O eucalipto é um gênero amplamente cultivado no Brasil desde o início do século XX. É utilizado principalmente na produção de carvão e polpa, apesar da aptidão para produção de toras para serraria. Para as espécies cultivadas no Brasil, as técnicas de manejo para serraria foram pouco desenvolvidas e delas depende a introdução efetiva da madeira serrada de eucalipto no mercado. O presente estudo objetivou identificar as variáveis do manejo florestal do Eucalyptus urophylla que determinam, física e temporalmente, a formação de madeira limpa (clear) em árvores manejadas para serraria. O experimento foi implantado em julho de 2013 na Estação Experimental de Ciências Florestais de Itatinga (E.E.C.F.I/ESALQ/USP) e consistiu de 4 espaçamentos, sendo eles (3 x 1), (3 x 2), (3 x 3) e (6 x 1,5) m. Realizou-se o primeiro inventário em janeiro de 2015, aos 18 meses de idade, com medições de atributos das árvores e dos galhos. As parcelas foram subdivididas pela metade e, também em janeiro de 2015, aplicou-se a desrama artificial (poda) até os 2,5 m do tronco em uma de cada par de subparcelas. Daí em diante foram realizadas medições de cicatrizes e incremento secundário (dendrômetros) tomadas periodicamente até fevereiro de 2016, aos 31 meses de idade. Em junho de 2015 foi feita a primeira amostragem destrutiva de toras para medição de espessura da casca e em fevereiro de 2016 uma segunda leva de toras foi amostrada e submetida a análise em laboratório. Esta amostragem não incluiu o tratamento sem poda devido à ausência de desrama natural. Toretes foram gradualmente processados em torno mecânico para observação em plano tangencial da madeira formada após a desrama artificial. Nesta etapa também mediu-se a espessura da zona de oclusão e de madeira clear. A zona de oclusão é essencialmente composta pelo exsudado secretado para proteção periférica da cicatriz na casca. A área calculada do anel de oclusão está altamente correlacionada à área do anel da casca. Portanto, a espessura da casca determina a espessura do anel de oclusão e a formação de clear se inicia quando o xilema secundário sobrepõe o ponto mais externo no plano tangencial marcado pelo exsudado. / Eucalyptus is a genus widely grown in Brazil since the beginning of the 20th century, traditionally used to produce fuel and pulp despite its potential for sawlog production. The silvicultural techniques developed for eucalyptus short rotation woody crops in Brazil have neglected essential traits for high quality sawlog production, without which eucalyptus solid wood is not marketable. The aim of the present study was to identify the variables in silvicultural management of Eucalyptus urophylla limiting, physical and temporally, clear wood formation. The experiment was established in July 2013 at the Itatinga Experimental Station, College of Agriculture \"Luiz de Queiroz\" (ESALQ), University of São Paulo (USP), Brazil, consisting of spacing trials of (3 x 1), (3 x 2), (3 x 3) e (6 x 1,5) m. Measurements o trees and branches attributes were first taken in January 2015, when trees were 18 months old. The plots were split in half (subdivided) and one of the subplots was addressed for a pruning trial in which all live and dead branches were removed to 2,5 m, also in January 2015From then on, wound occlusion and secondary growth (band dendrometers) were periodically measured until February 2016, when the trees were 31 months old. Destructive samplings were firstly carried out in June 2015, for bark thickness determination, and secondly in February 2016. The latter did not include unpruned subplots, once the trees had not yet shed the branches. Logs were debarked and processed in mechanical lathe while measurements of clear wood and occlusion zone were taken in the tangential plane. High correlation between occlusion zone ring area and bark ring area has been found. The occlusion zone of Eucalyptus urophylla is mainly composed by the exudate released by trees during the bark wound closure process. Therefore, the bark thickness establishes the occlusion ring thickness and clear wood formation starts after the secondary xylem overlaps the most external point in the tangential plane marked by the exudate.

O eucalipto é um gênero amplamente cultivado no Brasil desde o início do século XX. É utilizado principalmente na produção de carvão e polpa, apesar da aptidão para produção de toras para serraria. Para as espécies cultivadas no Brasil, as técnicas de manejo para serraria foram pouco desenvolvidas e delas depende a introdução efetiva da madeira serrada de eucalipto no mercado. O presente estudo objetivou identificar as variáveis do manejo florestal do Eucalyptus urophylla que determinam, física e temporalmente, a formação de madeira limpa (clear) em árvores manejadas para serraria. O experimento foi implantado em julho de 2013 na Estação Experimental de Ciências Florestais de Itatinga (E.E.C.F.I/ESALQ/USP) e consistiu de 4 espaçamentos, sendo eles (3 x 1), (3 x 2), (3 x 3) e (6 x 1,5) m. Realizou-se o primeiro inventário em janeiro de 2015, aos 18 meses de idade, com medições de atributos das árvores e dos galhos. As parcelas foram subdivididas pela metade e, também em janeiro de 2015, aplicou-se a desrama artificial (poda) até os 2,5 m do tronco em uma de cada par de subparcelas. Daí em diante foram realizadas medições de cicatrizes e incremento secundário (dendrômetros) tomadas periodicamente até fevereiro de 2016, aos 31 meses de idade. Em junho de 2015 foi feita a primeira amostragem destrutiva de toras para medição de espessura da casca e em fevereiro de 2016 uma segunda leva de toras foi amostrada e submetida a análise em laboratório. Esta amostragem não incluiu o tratamento sem poda devido à ausência de desrama natural. Toretes foram gradualmente processados em torno mecânico para observação em plano tangencial da madeira formada após a desrama artificial. Nesta etapa também mediu-se a espessura da zona de oclusão e de madeira clear. A zona de oclusão é essencialmente composta pelo exsudado secretado para proteção periférica da cicatriz na casca. A área calculada do anel de oclusão está altamente correlacionada à área do anel da casca. Portanto, a espessura da casca determina a espessura do anel de oclusão e a formação de clear se inicia quando o xilema secundário sobrepõe o ponto mais externo no plano tangencial marcado pelo exsudado. / Eucalyptus is a genus widely grown in Brazil since the beginning of the 20th century, traditionally used to produce fuel and pulp despite its potential for sawlog production. The silvicultural techniques developed for eucalyptus short rotation woody crops in Brazil have neglected essential traits for high quality sawlog production, without which eucalyptus solid wood is not marketable. The aim of the present study was to identify the variables in silvicultural management of Eucalyptus urophylla limiting, physical and temporally, clear wood formation. The experiment was established in July 2013 at the Itatinga Experimental Station, College of Agriculture \"Luiz de Queiroz\" (ESALQ), University of São Paulo (USP), Brazil, consisting of spacing trials of (3 x 1), (3 x 2), (3 x 3) e (6 x 1,5) m. Measurements o trees and branches attributes were first taken in January 2015, when trees were 18 months old. The plots were split in half (subdivided) and one of the subplots was addressed for a pruning trial in which all live and dead branches were removed to 2,5 m, also in January 2015From then on, wound occlusion and secondary growth (band dendrometers) were periodically measured until February 2016, when the trees were 31 months old. Destructive samplings were firstly carried out in June 2015, for bark thickness determination, and secondly in February 2016. The latter did not include unpruned subplots, once the trees had not yet shed the branches. Logs were debarked and processed in mechanical lathe while measurements of clear wood and occlusion zone were taken in the tangential plane. High correlation between occlusion zone ring area and bark ring area has been found. The occlusion zone of Eucalyptus urophylla is mainly composed by the exudate released by trees during the bark wound closure process. Therefore, the bark thickness establishes the occlusion ring thickness and clear wood formation starts after the secondary xylem overlaps the most external point in the tangential plane marked by the exudate.

Thesis (MScFor (Forest and Wood Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The objective of this study was to develop and assess a methodology of using pruning information (age and height) and ring width measurements on increment core samples taken at breast height from standing pruned Pinus patula trees for modeling the knotty core sizes in the pruned section of a tree. A total of 170 trees from 17 compartments, representing a wide variety of growth sites from the Mpumalanga escarpment, were selected and destructively sampled. Sample trees were selected to represent the productive timber volume available from the compartments using stratified sampling. Sample discs were removed at breast height (1.3m) and at six meter height. After drying and sanding, the cross-sectional surfaces of one surface of each of the discs were scanned on a document scanner and the ring widths measured, using an image analysis program. A preliminary study, using 30 discs, was undertaken to ascertain the appropriate number of radii per disc to measure. A comparison between results of two opposite radii, as opposed to four radii, showed that the difference in mean ring width resulting from the two approaches was statistically not significant. In practice this means that for ring width assessment, sampling of increment cores opposite to one another at breast height would be sufficiently accurate to study average ring width variation across the radius of a tree. A study was also conducted to determine to what accuracy ring widths at six metre height could be predicted from breast height measurements. It was shown that cumulative growth at six metre height can be predicted from cumulative growth at breast height, site index and cambial age at breast height as independent variables (R2 = 0.96). Ring width measurements at breast height can, therefore, be used to predict incremental growth throughout the pruned section. Combined with available information on the pruning history of a stand (pruning heights and pruning age), this study proved that quantitative knowledge on incremental growth can be used as a basis for estimating changes in knotty core sizes along the entire pruned section of the stem. Analysis of variation for the entire data set from ring width measurements showed that there was far greater variation in knotty core percentages (the percentage of diameter occupied by knotty core) between different compartments than within compartments. Within a tree, the knotty core percentages between three stem sections, 0-2.4m, 2.4–4.8m, and 4.8-7m, were found to increase significantly from the bottom section (49.1%) to the top section (65.4%). A single 2.4m log from the pruned section of each tree was removed and processed into sawn timber at a sawmill. After drying of the boards, a sub-sample of sawn boards from 17 logs, one log from each compartment, was selected and reconstructed into log form. From the reconstructed log (reconstructed to represent their original position in the log) the actual knotty core size was estimated by measuring the distance from the pith to the end of the branch stub. A comparison of the actual knotty core sizes and the modelled knotty core sizes of a sub-sample of trees showed only a modest relationship (R2 = 0.62). Reasons for this might be variability in pruning quality, inaccurate pruning records, nodal swellings and the methodology used to measure the actual knotty core sizes. Knowledge of knotty core sizes of standing trees can be used for many different purposes. Two applications that were assessed and found to be useful include decision support for cross cutting logs and for sawmill production planning purposes. Sawmill simulation software was used to evaluate value -and grade recoveries under different scenarios. Results showed that cross-cutting the pruned sections of logs from a compartment with large within-tree knotty core size variation into shorter logs, as opposed to keeping the pruned sections as single logs, result in increases in grade and value recovery. It was also shown that sawing of pruned logs from compartments with relatively small knotty cores, results in much better grade recoveries than logs from compartments with relatively large knotty cores (this information will be useful for production planning purposes). It can be concluded that the methodology proposed to reconstruct knotty cores from tree ring measurements has the potential to be used as a decision aid in the forest and forest products industry.