Densidade da madeira de árvores em savanas do norte da Amazônia brasileira

Densidade da madeira (DM) é uma variável importante para estimativas de estoques de carbono arbóreo em ecossistemas terrestres. Este tema é pobremente investigado em áreas de savana da Amazônia brasileira. O objetivo deste estudo foi investigar a DM das oito principais espécies arbóreas que ocorrem na savana aberta de Roraima, a maior área de savana do norte do bioma Amazônia. Foram verificadas as variações na DM em função da espécie e dos diferentes diâmetros observados ao longo da dimensão vertical de 75 indivíduos amostrados em seis sítios de coleta. Foi utilizado o método direto para obtenção de peças de madeira do fuste e da copa. Os resultados indicaram discrepância significativa interespecífica, sendo Roupala montana Aubl. a espécie de maior DM média (0,674 g cm-3). Foi detectado que existe variação significativa da DM entre as peças do fuste e da copa, independente da espécie e do sítio de coleta. A densidade da madeira de peças da copa com diâmetro entre 5 e 10 cm pode ser utilizada como preditora da DM média do indivíduo arbóreo. Nós concluimos que a DM das oito espécies arbóreas investigadas possui variabilidade interespecífica, com discrepâncias entre a DM do fuste e das partes lenhosas da copa. As distinções aqui detectadas devem ser considerados como uma importante ferramenta para melhorar as estimativas de estoque de carbono em áreas de savanas na Amazônia

Data from: Radial changes in wood specific gravity of tropical trees: inter- and intra-specific variation during secondary succession

Variation in wood specific gravity (WSG) within and across species of tropical trees is poorly studied in relation to vegetation change during tropical forest succession. We investigated WSG of 91 species in eight long-term plots along a successional chronosequence in northeastern Costa Rica. Radial changes in WSG were described by the rate of change (slope) along the stem radius. Significant radial changes were found in 42 of 74 species, with 37 species exhibiting increases from inner to outer wood, and 5 exhibiting decreases. Radial increases were commonly observed in species with inner WSG below 0.5, whereas radial decreases were observed in species with inner WSG above 0.7. Wood specific gravity weighted by cross-sectional area (wWSG) varied four-fold among species. Species classified as second-growth specialists had lower wWSG, lower inner and outer WSG, and higher slopes than old-growth specialists; successional generalists showed intermediate trait values. Among 18 species sampled in both second- and old-growth forests, 4 species (22%) showed significant variation in wWSG between forest types. Of 33 widely sampled species, seven species (21%) showed a significant effect of stem diameter on wWSG. Second-growth plots had lower stand-level wWSG and more pronounced radial increases than old-growth plots. Individual tree biomass for species with radial increases and low WSG was substantially underestimated when based on unweighted WSG compared to wWSG. Wood specific gravity varied with successional stage at multiple levels: within species, among successional specialist groups, and across plots of varying ages. Radial increases in WSG are common among trees in early and intermediate stages of tropical forest succession. This trait may confer growth advantages early in succession and increased resistance to physical or biotic damage during later successional stages

PRELIMINARY RESULTS OF ORGANOCHLORINES LEVELS AND BIOMARKER RESPONSES IN SKIN BIOPSIES OF THE COMMON BOTTLENOSE DOLPHINS FROM THE ADRIATIC SEA (MEDITERRANEAN SEA)

The main objective of this study was to apply a sensitive non-lethal “multi-trial-diagnostic–tool” in skin biopsy of common bottlenose dolphin (Tursiops truncatus), combining molecular biomarkers (western blot of CYP1A1, CYP2B) with analysis of OCs, in subcutaneous blubber, to evaluate the toxicological status of this odontocete species in the Adriatic Sea (Mediterranean Sea). The results of these analyses were compared with those obtained on samples collected in two other areas: the Strait of Gibraltar and the Sicily Channel. The multi-trial biomarker tool applied to skin biopsies underlined differences in OCs and molecular biomarker responses between genders (male greater than female) and among these three areas, revealing a lower toxicological stress in the bottlenose dolphins of the central Adriatic Sea

Tree morphology in seasonally dry montane forest in Argentina: Relationships with shade tolerance and nutrient shortage

Question: How does form (leaf and trunk morphology) relate to function (tolerance of shade and nutrient storage) in trees? Location: Los Toldos montane valley in NW Argentina. Methods: We analysed the relationships amongst (1) ten vegetative and four reproductive traits across 40 tree species, (2) a distribution based measure of recruitment under shade and (3) a distribution based measure of recruitment over a soil fertility gradient. Results: Ordinations revealed three main axes of speciesʼ morphological differentiation: (1) evergreen species had leaves with a lower specific leaf area, greater tensile resistance and slower decomposition rate, denser wood and thinner bark than deciduous species; (2) tall tree species that lack spines and are anemochorous were separated from short, spinescent and zoochorous species and (3) species were distinguished according to clonal growth, seed mass and pollination syndromes. Notably, speciesʼ recruitment under shade and over a soil fertility gradient were independent of each other, but both were correlated with speciesʼ scores along the first axis of morphological variation (tolerant species have attributes that favour resource conservation). Different sets of traits were correlated with recruitment under shade and over a soil fertility gradient when traits where assessed individually. Amongst shade tolerant species, recruitment under shade was negatively correlated with speciesʼ maximum height, suggesting differential responses to vertical gradients of light. Conclusions: These results provide new evidence of integration between leaf and stem morphology which is consistent with an evolutionary compromise between high rate of resource acquisition and resource conservation. Generalizations about the functional value of individual morphological characteristics and of ʻstrategiesʼ vary with the resolution of analyses.Fil: Easdale, Tomás A.. University of Wales; Reino Unido. Universidad Nacional de Tucumán; ArgentinaFil: Gurvich, Diego Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Sersic, Alicia Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Healey, John R.. University of Wales; Reino Unid

Data from: Does biomass growth increase in the largest trees? Flaws, fallacies and alternative analyses

The long-standing view that biomass growth in trees typically follows a rise-and-fall unimodal pattern has been challenged by studies concluding that biomass growth increases with size even among the largest stems in both closed forests and in open competition-free environments. We highlight challenges and pitfalls that influence such interpretations. The ability to observe and calibrate biomass change in large stems requires adequate data regarding these specific stems. Data checking and control procedures can bias estimates of biomass growth and generate false increases with stem size. It is important to distinguish aggregate and individual-level trends: a failure to do so results in flawed interpretations. Our assessment of biomass growth in 706 tropical forest stems indicates that individual biomass growth patterns often plateau for extended periods, with no significant difference in the number of stems indicating positive and negative trends in all but one of the 14 species. Nonetheless, when comparing aggregate growth during the most recent five years, 13 out of our 14 species indicate that biomass growth increases with size even among the largest sizes. Thus, individual and aggregate patterns of biomass growth with size are distinct. Claims concerning general biomass growth patterns for large trees remain unconvincing. We suggest how future studies can improve our knowledge of growth patterns in and among large trees