Gas exchange of field-grown Pinus radiata - Relationships with foliar nutrition and water potential, and with climatic variables

Gas exchange measurements were conducted on Pinus radiata to investigate relationships between these and leaf-air vapour pressure deficit, photosynthetic photon flux density, and foliar temperature, water potential and nutrition in the field. Multiple non-linear regressions indicated strong relationships between gas exchange and foliar [P] (but of no other nutrient), leaf-air vapour pressure deficit, photosynthetic photon flux density, foliar water potential and temperature. The final regression produced for relationships between gas exchange and these variables explained 81% of the variance in the data. Micro-climate and foliar data from another site were used to predict gas exchange using the regressions and calculated parameters. Good agreement was obtained between the predicted values and carbon assimilation measured at that site. The relationship was poorer for leaf conductance.