Coleção de referência de fitólitos e reconstituição paleoambiental da Floresta Ombrófila Densa Altomontana no Parque Estadual Carlos Botelho - SP

Abstract

Phytolith analysis is a promising tool of interdisciplinary sciences for paleobioclimatic reconstruction purposes. Phytolith is a bioindicator (Proxy) formed from the silicification process of plant cells and/or tissues, both grasses and woody, from the absorption of monosilicic acid (H4SiO4) from the soil solute. To understand such changes, through the fossil phytolithic signal, it is necessary to have knowledge of modern phytolithic productions, for which the Reference Collections of Modern Phytoliths (RCMP) are made. Currently, there are still gaps in phytolithic data for different vegetative classes, such as the Atlantic Forest, which has different phytophysiognomies. Among them, the Altomontana Dense Ombrophilous Forest (ADOF) stands out as one of the phytophysiognomies that lack data on the production and preservation of the phytolithic assemblage. In this work 82 samples of representative species of ADOF were selected for the elaboration of the RCMP and samples were collected from a soil under it, up to 90cm deep, for purposes of paleoenvironmental reconstitution, through a multiproxy analysis (chemical and physical soil analysis, of phytoliths, δ13C and 14C dating). Of the 82 studied plant samples, 51 phytolith morphotypes were identified, representing the phytolithic diversity of ADOF, mainly marked by the presence of Spheroid psilate/ornate and Blocky psilate. The results of RCMP showed that the representative families of ADOF are abundant producers of phytoliths, with representative morphotypes of plants with woody habits, predominantly adapted to a humid environment. High redundancy was found among non-monocotyledonae species. In the soil, only 41 morphotypes were identified. The physicochemical data of the soil allowed to identify a soil with little pedogenetic development, classified as cambisol haplic, which presents, in general, good edaphic condition for the preservation of morphotypes. The morphotypes that fossilized along the profile reflected the structure of the overlying vegetation, predominantly marked by plants of arboreal/shrubby habit, marked by the most representative morphotypes of RCMP. The phytolithic indices indicated maintenance of conditions of moisture, temperature and vegetation structure similar to the current ones, throughout the formation of the soil profile. Thus, the phytolithic assemblage corroborated the δ13C data, which also indicated the presence of forest, since ~3700 years cal. AP.