Optimum pruning intensity in Eucalytpus dunnii for clear wood producing.

Abstract

Eucalyptus dunnii is a subtropical species, indicated for areas where frosts occur. Besides its current utilization for paper, coal and boards production, the potential for nobler solid-uses are recognized, provided that silvicultural practices such as pruning and thinning are regarded. The objective of this study was to analyze the growth of dominant E. dunnii trees subjected to four different pruning intensities: 100, 80, 50 and 20% of the total tree height of remained canopy. Experimental design was fully randomized, with 10 replications per treatment. After 20 months of pruning, maintaining 50% of canopy was sufficient to allow a normal diameter growth. More important than the proportion, was the absolute length of remained canopy. It was concluded that it is necessary to keep, at least, 4 m of remained canopy in order to maintain a periodic annual increment over 4 cm (average during the 17-37 months period). When this threshold is exceeded, lost in the order of 50% in diameter increment are expected.