Regeneration of five commercially-valuable tree species after experimental logging in an Amazonian forest

This study investigated the regeneration variation of five commercially valuable tree species in relation to different intensities of felling in fourteen 4-ha plots in an area under experimental forest management. This experiment was carried out in a typical Amazonian tropical forest sample on "terra-firme," in Manaus (AM). Plots were logged 7 and 8 years (1987 and 1988), or 3 years (1993) before the study. All trees with height greater than 2 m, and diameter at breast height (DBH) smaller than 10 cm were measured. Only Aniba hostmanniana, Ocotea aciphylla, Licaria pachycarpa, Eschweilera coriacea and Goupia glabra were sufficiently common for individual analyses. These species have high timber values in the local market. Eight years after logging, the species responded differently to logging intensities. The numbers of individuals of Goupia glabra and Aniba hostmanniana were positively related to the intensity of logging, while Ocotea aciphylla, Licaria pachycarpa, and Eschweilera coriacea showed no statistically significant response. In the most recently (1993) logged areas, Goupia glabra and Aniba hostmanniana had higher numbers of individuals than the control plots.

Chlorophyll fluorescence of tropical tree species in a semi-deciduous forest gap

The characterization of different ecological groups in a forest formation/succession is unclear. To better define the different successional classes, we have to consider ecophysiological aspects, such as the capacity to use or dissipate the light energy available. The main objective of this work was to assess the chlorophyll fluorescence emission of tropical tree species growing in a gap of a semi-deciduous forest. Three species of different ecological groups were selected: Croton floribundus Spreng. (pioneer, P), Astronium graveolens Jacq. (early secondary, Si), and Esenbeckia febrifuga A. Juss. (late secondary, St). The potential (Fv/Fm) and effective (deltaF/Fm') quantum efficiency of photosystem II, apparent electron transport rate (ETR), non-photochemical (qN) and photochemical (qP) quenching of fluorescence were evaluated, using a modulated fluorometer, between 7:30 and 11:00 h. Values of Fv/Fm remained constant in St, decreasing in P and Si after 9:30 h, indicating the occurrence of photoinhibition. Concerning the measurements taken under light conditions (deltaF/Fm', ETR, qP and qN), P and Si showed better photochemical performance, i.e., values of deltaF/Fm', ETR and qP were higher than St when light intensity was increased. Values of qN indicated that P and Si had an increasing tendency of dissipating the excess of energy absorbed by the leaf, whereas the opposite was found for St. The principal component analysis (PCA), considering all evaluated parameters, showed a clear distinction between St, P and Si, with P and Si being closer. The PCA results suggest that chlorophyll fluorescence may be a potential tool to differentiate tree species from distinct successional groups.

Um modelo otimizador para organização dos compartimentos de exploração em floresta tropical

Existe a necessidade de garantia de um fluxo constante de madeira com potencial comercial para a viabilidade da pequena propriedade, porém nem sempre isto é possível, pelo fato de os talhões serem pequenos e, principalmente, a distribuição das espécies de interesse na floresta nativa ser irregular, por serem os ecossistemas heterogêneos e pela variedade de tipologias florestais que formam um complexo mosaico. Este trabalho teve como finalidade principal apresentar um modelo matemático que auxilie no planejamento e na distribuição dos talhões em uma pequena propriedade da floresta tropical. O modelo matemático resultou em um novo conceito de talhão. Com base no inventário pré-exploratório, os talhões foram subdivididos em compartimentos, onde foram consideradas características diferenciais como: espécie, volume por espécie, abundância, possibilidade de mercado e, principalmente, valor final de cada subtalhão. Para definição do modelo matemático utilizou-se a PM (programação por metas), que se faz necessária na seleção dos subtalhões, combinando-os e unindo-os em uma área equivalente ou menor que a do compartimento anual original. Este modelo, ao mesmo tempo que organiza novos talhões, determina a taxa de extração anual e sua possível renda, além de limitar a área do compartimento a ser explorado, o que se faz necessário para garantia da regeneração do compartimento no ciclo de corte previsto. Como resultado, o modelo proposto mostrou-se bastante superior ao formal e garantiu sobremaneira o equilíbrio do rendimento anual para o pequeno proprietário.

Validação do mapeamento de uma área de floresta tropical com o uso imagens de videografia aérea e dados de levantamento de campo

Este trabalho apresenta o mapeamento da cobertura vegetal da região da Floresta Nacional do Tapajós (FNT) no Pará, realizado por imagens multitemporais do satélite Landsat. Para a validação do mapeamento, foram utilizadas imagens de videografia aérea e dados de levantamento de campo. Através da análise da matriz de confusão, foram observados uma exatidão global de classificação de 84,5% e um índice kappa de 80,9%. O uso dos mosaicos de videografia aérea e dos pontos de levantamento de campo, dentro de um sistema de informação geográfica, permitiu caracterizar e avaliar a qualidade do mapeamento da região da FNT.

Measurement and simulation of solar radiation availability in relation to the growth of coffee plants in an agroforestry system with rubber trees

Solar radiation is an important factor for plant growth, being its availability to understory crops strongly modified by trees in an Agroforestry System (AFS). Coffee trees (Coffea arabica - cv. Obatã IAC 1669-20) were planted at a 3.4 x 0.9 m spacing inside and aside rows of monocrops of 12 year-old rubber trees (Hevea spp.), in Piracicaba-SP, Brazil (22º42'30" S, 47º38'00" W - altitude: 546m). One-year-old coffee plants exposed to 25; 30; 35; 40; 45; 80; 90; 95 and 100% of the total solar radiation were evaluated according to its biophysical parameters of solar radiation interception and capture. The Goudriaan (1977) adapted by Bernardes et al. (1998) model for radiation attenuation fit well to the measured data. Coffee plants tolerate a decrease in solar radiation availability to 50% without undergoing a reduction on growth and LAI, which was approximately 2m².m-2 under this condition. Further reductions on the availability of solar radiation caused a reduction in LAI (1.5m².m-2), thus poor land cover and solar radiation interception, resulting in growth reduction.

Evaluation of the throughfall and stemflow nutrient contents in mixed and pure plantations of Acacia mangium, Pseudosamenea guachapele and Eucalyptus grandis

The interception of the rainfall by the forest canopy has great relevance to the nutrient geochemistry cycle in low fertility tropical soils under native or cultivated forests. However, little is known about the modification of the rainfall water quality and hydrological balance after interception by the canopies of eucalyptus under pure and mixed plantations with leguminous species, in Brazil. Samples of rainfall (RF), throughfall (TF) and stemflow (SF) were collected and analyzed in pure plantations of mangium (nitrogen fixing tree -NFT), guachapele (NFT) and eucalyptus (non-nitrogen fixing tree -NNFT) and in a mixed stand of guachapele and eucalyptus in Seropédica, State of Rio de Janeiro, Brazil. Nine stemflow collectors (in selected trees) and nine pluviometers were randomly disposed under each stand and three pluviometers were used to measure the incident rainfall during 5.5 months. Mangium conveyed 33.4% of the total rainfall for its stem. An estimative based on corrections for the average annual precipitation (1213 mm) indicated that the rainfall's contribution to the nutrient input (kg ha-1) was about 8.42; 0.95; 19.04; 6.74; 4.72 and 8.71 kg ha-1 of N-NH4+, P, K+, Ca+2, Mg+2 and Na+, respectively. Throughfall provided the largest contributions compared to the stemflow nutrient input. The largest inputs of N-NH4+ (15.03 kg ha-1) and K+ (179.43 kg ha-1) were observed under the guachapele crown. Large amounts of Na+ denote a high influence of the sea. Mangium was the most adapted species to water competitiveness. Comparatively to pure stand of eucalyptus, the mixed plantation intensifies the N, Ca and Mg leaching by the canopy, while the inputs of K and P were lower under these plantations.

Chloroplastid pigment contents and chlorophyll a fluorescence in Amazonian tropical three species

Plants react to changes in light and hydrological conditions in terms of quantity and composition of chloroplastidic pigments, which affects the photosynthetic properties and consequently the accumulation of plant biomass. Thus, the chloroplastidic pigment concentration and chlorophyll a fluorescence of three Amazonian species (Bertholletia excelsa, Carapa guianensis e Dipteryx odorata) were investigated in sun and shade leaves form the tree crown collected during two distinct periods of precipitation (dry and rainy seasons). Pigment contents were determined by spectrophotometry and fluorescence variables were determined using a portable fluorometer. The results demonstrated that the species showed high concentrations of Chl a, Chl b e Chl total during the wet season in relation to the dry season, especially in shade leaves. A higher concentration of carotenoids was found in B. excelsa, when compared with leaves of C. guianensis and D. odorata. In leaves of B. excelsa and D. odorata no significant difference was found in relation to the photochemistry of photosystem II (Fv/Fm) between the wet and dry seasons. In conclusion, the three species react differently to variations in the light and precipitation conditions regarding light capture, aspects that might be considered in the management of forest plantations.

Análise do mosaico silvático em um fragmento de floresta tropical estacional no sudeste do Brasil

Este estudo foi realizado na "Mata da Câmara", um fragmento de floresta estacional semidecídual localizado em São Roque, SP, e teve como objetivos a identificação e análise do mosaico silvático, discutindo-se a arquitetura atual da floresta e inferindo sobre sua dinâmica de construção. Utilizou-se o método de inventário de linhas interceptadas, em que se amostraram três áreas de 50 × 105 m. Os resultados indicaram que as porcentagens de área ocupada por ecounidades em equilíbrio 2A foram de 46,8%, 48,6% e 75,7%, respectivamente nas três áreas estudadas. Pode-se concluir que na área A há uma floresta jovem, na área B uma floresta em fase de pré-maturidade com sinais de perturbações recentes e antigas e na área C uma floresta madura com alguns sinais de perturbações antigas. Comparando os resultados desta análise com aqueles obtidos através de levantamento fitossociológico, realizado na mesma área, a análise silvigenética mostrou ser mais uma importante ferramenta para discussão da dinâmica florestal, mas que em alguns caso tende a superestimar o grau de maturidade das florestas. No contexto dos fragmentos florestais remanescentes do Estado de São Paulo, pode-se dizer que a Mata da Câmara representa uma área de floresta relativamente bem preservada.

Coffee water use in agroforestry system with rubber trees

Water uptake and use by plants are essentially energy processes that can be largely modified by percentage of soil cover, plant type; foliage area and its distribution; phenological stage and several environmental factors. Coffee trees (Coffea arabica - cv. Obatã IAC 1669-20) in Agrforestry System (AFS) spaced 3.4x0.9m apart, were planted inside and along rows of 12- year-old rubber trees (Hevea spp.) in Piracicaba-SP, Brazil (22 42'30" S, 47 38'00" W - altitude: 546m). Sap flow of one-year-old coffee plants exposed to 35; 45; 80; 95 and 100% of total solar radiation was estimated by the heat balance technique (Dynamax Inc.). Coffee plants under shade showed greater water loss per unit of incident irradiance. On the other hand, plants in monocrop (full sun) had the least water loss per unit of incident irradiance. For the evaluated positions average water use was (gH2O.m-2Leaf area.MJ-1): 64.71; 67.75; 25.89; 33.54; 27.11 in Dec./2002 and 97.14; 72.50; 40.70; 32.78; 26.13 in Feb./2003. This fact may be attributed to the higher stomata sensitivity of the coffee plants under more illuminated conditions, thus plants under full sun presented the highest water use efficiency. Express transpiration by leaf mass can be a means to access plant adaptation to the various environments, which is inaccessible when the approach is made by leaf area.

Structural aspects and floristic similarity among tropical dry forest fragments with different management histories in northern Minas Gerais, Brazil

In order to produce useful knowledge to the initiatives of protection and management of forest fragments, more specifically for tropical dry forests which suffer with frequent anthropic activities, and due to the lack of specific studies, this article aimed describe the structure and the floristic similarity among three areas of dry forest with different management histories. The study was developed in Capitão Enéas municipality, Northern Minas Gerais, Brazil, where three fragments were evaluated, being one in regeneration for 30 years, another submitted to occasional fire and the third with selective cut in small scale. The sampling was developed through the point quarter method considering all the alive phanerophyte individuals with circumference at breast height (CBH) > 15 cm. In the three fragments, 512 individuals, distributed in 60 species, 47 genera, and 23 families were sampled. The most representative families were Fabaceae (26), Anacardiaceae (4), Bignoniaceae (3) and Combretaceae (3). However, fourteen families were represented by only one species. Only eight species were common to all fragments - Myracrodruon urundeuva standed out with 26.9% of all sampled individuals - while a great number of species were exclusive of each fragment. The floristic and structural differences between the fragments are possibly related to the history and intensity of management in each area besides the topography variations and the presence or absence of limestone outcrops. These results show the importance of each fragment, indicating that the loss of anyone would cause negative impacts on the regional flora and consequently to the associated biodiversity.

Cover layers to the growth of trees and shrobs over a sulfide spoil from gold mining

This work was done at a gold mine company in Paracatu, MG, Brazil, and was conducted from March 2000 to November 2005. The substrate (spoil) studied was a phillite rock which contains sulfides such as pyrite and arsenopyrite. This study aimed to evaluate the survival and growth of plant species on different combinations of substrate layers over the spoil. These layers were a cover layer and a sealing layer, both deposited over the spoil. The treatment 1 had saprolite (B1) in the sealing layer (SL) and B1 with liming (B1L) in the cover layer (CL). The treatment 2 had B1 in SL and B1L + soil with liming (SoL) in the CL. The treatment 3 had B1 + SoL in the SL and B1L in the CL. The treatment 4 had B1 + SoL in the SL and B1L + SoL in the CL. The plant species used were Acacia farnesiana, A. holosericea, A. polyphylla, Albizia lebbeck, Clitoria fairchildiana, Flemingia sp., Mimosa artemisiana, M. bimucronata e Enterolobium contortisiliquum. Forty and 57 months after planting, collardiameter, height, and living plants were evaluated. The greatest survival rate was oobservedintreatmentwith B horizon of an Oxisoil in both layers, with 80 %. In general, M. bimucronata and A. farnesiana species showed the highest survival rate. The arsenic-content by Mehlich 3 in the cover layer ranged from 0.00 to 14.69 mg dm- 3 among treatments. The experimental results suggest that layers combinations above the sulfide substrate allow the rapid revegetation of the spoil.

The role of arbuscular mycorrhizal fungi on the early-stage restoration of seasonally dry tropical forest in Chamela, Mexico

It was evaluated the effect of two different sources of local inocula from two contrasting sites (mature forest, pasture) of arbuscular mycorrhizae fungi (AMF) and a non-mycorrhizal control on the plant growth of six woody species differing in functional characteristics (slow-, intermediate- and fast-growth), when introduced in a seasonally tropical dry forest (STDF) converted into abandoned pasture. Six plots (12 X 12m) were set as AMF inoculum source. Six replicates of six different species arranged in a Latin Square design were set in each plot. Plant height, cover area and the number of leaves produced by individual plant was measured monthly during the first growing season in each treatment. Species differed in their ability to benefit from AMF and the largest responsiveness in plant height and leaf production was exhibited by the slow-growing species Swietenia humilis, Hintonia latiflora and Cordia alliodora. At the end of the growing season (November), the plant height of the fast growing species Tabebuia donnel-smithii, Ceiba pentandra and Guazuma ulmifolia were not influenced by AMF. However, inocula of AMF increased leaf production of all plant species regardless the functional characteristics of the species, suggesting a better exploitation of above-ground space and generating a light limited environment under the canopy, which contributed to pasture suppression. Inoculation of seedlings planted in abandoned pasture areas is recommended for ecological restoration due to the high responsiveness of seedling growth in most of species. Use of forest inoculum with its higher diversity of AMF could accelerate the ecological restoration of the above and below-ground comunities.

A riqueza e composição de formigas como indicadores dos efeitos do manejo florestal de baixo impacto em floresta tropical no estado do Acre

A sustentabilidade da extração madeireira seletiva depende de avaliações de impacto e monitoramento dos fatores abióticos, vegetação e fauna. Os objetivos deste trabalho foram estimar e comparar a riqueza e composição de formigas em área de manejo florestal sustentável de baixo impacto, no Projeto de Assentamento Chico Mendes, no Acre. As coletas foram realizadas com armadilhas pitfall e extrator de Winkler, em 30 parcelas de 10 x 10 m. As parcelas foram igualmente distribuídas em três tratamentos: (1) manejo - base de árvores exploradas em 2007; (2) queda natural - base de árvores caídas naturalmente em área não manejada; e (3) controle - parcela sem queda de árvore na mesma área não manejada. Para a caracterização da vegetação, foram tomadas medidas das variáveis: densidade arbórea e arbustiva, área basal arbórea e de árvores caídas, espessura de serapilheira e cobertura de dossel. A densidade arbórea foi significantemente maior no tratamento controle que no manejo. Diferenças significativas foram encontradas em cobertura de dossel entre os tratamentos controle e manejo e controle e queda natural. Foram coletadas 88 espécies de formigas, distribuídas em sete subfamílias. Não houve diferença na riqueza de espécies entre os tratamentos. Embora menor similaridade tenha sido encontrada entre os tratamentos manejo e controle, não foram observadas grandes diferenças na composição entre eles. Esses resultados indicaram que, nessa área, a atividade de extração madeireira de baixo impacto não afetou a assembleia de formigas, portanto, funcionalmente, essa forma de manejo não acarretou alterações no ecossistema em relação aos serviços associados às formigas.

Soil organic matter pools in a tropical savanna under agroforestry system in Northeastern Brazil

This study aimed at quantifying total organic carbon stocks and its pools in Acrisol under agroforestry systems with six (AFS6) and thirteen years old (AFS13), slash-and-burn agriculture (SBA) and savanna native forest (SNF) in northeastern Brazil. Soil samples were collected at 0-0.05 m, 0.05-0.10 m, 0.10-0.20 m and 0.20-0.40 m depths in the dry and rainy seasons to evaluate total organic carbon (TOC) stocks and labile carbon (LC), fulvic acid fraction (C-FAF), humic acid fraction (C-HAF), humin (C-HF) and microbial biomass carbon (Cmic) contents. Additionally, carbon management index (CMI) was determined. Higher TOC stocks (97.7 and 81.8 Mg ha-1 for the 0-0.40 m depth in the dry and rainy seasons, respectively) and LC, humic substances and Cmic contents were observed in the AFS13 in all the depths. CMI also was higher in the AFS13 (0-0. 05 m: 158 and 86; 0.05-0.10 m: 171 and 67, respectively for the dry and rainy seasons) especially when compared to the SBA (0-0.05 m: 5.6 and 5.4; 0.05-0.10 m: 5.3 and 5.8, respectively for dry and rainy seasons). The agroforestry systems increased soil quality through the conservation of organic matter and can be considered an excellent strategy to assurance sustainability in tropical soil of Northeastern Brazil

Diversidad florística arbórea y su relación con el suelo en un bosque pluvial tropical del chocó biogeográfico

El objetivo del presente estudio fue determinar la composición y diversidad florística arbórea a escala local en un bosque del Chocó biogeográfico, una de las regiones más lluviosas del mundo, y su relación con las características del sitio. Se emplearon dos parcelas de una hectárea, en las cuales se determinó la composición y diversidad de árboles con DAP > 10 cm y se relacionaron con los nutrientes del suelo, la topografíay el espacio. No se presentaron diferencias significativas entre las parcelas para las variables estructurales y de diversidad estudiadas, con valores de abundancia de 640 y 716 individuos/ha yde riqueza de 174 y 223 especies/ha.Nuestros resultados soportan la hipótesis de hiperdominancia de unos pocos grupos biológicos en los bosques húmedos tropicales. Ladiversidad arbórea a escala local se relacionó significativamente con algunas condiciones edáficas.Se presentó asociación positiva de la diversidad con el aluminio del suelo, y negativa con la topografía.No obstante, solamente un 37% de la variación en la composición florística fue explicada por las variables espaciales y ambientales (topográficas y edáficas). Por ello, aparentemente la distribución de las especies a escala local parece estar gobernada principalmente por procesos aleatorios o biológicos (como la limitación en dispersión), conforme lo propone la teoría neutral. El papel de las adaptaciones específicas al hábitat (teoría del nicho) pareciera ser limitado.