Registros polínicos para o Holoceno tardio da região da Campanha (Rio Grande do Sul, Brasil) e seu significado na história dos paleoambientes da Savana Estépica Parque

Abstract

-POLLEN RECORDS FOR LATE HOLOCENE IN THE CAMPANHA REGION (RIO GRANDE DO SUL, BRAZIL) AND THEIR SIGNIFICANCE IN THE HISTORY OF THE PALEOENVIRONMENTS IN THE "SAVANAESTÉPICA PARQUE". This paper presents palynological results from an outcropping section located in the Brazilian side of the Quaraí river (30°16'27.9"S/57°26'33.6"W), south of the Barra do Quaraí city, westernmost portion of the Rio Grande Sul State, as well as from 15 surface samples collected in the 'Parque do Espinilho' (PESP), in order to obtain current pollen spectrum. A total of 81 types of palynomorphs (pollen and non pollen) was identifi ed in the ten fertile samples from the outcropping section and 114 taxa from surface samples. Pollen diagrams were performed in order to identify current pollen spectrum and reconstruct the vegetational history of the "Savana Estépica Parque" during the late Holocene in this region, supported by radiocarbonic datings and granulometry analysis. Results indicate that between 3,380 ± 25 and 2,350 ± 25 14 C yr BP, area was composed by a fl oodplain covered with grasses that formed bodies of water with little depth enabling the development of algae colonies. Between 2,328 and 2,262 yr BP (interpolated age) occurred a decrease in humidity and the temperature rise, as suggested by the disappearance of algae and the bryophytes increasing. Between 2,130 (interpolated age) and 1,940 ± 20 14 C yr BP was recorded an increasing of the humidity, refl ected by the high diversity of arboreal taxa, with expansion of the "Mata Ciliar". Granulometrical data corroborate palynological results. Pollen spectra of surface samples refl ected the different current vegetation types of the PESP.Key words: 'Parque do Espinilho', Pampa Biome, vegetational reconstitution, Quaternary, Quaraí River. RESUMO -Este trabalho apresenta os resultados palinológicos de dez amostras de um afl oramento localizado na margem brasileira do rio Quaraí (30°16'27,9"S/57°26'33,6"W), ao sul do município de Barra do Quaraí, extremo oeste do Estado do Rio Grande do Sul, bem como de 15 amostras superfi ciais no Parque do Espinilho (PESP) para obtenção do espectro polínico atual. Foram identifi cados 81 tipos de palinomorfos (polínicos e não polínicos) nas amostras sedimentares do afl oramento e 114 nas amostras superfi ciais. Análises a partir dos diagramas polínicos foram realizadas com objetivo de identifi car o espectro polínico atual e reconstituir a história paleovegetacional da Savana Estépica Parque durante o Holoceno tardio da região, apoiadas por datações radiocarbônicas e análises granulométricas. Os resultados indicam que entre 3.380 ± 25 e 2.350 ± 25 14 C anos AP a área era composta por uma planície de inundação recoberta por poáceas que formava corpos d'água de pequena profundidade, possibilitando o desenvolvimento de colônias de algas. Entre 2.328 e 2.262 anos AP (idade interpolada) observa-se diminuição da umidade e aumento de temperatura, evidenciado pelo desaparecimento das algas e maior frequência de esporos de briófi tas. Entre 2.130 ano...

Grazing Changes the Soil-Plant Relationship in the Tree-Regeneration Stratum in the Pampa of Souhtern Brazil

“…The area is situated on quaternary lands of the morphostructural domain of the Bacia Sedimentar do Paraná (ALVES, 2012), in the geomorphological province of Cuesta del Haedo, where volcanic spills of the Serra Geral formation are associated to sandstones of the Botucatu formation, and the sedimentary deposits are represented by the Guterres alloformation and the Touro Passo formation (EVALDT et al, 2014). Chernossolos Ebânicos Carbonáticos vertissólicos are found in the western part of the state (STRECK et al, 2008).…”