The extent and causes of decline in productivity from first to second rotation blue gum plantations
This project quantified changes in productivity of blue gum plantations between the first and second rotation, particularly in Western Australia. The research showed that well established forestry management principles, such as soil and nutrition management, can sustain production through multiple rotations.
The research developed predictive modelling that fits easily into existing company inventory systems. Empirical growth curves were constructed that calculated second rotation site index, basal area and volume as a function of a standardised precipitation evaporation index and, where first rotation site index is known, to develop growth for the second rotation.
The research also modelled the processes driving the decline in production observed in the small sample set of plots. Some of the observed decline was due to variation in rainfall and soil water between rotations. For each millimetre of soil water lost in the 2nd rotation, there is a corresponding loss in wood production of approximately 0.015 cubic metres per hectare. In the worst case this will result in a 8–10% decrease in production
On sites where 1R site fertility was low, soil nutrition is likely to limit productivity in 2nd (and subsequent) rotations.