Using tree species inventories to map biomes and assess their climatic overlaps in lowland tropical South America

Abstract

Aim To define and map the main biomes of lowland tropical South America (LTSA) using data from tree species inventories and to test the ability of climatic and edaphic variables to distinguish amongst them. Location Lowland Tropical South America (LTSA), including Argentina, Bolivia, Brazil, Ecuador, Paraguay, Peru and Uruguay. Time period Present. Major taxa studied Trees. Methods We compiled a database of 4,103 geo‐referenced tree species inventories distributed across LTSA. We used a priori vegetation classifications and cluster analyses of floristic composition to assign sites to biomes. We mapped these biomes geographically and assessed climatic overlaps amongst them. We implemented classification tree approaches to quantify how well climatic and edaphic data can assign inventories to biomes. Results Our analyses distinguish savanna and seasonally dry tropical forest (SDTF) as distinct biomes, with the Chaco woodlands potentially representing a third dry biome in LTSA. Amongst the wet forests, we find that the Amazon and Atlantic Forests might represent different biomes, because they are distinct in both climate and species composition. Our results show substantial environmental overlap amongst biomes, with error rates for classifying sites into biomes of 19–21 and 16–18% using only climatic data and with the inclusion of edaphic data, respectively. Main conclusions Tree species composition can be used to determine biome identity at continental scales. We find high biome heterogeneity at small spatial scales, probably attributable to variation in edaphic conditions and disturbance history. This points to the challenges of using climatic and/or interpolation‐based edaphic data or coarse‐resolution, remotely sensed imagery to map tropical biomes. From this perspective, we suggest that using floristic information in biome delimitation will allow for greater synergy between conservation efforts centred on species diversity and management efforts centred on ecosystem function.

Biomes as evolutionary arenas: Convergence and conservatism in the trans‐continental succulent biome

“…Climatically, the distribution of grid cells containing at least two genera of stem succulents closely matches the proposed climate of the succulent biome (Dexter et al, 2018; Oliveira‐Filho et al, 2013; Schrire et al, 2005; Silva de Miranda et al, 2018; Figure 2). Ninety percent of cells containing stem succulents receive less than 1,300 mm annual precipitation, close to the 1,200 mm upper limit for succulent biome in eastern South America proposed by Oliveira‐Filho et al (2013) (Figure 2d).…”

“…Another discrepancy between our stem succulent model and traditional SDTF maps is the Chaco. The Chaco has characteristics of SDTFs (seasonally dry, fire‐free, grass‐poor), is clearly not a savanna, as indicated in the latest global map of grassy biomes (Lehmann et al, 2019), appears to comprise a mosaic of elements from several biomes (Segovia et al, 2019), and has been considered a distinct biome based on differences in soils, occurrence of frost, and floristic composition (DRYFLOR, 2017; Pennington et al, 2000; Silva de Miranda et al, 2018). The affinities of the Chaco remain debatable (Kuemmerle et al, 2017; Segovia et al, 2019).…”

Freezing and water availability structure the evolutionary diversity of trees across the Americas

“…Vegetation formations were taken from the NeoTropTree dataset, which categorises formations first based on physiognomy (savanna vs. forest) and then segregates the forests based on phenology. Following (35) and (54), we consider deciduous tropical forests to represent the tropical dry forest biome, while semideciduous forests are more related floristically to the tropical moist forest biome. Semideciduous forests share many tree species with evergreen forests and relatively few with more fully deciduous forests (35,54).…”

“…Following (35) and (54), we consider deciduous tropical forests to represent the tropical dry forest biome, while semideciduous forests are more related floristically to the tropical moist forest biome. Semideciduous forests share many tree species with evergreen forests and relatively few with more fully deciduous forests (35,54). We further divided the savannas based on geography, as our analyses showed evident differences in group affiliation between savannas in the Cerrado Domain of Brazil versus those further north (i.e.…”

Global Succulent Biome phylogenetic conservatism across the pantropical Caesalpinia Group (Leguminosae)

“…(). This biome encompasses a range of seasonally dry tropical vegetation, from medium stature closed‐canopy deciduous forests – exemplified by Neotropical seasonally dry tropical forests (SDTFs) (Pennington et al ., , , ; Särkinen et al ., ; DRYFLOR, ; Dexter et al ., ; Silva de Miranda et al ., ) – to lower stature open thorn and cactus scrub and thicket vegetation, together grouped as seasonally dry tropical forest and woodland (SDTFW rather than SDTF) (de Queiroz et al ., ). As defined by Schrire et al .…”