Abstract
In the present work a thinning program and a model describing dynamic of crown base recession for Eucalyptus grandis was established on an individual tree basis. Therefore, 485 trees were measured on temporary plots in forests of the companies Klabin Riocell (Guaíba), Todeschini (Cachoeira do Sul), the Federal University of Santa Maria and Aracruz Company, located in Rio Grande do Sul, Espirito Santo and Bahia, Brazil. A straight relationship between crown width and diameter at breast height (DBH) was found by using regression analysis. The equation obtained was crown width = e0.504+0.0307* DBH, with a coefficient of determination of 0.78 and a standard error of 0.034. With this equation the standing space of the individual trees was calculated over the whole rotation period, taking into account a crown cover of 70 %. Therefore the number of trees which can be grown on a hectare was derived for different variants of management systems aiming to produce eucalypt sawlogs in short rotation periods. Beside this a multivariate model describing height of crown base as a function of DBH and total height was found. Based upon this model the dynamics of crown base recession for different site qualities and thinning regimes are described, giving advice for time and intensity of green pruning.
Highlights
Plantation forestry is a very important part of the Brazilian forestry sector
Regression analysis with crown width as dependent variable and diameter at breast height as independent variable showed that crown width significantly increases with increasing diameter at breast height, but it was found increasing variance of the crown width for higher dbh-values, which indicated heteroscedasticity
Site index model for estimating maximum radial increment According to the model established diameter growth can be controlled by crown expansion, which is a function of competition regulation
Summary
Plantation forestry is a very important part of the Brazilian forestry sector. Representing only 1.3 % of the total forest area of the country, it contributes to more than 60% of the wood production. From 7 million ha of plantation forests existing in Brazil, almost 5 million ha are considered as industrial plantations with the aim of producing pulpwood, mainly from the genus Eucalyptus, with approximately 3 million ha, and Pinus (BROWN, 1997). Depending on site quality a second fertilizing is conducted at the age of 3 to 4 years. For the cellulose production in general no thinnings are necessary, harvesting age varies between 5, 7 and on poorer sites about 10 years. At this age the trees show up heights of 26 to 35 m and stand densities of 1000 trees/ha can be observed
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