Composição, estrutura horizontal e espacial de 16 ha de floresta densa de terra-firme no estado do Amazonas

Abstract

The predominant forest type of the Amazônia Biome, about 70%, is called terra-firme dense forest characterized mainly by high species diversity. Its floristic composition and structure are aspects that should be considered in the planning and execution of forest management and choice of appropriate silvicultural practices for their growth and development. This study sought to provide additional information to decision-making in the application of forest management techniques and/or conservation of species and analyze the spatial distribution of species of commercial interest in terra-firme dense forest in Central Amazon. This study was conducted in two areas: the Precious Woods Amazon Ltda (PWA), in Silves and the Campo Experimental do Distrito Agropecuário da Suframa (CEDAS) in Rio Preto da Eva, using 08 continuos hectares in each place. The main goals were to describe the forest composition and horizontal structure, including explicit spatial analysis. Also, we developd and test a methodology based on neighbor analysis as an auxiliar method for mother trees selection, trees to logging and also for conservation areas. From these analysis richness mapas were generated for focal species in two DAP classes (class I: DHB ≥ 10 cm and class II: DHB ≥ 40 cm). All individuos with DBH larger than 10 cm were measured in 2014 and had its UTM coordinates registered. From the list of 30 commercial species, 12 were selected for the spatial studies, having more than or equal 20 individuals. As a result, in each of the eight hectares 4.279 individuals, represented by 203 species were recorded in PWA and 5.069 individuals in 386 species in CEDAS, and 69 are unique to the PWA and 191 unique in CEDAS. The forest environment studied showed great floristic diversity, as presented by Shannon-Weaver index of 4,34 and 4,95 in the PWA and in CEDAS, respectively, supporting the high diversity estimated by the species-area curve. Among the five most abundant species in the PWA are Trattinnickia burserifolia (332 ind.), Eschweilera coriacea (168 ind.), Ocotea neesiana (167 ind.), Eschweilera collina (158 ind.) and Trymatococcus amazonicus (129 ind.) which together account for 22% of all individuals. Ocotea neesiana is the only species among the five most abundant ones that was also classified as a focal species. In CEDAS, Eschweilera bracteosa (315 ind.), Protium amazonicum (311 ind.), Eschweilera coriacea (205 ind.), Licania oblongifolia (114 ind.) and Pouteria sp.3 (111 ind.), together correspond to 21 % of the total individuals. In PWA considering the DHB ≥ 10 cm, the density of individuals was 535 ind.ha-1 and basal area was 222.3835 m2.ha-1. In CEDAS, the density of individuals and basal area were 634 ind.ha-1 and 223.0455 m2.ha-1, respectively. In the study of spatial pattern, the distribution of community, both in PWA as well in CEDAS, the Complete Spatial Randomness (CSR) was not rejected, so the predominant spatial pattern was random pattern. Considering the focal species, in PWA the CSR was rejected for two species, which were Licaria aritu and Scleronema micranthum,with pattern classified as aggregate, from the distance above 130 m. The results from the methodology based on neighbor analysis for tree selections purposes, showed its applicability for 50% of the selected species, where the richness found at the DBH Class II was not significantly different from the one found at Class I. This show that Class II can be used to represent the diversity for these species in the managment real forest situation. Then the methodology tested here is an important source of information, not only for studies in the permanet parcels, but also for the monitoring of the changes in species composition over time, after logging, among other studies.