Observações preliminares sobre a periodicidade e taxa de crescimento em árvores tropicais

Preliminary results of periodicity and increment rate of Cardeiro (Scleronema micranthum Ducke, Bombacaceae) are presented. A cyclic periodicity has been observed. The increment data are strongly correlated to those reported from French Guyana.Resultados preliminares sobre a periodicidade e taxa de crescimento de Cardeiro (Scleronema micranthum Ducke, Bombacaceae) são apresentados. Observou-se ama periodicidade de crescimento. As taxas de incremento são correlacionadas aos resultados referidos da Guiana Francesa

CERTIFICAÇÃO FLORESTAL NO BRASIL UMA FERRAMENTA EFICAZ PARA A CONSERVAÇÃO DAS FLORESTAS NATURAIS?

A certificação florestal é descrita como instrumento de mercado para apoiar um manejo florestal sustentável. Um foco especial é dado pela certificação sob FSC, mas também pelo sistema esquema nacional de certificação florestal no Brasil, o CERFLOR. O que se questiona é se a certificação poderá contribuir com a adoção de práticas de bom manejo pela motivação devido às vantagens advindas da certificação ou pela conscientização do consumidor. As principais forças motrizes do desmatamento nas florestas brasileiras ainda existem, por isso a contribuição da certificação para a conservação das florestas naturais parece ser limitada. FOREST CERTIFICATION IN BRAZIL AN EFFICIENT TOOL FOR THE CONSERVATION OF NATURAL FORESTS? Abstract Forest certification is described as a market-oriented tool to support sustainable forest management. Special emphasis is given to forest certification under FSC, but also to the national certification scheme in Brazil, CERFLOR. The key question is, whether forest certification gives a significant contribution to reduce deforestation and conventional unsustainable logging, respectively under the circumstances of the Brazilian forest sector and domestic consumer behaviour. The main driving forces for deforestation in Brazil still exist and, consequently, the impact of forest certification for the conservation of natural tropical forests in Brazil is still seen to be limited

Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is  < 2000 mm yr⁻¹ (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall  < 2000 mm yr⁻¹

Remarks on age and growth rate determination of amazonian trees

Specific data and comments are given on age and growth rate determination in trees of the Brazilian Amazon basin, based on long-term observation and research of diameter increment, radiocarbon dating, microscopic wood structure, and gamma- and X-ray densitometry; special attention is given to species of the unflooded Terra Firrne forest. Annual dry seasons in eastern Amazonia provoke periodical cambial activity which may be measured as variation in girth increment and is recorded in the wood anatomy as well as its density. Gamma radiation densitometry is discouraged because of poor results. X-ray densitometry and the radiocarbon method are promising but must be refined. Irregular specific climatic events should be considered to be possible natural marks. © 1989 Brill Academic Publishers. All Rights Reserved

Anatomia da madeira de Sebastiania commersoniana (Baillon) Smith & Downs (Euphorbiaceae): aspectos funcionais e ecológicos Wood anatomy of Sebastiania commersoniana (Baillon) Smith & Downs (Euphorbiaceae): functional and ecological aspects

Sebastiania commersoniana é uma espécie arbórea bastante comum em ambientes aluviais, em diversas condições pedológicas, graças a sua plasticidade e capacidade de tolerar períodos de inundação. Foram amostrados 21 indivíduos adultos dessa espécie, na planície do rio Iguaçu, visando à caracterização anatômica da madeira e sua interpretação em termos funcionais. S. commersoniana possui porosidade difusa, vasos solitários e múltiplos de dois a seis, com arranjo radial e placas de perfuração simples. Os vasos são pouco freqüentes (12-16-20/mm²), com diâmetro de 54-88-117 µm e elementos de vaso com comprimento 164-602-1025 µm. As fibras libriformes têm 656-1222-2050 µm de comprimento, 10-26-42 µm de largura, e paredes delgadas a espessas (1,0-2,8-5,1 µm). Fibras gelatinosas são freqüentes. Ocorre parênquima apotraqueal difuso em agregados, e paratraqueal escasso. Os raios, unisseriados, têm 164-805-2787 µm de altura e 12-22-35 µm de largura. Células perfuradas de raio são freqüentes, bem como máculas contendo grãos de amido. Estes também ocorrem no parênquima radial e no axial. A espécie desenvolve lenho de tensão em árvores inclinadas. A maioria dos caracteres observados coincide com descrições disponíveis para o gênero e a família a que a espécie pertence. Algumas características qualitativas são discutidas quanto às suas possíveis funções e implicações para a auto-ecologia da espécie.Sebastiania commersoniana is a very common tree species in alluvial environments with diverse soil conditions due to its plasticity and ability to tolerate periods of flooding. In this study we sampled 21 adult individuals of this species on the Iguaçu River plain, for wood anatomy characterization and interpretation using a functional approach. S. commersoniana has diffuse porous, solitary vessels and multiples of two to six, radially arranged with simple perforation plates; low vessel frequency (12-16-20/mm²), with diameter of 54-88-117 µm, and vessel elements 164-602-1025 µm in length. The fibers are 656-1222-2050 µm in length, 10-26-42 µm wide, the walls are 1.0-2.8-5.1 µm thick. Fibers with a gelatinous layer are common. Apotracheal parenchyma diffusein-aggregates is found, while paratracheal parenchyma is scanty. Rays are uniseriate, 164-805-2787 µm tall and 12-22-35 µm wide. Perforated ray cells are frequent, as well as scar tissue containing starch grains. Starch also occurs in the radial and axial parenchyma. This species develops tension-wood in inclined trees. Most of the features observed coincide with available descriptions of the genus and family to which the species belongs. Some qualitative features are discussed on the base of possible roles and implications for species autoecology

CERTIFICAÇÃO FLORESTAL NO BRASIL – UMA FERRAMENTA EFICAZ PARA A CONSERVAÇÃO DAS FLORESTAS NATURAIS?

A certificação florestal é descrita como instrumento de mercado para apoiar um manejo florestal sustentável. Um foco especial é dado pela certificação sob FSC, mas também pelo sistema esquema nacional de certificação florestal no Brasil, o CERFLOR. O que se questiona é se a certificação poderá contribuir com a adoção de práticas de bom manejo pela motivação devido às vantagens advindas da certificação ou pela conscientização do consumidor. As principais forças motrizes do desmatamento nas florestas brasileiras ainda existem, por isso a contribuição da certificação para a conservação das florestas naturais parece ser limitada. FOREST CERTIFICATION IN BRAZIL AN EFFICIENT TOOL FOR THE CONSERVATION OF NATURAL FORESTS? Abstract Forest certification is described as a market-oriented tool to support sustainable forest management. Special emphasis is given to forest certification under FSC, but also to the national certification scheme in Brazil, CERFLOR. The key question is, whether forest certification gives a significant contribution to reduce deforestation and conventional unsustainable logging, respectively under the circumstances of the Brazilian forest sector and domestic consumer behaviour. The main driving forces for deforestation in Brazil still exist and, consequently, the impact of forest certification for the conservation of natural tropical forests in Brazil is still seen to be limited

Growth models for two commercial tree species in upland forests of the Southern Brazilian Amazon

Despite all efforts to promote sustainable use of timber resources in tropical forests, the current management criteria still require adjustments at a species level, considering specific growth patterns and ecological features. Forest management in upland forests (terra firme) of the Brazilian Amazon region generally applies for all commercial tree species a common minimum logging diameter (MLD) of 50 cm and a felling cycle (FC) varying according to the harvest intensity between 25 and 35 years. In this study, we define species-specific FCs and MLDs for the two commercial tree species Hymenaea courbaril L. (Fabaceae) and Handroanthus serratifolius (Vahl) S.O. Grose (Bignoniaceae) from the terra firme of the Southern Brazilian Amazon, applying growth models based on the relationships between estimated tree age, diameter, height and volume. A total of 37 transversal cross-sections (20 stem discs from Hymenaea and 17 from Handroanthus) were obtained at a height of 20–60 cm above soil level in a private forest concession close to the municipality of Novo Aripuanã in the southern region of the Amazonas state. The two species are common in terra firme forests and have high wood densities of 0.76–0.96 g cm −3 (H. courbaril) and 0.85–1.08 g cm −3 (H. serratifolius). The mean age of H. courbaril and H. serratifolius, estimated by ring counting, varied from 104 to 241 years and both species had similar mean diameter increments of 3.9 ± 0.5 mm year −1 and 4.1 ± 0.6 mm year −1 , respectively. Both species present similar tree growth in diameter, height and volume resulting in a FC of 24.2 years and a MLD of 64.9 cm for H. courbaril, and a FC of 26.0 years and a MLD of 69.5 cm for H. serratifolius. These results demonstrate the need to adjust the selective logging systems practiced in the Brazilian Amazon region towards a species-specific management of timber species to increase the sustainability of selective logging. © 201