Southern WA nature inspiration thread

[shibui]

The process of Australian tree hollows developing is still not well understood.
A lot of tree hollows start out with insects - termites, wood boring beetles and others - as they consume the central heartwood of trees. Fungi and other decay processes may also contribute to initial formation but probably play a bigger part in enlarging the initial smaller holes in the centre of the trees.
Wind, breaking branches, may contribute - allowing access to the tree's heartwood for insects, fungi and other wood decaying organisms. Physical damage lower on the trunk can also allow access to the heartwood. Physical damage can be from animals chewing or scratching, other trees falling onto the trunk and human damage.
Over time the smaller holes inside the trunk and branches are slowly enlarged by various combinations of the above. Trees continue to grow and thicken even while the hollows inside get larger. Often the hollow trunk is not even visible from the outside. Quite a few Australian trees are know no wood workers and timber workers as useless because such a high proportion of the trunks are 'pipes'

As hollow branches and trunks become weaker they are more likely to break when it is windy, thus exposing the hollow cores. Exposed hollows are so common in Australian species that many of our native birds and animals use them for nesting and shelter. Many of those animals are so adapted to hollows they cannot live without hollows.
When hollow trunks and branches are exposed to outside factors, fire can then play a part. Fire is a 2 edged sword for hollow trees. It can enlarge hollows but it can also destroy hollow trees by further weakening their structure. Hollow trees act as a chimney drawing air in at openings down low and out at the top. Seeing hollow trees burn on a fireground is spectacular, especially at night when it becomes a fountain of flames and embers.

It is estimated that hollows take many years to form. The smallest hollows take decades to develop. It takes centuries for larger hollows like the tree shown above.