EUCALYPT DRYING and COLLAPSE

One of the challenges regularly encountered by eucalypt processors is defects which occur during drying. If eucalypt wood is to used for high-value solid wood products, it is crucial to understand defects such as cell collapse during drying.

A PhD project completed by Vikash Ghildiyal in 2023 investigated the genetic factors influencing drying collapse in two NZDFI eucalypt species:

• Genetic control: Heartwood collapse is under genetic control in both E. globoidea and E. quadrangulata with the heritability ranging from 0.19-0.44.
• Wood properties: Heartwood collapse was negatively correlated with basic density and positively correlated with extractive content.
• Heartwood vs sapwood: Sapwood showed less collapse than heartwood.

The findings suggest that collapse in this future eucalypt resource can be minimised through breeding, potentially eliminating the problem. This finding is of value to the NZDFI breeding programme, where future selections can incorporate resistance to drying defects.

More details of Vikash's research can be found in Project Update July - December 2023 and Project Update January - June 2022.

Vikash has produced four peer-reviewed publications:

• "Genetic variation in drying collapse and heartwood properties at mid-rotation age of Eucalyptus globoidea"
• "The effect of Joule heating on collapse and water absorption of wood"
• "Managing ion concentration in sap to control drying collapse, permeability, and streaming potential in plantation-grown eucalyptus timber"
• "Electrical Phenomena in Trees and Wood: A Review"

Vikash's 2023 PhD thesis is available here: 'Understanding and reducing drying collapse in difficult-to-dry plantation-grown eucalypt timber.