Woody plant subregions of the Amazon forest

Abstract

1. The Amazon forest covers 7.5 million km 2 in nine countries, hosts 25% of the global biodiversity and is a major contributor to the biogeochemical and climatic functioning of the Earth system. Despite its global importance, a regionalization of the Amazon tree flora is still lacking. Clear and data-driven delimitation of subregions is important for macroecological studies, to the identification of metacommunities and is a requisite for conservation planning. 2. We aimed at identifying and mapping plant species subregions and investigated their relationships with environmental, historical and human correlates. We provide the first woody plant regionalization of the entire Amazon forest using a datadriven approach based on assemblage composition patterns. 3. We compiled data on woody species composition from 301 assemblages based on species occurrences. We then used unconstrained ordination, interpolation and clustering techniques to identify and map discrete woody subregions. Hierarchical clustering analysis was conducted in order to investigate the relationships between the identified subregions. We used multinomial logistic regression model and deviance partitioning to investigate the influence of environmental, historical and human factors on subregions distribution. 4. We identified 13 woody subregions in the entire Amazon forest. The hierarchical subregion classification showed a broad Andean-Cratonic east-west division. Variation in subregions was explained jointly by human factors and spatial structure followed by environmental factors and spatial structure combined. 5. Synthesis. Our woody plant subregions differed from World Wildlife Fund ecoregions and physiognomic-based maps, highlighting the importance of basing regionalizations on taxon-specific groups and confirming that vegetation maps should not be used as proxies to plant diversity subregions. Our findings also confirm the need for multiple and extensive protected areas in the Amazon forest. The relevance of current climate factors in our study alerts to a profound impact that climate change could have on the spatial organization of the Amazon flora.

On the floristic identity of Amazonian vegetation types

“…In contrast, the other seven vegetation types have a low proportion of species restricted to them, ranging from 6% in coastal mosaics and savanna s.s. to 25% in tepuis. Species shared between terra Moreover, because these edaphic gradients are consistently important in segregating Amazonian vegetation types from local to continental scales, our results run counter to previous findings which have suggested that tree community composition in the Amazon is primarily driven by Amazon-wide gradients in environmental conditions (e.g., precipitation seasonality, soil fertility; Silva-Souza & Souza, 2020;ter Steege et al, 2006). Previous Amazon-wide studies analyzed tree species composition data without separating or considering the different Amazonian vegetation types.…”

“…Previous Amazon-wide studies analyzed tree species composition data without separating or considering the different Amazonian vegetation types. If composition is summarized within geographic grid cells (e.g., Silva-Souza & Souza, 2020;ter Steege et al, 2006), then a given grid cell may take on Values under NMDS1 and NMDS2 represent the coefficients of determination (adjusted R 2 , and their respective p-values) of generalized linear models (GLMs) between the first two axes of a non-metric multidimensional scaling and environmental variables. Values in the last row represent coefficients of determination of GLM-based multiple regressions between each NMDS axis and all significant variables.…”

Mapping functional tree regions of the Atlantic Forest: how much is left and opportunities for conservation

“…The CWM traits of specific leaf area (mm 2 mg -1 ), leaf dry matter content (g g -1 ), leaf nitrogen content (mg g -1 ), leaf thickness (mm), wood density (g cm -3 ), seed dry mass (mg) and maximum plant height (m) were computed based on abundance data regarding 2122 species distributed across 281 local communities. Community data were compiled from bibliographic sources and organized into the Caaporã database, which has been used in a number of recent publications on macroecological patterns of Brazilian and South American biomes (Cantidio & Souza 2019, Silva-Souza & Souza 2020, Silva et al 2021b. Further details on the use of this database in the Atlantic Forest can be found in Cantidio and Souza (2019) and Silva et al (2021b).…”

“…The ISODATA algorithm works by clustering n groups of pixels with similar spectral characteristics in the input bands from two until the maximum number of clusters is reached in order to find the best solution for the clusters (Memarsadeghi et al 2007). This requires the suggestion of an initial maximum number of clusters, which was determined using the L-method with 1000 iterations (Salvador & Chan 2004) following previous studies (Moura et al 2016, Cantidio & Souza 2019, Silva-Souza & Souza 2020. The L-method is a Euclidean-based procedure running piecewise regressions on repeated k-means partitions applied on a dissimilarity matrix of CWM traits (Salvador & Chan 2004).…”

Functional and taxonomic responses of tropical moth communities to deforestation

“…The study areas are distant from each other by 120 and 230 km, respectively, and were all originally covered by the same type of tropical rainforest (Xingu/Tocantins/Araguaia and Tocantins/Pindare moist forests; Silva-Souza & Souza, 2020) within the Belém centre of endemism (Cardoso Da Silva et al, 2005).…”