Viabilidade técnica e econômica da poda em plantações de Pinus Taeda e Pinus Elliottii
Cardoso, Denise Jeton
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Pinus taeda - Poda
Pinus elliottii - Poda
Brazil first began concerning about producing pine clearwood 30 years ago, even though it has been quite a common activity in other countries for several years. The wood originated from the first pruned pine plantations began to be harvested in recent years. However, the procedures used in the pruning operation vary from region to region, as well as the thinning regime and quality of the site, which directly affect the growth of the trees and the amount of knot-free wood produced at the end of the rotation. The expected price for this product is equal to or greater than 100% of the wood value for the same grade, without pruning. However, due to the increasing production of composition boards and other changes taking place in the market, clearwood prices have been decreasing, coming close to the prices of unpruned wood. One of the objectives of this study was to quantify the clearwood volumes effectively and potentially generated from pruned logs. Another objective was to establish the minimum price to be charged for the pruned wood so that the same economic result from an unpruned stand could be achieved, considering the costs of pruning and yield in commercial volume in each situation. Yet, the maximum price to be asked for was calculated in order to make it an advantage to buy pruned logs rather than buying clearwood veneer in the market. The cost of pruning only the first log and pruning the first two logs of each tree was considered. The data were taken from eight stands located in the regions of Jaguariaíva, Sengés and Ibaiti, all in Paraná State, and the region of Itapeva, in São Paulo State. The ages of the plantations range between 18 and 24 years old, seven stands being of Pinus taeda and one of Pinus elliottii. The log batches were processed in veneer companies located in Sengés and Ibaiti. The log processing was efficient, for it was possible to measure the diameter of the knotty core as the first knot was shown. The results show that on average 52.9 % of the volume of the batch from the first logs corresponds to the volume of potentially clearwood against 50.1 %, obtained in the batches containing second logs. However, 10.8 % of the volume of these logs was turned into clearwood veneer, whereas in the batches from unpruned stands, this percentage did not exceed 2.3 %. It was observed that the second log has a better shape than the first, both in pruned and unpruned batches, although the volume of the second log is smaller. The pruned trees have a better shape than the unpruned trees and they achieved, on average, 6.5 % more volume than the latter, for the same dbh (diameter at breast height) and height. Regarding the price, the pruned logs must have, in relation to the value of the same grade unpruned, a minimal additional of 53.9 %, so as the same economic result from an unpruned stand and a maximum additional of 77 % can be achieved, so that the buyer might prefer to purchase these logs instead of purchasing the veneers. It is recommended that pruning be performed only on the first log, preferably in very productive sites, due to the uncertainty about the demand for clearwood. Performing pruning on the second log is considered important to make up for the small amount of clearwood in stands of low and medium productivity.
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