P lains grassland
Author(s) -
FLANAGAN LAWRENCE B.,
FARQUHAR GRAHAM D.
Publication year - 2014
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/pce.12165
Subject(s) - biomass (ecology) , carbon fibers , oxygen , composition (language) , isotopes of oxygen , ecosystem , stable isotope ratio , isotopes of carbon , chemistry , environmental chemistry , isotope , environmental science , ecology , total organic carbon , biology , mathematics , nuclear chemistry , physics , organic chemistry , algorithm , quantum mechanics , composite number , linguistics , philosophy
Measurements of the carbon (δ 13 C m ) and oxygen (δ 18 O m ) isotope composition of C 3 plant tissue provide important insights into controls on water‐use efficiency. We investigated the causes of seasonal and inter‐annual variability in water‐use efficiency in a grassland near L ethbridge, C anada using stable isotope (leaf‐scale) and eddy covariance measurements (ecosystem‐scale). The positive relationship between δ 13 C m and δ 18 O m values for samples collected during 1998–2001 indicated that variation in stomatal conductance and water stress‐induced changes in the degree of stomatal limitation of net photosynthesis were the major controls on variation in δ 13 C m and biomass production during this time. By comparison, the lack of a significant relationship between δ 13 C m and δ 18 O m values during 2002, 2003 and 2006 demonstrated that water stress was not a significant limitation on photosynthesis and biomass production in these years. Water‐use efficiency was higher in 2000 than 1999, consistent with expectations because of greater stomatal limitation of photosynthesis and lower leaf c i /ca during the drier conditions of 2000. Calculated values of leaf‐scale water‐use efficiency were 2–3 times higher than ecosystem‐scale water‐use efficiency, a difference that was likely due to carbon lost in root respiration and water lost during soil evaporation that was not accounted for by the stable isotope measurements.