Navegando por Assunto "Pollen"

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Acesso aberto (Open Access)
Impactos das mudanças do nível do mar nos manguezais do sudeste do brasil durante o holoceno e antropoceno usando uma abordagem multi-proxy
(Universidade Federal do Pará, 2020-12-28) BOZI, Bettina Silva; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228
Mangroves are intertidal forests, susceptible to changes in tidal flooding frequency. Then, its dynamics along the topographic gradients of a coastal plain may be used as an indicator of sea-level changes. This work aims to identify the mangrove dynamics during the Holocene and Anthropocene and infer relative sea-level (RSL) changes based on satellite/drone images and pollen, isotopes (δ13C, δ15N), elemental (C\N), X-ray fluorescence (XRF), and sedimentary data, as well as C-14 dating along three cores sampled along a mangrove and a transition mangrove/herbaceous zone following a topographical gradient of a coastal plain in the southeastern Brazilian coast. These multi-proxy data indicated a change from a flat occupied by herbs, palms, tree/shrubs to a lagoon surrounded by mangroves with an increase of sedimentary organic matter sourced from estuarine waters between ~6300 and ~4650 cal yr BP. The RSL rise caused a landward mangrove migration during the early-middle Holocene, widely recorded along the Brazilian coast. The RSL fall converted that lagoon with mangroves into a flat occupied by herbs, palms, and trees/shrubs during the middle-late Holocene. The last thousand years were characterized by a significant decrease in the mangrove pollen occurrence on highest tidal flats occupied by modern mangroves between 390 cal yr BP (1560 AD) and 77 cal yr BP (1873 AD), probably caused by a RSL fall associated with the Little Ice Age (LIA). The core G-4, sampled from the lowest tidal flats and mainly occupied by Rhizophora, revealed an increased trend in Rhizophora pollen percentage since 77 cal yr BP (1873 AD). However, cores sampled from the highest mangrove tidal flats, in the ecotone mangrove/ herbaceous vegetation, indicated an increase of pollen percentages of Rhizophora, Avicennia, and Laguncularia, suggesting a mangrove migration into the highest tidal flats previously occupied by herbs, palms, and trees/shrubs since 1958 (core G-3) and 1955 AD (core RBN-2). These trends must be related to the increase in estuarine influence by a RSL rise since the end of the Little Ice Age and intensified during the last decades.
Acesso aberto (Open Access)
Recurso polínico coletado por abelhas sem ferrão (Apidae, Meliponinae) em um fragmento de floresta na região de Manaus - Amazonas
(Instituto Nacional de Pesquisas da Amazônia, 2009-09) OLIVEIRA, Francisco Plácido Magalhães; ABSY, Maria Lúcia; MIRANDA, Izildinha Souza
The objective of this study was to characterize the resources used by Amazonian bees Melipona seminigra merrillae, Melipona fulva, Trigona fulviventris and CephaloTrigona femorata, in an urban Forest patch at Manaus city from March to October 2001. The pollen analysis determined 90 pollen types, distributed in 31 families, 67 genera and 10 palynologycal types unidentified. Trigona fulviventris was the bee species that presented the most diversified pollen types, using 58 sources in that period. The size of pollen types used were distributed as follows: T. fulviventris (58), M.s. merrilae (41), C. femorata (34) and M. fulva (25). Plant species contributing the most for the diet of the bees and presenting the highest frequencies on the pollen samples were Miconia myriantha (12,91%), Leucaena leucocephalla (9,52%), Tapirira guianensis (6,53%), Eugenia stipitata (6,22%), Protium heptaphyllum (6,17%) and Vismia guianensis (5,93%). Generally the bees concentrated their collections on a reduced number of plant species and with a differentiated degree of use for each source. Pollen types with frequency above 10% occurred in a small proportion for most months, being responsible for more than 50% of all the pollen collected every month. Pollen source used varied according to the species, T. fulviventris had a more broad and diversified diet, whereas M. fulva was the bees species that least diversified its diet. T. fulviventris presented higher uniformity on the use of pollen sources and the pollen niches overlap was higher between M.s. merrillae and M. fulva and lower between T. fulviventris and C. femorata.