Farm Forestry New ZealandSpatial distribution of cell collapse in Eucalyptus nitens wood due to drying treatment
By Alan Dickson and Rosie Sargent, June 2021.
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Executive summary
This work is part of a broader approach to characterising and understanding the mechanisms of cell collapse and within-ring checking in hardwoods during drying. Understanding the causes of such timber degrade gives us options for dealing with it in the future, such as identifying collapse-prone timber prior to drying, or developing drying methods that avoid the conditions that cause checking and collapse.
In this microscopy approach we characterise and measure collapse and checking responses, and spatial relationships, at a cellular level but can do this over a size scale closer to which they occur and are an issue during timber processing. A conventional, stereo light microscope was used to image polished wood surfaces. This was done at cellular resolution, over size-scales of the growth-ring or larger.
An image analysis approach was developed that enabled cell collapse to be identified, located and measured. The analysis of air, kiln, and oven-dried Eucalyptus nitens showed that cell collapse was highly variable but generally more prominent in the outer third of growth rings. There were significant changes in vessel shape across the growth-rings and vessel area was significantly reduced by drying.
The technique provides an intermediate step between detailed microscopy and macroscopic imaging that allows spatial analysis at the wood cell level. The result is the detailed imaging and analysis of cell collapse and its relationships to wood morphology and the major hydraulic pathways. This will allow for the investigation of cell collapse and checking mechanisms and how they related to the broader growth ring and wood morphology and structure.
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