Structure of a disturbed mangrove in the Rio Parnaíba delta, Piauí, northeast Brazil

Phytosociological analysis was used to quantify the structure of a disturbed mangrove next to a tidal creek of the Rio Igaraçu, Piauí, northeast Brazil, and comparison was made with a survey made fourteen years earlier. Thirty 10×10 m plots were demarcated in three areas of ten plots each. Height and circumference of trees of circumference at breast height ≥ 15 cm were measured in 285 individuals of Avicennia germinans (L.) L., Laguncularia racemosa (L.) C.F.Gaertn. and Rhizophora mangle L. Height ranged from 1.5−15 m (mean 4.4 m) and diameter from 4.8−28.7 cm (mean 7.2 cm). Avicennia and Laguncularia showed the highest parameter values (importance values 52% and 44%, respectively). Furthest from the creek and subject to less frequent tidal flooding, only Avicennia occurred, shorter (mean height 3.8 m) and fewer (density 130 ind ha−1) than elsewhere. In the central area (density 1240 ind ha−1) Avicennia dominated Laguncularia (importance values 53% vs. 47%). All species occurred nearest the creek (density 1480 ind ha−1, importance values Laguncularia 47%, Avicennia 46%, Rhizophora 7%), and heights and diameters were lower. Changes from a previous study suggest selective logging of larger individuals nearer the creek, especially Rhizophora, favouring regeneration of Laguncularia.