Changes in Pinus radiata stem form in response to nitrogen and phosphorus fertiliser

The change in tree form of Pinus radiata, D. Don after application of nitrogen and/or phosphorus fertiliser was examined through analysis of bark thickness, relative taper curves, and tree volume equations. Based on some 1300 sectionally measured trees, the results indicate that the application of phosphorus leads to thinner bark and a small improvement in form, while nitrogen alone results in a slight deterioration in form. A weak negative relation-ship between the change in form and the basal area response to fertiliser suggests that only when basal area response exceeds 35 % will average form improve by more than 2.5%