Growth response following green crown pruning in plantation-grown Eucalyptus pilularis and Eucalyptus cloeziana

摘要

Pruning of live branches is performed to enhance wood quality in plantation trees. Stem, branch and wood propertiesnmay be altered following pruning from below, but the extent and duration of such effects are unknown for manynplantation Eucalyptus species. The effect of 0%, 20%, 50%, and 70% green crown length removal on growth and woodnquality was examined in 3.5-year-old plantation-grown Eucalyptus pilularis Sm. (blackbutt) and Eucalyptus cloeziana F.nMuell. (Gympie messmate) trees on two subtropical sites in eastern Australia. Growth increment of the stem at breastnheight was not affected by 20% crown removal. However, stem increment at breast height was reduced for up to 8 monthsnwith 50% crown removal and up to 12 months with 70% crown removal. Pruning had no impact on height growth. However,nthe height of trees pruned to 70%, relative to the height of the surrounding unpruned trees, was temporarily reducedn12 months after pruning in both species. Stem form, stem taper, wood density, and residual branch growth above thenpruned zone were unaffected by pruning. Owing to the fast vertical crown expansion, trees were able to rapidly compensatenfor leaf area removal without long-term reductions in stem growth. The implications for management operations utilizingnpruning as a means of enhancing timber quality are discussed.