Towards a functional-structural model for macadamia (MC07021)

This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

The Department of Agriculture, Fisheries and Forestry (DAFF) initiated an internally funded project to develop expertise in functional-structural modelling of tropical and sub-tropical tree fruit crops. Macadamia was chosen as the model crop for these initial studies. The DAFF project used self-organising model to explore canopy management options. The amount of light available for growth was sensed at the leaf level and used to represent vigour, which was then accumulated acropetally. Buds also sensed the light environment but only to provide demand in subsequent redistribution.

Tree models were initiated by reading in an initial structure digitised from a small tree in the field and then allowed to develop (self-organising) for a number of years. Simulated cultural practices such as hedging, topping, removal of the leader and limb removal were investigated. The model provided insight into the impact of these practices on light distribution within the canopy and to the orchard floor. The lessons learnt from this will be applied to other evergreen, tropical fruit and nut trees.

The Australian Macadamia Society agreed fund, through Hort Innovation (which was then Horticulture Australia Limited), two part-scholarships for PhD studies to complement the DAFF macadamia modelling work. One study (by Sadegh Karimaei) focussed on vegetative growth and the influence of carbohydrate allocation on growth and tree architecture. The other study (by Janine Conway) focussed on axillary bud development and implications for reliability of flowering (and ultimately fruit development), an important yield-limiting factor.