Structure and floristic composition of flood plain forests in the PeruvianAmazon II. The understorey of restinga forests

Structure and floristic composition of small trees and shrubs (1.5 m height to 10 cm diameter at breast height was described in two flood plain forest s of the lower Ucayali river, Peruvian Amazon. The forests were of the high and low restinga type, on an annual average flooded around 1 and 2 months, respectively. The soils were nutrient rich entisols, and the vegetation fo rms closed high canopy forests with presence of emergents. A total of 25 pe rmanent sample plots covering 0.64 ha were established. They were nested wi thin six quadratic 1 ha permanent sample plots where large individuals grea ter than or equal to 10 cm DBH) were inventoried. Overall average density a nd basal area of the understorey were 4458 ha and 5.0 m(2)/ha, respectively . The families of Moraceae, Leguminosae, Annonaceae, Euphorbiaceae, and Lau raceae were among the most important tree families, while important shrub a nd small tree families were Violaceae, Rubiaceae, Melastomataceae, and Olac aceae. Two hundred eight and 204 tree species were registered in the restin ga forest overstories and understories, respectively. Fifty-six percent of the species were shared between the two forest strata, while around 22% wer e confined to each of them. Species present only in the understorey were pr edominantly shrubs or treelets, while some of the species with a presence o nly in the overstorey were probably early succession species about to disap pear from the forests. (C) 2001 Elsevier Science B.V All rights reserved.