Resumo -Foi realizada a análise da viabilidade econômica de diferentes sistemas de produção de madeira de eucalipto (Eucalyptus grandis Hill ex. Maiden) em duas propriedades rurais, no Município de Alegrete, RS. A análise econômica considerou a comparação entre um sistema tradicional de pecuária da região e dois sistemas alternativos de conversão da área de pecuária para plantios homogêneos de eucalipto em duas densidades com 2.222 e 1.111 árvores.ha -1 e dois sistemas silvipastoris: com 1.000 e 500 árvores.ha -1 . A análise dos resultados foi realizada a partir da determinação da Taxa Interna de Retorno (TIR) e da sua comparação com a Taxa Mínima de Atratividade (TMA). As alternativas com e sem o valor da terra foram avaliadas considerando uma variação do preço (aumento e diminuição de 5%) e do volume da madeira (aumento e diminuição de 10%). Considerando o valor da terra, todas as alternativas analisadas apresentaram TIR inferior a TMA (3,72%). A análise de sensibilidade mostrou que, havendo aumento do preço e do volume de madeira, a maioria das alternativas com desbaste apresentou TIR superior a TMA, exceto a alternativa do sistema silvipastoril com 500 árvores.ha -1 . Dessa forma, a implantação do componente florestal na propriedade rural, quando não se considerou o valor da terra, apresentou-se economicamente viável para o produtor rural.Termos para indexação: Pecuária extensiva, produção florestal, sistema silvipastoril, avaliação econômica, Eucalyptus grandis. Silvopastoral Systems as a Support for Rural Development in the Southwest Region of Rio Grande do Sul State, BrazilAbstract -An economic viability analysis was performed for different eucalypt wood production systems (Eucalyptus grandis Hill ex. Maiden) in two rural properties located in Alegrete County, RS. The traditional pasture system was compared with two other alternative systems, one of them represented by a pasture land converted to homogeneous eucalypt plantation by using two plant densities (2,222 and 1,111 trees.ha -1 ) and the other represented by a silvopastoral system containing 1,000 and 500 trees.ha -1 . The results were analyzed by determining the Internal Retuurn Rate (IRR) and comparing it to the Minimum Attractive Rate (MAR). The alternatives with and without land value were evaluated taking into account the wood price variation (gain and lost of 5%) and the wood yield (gain and lost of 10%). Considering the land value, all alternatives showed that the IRR was lower than the MAR (3.72%). The sensibility analysis showed that when price and yield of the wood had their values increased, for the majority of alternatives considering the practice of thinning, the IRR was higher than the MAR, except to silvopastoral system containing 500 trees.ha -1 . The conclusion was that, the forest component implementation is economically viable for the land owner, except by the fact that it is necessary to disregard the land value in this approach.

Seeds of Cedrela fissilis

No abstract

This study aimed to evaluate the effects of different spacings on wood productivity of two hybrid clones of Eucalyptus, namely E. brassiana × E. urophylla and E. grandis × E. camaldulensis, in the Araripe Plateau. The field trials were established in February 2006 at the Experimental Station of Araripina (latitude: 7°27'50"S; longitude: 40°24'38"W, altitude: 828 m), belonging to the Agronomic Institute of the State of Pernambuco-IPA. Five spacings were tested: 3.0×2.0, 3.0×2.5, 3.0×3.0, 3.0×3.5 and 3.0×4.0 m. The experimental design adopted for both trials was randomized blocks with four replications and plots of 64 plants. The effective areas ranged from 216 to 432 m 2 , and the total experimental area of 11,520 m 2. At the age of four years it was found that there were no statistical differences among the means for the variables evaluated in E. brassiana × E. urophylla. For survival, total height, DBH, wood production and mean annual increment the means were 93%, 14.8 m, 12.3 cm, 98.7 m 3 ha-1 and 24.7 m 3 /ha y-1 , respectively. For E. grandis × E. camaldulensis, the means for the same variables previously described were 89.4%, 13.9 m, 12 cm, 83.3 m 3 ha-1 and 20.8 m 3 /ha y-1 , respectively. Differently from the first, for this hybrid only the survival and height means did not differ significantly from each other. Specifically for DBH, it was noted that the highest value of 13.2 cm, corresponding to the spacing 3.0×4.0 m, did not differ statistically of 12.9 cm obtained from the spacing of 3.0×3.5 m. Nevertheless, these values were significantly different from the others. The highest production of wood was 105 m 3 ha-1 at the spacing 3.0×2.0 m, however, there is no significant difference comparing to 86.3 m 3 ha-1 achieved at the spacing 3.0×2.5 m. Likewise, the mean annual increment (MAI) increased inversely to the spacing. We concluded that the number of plants per hectare plays an emphatic role in increasing the wood productivity of these two hybrids at this stage of development.

No abstract