Research On Pruning Effects Of 3yrs. Corymbia Torelliana

A field trial of pruning on 3 years old Corymbia Torelliana was established in November 2008 in a plantation at South China Experimental Nursery in Suixi county, Zhanjiang city,Guangdong province. This trial had a randomized block design that included 3 replicates of 9 treatments. Each plot compromised 10 trees. Treatments included:4 pruning intensities pruning all branches up to stem diameters of 5.0,6.0,7.0 or 8.0 cm,2 methods of pruning-flush and stubble, and 2 methods of wound protection-wax or paint. Assessments were carried at various intervals during the span of 12 months on growth, wound occlusion and visual quality of peered veneer.(1) Growth results during the observation period showed:height growth was impeded; DBH growth was promoted; taper was decreased plumpness was increased; in the first 6 months after pruning, heavier pruning intensities lead to higher crown growth ratios but in second 6 months the opposite occurred; After 12 months the average individual tree volume of pruned trees was larger than that of unpruned trees, and the largest and smallest stand volumes were obtained with 8cm and 5cm pruning lifts respectively; Overall the worst pruning lift was 5cm and the best pruning lift was 8cm, and the best treatment and the worst treatment was "8cm+flush+wax" and "5cm+plush+paint" respectively.(2) Observations of wound occlusion results the 12 month period showed that the ranking of pruning lifts in order from highest to lowest occlusion ratios was 7 cm,8 cm and 5 cm; paint promoted wound occlusion better than did wax and the best wound occlusion was found to occur at stem height of between 2.00 and 5.35m; wound grade played a decisive role in wound occlusion with the occlusion of small wounds and large wounds occluding faster than others; tree growth condition, such as DBH and crown growth, also affected wound occlusion; Overall, the best treatments with respect to wound occlusion were "7cm+flush+wax" and "6cm+plush+paint" respectively. (4) Visual grades of peeled veneer obtained from 3 and 9 year old C. torelliana trees showed that quality was influenced most by dead knots, live knots, holes. Traits that had lesser influence included twist and groove.