Floristic composition and similarity of 15 hectares in Central Amazon, Brazil

The Amazon region is one of the most diverse areas in the world. Research on high tropical forest diversity brings up relevant contributions to understand the mechanisms that result and support such diversity. In the present study we describe the species composition and diversity of 15 one-ha plots in the Amazonian terra firme dense forest in Brazil, and compare the floristic similarity of these plots with other nine one-ha plots. The 15 plots studied were randomly selected from permanent plots at the Embrapa Experimental site, Amazonas State in 2005. The diversity was analysed by using species richness and Shannon’s index, and by applying the Sorensen’s index for similarity and unweighted pair-group average (UPGMA) as clustering method. Mantel test was performed to study whether the differences in species composition between sites could be explained by the geographic distance between them. Overall, we identified 8 771 individuals, 264 species and 51 plant families. Most of the species were concentrated in few families and few had large number of individuals. Families presenting the highest species richness were Fabaceae (Faboideae: 22spp., Mimosoideae: 22spp.), Sapotaceae: 22spp., Lecythidaceae: 15 and Lauraceae: 13. Burseraceae had the largest number of individuals with 11.8% of the total. The ten most abundant species were: Protium hebetatum (1 037 individuals), Eschweilera coriacea (471), Licania oblongifolia (310), Pouteria minima (293), Ocotea cernua (258), Scleronema micranthum (197), Eschweilera collina (176), Licania apelata (172), Naucleopsis caloneura (170) and Psidium araca (152), which represented 36.5% of all individuals. Approximately 49% of species had up to ten individuals and 13% appeared only once in all sampled plots, showing a large occurrence of rare species. Our study area is on a forest presenting a high tree species diversity with Shannon’s diversity index of 4.49. The dendrogram showed two groups of plots with low similarity between them (less than 0.25), and the closer the plots were one to another, more similar in species composition (Mantel R=0.3627, p<0.01). The 15 plots in our study area share more than 50% of their species composition and represent the group of plots that have the shortest distance between each other. Overall, our results highlight the high local and regional heterogeneity of environments in terra firme forests, and the high occurrence of rare species, which should be considered in management and conservation programs in the Amazon rainforest, in order to maintain its structure on the long run. Rev. Biol. Trop. 59 (4): 1927-1938. Epub 2011 December 01.

La región amazónica es una de las más diversas áreas del mundo. Los estudios sobre la gran diversidad de bosques tropicales generan contribuciones relevantes en la comprensión de los mecanismos que originan y apoyan tal diversidad. En el presente estudio se describe la composición de las especies y la diversidad de 15 parcelas de una hectárea en el bosque denso amazónico terra firme en Brasil, y compara la similitud florística de estas parcelas con otras nueve parcelas de una hectárea. Las 15 parcelas estudiadas fueron seleccionadas al azar, en el 2005, de parcelas permanentes en el sitio experimental de Embrapa, Estado de Amazonas. La diversidad fue analizada utilizando la riqueza de especies y el índice de Shannon, así como el índice de Similitud de Sorensen; y como método de agrupación se utilizó el promedio no ponderado por grupo (UPGMA). La prueba de Mantel se llevó a cabo para estudiar si las diferencias en la composición de especies entre los sitios podrían ser explicadas por la distancia geográfica entre ellos. En general, se identificaron 8 771 individuos, 264 especies y 51 familias de plantas. La mayoría de las especies se concentraron en pocas familias y pocas tenían un gran número de individuos. Las familias que presentaron la mayor riqueza de especies fueron: Fabaceae (Faboideae: 22spp, Mimosoideae: 22spp), Sapotaceae: 22spp, Lecythidaceae: 15 y Lauraceae: 13. Burseraceae tuvo el mayor número de individuos con un 11.8% del total. Las diez especies más abundantes fueron: Protium hebetatum (1 037 individuos), Eschweilera coriacea (471), Licania oblongifolia (310), Pouteria minima (293), Ocotea cernua (258), Scleronema micranthum (197), Eschweilera collina (176), Licania apelata (172), Naucleopsis caloneura (170) y Psidium araca (152), que representó un 36.5% de todos los individuos. Aproximadamente en el 49% de las especies se encontraron hasta diez individuos, mientras que el 13% de las especies apareció sólo una vez en todas las parcelas de muestreo, lo que demuestra una alta presencia de especies raras. La zona de estudio se encuentra en un bosque con alta diversidad de especies de árboles, con un índice de diversidad de Shannon de 4.49. El dendrograma mostró dos grupos de parcelas con baja similitud entre ellas (menos de 0.25), y entre más cercanas las parcelas, más similares en composición de especies fueron (Mantel R=0.3627, p<0.01). Las 15 parcelas en nuestra área de estudio compartieron más del 50% de su composición de especies y representaron el grupo de parcelas con la menor distancia entre ellas. En general, nuestros resultados ponen de manifiesto la alta heterogeneidad local y regional de los ambientes de los bosques de terra firme, y la gran concurrencia de especies raras, lo cual debe ser considerado en los planes de manejo y conservación de la selva amazónica, con el fin de mantener su estructura a largo plazo.

Influência do hábitat na estrutura da comunidade de macroinvertebrados aquáticos associados às raízes de Eichhornia crassipes na região do Lago Catalão, Amazonas, Brasil / Influence of habitat on community structure of macroinvertebrate associated with roots of Eichhornia crassipes in the Lake Catalão, Amazonas, Brazil

Por possuírem ciclos de vida curtos, os macroinvertebrados aquáticos podem responder rapidamente às modificações ambientais, alterando a estrutura das suas populações e comunidades. O objetivo deste estudo foi determinar se há relação entre a composição de macroinvertebrados aquáticos associados a bancos de Eichhornia crassipes o gradiente de condutividade elétrica da água e a biomassa das raízes destes bancos. No pico da cheia de 2005, 21 bancos de macrófitas aquáticas flutuantes dominados por E. crassipes foram amostrados no rio Negro (baixa condutividade < 30 µS cm-1), na confluência entre os rios Negro e Solimões (média condutividade > 30 µS cm-1 e < 50 µS cm-1), e no rio Solimões (alta condutividade > 50 µS cm-1). Foram encontrados 1707 macroinvertebrados aquáticos, distribuídos em 14 ordens e 35 famílias. A abundância de invertebrados aquáticos foi maior em bancos na confluência das águas. O aumento da biomassa das raízes de E. crassipes levou a um aumento da abundância e da riqueza de famílias de macroinvertebrados. A abundância dos coletores-catadores, coletores-filtradores e raspadores variou com o tipo de água, e apenas a abundância dos coletores-catadores e coletores-filtradores variou em função da biomassa das raízes. A riqueza de famílias dos raspadores variou em função do tipo de água. A organização da comunidade depende do gradiente de biomassa de raízes, indicando a importância da estrutura do hábitat para o estabelecimento dos macroinvertebrados.

Owing to their short life cycles aquatic macroinvertebrates may quickly respond to environmental modifications by changing the structure of their populations and communities. The aim of this study was to determine the relationship between the composition of aquatic macroinvertebrates associated with Eichhornia crassipes stands, the gradient of water conductivity and biomass of the roots of these stands. At the peak of the floods of 2005, 21 banks of floating aquatic macrophytes dominated by E. crassipes were sampled in the Solimões River (high conductivity > 50 µS cm-1), the confluence of these the rivers Solimões and Negro (medium conductivity > 30 µS cm-1 and < 50 µS cm-1) and Negro River (low conductivity < 30 µS cm-1). A total of 1707 aquatic macroinvertebrates were found, divided into 14 orders and 35 families. The abundance of aquatic invertebrates was higher in stands in the rivers confluence. The increased biomass of roots of E. crassipes led to an increase of abundance and richness of families of macroinvertebrates. The abundance of collector-gatherers, filter feeders and collector-scrapers varied with the type of water; only the abundance of collector-gatherers and collector-filter-varied with the root biomass. The abundance of collector-gatherers, filter feeders and collector-scrapers varied with the type of water, and only the richness of collectors and filter feeders varied with the root biomass. The family richness of collector-scrapers varied with the type of water. The organization of the community depends on the gradient of root biomass, showing that habitat structure is an important factor for the establishment of macroinvertebrates.