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Crown thinning on Eucalyptus dunnii stands for saw- and veneer logs in southern Brazil

Dobner, Mário, Jr., Huss, Juergen
New forests 2019 v.50 no.3 pp. 361-375
Eucalyptus dunnii, Pinus taeda, case studies, forest management, highlands, plantations, pruning, trees, veneer logs, Brazil
Eucalypt plantations occupy > 5 million ha in the warm regions of Brazil. In the southern highlands, however, forestry is dominated by Pinus taeda. The frost-tolerant Eucalyptus dunnii Maiden seems to be suitable for that area, but there are few case studies and very little information about managing eucalypt stands for multiple uses. Thinning and pruning are key silvicultural management practices for E. dunnii plantations that produce saw- and veneer-logs. With this study it was aimed to evaluate the use of crown thinning to produce large-diameter trees in Eucalyptus dunnii stands. At age 2 years, 200 potential crop trees (pct) per ha were selected, pruned, and released from competition in five different intensities: no thinning, three practice-oriented variants, and one extreme and early thinning. Experimental data was collected until the stands were 13 years old. The production of large-diameter log assortments (≥ 40 cm) was positively associated with thinning and was strongly dependent on the site quality. Optimal results occurred with initial densities of 1000 trees ha⁻¹ associated with early and relatively aggressive thinning. However, the final selection of pct’s and their release from competitors should not take place before dominant trees can be efficiently recognized (h₁₀₀ = 15 m). Following these recommendations, at age of 13 years, the production of 100 m³ ha⁻¹ of big sized timber (> 40 cm) can be expected.