Gradsects – a new approach on plant biodiversity assessment in vegetation growing on coastal sandy plains from Southeastern Brazil

Resumen

Restingas, a geomorphological local name for the sandy coastal plains, are a type of coastal tropical and subtropical ecosystem that occur on sandy, acidic, and nutrient-poor soils of eastern Brazil. It is within the Atlantic Forest, one of the hottest hotspots due to its fragmentation and for being constantly pressured by anthropic forces. We have assessed the open shrubby vegetation located in the Paulo Cesar Vinha State Park (20°33’-20°38’S e 40°26’-40°23’W) in order to know whether past sand extraction mining affects biological diversity and species richness locally or in a broader scale. We used Gradsect technique in order to determine if this approach is efficient in assessing biodiversity changes in impacted tropical ecosystems. Gradsect assesses plant functional types (PFT) without quantifying the occurrence of each PFT. Gradsect sampled 994 PFTs in a total area of 4200 m², distributed in 168 sampling unities, to find 151 species in 285 different modi. The diversity index of Shannon-Wiener (H’) was 4.65, evenness index (J) was 0.97, and Whittaker’s Index for taxa richness was 21.88. Among 121 plant genera, 93 corresponded to monospecific ones, as well as 34 among the 64 plant families were monospecific, suggesting high diversity levels. The biodiversity in the deep of the hole created by sand mining and in its slope was only significantly lower than the intermediate zone, about 300 m far from the impact point, but both of them did not differ significantly from the blocks from an adjacent area, no more than 50 m far from the impact point; from the boundaries of a marsh, and from a distant zone that was about 500 m far from the impact point.