Taxonomia e fitossociologia da vegetação arbustivo-arbórea de dunas na restinga da Vila Bonifácio, Ajuruteua, Bragança, Pará

Abstract

In the Amazon region, formations of coastal vegetation on sandy soils {restinga) cover an area of approximately 1000 km2. In contrast to the restinga vegetation of southern and southeastern Brazil, restinga vegetation in the north of the country is not well known. This study presents a description of the woody vegetation of restinga dunes and the relationship between floristics, vegetation structure and topography near Vila Bonifácio, Ajuruteua península, Pará. A key to the woody species of the Vila Bonifácio restinga is presented as well as a short summary of the characters important for the identification of each species. The study site features a complex of dune ridges within an area of marshes, surrounded by mangroves. Vegetation structure was investigated along 4 transects of 10 m width and lengths of 100-170 m, each crossing obliquely the same dune ridge. Begin and end of ali transects were localized within the marsh-dune ecotone on either side of the transect. Elevation and influence of tidal inundation were documented along topographic profiles across each transect. Within transects, basal diameter, height as well as length of prostrate stem portions of ali trees and shrubs with a basal stem diameter >2.5 cm were recorded. If possible, fertile shoots of each occurring species were collected and deposited in local and regional herbaria. 15 woody plant species were identified within the sampling area, 3 additional species were found outside the transects. The species with the highest importance value was Pouteria ramiflora (Sapotaceae); other important constituents of the dune vegetation were members of Myrtaceae {Myrcia cuprea. Eugenia flavescens) and Arecaceae (Aslrocaryum sp.). Most plants were small trees or shrubs, with the notable exception of Humiria balsamifera (Humiriaceae) and P. ramiflora, reaching stem diameters of about 30 cm and heights >10 m in some parts of the area. The total basal area of ali transects accounted to 9.9 nr-ha'1, the overall tree density was 2.293,48 individuals-ha'1. Large stem diameters of P. ramiflora were only encountered at low elevation; similarly, height of P. ramiflora, Protium heptaphyllum and Ouratea ssp. was reduced at higher elevations. No convincing relationship between density and elevation was detected. The species inventory of Vila Bonifácio overlaps with that of the small number of other well-known restingas along the coast of Pará but future, more detailed surveys are necessary to arrive at a conclusive characterisation of the restinga flora of this state.