Tropical Forests Of South America Research Articles

Climate change is expected to reduce the potential distribution of Ceiba glaziovii in Caatinga, the largest area of dry tropical forest in South America

Ecological niche modeling is a widely used tool to predict species distribution considering current, past, or future climate change scenarios across different geographic areas. Modeling scenarios allow researchers to assess the impacts of climate change on species distribution and identify priority areas for conservation. This study aimed to model the current and future potential distribution of Ceiba glaziovii under different climate change scenarios in Brazil. The MaxEnt algorithm was used to correlate species occurrence points with bioclimatic variables in current and future climate scenarios. Four General Circulation Models (GCMs) from CMIP6 were employed: BCC-CSM2-MR, CNRM-CM6-1, IPSL-CM6A-LR, and MIROC6, considering optimistic and pessimistic projections. The contribution of variables and model accuracy were assessed using the Jackknife statistical test and the Area Under the Curve (AUC) parameter. AUC values for current and future scenarios demonstrated high accuracy. The bioclimatic variables of precipitation and temperature were the main contributors to determining areas with higher habitat suitability. In the future climate scenario, there was a reduction in areas with good climatic suitability for all four GCMs, considering optimistic and pessimistic projections. Among the areas with high habitat suitability, the IPSL-CM6A-1 model in the optimistic projection showed the smallest reduction, while in the pessimistic scenario, all areas with high suitability disappeared. The species' climatic niche is expected to decrease under all tested climate change scenarios. The central areas of the Caatinga and its transition zones exhibit the highest climatic suitability in current and future scenarios and should be prioritized for the species' conservation.

Decoding the drivers and effects of deforestation in Peru: a national and regional analysis

AbstractHigh deforestation rates in tropical forests of South America lead to biodiversity loss, climate change and alterations in nature’s contributions to people. Deforestation drivers vary across scales due to the heterogeneity of environmental and socioeconomic conditions and forest types. Here, we test the effects of deforestation drivers on deforestation rate from 2000 to 2020 at national and regional scales using Peru as a study case. To do that, we selected nine deforestation drivers commonly used in tropical deforestation analyses. We used the forest cover loss dataset of Global Forest Change to calculate deforestation rates. We conducted five path analyses, one for the national scale and the others for the four regions, using the district as a spatial unit. The national path model explained 34% of the total observed variance and showed that temperature, agriculture, transport network, precipitation, rural population and fire had a positive effect on deforestation, while the slope had a negative effect. The regional path models (63% of the total observed variance in the Coast region, 32% in the Andean, 60% in the High Rainforest and 75% in the Low Rainforest) showed that many national drivers remained at the regional scale. However, we found that the strength, relation (positive/negative) and type (direct/indirect) may vary. Therefore, identifying regional differences in deforestation dynamics is crucial for forest conservation planning and for addressing effective policies in tropical countries. However, improving the quality and availability of national data is essential for further advancing our understanding of this complex process.

Cues of uncommon food habits within dung beetles: Notes from a seasonally dry tropical forest in South America

The assessment of species’ diet and trophic plasticity serve as key elements to understand their adaptations to harsh ecosystems, such as deserts and dry forests. Among dung beetles, coprophagy is the main feeding habit, which may be substituted or complemented by other unusual diets, such as granivory and necrophagy. This study presents new records of dung beetle uncommon diets in Caatinga, the largest Seasonally Dry Tropical Forest in America. We include novel descriptions of the genera Dichotomius Hope, 1838 and Canthidium Erichson, 1847 in using and removing seeds in Caatinga. We also present the first report of dung beetles from Caatinga attracted to dead millipedes, specifically for Coprophanaeus pertyi (Olsufieff, 1924). Also, we found goat hairballs along with the roller beetle Deltochilum verruciferum Felsche, 1911 inside a pitfall trap, suggesting that this species may use animal fur to feed or breed. Finally, we included an updated list on unusual food records of dung beetle species in Caatinga dry forest. Our findings indicate that dung beetles in Caatinga display diverse feeding habits in response to extreme environmental conditions and/or limited resources. We expand the still-scarce knowledge regarding dung beetle feeding ecology outside their interaction with dung or the soft tissues of carrion. Despite our findings, new evidence is essential to reinforce our understanding on trophic plasticity of dung beetles in Caatinga. A better comprehension of resource plasticity by dung beetles will also be a significant input for biodiversity conservation due to the changes in food availability in anthropogenic landscapes.

Mapping the Amazon: Literary Geography After the Rubber Boom by Amanda M. Smith

Reviewed by: Mapping the Amazon: Literary Geography After the Rubber Boom by Amanda M. Smith Charlotte Rogers KEYWORDS Amazonia, Cartography, Maps, Environmental Humanities, Literature, Literary Criticism, Latin America amanda m. smith. Mapping the Amazon: Literary Geography After the Rubber Boom. Liverpool UP, 2021, 248 pp. The drama of getting lost in the jungle has long been a driving force of fiction about the South American wilderness. While "losing oneself" is often glossed as a psychological and even existential crisis in literary studies, Amanda M. Smith's Mapping the Amazon: Literary Geography After the Rubber Boom approaches the phenomenon from a more prosaically literal yet equally enriching perspective. Mapping the Amazon examines five canonical novels set in the tropical forests of South America by José Eustasio Rivera, Rómulo Gallegos, Mario Vargas Llosa, César Calvo, and Márcio Souza. Smith proposes that each author creates a literary geography that signals the insufficiency of traditional cartography to represent Amazonia while simultaneously presenting an imagined landscape that has real consequences for the region's ecologies, peoples, and cultures. This important contribution to Amazonian literary studies deftly builds a theoretical bridge between geocriticism and the environmental humanities. Smith incisively identifies a tension central to her corpus of texts, namely the gulf between what Gallegos called the "geografía muerta" of cartography and the [End Page 115] "geografía viva" of the forest (68). One episode from Rivera's La vorágine perfectly crystallizes this dichotomy: the coyly named character Clemente Silva gets lost attempting to navigate the forest according to existing maps of Amazonia, only to later save himself through an attentiveness to the Canaguche palm, whose orientation indicates the direction of the sun. Smith neatly traces the cartographic impulse to the extractive industries that have cyclically ravaged the region, while conversely illustrating how Silva's successful multispecies wayfinding draws on Indigenous lore. This contrast informs the entire volume, as Smith guides her reader through the ways in which each author grapples with the histories of extractivism and its effects on Indigenous cultures, at times denouncing industrial depredations and at others unexpectedly reinforcing them. Smith's lively syntheses of geocriticism and discourses of extractivism in the introduction will be highly useful to budding scholars—in fact, I have already passed Mapping the Amazon along to several of my PhD students at the University of Virginia. The book sidesteps the broader history of mapping the Amazon in previous centuries to make room for a deep dive into the rubber boom and its afterlives, including impressive archival research and fieldwork undertaken in Colombia and Peru. Smith's definition of extractivism begins with a tight focus on rubber and other physical materials in Gallegos and Rivera, and it expands over the course of the volume to include literary and spiritual extractivism in the works of Vargas Llosa, Calvo, and Souza. Chapter 1, "Reading Maps with La vorágine," interprets the demise of Rivera's famous protagonist Arturo Cova as a cautionary tale of the perils of "cartographic delusion," which Smith defines as "the blind overreliance on maps that are necessarily incomplete," in contrast to Clemente Silva's ability to survive by respecting Indigenous and more-than-human perspectives (44). The twin highlights of chapter 2 are Smith's insights on how debates about education in Venezuela inform Gallegos's Canaima and her pathbreaking reading of the much-analyzed "Tormenta" scene as an interspecies shamanic experience for the main character, Marcos Vargas. Smith's discussion of the Canaima National Park in Venezuela puts her in a fruitful dialogue with the work of Victoria Saramago while also featuring the unjust repercussions of "writing over Carib meanings" in the literary canon and South American societies today. Chapter 3 accuses Mario Vargas Llosa of "openly flaunt[ing] his instrumentalization of Amazonian cultural geography to write and sell books" (102). In line with many leftist diatribes against the Peruvian Nobel laureate, Smith excoriates Vargas Llosa for his involvement with the Summer Institute of Linguistics and his selective mapping of Amazonia in La casa verde, La historia de secreta de una novela, and other works. Chapter 4 is perhaps the most radical in the book for its study of the ayahuasca boom...

A new species of Akodon Meyen, 1833 (Rodentia: Cricetidae) from dry forests of the Amazonia-Cerrado transition

Akodon is the most diverse genus of the tribe Akodontini, comprising 41 extant species. Although distributed in a wide range of environments in South America, the genus was long considered to be absent from Amazon Forest. Nonetheless, in recent decades, records of Akodon have been reported based on specimens from southern Amazonia, throughout the contact zone with Cerrado. Published data about the unique karyotype (2n=10), along with evidence of sister phylogenetic relationship (Cytb sequences) with Akodon cursor, a species from the Atlantic Forest, suggest that these specimens represent an undescribed species. Herein we hypothesize that these samples represent a new species of Akodon from Amazonia-Cerrado transitional areas. Through the analyses of 217 specimens from Mato Grosso and Pará states, Brazil, as well as 336 specimens of Akodon cursor species group from the Atlantic Forest, we provide qualitative and quantitative external and craniodental data that support their distinction in comparison with other congeners. The sister relationship between this new species and A. cursor provide additional evidence of a past connection between the two largest tropical forests of South America. Moreover, the recognition of Akodon n. sp. points to the presence of the genus in the Amazonia-Cerrado transition, an area currently under great anthropic pressure, highlighting the fact that we might be losing a portion of Brazilian biodiversity before even getting to know it.

Lizards (Reptilia: Squamata) from the Caatinga, northeastern Brazil: Detailed and updated overview

AbstractThe Caatinga is the largest seasonal dry tropical forest in South America and it has been historically neglected in terms of its biodiversity. Regarding lizards, different studies led to the current knowledge of diversity and endemism in Caatinga, but detailed syntheses are scarce in the literature. We present the most detailed and up-to-date synthesis of knowledge about Caatinga lizards by providing a detailed (i) list of species; (ii) taxonomic richness patterns; (iii) knowledge gaps and spatial biases; and (iv) detailed distribution maps of all species that contain at least one occurrence record within Caatinga limits. We created a distribution database using occurrences of lizards in Caatinga based on scientific collections, field collection, and literature. We produce up-to-date distribution maps, calculate the Extent of Occurrence and provide the environmental and bioclimatic profile for each species recorded. We draw taxonomic richness and sampling gap maps. Our database has 20,538 records of occurrence of lizards of the Caatinga. We recorded 93 lizard species (13 families), 52.7% of which are endemic. Forthy-four percent of the species present restricted distributions. We identified that 53% of the Caatinga area (or 70% of the municipalities) has no record of occurrence of lizards. The data presented are an important step towards synthesizing in detail the accumulated knowledge about Caatinga lizards and is crucial for accurate strategies for the conservation planning. It directs actions to advance our knowledge on Caatinga lizards: to concentrate inventories in sample void areas; continuous update of the species occurrence database, advance in the generation of autoecology data for species.

Isolation by distance and past climate resistance shaped the distribution of genealogical lineages of a neotropical lizard

Organisms adapted to open environments in South America have recently been used to understand the origins of the high Neotropical biodiversity. In the Caatinga, the largest continuous block of Seasonally Dry Tropical Forest in South America, phylogeographic studies have uncovered the role of historical climate changes and rivers (i.e., the São Francisco River, the largest perennial river in Caatinga), in promoting genetic differentiation and speciation of lizards and amphibians. We used mitochondrial data, demographic analyses, paleodistribution models, and landscape genetic methods to test the effects of spatial distances, historical climate fluctuations, and landscape heterogeneity on the genetic variation of the generalist lizard Tropidurus hispidus in the semi-arid Caatinga in northeastern Brazil. Four haplogroups with moderate geographical structure diverged in the Pleistocene, and exhibited high genetic diversity. Ecological niche models revealed large suitable climatic areas for T. hispidus in the past 790 thousand years, connecting the Caatinga and other regions via a narrow corridor. Part of the genetic differentiation in T. hispidus resulted from spatial distances among populations and isolation by resistance through climatic unsuitability areas in the Last Glacial Maximum (LGM), which probably reduced population connectivity and gene flow. Our findings highlight the role of the historical factors of the Caatinga, through LGM climate, and the generalist condition of species in shaping the genealogical histories of populations. Although the results are based on a single-locus approach, our study is a first step to shed light on the main drivers of the evolutionary history of T. hispidus, in a highly diverse and still poorly studied region.

Neotropical Studies on Hymenochaetaceae: Unveiling the Diversity and Endemicity of Phellinotus.

Phellinotus, a neotropical genus of wood-decay fungi commonly found on living members of the Fabaceae family, was initially described as containing two species, P. neoaridus and P. piptadeniae. The members of this genus, along with six other well-established genera and some unresolved lineages, are the current representatives of the ‘phellinotus clade’. On the other hand, based on a two-loci phylogenetic analysis, some entities/lineages of the ‘phellinotus clade’ have been found in Fomitiporella s.l. In this work, we performed four-loci phylogenetic analyses and based on our results the genera of the ‘phellinotus clade’ are shown to be monophyletic groups. In addition to the natural groups confirmed as different genera, morphological revisions, phylogenetic relationships, and host distribution of different specimens resembling P. neoaridus and P. piptadeniae revealed three new species in the Phellinotus genus, referred to here as P. magnoporatus, P. teixeirae and P. xerophyticus. Furthermore, for P. piptadeniae a narrower species concept was adopted with redefined morphological characters and a more limited distribution range. Both P. neoaridus and P. teixeirae have a distribution range restricted to seasonally dry tropical forests in South America. Additionally, based on detailed morphological revisions Phellinus badius, Phellinus resinaceus, and Phellinus scaber are transferred to the Phellinotus genus. The geographic distribution and host range of the genus are then discussed.

Modeling the potential distribution of cacti under climate change scenarios in the largest tropical dry forest region in South America

Climate change projections for the Brazilian semiarid region for the rest of this century include increased temperature, reduced precipitation and aridification. Consequently, alterations in the distribution of species are expected in the largest seasonally dry tropical forest in South America (Caatinga), which covers 75% of Brazil's semiarid region. This study modeled the potential distribution of eight cactus species native (target species) to the Caatinga under future climate scenarios and analyzed the range shifts of these species during the remainder of this century. Two online biodiversity databases, nine environmental variables and the Maxent algorithm were used, considering the time intervals 1961–1990, 2041–2060 and 2061–2080, along with two Representative Concentration Pathway (RCP) scenarios, 4.5 and 8.5. The potential species distribution models predict that: (1) the future climate conditions are likely to cause contraction or expansion of the areas with high habitat suitability (>0.75) of the target species; (2) species with widespread distribution are likely to be vulnerable to climate change; (3) for some cactus species, climate change will provide an opportunity for expansion, but for the majority it will be a threat to survival; and (4) it is premature to claim that the future vegetation of the Caatinga will be dominated by cacti.

Bat–flower interaction networks in Caatinga reveal generalized associations and temporal stability

AbstractSeasonal variation in precipitation regimes influences species composition and plant–animal interactions. Such temporal variation is especially relevant in the Brazilian Caatinga, the largest Seasonally Dry Tropical Forest in South America, where bat pollination is unusually frequent in comparison with other tropical plant communities. Here, we describe seasonal and annual variations of the interaction networks between nectarivorous bats and flower species in the Caatinga. Five species of nectar‐feeding bats interacted with 30 plant species. Nectarivorous bats showed high levels of interaction overlap, which contributed to ecological generalization (low specialization and modularity) and lack of nestedness in the interaction networks. This pattern was consistent across seasons and years. Chiropterophilous and non‐chiropterophilous plants were equally important components of the interaction network. The generalized interaction patterns found may be a necessary condition for the persistence of nectarivorous bats and their specialized plants in the environmentally harsh and variable Caatinga. The underappreciated generalized interactions of bats with plants calls for studies testing the effectiveness of bats in pollinating the plants they visit, including those not typically categorized as “bat‐flowers”.Abstract in Portuguese is available with online material.

Viability of seeds of some tropical tree species during storage

For most forest species the irregularity of fruiting, low seed production and spatial distribution of trees, make it impossible to supply seeds to meet seedling production programs. On the other hand, to prevent subsequent years of low production and maintain seed viability, it is necessary to adopt adequate storage procedures. Therefore, the objectives of the study were to evaluate the influence of water content and storage conditions on the physiological potential of seeds of Colubrina glandulosa Perkins (Rhamnaceae), Chloroleucon dumosum (Benth.) G.P. Lewis (Fabaceae), Enterolobium contortisiliquum (Vell.) Morong (Fabaceae), Mimosa bimucronata (DC.) O. Kuntze (Fabaceae) and Sapindus saponaria L. (Sapindaceae), which are native tree species in tropical forests in South America. The seeds were placed in paper packaging and glass packaging and stored in a laboratory environment (uncontrolled), during storage periods of zero (recently harvested), three, six, nine, 12 and 15 months. For each storage period, the water content and physiological potential of the seeds were evaluated. The design was entirely randomized with four repetitions of 25 seeds. The germination (G) and germination uniformity (U) data were subjected to analysis of variance in a 2 x 6 factorial arrangement (two types of packaging x six storage periods), and application of polynomial regression. Seeds of Colubrina glandulosa, Chloroleucon dumosum, Enterolobium contortisiliquum, Mimosa bimucronata and Sapindus saponaria, packed in paper packaging or glass packaging, and stored under uncontrolled conditions of natural environment, presented higher G and U, in the storage period of 15 months. The physiological potential of the seeds can be maintained for a long time, as long as they are packed in a glass container with an adequate initial water content. With a water content of 8.2, 8.1, 7.9, 8.4% and 12.1%, the seeds of Colubrina glandulosa, Chloroleucon dumosum, Enterolobium contortisiliquum, Mimosa bimucronata and Sapindus saponaria, respectively, maintain the viability during storage. Therefore, the solution to store these seeds would be to rigorously dry them, and then use waterproof packaging. It is recommended that for the storage of seeds of these tree species, they are previously packaged in glass containers

Fine root dynamics across pantropical rainforest ecosystems.

Fine roots constitute a significant component of the net primary productivity (NPP) of forest ecosystems but are much less studied than aboveground NPP. Comparisons across sites and regions are also hampered by inconsistent methodologies, especially in tropical areas. Here, we present a novel dataset of fine root biomass, productivity, residence time, and allocation in tropical old-growth rainforest sites worldwide, measured using consistent methods, and examine how these variables are related to consistently determined soil and climatic characteristics. Our pantropical dataset spans intensive monitoring plots in lowland (wet, semi-deciduous, and deciduous) and montane tropical forests in South America, Africa, and Southeast Asia (n=47). Large spatial variation in fine root dynamics was observed across montane and lowland forest types. In lowland forests, we found a strong positive linear relationship between fine root productivity and sand content, this relationship was even stronger when we considered the fractional allocation of total NPP to fine roots, demonstrating that understanding allocation adds explanatory power to understanding fine root productivity and total NPP. Fine root residence time was a function of multiple factors: soil sand content, soil pH, and maximum water deficit, with longest residence times in acidic, sandy, and water-stressed soils. In tropical montane forests, on the other hand, a different set of relationships prevailed, highlighting the very different nature of montane and lowland forest biomes. Root productivity was a strong positive linear function of mean annual temperature, root residence time was a strong positive function of soil nitrogen content in montane forests, and lastly decreasing soil P content increased allocation of productivity to fine roots. In contrast to the lowlands, environmental conditions were a better predictor for fine root productivity than for fractional allocation of total NPP to fine roots, suggesting that root productivity is a particularly strong driver of NPP allocation in tropical mountain regions.

Geographical patterns and current and short‐term historical correlates of phylogenetic diversity and endemism for New World primates

AbstractAimAddressing the phylogenetic relationship among species has been insightful to understand evolutionary and biogeographical processes shaping the distribution of diversity across broad geographical gradients. Here we determine the geographical distribution and the variables correlated with the phylogenetic component of diversity and endemism for primates, as well as their relationships with the taxonomic component of diversity.LocationNew World.TaxonNew World monkeys, Platyrrhini.MethodsWe mapped primate occurrence in cells of 110 × 110 km. For each cell, we calculated phylogenetic diversity (PD) and endemism (PE), as well as how much these indices deviate from their expected values based on species richness (SR) and endemism (SE), respectively. Using simultaneous autoregressive models, we tested the effects of mean annual temperature, forest structure and climate history on the current patterns of primate phylogenetic diversity.ResultsWe found that most primate phylogenetic diversity is found in the tropical forests of South America. Tropical forests also present much higher PD and PE than predicted by SR and SE, respectively, demonstrating their importance in producing and maintaining primate phylogenetic diversity in the New World. Furthermore, regions presenting low SR and SE nevertheless show high PE, likely because these areas have witnessed the evolution of many clades occurring exclusively therein. Overall, mean annual temperature had the highest influence in explaining phylogenetic indices.Main conclusionsOur results suggest a strong influence of primate biogeography throughout the New World on the geographical distribution of the phylogenetic component of their diversity, with the Amazon, Atlantic Forest and Central America containing the greatest amount and endemism of phylogenetic diversity. Our study contributes to a better understanding of the dynamics underlying the geographical distribution of New World's primate diversity, especially in a phylogenetic context in which their biogeographical history has deeply affected current patterns of primate diversity in this region. Our results provide essential information for the conservation of primate evolutionary history, especially considering the forecast effects of habitat loss and climate change on the dynamics of tropical forests.

Phylogeography of the specialist plant Mandirola hirsuta (Gesneriaceae) suggests ancient habitat fragmentation due to savanna expansion

The area occupied by tropical forests in South America has continually experienced shrinkage since the Miocene, with the formation of the Dry Diagonal, which is composed of seasonally dry tropical forests and savannas (Caatinga, Cerrado, and Chaco). Here, we contribute to the understanding of the establishment of the Dry Diagonal by testing the hypotheses of “ancestral fragmentation” and of “colonization” to explain the current distribution of species in rocky humid formations of Cerrado, a Neotropical savanna in Brazil. Populations of Mandirola hirsuta (Gesneriaceae) were sampled in 25 localities; these cover the species’ entire geographical distribution, and the plastid intergenic regions psbA-trnH and trnQ-5′-rps16 were sequenced. The findings show that intrapopulation genetic variability was low, whereas interpopulation variability was high. We detected seven genetic groups that were geographically well delimited, and no signs of recent population expansion were observed. Divergence between the seven main lineages took place between the late Miocene and the Pliocene periods. In Approximate Bayesian Computation, the fragmentation scenario had a significantly higher probability than the colonization scenario. Results support the hypothesis of a former broader distribution for the humid vegetation, which was fragmented with the expansion of savannas; results also indicate population differentiation promoted by a rapid expansion of the Dry Diagonal.

Integrating LiDAR, Multispectral and SAR Data to Estimate and Map Canopy Height in Tropical Forests

Developing accurate methods to map vegetation structure in tropical forests is essential to protect their biodiversity and improve their carbon stock estimation. We integrated LIDAR (Light Detection and Ranging), multispectral and SAR (Synthetic Aperture Radar) data to improve the prediction and mapping of canopy height (CH) at high spatial resolution (30 m) in tropical forests in South America. We modeled and mapped CH estimated from aircraft LiDAR surveys as a ground reference, using annual metrics derived from multispectral and SAR satellite imagery in a dry forest, a moist forest, and a rainforest of tropical South America. We examined the effect of the three forest types, five regression algorithms, and three predictor groups on the modelling and mapping of CH. Our CH models reached errors ranging from 1.2–3.4 m in the dry forest and 5.1–7.4 m in the rainforest and explained variances from 94–60% in the dry forest and 58–12% in the rainforest. Our best models show higher accuracies than previous works in tropical forests. The average accuracy of the five regression algorithms decreased from dry forests (2.6 m +/− 0.7) to moist (5.7 m +/− 0.4) and rainforests (6.6 m +/− 0.7). Random Forest regressions produced the most accurate models in the three forest types (1.2 m +/− 0.05 in the dry, 4.9 m +/− 0.14 in the moist, and 5.5 m +/− 0.3 the rainforest). Model performance varied considerably across the three predictor groups. Our results are useful for CH spatial prediction when GEDI (Global Ecosystem Dynamics Investigation lidar) data become available.

Realistic and simplified models of plant and leaf area indices for a seasonally dry tropical forest

Leaf Area Index (LAI) models that consider all phenological stages have not been developed for the Caatinga, the largest seasonally dry tropical forest in South America. LAI models that are currently used show moderate to high covariance when compared to in situ data, but they often lack accuracy in the whole spectra of possible values and do not consider the impact that the stems and branches have over LAI estimates, which is of great influence in the Caatinga. In this study, we develop and assess PAI (Plant Area Index) and LAI models by using ground-based measurements and satellite (Landsat) data. The objective of this study was to create and test new empirical models using a multi-year and multi-source of reflectance data. The study was based on measurements of photosynthetic photon flux density (PPFD) from above and below the canopy during the periods of 2011–2012 and 2016–2018. Through iterative processing, we obtained more than a million candidate models for estimating PAI and LAI. To clean up the small discrepancies in the extremes of each interpolated series, we smoothed out the dataset by fitting a logarithmic equation with the PAI data and the inverse contribution of WAI (Wood Area Index) to PAI, that is the portion of PAI that is actually LAI (LAIC). LAIC can be calculated as follows: LAIC=1-WAI/PAI). We subtracted the WAI values from the PAI to develop our in situ LAI dataset that was used for further analysis. Our in situ dataset was also used as a reference to compare our models with four other models used for the Caatinga, as well as the MODIS-derived LAI products (MCD15A3H/A2H). Our main findings were as follows: (i) Six models use NDVI (Normalized Difference Vegetation Index), SAVI (Soil-Adjusted Vegetation Index) and EVI (Enhanced Vegetation Index) as input, and performed well, with r2 ranging from 0.77 to 0.79 (PAI) and 0.76 to 0.81 (LAI), and RMSE with a minimum of 0.41 m2 m−2 (PAI) and 0.40 m2 m−2 (LAI). The SAVI models showed values 20% and 32% (PAI), and 21% and 15% (LAI) smaller than those found for the models that use EVI and NDVI, respectively; (ii) the other models (ten) use only two bands, and in contrast to the first six models, these new models may abstract other physical processes and components, such as leaves etiolation and increasing protochlorophyll. The developed models used the near-infrared band, and they varied only in relation to the inclusion of the red, green, and blue bands. (iii) All previously published models and MODIS-LAI underperformed against our calibrated models. Our study was able to provide several PAI and LAI models that realistically represent the phenology of the Caatinga.

Heightened levels and seasonal inversion of riverine suspended sediment in a tropical biodiversity hot spot due to artisanal gold mining

In recent years, rising gold prices have exacerbated the global proliferation of artisanal-scale gold mining (ASGM), with catastrophic consequences for human and ecological health. Much of this burgeoning industry has occurred in biodiversity hot spots, notably in the tropical forests of South America. While the loss of tropical forests and floodplains as a result of ASGM has been well characterized, ASGM impacts on riverine hydrological properties are less understood. Previous fieldwork on ASGM-affected and gully-eroded tropical streams and rivers has demonstrated that increases in suspended-sediment concentration (SSC) can substantially impact fish diversity and aquatic community structure, yet our understanding of the timing and scope of impacts of such increases is limited by the lack of long-term records of SSC. To address this challenge, we present a 34-y analysis of the direct effect of ASGM on 32 river reaches in the Madre de Dios region of Peru, which has been heavily impacted by ASGM since the 1980s. We evaluate spatial and temporal patterns of impacts using estimated SSC derived from Landsat satellite imagery. We find that 16 of 18 stretches of river impacted by ASGM show significant increasing trends in SSC (P < 0.05), while only 5 of 14 unaffected sites do so. Additionally, ASGM appears to reverse natural seasonal cycles of SSC, which may imperil aquatic species. Overall, our findings indicate that ASGM is fundamentally altering optical water quality dynamics of a critical tropical biodiversity hot spot and provide guidance for future regulation of these activities.

Long-term impacts of mid-Holocene drier climatic conditions on Bolivian tropical dry forests

AbstractThe Bolivian Chiquitano dry forest is the largest block of intact seasonally dry tropical forest in South America and is a priority ecoregion for conservation due to its high threat status. However, the long-term impacts of drier climatic conditions on tropical dry forests are not well understood, despite climate models predicting increased droughts over Bolivia in the coming century. In this paper, we assess the impacts of drier climatic conditions during the mid-Holocene on the Bolivian Chiquitano tropical dry forest using fossilised pollen, phytoliths, macro-charcoal, and geochemical proxies from a sediment core from a large lake (Laguna Mandioré) on the Bolivia–Brazil border. Our results show that drier climatic conditions during the mid-Holocene caused a local-scale, ecotonal expansion of upland savannah at the expense of dry forest. Interaction between drier climatic conditions and fire regime likely exerted a stronger control over the position of the dry forest–savannah ecotone than edaphic factors. However, the majority of the dry forest within the lake catchment maintained a closed canopy throughout the drier conditions of the mid-Holocene, despite floristic turnover towards more drought-tolerant taxa. These findings imply overall resilience of the Chiquitano dry forest biome to future drought, albeit with floristic changes and upland savannah encroachment at ecotones.

Notes on the Trip to the Great Savannah

In July 1947, the Cuban Author Alejo Carpentier traveled from his home in caracas to the sparsely inhabited interior of venezuela, visiting the country's tropical forests and its great plains. At the time, Carpentier was known principally as a music critic and newspaper columnist for El Nacional in Venezuela and Carteles in Cuba; he had yet to publish El reino de este mundo (The Kingdom of This World; 1949), which would launch his career as a novelist and earn him international renown. Carpentier later wrote a novel about a trip much like the one he took in 1947. In the now-canonical Los pasos perdidos (The Lost Steps; 1953), a failed composer finds inspiration by traveling from a cosmopolitan city to the tropical forests of South America. Carpentier's creativity was similarly sparked by his trip to the Venezuelan wilderness, as his travel diary Notas del viaje a la Gran Sabana (Notes on the Trip to the Great Savannah) makes clear. Notas is the only contemporary account of the journey written by Carpentier, who later made contradictory statements about the details and even the number of trips he took. Beyond its documentary value, the travel diary reveals that Carpentier's experience was deeply enmeshed with his readings, a characteristic that also marks the narrator-protagonist of Los pasos perdidos. Moreover, Notas is of broad ecocritical and historical significance because it makes clear the extent to which the forests and plains of South America were changing during Venezuela's boom in oil drilling and gold mining in the 1940s. Inspired by what he witnessed in Venezuela, Carpentier created the central drama of Los pasos perdidos out of his protagonist's desire to inhabit what the author called the “mundo del Genesis” (“world of Genesis”) at a time when extractive industries were rapidly transforming the economies, ecologies, and societies of the region (“La Gran Sabana” 32).

Defaunation of large-bodied frugivores reduces carbon storage in a tropical forest of Southeast Asia

Recent studies have suggested that defaunation of large-bodied frugivores reduces above-ground carbon storage in tropical forests of South America and Africa, but not, or less so, in Southeast Asian tropical forests. Here we analyze the issue using the seed dispersal network (data of interaction between trees and animal seed dispersers) and forest composition of a 30-ha forest dynamics plot in central Thailand, where an intact fauna of primates, ungulates, bears and birds of all sizes still exists. We simulate the effect of two defaunation scenarios on forest biomass: 1) only primates extirpated (a realistic possibility in near future), and 2) extirpation of all large-bodied frugivores (LBF) including gibbons, macaques, hornbills and terrestrial mammals, the main targets of poachers in this region. For each scenario, we varied the population size reduction of the LBF dispersed tree species from 20% to 100%. We find that tree species dependent on seed dispersal by large-bodied frugivores (LBF) account for nearly one-third of the total carbon biomass on the plot, and that the community turnover following a complete defaunation would result in a carbon reduction of 2.4% to 3.0%, depending on the defaunation scenario and the model assumptions. The reduction was always greater than 1% when the defaunation intensity was at least 40%. These effect sizes are comparable to values reported for Neotropical forests, suggesting that the impact of defaunation on carbon deficit is not necessarily lower in Southeast Asian forests. The problem of defaunation in Asia, and the mutual benefits between biodiversity conservation and climate change mitigation, should therefore not be neglected by global policies to reduce carbon emissions.