Manejo florestal : impactos ecologicos de diferentes niveis de remoção e os impactos de sua sustentabilidade

AUTOR(ES)
DATA DE PUBLICAÇÃO

2001

RESUMO

The objective ofthis study was to evaluate an experiment offorest management established in 1980 at the Reserva Natural da Vale do Rio Doce, and monitored during a period of 20 years. The forest was exploited according to various levels of basal area remotion, totaling 9 treatments, including the control, in which no interference was made and the clearcut, with 100% of basal area remotion. Silvicultural treatments such as thinning and releasing were not applied. With the clearcut, only a utilization of 27% of timber for sawmills was obtained, in relation to the estimated volume by volumetric equation, which indicates a low yield mainly due to internal defects that rarely are accounted for. The harvest gave a net profit of U$269 to 627 lha, in the less intensive treatment (treatment 2) and more intensive (treatment 7), respectively. The increment rates in diameter were greater in the first years after the silvicultural treatments were done, and decreased with the closing of the canopy and were greater in the more intensive treatments. The rate of annual periodic mean increment varied from 2.22 mm/year in the treatment 1 (without interference), to 3.07 mm/year in the treatment 7, during a period of 20 years. The phytosociologic structure of the forest, in relation to the species with greater VC, showed only a slight alteration. However, some pioneer species or even initial secondary ones can reach greater positions ofVC due to the light stimulus provided by the basal area remotion levels. The floristic composition varied naturally and more severely according to the intensity of the management. Processes of species disappearances within the plots occurred naturally in the treatment 1 (without interference) and in the treatments where interferences were made (treatments 2 to 9), but some ofthe species which were affected by harvest were not yet sampled with DBH greater of equal to 10 em. The diversity restoration was fast, considering the Shannon index, but the richness was restored a bit slower in the more intensive treatments. The restoration of density of individuaIs occurred rapidly but the basal area increase showed to be very slow. The diametric structure was a good indicator of the general restoration of the forest structure, showing that a great part of this was concentrated in the first diametric classes, while in the greater classes both the density reposition and the basal area increase were very slow. A light significant increase in the concentration of soil nutrients (P, Ca + Mg, K) was found after the harvest, except for Aluminum (AI) which decreased. AlI the treatments presented on increase and the statistic result showed that the interaction Time x Treatment is significant. The conservation of forest resources and forest management are not incompatible but if the impacts of the harvest are high, as occurred in alI treatments except in treatment 2, in this work, then the forest restoration process becomes very slow for wood sustainable harvests in cyc1es of 30 or 40 years. Besides, if desirable species are not favored, the volume of the forest at the end of 20 years wilI, in its greater part, inc1ude woods with lower economic value

ASSUNTO(S)

florestas - crescimento ecologia florestal

ACESSO AO ARTIGO

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