Reference collections of plant communities from "Restinga" of the coastal plain of Maricá, Rio de Janeiro, Brazil

Abstract

This chapter has the purpose to make reference collections of silicophytoliths from current plant communities of the zone transformed into Environmental Protection Area in the coastal plain of Maricá, Rio de Janeiro, Brazil; to contribute to the study of paleobiogeoclimatic reconstruction and evolution of the area along the Quaternary. For this, we identified the different geomorphological units and the plant communities that conforms the restinga. Samples of the leaves of some of the species of each community were taken and silicophytoliths were obtained by the technique of calcination. The ashes were mounted on inmersion oil and analyzed by optical microscope. This coastline presents two sand ridges (the external from Holocene, the internal from Pleistocene) separated by a depression where there is a freshwater marsh originated by upwelling of the water table. The following plant communities were delimited: a) Halophile-psamophile: adapted to saline and sandy conditions subject to tidal influence, with predominance of herbaceous and creeping species; b) Scrub: open vegetation forming thickets; c) Herbaceous marsh: between the two sand ridges, with predominance of Poaceae and Cyperaceae; d) Slack: with creeping vegetation; e) Shrubby vegetation on the shore of Maricá lagoon: more disturbed area, with a higher incidence of invasive species; f) Dry forest: with an arboreal structure well developed, without dominant species. Silicophytoliths were identified in: a) Halophile-psamophile community: Sporobolus virginicus, Poaceae (predominant morphotype horned tower), Stenotaphrum secundatum, Poaceae (main morphotypes bilobates and crosses), Remirea maritima, Cyperaceae (especially cone shaped); b) Scrub: Clusia lanceolata, Clusiaceae (predominant morphotype globular psilate), Allagoptera arenaria, Arecaceae (globular echinate); c) Dry forest: Astrocaryum aculeatissium, Arecaceae (conical silicophytoliths). In other plants such as Ipomoea pes-caprae (Convolvulaceae), Alternanthera maritima (Amaranthaceae), Heteropteris chrysophylla (Malpighiaceae), Smilax spinosa (Smilacaceae), Neoregelia cruenta (Bromeliaceae) and Clusia aff. fluminensis (Clusiaceae) no silicophytoliths were observed. The coastline of Maricá has been undergoing a disordered occupation process, affecting ecosystems and modifying its landscape. We hope that studies about vegetation dynamics in the region will contribute, besides paleoclimate studies, to its sustainable development.