Forest community studies traditionally investigate arboreal structure and composition. Herb-shrub layers have little or no importance in these works. Initial information on herb-shrub layers of Brazilian forests was provided as a complement to arboreal studies. However, herb-shrub layers have recently gained a central importance in some works. The main objective of this study was to describe the phytosociological structure of the Silvicultura forest's herb-shrub layer to understand the synecological relations and study the populational dynamic processes involved. The phytosociological parameters used were obtained from 1 m² split plots of 100 m² samples. All individuals with less than 10cm PBH (perimeter at breast height) or over 20 cm were sampled. Dynamic processes were evaluated by using the size frequency distribution of sampled populations. The herb-shrub phytosociological structure consisted of 1193 individuals of 109 species of 41 families in samples of 100 m². The Shannon diversity index (H') was equal to 3.38 nats/individual and the equability (J') was equal to 0.72, both showing high heterogeneity under herb-shrub conditions. The most important species (VI) were Piper lucaeanum, Psychotria conjugens, Olyra micrantha, Psychotria sessilis, Siparuna guianensis, Bambusa tuldoides, Ottonia leptostachya, Aparisthmium cordatum and Psychotria hastisepala. The most important (VI) families were Rubiaceae, Piperaceae, Poaceae, Monimiaceae, Leguminosae (Mimosoideae), Myrtaceae, Euphorbiaceae, Meliaceae, Lauraceae and Flacourtiaceae. The size frequency distribution analysis raised the hypothesis that there were two species groups, with different strategies. One group would consist of species allocating photosynthates preferentially to their photosynthetic system, and the other group of species allocating photosynthates preferentially to their trunks.
Regeneration; understory structure; size structure
