
TY  - JOUR
A1  - Walcroft, A. S. 
A1  - Silvester, W. B. 
A1  - Whitehead, D. 
A1  - Kelliher, F. M. 
T1  - Seasonal Changes in Stable Carbon Isotope Ratios within Annual Rings of <emph type="2">Pinus radiata</emph> Reflect Environmental Regulation of Growth Processes
JF  - Functional Plant Biology
JO  - Functional Plant Biol.
Y1  - 1997
VL  - 24
IS  - 1
SP  - 57
EP  - 68
KW  - 
UR  - https://doi.org/10.1071/PP96025 
N2  - Seasonal cycles in stable carbon isotope composition (&#948;13C) were measured within annual rings of Pinus radiata D. Don from trees in two plantation sites which differ markedly in annual water balance. The amplitudes of seasonal &#948;13C variation at the wet and dry sites were 1&#8211;2 and 4 respectively. Mean &#948;13C values from the wet site were 3 more 13C depleted than those from the dry site implying lower water-use efficiency (carbon assimilation per unit transpiration). A process-based, leaf-level model of stomatal conductance and CO2 assimilation was combined with a water balance model to estimate the average daily intercellular CO2 concentration (ci). Over two growing seasons at each site there was generally good agreement between mean canopy-level ci derived from the tree-ring &#948;13C data and modelled leaf-level ci levels. Further, the ratio of annual CO2 assimilation to transpiration estimated by the model for each site correlated with the differences in water-use efficiency between the sites. Carbon isotope discrimination of leaves in the canopy was thus reflected directly in the stem wood, and its dynamic variation within a site, as well as between sites, was driven principally by the interaction of seasonally changing micrometeorological variables and soil water availability. 
ER  -

