DinÃmica vegetacional e climÃtica holocÃnica da Caatinga, na regiÃo do Parque Nacional do Catimbau, BuÃque - PE

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The main objective of the present work was to describe the Holocene dynamics of the Caatinga vegetation, in the region of the National Park of Catimbau, BuÃque, PE, Brazil. Palynological analyses were carried out from clay, rich in plant organic-matter, deposited on the low slopes of the Serra do JerusalÃm, in the Brejo de SÃo Josà Farm (8 32â 45ââS, 37 13â 14ââW) and four radiocarbon datings were obtained, aiming at quantifying the variation and density of pollen grains along an interval within the Holocene, and establishing their relation to climatic variations. Samples were taken at every 10 cm, from a trench open in sediment with 1.10 m of depth. Based on pollen types identified through comparison to the elements of the actual flora, and statistical analyses carried out using the subprogram for statistics, similarity and cluster analysis CONISS (Grimm,1987), within the software Tilia/Tilia Graph. three polinical zones were established, described in pollen diagrams of concentration and percentages of the main taxa, including trees, shrubs, lianas, aquatic herbs, algae and spores, along the studied profile. These results allowed inferring modifications of sedimentation rates, composition and distribution of the flora during the Holocene, from 8,410 + 40 years BP to Present in the region, associated with humidity variation. Local conditions were humid throughout the profile, but around 2,150 + 40 years BP an increase on sedimentation rate, on the percentage of the aquatic angiosperm Nymphaea and of the algae Mougeotia, Debarya and Zignema suggest greater humidity, possibly promoted by a period of more intense precipitation. Since ca. 1,649 years BP to Present, polinical compositions resembles the actual vegetation, with local characteristics, because, even though the area is within a semi-arid climate, the elements Anthoceros, Cyathea, Spores Monoletes, Mougeotia and Zignema are frequent, typical from humid environments. High humidity rates observed in the area are possibly related to various local factors, although they possibly reproduce moist conditions of a broader scale. The fact that the area lies within the lowest slopes of an arenitic plateau, which acts as a caption for recharge of underground-water, its proximity to the geological contact with crystalline rocks along the border of the Sedimentological Jatobà Basin or the association to faults or fractures, allowing water flow, possibly has favored the preservation and maintenance of the vegetation, with a high humidity gradient within the semi-arid. Area occupation and anthropogenic transformations on vegetation are recorded since ca. 4,500 years BP, as suggested by the presence of Orbignya (babaÃu palm), an exotic element for this region. At around 2,440 years BP up to ca. 1,694 years BP, records of elements with aquatic habits and typical from humid environments suggest moister conditions, which can have led to an expansion of the process of area occupation by groups of humans

ASSUNTO(S)

pernambuco palynology caatinga holoceno palinologia caatinga holocene pernambuco geociencias

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