Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees

Induced polyploidy potential for improving resistance in Hevea clones to rubber tree leaf blight.

Components of resistance that reduce the epidemic rate of rubber tree leaf blight, have been evaluated on colchicine-induced polyploids (CIP) Hevea clones and on their respective natural diploids after inoculation of virulente Microcyclus ulei isolates to the diploid clones. SomeCIP clones have presented high level of resistance in comparison with their susceptible diploid clones, whereas other CIP clones were susceptible. The polyploid plant inherent factors controlling the resistanceto M. ulei and the induced polyploid potential for rubber tree breeding aiming at resistance to leaf blight are discussed.Made available in DSpace on 2015-08-13T07:22:54Z (GMT). No. of bitstreams: 1 p.1218.pdf: 5857021 bytes, checksum: 68c790fa3f1a834640ce8f23ea06b7e6 (MD5) Previous issue date: 1996-12-17199

Emissão de fluxos foliares, floração e ciclagem de nutrientes em clones de copa de Hevea pauciflora Fluxes emission of leaves, flowering and nutrient cycling in crown clones of Hevea pauciflora

A fenologia foliar tem sido utilizada como uma característica importante na seleção dos clones de Hevea spp., enquanto o teor de nutrientes na serapilheira é um bom indicador da ciclagem de nutrientes. O objetivo deste trabalho foi verificar o efeito da periodicidade de emissão de fluxos foliares na floração de copa de Hevea pauciflora, estado nutricional e qualidade da serapilheira. Foram avaliadas 15 plantas de 10 anos de idade dos clones de copa CNS G 112, CNS G 124 e CBA 2. Nas condições edafoclimáticas da Amazônia tropical úmida, a emissão de folhas e de floração de H. pauciflora ocorre com maior intensidade no segundo semestre (início do período chuvoso). A H. pauciflora apresenta maior acúmulo de serapilheira que a floresta primária e os teores foliares de 22,18 g kg-1 de N, 1,47 g kg-1 de P, 5,77 g kg-1 de K, 3,79 g kg-1 de Ca, 2,09 g kg-1 de Mg, 16,15 mg kg-1 de B, 6,14 mg kg-1 de Cu, 53,87 mg kg-1 de Fe, 66,20 mg kg-1 de Mn e 48,44 mg kg-1 de Zn podem ser utilizados como referência para essa espécie de seringueira.<br>The leaf phenology has been used as an important characteristic in the selection of Hevea spp. clones, while the nutrient content in litter is a good indicator of nutrient cycling. The objective of this study was to verify the effect of frequency of emission of fluxes of leaves and flowers in crown of Hevea pauciflora, nutritional status and quality of litter. Fifteen plants of ten-year-old of each clones (CNS G 112, CNS G 124 and CBA 2) were evaluated. In tropical Amazonia edaphoclimatic conditions, the leaf emergence and flowering of H. pauciflora occurs with higher intensity in the second semester (beginning of rainy season). The H. pauciflora has higher quantity of litter than the primary forest, and the foliar concentrations of 22.18 g kg-1 of N, 1.47 g kg-1 of P, 5.77 g kg-1 of K, 3.79 g kg-1 de Ca, 2.09 g kg-1 of Mg, 16.15 mg kg-1 of B, 6.14 mg kg-1 of Cu, 53.87 mg kg-1 of Fe, 66.20 mg kg-1 of Mn e 48.44 mg kg-1 of Zn can be utilized as reference for this specie of rubber tree

Aplicação de KCN e linamarina e a incompatibilidade de enxertia por translocação no clone de seringueira IPA 1 KCN and linamarin applications and the translocation incompatibility of crown clones of Hevea sp. budded onto IPA 1

Para caracterizar evidências indiretas do envolvimento dos glicosídeos cianogênicos da seringueira, cujo principal componente é a linamarina, no desenvolvimento dos sintomas de incompatibilidade de enxertia por translocação apresentados pelo clone de painel IPA 1 (Hevea brasiliensis) em enxertos de copa com vários clones de outras espécies de Hevea, tentou-se sua reprodução através da aplicação de soluções com concentrações de cianeto de potássio (KCN) e linamarina no caule do clone IPA 1 e dos clones Fx 4098 e Fx 3864, que não apresentam reação de incompatibilidade com os mesmos clones incompatíveis com o IPA 1. A aplicação de soluções de KCN no caule provocaram rápida coagulação do látex nos laticíferos do IPA 1 com concentrações muito baixas de KCN e mais altas no Fx 4098. No Fx 3864, não houve efeito, exceto leve redução de escoamento com a dose mais alta. Os tratamentos com KCN causaram necrose apenas próximo ao local das aplicações. Com soluções de linamarina, a necrose, também precedida pela coagulação do látex, ocorreu em maior extensão do caule, o que indica maior mobilidade de linamarina, que do KCN. O IPA 1 mostrou-se, novamente, mais sensível às concentrações mais baixas de linamarina, com doses mais altas provocando os mesmos efeitos no Fx 4098 e sem ocorrência de efeitos no Fx 3864. Nos tratamentos com linamarina observou-se o acúmulo de HCN livre na casca do caule do clone IPA 1, responsável pelos sintomas observados. A incompatibilidade com o IPA 1 é provocada pela translocação de glicosídios cianogênicos das copas enxertadas no IPA 1, que não é dotado de suficiente capacidade de remoção do HCN liberado na hidrólise desses glicosídios, tendo o Fx 3864 apresentado desintoxicação mais eficiente.<br>To further evaluate previous indirect evidences of a role for the rubber tree cyanogenic glycosides, of which the main component is linamarin, this study evaluated the translocation incompatibility of the clone IPA 1 (Hevea brasiliensis) with budded crowns of clones of other species. Solutions of KCN were first applied, which caused rapid coagulation of the latex in the laticiphers of IPA 1, at very low concentrations, the same effect being observed in Fx 4098 at higher concentrations. The clone Fx 3864 presented no effect, only a slight reduction of the latex flow at the highest concentration. With linamarin solutions the necrosis, again preceded by latex coagulation, spread longer along the stem, indicating a higher mobility of linamarin than KCN. The clone IPA 1 behaved again sensitive to the lower concentrations of linamarin, with the higher concentrations causing the same effects on Fx 4098 and no effect on Fx 3864. With linamarin a build up of free HCN was detected in the bark of IPA 1. The incompatibility with IPA 1 is caused by the translocation of cianogenic glycosides from the budded crowns to the stem which is deprived of sufficient capacity to remove the HCN liberated by the hydrolisis of cyanogenic glicosides, while the Fx 3864 presented a very efficient detoxifying capacity