Tree species compositional change and conservation implications in the white‐water flooded forests of the Brazilian Amazon

Abstract

Aim The aim of this study was to use compositional changes in tree species along the Amazon River floodplain in Brazil to identify and characterize biogeographic regions that would serve as broad surrogates for conservation planning.Location The main course of the Amazon River in Brazil, covering a river distance of approximately 2800 km.Methods Two sampling methods were employed at specific sites: standardized transects and/or individual‐based samples. Seventy‐three samples were collected from 26 sites at approximately 100‐km intervals along the floodplain. Biogeographic regions were identified by non‐metric multidimensional scaling (NMDS) ordination and by a hierarchical cluster analysis. The relative influence of environmental components (flood depths, annual rainfall, and length of the dry season) on tree species composition and one spatial component (longitude) were analysed by multiple regressions against a one‐dimensional NMDS ordination axis.Results Based on tree species composition, three main biogeographic regions were identified: a western region between Tabatinga and the Negro River confluence; a central region from the Negro River confluence to the Xingu confluence; and an estuarine region from the Xingu confluence to Santana. The regions identified were consistent using different data sets and analytical techniques. Mixed environmental and spatial effects explained most of the variation, but the spatial effect alone had a greater influence on species composition than environmental effects alone.Main conclusions The regions delimited in the analyses differed from those based on geomorphology or World Wildlife Fund (WWF) ecoregions. These results reinforce the need for surrogates to be tested against biological data before they are used to shape approaches to conservation planning. Although a protected area coverage of 25% gives the impression of extensive conservation management on the floodplain, less than 1% of the Amazon’s floodplain in Brazil is strictly protected. The significant compositional differences between regions and the strong spatial variation along the Amazon indicate that strict protection areas should be distributed much more evenly within and between regions.

Distribution and β‐diversity of tree species in igapó forests (Negro River basin, Brazilian Amazon)

“…When we compared these results with those obtained in várzea forests, Albernaz et al. () found that Fabaceae (20.29%), Annonaceae (6.08%), Sapotaceae (4.80%), Moraceae (4.79%) and Lauraceae (3.32%) were the richest families, representing almost 40% of the species richness. In terra firme of the Central Amazon, Emidio da Silva et al.…”

“…Flooded forests cover more than 800,000 km 2 of the Amazon lowlands during the high‐water season (Melack & Hess, ) but have been sparsely studied compared with “terra firme” forests. This periodic flooding exerts a strong influence on the structure and composition of plant species, which continuously change along the river channel (Albernaz et al., ; Luize, Silva, Wittmann, Assis, & Venticinque, ; Rosales, Petts, & Knab‐Vispo, ; Wittmann, Junk, & Piedade, ). Forests flooded with white or muddy water, such as water from the Solimões River, are referred to as “várzea” (Sioli, ), while those flooded by black and acidic water, such as that of the Negro River, or by clear water, such as that from the Tapajós River, are referred to as “igapó” (Kubitzki, ; Prance, ).…”

Floristic impoverishment of Amazonian floodplain forests managed for açaí fruit production

“…Less than 1% of the Amazon's floodplain estuarine in Brazil is strictly protected (Albernaz et al, 2012) and our study area is designated as an 'extremely high' priority area for conservation initiatives by the Brazilian government (MMA, 2007). Our results emphasize the need to reinforce the protected area network along the main stem Amazon river and the lower reaches of its tributaries to include areas which do not permit any extractive activities that alter the forest physiognomy.…”

Genetic diversity and structure of Astrocaryum jauari (Mart.) palm in two Amazon river basins

“…These seasonal floodings have led to the adaptation of A. jauari and other species to ensure survival when partially or totally submersed during those phases (Piedade et al 2006). The distribution of A. jauari and other plants adapted to this habitat varies according to flooding regimes and seasonality, precipitation patterns around the hydrographic basins and due to evolutionary geographical events, defined by the effect of sediment deposition and erosion on changes in river courses (Albernaz et al 2012).…”