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Loblolly pine is widely planted in southern Brazil. Despite its major relevance for the forestry sector, knowledge about its radial growth at different height levels is scarce—it is unprecedented for trees subjected to crown thinning. The following questions were answered: (1) how many competitors should be removed to favour the radial growth of potential crop trees? and (2) how long does it take to detect enhanced growth rates along the stem and how long do the effects last? The research design included four thinning treatments where competitor trees were removed in different intensities starting at age 5 years. At age 30 years, 20 trees from each thinning treatment were selected, of which cross-sectional discs were taken at 1.3 m, 25, 50 and 75% of commercial height. The removal of one competitor tree per potential crop tree is not sufficient to increase radial growth immediately after thinning—two competitors need to be removed. Growth responses were detected immediately at the tree base (1.3 m), but took ~ 3 and ~ 8 years to be detectable at 25% (~ 8 m) and 50% (~ 15 m) of commercial height. Positive influences on growth rate following thinning take longer to be detectable upwards in the stem than at the trees base. However, once present, enhanced growth rates last longer at higher levels than at the tree base. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The search for greater productivities, shorter production cycles and thus higher economic performances have led companies and landowners on the Highlands of Southern Brazil to invest in Eucalyptus plantations rather than Pinus. Determining the productivity and economic performance of forest stands is a key factor for their planning and management. In this context, the present study was carried out aiming to evaluate de growth and economic performance of Eucalyptus dunnii in different sites on the Highlands of Southern Brazil. Data from continuous forest inventory were regarded with a total of128 sample plots and 10.903 dbh x hdom paired values. Three site classes were obtained with dominant heights at index age of 10 years as the following: Class I: 34 to 39 m; Class II: 29 to 33,9 m; Class III: 24 to 28,9 m. Stands of d200 of 30 cm can be obtained since the age of 9 years-old on sites of high productivity, while it takes from 3 to 5 years on sites of lower productivity. The internal rate of return (IRR) on sites of high productivity is twice as high as the ones verified on sites with lower productivity. Net present values (NPV) and land expectation values (LEV) on sites of high productivity are 14 times higher than the ones observed on the worst sites. It was concluded that it is not only more profitable to grow E. dunnii on sites of high productivity, but also that there might be no viability at all of its cultivation on low productivity sites. [ABSTRACT FROM AUTHOR]