Manejo florestal em faixas alternadas para floresta ombrófila aberta no município de Codó, Estado do Maranhão

Abstract

This study was carried out at the forest management area of the Magela Project in the Municipality of Codó-MA (04º 35’ 20" S and 43º 49’ 55,2" W), owned by the MARGUSA (Maranhão Gusa S/A) enterprise. The objectives were to adjust a volumetric model to estimate, simultaneously, the bole volume and the total volume of individual trees; analyze the floristic composition, horizontal structure and diametric distributions, basal area and the total volume of the forest; and to carry out a technical and financial analysis comparing both forest management systems in alternate strips and the selective system. There were measured 364 tree-sample with diameters ranging from 2,5 cm to 90 cm. The Schumacher and Hall model was tested with one binary variable to estimate the bole and total volumes with or without holes; and the total volume of Cenostigma macrophyllum Tul (Leguminosae). A total of 21 randomized plots of 50 m x 200 m were established, with twelve plots in Open Ombrophylus Forest with Liana (OOFliana) and nine plots in Open Ombrophylus Forest with Palm (OOFpalm). All individuals with dbh = 15 cm (inclusion level I) were measured. Individuals with 5 cm = dbh < 15 cm (inclusion level II) were measured in 5 m x 50 m subplots. Quantitative data of the remaining forest structure and the technical forest management coefficient estimates were taken through a forest inventory carried out in six 50 m x 200 m permanent plots after harvesting; in each permanent plot trees and palms with dbh = 5 cm were measured. Results showed that the equations from the regression model adjustment can be used, with good precision, for estimating the bole and total volumes in Open Ombrophylus Forest. OOFpalm showed the higher floristic diversity, best forest structure quality and the lesser productivity capacity than OOFliana. The most ecological important species in OOFliana were: Cenostigma macrophyllum, Galipea jasminiflora Encley (Rutaceae), Hymenaea parviflora Huber (Leguminosae) e Duguetia cadavérica Huber (Annonaceae). While in OOFpalm, the most important species were: Orbignya speciosa (Mart.) Bard. Rodr. (Arecaceae), Actinostemon klotzchii (Didr.) Pax (Euphorbiaceae), Cenostigma macrophyllum e Hymenaea parviflora Huber (Leguminosae). The indicator species of OOFliana and OOFpalm were, respectfully, Cenostigma macrophyllum and Orbignya speciosa. Both phytocenosis presented good potential for sustainable production of wood to energy. Results of liquid present value for infinite horizon, soil expect value, equivalent annual value, benefit/cost ratio, internal rate of return and mean production cost showed that: the MAFA system had a higher environmental viability; the harvesting operational income (felling and bucking) was higher in the MAFA system; both forest management systems have financial viability, being SS system the best economic alternative; charcoal produced from sustainable forest management systems can compete with charcoal obtained in common market.