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Spatial and temporal scaling of intercellular CO 2 concentration in a temperate rain forest dominated by Dacrydium cupressinum in New Zealand
Author(s) -
TISSUE DAVID T.,
BARBOUR MARGARET M.,
HUNT JOHN E.,
TURNBULL MATTHEW H.,
GRIFFIN KEVIN L.,
WALCROFT ADRIAN S.,
WHITEHEAD DAVID
Publication year - 2006
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/j.1365-3040.2005.01427.x
Subject(s) - canopy , atmospheric sciences , environmental science , ecosystem , eddy covariance , temperate forest , stomatal conductance , temperate rainforest , isotopes of carbon , forest ecology , carbon cycle , photosynthesis , botany , ecology , biology , total organic carbon , geology
Seven methods, including measurements of photosynthesis ( A ) and stomatal conductance ( g s ), carbon isotope discrimination, ecosystem CO 2 and water vapour exchange using eddy covariance and the use of a multilayer canopy model and ecosystem Keeling plots, were employed to derive estimates of intercellular CO 2 concentration ( C i ) across a range of spatial and temporal scales in a low productivity rain forest ecosystem dominated by the conifer Dacrydium cupressinum Lamb. in New Zealand. Estimates of shoot and canopy C i across temporal scales ranging from minutes to years were remarkably similar (range of 274–294 µ mol mol −1 ). The gradual increase in shoot C i with depth in the canopy was more likely attributable to decreases in A resulting from lower irradiance ( Q ) than to increases in g s due to changes in air saturation deficit ( D ). The lack of marked vertical gradients in A and g s at saturating Q through the canopy and the low seasonal variability in environmental conditions contributed to the efficacy of scaling C i . However, the canopy C i estimate calculated from the carbon isotope composition of respired ecosystem CO 2 ( δ 13 C R ; 236 µ mol mol −1 ) was much lower than other estimates of canopy C i . Partitioning δ 13 C R into four components (soil, roots, litter and foliage) indicated root respiration as the dominant (> 50%) contributor to δ 13 C R . Variable time lags and differences in isotopic composition during photosynthesis and respiration make the direct estimation of canopy C i from δ 13 C R problematic.