782 resultados para Engel, Antke


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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Failures in reforestation are often attributed to nutrient limitation for tree growth. We compared tree performance and nitrogen and phosphorus relations in adjacent mixed-species plantings of contrasting composition, established for forest restoration on Ultisol soil, originally covered by tropical semi-deciduous Atlantic Forest in Southeast Brazil. Nutrient relations of four tree species occurring in both planting mixtures were compared between a legume-dominated, species-poor direct seeding mixture of early-successional species ("legume mixture"), and a species-diverse, legume-poor mixture of all successional groups ("diverse mixture"). After 7 years, the legume mixture had 6-fold higher abundance of N(2)-fixing trees, 177% higher total tree basal area, 22% lower litter C/N, six-fold higher in situ soil resin-nitrate, and 40% lower in situ soil resin-P, compared to the diverse mixture. In the legume mixture, non-N(2)-fixing legume Schizolobium parahyba (Fabaceae-Caesalpinioideae) had significantly lower proportional N resorption, and both naturally regenerating non-legume trees had significantly higher leaf N concentrations, and higher proportional P resorption, than in the diverse mixture. This demonstrate forms of plastic adjustment in all three non-N(2)-fixing species to diverged nutrient relations between mixtures. By contrast, leaf nutrient relations in N(2)-fixing Enterolobium contortisiliquum (Fabaceae-Mimosoideae) did not respond to planting mixtures. Rapid N accumulation in the legume mixture caused excess soil nitrification over nitrate immobilization and tighter P recycling compared with the diverse mixture. The legume mixture succeeded in accelerating tree growth and canopy closure, but may imply periods of N losses and possibly P limitation. Incorporation of species with efficient nitrate uptake and P mobilization from resistant soil pools offers potential to optimize these tradeoffs.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Acompanha-se, aqui, a pertinência do lema de Engels, que concebe o marxismo como herdeiro do idealismo alemão nas teorias de Lukács, Horkheimer e Adorno. Enquanto Lukács assenta o método marxista na vertente da filosofia hegeliana e Horkheimer assume explicitamente o legado kantiano, Adorno não se propõe a ser herdeiro, mas sim crítico do idealismo alemão.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Purpose: This study evaluated the impact of socioeconomic factors on children's performance on tests of working memory and vocabulary.Method: Twenty Brazilian children, aged 6 and 7 years, from low-income families, completed tests of working memory ( verbal short-term memory and verbal complex span) and vocabulary ( expressive and receptive). A further group of Brazilian children from families of higher socioeconomic status matched for age, gender, and nonverbal ability also participated in the study.Results: Children from the low socioeconomic group obtained significantly lower scores on measures of expressive and receptive vocabulary than their higher income peers but no significant group differences were found on the working memory measures.Conclusion: Measures of working memory provide assessments of cognitive abilities that appear to be impervious to substantial differences in socioeconomic background. As these measures are highly sensitive to language ability and learning in general, they appear to provide useful methods for diagnosing specific learning difficulties that are independent of environmental opportunity.

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This study evaluate the native species naturally regenerating in Eucalyptus saligna stand understory. This stand is located at Itatinga Experimental Station, of the Forest Sciences Department (ESALQ/USP). The experimental area encompasses two sites separated from each other around 250 m, differing 30 m in altitude. These two sites are different mainly in land slope and soil fertility and soil hydric retention capacity. Eight permanent plots of 625 m2 in each site were randomly sampled. The woody species Individuals with height equal or bigger than 1,5 m and the Eucalyptus saligna coppicings were surveyed in each plot. A total of 107 species were Identified and 7 species were common to both sites, distributed into 72 genera and 34 families. Based upon the results It is possible to conclude that the Eucalyptus saligna trees do not preclude the natural regeneration of the native species in the stand understory, however the floristic structure of the community is also influenced by edaphic factors and vicinity of seed sources.

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Among 89 plants species growing in a subtropical dry forest fragment located in Botucatu, State of São Paulo, Brazil, 35 species were cut by Atta sexdens, representing 39.34% of the current plants existing in this area. A. sexdens L., 1758 (Hymenoptera: Formicidae) has a selective preference for the following species: Alchornea triplinervia, Faramea cyanea, Cariniana estrellensis and Casearea obliqua, with the first being the most cut species. The frequency and absolute densities of the plant families and species significantly influence the selection process. When comparing the absolute frequency regarding the 10 most cut plant species and the cutting frequency, significant data were obtained only for the euphorbiaceous A. triplinervia species, proving the preference of A. sexdens for this species in particular. These interactions are discussed based on ecological and management factors in agro-ecosystems.

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This paper describes the reproductive phenorhythms of tree species in a tropical seasonal lowland forest in Southeastern Brazil. Every two weeks, five individuals of 41 species were observed for the occurrence of flowering and fruiting, from May 1982 to December 1992. All phenophases showed high seasonality, when considering the whole set of species, but the amplitude of the cycles was much more variable between years; only 13 species had regular flowering. Infra-annual flowering and fruiting were found in 11 and four species, respectively, while only one species flowered and fruited continually. Supra-annual cycles were observed in four (flowering) and seven (fruiting) species. An increase was observed in number of species and individuals flowering and fruiting from 1990 to 1992, following mainly an elevation in the absolute minimum air temperature. These data suggest a relationship between reproductive phenology and major climatic phenomena like El Niño events and solar activity cycles. © International Society for Tropical Ecology.

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Soil seed banks are considered an important mechanism for natural regeneration in tropical forest ecosystems. This paper investigated the soil seed bank in two semideciduous seasonal tropical forest fragments with different disturbance histories in Botucatu, southeastern Brazil. In each study site, 40 superficial soil samples (30 cm × 30 cm × 5 cm) were taken at the end of both the dry and rainy seasons. The seeds were estimated by the germination method. Average soil seed density was 588.6 and 800.3 seeds m-2, respectively, for site 1 (less disturbed) and site 2 (more disturbed). Seed density and diversity (H′) were significantly higher in site 2 in both seasons. Non-woody taxa predominated in both fragments, but pioneer tree species were better represented in the less disturbed forest. Both ecosystems have a potential for regeneration from soil seed banks, but this potential is higher in the less disturbed site. Low richness and density of pioneer tree species in the seed bank indicate that the ecosystem has lost its resilience. The seed bank is not as important in these ecosystems as in other forests. Results indicate that management strategies to restore these forests should take into account the possibility of recovering soil seed bank processes and dynamics. © 2007 Elsevier B.V. All rights reserved.

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This study aimed at characterizing the potential for natural regeneration of native vegetation in the under-story of an earlier Eucalyptus saligna Smith production stand. The study was carried out at the Parque das Neblinas, Bertioga municipality, SP, in a 45 ha third rotation stand; which had been abandoned 15 years ago for natural regeneration to occur. The sampling was done in 24 plots of 20 × 40 m. The sampled area was of 19,200 m2, with inventory made of 100% of the eucalyptus trees. All regeneration trees with a height ≥ 1.30 m and DBH ≥ 5.0 cm were measured, as well as adult individuals with DBH ≥ 5.0 cm; surveyed in two size classes. 1,417 individuals of E. saligna were measured, with a density of 738,02 individuals/ha and a basal area of 22.69 m2/ha. Among 2,763 natural regeneration individuals, 111 species belonged to 66 genera and 34 botanical families. The species represented 43.7% of the tree richness of neighboring native forest fragments. The total estimated density and the basal area were respectively 1,052.6 individuals/ha and 6.4 m2/ha of autochthonous trees with DBH ≥ 5.0 cm (Class 1); while for regeneration there were 3,864.58 individuals/ha, and 2.76 m2/ha of individuals with a height ≥ 1.30 m and DBH < 5.0 cm (Class 2). Shannon diversity (H') was 2.83 and 3.68, respectively, for Classes 1 and 2, and the corrected species richness for a 1000-individual sample (R1000) were 75.6 and 87.29 (Fisher's a index) for the same classes. The majority of the species (34.84%) was typical from the understory of wet tropical forest and had zoochoric fruit dispersal (67.57%). The results indicate that, under these conditions, a eucalyptus forest is able to provide adequate regeneration niches for native vegetation, and may represent a sink habitat for local populations.

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Incluye Bibliografía

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Incluye Bibliografía

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The main aspects of restoration, in various ecosystems, are here discussed, by means of a bibliographic analysis of the last twenty-eight years. The main concepts, research themes and target ecosystems are also described.