Branching out … what impact does tree spacing have on branch development?


New findings from Southern Cross University’s Forest Research Centre will help growers improve plantations by controlling branch size and quality.


At an experimental Eucalyptus pilularis plantation in subtropical eastern Australia, the researchers studied trees aged between 1.6 and 5.7 years.

Densities ranging between 816 and 1,667 trees per hectare were compared, while the rectangularities of tree spacing observed were in the range of one to six. Studying branches at the lowest five metres of the tree stems, because they were deemed most likely to yield high-quality sawn timber, researchers found neither density nor rectangularity had a substantial impact on the number of branches or their diameters.

The researchers were also on the look out for branches with diameters in excess of 2.5 cm, because branches of this size are likely to produce large knots that degrade the quality of sawn timber. In most cases, such branches were found to develop on lower stems aged between two and four years. However, an average of almost five such branches were found on the more widely spaced trees, compared to just two or three on trees grown closer together.

The results confirmed previous work suggesting pruning of high-quality eucalypt plantations should start at between two and three years of age, particularly where trees are more widely spaced. This will help limit the development of larger branches and restrict the size of problematic knotty cores.

Source: Australian Forestry