EFFECT OF SITE AND GROWTH ATTRIBUTES ON LOG END-SPLITTING OF EUCALYPTUS PELLITA GROWN IN NORTHERN BORNEO AND ITS REMEDIAL MEASURES

Eucalyptus pellita is currently the predominant tree species deployed for tree plantation establishment in many parts of Borneo, particularly in the state of Sabah, Malaysia. This study evaluates the occurrence of end-splitting in four-year old plantation grown E. pellita in Sabah as affected by site and growth attributes. An existing progeny tree breeding trial, involving seeds originated from Papua New Guinea, China, Vietnam, Australia and Sabah with 101 individual families, was used to carry out the split assessment. The trial trees were planted on two contrasting sites which differed significantly in soil type, soil texture, soil physical conditions, effective rooting depth and drainage capacity. Logs from the second thinning were cut into 2.2 m long sections. The end splits were evaluated by using a designated split scoring system. Plastic s-hooks, a wax emulsion end sealer and a bitumen end sealer were used as remediation measure and were compared against a control of no remedial application. The study showed that significant variation exists in log end-splitting, comparing the two sites, in combination with significant variation in tree growth. The variation in log end-splitting is attributed to the variation in tree growth as a response to the different growing conditions. Application of plastic s-hooks reduced split occurrence and severity significantly (49.62%), while the wax and bitumen end sealers had no effect on reduction of growth strain related splits. The findings suggested that end-splitting is caused by complex genetic-environment/site-growth interactions. It is vital to better understand factors involved in log end-splitting to optimise E. pellita plantation management.