Structure and Floristic composition of Flood plain forests in the Peruvian Amazon 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 forests 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 forms closed high canopy forests with presence of emergents. A total of 25 permanent sample plots covering 0.64 ha were established. They were nested within six quadratic 1 ha permanent sample plots where large individuals (>10 cm DBH) were inventoried. Overall average density and basal area of the understorey were 4458 ha and 5.0 m2 /ha, respectively. The families of Moraceae, Leguminosae, Annonaceae, Euphorbiaceae, and Lauraceae were among the most important tree families, while important shrub and small tree families were Violaceae, Rubiaceae, Melastomataceae, and Olacaceae. Two hundred eight and 204 tree species were registered in the restinga forest overstories and understories, respectively. Fifty-six percent of the species were shared between the two forest strata, while around 22% were confined to each of them. Species present only in the understorey were predominantly shrubs or treelets, while some of the species with a presence only in the overstorey were probably early succession species about to disappear from the forests