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The Amazon forest is far from uniform, containing different forest types and even savannas, but quantitative analyses of this variation are lacking. Here, we applied ordination analyses to test the floristic differentiation among Amazonian vegetation types using data for virtually all known tree species occurring in the Amazon (8224), distributed across 1584 sites. We also performed multiple regressions to assess the role of climate and substrate in shaping continental‐scale patterns of community composition across Amazonia. We find that the traditional classification of Amazonian vegetation types is consistent with quantitative patterns of tree species composition. High elevation and the extremes of substrate‐related factors underpin the floristic segregation of environmentally “marginal” vegetation types and terra firme forests with climatic factors being relatively unimportant. These patterns hold at continental scales, with sites of similar vegetation types showing higher similarity between them regardless of geographic distance, which contrasts with the idea of large‐scale variation among geographic regions (e.g., between the Guiana Shield and southwestern Amazon) representing the dominant floristic pattern in the Amazon. In contrast to other tropical biomes in South America, including the Mata Atlântica (second largest rain forest biome in the neotropics), the main floristic units in the Amazon are not geographically separated, but are edaphically driven and spatially interdigitated across Amazonia. Two thirds of terra firme tree species are restricted to this vegetation type, while among marginal vegetation types, only white‐sand forests (campinaranas) have a substantial proportion of restricted species, with other vegetation types sharing large numbers of species.
Biotropica. 2021;00:1–11.
Received: 21 August 2020 
Revised: 30 December 2020 
Accepted: 30 December 2020
DOI: 10.1111/btp.12932
On the floristic identity of Amazonian vegetation types
Ary T. Oliveira- Filho1| Kyle G. Dexter2,3 | R. Toby Pennington3,4 |
Marcelo F. Simon5| Marcelo L. Bueno6| Danilo M. Neves1
© 2021 The Association for Tropical Biology and Conservation
1Institute of Biological Sciences, Federal
University of Minas Gerais, Belo
Horizonte, Brazil
2School of GeoSciences, University of
Edinburgh, Edinburgh, UK
3Department of Tropical Diversity, Royal
Botanic Garden Edinburgh, Edinburgh, UK
4Department of Geography, College
of Life and Environmental Sciences,
University of Exeter, Exeter, UK
5EMBRAPA Recursos Genéticos e
Biotecnologia, Brasília, Brazil
6Unidade Universitária de Mundo Novo,
Universidade E stad ual de Mato Grosso d o
Sul, Mundo Novo, Brazil
Danilo M. Neves, Institute of Biological
Sciences, Federal University of Minas
Gerais, Belo Horizonte 31270– 090, Brazil.
Funding information
Conselho Nacional de Desenvolvimento
Científico e Tecnológico— CNPq/Brazil
to A.T.O.- F. (301644/88- 8); Instituto
Serrapilheira/Brazil to D.M.N. (Serra-
1912- 32082); US National Science
Foundation to D.M.N. (DEB- 1556651);
Coordenação de Aperfeiçoamento de
Pessoal de Nível Superior— CAPES/PrInt/
Brazil to D.M.N. (88887.474387/2020-
00); UK National Environmental Research
Council to R.T.P., K.G.D., D.M.N. (NE/
I028122/1); UK Leverhulme Trust
International Academic Fellowship to
Associate Editor: Ferry Slik
Handling Editor: Rakan Zawahi
The Amazon forest is far from uniform, containing different forest types and even
savannas, but quantitative analyses of this variation are lacking. Here, we applied
ordination analyses to test the floristic differentiation among Amazonian vegetation
types using data for virtually all known tree species occurring in the Amazon (8224),
distributed across 1584 sites. We also performed multiple regressions to assess the
role of climate and substrate in shaping continental- scale patterns of community com-
position across Amazonia. We find that the traditional classification of Amazonian
vegetation types is consistent with quantitative patterns of tree species composition.
High elevation and the extremes of substrate- related factors underpin the floristic
segregation of environmentally “marginal” vegetation types and terra firme forests
with climatic factors being relatively unimportant. These patterns hold at continental
scales, with sites of similar vegetation types showing higher similarity between them
regardless of geographic distance, which contrasts with the idea of large- scale vari-
ation among geographic regions (e.g., between the Guiana Shield and southwestern
Amazon) representing the dominant floristic pattern in the Amazon. In contrast to
other tropical biomes in South America, including the Mata Atlântica (second largest
rain fore st biome in the neotropics), the main floristic unit s in the Amazon are not ge o-
graphically separated, but are edaphically driven and spatially interdigitated across
Amazonia. Two thirds of terra firme tree species are restricted to this vegetation type,
while among marginal vegetation types, only white- sand forests (campinaranas) have
a substantial proportion of restricted species, with other vegetation types sharing
large numbers of species.
community composition, edaphic conditions, environmental gradients, environmentally
marginal habitats, ordination analysis, terra firme forests, tree species, white- sand forest
The Amazon forest, which spreads across the lowlands of the
Amazon, Orinoco and other northern drainages of South America, is
the world's largest continuous expanse of tropical rain forest, with an
ever- inc reasing numb er of desc ribe d pla nt sp ecie s (Ca rdos o et al., 2017;
ter Steege et al., 2016). Since the first scientific exploration of the 18th
and 19th centuries, it has been clear that the region is far from a con-
tinuous and undifferentiated rain forest, as there are striking contrasts
among forest physiognomies and even patches of savanna vegetation.
Two main dichotomies in vegetation types have long been est ab-
lished, both using divisions based upon which environments are in-
terpreted to be more marginal (Salovaara et al., 2005). One contrasts
upland, terra firme forests growing on flood- free interfluves (literally
solid or firm ground; tierra firme in Spanish) with those growing on
the seasonally inundated floodplains along wide and slow flowing,
larger rivers (Luize et al., 2018). The other dichotomy contrasts both
terra firme and flooded forests with forest occurring on pockets of
highly leached deposits of podzolized hypo- dystrophic white- sand
(Adeney et al., 2016). But while the environmental differences be-
tween terra firme, flooded, and white- sand forests are somewhat
striking, the lines between these forests and the other vegetation
types in the Amazon are not always sharp, contributing to some no-
menclatural confusion (Phillips et al., 2003).
There are several additional prominent vegetation types in the
Amazon, growing on and around rock outcrops and coastal sands. In
both edaphic situations, the vegetation shows a wide array of phys-
iognomic expressions, including forests, dwarf- forests, scrublands,
and bushlands, often mixed in mosaics. Rock outcrops are particu-
larly evident across the chain of sandstone highlands of the Guiana
Shield (often referred to as tepuis; Berry & Riina, 2005; Huber, 1997),
and on the top of the numerous inselbergs of both the Brazilian and
Guiana Shields (Gröger, 2000; Raghoenandan, 2000). Coastal veg-
etation mosaics include extensive tracts of mangrove forests that
run almost uninterrupted from the Brazilian island of São Luís to
the Orinoco Delta in Venezuela and may penetrate inland as far as
40 km where they gradually blend with flooded forests (González,
2011; Nascimento et al., 2013). Away from the mangroves, pockets
of stabilized coastal sands bear a mosaic of vegetation types usually
referred to as restingas and matas de ma in Brazil (Silva et al., 2010).
Although virtually all the environmentally marginal vegetation
types can include open physiognomies that may resemble savan-
nas, the Amazon is also home to savannas sensu stricto, that is, those
associated with the existence of a dry season lasting for at least
3 months, and a flammable grass ground layer that may trigger fire
outbreaks (Huber, 1997). Most of these savannas experience some
form of waterlogging during the rainy season (Pennington et al.,
2006; Sarmiento, 1984).
From previous studies, we know that tree species distribution
patterns do match some of these pre- defined vegetation types at
local and regional scales (10– 100,000 km2; e.g., Draper et al., 2018;
Draper et al., 2019; Duivenvoorden, 1995; Guitet et al., 2015;
Higgins et al., 2011; Pitman et al., 2008; Scudeller, 2018; Stropp
et al. , 2011; ter St eege et al., 2000) but, so far, this has not bee n scru-
tinized for the Amazon region as a whole and all its main vegetation
types. A common conclusion stemming from the few Amazon- wide
floristic studies is that distinct vegetation types in one region tend
to resemble one another more closely than they do the same vege-
tation types in other regions (Silva- Souza & Souza, 2020; ter Steege
et al., 2006; Terborgh & Andresen, 1998). Such conclusions have led
to a view of floristic regionalization that has neglected the differ-
ent vegetation types of Amazonia. For example, there is a consistent
west to east gradient in tree community composition, congruent
with an Amazon- wide variation in soil fertility and drought (soils in
the eastern Amazon are poorer and climate is drier; ter Steege et al.,
2006). These continental- scale analyses have either been conducted
at coarser taxonomic scales— at the family (Terborgh & Andresen,
1998) and genus- level (ter Steege et al., 2006)— or have lumped taxa
from distinct vegetation types into large geographic “grid cells” (e.g.,
4° × 6° in ter Steege et al., 2006; up to 20 km distance in Silva- Souza
& Souza, 2020). Here, we bring together the most comprehensive,
species- level dataset to date on the composition of tree communi-
ties across the entire Amazon basin, where individual communities
have been assigned a priori to one of the predominant vegetation
types in the Amazon.
Our objectives are threefold. Firstly, we test the floristic dif-
ferentiation of nine vegetation types, following the classification
system proposed by Oliveira- Filho (2015). We predict that by using
comprehensive, species- level tree community surveys, most (if
not all) vegetation types will show an Amazon- wide compositional
Secondly, we test whether variation in edaphic and climatic con-
ditions controls the floristic differentiation between terra firme for-
est and other vegetation types, with marginal vegetation types being
placed in environments sometimes interpreted to be more stressful
(Salovaara et al., 2005). We predict that the floristic segregation of
lowland vegetation t ypes is primarily associated with edaphic fac-
tors (e.g., rockiness, sandiness, salinity, soil waterlogging), with cli-
mate being only important in segregating highland vegetation types
(e.g., montane forest, tepuis) from all others.
Finally, to give context to our results and to explore the floris-
tic distinctiveness of vegetation types, we also examine patterns of
species shared among these vegetation types and the propor tion of
species restricted to individual vegetation types.
2.1  |  Study area
The Amazon forest, as circumscribed here (see outline in Figure 1),
includes most of the Amazon and Orinoco river basins (excluding
the Andean headwaters of some rivers and the mid- Orinoco Llanos),
and the North Atlantic coastal river basins between the states of
Delta Amacuro, in Venezuela, and Maranhão, in Brazil. With regards
to elevation, a maximum altitude of 1100 m was established on the
Andean flanks to exclude the complex and extensive vegetation and
environment gradients associated with the massive mountain chain.
No altitudinal limit was established, however, for the highlands of the
Guiana Shield, which are entirely embedded in the Amazon Province.
This is a controversial issue in the sense that some authors consider
the Guiana Highlands as a separate biogeographic province (e.g.,
Cabrera & Willink, 1980; Cardoso et al., 2017), supported by the high
number of endemic species, many of which are restricted to particu-
lar tepuis or highlands (Berry & Riina, 2005). We based our decision
on the following facts: (a) unlike the Andes, which make up a natural
limit, the Guiana Highlands are encircled and pervaded by Amazonian
lowlands; (b) the highest altitudes reached by the Guiana Highlands
(25003000 m) are modest compared to those of the Andes; and (c)
tepuis and highlands also share a considerable number of species with
lowland Amazonian vegetation types (Steyermark et al., 1995– 2005).
2.2  |  Nomenclature
The white- sand vegetation complex is particularly thorny when it
comes to nomenclature. The main reason for this is the remarkable
variation in physiognomy, which ranges from grass/shrublands to for-
ests with slender- trunked trees and more open canopies compared
to those of adjacent terra firme forests growing on more clayey soils
(Adeney et al., 2016). Throughout the Amazon, various local terms
are also used to designate both the whole white- sand complex and
its physiognomic expressions, for example, bana, caatinga amazônica,
campina, campinarana, varillal, and chamizal (Demarchi et al., 2018;
Fine et al., 2010; García- Villacorta et al., 2016; Stropp et al., 2011).
Following Daly et al. (2016), we here adopt campinarana, because
of its official use in Brazil (IBGE, 2012) and because it embraces the
whole array of physiognomies growing on podzolized sands liable
to ground water saturation, but conveniently excludes white- sand
floodplain forests, which we distinguish in this paper.
Nomenclature for vegetation occurring on seasonal floodplains is
less complex. We use the prevailing nomenclature for two main sea-
sonally flooded vegetation types in the Amazon, distinguishing igapó
and várzea fo rests, de pen ding on th e ty pes of ri vers al o ng whi c h they
occur (see Junk et al., 2011; Kubitzki, 1987; Prance, 1979). Vár zea
forests are found along rivers carrying copious quantities of sedi-
ments (and nutrients), mostly brought from the Andes, with variation
in the amount of clay resulting in waters that are many shades of
brown. Confusingly, these rivers are often called white- water rivers
(ríos de agua blanca, rios de água branca). In contrast, igapó forests
are found along rivers with small amounts of suspended mineral
particles, which are called black or clear- water rivers (ríos de agua
negra o clara, rios de água negra ou clara). These rivers drain basins
where white sands or other highly leached soils prevail (e.g., flowing
from the Brazilian and Guiana Shields) and can carry vast loads of
humic acid colloids resulting from the arrested litter decay in these
hypo- dystrophic soils. A similar process takes place in black- water
oxbow lakes severed from white- water rivers as well as in narrower
upstream floodplains throughout the basin. The dichotomy of várzea
and igapó falls short when it comes to rivers with “mixed” waters,
and rivers with temporal and spatial variations in suspended par ti-
cles, of which the Casiquiare Channel in Venezuela is an example. In
both igapós and várzeas, vegetation structure varies from tall forests
to floodplains with more open formations, depending on local flood-
ing dynamics and related processes of either erosion or sedimenta-
tion (Kalliola et al., 1992; Luize et al., 2018; Salo et al., 1986; Worbes
et al., 1992). The timing and duration of flooding in these forests
can be variable, from once every few decades in rivers close to the
Andes (e.g., on the Manu River in Peru, pers. comm. John Terborgh)
to multiple months annually for the iconic várzeas and igapós along
major rivers such as the Amazon and the Rio Negro.
2.3  |  Dataset
We extracted the dataset from the NeoTropTree (NTT) database
(http://www.neotr, which consists of tree species
checklists compiled for geo- referenced sites, from southern Florida
FIGURE 1 Distribution of the 1584
Amazonian sites used in the analyses
with their a priori classification into nine
vegetation types. Blue and white contours
illustrate major rivers and national
borders, respectively. Our delimitation of
the Amazon is outlined in a darker, gray-
green color
(U.S.A.) and Mexico to Patagonia in Argentina and Chile. Trees here
are defined as freely standing woody plants >3 m in height, including
tree ferns. NTT currently holds 7485 sites/checklists, 20,562 tree
species, and 1,206,314 occurrence records. A site/checklist in NTT
is defined by a single vegetation type, following the classification
system proposed by Oliveira- Filho (2015), contained in a circular
area with a 10 km diameter. Where two or more vegetation types
co- occur in the area, there can be multiple geographically overlap-
ping sites in the NTT database.
The data were originally compiled from an extensive survey
of published and unpublished (e.g., PhD theses) literature, partic-
ularly those on tree community sur veys and floristic inventories.
Additional occurrence records obtained from both major herbaria
and taxonomic monographs have been added to the checklists when
they were collected within the 10- km diameter of the original NTT
site, and within the same vegetation type. NTT does not include
sites with an indication of high anthropogenic disturbance nor those
with low species richness, because this is of te n du e to low sampling/
collecting efforts, which results in poor descriptive power. Thus,
secondary forests, which might be considered a distinct vegetation
type, are not included in our study. Lowest species richness in the
Amazon dataset ranged from 20 species in savanna s.s. and campina-
rana to 100 in terra firme forest, while plot size (in tree community
surveys derived from plot data) ranged from 1 to 5 ha.
All species and their occurrence records were checked for taxo-
nomic circumscriptions and geographical distributions as accepted
by the teams of specialists responsible for the online projects Flora
do Brasil, Catalogue of the Vascular Plants of Ecuador, Peru Checklist,
Bolivia Catalogue (available at http://flora dobra, http://
www.tropi ct/CE/, http://www.tropi ct/
PEC, and http://www.tropi ct/BC/, respectively) and
published floras (Bernal et al., 2016; Boggan et al., 1997; Cardoso
et al., 2017; Steyermark et al., 1995– 2005). We eventually eliminated
records for 111 species due to synonymy (59), invalid or dubious
name s (7), in correc t growth hab it (15), and incorr ect dist ribution (30).
The final dataset contained presence/absence data for 8224 tree
species across 1584 sites, with a total of 364,965 presences. Sites
derived exclusively from herbarium data represented 41% of the full
matrix (654 sites). The dataset also included 24 environmental vari-
ables (30 arc- sec resolution) for all its sites, derived from multiple
sources. Procedures and protocols concerning variables’ sources and
extraction are thoroughly detailed at http://www.neotr
We adopted the vegetation descriptors provided by NTT and
based on Oliveira- Filho (2015) to classify the sites into nine vege-
tation types: 776 terra firme forests, 171 campinaranas, 291 várzeas,
176 igapós, 55 rock outcrops, 36 tepuis, 29 coastal mosaics, 28 sa-
vannas sensu stricto (hereafter savanna s.s.), and 22 montane forests
(Figure 1; Table S1). All sites classified as tepuis and montane for-
ests occur above 1100 m of altitude (see Study Area), with tepuis
differing from montane forests in their rocky soils and dwarfish
physiognomy. The map in Figure 1 was designed using the packages
maptools (Bivand & Lewin- Koh, 2017) and raster (Hijmans, 2016) in
R Statistical Environment (R Core Team, 2018).
The NTT database also includes environmental variables for all
its sites, derived from multiple sources (at a 30 arc- second resolu-
tion). Altitude at the NTT site center was used as an integrative en-
vironmental variable. Variables representing average climate (mean
annual precipitation and temperature) as well as climate extremes
(e.g., precipitation in driest month) and seasonality (e.g., precipi-
tation seasonality) were obtained from WorldClim 1.4 data layers
(Hijmans et al., 2005). Frost frequency (days) and cloud interception
(mm) were obtained from interpolating known values as response
variables (data obtained from 135 and 57 Brazilian Meteorological
Stations measuring frost frequency and cloud interception, respec-
tively) with elevation, latitude, and the WorldClim layers as pre-
dicting variables. Soil coarseness (% sand) and soil fertility (% base
saturation) and surface rockiness (% exposed rock) were obtained
from the Harmonized World Soil Database v1.2 (available at http:// - porta l/soil- surve y/soil- maps- and- datab ases/
harmo nized - world - soil- datab ase- v12/en/) and ranked afterward by
mid- class percentage. The use of classes was adopted because high
local soil heterogeneity can make raw figures unrepresentative. Soil
Water Storage capacity (%) was obtained from the International Soil
Moisture Network (available at u/).
2.4  |  Analyses of community composition
We fir st explored the patterns of floristic differentiation among pre-
viously defined vegetation types by performing non- metric multidi-
mensional scaling (NMDS; McCune & Grace, 2002), and tested its
overall significance by applying an analysis of similarities (ANOSIM;
Clarke, 1993). Beforehand, we excluded 832 singletons (species
found at a single site), as they commonly increase the noise in ordi-
nation analyses without contributing information (Lepš & Šmilauer,
2003), and then computed pairwise compositional distances be-
tween all sites using Simpson distance as the dissimilarity metric
(Simpson, 1960), which describes community turnover without the
influence of richness gradients (Baselga, 2010).
We used the vegetation types confirmed in the ordination anal-
ysis to produce sets of diagnostic species based on their coef ficient
of fidelity (phi; Tichý & Chytr ý, 2006). An advantage of this coeffi-
cient is that they can take negative values, which expresses the fact
that a species tends to “avoid” a particular habitat and its environ-
mental conditions (De Cáceres & Legendre, 2009; De Cáceres et al.,
2008). In this study, diagnostic species represent those statistically
associated with one or more vegetation types so that their presence
in species lists may be a strong indicator of the veget ation types
themselves. Significance of phi was obtained via Monte Carlo per-
mutations (999). Species’ phi for each vegetation type are provided
as Supplementary Information (see Table S2).
We then used the major axes of compositional variation sum-
marized by the ordination analysis to test whether the obser ved
patterns of floristic differentiation in the Amazon are underpinned
by extreme environmental conditions segregating terra firme forests
from environmentally marginal vegetation types. First, we selected
a subset of significant environmental variables for each of the major
NMDS axes through an AIC- based forward selection method for
generalized linear models and then performed an additional and
progressive elimination of collinear variables based on their vari-
ance inflation factor (VIF), informed by their ecological relevance,
until maintaining only those with VIF < 4 (Quinn & Keough, 2002).
We tested the significance of the selected environmental variables
by applying ANOVA permutation tests (999 permutations). We ex-
plored the result s visually by fitting the values of the most important
environmental variables in ordination space (NMDS). The variable
selection, VIF, NMDS and phi analyses were conducted using the
vegan (Oksanen et al., 2016), recluster (Dapporto et al., 2015), usdm
(Naimi et al., 2014) and indicspecies (De Cáceres & Legendre, 2009)
packages in R Statistical Environment (2018).
Finally, we used a chord diagram to assess the patterns of com-
positional overlap among Amazonian vegetation types. The chord
diagr am was designed using the D3 Java Environment (Bostock et al.,
2011; custom codes available at
The distribution of the sites in ordination space yielded by NMDS
(K = 2; stress = 0.17; Figure 2) largely segregated the previously de-
fined Amazonian vegetation types (ANOSIM R = 0.85; p = 0.001). We
found a negligible decrease in stress values by adding a third NMDS
axis, and a high correlation between the distances summarized by
the first two axes and the full distance matrix (Pearson's r = 0.83).
Thus, we focused subsequent analyses on the two- dimensional ordi-
nation space, and the results are detailed below.
Axis 1 places both terra firme forests and campinaranas at inter-
mediate scores and is congruent with two gradient s: the first toward
seasonally flooded forests (várzeas and igapós), placed at one ex-
treme, and the second toward montane forests and open formations
(coastal mosaic, rock outcrops, savanna s.s., and tepuis), at the other
extreme. Axis 2 segregated várzeas, tepuis, terra firme, and montane
forests at one extreme, and igapós, campinaranas, and the remaining
open formations at the other. It is worth noting that campinaranas
seem to be closer to savannas s.s. than to terra firme forests along
this axis. In addition, the differentiation between terra firme forest,
savanna s.s., and the coastal mosaic is more nuanced and suggests
a forest- to- savanna gradient. These patterns are robust to exclud-
ing sites (checklists) compiled exclusively from herbarium data (654
sites; Figure S1).
The furthest extremes of substrate- related variables lead to
distinct, environmentally marginal vegetation types (Figure 2). The
selected environmental predictors account for 72% and 62% of the
variation in community composition summarized by the first two
NMDS axes, respectively (Table 1). An increase in sandiness was
congruent with the floristic differentiation of campinaranas from all
other vegetation types, while an increase in soil water storage ca-
pacity (a proxy of seasonal soil waterlogging) was associated with
the floristic dif ferentiation between seasonally flooded forests
(várzeas and igapós) and all other vegetation types. The somewhat
nuanced differentiation between the two seasonally flooded vege-
tation t ypes is congruent with decreasing soil fertility from várzeas
to igapós. Precipitation seasonality was associated with the floris-
tic differentiation of coast al mosaics and savanna s.s. from all other
vegetation types, with the segregation between these two being as-
sociated with higher soil sandiness in coastal mosaics. High sur face
rockiness (a proxy of soil water deficit) was congruent with the flo-
ristic segregation of forests associated with tepuis and rock outcrops
from all other vegetation types. Altitudinal gradients in cloud inter-
ception and mean annual temperature drive the floristic differenti-
ation between highland vegetation types, namely montane forests
and tepuis, and all other vegetation types. Te pui s are associated with
higher cloud interception, thus reflecting lower water deficit when
compared to rock outcrops. Finally, both tepuis and montane forests
are found under lower mean annual temperature, with intermediate
conditions of cloud interception segregating mont ane forests from
tepuis (high cloud interception) and lowland terra firme forests (low
cloud interception).
There are a considerable number of species restricted to terra
firme forests in our dataset (4424 species), which far surpasses the
number of species terra firme shares with other vegetation types
(2032 species; Figure 3). There is also a high proportion of species
in campinaranas that are res tricted to that vegetation type (42%). In
contrast, the other seven vegetation types have a low proportion
of species restricted to them, ranging from 6% in coastal mosa-
ics and savanna s.s. to 25% in tepuis. Species shared between terra
FIGURE 2 Ordination of 1584 tree communities in the Amazon
inferred from non- metric multidimensional scaling of their species
composition. Colors indicate the a priori classification into nine
main vegetation types, and darker shades in each color indicate
overlapping circles (i.e., two or more sites show high similarity
in species composition). PrecSeas = precipitation seasonality;
CloudItcp = cloud interception; SoilFert = soil fertility; SWS = soil
water storage capacity; TempAnn = mean annual temperature
firme forest (the largest species pool) and other marginal vegeta-
tion types are high. Among marginal vegetation types, the number
of species shared ranges from 18, between igapó and tepui, to 655
shared between igapó and rzeas (Figure 3). These results indi-
cate that, apart from terra firme forests, most of the tree flora of
Amazonian vegetation types are shared among t wo or more vege-
tation types, with their community compositions, which are distinct
(Figure 2), representing unique combinations of the Amazonian
species pool.
4.1  |  Continental- scale patterns
The composition of the tree flora across the Amazon region shows
variation congruent with traditional vegetation classifications. The
most species rich and geographically widespread vegetation type
is terra firme forest, while marginal vegetation types, such as campi-
narana, savanna s.s., igapó or várzea, diverge in species composition
along distinct environmental gradients. These marginal vegetation
types house many t ree species not found in terra firme fores t, yet large
numbers of them are shared among the dif ferent marginal vegetation
types themselves, for example between savanna s.s. and campinarana.
The marginal vegetation types are placed at extreme values of
the significant environmental gradients, potentially indicating eco-
physiological stress, and our results highlighted that substrate, not
climate, is the most important environmental driver controlling the
major axes of composition in Amazonian tree communities. Different
from other forest biomes in South America, where variation in
temperature and water availability are clearly the most important
factors controlling continental- scale patterns of tree community
composition (e.g., in seasonally dry tropical forests (Neves et al.,
2015), or in the Mata Atlântica (Neves et al., 2017)), climatic condi-
tions are relatively unimportant in Amazonia (but see discussion for
montane forests and tepuis).
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 con-
ditions (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 con-
sidering 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
Cloud interception 0.2 24 <0.0001 0.059 <0.0001 2.398
Mean annual temperature 0.228 <0.0001 0.225 <0.0001 2.812
Precipitation seasonality 0.041 <0.0001 1.046
Sandiness 0.051 <0.0001 0.294 <0.0001 1.990
Soil fertility 0.207 <0.0001 2.087
Soil water storage capacity 0.656 <0.0001 0.013 <0.0001 3.095
Surface rockiness 0.327 <0.0001 0.019 <0.0001 2.534
All variables 0.723 <0.0001 0.623 <0.0001
Note: Values under NMDS1 and NMDS2 represent the coefficients of determination (adjusted R2,
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. VIF = variation inflation factor, as a measure of collinearity between all
variables in the analyses (variables were progressively eliminated until VIF < 4).
TAB LE 1  Significant climatic and
edaphic predictors of large- scale gradients
of tree community composition in the
FIGURE 3 Overlap in tree species composition among
Amazonian vegetation types. Values in white express the number
of species that are shared among vegetation types or restricted
to a given vegetation type, respectively (the sum of these values
represent the total species richness in that vegetation type). Chord
width is proportional to the number of shared species
the compositional identit y of the dominant vegetation type in the
grid cell, and if there are geographic gradients in the prevalence
of vegetation types, the geographic grid cell approach may lead to
geographically driven results, which mask vegetation heterogeneity
within grid cells. Our approach ensured that every sample unit (i.e.,
site or community) represents only a single vegetation type, which
is likely why we find a clearer signal for vegetation type than for
geography in our results. That these vegetation types are floristi-
cally coherent across the Amazon basin also suggests that dispersal
among areas of the same vegetation type is not particularly limited
by geographic distance, in agreement with a recent study of several
Amazonian tree genera (Dexter et al., 2017).
Below we delve into the main floristic patterns observed in our
results to discuss the compositional identity and environmental dis-
tinctiveness of Amazonian vegetation types. Because the dataset
used in this study does not include sites with a high indication of
anthropogenic disturbance, we stress that analyses including com-
munity inventories (e.g., floristic checklists, plot data) from recently
degraded areas, such as early- stage secondary forests, may reveal
additional vegetation types.
4.2  |  Forest types
Flooded forests share a similar environmental condition driving
their compositional distinction from terra firme forests: seasonal
flooding, potentially combined with soil waterlogging during the
low water season. This, however, does not lead to homogeneous
stands of flooded forests throughout the Amazon, and one of their
main variations was captured here as follows: the floristic, edaphic
and distributional differentiation of igapós and várzeas. rzea
forests are more evenly distributed across major river basins in
Amazonia, while most igapó forests are concentrated in the Rio
Negro and upper Orinoco River Basins where the substrate is of
highly leached and impoverished white sands. Nonetheless, igapó
forests are also found in other Amazonian regions under similar
edaphic conditions (Montero et al., 2014; Wittman et al., 2010). In
addition, both types of flooded forests have species restricted to
them in our dataset (160 species restricted to várzeas and 168 to
igapós), though the largest proportion of their species composition
is either shared bet ween them or with terra firme forests (Figure 3;
Scudeller, 2018).
The tree flora of montane forests in Amazonia is compositionally
coherent with the main floristic patterns described for Neotropical
montane flora in general, such as the presence of some genera that
are rare to absent in the lowland flora, including Bonnetia, Brunellia,
Drimys, Hedyosmum, Ilex, Laplacea, Meriania, Podocarpus, Symplocos
and Weinmannia (Webster, 1995). The overall lack of these taxa in
lowland Amazonia is likely driven by temperature, an important
environmental factor driving floristic differentiation between mon-
tane and terra firme forests in our dataset. Nonetheless, variation
in temperature across the range and location of elevations sampled
in our study is not large, thus explaining the high proportion of tree
species shared between montane forests and other Amazonian hab-
itats (88%), and supporting the claim that these forests should be
treated as Amazonian (contrasting with views in Cabrera & Willink,
1980; Cardoso et al., 2017). Igapó forests, for instance, share a lower
proportion of tree species with other Amazonian habitats (82%),
yet igapós are consistently treated as Amazonian (Wittmann et al.,
2010). The fact is that many lowland terra firme species do extend
their distribution toward high altitudes (1100– 3000 m), such as
Annona symphyocarpa, Coussapoa crassivenosa, Cyathea bipinnati-
fida, Cyathea macrosora, Elaeoluma nuda, Hieronyma oblonga, Miconia
dodecandra, Miconia pseudocapsularis, Miconia punctata, Mollinedia
ovata, Nectandra reticulata and Quiina cruegeriana; to cite a few di-
agnostic species of both mont ane and terra firme forests (Table S2).
The scarcity of mineral nutrients in white- sand environments is
probably the leading environmental distinction of campinaranas, and
plant species there are known to have acquired morphological, phys-
iological and mutualistic traits to maximize both nutrient capture
and retention (Adeney et al., 2016). This specialized flora explains
much of the differentiation of campinaranas from other vegetation
types, which is evident in the high proportion of restricted species
(42%; Figure 3). This is almost twice the proportion of endemics in
western Amazonian campinaranas found by Garcia- Villacorta et al.
(2016; 23%), but this is probably explained by the fact that those
authors worked with the whole spectrum of growth habits, and not
only trees, considered all available herbarium voucher data (not just
those collected near NTT sites as done here) and concentrated their
efforts only in western Amazonia.
4.3  |  Open formations
Th e coa stal sand dep osi ts along th e Atl ant ic sho res, co vered by a mo -
saic of mangroves and sandy beaches, represent another Amazonian
vegetation type associated with white- sand substrates. However,
soils in these coast al mosaics are more fertile than in campinaranas,
and they are mostly found in the eastern Amazon, where precipita-
tion seasonality is relatively more pronounced. Nonetheless, these
white- sand, seasonally dry coastal environments are not too exten-
sive (Cremers & Hoff, 2003; González, 2011; Silva et al., 2010), nor do
they seem to be restrictive floristically, as 94% of species in coastal
mosaics are also found in other vegetation types. Accordingly, they
have one of the lowest proportions of restricted tree species in
Amazonian habitats— only 15 tree species are restricted to coastal
sand de pos its in this anal ysis, nine of which are typic al of mangroves .
Water deficit intervals, mediated by climate, substrate or both,
drive tree community differentiation in two other environments:
savannas s.s. and rock outcrops. Most savannas s.s. are found where
the dr y season is longest in the Amazon, and where fire outbreaks
may occur in the dry season. Interestingly, many of these savannas
are hyper- seasonal (sensu Sarmiento, 1983), in that they also face
some form of water excess in the rainy season, mostly due to soil
waterlogging either caused by poor drainage or floods, as in the
Bolivian Llanos de Moxos and in the Brazilian estuarine island of
Marajó. Nevertheless, there are also non- hyper- seasonal savannas,
particularly on hills with shallow soils in the Brazilian state of Pará,
where the flora shares a great number of species with that of the
Cerrado savannas in Central Brazil (Devecchi et al., 2020). In fact,
the tree flora of most Amazonian savannas does show some floristic
affinity with the savannas of either the Brazilian Cerrados or the
Venezuelan Llanos (Buzatti et al., 2018; Ratter et al., 2006; see also
Devecchi et al. 2020 for comparisons between all plant life- forms).
Rock outcrops are another common feature in the Amazon
that may experience local water shortage, even in ever- wet areas,
because rainwater is promptly drained from the substrate. Rock
outcrops are particularly common across inselbergs on both
the Guiana and Brazilian Crystalline Shields, where they host
tree species not found elsewhere in the Amazon (Gröger, 2000;
Raghoenandan, 2000). The xeric nature of rock outcrops is con-
firmed by the disjunct occurrences of a considerable number of
species that are also typic al of seasonally dr y deciduous forests
outside of the Amazon, such as Aspidosperma cuspa, Brasiliopuntia
brasiliensis, Bursera simaruba, Cereus hexagonus, Guapira cuspidata,
Senegalia riparia and Vachellia farnesiana. Apart from rock out-
crops, another substrate related to periods of water deficit in the
Amazon is the hardened surface of some mudflats, such as those
found on the Guyanese coastal plains and on the meanders of the
Lower Amazon and mid- Marañon rivers. This condition probably
explains the occurrence of a typical savanna vegetation and flora
in these regions, even under year- round wet climates.
The tepuis are formed of the steep slopes and plateaus of the
massive Paleozoic sandstones atop the Guiana Shield. Environmental
factors along altitudinal gradients are hardly ever easily summarized
by one varia ble and include fa ctors such as incre asing cloud intercep -
tion (an important factor in our models) and declining temperatures
toward higher altitudes. Additional sources of environmental het-
erogeneity include slope, aspect, and surface rockiness, and there
is usually a local combination of stressful factors at play. In general,
scrubs and savannas prevail on the shallow soils and bare rocks at
the summits of tepuis (Huber, 2005), where cloud interception is the
major source of water, and are replaced by montane forests in colder
environments with deeper soils.
It is important to bear in mind that, different from forest
types, the open formations in our analyses do not represent a
tree- dominated habitat. Therefore, our comparisons are based on
the few tree species that occur in these plant communities, while
he rbs , forbs an d shrub s are not in clu ded . If data for the who le pla nt
community were available, we would expect even higher dissim-
ilarities between these open habitats and other tree- dominated
habitats, with increased number of endemic species in the former.
Our findings show that the traditional classification of Amazonian
vegetation formations is consistent with quantitative patterns of
tree species distribution. We also demonstrate how the terra firme
forest is the core vegetation type from which the eight marginal
habitat s differentiate floristically in a manner consistent with more
extreme environmental conditions. These patterns, which have been
previously described at a regional scale, are documented here for
the first time across the entire Amazon Basin.
In addition, we show that a large proportion of tree species found
in the eight marginal vegetation types are shared among each other
and with terra firme fores ts. In fact, apar t from terra firme forests and
campinaranas, there is a small percentage of tree species restricted
to a single vegetation type in the Amazon. Nonetheless, if future
conservation strategies aim to protect the full set of tree species in
the Amazon, they must consider the identity and distribution of the
multiple vegetation types there, as well as their current status of
conservation. Many of the localities in our analyses may have been
impacted by the recent increase in deforestation and forest fires in
the Amazon, especially those found across the south and eastern
borders of the Brazilian Amazon— a region known as the “arc of de-
forestation” (Soares- Filho et al., 2006).
We are grateful to Hans ter Steege and an anonymous reviewer for
their constructive comments on the manuscript.
The authors declare no conflict of interest.
A.O.F compiled the database, conceived the idea, and designed the
manuscript. D.M.N. analyzed the data. A.O.F. and D.M.N. led the
writing with substantial input from R.T.P., K.G.D., and M.F.S. All au-
thors commented on the manuscript and approved the final version.
Presence/absence data for the 8224 tree species found across the
1584 Amazonian communities were extracted from the NeoTropTree
database (available at http://www.neotr
Bioclimatic variables and altitude were obtained from WorldClim 1.4
data layers (available at: Soil
variables were obtained from the Harmonized World Soil Database
v 1.2 (available at: - porta l/soil- surve y/soil-
maps- and- datab ases/harmo nized - world - soil- datab ase- v12/en/).
Soil Water Storage capacity was obtained from the International Soil
Moisture Network (available at
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How to cite this article: Oliveira- Filho AT, Dexter KG,
Pennington RT, Simon MF, Bueno ML, Neves DM. On the
floristic identity of Amazonian veget ation types. Biotropica.
... Geographic Distribution, Habitat, and Ecology-Aldina is confined to the Amazon basin, which covers a vast area of relatively poorly-botanized lowland tropical rainforest in Brazil (Hopkins 2007;Cardoso et al. 2017), a country recognized for its high floristic diversity and endemism (Forzza et al. 2012 Furthermore, other species of Aldina can be found in the black water floodplains (igap os), upland (terra-firme) (Fig. 3), and montane forests of the Amazonian tepuis along the Guiana Shield Region. Although at first sight the Amazon may look like an endless homogeneous type of vegetation, it harbors a mosaic of ecologically distinct vegetation physiognomies that are shaped by many variables such as altitude, river drainage, soil composition, and precipitation (Pires and Prance 1985;Oliveira-Filho et al. 2021). As shown for other Amazonian plant taxa (Fine et al. 2010;Draper et al. 2021;Fine and Baraloto 2016), the distribution of Aldina species seems to be constrained by their preferences for particular habitat types such berryi is one of the two species in the genus with glabrous ovary, occasionally with few hairs at its base. ...
... Such challenging environmental conditions, along with their island-like configuration, are often invoked to explain the lower species diversity of white-sand forests. Nevertheless, a high proportion of plant species (42%) are restricted to that vegetation type (Stropp et al. 2011;Fine and Baraloto 2016;Fine and Bruna 2016;Oliveira-Filho et al. 2021). Therefore, white-sand floras have a unique functional composition (Fortunel et al. 2014), suggesting important differences in ecosystem processes related to carbon and nutrient cycles. ...
... Amazonia spans more than 6 million square kilometers across eight South American countries and it is one of the most critical natural environments to sustain the biodiversity and regulate climate on a global scale (Davidson et al. 2012;Charity et al. 2016). In addition to its continental size, Amazonia holds remarkable environmental heterogeneity, having many vegetation types, from forested formations like 'Terra firme' (forests growing on the flood-free interfluves) and 'várzeas' (forests growing on the seasonally inundated floodplains, found along rivers carrying copious quantities of sediments and nutrients), to savannas sensu stricto (Oliveira-Filho et al. 2021). Such environmental heterogeneity affects the species diversity patterns in Amazonia, which has been divided into large geographic regions based on faunistic and floristic similarity since the nineteenth century (e.g., Wallace 1852). ...
... The state of Amapá has a territory of about 143 000 square kilometers (slightly larger than Greece) and harbors three biomes (Olson et al. 2001): Tropical Moist Broadleaf Forests; Tropical Grasslands, Savannas, and Shrublands (known as the Cerrado of Amapá); and Mangroves. The great majority of the state's territory (almost 82%) is composed of forested formations , which harbor a variety of vegetation types like Terra firme and várzeas forests, coastal vegetation mosaics, savannas, and even rock outcrops (Oliveira-Filho et al. 2021). Such habitat heterogeneity provides a high biodiversity to the state and, despite the fact that there are some punctual biologic inventories (e.g., Silva et al. 1997 [birds]; Cáceres & Aptroot 2016 [lichens]; Melo et al. 2016 [fishes]; Benício & Lima 2017 [anurans]), and also some DNA-based exploration of the diversity of the region (e.g., Vacher et al. 2020 [anurans]), studies compiling the knowledge about large taxonomic groups in Amapá are scarce. ...
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We herein present the first annotated anuran checklist for the Brazilian state of Amapá, eastern Amazonia, based on a thorough literature review. We recorded the occurrence of 111 species belonging to 13 anuran families distributed across 48 localities throughout Amapá, within two biomes. Among these species, 62.5% occur exclusively in the Tropical Moist Broadleaf Forest biome, ~8% occur exclusively in the Tropical Savanna biome, and ~29% occur in both. Two species were considered endemic to Amapá and were registered only in the central portion of the state. Regarding the conservation status, only one species (Dendropsophus amicorum) is classified as threatened, assigned to the "critically endangered" category. The other species are categorized as either "least concern" or "data deficient" (85 and 8, respectively), whereas 21 are not evaluated. The current annotated list contributes to the incipient knowledge on anuran species richness in Amapá and, despite the research regarding anuran taxonomy has considerably progressed over the past 20 years, there is still much to do. Our data highlight the need for trained taxonomists to develop research in the state.
... Many previous studies differentiated Amazonian forest types in their analyses (Draper et al., 2019;Emilio et al., 2010;Oliveira-Filho et al., 2021;Stropp et al., 2009;ter Steege et al., 2019), and others considered terra firme and floodplain forests (Assis et al., 2017;Bredin et al., 2020;Myster, 2017), or submontane and terra firme forests (Macía, 2008;Macía et al., 2007;Macía & Svenning, 2005). ...
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The latitudinal biodiversity gradient is considered a first‐order biogeographical pattern for most taxonomic groups. Latitudinal variation in plant diversity is not always consistent, and this could be related to the particular characteristics of different forest types. In this study, we compare latitudinal changes in floristic diversity (alpha diversity), composition (beta diversity) and dominance across different tropical forest types: floodplain, terra firme and submontane forests. Western Amazonia (Ecuador, Peru and Bolivia). Woody plants. We inventoried 1978 species and 31,203 individuals of vascular plants with a diameter at breast height ≥ 2.5 cm in 118 0.1‐ha plots over an 1800 km latitudinal gradient in three different forest types. The relationships between alpha diversity, latitude and forest type were analysed using generalised linear mixed models. Semi‐parametric permutational multivariate analysis of variance was used to investigate the effects of latitude and forest type on beta diversity. Dominant species abundances were correlated with non‐metric multidimensional scaling ordination axes to reflect their contributions in shaping changes in beta diversity. Alpha diversity increased towards equatorial latitudes in terra firme and submontane forests but remained relatively constant in floodplains. Beta diversity of all forest types changed with latitude, although less clearly in floodplains. Also, in floodplain forests, there were fewer dominant species contributing to beta diversity and more species homogeneous along the gradient. Latitudinal diversity patterns are manifested in alpha and beta diversity since latitude summarizes climatic and edaphic changes. However, we found different responses of each forest type. In floodplain forests, inundation regime is a stronger predictor than latitude, limiting floristic diversity and composition. Changes in dominant species abundance over gradients exapined species composition, but floodplain forests haboured more homogeneous dominant species than well drained forests. It is easy to study environmental trends and habitat characteristics of each forest type to understand their species diversity and dominance patterns. El gradiente latitudinal representa un patrón biogeográfico de gran importancia para muchos grupos taxonómicos. No obstante, las variaciones latitudinales en la diversidad vegetal no siempre coinciden, debido a las características físicas y biológicas de los diferentes tipos de bosque. En este estudio, comparamos los cambios en diversidad florística (diversidad alfa), composición (diversidad beta) y dominancia de diferentes tipos de bosque (inundables, tierra firme y submontanos) a lo largo del gradiente latitudinal. Amazonia occidental (Ecuador, Perú, Bolivia). Plantas leñosas. Inventariamos 1978 especies y 31,203 individuos de plantas vasculares leñosas con un diámetro a la altura del pecho ≥2.5 cm en 118 parcelas de 0.1 ha, a lo largo de un gradiente latitudinal de 1800 km en tres tipos de bosque. La relación entre diversidad alfa, latitud y tipo de bosque fue analizada con modelos mixtos lineales generalizados (GLMMs). Se utilizó el análisis multivariante de la varianza semi‐paramétrico con permutaciones para investigar los efectos de la latitud y del tipo de bosque sobre la beta diversidad. La abundancia de especies dominantes se correlacionó con los ejes de un análisis multidimensional no‐métrico (NMDS) para explicar la contribución de dichas especies a los patrones de beta diversidad observados. La diversidad alfa de los bosques de tierra firme y submontanos incrementó hacia el ecuador, mientras que la de los bosques inundables se mantuvo más constante a lo largo del gradiente latitudinal. La diversidad beta de todos los tipos de bosque varió con la latitud, aunque menos pronunciadamente para bosques inundables. Además, en los bosques de inundables se encontraron menos especies dominantes contribuyendo a la diversidad beta y más especies dominantes distribuidas homogéneamente a lo largo del gradiente. Los patrones de diversidad latitudinal se manifiestan en la diversidad alfa y beta, ya que la latitud resume los cambios climáticos y edáficos. Sin embargo, encontramos respuestas diferentes en cada tipo de bosque. En los bosques inundables, el régimen de inundación es un predictor más fuerte que la latitud, limitando la riqueza de especies y la composición florística. Los cambios en la abundancia de especies dominantes a lo largo de los gradientes explicaron la composición de especies, pero los bosques inundables albergaron especies dominantes más homogéneas en su abundancia que los bosques bien drenados. Es fundamental comprender las tendencias ambientales y las características del hábitat de cada tipo de bosque para entender su divesidad de especies y patrones de dominancia.
... The interviews with former traders and people living at communities visited revealed that until the end of the commercialization period during the 1980s, extraction of resin in Santarém mainly occurred on terra firme formations near rivers, the main route of flow products (the definition of terra firme used here and beyond is following Oliveira-Filho et al. 2021). According to them, forests on plateaus were relatively poorly explored due to the distance to navigable waterways. ...
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Amazonia contains the largest remnant of continuous forest on the planet. In Brazil, it represents nearly 45% of the territory but contributes little to the country’s economy. This work discusses the use of jutaicica copal resin extracted from tree species of the genus Hymenaea (Fabaceae), which once represented a considerable part of the economy of Pará state. We present a review of its historical use, explore how and for what purpose the resin is extracted, and characterize it based on thermal and spectroscopic techniques. In western Pará state, jutaicica is gathered mainly from two species, H. courbaril and H. parvifolia, and in the past was used as a valuable source for varnish production. The resins from these species are distinctive according to thermal and spectroscopic methods. Thermal analysis shows H. courbaril might be a better source for polymer gathering. Infrared spectra can be accurately used to differentiate sources and demonstrate more uniformity in samples from H. courbaril, which is corroborated by the 13C-RMN spectra of the analyzed batches. Jutaicica is one of many non-timber forest products lacking investments for economic reintegration, an important contribution of income in extractive reserves, which play a key role in the conservation of Amazonia.
... Fern species richness represented the total number of species recorded at each site. Fern composition was measured using the first axes of a non-metric multidimensional scaling (NMDS), calculated from species abundance values [39], a standard approach used in the literature to assess species composition in regression models [28]. To assess the completeness of our sampling and to estimate the potential total number of forest fern species in Xishuangbanna, we used the Chao2 species richness estimator [40]. ...
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Understanding how forest fragment size, topography, forest structure, and soil properties affect plant diversity remains a crucial question in conservation biology, with ferns often being un-derstudied. To address this knowledge gap, we surveyed the abundance, species richness, and composition of ferns in a tropical landscape in south China using 75 sites in 42 forest fragments. We then used a multi-model inference approach to assess whether fern abundance, richness, and composition were better explained by (a) fragment size, (b) topography (slope, aspect), (c) forest structure (tree basal area, light availability), or (d) soil properties (pH, Carbon, Nitrogen, Phosphorous, Calcium , Magnesium, water availability, and proportion of clay, silt, and sand). We also conducted a nestedness analysis to examine whether the composition of the fern communities in smaller fragments (0.4-1 km²) differed or represented a subset of the communities found in larger fragments (e.g., >10 km²). We found that (a) fern abundance was mostly influenced by soil properties, slope, and aspect, (b) fern species richness by soil properties and slope, and (c) fern species composition by forest structure, specifically, tree basal area. We also found that fern species composition was not nested in the landscape, suggesting that smaller forest fragments had different communities from larger fragments. Our results suggest also that soil properties play an important role in maintaining fern abundance and diversity and therefore protecting soil can help conserve ferns in fragmented landscapes.
... Climatic seasonality has been suggested to be the most important environmental condition defining the main boundaries of Neotropical bioregions (6), the floristic distinctions between neighboring evergreen, deciduous and semideciduous forests (12,13), and the dominant functional traits of moist forests (14). Biogeographical patterns in floristic variation have been documented for old-growth forests (15)(16)(17)(18), but not for the subset of species that colonize successional forests in human-modified landscapes across the Neotropics. ...
... This huge forest territory is far from uniform, containing different forest types like upland forests (terra firme), seasonally inundated floodplains (várzeas and igapós), coastal forest (restingas) and savanas (white-sand forests, campinaranas), among others (Junk et al., 2011). Earlier studies have indicated that these forest types differ in their structure and species composition (Oliveira-Filho et al., 2021). The Andes-Amazonia interface is one of the most important speciation centers for epiphytes , and Western Amazonian forests have been assumed to host a substantially richer epiphyte flora compared to other Amazonian regions (Gentry and Dodson, 1987;Kreft et al., 2004;Küper et al., 2004). ...
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Epiphytes are still an understudied plant group in Amazonia. The aim of this study was to identify distributional patterns and conservation priorities for vascular epiphyte assemblages (VEA) across Amazonia. We compiled the largest Amazonian epiphyte plot database to date, through a multinational collaborative effort of 22 researchers and 32 field sites located across four Amazonian countries – the Amazonian Epiphyte Network (AEN). We addressed the following continental-scale questions by utilizing the AEN database comprising 96,448 epiphyte individuals, belonging to 518 vascular taxa, and growing on 10,907 tree individuals (phorophytes). Our objectives here are, first, to present a qualitative evaluation of the geographic distribution of the study sites and highlight regional lacunae as priorities for future quantitative inventories. Second, to present the floristic patterns for Amazonia-wide VEA and third, to combine multivariate analyses and rank abundance curves, controlled by major Amazonian habitat types, to determine how VEA vary geographically and ecologically based on major Amazonian habitat types. Three of the most striking patterns found are that: (1) VEA are spatially structured as floristic similarity decays with geographic distance; (2) a core group of 22 oligarchic taxa account for more than a half of all individuals; and (3) extensive floristic sampling gaps still exist, mainly across the highly threatened southern Amazonian deforestation belt. This work represents a first step toward unveiling distributional pattern of Amazonian VEA, which is important to guide future questions on ecology and species distribution ranges of VEA once the collaborative database grows allowing a clearer view of patterns.
The detection of Solar-Induced chlorophyll Fluorescence (SIF) by remote sensing has opened new perspectives on ecosystem studies and other related aspects such as photosynthesis. In general, fluorescence high-resolution studies were limited to proximal sensors, but new approaches were developed to improve SIF resolution by combining OCO-2 with MODIS orbital observations, improving its resolution from 0.5° to 0.05 on a global scale. Using a high-resolution dataset and rainfall data some SIF characteristics of the satellite were studied based across 06 contrasting ecosystems in Brazil: Amazonia, Caatinga, Cerrado, Atlantic Forest, Pampa, and Pantanal, from years 2015-2018. SIF spatial variability in each biome presented significant spatial variability structures with high R2 values (>0.6, Gaussian models) in all studied years. The rainfall maps were positively and similar related to SIF spatial distribution and were able to explain more than 40% of SIF's spatial variability. The Amazon biome presented the higher SIF values (>0.4 W m-2 sr-1 μm-1) and also the higher annual rainfall precipitation (around 2000 mm), while Caatinga had the lowest SIF values and precipitations (<0.1 W m-2 sr-1 μm-1, precipitation around 500 mm). The linear relationship of SIF to rainfall across biomes was mostly significant (except in Pantanal) and presented contrasting sensitivities as in Caatinga SIF was mostly affected while in the Amazon, SIF was lesser affected by precipitation events. We believe that the features presented here indicate that SIF could be highly affected by rainfall precipitation changes in some Brazilian biomes. Combining rainfall with SIF allowed us to detect the differences and similarities across Brazil's biomes improving our understanding on how these ecosystems could be affected by climate change and severe weather conditions.
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Clear and data-driven bioregionalizations can provide a framework to test hypotheses and base biodiversity conservation. Here we used occurrence and abundance data in combination with objective analytical methods to propose two bioregionalization schemes for tree species of the Cerrado and the Pantanal in South America. We also evaluated the contribution of three sets of determinants of the occurrence- and abundance-based subregions. We compiled data on tree species composition from 894 local assemblages based on species occurrences, and from 658 local assemblages based on species abundances. We used an unconstrained community-level modelling approach and clustering techniques to identify and map tree subregions for the occurrence and the abundance data sets, separately. Hierarchical clustering analyses were conducted to investigate floristic affinities between the subregions and to map broader floristic regions. We used multinomial logistic regression models, deviance partitioning, and rank-sum tests to assess the main subregion correlates. We identified 18 occurrence- and four abundance-based subregions in the Cerrado and the Pantanal. The hierarchical classifications grouped the occurrence-based subregions into nine floristic zones and abundance-based subregions into two broad floristic zones. Variation in subregions were explained mainly by environmental factors and spatial structure in both occurrence and abundance data sets. The occurrence- and abundance-based subregions are complementary approaches to disentangle macroecological patterns and to plan conservation efforts in the Cerrado and the Pantanal. Our findings based on occurrence data revealed more complex and interdigitated boundaries between subregions of tree species than previously reported. The environment, historical stability, and human effects act in a synergetic way on the distribution of the subregions. Finally, the relevance of contemporary environmental factors to the subregion patterns we found alert us to the profound impact global warming may have on the spatial organization of the Cerrado-Pantanal tree flora.
Amazonia has a very high, although still incompletely known, species diversity distributed over a mosaic of heterogeneous habitats that are also poorly characterized. As a result of this multi‐faceted complexity, Amazonia poses a great challenge to geogenomic approaches that strive to find causal links between Earth's geological history and biotic diversification, including the use of genomic data to solve geologic problems. This challenge is even greater because of the need for interdisciplinary approaches despite the difficulties of working across disciplines, where misinterpretations of the literature in disparate research fields can produce unrealistic scenarios of biotic‐geologic linkages. The exchange of information and the joint work of geologists and biologists are essential for building stronger and more realistic hypotheses about how past climate may have affected the distribution and connectivity among populations, how the evolution of drainage networks influenced biotic diversification, and how ecological traits and species interactions currently define the spatial organization of biodiversity, and thus how this organization has changed in the past and may change in the future. The heterogeneity of Amazonia and the different effects of historical processes over its distinct regions and ecosystems have to be more completely recognized in biogeography, conservation; and policymaking. In this perspective, we provide examples of geological, climatological; and ecological information relevant to studies of biotic diversification in Amazonia, where recent advances (and their limitations) may not be apparent to researchers in other fields. The three examples, which include the limitations of climate model outputs, the complicated evolution of river drainages; and the complex link between species and their habitats modulated by ecological specialization, are a small subsample intended to illustrate the urgency for more integrated interdisciplinary approaches.
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Open habitats such as grasslands occupy < 5% of the Amazon and are currently grouped under the broad term Amazonian savanna, covering an area of c. 267 000 km 2 , mostly in Brazil and Bolivia. These habitats are found isolated within an extensive rainforest matrix, having a distinct flora from the latter. The lower Amazon River is home to several patches of savanna that occupy both south and north banks of the river, in Santarém, Alenquer and Monte Alegre. Although having an abundance of herbaceous plants, most studies on these open areas focus only on tree species, ignoring the relevant non-woody component of the vegetation. Our objectives were to provide new surveys of seed plants for two Amazonian savanna sites and to take the opportunity to revisit the biogeographical links between Amazonian savanna, Amazonian canga vegetation and the central Brazilian cerrado (CBC) and caatinga, analysing woody and herbaceous plants. We created a floristic database that includes sites of Amazonian savannas, including campinarana, coastal scrub (restinga), CBC and Amazonian campos rupestres (on canga or other substrate). We compared those sites using multivariate analyses to find out the degree of floristic resemblance between sites. We prepared a new list of 406 species of seed plants [336 in Parque Estadual de Monte Alegre (PEMA) and 117 in Serra do Itauajuri (SI)], including 23 new records for the state of Pará and some putative new species for science. The Amazonian savannas form three loosely arranged groups, whereas the Amazonian canga formed a cohesive assemblage. Both groups were contrasted against cerrado and caatinga sites and had a distinctive flora from both. Sites from northwestern Pará (Alter do Chão, PEMA and SI) were grouped with their northern counterparts in Roraima. An improved representation of the flora of these sites is provided, with more insight into the relationship between the Amazonian savanna sites and other vegetation types. It is worrying that recent changes of the Brazilian legislation place open environments, such as PEMA, in the path of vulnerability to disturbance and destruction.
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The evolutionary processes underlying the high diversity and endemism in the Cerrado, the most extensive Neotropical savanna, remain unclear, including the factors promoting the presence and evolution of savanna enclaves in the Amazon forest. In this study, we investigated the effects of past climate changes on genetic diversity, dynamics of species range and the historical connections between the savanna enclaves and Cerrado core for Qualea grandiflora, a tree species widely distributed in the biome. Totally, 40 populations distributed in the Cerrado core and Amazon savannas were analyzed using chloroplast and nuclear DNA sequences. We used phylogeographic, coalescent and ecological niche modeling approaches. Genetic data revealed a phylogeographic structure shaped by Pleistocene climatic oscillations. An eastern-western split in the Cerrado core was observed. The central portion of the Cerrado core harbored most of the sampled diversity for cpDNA. Ecological niche models predicted the presence of a large historical refuge in this region and multiple small refuges in peripheral areas. Relaxed Random Walk (RRW) models indicated the ancestral population in the north-western border of the central portion of the Cerrado core and cyclical dynamics of colonization related to Pleistocene climatic oscillations. Central and western ancient connections between Cerrado core and Amazonian savannas were observed. No evidence of connections among the Amazonian savannas was detected. Our study highlights the importance of Pleistocene climatic oscillations for structuring the genetic diversity of Q. grandiflora and complex evolutionary history of ecotonal areas in the Cerrado. Our results do not support the recent replacement of a large area in the Amazon forest by savanna vegetation. The Amazonian savannas appear to be fragmented and isolated from each other, evolving independently a long ago.
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We determined the filtered tree species pool of Amazonian wetland forests, based on confirmed occurrence records, to better understand how tree diversity in wetland environments compares to tree diversity in the entire Amazon region. The tree species pool was determined using data from two main sources: 1) a compilation of published tree species lists plus one unpublished list of our own, derived from tree plot inventories and floristic surveys; 2) queries on botanical collections that include Amazonian flora, curated by herbaria and available through the SpeciesLink digital biodiversity database. We applied taxonomic name resolution and determined sample-based species accumulation curves for both datasets, to estimate sampling effort and predict the expected species richness using Chao’s analytical estimators. We report a total of 3 615 valid tree species occurring in Amazonian wetland forests. After surveying almost 70 years of research efforts to inventory the diversity of Amazonian wetland trees, we found that 74% these records were registered in published species lists (2 688 tree species). Tree species richness estimates predicted from either single dataset underestimated the total pooled species richness recorded as occurring in Amazonian wetlands, with only 41% of the species shared by both datasets. The filtered tree species pool of Amazonian wetland forests comprises 53% of the 6 727 tree species taxonomically confirmed for the Amazonian tree flora to date. This large proportion is likely to be the result of significant species interchange among forest habitats within the Amazon region, as well as in situ speciation processes due to strong ecological filtering. The provided tree species pool raises the number of tree species previously reported as occurring in Amazonian wetlands by a factor of 3.2.
Open habitats such as grasslands occupy < 5% of the Amazon and are currently grouped under the broad term Amazonian savanna, covering an area of c. 267 000 km2, mostly in Brazil and Bolivia. These habitats are found isolated within an extensive rainforest matrix, having a distinct flora from the latter. The lower Amazon River is home to several patches of savanna that occupy both south and north banks of the river, in Santarém, Alenquer and Monte Alegre. Although having an abundance of herbaceous plants, most studies on these open areas focus only on tree species, ignoring the relevant non-woody component of the vegetation. Our objectives were to provide new surveys of seed plants for two Amazonian savanna sites and to take the opportunity to revisit the biogeographical links between Amazonian savanna, Amazonian canga vegetation and the central Brazilian cerrado (CBC) and caatinga, analysing woody and herbaceous plants. We created a floristic database that includes sites of Amazonian savannas, including campinarana, coastal scrub (restinga), CBC and Amazonian campos rupestres (on canga or other substrate). We compared those sites using multivariate analyses to find out the degree of floristic resemblance between sites. We prepared a new list of 406 species of seed plants [336 in Parque Estadual de Monte Alegre (PEMA) and 117 in Serra do Itauajuri (SI)], including 23 new records for the state of Pará and some putative new species for science. The Amazonian savannas form three loosely arranged groups, whereas the Amazonian canga formed a cohesive assemblage. Both groups were contrasted against cerrado and caatinga sites and had a distinctive flora from both. Sites from north-western Pará (Alter do Chão, PEMA and SI) were grouped with their northern counterparts in Roraima. An improved representation of the flora of these sites is provided, with more insight into the relationship between the Amazonian savanna sites and other vegetation types. It is worrying that recent changes of the Brazilian legislation place open environments, such as PEMA, in the path of vulnerability to disturbance and destruction.
The Amazon forest covers 7.5 million Km2 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. 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 data‐driven approach based on assemblage composition patterns. 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. 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 were explained jointly by human factors and spatial structure followed by environmental factors and spatial structure combined. Synthesis. Our woody plant subregions differed from WWF 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.
The forests of Western Amazonia are among the most diverse tree communities on Earth, yet this exceptional diversity is distributed highly unevenly within‐ and among communities. In particular, a small number of dominant species account for the majority of individuals while the large majority of species are locally and regionally extremely scarce. By definition, dominant species contribute little to local species richness (alpha diversity), yet the importance of dominant species in structuring patterns of spatial floristic turnover (beta diversity) has not been investigated. Here, using a network of 207 forest inventory plots, we explore the role of dominant species in determining regional patterns of beta diversity (community‐level floristic turnover and distance‐decay relationships) across a range of habitat types in northern lowland Peru. Of the 2031 recorded species in our dataset, only 99 of them accounted for 50% of individuals. Using these 99 species it was possible to reconstruct the overall features of regional beta diversity patterns, including the location and dispersion of habitat types in multivariate space, and distance‐decay relationships. In fact, our analysis demonstrated that regional patterns of beta diversity were better maintained by the 99 dominant species than by the 1932 others, whether quantified using species abundance data or species presence/absence data. Our results reveal that dominant species are normally common only in a single forest type. Therefore, dominant species play a key role in structuring Western Amazonian tree communities, which in turn has important implications, both practically for designing effective protected areas, and more generally for understanding the determinants of beta diversity patterns. This article is protected by copyright. All rights reserved.
This chapter intents to contribute to the knowledge of the geographic distribution of tree taxa in Brazilian igapó forest and presents an analysis of the distribution of tropical tree species from periodic flooded areas, focusing on the description and interpretation of the patterns of local, regional and global. We used 19 floristic and phytosociological works carried out in periodically flooded forests of the Rio Negro basin, Brazilian Amazon, and classified them according to the occurrence area of tree species using the phytogeography patterns established by Prance (1977). Considering the different possibilities of occurrence of a taxon in the Amazon biome, we defined three possible tree species geographic patterns: AA – ample amazon; FP – floodplain area; and BW – black water. For each taxon we calculated the frequency of occurrence. For each phytogeographic pattern we investigated the occurrence of each taxon in other formations out of the Amazon forest, according to the five biomes by IBGE classification: Cerrado (CE), Caatinga (CA), Pantanal (PA), Mata Atlântica (MA) and Pampa (PP). In all, 19 surveys were selected; the specific richness of at least 636 woody taxa was recognized. Of these, 380 species are duly determined and belong to 211 genera and 62 families. We checked 231 species with wide distribution on the Amazon (AA), 65 occur only on floodplain (FP), 61 occur only near black water river (BW), 7 are restricted to one formation on Amazon and 16 species are not registered on Species Link site. The majority of the species BW are considered rare (59%) and only 12 species (19.7%) occur in other Brazilian biome. We observed the same with floodplain species (FP), only 12.3% also occur in other Brazilian biome. In general, the most constant/moderately frequent species in the igapó forest showed large geographic amplitude occurring in other Brazilian biomes. A great proportions of them also occurred in cerrado (CE), followed by Atlantic rain forest (MA). The fact that about 37.6% of all species occurred also in other formations, 43.1 % of genera and 69.4 % of families in igapó forest also occur out of Amazon forest.