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Using tree species inventories to map biomes and assess their climatic overlaps in lowland tropical South America
... The lowland biomes in NE Brazil include dry forest (or seasonally dry tropical forest; SDTF), savanna, semi-deciduous forest and humid forest (Queiroz, Cardoso, Fernandes, & Moro, 2017;Silva de Miranda et al., 2018). Semi-deciduous forest is intermediate in physiognomy between dry and evergreen humid forest , while being floristically closer to humid forest Silva de Miranda et al., 2018). ...
... The lowland biomes in NE Brazil include dry forest (or seasonally dry tropical forest; SDTF), savanna, semi-deciduous forest and humid forest (Queiroz, Cardoso, Fernandes, & Moro, 2017;Silva de Miranda et al., 2018). Semi-deciduous forest is intermediate in physiognomy between dry and evergreen humid forest , while being floristically closer to humid forest Silva de Miranda et al., 2018). We retain it as a distinct unit, but it could be combined with either dry forest (sensu Pennington, Prado, & Pendry, 2000) (Queiroz et al., 2017). ...
... The comparative s-SDM analysis and comparative inventory analysis both resulted in the recognition of four biomes similar in geographical distributions and floristic composition to those detected in previously published analyses (Queiroz et al., 2017;Silva de Miranda et al., 2018) and, in most cases, their functional identity. This indicates that s-SDMs are able to recover macroecological patterns with accuracy. ...
Aim: To test whether species distribution models (SDMs) can reproduce major macroecological patterns in a species-rich, tropical region and provide recommendations for using SDMs in areas with sparse biotic inventory data.
Location: Northeast Brazil, including Minas Gerais.
Time period: Present.
Major taxa studied: Flowering plants.
Methods: Species composition estimates derived from stacked SDMs (s-SDMs) were compared with data from 1,506 inventories of 933 woody plant species from northeast Brazil. Both datasets were used in hierarchical clustering analyses to delimit floristic units that correspond to biomes. The ability of s-SDMs to predict the identity, functional composition and floristic composition of biomes was compared across geographical and environmental space.
Results: The s-SDMs and inventory data both resolved four major biomes that largely corresponded in terms of their distribution, floristics and function. The s-SDMs proved excellent at identifying broad-scale biomes and their function, but misas-signed many individual sites in complex savanna-forest mosaics.
Main conclusions: Our results show that s-SDMs have a unique role to play in describing macroecological patterns in areas lacking inventory data and for poorly known taxa. s-SDMs accurately predict floristic and functional macroecological patterns but struggle in areas where non-climatic factors, such as fire or soil, play key roles in governing distributions.
... fact, the discontinuity of neotropical rain forests is probably related to geological events, such as the uplift of the Andes (Hoorn et al., 2010), and to historical climatic events, such as the expansion of open vegetation in the Neotropics favored by the increase of seasonality during the Upper Miocene (Prado and Gibbs, 1993;Jaramillo et al., 2010). There are marked differences in the composition of the tree flora between blocks of neotropical rain forests, such as Amazon and Atlantic Forest (Miranda et al., 2018). However, these differences ...
... Neotropical rain forests occur as discontinuous blocks across the Americas, which, although physiognomically very similar, present floristic variations (Oliveira-Filho and Fontes, 2000;Rangel, 2004;Santiago-Valentin and Olmstead, 2004;Bruijnzeel et al., 2011;Antonelli et al., 2018;Miranda et al., 2018). Although many of these forests have been recognized as distinct units based on floristic knowledge (Gentry, 1982a;Burnham and Graham, 1999;Miranda et al., 2018), a comprehensive analysis using formal biogeographical methods and covering all the Neotropics is still lacking. ...
... Neotropical rain forests occur as discontinuous blocks across the Americas, which, although physiognomically very similar, present floristic variations (Oliveira-Filho and Fontes, 2000;Rangel, 2004;Santiago-Valentin and Olmstead, 2004;Bruijnzeel et al., 2011;Antonelli et al., 2018;Miranda et al., 2018). Although many of these forests have been recognized as distinct units based on floristic knowledge (Gentry, 1982a;Burnham and Graham, 1999;Miranda et al., 2018), a comprehensive analysis using formal biogeographical methods and covering all the Neotropics is still lacking. ...
Questions
We investigated tree floristic variation among the Neotropical Non‐Flooded Evergreen Forests (NEF). We addressed the following questions: (a) which are the floristic groups among NEF and how are they correlated with environmental variables; (b) how many species, genera and families are shared between these floristic groups and which species are unique and indicative of each one; and (c) how does species richness vary between NEF groups?
Location
Neotropical region.
Methods
We used cluster and ordination analyses based on 518,004 tree occurrence data available in the NeoTropTree database to identify floristic groups throughout NEF. From the floristic groups identified here, we (a) verified correlations between floristic composition and precipitation, temperature, altitude, and latitude; (b) calculated the number of shared species, genera and families, and identified taxa unique to each group; and (c) obtained indicator species and estimated species richness for these floristic groups.
Results
We recorded 172 families, 1,276 genera and 15,134 species in 1,885 sites of NEF. The families most rich in species were Fabaceae, Rubiaceae and Myrtaceae. We identified nine groups among the NEF, which broadly correspond to floristic provinces reported in the literature. Altitude and annual mean temperature were associated with a species turnover gradient from Amazon to Andean Cloud Forest. Atlantic Forest (south) and Mesoamerica plus Caribbean (north) represented the extremes of a latitudinal gradient. The Atlantic Forest presented the largest number of exclusive and indicator species (2,477 and 265, respectively), while the Amazon showed the highest species richness (6,167 species).
Conclusions
Although it was possible to separate NEF into distinct floristic groups, this floristic dissociation seems to be recent, since it found support only in species data. The floristic groups identified in this study are largely congruent with their geographic distribution and spatial/ecological isolation, and seem to reflect historical, geological and climatic events that occurred in the Neotropics.
... On more local scales, climate predictors usually play a secondary role, while edaphic and topographic gradients are stronger predictors of vegetation (Trejo & Dirzo, 2002;Phillips et al., 2003;Pitman et al., 2008;Eisenlohr et al., 2013). However, evidence from recent studies supports the view that soils and substrate-related factors are major drivers of vegetation also on a macroecological scale (see, for instance, Neves et al., 2017;Miranda et al., 2018;Oliveira-Filho et al., 2021). Finally, the recognition of dispersal limitation as a key determinant of floristic variation between areas has provided important contributions to understanding patterns of species composition in plant assemblages (Antonelli et al., 2009;Quintana et al., 2017). ...
... Thus, NNFEFs experience wide latitudinal, altitudinal and longitudinal gradients, implying considerable environmental and spatial variations across their range (e.g., Cupertino-Eisenlohr et al., 2021). Floristic variation along these environmental gradients can be seen along disjunct NNFEF regions such as the Atlantic, Amazon, Tropical Andes, Choco, Mesoamerica and Caribbean (Asprey, 1959;Gentry, 1982a;Henderson et al., 1991;Miranda et al., 2018). A recent study based on a large data set spanning the whole extension of NNFEFs has confirmed previous works by demonstrating that those disjunct regions represent distinct floristic groups (Cupertino-Eisenlohr et al., 2021). ...
... We found a clear distinction between the Amazon, Atlantic Forest, and to a lesser degree the Andean Cloud Forest from other NNFEF groups, which highlights the floristic and environmental uniqueness of these groups. Biotic and environmental differentiation of Amazon and Atlantic Forest has also been evidenced in recent studies (Sobral-Souza et al., 2015;Ledo & Colli, 2017;Miranda et al., 2018). On the other hand, we found environmental characteristics that overlapped among the Caribbean, Mesoamerica and SANFL. ...
Questions
We examined the drivers of tree species variation across Neotropical non‐flooded evergreen forests (NNFEFs) to answer the following questions: Can floristic groups be differentiated based on environmental predictors? How do bioclimatic, topographic, edaphic predictors and dispersal barriers contribute to explain the floristic variation throughout NNFEFs?
Location
Neotropical region.
Methods
Based on 1,843 sites (circular areas with a diameter of 10 km), 15,072 species and 509,793 occurrence records of trees, as well as on environmental variables (42 bioclimatic, 13 edaphic and four topographic variables) and dispersal barriers (based on ecological and geographical dispersal suitability), we tested whether environmental predictive variables can discriminate NNFEF floristic groups, and built canonical models and variation partitioning to assess which variables contributed most to the floristic variation.
Results
Despite extensive overlap in predictive variables, Amazon and Atlantic Forest were the most differentiated among the nine NNFEF groups. Floristic variation along NNFEFs was mainly determined by environmental factors (54.1%), with topographic and edaphic variables, mainly topographic wetness index and pH respectively, representing the most important predictors followed by a combination of environmental factors and dispersal barriers (22.7%). The pure dispersal barriers fraction also contributed significantly to our model (3.7%), especially considering the second canonical axis.
Conclusions
The high importance of soil and topographic variables indicates that the species have a relatively narrow niche driven by such factors, suggesting that conservation strategies should not be generalized for NNFEFs. In addition, dispersal barriers do not seem to have prevented floristic exchanges between most NNFEF groups, except in the Atlantic Forest.
... The intermediate disturbance hypothesis (Connell, 1978) posits that if a disturbance is not too extreme, many plant lineages may already have or can evolve traits required to survive it, but the more extreme the disturbance (e.g., extreme drought and extreme cold or extreme heat), an increasingly small number of species will have these traits because they are hard to evolve. Quantitative evidence across floras is now needed to understand the relative roles of niche conservatism and the species-environment interactions (environmental filtering) across ecological gradients, particularly in the Neotropics where much biome complexity is found Hughes et al., 2013;Dexter et al., 2018;Silva-de-Miranda et al., 2018). ...
... We applied our biome delimitation approaches to NE Brazil because of our long-term experience working on the taxonomy, distribution, ecology, and evolution of flowering plants in the region (e.g., Rocha et al., 2004;Queiroz, 2006;Queiroz et al., 2010Queiroz et al., , 2017Särkinen et al., 2011;Santos et al., 2012;Cardoso et al., 2014;Fernandes et al., 2020;Moonlight et al., 2020). We defined our study area as NE Brazil (including the state of Minas Gerais) in order to include all areas defined as the Caatinga by Instituto Brasileiro de Geografia e Estatística [IBGE] (2012) and alternative biome classifications (e.g., Queiroz et al., 2017;Silva-de-Miranda et al., 2018;Moonlight et al., 2020). We have a particular interest in identifying "core" areas that are relatively homogenous in floristic, functional, and phylogenetic space, so it was important to include areas of all biomes that surround the Caatinga (i.e., areas known to differ in these respects). ...
... The results do not adequately capture the biome complexity in Brazil. For example, Ringelberg et al. (2020) delimit not just the Caatinga as succulent biome, but also parts of the Chaco and the campos rupestres of the Chapada Diamantina, which are ecologically, historically, and functionally distinct biomes (Pennington et al., 2000;DRYFLOR, 2016;Silva-de-Miranda et al., 2018;Rapini et al., 2021). Indeed, we demonstrate that not just the "core" Caatinga but also transitional and non-Caatinga areas have high proportions of stem succulents (Figure 4B). ...
While we have largely improved our understanding on what biomes are and their utility in global change ecology, conservation planning, and evolutionary biology is clear, there is no consensus on how biomes should be delimited or mapped. Existing methods emphasize different aspects of biomes, with different strengths and limitations. We introduce a novel approach to biome delimitation and mapping, based upon combining individual regionalizations derived from floristic, functional, and phylogenetic data linked to environmentally trained species distribution models. We define “core Biomes” as areas where independent regionalizations agree and “transition zones” as those whose biome identity is not corroborated by all analyses. We apply this approach to delimiting the neglected Caatinga seasonally dry tropical forest biome in northeast Brazil. We delimit the “core Caatinga” as a smaller and more climatically limited area than previous definitions, and argue it represents a floristically, functionally, and phylogenetically coherent unit within the driest parts of northeast Brazil. “Caatinga transition zones” represent a large and biologically important area, highlighting that ecological and evolutionary processes work across environmental gradients and that biomes are not categorical variables. We discuss the differences among individual regionalizations in an ecological and evolutionary context and the potential limitations and utility of individual and combined biome delimitations. Our integrated ecological and evolutionary definition of the Caatinga and associated transition zones are argued to best describe and map biologically meaningful biomes.
... The range boundaries of the tropical dry forest biome should coincide with climatic thresholds related to temperature, mean annual rainfall, seasonality, and water deficit [17,20,33]. ...
... There are a number of ways to validate and refine bioclimatic assessments of the tropical dry forest biome. Results can be compared to local vegetation maps [33,36], high resolution (< 1 m) remote sensing imagery [17], and field inventories or georeferenced specimens [8,33,36]. Field plots, however, offer the most robust approach to validating bioclimatic models because they provide high resolution data on location, species composition, and structure over a standardize area [37]. ...
... There are a number of ways to validate and refine bioclimatic assessments of the tropical dry forest biome. Results can be compared to local vegetation maps [33,36], high resolution (< 1 m) remote sensing imagery [17], and field inventories or georeferenced specimens [8,33,36]. Field plots, however, offer the most robust approach to validating bioclimatic models because they provide high resolution data on location, species composition, and structure over a standardize area [37]. Furthermore, field ecologists are often familiar with a site's natural history and have identified the vegetation and function as a tropical dry forest. ...
There is a debate concerning the definition and extent of tropical dry forest biome and vegetation type at a global spatial scale. We identify the potential extent of the tropical dry forest biome based on bioclimatic definitions and climatic data sets to improve global estimates of distribution, cover, and change. We compared four bioclimatic definitions of the tropical dry forest biome–Murphy and Lugo, Food and Agriculture Organization (FAO), DryFlor, aridity index–using two climatic data sets: WorldClim and Climatologies at High-resolution for the Earth’s Land Surface Areas (CHELSA). We then compared each of the eight unique combinations of bioclimatic definitions and climatic data sets using 540 field plots identified as tropical dry forest from a literature search and evaluated the accuracy of World Wildlife Fund tropical and subtropical dry broadleaf forest ecoregions. We used the definition and climate data that most closely matched field data to calculate forest cover in 2000 and change from 2001 to 2020. Globally, there was low agreement (< 58%) between bioclimatic definitions and WWF ecoregions and only 40% of field plots fell within these ecoregions. FAO using CHELSA had the highest agreement with field plots (81%) and was not correlated with the biome extent. Using the FAO definition with CHELSA climatic data set, we estimate 4,931,414 km ² of closed canopy (≥ 40% forest cover) tropical dry forest in 2000 and 4,369,695 km ² in 2020 with a gross loss of 561,719 km ² (11.4%) from 2001 to 2020. Tropical dry forest biome extent varies significantly based on bioclimatic definition used, with nearly half of all tropical dry forest vegetation missed when using ecoregion boundaries alone, especially in Africa. Using site-specific field validation, we find that the FAO definition using CHELSA provides an accurate, standard, and repeatable way to assess tropical dry forest cover and change at a global scale.
... Then, we refined assignments using the biomes suggested by Dexter et al. (2018) and Silva de Miranda et al. (2018), followed by a detailed evaluation from two cactus taxonomist authors (D.C.Z. and N.P.T.). ...
... Based on the proposed classification, we performed two distinct ancestral biome reconstructions: (i) using the SDTF as a broad and azonal biome Pennington et al., 2000;Silva de Miranda et al., 2018); (ii) splitting the SDTF into discrete nuclei (e.g. ...
... For the Neotropical biogeography, the ecoregions (e.g.Olson et al., 2001) or Brazilian phytogeographical domains are (IBGE, 2012) frequently synonymized to biomes as operational units (e.g.Antonelli et al., 2018), but recent studies have been showing a distinctive scenario, with the occurrence of azonal (e.g. SDTF) and interdigitated biomes, especially in the South American dry diagonalSilva de Miranda et al., 2018). Thus, we stress that biogeographical transitions between operational geographical units may not be assumed a priori as biome shifts.Biome transitions/shifts are also generally associated with trait evolution in plant species (Chaparro-Pedrazza & Roos, 2020;Donoghue & Edwards, 2014). ...
The interconnectedness and biotic interchange among Neotropical biomes are thought to play an important role in driving adaptation and diversification. However, how these processes are in synteny to trait evolution in species of open and xeric areas is poorly studied. Here, we investigate the spatial and temporal dimensions of evolution and candidate traits associated with biome shifts in xeric vegetation, focusing on the family Cactaceae. Xeric and open areas of South America. Genus Cereus Mill. (Cactaceae, Cereeae). We applied biogeographical reconstructions on a time‐calibrated phylogeny inferred from multilocus data (ddRAD‐Seq) using Bayesian analyses on BEAST2, species distribution modelling in Maxent, the reconstruction of biome affinities and niche shift analyses based on abiotic traits (climate and soil) using Mk‐model in BioGeoBEARS, and phenotypic trait‐based analysis in Mesquite. The Cerrado domain is the ancestral area of Cereus, with most diversification events occurring in a time of intense orogenesis, climatic changes, and marine regressions within the last 5 Mya. Events of biome transition from the seasonally dry tropical forest (SDTF) were also associated with trait and niche shifts. The diversification of the xerophyte genus Cereus is associated with the climatic and geomorphological instabilities of the Pliocene and Pleistocene epochs. The Cerrado domain states an important region of dispersal for the genus. Some geographical range movements involved biome shifts associated with niche evolution while others were restricted to a simple biogeographical transition without niche change. Particular clades that experienced biome shifts displayed some phenotypic state changes, suggesting a role of biotic traits for environment transition. The results observed in Cereus may be a biogeographical pattern that should be tested with other cactus species, such as Pilosocereus spp., or species of xeric habitats, such as Annonaceae and Vochysiaceae.
... In addition to the presence and absence of species, the NeoTropTree database also includes environmental data for each site (at a 30 arc-second resolution), such as annual temperature, temperature day range, isothermality, temperature seasonality, maximum temperature, minimum temperature, annual temperature range, annual precipitation, precipitation in the wettest period, precipitation in the dry period and precipitation seasonality (obtained from the WorldClim, Hijmans et al. 2005); water deficit duration, water deficit severity, water excess duration and water excess severity (generated by Walter's Climate Diagrams ;Walter 1985); hyper seasonality, days of frost and cloud interception (obtained from interpolating known values as response variables with elevation, latitude and the WorldClim layers as predicting variables), potential evapotranspiration and aridity index (obtained by Zomer et al. 2008), ranked rockiness (% exposed rock), ranked sand (% sand), soil fertility (% base saturation), and ranked salinity (ds/m) (obtained from the Harmonized World Soil Database v 1.2; available at http:// www.fao.org/soils -porta l/soil-surve y/soil-maps-and-datab ases/harmo nized -world -soil-datab ase-v12/en/ and ranked afterwards by mid-class percentage) and ranked drainage and soil water storage (obtained following EMBRAPA's protocol) (Santos et al. 2013), totalling 27 geo-edaphic variables (description, history and NeoTropTree protocol at http:// www.neotr optre e.info). ...
... The greater turnover found among different vegetation types (especially between Atlantic semideciduous forest and Dry Chaco woodlands) allowed us to accept the phylogenetic consistency of these vegetation types. The Chaco biome, separated from the other vegetation types, showed the greatest phylogenetic turnover, in agreement with Silva de Miranda et al. (2018) who found the greatest differentiation in species composition to be between the Chaco and other biomes of the South American lowland. This is especial important for conservation issues, since only ~ 9% of the Chaco biome are covered by protected areas (Nori et al. 2016), and thus, many different lineages may be threatened. ...
In South America the biogeographic history has produced different biomes with different vegetation types and distinct floras. As these vegetation types may diverge in evolutionary histories, we analysed how alpha and beta phylogenetic diversity vary across them and determine the main drivers of variation in phylogenetic diversity. To this end, we compiled a list of 205 sites and 1222 tree species spread over four biomes and eight vegetation types in central South America. For each site we evaluate six measures of evolutionary alpha diversity (species richness, phylogenetic diversity sensu stricto and the standardized effect size of phylogenetic diversity, mean phylogenetic distance and mean nearest taxon distance) and beta diversity (phylogenetic Sorensen’s similarity). We checked the influence of spatial and environmental variables using generalized least squares models. The greatest phylogenetic differentiation was found between west and east of central South America, mainly between the Chaco communities and the other vegetation types, suggesting that species found in this biome come from different lineages, comparing with the others vegetation types. Our results also showed a clustered phylogenetic structure for the Dry chaco woodlands, which may be associated with harsh environmental conditions. In addition to historical process, climatic conditions are the main drivers shaping phylogenetic patterns among the distinct vegetation types. Understanding patterns of phylogenetic diversity and distribution can greatly improves conservation planning and management since it allows the conservation of unique biomes characteristics.
... Moreover, when possible, species inclusion in the dataset was verified by evaluating herbaria vouchers. Both African (23,44,78) and South American (79)(80)(81) datasets have been explored and validated in previous research aiming to investigate macroecological, biogeographic, and evolutionary research questions within continents. Further details on how both datasets were assembled can be found in the references (23,44,(78)(79)(80)(81) and in the SI Appendix, SI Materials and Methods. ...
... Both African (23,44,78) and South American (79)(80)(81) datasets have been explored and validated in previous research aiming to investigate macroecological, biogeographic, and evolutionary research questions within continents. Further details on how both datasets were assembled can be found in the references (23,44,(78)(79)(80)(81) and in the SI Appendix, SI Materials and Methods. Here, we only included checklists of frost-free areas [fourth criterion of (82)] and below 1,750 m of elevation. ...
Significance
Our full-scale comparison of Africa and South America’s lowland tropical tree floras shows that both Africa and South America’s moist and dry tree floras are organized similarly: plant families that are rich in tree species on one continent are also rich in tree species on the other continent, and these patterns hold across moist and dry environments. Moreover, we confirm that there is an important difference in tree species richness between the two continents, which is linked to a few families that are exceptionally diverse in South American moist forests, although dry formations also contribute to this difference. Plant families only present on one of the two continents do not contribute substantially to differences in tree species richness.
... The term "phytogeographic domains" is used by scientific projects as the Flora of Brazil database (Forzza et al., 2010;Flora do Brasil, 2020under construction, 2019. However, others authors and the Brazilian government treat the Cerrado as a biome (e.g., Ribeiro and Walter, 2008;MMA, 2011a;Silva de Miranda et al., 2018;MapBiomas, 2019). We considered in this paper the Cerrado as a phytogeographic domain because this concept emphasizes its variety of vegetative physiognomies, implying that all vegetations types must be conserved and not just a single biome. ...
... Given the numerous academic works that aim to understand the distribution of Brazilian flora, we consider it appropriate to use the current official map (IBGE, 2019), but with the inclusion of cerrado enclaves in other phytogeographic domains since many works address the floristic survey of cerrado outside the central area of the domain (see next section). Silva de Miranda et al. (2018) used tree species inventories to map the main biomes, or phytogeographic domains, of lowland tropical South America, and they show substantial overlap amongst biomes, and their map also indicates these cerrado enclaves. It is also essential to use the Brazilian map within other domains context from countries in the continent to understand the savanna connections through South America (Silva and Bates, 2002;Borghetti et al., 2019;Devecchi et al., 2020). ...
The Cerrado contains a wide variety of vegetation types, and it is known for its high biodiversity but is highly threatened. We review the changes through time of geographical limits, studies on flora distribution patterns, and conservation status of Cerrado. Even with advances in technology, only the first government official map of Cerrado in 1993 included disjunct cerrado vegetations, that is, cerrado enclaves in other phytogeographic domains. The lack of cerrado enclaves delimiting and changes of geographical limits of Cerrado affects the land regulations because Brazilian government programs, or even laws, can be specific to a phytogeographic domain. Cerrado flora distribution presented a consistent pattern among studies along time, in which different regions show high similarity in their floristic composition, namely Biogeographic Districts (BD). We need conservation actions in each BD, since protected areas and deforestation rates are uneven among the BDs. Today, only 8.36% of cerrado are in Conservations Units (CU), far from the goal of 17% by 2020. Only 6.51% of cerrado are Indigenous Lands (IL). Both protected areas (CU and IL) have practically not increased since 2009. Discounting area overlapped, only 14.41% of Cerrado territory is in Protected Areas. The clear-cut deforested area reached 49.9% of Cerrado in 2019. From 2016 to 2019, the average annual deforestation rate is proportionally 78% higher than in Amazon. In recent years, the higher deforestation rates are in the states of North and Northeast of Brazil. We need strategic plans to conserve areas in all Biogeographic Districts, including disjunct cerrado areas, and think out how to reduce deforestation rates and promote sustainability actions.
... Therefore, there is a clear need to use of a richness-free dissimilarity index so that our bioregionalization do not reflect richness gradients and sampling biases instead of the patterns we are aiming to capture (Castro-Insua, Gómez-Rodríguez, & Baselga, 2018). The use of indices not affected by richness gradients like the Simpson index is now a clear recommendation (Castro-Insua et al., 2018) and an emerging consensus, and has been extensively used in biogeographical studies (Cantidio & Souza, 2019;Castro-Insua et al., 2018;Dapporto, Fattorini, Vodǎ, Dincǎ, & Vila, 2014;Kreft & Jetz, 2010;Linder et al., 2012;Miranda et al., 2018;Moura et al., 2016;Silva & Souza, 2018a). Despite the robustness of this dissimilarity index to richness differences, small samples yielding small richness values were almost certainly undersampled in a biodiversity-rich domain like the Amazon and could bias the analyses by being nested within more species-rich assemblages, producing artificially small dissimilarity values. ...
... This means that the observed proportion of shared species between any pair of samples may be smaller than the true proportion of species shared between sites from which the samples came from, producing observed dissimilarity values lower than the real ones. However, it is important to emphasize that sampling variation is inevitable in geographical-scale studies that rely on heterogeneous knowledge assembled along decades or centuries (Banda-R et al., 2016;Cantidio & Souza, 2019;Miranda et al., 2018;Moura et al., 2016;Neves, Dexter, Pennington, Bueno, & Oliveira Filho, 2015;Neves et al., 2017;Oliveira-Filho & Fontes, 2000); and if we regarded it as impeditive to further studies, many opportunities to improve knowledge would be lost. Insufficient sampling is likely to be a permanent bias in all species-rich community and macroecological studies, since intensive sampling of local diversity (e.g. ...
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.
... Clements, 1917;Whittaker, 1970), the biome concept was later expanded to include differences in ecosystem services and functions (e.g. Higgins et al., 2016;Silva de Miranda et al., 2018), with results being compared to terrestrial zoogeographic partitionings (Ficetola et al., 2017;Holt et al., 2012;Wallace, 1876). Over the past three decades, biomes have been increasingly delineated in the ocean system, yet the biotic and environmental factors used to define such biomes vary strongly between studies. ...
... Similar to terrestrial biomes (e.g. Higgins et al., 2016;Silva de Miranda et al., 2018), biomes based on the most abundant species likely capture differences in ecosystem function as well. ...
Biomes are geographical units that can be defined based on biological communities sharing specific environmental and climatic requirements. Contemporary ocean biomes have been constructed based on various approaches. These included the biogeographic patterns of higher trophic level organisms, physical and biogeochemical properties, or bulk biological properties such as chlorophyll-a, but none considered the biogeographic patterns of the first trophic level explicitly, i.e. phytoplankton biogeography. A global description of marine biomes based on phytoplankton and defined in analogy to terrestrial vegetation biomes is still lacking. A bioregionalization based on phytoplankton appears particularly timely, as phytoplankton have a high sensitivity to climatic changes and fuel marine productivity. Here, we partition the global ocean into biomes by using self-organizing maps and hierarchical clustering, drawing on the biogeographic patterns of 536 phytoplankton species predicted from empirical evidence. Our approach reveals eight different biomes at the seasonal scale, and seven at the annual scale. The biomes host characteristic phytoplankton species compositions, and differ in their prevailing environmental conditions. The largest differences in phytoplankton composition are found between a Pacific equatorial biome and other tropical biomes, and between subtropical and high latitude biomes. The Pacific equatorial biome is characterized by species with narrower ecological niches, the tropical and subtropical biomes by cosmopolitan generalists, and the high latitudes by species with a heterogeneous biogeography. The strongest differences between biomes are found along gradients of temperature and macronutrient availability, associated with latitude. We test whether our biomes can be reproduced based on indicator species, or potential co-occurrence networks of species determined from the predicted species distributions that are wide-spread in some but rare in other biomes. We find that our biomes can be reproduced by the 51 species identified, which together form significant species co-occurrences. This suggests that species co-occurrences, rather than individual indicator species drive oceanic biome partitioning at the first trophic level. Our biome partitioning may be especially useful for comparative analyses on the functional implications of phytoplankton organization, and impacts on zoogeographical partitionings. Furthermore, it provides a framework for predicting large-scale changes in phytoplankton community structure due to anthropogenic climate and environmental change.
... To this end, we used the Socio-Ecological Observatory for Southern African Woodlands (SEOSAW 2019) dataset, which included 4,655 plots containing, in total, 699 tree species distributed across 276 genera. This analysis was based on ordination methods in association with different hierarchical clustering algorithms (Kreft and Walter 2010;Fayolle et al. 2014;Dexter et al. 2015;Miranda et al. 2018). ...
The miombo woodlands play a critical role in providing livelihood services and mitigating the effects of climate change. However, the woodlands are increasingly at risk from human-induced pressures that remove woody species, deplete soil nutrients and alter their ecological integrity. There are also indications that climate change will alter plant reproductive processes. The ability of the woodlands to continue to provide goods and services, therefore, hinges on the adoption of sustainable management practices, which address the woodland ecology–food–energy nexus and land tenure complexities under a changing climate. Biodiversity conservation is important and protected areas play a key role in doing so, but appropriate management systems are needed. Many of the dominant woody species are able to regenerate after harvesting by resprouting from the stump. Additionally, species may regenerate through the germination of seed from the soil seed bank. Sustainable management of the miombo, in order to mitigate anthropogenic disturbances, requires the development and application of integrated silvicultural systems, opening the canopy to stimulate and enhance germination of the soil seed reserves and promote the growth of seedlings that have remained dormant under the canopy. Furthermore, there is a need to incorporate local communities and their indigenous knowledge systems in active management.
... This region receives around 2000 mm annual rainfall with lower values into the continent and higher values found at montane areas. Most of the area does not show a climatological water deficit, leading to a low seasonal signal [28]. ...
Detecting disturbances in native vegetation is a crucial component of many environmental management strategies, and remote sensing-based methods are the most efficient way to collect multi-temporal disturbance data over large areas. Given that there is a large range of datasets for monitoring, analyzing, and detecting disturbances, many methods have been well-studied and successfully implemented. However, factors such as the vegetation type, input data, and change detection method can significantly alter the outcomes of a disturbance-detection study. We evaluated the spatial agreement of disturbance maps provided by the Breaks For Additive Season and Trend (BFAST) algorithm, evaluating seven spectral indices in three distinct vegetation domains in Brazil: Atlantic forest, savanna, and semi-arid woodland, by assessing levels of agreement between the outputs. We computed individual map accuracies based on a reference dataset, then ranked their performance, while also observing their relationships with specific vegetation domains. Our results indicated a low rate of spatial agreement among index-based disturbance maps, which itself was minimally influenced by vegetation domain. Wetness indices produced greater detection accuracies in comparison to greenness-related indices free of saturation. The normalized difference moisture index performed best in the Atlantic forest domains, yet performed poorest in semi-arid woodland, reflecting its specific sensitivity to vegetation and its water content. The normalized difference vegetation index led to high disturbance detection accuracies in the savanna and semi-arid woodland domains. This study offered novel insight into vegetation disturbance maps, their relationship to different ecosystem types, and corresponding accuracies. Distinct input data can produce non-spatially correlated disturbance maps and reflect site-specific sensitivity. Future research should explore algorithm limitations presented in this study, as well as the expansion to other techniques and vegetation domains across the globe.
... To this end, we used the Socio-Ecological Observatory for Southern African Woodlands (SEOSAW 2019) dataset, which included 4,655 plots containing, in total, 699 tree species distributed across 276 genera. This analysis was based on ordination methods in association with different hierarchical clustering algorithms (Kreft and Walter 2010;Fayolle et al. 2014;Dexter et al. 2015;Miranda et al. 2018). ...
We describe the current land cover of the miombo woodlands and review both current and future drivers of change that may influence land cover in years to come. We also explore possible future ecological and socio-economic outcomes for the miombo in light of the projected futures for the miombo countries in particular, and for the continent in general. Finally, we assess pathways towards desirable trans formations (i.e. just and sustainable transformations) that secure in the long term the contributions of the miombo to improved quality of life. Climate change, human population growth, urbanisation, agricultural expansion and energy production are the major drivers of change in the miombo. The projected futures (2050) show significant temperature rise coupled with a decline in rainfall, a considerable increase in cropland and urban areas, and a decline in the extent of miombo woodlands. We explore options for decision-makers to support conservation and sustainable development in the miombo woodlands and to facilitate fair and equitable access and sharing of benefits arising from ecosystem services produced in these woodlands. Lastly, our analysis suggests that the combination of three pathways (scenarios) is more likely to lead to just and sustainable futures in miombo woodlands, supporting empowered and thriving local communities.
... The one study cited by Mucina that does construct biomes based on floristic data (Silva de Miranda et al., 2018) can be discarded because of fine taxonomic and geographic scalemeaning the authors are simply reconstructing phytochoria, but, at that scale, phytochoria and biomes overlap. The distinction between biomes and phytochoria is one relevant globally and for broad plant lineages. ...
... No entanto, é importante chamar atenção para o fato de que estas florestas transicionais podem estar subamostradas na região Nordeste. Essa tendência pode ser vista no estudo de Miranda et al. (2018), em que os autores apontam a existência de 115 levantamentos de florestas transicionais entre floresta atlântica (floresta úmida) e cerrado (savana) e 49 levantamentos de florestas transicionais entre floresta atlântica e caatinga (floresta seca). ...
Na região Nordeste as florestas semidecíduas estão sendo substituídas por grandes lavouras e pequenas plantações. Nesse sentido, levantamentos fitossociológicos se fazem importantes por abordar aspectos ligados a estrutura, composição e o estado de conservação dos fragmentos remanescentes ameaçados. Assim objetivou-se descrever a estrutura e composição florística da comunidade arbórea de um fragmento de floresta estacional semidecidual no município de Lagoa Seca, Paraíba, Brasil. Para isso, foram alocadas 25 parcelas permanentes com dimensões de 400m², sendo todos os indivíduos com circunferência à altura do peito > 15 centímetros aferidos. A partir dos dados coletados foram elaboradas listas florísticas, fitossociológicas, gráficos de distribuição de classes de diâmetro e altura, índice de diversidade de Shannon (H') e área basal total da comunidade. Foram amostrados 1835 indivíduos, pertencentes a 76 espécies e 27 famílias botânicas. O índice de Shannon (3,61) foi considerado alto enquanto o valor de área basal total (23,99 m²/ha) foi considerado baixo quando comparados a outros fragmentos semelhantes. Apesar da alta diversidade, o baixo valor de área basal pode estar relacionado aos fatores antrópicos, uma vez que foi percebido que o corte seletivo é constante na área, podendo ser este o mesmo cenário vivenciado por outras áreas ainda não amostradas.
... These long-term tropical rain forest plots have been extremely successful in achieving their primary aim of improving our knowledge of tropical forest ecology, including, for example: the relationships of climate with biomass (Álvarez-Dávila et al., 2017) and forest structure (Feldpausch et al., 2012); the role of diversity in car- Guevara et al., 2016;Levis et al., 2017), continental scale floristic patterns (Esquivel-Muelbert et al., 2017;ter Steege et al., 2006;ter Steege, Pitman, Sabatier, Baraloto, & Salomão, 2013), biome delimitation, and mapping (Silva-de-Miranda et al., 2018), and even facilitated the discovery of species new to science (reviewed by Baker et al., 2017). Repeated censuses of these plots have provided insight into the role of tropical forests in global cycles of carbon, energy, and water (Pan et al., 2011;Phillips et al., 1998), long-term trends in forest dynamics (Brienen et al., 2015), and the impacts of extreme climatic events (Feldpausch et al., 2016;Phillips et al., 2009). ...
Understanding of tropical forests has been revolutionized by monitoring in permanent plots. Data from global plot networks have transformed our knowledge of forests’ diversity, function, contribution to global biogeochemical cycles, and sensitivity to climate change. Monitoring has thus far been concentrated in rain forests. Despite increasing appreciation of their threatened status, biodiversity, and importance to the global carbon cycle, monitoring in tropical dry forests is still in its infancy. We provide a protocol for permanent monitoring plots in tropical dry forests. Expanding monitoring into dry biomes is critical for overcoming the linked challenges of climate change, land use change, and the biodiversity crisis. Understanding of tropical forests has been revolutionised by monitoring in permanent plots. Data from global plot networks have transformed our knowledge of forests' diversity, function, contribution to global biogeochemical cycles, and sensitivity to climate change. Monitoring has thus far been concentrated in rain forests. Despite increasing appreciation of their threatened status, biodiversity, and importance to the global carbon cycle, monitoring in tropical dry forests is still in its infancy. We provide a protocol for permanent monitoring plots in tropical dry forests. Expanding monitoring into dry biomes is critical for overcoming the linked challenges of climate change, land use change, and the biodiversity crisis.
... Whereas tropical moist forests form a closed canopy with a complex vertical structure, savannas are more open, allowing fire-and drought-adapted grasses to grow in the understory. Typically, forest dominates in wetter areas, while savannas occur in drier, seasonal areas (1,2), although transitions between forest and savanna are not rigidly determined by climate (2)(3)(4). Soils and topography can be locally and regionally important, but at intermediate rainfall (between 1,000 and 2,500 mm globally), forest and savanna, both widespread, potentially represent alternative stable states maintained by feedbacks between tree cover and disturbances-specifically fire (3,(5)(6)(7) and chronic herbivory (8). As a result, forest and savanna tree species show contrasting adaptations (9,10), and transitions across the forest-savanna boundary are characterized by high species turnover (10,11). ...
The idea that tropical forest and savanna are alternative states is crucial to how we manage these biomes and predict their future under global change. Large-scale empirical evidence for alternative stable states is limited, however, and comes mostly from the multimodal distribution of structural aspects of vegetation. These approaches have been criticized, as structure alone cannot separate out wetter savannas from drier forests for example, and there are also technical challenges to mapping vegetation structure in unbiased ways. Here, we develop an alternative approach to delimit the climatic envelope of the two biomes in Africa using tree species lists gathered for a large number of forest and savanna sites distributed across the continent. Our analyses confirm extensive climatic overlap of forest and savanna, supporting the alternative stable states hypothesis for Africa, and this result is corroborated by paleoecological evidence. Further, we find the two biomes to have highly divergent tree species compositions and to represent alternative compositional states. This allowed us to classify tree species as forest vs. savanna specialists, with some generalist species that span both biomes. In conjunction with georeferenced herbarium records, we mapped the forest and savanna distributions across Africa and quantified their environmental limits, which are primarily related to precipitation and seasonality, with a secondary contribution of fire. These results are important for the ongoing efforts to restore African ecosystems, which depend on accurate biome maps to set appropriate targets for the restored states but also provide empirical evidence for broad-scale bistability.
... The Caatinga vegetation has different physiognomies: arboreal, subarboreal, shrubby, sub-shrubby (Chaves et al., 2008) (Fig. 3). The spatial distribution of these physiognomies is related to the climate and the degree of the anthropization of the region (Silva et al., 2018a;Castro et al., 2019). The Caatinga ranges from xerophilous thorny forests -a combination of shrubs and small trees with a seasonal herbaceous layerto mosaics of semideciduous and perennial forests (Moro et al., 2014;Castanho et al., 2020). ...
Accurate information on the land cover is crucial for efficient monitoring and development of environmental studies in the Brazilian Caatinga forest. It is the largest tropical seasonal forest in South America, presenting high biodiversity and is under intense anthropogenic disturbance. Caatinga's land cover is heterogeneous, and rainfall is its primary phenological regulator, presenting mainly deciduous species. Different land-cover patterns show distinct spatial responses to climate and soils changes and modify their physical properties over time. Rainfall is highly variable over time and space, but seasonally concentrated between 2 to 4 months. Therefore, distinguishing the different patterns of land cover through medium spatial-resolution remote sensing, such as the Landsat image series, is challenging, due to the particularities of the climate-vegetation interaction. Two remote sensing approaches have a high potential for efficient land-cover mapping in Caatinga: single and multi-date imagery. The heterogeneity of the land cover of this environment can contribute to a better performance of multispectral approaches, although it is normally applied for single-date images. In a land-cover mapping effort in Caatinga, the temporal factor gains relevance, and the use of time series can bring advantages, but, in general, this approach uses vegetation index, losing multispectral information. This manuscript aims to assess the accuracies and advantages of single-date multispectral and multi-date Normalized Difference Vegetation Index (NDVI) approaches in land-cover classification. Both approaches use the Random Forest method, and the results are evaluated based on samples collected during field surveys. Results indicate that land-cover classification obtained from multi-date NDVI performs better than single-date multispectral data. The lower performance observed for single-date multispectral classification is due to similarities in spectral responses: targets of deciduous vegetation lose their foliage and can be misread as non-vegetated areas. Meanwhile, an accurate classification by time series of plant clusters in seasonal forests allows incorporating seasonal variability of land-cover classes during the rainy and dry seasons, as well as transitions between seasons.
... Sites in the NTT database are defined by a single vegetation type within a circular area of 5-km radius and contain records of tree and tree-like species, i.e., freestanding plants with stems that can reach over 3 m in height [see www.neotroptree.info and (38) for details]. Each FIA plot samples trees that are ≥12.7-cm ...
The historical course of evolutionary diversification shapes the current distribution of biodiversity, but the main forces constraining diversification are still a subject of debate. We unveil the evolutionary structure of tree species assemblages across the Americas to assess whether an inability to move or an inability to evolve is the predominant constraint in plant diversification and biogeography. We find a fundamental divide in tree lineage composition between tropical and extratropical environments, defined by the absence versus presence of freezing temperatures. Within the Neotropics, we uncover a further evolutionary split between moist and dry forests. Our results demonstrate that American tree lineages tend to retain their ancestral environmental relationships and that phylogenetic niche conservatism is the primary force structuring the distribution of tree biodiversity. Our study establishes the pervasive importance of niche conservatism to community assembly even at intercontinental scales.
... 10% of their original extent remaining (Bastin et al. 2017). While dry tropical forests have received more attention (Pennington et al. 2000;Linares-Palomino et al. 2015;Dexter et al. 2018), the knowledge of subtropical-warm temperate dry forests distribution and composition is locally fragmented or focused only on woody species instead of on complete floristic inventories (Lewis et al. 2009;Kuemmerle et al. 2017;Silva de Miranda et al. 2018). ...
Aims: The native woody vegetation from the Espinal phytogeographic province in central Argentina, found in subtropical-warm temperate climates, represents part of the southernmost seasonally dry forest in South America. Although this vegetation has been studied for over a century, a complete phytosociological survey is still needed. This lack of knowledge makes its spatial delimitation and the establishment of efficient conservation strategies particularly difficult. The main goals of this study were to classify these forests and assess their current forest cover and to better define the extent of the Espinal phytogeographic province in Córdoba region, central Argentina. Study area: Espinal Phytogeographic Province in Córdoba region, central Argentina (ca. 101,500 km² ). Methods: We sampled 122 stands following the principles of the Zürich-Montpellier School of phytosociology; relevés were classified through the ISOPAM hierarchical analysis. The extent of the Espinal phytogeographic province was established by overlaying previous vegetation maps, and a map showing the current distribution of forest patches was constructed based on a supervised classification of Landsat images. Results: Four woody vegetation types of seasonally dry subtropical forest were identified based on the fidelity and the abundance of diagnostic species: (1) Aspidosperma quebracho-blanco forest; (2) Zanthoxylum coco forest; (3) Geoffroea decorticans forest; and (4) Prosopis caldenia forest. These vegetation types were segregated along gradients of temperature and precipitation seasonality and soil-texture and sodium content. The remaining forest patches represent 3.43% of the extent of the Espinal province in Córdoba region of which only 1.05% is represented in protected areas. Conclusions: We present a classification of the Espinal forest based on a complete floristic survey. Despite the dramatic forest loss reported, our results show that some forest patches representative of the Espinal are still likely to be found in the area. However, urgent measures should be taken to establish new protected natural areas in order to preserve the last remaining forest patches.
Taxonomic reference: Catálogo de las Plantas Vasculares del Cono Sur (Zuloaga et al. 2008) and its online update (http://www.darwin.edu.ar).
Abbreviations: ISOMAP = isometric feature mapping; ISOPAM = isometric partitioning around medoids.
... These long-term tropical rain forest plots have been extremely successful in achieving their primary aim of improving our knowledge of tropical forest ecology, including, for example: the relationships of climate with biomass (Álvarez-Dávila et al., 2017) and forest structure (Feldpausch et al., 2012); the role of diversity in car- Guevara et al., 2016;Levis et al., 2017), continental scale floristic patterns (Esquivel-Muelbert et al., 2017;ter Steege et al., 2006;ter Steege, Pitman, Sabatier, Baraloto, & Salomão, 2013), biome delimitation, and mapping (Silva-de-Miranda et al., 2018), and even facilitated the discovery of species new to science (reviewed by Baker et al., 2017). Repeated censuses of these plots have provided insight into the role of tropical forests in global cycles of carbon, energy, and water (Pan et al., 2011;Phillips et al., 1998), long-term trends in forest dynamics (Brienen et al., 2015), and the impacts of extreme climatic events (Feldpausch et al., 2016;Phillips et al., 2009). ...
Understanding of tropical forests has been revolutionised by monitoring in permanent plots. Data from global plot networks have transformed our knowledge of forests’ diversity, function, contribution to global biogeochemical cycles, and sensitivity to climate change. Monitoring has thus far been concentrated in rain forests. Despite increasing appreciation of their threatened status, biodiversity, and importance to the global carbon cycle, monitoring in tropical dry forests is still in its infancy. We provide a protocol for permanent monitoring plots in tropical dry forests. Expanding monitoring into dry biomes is critical for overcoming the linked challenges of climate change, land use change, and the biodiversity crisis.
... 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). ...
Historically, biomes have been defined based on their structurally and functionally similar vegetation, but there is debate about whether these similarities are superficial, and about how biomes are defined and mapped. We propose that combined assessment of evolutionary convergence of plant functional traits and phylogenetic biome conservatism provides a useful approach for characterizing biomes. We focus on the little‐known succulent biome, a trans‐continentally distributed assemblage of succulent‐rich, drought‐deciduous, fire‐free forest, thicket and scrub vegetation as a useful exemplar biome to gain insights into these questions.
... Lett. XX (XXXX) XXXXXX Castanho et al 3 dominated by xerophilous thorn woodlandsa combination of shrubs and small trees with a seasonal herbaceous layerit also encompasses many other vegetation physiognomies whose distribution is closely related to its heterogeneous climate (Silva de Miranda et al 2018). These include mosaics of semideciduous and evergreen forests at higher elevation (residual Atlantic Rainforest), as well as cactus scrublands or rocky soil in the driest regions (Prado 2003, Sampaio and Rodal 2000, Velloso et al 2002, Moro et al 2014, Giulietti et al 2003, Rocha 2004. ...
Seasonally dry tropical forests (SDTFs) account for one-third of the interannual variability of global net primary productive (NPP). Large-scale shifts in dry tropical forest structure may thus significantly affect global CO2 fluxes in ways that are not fully accounted for in current projections. This study quantifies how changing climate might reshape one of the largest SDTFs in the world, the Caatinga region of northeast Brazil. We combine historical data and future climate projections under different representative concentration pathways (RCPs), together with spatially explicit aboveground biomass estimates to establish relationships between climate and vegetation distribution. We find that physiognomies, aboveground biomass, and climate are closely related in the Caatinga – and that the region’s bioclimatic envelope is shifting rapidly. From 2008-2017, more than 90% of the region has shifted to a dryer climate space compared to the reference period 1950-1979. An ensemble of global climate models (based on IPCC AR5) indicates that by the end of the 21st century the driest Caatinga physiognomies (thorn woodlands to non-vegetated areas) could expand from 55% to 78% (RCP 2.6) or as much as 87% (RCP8.5) of the region. Those changes would correspond to a decrease of 30% to 50% of the equilibrium aboveground biomass by the end of the century (RCP 2.6 and RCP8.5, respectively). Our results are consistent with historic vegetation shifts reported for other SDTFs. Projected changes for the Caatinga would have large-scale impacts on the region’s biomass and biodiversity, underscoring the importance of SDTFs for the global carbon budget. Understanding such changes as presented in this study will be useful for regional planning and could help mitigate their negative social impacts.
... Two other assemblages were clearly identified based on well-resolved ecological groups ( Fig. 1; Table 1), which correspond to moist tropical forest (assemblage 'B', with 15 species; Table 1) and wet tropical forest (assemblage 'C', composed of 17 species; Table 1) according to Holdridge's (1947) proposal. This pattern of separation between the Amazon and Atlantic Forests was also found by Silva de Miranda et al. (2018), who provided evidence that these forests (previously considered a single tropical wet/moist forest biome) are floristically distinct and that their climatic niches generally do not overlap. Annual precipitation and seasonality of precipitation were the most important variables restricting the species distribution of Capparaceae (69% of cases), confirming that Neotropical species of this family are climatically associated with NSDF (assemblage 'A'). ...
In the Neotropics, the distribution of Capparaceae has been historically associated with seasonally dry forest (NSDF), but recent taxonomic studies have questioned this assumption. Given the environmental co-occurrence of species and the need to understand their relationships with the ecosystem, we use ecological niche modelling and numerical ecology methods to better describe the distribution patterns of Capparaceae and their climatic affinities with NSDF. We used the Maxent algorithm to model the ecological niches of 104 species of Capparaceae, which gave maximum values of the response curves for climatic suitability. These values were used to carry out multivariate statistical analyses [principal components analysis (PCA), non-metric multidimensional scaling (NMDS) and discriminant analysis (DA)] to identify ecological associations based on climatic similitude among species. Both PCA and NMDS showed that annual precipitation, precipitation of the wettest quarter and precipitation of the driest quarter were the most important climatic variables shaping distributions of species and their associations with NSDF, moist tropical forest (MTF) and wet tropical forest (WTF). Although we found 72 species associated with NSDF as previously reported, DA revealed an overlapping pattern among the three ecological/climatic assemblages (NSDF, MTF and WTF). This confirms the existence of transition zones and species with wider niches. Our results provide an important biogeographical framework of ecological patterns for species associated with NSDF, opening new lines of research on the reconstruction of distribution in future climatic scenarios or palaeo-distributions.
... We limited our analysis to woody plants as they are the most recognizable physiognomy of the SDTFs and to those sites that fit the definition of SDTF provided by Pennington et al. (2009) andBanda et al. (2016). Thus, we excluded the Chaco woodland of central-South America characterized by frequent winter frosts (Pennington et al., 2000) and the semi-deciduous forests in Brazil bordering the Amazonian and the Atlantic rain forests where a considerable mixture of species from dry forests and wet forests are observed (Silva de Miranda et al., 2018). Nonetheless, consistent with other regional studies of the SDTF we included the semi-deciduous forests from the Misiones region (Pennington et al., 2000;Prado & Gibbs, 1993). ...
Aim
Exceptions to the quasi‐ubiquitous latitudinal diversity gradient (LDG) have been poorly studied. A reverse LDG, when species richness (SR) increases away from the Equator, has been suggested for several taxa and entire biomes. The Neotropical seasonally dry tropical forests (SDTF) are a well‐known example of a reverse LDG that could be caused by the climatic stability of Pleistocene Refugia and dispersion from distinct source areas. Here, we test these predictions under a spatial and phylogenetic framework.
Location
Neotropics.
Taxon
Woody plants.
Methods
We used a recent species‐level seed plant phylogeny and the DRYFLOR dataset to evaluate the geographic patterns of phylogenetic diversity (PD) and structure of woody plant assemblages associated with the Neotropical SDTFs. We conducted spatial regressions to test the effect of climatic instability since the Last Glacial Maximum (LGM) on assemblages’ residual PD (controlling for SR) and null model analysis to evaluate their phylogenetic structure using the Net Relatedness Index.
Results
Phylogenetic diversity of the Neotropical SDTFs increased away from the Equator, likely driven by SR. This pattern was not related to climatic instability since the LGM. Phylogenetic structure of SDTF assemblages showed considerable spatial patterning, with significant phylogenetic clustering in the Mesoamerica and Caatinga regions.
Main conclusion
The reverse latitudinal SR gradient of the Neotropical SDTF assemblages is mirrored by their PD. Phylogenetic history seems to have influenced such patterns differently across the Neotropics with no relationship to climatic stability since the LGM, where particular SDTF nuclei previously suggested as Pleistocene refugia served as cradles and source areas for the current diversity pattern of the biome.
... Vantagens e desvantagens dos sistemas de biorretenção Valoriza a paisagem urbana Pode resultar em água parada, facilitando a proliferação de pragas Reduz o pico de vazão durante eventos de chuva e diminui o nível de poluição da água Não é apropriada para lugares que geram um alto teor de poluição do solo, devido à possibilidade de contaminação dos aquíferos Recarga da água subterrânea e restabelecimento do fluxo de base Não é apropriado para lugares com declividade maior que 20% Diminui efeitos erosivos e auxilia no equilíbrio do ciclo hidrológico Requer manutenção regular e específica de acordo com o tipo de vegetação Boa aceitabilidade por parte da população Fonte: County of Los Angeles (2014); Muthanna et al. (2008); Li & Zhao (2008) apudSilva et al. (2018) ...
Livro oriundo do projeto de pesquisa entitulado IMPACTOS DAS MUDANÇAS CLIMÁTICAS EM EXTREMOS HIDROLÓGICOS (SECAS E CHEIAS), financiado pelas CAPES e Agência Nacional de Águas e Saneamento Básico por meio do Edital Mudanças do Clima e Recursos Hídricos n° 19/2015.
Instituições participantes do projeto de pesquisa
Programa de Pós-Graduação em Engenharia Civil (Recursos Hídricos) da Universidade Federal do Ceará
Programa de Pós-Graduação em Tecnologia Ambiental e Recursos Hídricos da Universidade de Brasília
Programas de Pós-Graduação em Engenharia Civil e Ambiental, em Gestão e Regulação de Recursos Hídricos, e em Sistemas Agroindustriais, da Universidade Federal de Campina Grande
Organizadores
Francisco de Assis de Souza Filho (UFC)
Carlos de Oliveira Galvão (UFCG)
Dirceu Silveira Reis Junior (UnB)
Revisores
Daniel Antônio Camelo Cid (UFC)
Maycon Breno Macena da Silva (UFCG)
Apresentação
As mudanças climáticas têm nos recursos hídricos uma de suas dimensões mais relevantes. Os impactos das mudanças climáticas nos extremos hidrológicos (secas e cheias) podem impor aumento significativo da vulnerabilidade das populações humanas e do desenvolvimento social. Avaliar os riscos de aumento da frequência destes eventos e as severidades dos mesmos é passo inicial e necessário para a proposição de estratégias de adaptação que possibilitem maior resiliência da sociedade à variabilidade e mudança climática.
Objetivando construir análise deste processo e propostas de mitigação, a Universidade Federal do Ceará (UFC), a Universidade de Brasília (UnB) e a Universidade Federal de Campina Grande (UFCG) decidiram constituir uma rede de colaboração com outras instituições internacionais e submeter proposta para o Edital Mudanças do Clima e Recursos Hídricos n° 19/2015 CAPES-ANA.
A proposta intitulada “Impactos das Mudanças Climáticas em Extremos Hidrológicos (Secas e Cheias)” recebeu financiamento deste edital e os resultados do trabalho de pesquisa financiados por este projeto constituem os capítulos do presente livro. Os grupos de pesquisa da UFCG, UFC e UnB possuem colaboração anterior a este projeto, notadamente na Rede Brasileira de Pesquisas sobre Mudanças Climáticas Globais – REDE CLIMA, e as atividades desenvolvidas neste projeto podem ser consideradas no contexto desta rede de colaboração. As pesquisas foram desenvolvidas nos Programas de Pós-Graduação em Engenharia Civil (Recursos Hídricos) da Universidade Federal do Ceará, em Tecnologia Ambiental e Recursos Hídricos da Universidade de Brasília, em Engenharia Civil e Ambiental, em Gestão e Regulaçã o de Recursos Hídricos, e em Sistemas Agroindustriais, da Universidade Federal de Campina Grande. Alunos de graduação também foram envolvidos no projeto.
Diversos pesquisadores deste projeto tiveram bolsas financiadas pelo CNPq, pela CAPES e pela Fundação Cearense de Apoio ao Desenvolvimento Científico e Tecnológico (FUNCAP), a quem agradecemos. O presente livro é dividido em três partes: (i) modelos climáticos e detecção de mudanças; (ii) impactos das mudanças climáticas e (iii) estratégias de adaptação à mudança climática.
... Two other assemblages were clearly identified based on well-resolved ecological groups ( Fig. 1; Table 1), which correspond to moist tropical forest (assemblage 'B', with 15 species; Table 1) and wet tropical forest (assemblage 'C', composed of 17 species; Table 1) according to Holdridge's (1947) proposal. This pattern of separation between the Amazon and Atlantic Forests was also found by Silva de Miranda et al. (2018), who provided evidence that these forests (previously considered a single tropical wet/moist forest biome) are floristically distinct and that their climatic niches generally do not overlap. Annual precipitation and seasonality of precipitation were the most important variables restricting the species distribution of Capparaceae (69% of cases), confirming that Neotropical species of this family are climatically associated with NSDF (assemblage 'A'). ...
In the Neotropics, the distribution of Capparaceae has been historically associated with seasonally dry forest (NSDF), but recent taxonomic studies have questioned this assumption. Given the environmental co-occurrence of species and the need to understand their relationships with the ecosystem, we use ecological niche modelling and numerical ecology methods to better describe the distribution patterns of Capparaceae and their climatic affinities with NSDF. We used the Maxent algorithm to model the ecological niches of 104 species of Capparaceae, which gave maximum values of the response curves for climatic suitability. These values were used to carry out multivariate statistical analyses [principal components analysis (PCA), non-metric multidimensional scaling (NMDS) and discriminant analysis (DA)] to identify ecological associations based on climatic similitude among species. Both PCA and NMDS showed that annual precipitation, precipitation of the wettest quarter and precipitation of the driest quarter were the most important climatic variables shaping distributions of species and their associations with NSDF, moist tropical forest (MTF) and wet tropical forest (WTF). Although we found 72 species associated with NSDF as previously reported, DA revealed an overlapping pattern among the three ecological/climatic assemblages (NSDF, MTF and WTF). This confirms the existence of transition zones and species with wider niches. Our results provide an important biogeographical framework of ecological patterns for species associated with NSDF, opening new lines of research on the reconstruction of distribution in future climatic scenarios or palaeo-distributions.
... Despite research efforts to date (e.g., De Oliveira-Filho et al. 1989, Oliveira-Filho and Ratter 1995, Neves 2017, Bueno et al. 2018, Silva de Miranda et al. 2018, it remains an open question as to how changes in soil nutrients, texture, soil water availability, and chemistry affect local forest biodiversity, structure, and physiognomy. Physiognomy is defined as "the form and function of vegetation; the appearance of vegetation that results from the life-forms of the predominant plants" (Shimwell 1984) (attributed to Cain and de Oliviera Castro 1959). ...
The severe deforestation of Brazil’s Atlantic Forest and the increasing effects of climate change underscore the need to understand how tree species respond to climate and edaphic factors. To identify the most important environmental drivers of coastal Atlantic Forest diversity and functional composition, we studied 42 plots of coastal Atlantic Forest (restinga), which has a high diversity of plant communities and spans strong environmental gradients. We examined how forest physiognomy and functional composition respond to changes in the environment, hydraulic, and soil properties. We tested different hypotheses relating the roles of nutrients and soil water availability in driving shifts in tropical forest diversity and functioning. We collected wood samples and leaves from ˜85% of the plant species identified in the forest inventory and estimated the community‐weighted tree height, aboveground biomass, basal area of individual plants, specific leaf area, wood density, and the total tree biomass per community by the sum of all trees’ aboveground biomass per plot. We measured water table depth and 24 physicochemical soil parameters. Hypotheses relating to these factors were formalized via both generalized additive models and piecewise structural equation models and null models of community assembly. Increasing drought, as reflected by increasing water table depth, coarse sand, and soil concentration of aluminum (>6 cmol/kg), was found to be a primary driver of shifts in all measured functional traits. Water table depth was found to be the main environmental driver of restinga species diversity, but shifts in species richness were largely decoupled from functional richness and functional dispersion. Our results suggest that decreases in soil water availability are a central driver of local phenotype–environment matching and that increasing water limitation increases the role of environmental filtering on multiple traits. Our results show that drought leads to a strong convergence (standardized effect size < −1.95) in forest function and leads to shifts to smaller statured forest in particular. These findings reveal important differences in the drivers of forest structure and functioning, suggesting that changes in local spatial variation in soil and moisture variables will be a central issue in restinga management and conservation.
... We produced a classification for the New World based on previous regionalization proposed by Morrone (2014). Our classification is composed of nine regions (Figure 3), and includes: two regions dominated by tropical rainforests (Amazon, Atlantic Forest); one dominated by grass-rich and fire-prone savannas (Cerrado + Pampas, which here also includes the higher elevations of the Chapada Diamantina mountain range, in the core of the Caatinga dry matrix and also the southern grasslands); the Caatinga, characterized by fire-sensitive, succulent-rich formations associated with the global SDTF biome; the Chaco, a region with great temperature seasonality that experiences regular frost, and potentially represents a distinct biome with more temperate affinities (Prado and Gibbs, 1993;Banda et al., 2016;Miranda et al., 2018); the other four regions (Andes, Caribbean Islands, North America, and Northern South America) are composed by a mix of distinct biome types. Since our aim is to assess the evolution of the dry-adapted flora, we considered Caatinga in its narrow sense (sensu Fernandes et al., 2020), including only vegetation types connected to the SDTF biome, which encompasses distinct formations that mostly occur on areas of low altitude (below 1,000 m) in the region. ...
The Brazilian Caatinga is considered the richest nucleus of the Seasonally Dry Tropical Forests (SDTF) in the Neotropics, also exhibiting high levels of endemism, but the timing of origin and the evolutionary causes of its plant diversification are still poorly understood. In this study, we integrate comprehensive sampled dated molecular phylogenies of multiple flowering plant groups and estimations of ancestral areas to elucidate the forces driving diversification and historical assembly in the Caatinga flowering plants. Our results show a pervasive floristic exchange between Caatinga and other neotropical regions, particularly those adjacent. While some Caatinga lineages arose in the Eocene/Oligocene, most dry-adapted endemic plant lineages found in region emerged from the middle to late Miocene until the Pleistocene, indicating that only during this period the Caatinga started to coalesce into a SDTF like we see today. Our findings are temporally congruent with global and regional aridification events and extensive denudation of thick layers of sediments in Northeast (NE) Brazil. We hypothesize that global aridification processes have played important role in the ancient plant assembly and long-term Caatinga SDTF biome stability, whereas climate-induced vegetation shifts, as well as the newly opened habitats have largely contributed as drivers of in situ diversification in the region. Patterns of phylogenetic relatedness of Caatinga endemic clades revealed that much modern species diversity has originated in situ and likely evolved via recent (Pliocene/Pleistocene) ecological specialization triggered by increased environmental heterogeneity and the exhumation of edaphically disparate substrates. The continuous assembly of dry-adapted flora of the Caatinga has been complex, adding to growing evidence that the origins and historical assembly of the distinct SDTF patches are idiosyncratic across the Neotropics, driven not just by continental-scale processes but also by unique features of regional-scale geological history.
... Adaptation to spatially varying selective pressures is evident in the geographical distribution of many traits in plants (e.g., Joshi et al. 2001;Sakai and Larcher 2012). Savannas and SDTFs occur under a similar seasonal climate with a dry season during the winter (Pennington et al. 2006;Silva de Miranda et al. 2018). They differ notably in soil fertility and structure; while savannas are usually found over more ancient soils, dystrophic, with lower pH, and higher concentration of aluminum, SDTFs are usually found in eutrophic and oligotrophic soils with moderate pH and low levels of aluminum (Oliveira-Filho and Ratter 1995;Dexter et al. 2018). ...
The role of natural selection in shaping spatial patterns of genetic diversity in the Neotropics is still poorly understood. Here, we perform a genome scan with 24,751 probes targeting 11,026 loci in two Neotropical Bignoniaceae tree species: Handroanthus serratifolius from the seasonally dry tropical forest (SDTF) and Tabebuia aurea from savannas, and compared with the population genomics of H. impetiginosus from SDTF. OutFLANK detected 29 loci in 20 genes with selection signal in H. serratifolius and no loci in T. aurea. Using BayPass, we found evidence of selection in 335 loci in 312 genes in H. serratifolius, 101 loci in 92 genes in T. aurea, and 448 loci in 416 genes in H. impetiginosus. All approaches evidenced several genes affecting plant response to environmental stress and primary metabolic processes. The three species shared no SNPs with selection signal, but we found SNPs affecting the same gene in pair of species. Handroanthus serratifolius showed differences in allele frequencies at SNPs with selection signal among ecosystems, mainly between Caatinga/Cerrado and Atlantic Forest, while H. impetiginosus had one allele fixed across all populations, and T. aurea had similar allele frequency distribution among ecosystems and polymorphism across populations. Taken together, our results indicate that natural selection related to environmental stress shaped the spatial pattern of genetic diversity in the three species. However, the three species have different geographical distribution and niches, which may affect tolerances and adaption, and natural selection may lead to different signatures due to the differences in adaptive landscapes in different niches.
... Recharge (green); Removal (pink); Surplus (blue); Soil Water Deficit (red). Miranda et al., 2018;CRIA, 2021). ...
The Seasonally Dry Tropical Forests (SDTF) present very high biodiversity and a number of tree species that are adapted to prolonged periods of water stress. Considering tree ring formation is mainly driven by seasonal variation in precipitation in tropical environments, tree-ring studies from STDF can provide important contributions to understanding how these forests are responding to climate variations. In the present study, we demonstrate the influence of edaphoclimatic variables (precipitation, air temperature and soil water deficit-SWD) and the ocean teleconnections (Tropical Southern Atlantic-TSA, Atlantic Multidecadal Oscillation-AMO, Western Hemisphere Warm Pool-WHWP and El Niño 3.4) on Cedrela odorata L. growth from a SDTF of northeastern Brazil. We used standard dendrochronological methods to develop an 89-year-long ring-width index chronology. The climate sensitivity of C. odorata was assessed through Pearson's correlation tests and linear regressions, which allowed to identify the determinant months (cause-effect) of each variable on the chronology. Tree growth was positively correlated with total annual precipitation and negatively correlated with temperature and SWD, particularly during the rainy season (March to August). In parallel, we identified that extremely dry years can contribute to missing rings, exposing the lack of growth in C. odorata caused by water stress. Among the oceanic variables, all of them showed a negative effect on radial growth of C. odorata, except for TSA, which had no significant effect. Tree growth is clearly disadvantaged in years with strong El Niño and high values of AMO index during the rainy months (May and June). However, the WHWP showed a more pronounced negative effect in the beginning of the dry season (September). Our findings added valuable information on C. odorata responses to hydrological seasonality from SDTF and the fluctuations in oceanic teleconnections, which in turn, influence the rainfall dynamics in northeastern Brazil.
... For instance, temperature seasonality and topography are more important indicators of species diversity than mean annual temperature (Shrestha et al., 2018). Variables related to temperature seasonality seem to be more important than variables related to mean temperature for distinguishing biomes (Silva de Miranda et al., 2018). Compared to the mean annual temperature, frost, which is correlated with temperature seasonality (Hänninen, 2016), is identified as a more important driver of tree growth (Marquis et al., 2020), and seems to better explain the altitudinal and latitudinal range limits of tree species (Du et al., 2019;Kollas et al., 2014;Körner et al., 2016;Vitra et al., 2017). ...
Plain Language Summary
The present study documents the variation with altitude of the trend in the seasonal temperature difference over the TP and detects the influence upon it of anthropogenic activities. The seasonal temperature difference weakened in most regions of the TP during 1961–2014. Also, the higher the altitude, the more notable the decrease. The trend in the temperature seasonality over the TP and its variation with altitude can mainly be ascribed to the difference in the rate of warming between winter and summer. The greater warming in winter in higher‐altitude regions over the TP causes the negative tendency of the seasonal temperature difference to amplify with elevation. The model‐simulated responses are able to capture the observed variation with altitude of the trend in the temperature seasonality only if anthropogenic forcing is involved. Moreover, the influence upon it of anthropogenic activities is statistically detectable, with the increase in anthropogenic aerosols being the main contributor. In the model‐simulated response to anthropogenic aerosol–only forcing, the larger decrease in snow‐related albedo at higher altitudes in winter can explain the amplified warming there in winter and thereby the weakening with elevation in the seasonal temperature difference.
... We structure our discussion of natural hybridization in Neotropical seed plants by major biome, including rainforest, páramo, savanna, deserts and wetlands, among others. Our justification for this is that although biomes are most usually defined by their physiognomy and ecological processes, it has been shown that in South America they can be defined by distinct species composition (Silva de Miranda et al., 2018). Such biotic distinctiveness has led some to view biomes as distinct evolutionary arenas (e.g. ...
Hybridisation can facilitate both evolutionary diversification and extinction and has had a critical role in plant evolution, with~ 25% of species known to hybridise in some temperate floras. However, in the species-rich neotropical flora, hybridisation’s role in the evolution of diversity remains unclear. Our review examines studies of hybridisation in seed plants from across the Neotropics, and explores its outcomes on neotropical plant evolution. We review studies on a per-biome basis and a spectrum of evolutionary outcomes from hybridisation are evident across neotropical biomes and taxa. These range from short-term impacts, such as the broadening of ecological amplitude in hybrid progeny with transgressive phenotypes and genetic swamping, through to long term impacts such as the generation of new lineages. Among these studies certain themes emerge, such as the pervasive hybridisation among species-rich plant radiations from the Andean Páramos, suggesting a role for hybridisation in rapid diversification events. Finally, we highlight that hybridisation is relatively understudied in the neotropical flora despite its remarkable species-richness. The advent of genomic techniques can facilitate the study of hybridisation and its effects in understudied biomes and plant groups. The increasing availability of genomic resources will eventually allow comparisons between tropical and temperate floras and therefore shed light on hybridisation’s evolutionary impacts across the latitudinal biodiversity gradient.
... Brejos in the western part of Ceará state (called Brejos Cearenses) form an area of endemism for harvestmen (DaSilva et al. 2016;DeSouza et al. 2017). Relationships among the various components of the brejos de altitude montane forests, including both Amazon region and northeastern Atlantic forest (Tabarelli & Santos 2004;Silveira et al. 2019), have been established mainly by using the inferences derived from the floristic similarity data (Santos et al. 2007;Silva-de-Miranda et al. 2018) and the population genetic structures (d' Horta et al. 2011) of these regions. The relationship between Auranus quilombola sp. ...
Harvestmen are one of the largest groups of arachnids with more than 6,500 species distributed in 1,500 genera and 50 families. However, the interactions between harvestmen and arthropod-pathogenic fungi have rarely been studied. Certain previous studies report that fungal attack represents one of the most important factors for the mortality of harvestmen, but the fungus has rarely been identified, and most of the important information about the fungus-host interactions remains unrecorded. In the present study, we have described the new species Auranus quilombola sp. nov. and reported its interactions with the arthropod-pathogenic fungus Gibellula sp. Auranus quilombola sp. nov. belongs to the family Stygnidae, and it is endemic to the humid mountain forests of Ceará state, Brazil in an area of endemism known as Brejos Cearenses. The species is related to five other species of Auranus, all of which have been recorded from the Amazon rainforest. A taxonomic description of this new species and its biogeographic implications have also been discussed in this paper.
... While it is clear that the rainforest and savanna island-like enclaves should not be included in the Caatinga delimitation (Queiroz et al., 2017;Fernandes et al., 2020), the inclusion of other areas that have transitional or ambiguous identity may be controversial Neves et al., 2015;Miranda et al., 2018) and lacks further comprehensive studies encompassing both their flora and fauna. For example, the deciduous and semideciduous seasonal forests on the western and southern edges of the Caatinga-SS are sometimes considered as part of the Caatinga (Andrade-Lima, 1981;Queiroz et al., 2017;Silva et al., 2017a;Fernandes et al., 2020) and sometimes considered as part of the Atlantic Forest (Olson et al., 2001;Silva and Casteleti, 2003;Oliveira-Filho et al., 2006), and both may be valid . ...
The Caatinga of northeastern Brazil is the largest nucleus of the seasonally dry tropical forest biome. Number of bird species in lists of the Caatinga often are quite different, mainly due to the existence of enclaves of other biomes embedded in this region, and whose species may or may not be included on those lists. While some consider such enclaves as disjunctions of other biomes, and therefore do not consider their species to be Caatinga-inhabitants, others consider the enclaves as part of the Caatinga and then include their species. In addition, the Caatinga has been widely used as a unit of analysis in biogeographical and macroecological studies, sometimes without a biologically meaningful delimitation. The need for a comprehensive review of these issues motivated me to propose a biologically meaningful checklist of the birds of the Caatinga and to explain why the enclaves of other biomes embedded within this region should not be considered part of the Caatinga. I argue that the previous checklists of birds, among other animals, of the Caatinga have been assembled in a biologically meaningless way, for which I provide a biologically meaningful alternative. This checklist comprises as many as 442 bird species for the Caatinga and is the first to comply with strict criteria as to its accessible, verifiable documentation.
... The Caatinga vegetation has different physiognomies: arboreal, subarboreal, shrubby, sub-shrubby (Chaves et al., 2008) (Fig. 3). The spatial distribution of these physiognomies is related to the climate and the degree of the anthropization of the region (Silva et al., 2018a;Castro et al., 2019). The Caatinga ranges from xerophilous thorny forests -a combination of shrubs and small trees with a seasonal herbaceous layerto mosaics of semideciduous and perennial forests (Moro et al., 2014;Castanho et al., 2020). ...
Accurate information on the land cover is crucial for efficient monitoring and development of environmental studies in the Brazilian Caatinga forest. It is one of the largest and most biodiverse dry forests on the planet. Distinguishing different patterns of land cover through medium spatial-resolution remote sensing, such as the Landsat image series, is challenging to Caatinga due to heterogeneous land cover, complex climate-soil - vegetation interactions, and anthropogenic disturbance. Two remote sensing approaches have a high potential for accurate and efficient land-cover mapping in Caatinga: single and multi-date imagery. The heterogeneity of the land cover of this environment can contribute to a better performance of multispectral approaches, although it is usually applied for single-date images. In a land-cover mapping effort in Caatinga, the temporal factor gains relevance, and the use of time series can bring advantages, but, in general, this approach uses vegetation index, losing multispectral information. This manuscript assesses the accuracies and advantages of single-date multispectral and multi-date Normalized Difference Vegetation Index (NDVI) approaches in land-cover classification. Both approaches use the Random Forest method, and the results are evaluated based on samples collected during field surveys. Results indicate that land-cover classification obtained from multi-date NDVI performs better (overall accuracy of 88.8% and kappa of 0.86) than single-date multispectral data (overall accuracy of 81.4% and kappa coefficient of 0.78). The Z-test indicated that the difference in performance between the two approaches was statistically significant. The lower performance observed for single-date multispectral classification is due to similarities in spectral responses for targets of deciduous vegetation that lose their foliage and can be misread as non-vegetated areas. Meanwhile, an accurate classification by time series of plant clusters in seasonal forests allows incorporating seasonal variability of land-cover classes during the rainy and dry seasons, as well as transitions between seasons. The most important variables that contributed to the accuracy were the red, Near Infrared (NIR) and Short-Wave Infrared (SWIR) bands in single-date multispectral classification and the months in the dry season were the most relevant in multi-date NDVI classification.
... Whereas tropical moist forests form a closed canopy with a complex vertical structure, savannas are more open, allowing fire-and drought-adapted grasses to grow in the understory. Typically, forest dominates in wetter areas, while savannas occur in drier, seasonal areas (1,2), although transitions between forest and savanna are not rigidly determined by climate (2)(3)(4). Soils and topography can be locally and regionally important, but at intermediate rainfall (between 1,000 and 2,500 mm globally), forest and savanna, both widespread, potentially represent alternative stable states maintained by feedbacks between tree cover and disturbances-specifically fire (3,(5)(6)(7) and chronic herbivory (8). As a result, forest and savanna tree species show contrasting adaptations (9,10), and transitions across the forest-savanna boundary are characterized by high species turnover (10,11). ...
The idea that tropical forest and savanna are alternative states is crucial to how we manage these biomes and predict their future under global change. Large-scale empirical evidence for alternative stable states is limited, however, and comes mostly from the multimodal distribution of structural aspects of vegetation. These approaches have been criticized, as structure alone cannot separate out wetter savannas from drier forests for example, and there are also technical challenges to mapping vegetation structure in unbiased ways. Here, we develop an alternative approach to delimit the climatic envelope of the two biomes in Africa using tree species lists gathered for a large number of forest and savanna sites distributed across the continent. Our analyses confirm extensive climatic overlap of forest and savanna, supporting the alternative stable states hypothesis for Africa, and this result is corroborated by paleoecological evidence. Further, we find the two biomes to have highly divergent tree species compositions and to represent alternative compositional states. This allowed us to classify tree species as forest vs. savanna specialists, with some generalist species that span both biomes. In conjunction with georeferenced herbarium records, we mapped the forest and savanna distributions across Africa and quantified their environmental limits, which are primarily related to precipitation and seasonality, with a secondary contribution of fire. These results are important for the ongoing efforts to restore African ecosystems, which depend on accurate biome maps to set appropriate targets for the restored states but also provide empirical evidence for broad-scale bistability. alternative stable states | tropical biomes | tree species composition | precipitation and seasonality | fire T ree cover and canopy openness are commonly used to differentiate tropical forests and savannas, but the difference between the two biomes is not just a matter of structure (1). Significance We develop a biogeographic approach to analyzing the presence of alternative stable states in tropical biomes. Whilst forest-savanna bistability has been widely hypothesized and modeled, empirical evidence has remained scarce and controversial , and here, applying our method to Africa, we provide large-scale evidence that there are alternative states in tree species composition of tropical vegetation. Furthermore, our results have produced more accurate maps of the forest and savanna distributions in Africa, which take into account differences in tree species composition, and a complex suite of determinants. This result is not only important for understanding the biogeography of the continent but also, to guide large-scaled tree planting and restoration efforts planned for the region.
... obs.). Eight out of the ten species within the South American SDTF clade are from Brazil and of these, four are distributed in the Caatinga, the largest area of SDTF in the Neotropics (700,000 km 2 ; Silva de Miranda et al. 2018). Ceiba species such as C. pubiflora are often widespread (Fig. 4) and abundant (Lima et al. 2010). ...
... Where two or more vegetation types co-occur in one 10 km diameter area, these were treated as spatially overlapping assemblages but assigned to different vegetation types (see description, history and protocol of NeoTropTree at http://www.neotr optree.info). Major heterogeneity in vegetation type within 10 km diameter areas was common in eastern South America (Silva de Miranda et al., 2018). In addition to the presence and absence data for tree species, each assemblage is characterized by numerous descriptive and environmental data, such as altitude, geo-edaphic and climatic variables. ...
Abstract
Aim
We used a phylogenetic approach to group assemblages of woody plant into major vegetation units in the Atlantic Forest, thus for the first time incorporating information on species evolutionary relationships into a bioregionalization of this critical hotspot. A phylogenetic regionalization will provide a spatially explicit framework for answering many basic and applied questions in biogeography, ecology and conservation.
Location
Atlantic Forest.
Taxon
Angiosperms
Methods
Our data set comprises 614 genera and 116 families, spread over 1,755 assemblages. To place assemblages in a multivariate evolutionary composition space, we used a phylogenetically informed ordination analysis, and to determine what the main phylogenetic groups of assemblages were, we used K‐means clustering based on phylogenetic dissimilarity of assemblages. To quantify how well environmental variables distinguish the phylogenetic groups found, we implemented classification tree approaches. Then, to explore the evolutionary turnover between the phylogenetic groups, we calculated phylogenetic beta diversity. Finally, we determined the lineages that are most strongly associated with individual phylogenetic groups using an indicator analysis for lineages.
Results
Our analyses suggest that there are seven principal groups, in terms of evolutionary lineage composition, in the Atlantic Forest. The greatest turnover of phylogenetic lineage composition separates tropical evergreen rain forest and semideciduous assemblages from subtropical and highland assemblages. The mixed subtropical forest showed the lowest phylogenetic compositional similarity values with other groups. Tropical rain forest had the highest number of significant indicator lineages, and the highest values of the indicator statistic for lineages.
Main conclusions
We found that the most pronounced evolutionary division separates southern and highland tree assemblages from those occurring under more tropical climates and at lower elevations. Our phylogenetic analyses point to an environmentally driven compositional division, likely based on the regular occurrence of freezing versus non‐freezing temperatures. Precipitation and edaphic regimes that assemblages experience had less definitive effects on their evolutionary lineage composition.
Texture, base saturation, organic carbon content, and water storage availability of soil are drivers of plant physiognomy and composition of communities. Soil properties in ecotone areas are still poorly studied, and the transition between dry, moist, and semideciduous forests is defined only by climate parameters. The objective of this study was to describe the soil properties of a moist-dry forest ecotone in Northeastern Brazil. Seven soil profiles were dug in a pristine semideciduous forest known as “Agreste”. Four more pedons were described to represent soils of dry forests. Morphology, reactivity, texture, organic matter content, and water storage capacity of the soil horizons were determined. The soils of the study area are derived from granites and granitoids, rocks highly resistant to weathering. Soils of dry forests are loam, neutral to alkaline, and hypereutrophic. Soils of semideciduous forest are sandy, acidic, dystrophic, and have up to 65% higher C content. The rocks act as impermeable layers to water, and consequently, most soils develop stagnic properties in semideciduous forests. Soils are dystrophy and have low CEC and loam texture. These properties are attributed to ferrolysis. Umbrisols and Stagnosols with higher water storage capacity than dry forests soils sustain semideciduous forests in Northeastern Brazil.
Tropical ecosystems have the highest levels of biodiversity, cycle more water and absorb more carbon than any other terrestrial ecosystem on Earth. Consequently, these ecosystems are extremely important components of Earth’s climatic system and biogeochemical cycles. Plant hydraulics is an essential discipline to understand and predict the dynamics of tropical vegetation in scenarios of changing water availability. Using published plant hydraulic data we show that the trade‐off between drought avoidance (expressed as deep‐rooting, deciduousness and capacitance) and hydraulic safety (P50) is a major axis of physiological variation across tropical ecosystems. We also propose a novel and independent axis of hydraulic trait variation linking vulnerability to hydraulic failure (expressed as the hydraulic safety margin‐HSM) and growth, where inherent fast‐growing plants have lower HSM compared to slow‐growing plants. We surmise that soil nutrients are fundamental drivers of tropical community assembly determining the distribution and abundance of the slow‐safe/fast‐risky strategies. We conclude showing that including either the growth‐HSM or the resistance‐avoidance trade‐off in models can make simulated tropical rainforest communities substantially more vulnerable to drought than similar communities without the trade‐off. These results suggest that vegetation models need to represent hydraulic trade‐off axes to accurately project the functioning and distribution of tropical ecosystems.
The Science Panel for the Amazon (SPA) is an unprecedented initiative convened under the auspices of the United Nations Sustainable Development Solutions Network (SDSN). The SPA is composed of over 200 preeminent scientists and researchers from the eight Amazonian countries, French Guiana, and global partners. These experts came together to debate, analyze, and assemble the accumulated knowledge of the scientific
community, Indigenous peoples, and other stakeholders that live and work in the Amazon.
The Panel is inspired by the Leticia Pact for the Amazon. This is a first-of-its-kind Report which provides a comprehensive, objective, open, transparent, systematic, and rigorous scientific assessment of the state of the Amazon’s ecosystems, current trends, and their implications for the long-term well-being of the region, as well as opportunities and policy
relevant options for conservation and sustainable development.
The three volumes of the final report can be downloaded from: https://www.theamazonwewant.org/amazon-assessment-report-2021/
This chapter presents country-specific descriptions of human intervention in the Amazon. In general, a rapid expansion of agricultural and extractive activities, mostly for export but also for domestic markets, and to a lesser degree small scale agriculture, have led to extensive deforestation and environmental degradation without substantially improving the living conditions of the population. Government policies and the extent of State ascendancy in the area also seem to be a powerful determinant of the nature and scale of the process. Despite the common underlying international and domestic economic and political forces in the Amazon, each country has its own particularities. In the case of Colombia, the process was shaped by the guerilla presence and deteriorated after the Peace Treaty, which does not mention “deforestation” and perpetuates Colombia’s extractivist model. Ecuador’s case is representative of the link between fossil fuel extraction, environmental deterioration, and social exclusion. The case of Peru shows an Amazon perceived as a territory awaiting to be “conquered, occupied, and exploited”, subjected to an unwavering extractive and market-orientated drive. In Bolivia, contradictions between conservation and state-led development policies and business activities, which have transformed it into the second deforestation hotspot of Amazonia after Brazil, are presented. The Venezuelan Amazon is subject to rampant violence and illegal activity driven by the political geography of gold in mixed configurations of governance, with blurred boundaries between legality and illegality and prevailing negligence concerning conservation. The Guianas share low deforestation levels and lower environmental pressures, but the recent expansion of gold mining poses a serious threat. The Brazilian case presented in the previous Chapter is referenced here when comparing countries’ experienes. Conservation experiences are also included. In all cases, unsustainable extractivist models have outpaced conservation policies; however, these experiences can prove useful in the design of effective conservation policies, reduction of greenhouse gas emissions, and improvements in living conditions of Indigenous peoples and local communities.
This work is focused on characterizing and understanding the aboveground biomass of Caatinga in a semiarid region in northeastern Brazil. The quantification of Caatinga biomass is limited by the small number of field plots, which are inadequate for addressing the biome’s extreme heterogeneity. Satellite-derived biomass products can address spatial and temporal changes but they have not been validated for seasonally dry tropical forests. Here we combine a compilation of published field phytosociological observations with a new 30m spatial resolution satellite biomass product. Both data were significantly correlated, satellite estimates consistently captured the wide variability of the biomass across the different physiognomies (2-272 Mg/ha). Based on the satellite product we show that in year 2000 about 50 percent of the region had very low biomass (<2 Mg/ha) and that the majority of the biomass (86%) is concentrated in only 27% of the area. Our work confirm other estimates of biomass 39 Mg/ha (9-61 Mg/ha) and carbon 0.79 PgC. The satellite products together with ground based estimates has the potential to improve forest management in Caatinga and other seasonally dry tropical forests through improved approximation of spatial variability, how they relate to climate, and support numerical modeling experiments in semiarid regions.
The miombo woodlands form the largest dry forest ecosystem both worldwide and in southern Africa. They have existed since the Tertiary Period following major climatic and topographic changes which shrank the closed evergreen forests. We describe miombo distribution according to the ecological importance of Brachystegia and Julbernardia, the two main genera, and according to the abundance of the main plant species. Analyses indicate that the woodlands cover nearly 2 million km2. The ecology of the woodlands is driven by climate, soils and disturbances, but given the extent of woodland cover change, the variability in structure and composition across the region is enormous and not always directly related to the determinants. This landscape variability is important for miombo conservation and management. Continued active research is essential to increase knowledge in the current global changing context.
The evolutionary processes leading to lineage diversification in Neotropical plants are still poorly understood. Here, we provide a synthesis of phylogeographic patterns and unravel whether the Neogene geological events or the Quaternary climatic changes drove lineage diversification of Angiosperms in the South America dry diagonal. Despite the high number of plant species in the dry diagonal (~19,000) only few species (30) were studied. Major lineage divergences occurred in the Pliocene but most lineage diversifications occurred at the Early and Middle Pleistocene. The Last Glacial Maximum (LGM) may have had a more local and regional effect in differentiation among populations and patterns of genetic diversity distribution. Species responded differently to the Quaternary climate changes leading to high variation in spatial patterns in genetic diversity and phylogeographic patterns. Finally, our findings challenge the hypothesis of glacial refugia and the importance of the last glacial maximum (LGM) in the diversification of Angiosperms in the South America dry diagonal.
Aim
To quantify evolutionary transitions between tropical evergreen rain forest and seasonally dry biomes, to test whether biome transitions affect lineage diversification and to examine the robustness of these results to methodological choices.
Location
The tropics.
Time period
The Cenozoic.
Major taxa studied
The plant subfamily Bombacoideae (Malvaceae).
Methods
We inferred ancestral biomes based on a fossil‐dated molecular phylogeny of 103 species (59% of the clade) and recorded the number of transitions among biomes using biogeographical stochastic mapping based on the dispersal‐extinction‐cladogenesis model. We then estimated diversification rates using state‐specific speciation and extinction rate (SSE) methods. Furthermore, we tested the sensitivity of the results to model choice, phylogenetic uncertainty, measurement error and biome definition.
Results
We found numerous transitions from evergreen rain forest to seasonally dry biomes, and fewer in the opposite direction. These results were robust to methodological choices. Biome type did not influence diversification rates, although this result was subject to uncertainty, especially related to model choice and biome definition.
Main conclusions
Our results contradict the idea of evolutionary biome conservatism in Bombacoideae, and support previous findings that evergreen rain forests serve as a source for the flora of seasonally dry biomes. The impact of biome classification and biome definition on the results suggest caution when using a biome concept for biogeographical reconstruction and diversification rate analysis.
The National Forest Inventory (Inventário Florestal Nacional-IFN) is a large initiative that uses standardised methods to survey Brazilian forestry resources. One target of the IFN is the Cerrado, which contains one of the richest floras in the world. The aim of this study was to assess the contribution of the IFN to the knowledge of Cerrado woody flora. We analysed data from field-collected vouchers sampled by the IFN Cerrado. We restricted our analyses to IFN collections of native trees and shrubs, including palms, which were identified at the species level. Habitat of each collection was obtained by overlaying specimens’ geographic coordinates with land cover maps available in the Mapbiomas platform. Our final dataset comprised 28,602 specimens distributed in 2,779 sites (conglomerates) in Bahia, Distrito Federal, Goiás, Maranhão, Mato Grosso, Mato Grosso do Sul, Minas Gerais, Piauí, São Paulo and Tocantins. Collections were located in the following habitats: savannas (40.5%), forests (30.2%), anthropic areas (25.6%), grasslands (3.5%), and water (0.2%). We recorded 1,822 species belonging to 543 genera and 105 families, representing 34% of Cerrado woody species recorded on Flora do Brasil 2020. Fabaceae had the largest number of species, while Tapirira guianensis and Matayba guianensis were the most collected species. We highlight 60 potentially new records of occurrence for several states and 64 new records for the Cerrado, primarily in riparian forests where species from other biomes occur. In addition, 232 recorded species are Cerrado endemics, while 36 are cited in the CNCFlora’s red list as endangered. The systematic sampling carried out by the IFN enabled vegetation sampling in remote and poorly known areas, which expanded the geographic range of many woody species and contributed to the knowledge of plant diversity in the Cerrado.
This Report provides a comprehensive, objective, open, transparent, systematic, and rigorous scientific assessment of the state of the Amazon’s ecosystems, current trends, and their implications for the long-term well-being of the region, as well as opportunities and policy relevant options for conservation and sustainable development.
Climate change has the potential to affect the ecology and evolution of every species on Earth. Although the ecological consequences of climate change are increasingly well documented, the effects of climate on the key evolutionary process driving adaptation - natural selection - are largely unknown. We report that aspects of precipitation and potential evapotranspiration, along with the North Atlantic Oscillation, predicted variation in selection across plant and animal populations throughout many terrestrial biomes, whereas temperature explained little variation. By showing that selection was influenced by climate variation, our results indicate that climate change may cause widespread alterations in selection regimes, potentially shifting evolutionary trajectories at a global scale.
We assess progress toward the protection of 50% of the terrestrial biosphere to address the species-extinction crisis and conserve a global ecological heritage for future generations. Using a map of Earth's 846 terrestrial ecoregions, we show that 98 ecoregions (12%) exceed Half Protected; 313 ecoregions (37%) fall short of Half Protected but have sufficient unaltered habitat remaining to reach the target; and 207 ecoregions (24%) are in peril, where an average of only 4% of natural habitat remains. We propose a Global Deal for Nature—a companion to the Paris Climate Deal—to promote increased habitat protection and restoration, national-and ecoregion-scale conservation strategies, and the empowerment of indigenous peoples to protect their sovereign lands. The goal of such an accord would be to protect half the terrestrial realm by 2050 to halt the extinction crisis while sustaining human livelihoods.
Climate change will fundamentally alter many aspects of the natural world. To understand how species may adapt to this change, we must understand which aspects of the changing climate exert the most powerful selective forces. Siepielski et al. looked at studies of selection across species and regions and found that, across biomes, the strongest sources of selection were precipitation and transpiration changes. Importantly, local and regional climate change explained patterns of selection much more than did global change.Science, this issue p. 959Climate change has the potential to affect the ecology and evolution of every species on Earth. Although the ecological consequences of climate change are increasingly well documented, the effects of climate on the key evolutionary process driving adaptationtextemdashnatural selectiontextemdashare largely unknown. We report that aspects of precipitation and potential evapotranspiration, along with the North Atlantic Oscillation, predicted variation in selection across plant and animal populations throughout many terrestrial biomes, whereas temperature explained little variation. By showing that selection was influenced by climate variation, our results indicate that climate change may cause widespread alterations in selection regimes, potentially shifting evolutionary trajectories at a global scale.
This paper describes the technical development and accuracy assessment of the most recent and improved version of the SoilGrids system at 250m resolution (June 2016 update). SoilGrids provides global predictions for standard numeric soil properties (organic carbon, bulk density, Cation Exchange Capacity (CEC), pH, soil texture fractions and coarse fragments) at seven standard depths (0, 5, 15, 30, 60, 100 and 200 cm), in addition to predictions of depth to bedrock and distribution of soil classes based on the World Reference Base (WRB) and USDA classification systems (ca. 280 raster layers in total).
ABSTRACT
The tree flora of seasonally dry forests (SDTF) of eastern tropical and subtropical South America was investigated according to two main aspects: (a) the variations in floristic composition were analyzed in terms of geographical and climatic variables by performing multivariate analyses on 532 existing floristic checklists; and (b) the links among different seasonally dry forest formations, Amazonian forests and cerrados (woody savannas) were assessed. Analyses were performed at the species, genus and family levels. There was a strong spatial pattern in tree species distribution that only receded and allowed clearer climate-related patterns to arise when either the geographical range was restricted or data were treated at the genus and family levels. Consistent floristic differences occurred between rain and seasonal forests, although these were obscured by Strong regional similarities which made the two foresttypes from the same region closer to each other floristically than they were to their equivalents in different regions. Atlantic rain and seasonal forests were floristically closer to each other than to Amazonian rain forests but north-east rain and seasonal forests were both closer to Amazonian rain forests than each other, though only at the generic and familial levels. Atlantic seasonal forests also share a variable proportion of species with caatingas, cerrados and the chaco, and may represent a transition to these open formations. Increasing periods of water shortage, with increases in soil fertility and temperature are characteristic of a transition from semideciduous to deciduous forests and then to the semi-arid formations, either caatingas (tropical) or chaco forests (subtropical), while increasing fire frequency and decreasing soil fertility lead from seasonal forests to either cerrados (tropical) or southern campos (subtropical). The SDTF vegetation of eastern South America may be classified into three floristic nuclei: caatinga, chaco and Atlantic forest (sensu latissimo). Only the last, however, should be linked consistently to the residual Pleistocenic dry seasonal flora (RPDS). Caatinga and chaco represent the extremes of floristic dissimilarity among the three nuclei, also corresponding to the warm-dry and warm-cool climatic extremes, respectively. In contrast to the caatinga and chaco nuclei, the Atlantic SDTF nucleus is poor in endemic species and is actually a floristic bridge connecting the two drier nuclei to rain forests. Additionally, there are few grounds to recognize the Atlantic nucleus flora as a clearly distinct species assemblage, since there is a striking variation in species composition found throughout its wide geographical range. Nevertheless, there is a group of wide-range species that are found in most regions of the Atlantic nucleus, some of which are also part of the species blend of the Caatinga and Chaco floras, though the latter plays a much smaller part. We propose that it is precisely this small fraction of the Atlantic nucleus flora that should be identified with the RPDS vegetation.
The subtropical dry forests are experiencing rapid clearing in the southamerican Great Chaco region, mainly for soybean production in Argentina. This is causing biodiversity loss and soil salinization. This forests are unique for the floristic richness and the dense forest cover in a region characterized by semiarid climatic conditions. The authors complain to the DRYFLOR team for their exclusion of the Gran Chaco, the world´s largest continuous dry forest, from their definition of tropical and subtropical dry forests in their paper "Plant diversity patterns in neotropical dry forests and their conservation implications".
Seasonally dry tropical forests are distributed across Latin America and the Caribbean and are highly threatened, with less than 10% of their original extent remaining in many countries. Using 835 inventories covering 4660 species of woody plants, we show marked floristic turnover among inventories and regions, which may be higher than in other neotropical biomes, such as savanna. Such high floristic turnover indicates that numerous conservation areas across many countries will be needed to protect the full diversity of tropical dry forests. Our results provide a scientific framework within which national decision-makers can contextualize the floristic significance of their dry forest at a regional and continental scale.
Wildfires are becoming increasingly dominant in tropical landscapes due to reinforcing feedbacks between land cover change and more severe dry conditions. This study focused on the Bolivian Chiquitania, a region located at the southern edge of Amazonia. The extensive, unique and well-conserved tropical dry forest in this region is susceptible to wildfires due to a marked seasonality. We used a novel approach to assess fire risk at the regional level driven by different development trajectories interacting with changing climatic conditions. Possible future risk scenarios were simulated using maximum entropy modelling with presence-only data, combining land cover, anthropogenic and climatic variables. We found that important determinants of fire risk in the region are distance to roads, recent deforestation and density of human settlements. Severely dry conditions alone increased the area of high fire risk by 69%, affecting all categories of land use and land cover. Interactions between extreme dry conditions and rapid frontier expansion further increased fire risk, resulting in potential biomass loss of 2.44±0.8 Tg in high risk area, about 1.8 times higher than the estimates for the 2010 drought. These interactions showed particularly high fire risk in land used for 'extensive cattle ranching', 'agro-silvopastoral use' and 'intensive cattle ranching and agriculture'. These findings have serious implications for subsistence activities and the economy in the Chiquitania, which greatly depend on the forestry, agriculture and livestock sectors. Results are particularly concerning if considering the current development policies promoting frontier expansion. Departmental protected areas inhibited wildfires when strategically established in areas of high risk, even under drought conditions. However, further research is needed to assess their effectiveness accounting for more specific contextual factors. This novel and simple modelling approach can inform fire and land management decisions in the Chiquitania and other tropical forest landscapes to better anticipate and manage large wildfires in the future.
High-temperature tolerance in plants is important in a warming world, with extreme heat-waves predicted to increase in frequency and duration, potentially leading to lethal heating of leaves. Global patterns of high-temperature tolerance are documented in animals, but generally not plants, limiting our ability to assess risks associated with climate warming. To assess whether there are global patterns in high-temperature tolerance of leaf metabolism, we quantified Tcrit (high temperature where minimal chlorophyll a fluorescence rises rapidly, and thus where photosystem II is disrupted) and Tmax (temperature where leaf respiration in darkness is maximal, beyond which respiratory function rapidly declines) in upper-canopy leaves of 218 plant species spanning seven biomes. Mean site-based Tcrit values ranged from 41.5 °C in the Alaskan arctic to 50.8 °C in lowland tropical rainforests of Peruvian Amazon. For Tmax, the equivalent values were 51.0 and 60.6 °C in the Arctic and Amazon, respectively. Tcrit and Tmax followed similar biogeographic patterns, increasing linearly (˜8 °C) from polar to equatorial regions. Such increases in high temperature tolerance are much less than expected based on the 20 °C span in high temperature extremes across the globe. Moreover, with only modest high-temperature tolerance despite high summer temperature extremes, species in mid-latitude (~20°-50°) regions have the narrowest thermal safety margins in upper-canopy leaves; these regions are at the greatest risk of damage due to extreme heat-wave events, especially under conditions when leaf temperatures are further elevated by a lack of transpirational cooling. Using predicted heat-wave events for 2050 and accounting for possible thermal acclimation of Tcrit and Tmax, we also found that these safety margins could shrink in a warmer world, as rising temperatures are likely to exceed thermal tolerance limits. Thus, increasing numbers of species in many biomes may be at risk as heat-wave events become more severe with climate change. This article is protected by copyright. All rights reserved.
We used Ecological Niche Modeling (ENM) of individual species of two taxonomic groups (plants and birds) in order to reconstruct the climatic distribution of Tropical Dry Forests (TDFs) in Mexico and to analyze their boundaries with other terrestrial ecosystems. The reconstruction for TDFs’ distribution was analyzed considering the prediction and omission errors based upon the combination of species, obtained from the overlap of individual models (only plants, only birds, and all species combined). Two verifications were used: a primary vegetation map and 100 independent TDFs localities. We performed a Principal Component (PCA) and Discriminant Analysis (DA) to evaluate the variation in the environmental variables and ecological overlap among ecosystems. The modeling strategies showed differences in the ecological patterns and prediction areas, where the “all species combined” model (with a threshold of ≥10 species) was the best strategy to use in the TDFs reconstruction. We observed a concordance of 78% with the primary vegetation map and a prediction of 98% of independent locality records. Although PCA and DA tests explained 75.78% and 97.9% of variance observed, respectively, we observed an important overlap among the TDFs with other adjacent ecosystems, confirming the existence of transition zones among them. We successfully modeled the distribution of Mexican TDFs using a number of bioclimatic variables and co-distributed species. This autoecological niche approach suggests the necessity of rethinking the delimitations of ecosystems based on the recognition of transition zones among them in order to understand the real nature of communities and association patterns of species.
The checklist of the vascular plants of the Southern Cone presents updated information of 19,787 taxa and 44,943 synonyms, distributed in 2,679 genera and 318 families. This checklist was prepared, and its permanently updated, using the database "Documenta Florae Australis", with the contribution of numerous researchers and institutions, and constitutes the bases for the Flora of Argentina, currently under preparation. Here we evaluate the current knowledge of vascular plants in the Southern Cone and provide a summary of the ongoing Flora of Argentina, and the significance of these projects for the World Flora on line and to the botanical studies in the region.
Earth is home to a remarkable diversity of plant forms and life histories, yet comparatively few essential trait combinations have proved evolutionarily viable in today’s terrestrial biosphere. By analysing worldwide variation in six major traits critical to growth, survival and reproduction within the largest sample of vascular plant species ever compiled, we found that occupancy of six-dimensional trait space is strongly concentrated, indicating coordination and trade-offs. Three-quarters of trait variation is captured in a two-dimensional global spectrum of plant form and function. One major dimension within this plane reflects the size of whole plants and their parts; the other represents the leaf economics spectrum, which balances leaf construction costs against growth potential. The global plant trait spectrum provides a backdrop for elucidating constraints on evolution, for functionally qualifying species and ecosystems, and for improving models that predict future vegetation based on continuous variation in plant form and function.
Assuming that co-distributed species are exposed to similar environmental conditions, ecological niche models (ENMs) of bird and plant species inhabiting tropical dry forests (TDFs) in Mexico were developed to evaluate future projections of their distribution for the years 2050 and 2070. We used ENM-based predictions and climatic data for two Global Climate Models, considering two Representative Concentration Pathway scenarios (RCP4.5/RCP8.5). We also evaluated the effects of habitat loss and the importance of the Mexican system of protected areas (PAs) on the projected models for a more detailed prediction of TDFs and to identify hot spots that require conservation actions. We identified four major distributional areas: the main one located along the Pacific Coast (from Sonora to Chiapas, including the Cape and Bajío regions, and the Balsas river basin), and three isolated areas: the Yucatán peninsula, central Veracruz, and southern Tamaulipas. When considering the effect of habitat loss, a significant reduction (~61%) of the TDFs predicted area occurred, whereas climate-change models suggested (in comparison with the present distribution model) an increase in area of 3.0-10.0% and 3.0-9.0% for 2050 and 2070, respectively. In future scenarios, TDFs will occupy areas above its current average elevational distribution that are outside of its present geographical range. Our findings show that TDFs may persist in Mexican territory until the middle of the XXI century; however, the challenges about long-term conservation are partially addressed (only 7% unaffected within the Mexican network of PAs) with the current Mexican PAs network. Based on our ENM approach, we suggest that a combination of models of species inhabiting present TDFs and taking into account change scenarios represent an invaluable tool to create new PAs and ecological corridors, as a response to the increasing levels of habitat destruction and the effects of climate change on this ecosystem.
To provide an inter-continental overview of the floristics and biogeography of drought-adapted tropical vegetation formations, we compiled a dataset of inventory plots in South America (n=93), Africa (n=84), and Asia (n=92) from savannas (subject to fire), seasonally dry tropical forests (not generally subject to fire), and moist forests (no fire). We analysed floristic similarity across vegetation formations within and between continents. Our dataset strongly suggests that different formations tend to be strongly clustered floristically by continent, and that among continents, superficially similar vegetation formations (e.g. savannas) are floristically highly dissimilar. Neotropical moist forest, savanna and seasonally dry tropical forest are floristically distinct, but elsewhere there is no clear floristic division of savanna and seasonally dry tropical forest, though moist and dry formations are separate. We suggest that because of their propensity to burn, many formations termed “dry forest” in Africa and Asia are best considered as savannas. The floristic differentiation of similar vegetation formations from different continents suggests that cross-continental generalisations of the ecology, biology and conservation of savannas and seasonally dry tropical forests may be difficult.
The main objective of our study was to provide consistent information on land cover changes between the years 1990 and 2010 for the Cerrado and Caatinga Brazilian seasonal biomes. These areas have been overlooked in terms of land cover change assessment if compared with efforts in monitoring the Amazon rain forest. For each of the target years (1990, 2000 and 2010) land cover information was obtained through an object-based classification approach for 243 sample units (10 km × 10 km size), using (E)TM Landsat images systematically located at each full degree confluence of latitude and longitude. The images were automatically pre-processed, segmented and labelled according to the following legend: Tree Cover (TC), Tree Cover Mosaic (TCM), Other Wooded Land (OWL), Other Land Cover (OLC) and Water (W). Our results indicate the Cerrado and Caatinga biomes lost (gross loss) respectively 265,595 km2 and 89,656 km2 of natural vegetation (TC + OWL) between 1990 and 2010. In the same period, these areas also experienced gain of TC and OWL. By 2010, the percentage of natural vegetation cover remaining in the Cerrado was 47% and in the Caatinga 63%. The annual (net) rate of natural vegetation cover loss in the Cerrado slowed down from −0.79% yr−1 to −0.44% yr−1 from the 1990s to the 2000s, while in the Caatinga for the same periods the rate increased from −0.19% yr−1 to −0.44% yr−1. In summary, these Brazilian biomes experienced both loss and gains of Tree Cover and Other Wooded Land; however a continued net loss of natural vegetation was observed for both biomes between 1990 and 2010. The average annual rate of change in this period was higher in the Cerrado (−0.6% yr−1) than in the Caatinga (−0.3% yr−1).
R package, available on CRAN