Análise florística e estrutural de uma área de manejo florestal no Amazonas: estudo de caso de Mezilaurus itauba (Meisn.) Taub. ex Mez

Abstract

The Amazon rainforest is the largest tropical rainforest reserve the world and because of its extension and the complexity associated with forest inventories, it has many gaps about its knowledge. In order to increase this knowledge, characterization and analysis of the horizontal structure of the tree vegetation community in “terra firme” forest in the Itacoatiara, Silves and Itapiranga region, in the state of Amazonas (AM) was carried out. It is an area of concession of forest management belonging to Precious Woods Amazon company. The data used are derived from forest inventory, carried out in 2010 by the Forest Management Laboratory (LMF) team located at the National Institute of Amazonian Research (INPA). There were 14,426 arboreal individuals, distributed in 236 species, 157 genera and 55 botanical families. From these individuals, 4,835 were determined at specific level, 8,098 at generic level, 1,288 only as a family, 175 only by popular name and 30 samples have no identification. The families with the greatest genera diversity were: Fabaceae (26), Euphobiaceae (10), Annonaceae (7), Apocynaceae (7) and Arecaceae (7). The five families that presented the highest number of individuals were: Sapotaceae (1,908), Lecythidaceae (1,759), Burseraceae (1,414), Fabaceae (1,380) and Lauraceae (1,056) a total of more than 52% of the individuals sampled. Such families were followed by Chrysobalanaceae (753), Arecaceae (707), Annonaceae (666), Euphorbiaceae (516) and Moraceae (472). The ten mentioned families totalize approximately 80% of the individuals found in the area. On the other hand, Ebenaceae, Calophyllaceae, Ochnaceae and Bixaceae contributed with only one individual each. The species accumulation curves (collector curve) for both species and botanical families showed that the samplings were sufficient to characterize the floristic composition of the study area. With the inclusion of the last 12 plots (10% of the sampled area), there was an increase of only six species (1.9% of area wealth) and only one new botanical family (0.6%). It was possible to observe the formation of two groups with similarity around 45% by the grouping method UPGMA. No association between these two groups was observed within the years of the exploration, however, there is a clear relationship between the groups and the species richness. The diversity of the study area, according to the Shannon index (H '), was of 4,12 ± 0,08 demonstrating a great diversity of species in comparison with other studies realized in the Amazon. The diameter distribution of the individuals followed the typical pattern found in tropical natural forests, called "Reverse J". In this dissertation, a case study was also carried out with the species Mezilaurus itauba, included in the list of endangered species of IUCN. The objective was to verify if the identified trees in the forest inventory to the name of M. itauba corresponded exactly to this species or to others and how many species were included in this identification. Collections of botanical material from the specimens cited by the loggers as M. itauba were carried out to confirm the identification. A total of 72 samples were obtained, of which 40% were of the species M. duckei (29 individuals), 38% of M. itauba (27 ind.), 18% of M. synandra (13 ind.), Licaria sp 1. (3%) and Licaria sp 2. (1%). The diameter distribution of the individuals of Mezilaurus spp. also followed the negative exponential pattern, but the first two classes showed very similar values. According to the criteria of IUCN (2001) M. synandra should be considered Least Concern (LC), because it presents a wide distribution and in different habitats in Brazil. Mezilaurus duckei is restricted to the state of Amazonas and despite the contribution of the present study, it still has few collections. Due to its narrow distribution, it needs further study, and the species should be considered as Data Deficient (DD). The M. itauba species should no longer be considered Vulnerable (VU) and should be categorized as Least Concern (LC), since it has a wide distribution in Brazil and other Amazonian countries.