An investigation into collapse and shrinkage behaviour of Eucalyptus grandis and Eucalyptus grandis-urophylla wood

In this study, the variation of collapse and shrinkage both radially and along the height of trees was investigated and their relationships with warp in the sawn boards as well as the basic physical properties of wood (density, moisture content, permeability, extractives contents and heartwood/sapwood ratio) were determined. Seventy trees of Eucalyptus grandis and Eucalyptus grandis-urophylla were selected based on age (young, medium and old) and genetics (improved and unimproved). Collapse and shrinkage were measured on both wedges and sawn boards. In terms of the causal factors in wedges, there were weak but significant correlations between collapse and extractives content, density, and permeability, while shrinkage showed stronger correlations with the same parameters. The results showed that on boards, collapse and shrinkage varied depending on group (age x genetics), log position and the radial position of the boards. The radial and tangential collapse measured on wedges did not correspond well with collapse observed in sawn board specimens. Future research should focus on understanding collapse in Eucalyptus grandis and Eucalyptus grandis-urophylla on an anatomical level including the clear directional nature as well as the influence that specimen geometry has on collapse.