Análise quantitativa e qualitativa do crescimento de caixeta – Tabebuia cassinoides (Lam.) DC. – em florestas manejadas, no município de Iguape/SP

Abstract

Caixeta – Tabebuia cassinoides (LAM.) DC. – is a tree species of swamp forests in the Atlantic Rain Forest. It has been used since the 30’s, mainly for clog and pencil production. IBAMA Decree no. 218 prohibited Caixeta’s explotation in 1989. By its importance for the community and social movement, caixeta’s management was regulated by the Resolution 11/92 by the Environmental Secretary of São Paulo State. This Resolution regulates caixeta management by auto-sustained regime. The cutting cycle was defined as 12 years, but isn’t based on technical and scientific data. Information about growth and yield are rare for Tropical Rain Forest. This information is essential to verify technical, environmental and economic sustainability of the forest management. Thus, check the proposed cutting cycle is fundamental to certify the sustainability of caixeta management. After harvest caixeta sprouts vigorously, so one the most important silvicultural practice is sprout thinning. Resolution ES 11/92, establishes that must be left 1 to 3 sprouts per stump. Objectifying to verify growth and stem quality of the sprouts was established an experimental area composed by 224 stumps. By the Forest Inventory measurement of Retiro Farm (50 samples 10 x 20 m) and Cindumel Farm (46 samples 10 x 20 m), was observed Mean Annual Increment for volume of 3,215 ± 0,366 m /ha/year and 5,557 ± 0,598 m /ha/year, respectively. The harvest intensity was over 50% of the amount harvestable wood; the intensity was higher near the extraction routes, reaching 94%. Thus caused a reduction of 54% in MAI, where the harvest intensity was higher than 75%. The estimated harvest cycle for managed caixetais has Confident Interval from 12,9 to 17,6 years. T he measurement of thinning sprout experiment, 8 years after logging, indicates that treatments that have 1 and 2 sprouts are statistically equal, and have mean DBH of 8,95 cm and 8,37 cm, respectively. While the treatments that have 3 and all sprouts have mean DBH of 7,30 cm and 5,37 cm, respectively, for the same period. Sprout thinning improves stem quality, increasing the height of first fork and reducing stem sinuosity, when compared with sprouts without thinning. The research results pointed to the need of Resolution 11 review, searching for the sustainability of caixeta management. The points that must be reviewed, are: (i) establishment of a limit of harvest intensity lesser than 75%, nearby the extraction routes; (ii) the number of the sprouts per s tump must be 1 or 2, and; (iii) the harvest cycle of 12 years is underestimated.