Structure and Floristic Composition of Flood Plain Forests in the Peruvian Amazon I. Overstorey

Three Peruvian flood plain forests adjacent to the Ucayali river were sampled using nine 1 ha permanent sample plots in which stems exceeding 10 cm DBH were identified and measured. These plots were measured four times during 1993-1997. Three plots were established in each of the three forest types high restinga, low restinga, and tahuampa, characterised in part by an annual inundation of one, two and four months per year, respectively. Stem density varied from 446 to 601 per hectare, and the basal area ranged between 20 and 29 m2/ha. A total of 321 species were recorded in the nine hectare sample, with 88-141 species in each 1 ha plot. Species composition indicated a relatively low similarity between the forest types. Plots with the longest flooding contained the most species, expressed both as per unit area as well as per 1000 stems. The flood plain forests contained fewer tree species than adjacent non-flooded terra firme forest. Family importance values were calculated for each forest. In all three forests Leguminosae, Euphorbiaceae, Annonaceae and Lauraceae were important. The Moraceae family was conspicuous in both high restinga and low restinga. The Arecaceae and Meliaceae were notable in high restinga, as was Rubiaceae in low restinga. Lecythidaceae, Sapotaceae and Chrysobalanaceae exhibited relatively high values in the tahuampa forest. High species importance values were obtained for Maquira coriacea, Guarea macrophylla, Terminalia oblonga, Spondias mombin, Ceiba pentandra, Hura crepitans, Eschweilera spp., Canipsiandra angustifolia, Pouteria spp., Licania micrantha, Parinari excelsa and Calycophyllum spruceanum. Among the species of smaller stature, Drypetes amazonica, Leonia glycicarpa, Theobroma cacao and Protium nodulosum attained high values