
TY  - JOUR
A1  - Arneth, A. 
A1  - Kelliher, F.M. 
A1  - McSeveny, T.M. 
A1  - Byers, J.N. 
T1  - Fluxes of carbon and water in a <emph type="2">Pinus radiata</emph> forest subject to soil water deficit
JF  - Functional Plant Biology
JO  - Functional Plant Biol.
Y1  - 1998
VL  - 25
IS  - 5
SP  - 557
EP  - 570
KW  - 
UR  - https://doi.org/10.1071/PP97153 
N2  - We measured, by eddy covariance, seasonal CO2 (FCO2) and water (E) fluxes in an 8-year-old New Zealand Pinus radiata D.Don plantation subject to growing season soil water deficit. Average rates of FCO2 and E were highest in spring (324 mmol m-2 d-1 and 207 mol m-2 d-1, respectively) when the abiotic environment was most favourable for surface conductance and photosynthesis. During summer, fluxes were impeded by soil water (&#952;) deficit and were equal to or smaller than during winter (FCO2 = 46 mmol m-2 d-1 in summer and 115 mmol m-2 d-1 in winter; E = 57 and 47 mol m-2 d-1, respectively). On particularly hot and dry days, respiration exceeded photosynthetic uptake and the ecosystem was a net carbon source. Portraying the underlying biochemistry of photosynthesis, daytime half-hourly FCO2 increased with quantum irradiance absorbed by the canopy (Qabs) following a non-saturating, rectangular hyperbola. Except for winter, this relation was variable, including hysteresis attributable to diurnal variation in air saturation deficit (D). Daily ecosystem FCO2, FCO2/Qabs and FCO2/E were inversely proportional to maximum daily D, but in the cases of FCO2 and FCO2/Qabs only after soil moisture deficit became established. Consequently, as the tree growing season progressed, ecosystem carbon sequestration was strongly limited by the co-occurrence of high D at low &#952;. 
ER  -

