Seasonally Dry Tropical Forests Research Articles

How Forest Management with Clear-Cutting Affects the Regeneration, Diversity and Structure of a Seasonally Dry Tropical Forest in Brazil

In Brazil, logging in the Seasonally Dry Tropical Forest (SDTF) under management plans that include clear-cutting has increased in recent decades, and the structure, composition, diversity and functioning of the forest likely must have been affected. The aim of this study was to understand the growth dynamics of shrub–tree biomass (STB), species richness and vegetation structure as a function of regeneration time after clear-cutting (treatments), taking the Legal Reserve (40 years of regeneration) as reference. The study was carried out in 2018 at the Ramalhete Settlement, General Sampaio, in the state of Ceará. All plants with a circumference at breast height (CBH) ≥ 6 cm were identified and the CBH was measured across 42 sample plots (20.0 m × 20.0 m), using seven plots per treatment (3, 5, 8, 11 and 15 years after clear-cutting, and the Legal Reserve, 40 years of regeneration). The following were determined: STB (total and by species), density and basal area (by ecological group and diameter class), basal area (species of higher added value), diversity (Hill numbers), and the importance value index (IVI). It was found that during the early years (up to at least 11 years), many important forest characteristics related to the composition of the ecological groups and vegetation structure were strongly affected, and major impacts can be seen, the effects of which, however, decreased over time of regeneration, having almost no effect after 15 years. After 15 years following clear-cutting, the SDTF presented accumulated STB, species richness and structure similar to the area undergoing regeneration for 40 years. However, the small number of indicator species of more-preserved areas (even at T15 and T40) points out that management needs to be improved. However, promoting species of greater added value and determining whether the forest recovers its structure and diversity after successive cutting cycles also still need to be addressed.

Can size make a difference? Cross-predation occurrences between lizards and scorpions in the Brazilian seasonal dry tropical forest

Can size make a difference? Cross-predation occurrences between lizards and scorpions in the Brazilian seasonal dry tropical forest

Wind farm noise and anuran diversity patterns: a case study in Brazilian seasonal dry tropical forest

ABSTRACT Noise pollution contributes to the global biodiversity crisis, however the consequences of this pollution on anuran diversity patterns are poorly understood. This is especially true of less evident sources of noise like wind farms and highly exploited areas, as in the Brazilian semi-arid region. Here, we evaluated the influence of wind farm noise on anuran assemblages’ diversity at the Caatinga, a seasonal dry tropical forest in Brazil. We tested the hypothesis that wind farm noise negatively affects the diversity of anuran assemblages in terms of abundance, species richness and composition. Anurans were sampled in 19 temporary ponds along a noise gradient in two wind farms over a rainy season (March to August). A total of 2,047 individuals belonging to 20 species were recorded. Our results suggest that wind farm noise has a non-significant relationship with anuran diversity patterns (species richness, composition and abundance). To our knowledge, this is the first investigation into the effects of wind farm noise on anuran assemblages in the Caatinga dry forest. Despite our results suggesting that anuran diversity is insensitive to noise pollution caused by wind farms, identification of emerging threats is essential to mitigate impacts on anuran populations which are declining globally.

Registro de depredación intragremial del escorpión Physoctonus debilis (C. L. Koch, 1840) (Scorpiones: Buthidae) por la chinche Microtomus tibialis Stichel, 1926 (Hemiptera: Reduviidae)

Scorpions and assassin bugs are arthropod predators that may impact in trophic chain, coexisting in similar microhabitats and exhibiting antagonistic interactions. This study reports the first case of predation of the scorpion Physoctonus debilis by the assassin bug Microtomus tibialis in a Brazilian Seasonal Dry Tropical Forest biome. During a nocturnal collection, an adult individual of M. tibialis was observed, with the head and body facing downwards, while holding a female of P. debilis, with the aid of the mouthparts under the vegetation. Reports like these are important to understand the evolutionary dynamics and natural history of predators that cohabit in the same microhabitat.

Phylogenomics of One of the World’s Most Intriguing Groups of CAM Plants, the Opuntioids (Opuntioideae: Cactaceae): Adaptation to Tropical Dry Forests Helped Drive Prominent Morphological Features in the Clade

Opuntioideae, composed of roughly 370 species, occur in almost every biome in the Americas, from seasonally dry tropical forests (SDTF) to high-elevation Andean grasslands, American deserts and temperate zones. The interrelationships among the three major clades of Opuntioideae (Cylindropuntieae, Opuntieae and Tephrocacteae) are not well resolved, and thus, the ancestral habitat, biogeographic history and evolution of morphological characters, such as large photosynthetic leaves and flattened stems, are poorly understood. To test their geographic origin and evolution of key morphological characters, we built the largest phylogenomic dataset for Cactaceae to date using 103 plastid genes of 107 taxa of Opuntioideae. The subfamily Opuntioideae likely evolved in South America in a combination of seasonally dry tropical forest (SDTF)/desert habitats. Opuntieae most likely evolved in South America in SDTF and, from there, moved into desert regions, Chaco and temperate/subtropical zones, while Tephrocacteae and Cylindropuntieae evolved in South America in desert regions and moved into SDTF, Chaco and temperate/subtropical zones. Analyses of morphological evolution suggest that, although large leaves are plesiomorphic in Opuntioideae, long-lived, photosynthetically active leaves in Cylindropuntieae and Tephrocacteae are homoplasious and do not represent retained plesiomorphy, as is often assumed. Flattened stems are synapomorphic for Opuntieae, possibly representing adaptation to competition for light resources in SDTF, their most likely ancestral area.

The role of chronic anthropogenic disturbances in plant community assembly along a water availability gradient in Brazil’s semiarid Caatinga region

The effects of anthropogenic disturbances on the structure and function of seasonally dry tropical forests (SDTFs) are mediated both by disturbance type and intensity, and the environmental conditions, including climate. In a climate change scenario, the interaction between low water availability and chronic anthropogenic disturbances may potentially have drastic consequences on SDTF dynamics and the ecosystem services it provides. We hypothesized that in these naturally stressed systems, the effects of human disturbance are strongest in the most water-stressed sites, implying a worrisome synergism between harsh abiotic conditions (lower precipitation, higher temperature) and human effects, ultimately resulting in a less developed community structure and reduced diversity. By integrating information for the adult and regenerating vegetation strata in 21 sites distributed across climatic, plant cover and disturbance gradients in the Caatinga (seasonally dry tropical) forest of Brazil, we analyzed the individual and combined effects of chronic anthropogenic disturbances, as measured through the Cattle Pressure Index and the Human Activity Index, along climate gradients, on community structure, diversity, and composition. As expected, the Cattle Pressure Index was negatively related to diameter at ground level, basal area, and diversity in the adult stratum, whereas for the regenerating stratum, litter stock had the strongest effect on vegetation structure. Climatic factors were poor predictors of the variation in the three true diversity measures (0D, 1D, and 2D) of the regenerating community. Our results revealed important cross-site differences in both vegetation strata over a small range of climatic variation. We conclude that the most stressful conditions associated with a very low precipitation regime enhance the effects on chronic disturbances, gradually driving SDTF communities into new alternative states and rendering these environments more prone to desertification.

A new, disjunct species of Bahiana (Euphorbiaceae, Acalyphoideae): Phytogeographic connections between the seasonally dry tropical forests of Peru and Brazil, and a review of spinescence in the family.

Bahiana is expanded from 1 to 2 species with the description of B.occidentalis K. Wurdack, sp. nov. as a new endemic of the seasonally dry tropical forests (SDTFs) of Peru. The disjunct distribution of Bahiana with populations of B.occidentalis on opposite sides of the Andes in northwestern Peru (Tumbes, San Martín) and B.pyriformis in eastern Brazil (Bahia) adds to the phytogeographic links among the widely scattered New World SDTFs. Although B.occidentalis remains imperfectly known due to the lack of flowering collections, molecular phylogenetic results from four loci (plastid matK, rbcL, and trnL-F; and nuclear ITS) unite the two species as does gross vegetative morphology, notably their spinose stipules, and androecial structure. Spinescence in Euphorbiaceae was surveyed and found on vegetative organs in 25 genera, which mostly have modified sharp branch tips. Among New World taxa, spines that originate from stipule modifications only occur in Bahiana and Acidocroton, while the intrastipular spines of Philyra are of uncertain homologies.

Ensemble Machine Learning for Mapping Tree Species Alpha-Diversity Using Multi-Source Satellite Data in an Ecuadorian Seasonally Dry Forest

The increased variety of satellite remote sensing platforms creates opportunities for estimating tropical forest diversity needed for environmental decision-making. As little as 10% of the original seasonally dry tropical forest (SDTF) remains for Ecuador, Peru, and Colombia. Remnant forests show high rates of species endemism, but experience degradation from climate change, wood-cutting, and livestock-grazing. Forest census data provide a vital resource for examining remote sensing methods to estimate diversity levels. We used spatially referenced trees ≥5 cm in diameter and simulated 0.10 ha plots measured from a 9 ha SDTF in southwestern Ecuador to compare machine learning (ML) models for six α-diversity indices. We developed 1 m tree canopy height and elevation models from stem mapped trees, at a scale conventionally derived from light detection and ranging (LiDAR). We then used an ensemble ML approach comparing single- and combined-sensor models from RapidEye, Sentinel-2 and interpolated canopy height and topography surfaces. Validation data showed that combined models often outperformed single-sensor approaches. Combined sensor and model ensembles for tree species richness, Shannon’s H, inverse Simpson’s, unbiased Simpson’s, and Fisher’s alpha indices typically showed lower root mean squared error (RMSE) and increased goodness of fit (R2). Piélou’s J, a measure of evenness, was poorly predicted. Mapped tree species richness (R2 = 0.54, F = 27.3, p = <0.001) and Shannon’s H′ (R2 = 0.54, F = 26.9, p = <0.001) showed the most favorable agreement with field validation observations (n = 25). Small-scale model experiments revealed essential relationships between dry forest tree diversity and data from multiple satellite sensors with repeated global coverage that can help guide larger-scale biodiversity mapping efforts.

Fire Impacts and Dynamics of Seasonally Dry Tropical Forest of East Java, Indonesia

(1) Background: Seasonally dry tropical forests (SDTFs) are globally important ecosystems which receive less research attention compared to tropical rainforests but are equally under serious threat. The objectives of this paper are to characterize the vegetation structure, diversity and composition of SDTF of Baluran National Park, East Java, Indonesia, and to assess the impact of burning this SDTF and its post-fire recovery. (2) Methods: In the field, we measured floristic composition and dominance at sites with different fire histories in both SDTF and adjacent savannas of Baluran. Remote sensing image analysis was also employed using the MODIS burn area product and various thematic maps. (3) Results: SDTF at Baluran has moderately high tree cover, is less diverse in species than rainforest, and has a prominent vegetative response to fire, especially in the tree layer. The immediate post-fire period in SDTF featured lower densities of tree seedlings and saplings, more grasses and herbs, and lower species richness than older unburned forest. Species composition varied with fire age and vegetation type, with relatively rapid recovery with time since fire evident, although there was some convergence of long-unburned savanna and SDTF sites in terms of floristics. (4) Conclusions: The SDTF of Baluran recovers after fire principally via resprouting but also via seedling regeneration, with structural attributes returning more quickly (<10 years) than floristic composition (>10 years). We did not find consistent evidence of ecosystem transitions between SDTF and savanna despite a small number of long-unburned savanna sites having floristic similarities to dry forest (particularly in terms of characteristic tree species), and we identify the need for more study to determine the degree and mechanisms of forest–savanna transitions in the region, with a future research agenda outlined. Relatively large areas of savanna–dry forest transitions demonstrated from remote sensing analyses were primarily attributed to spread of Acacia nilotica (an alien invasive small tree or shrub) into long-unburned savanna, and its decline in areas where the species is being successfully controlled via burning and cutting. Knowledge of such ecological shifting is important for the ecosystem management, especially in terms of their usage by large mammals.

Mapping wood volume in seasonally dry vegetation of Caatinga in Bahia State, Brazil

The Caatinga biome in Brazil comprises the largest and most continuous expanse of the seasonally dry tropical forest (SDTF) worldwide; nevertheless, it is among the most threatened and least studied, despite its ecological and biogeographical importance. The spatial distribution of volumetric wood stocks in the Caatinga and the relationship with environmental factors remain unknown. Therefore, this study intends to quantify and analyze the spatial distribution of wood volume as a function of environmental variables in Caatinga vegetation in Bahia State, Brazil. Volumetric estimates were obtained at the plot and fragment level. The multiple linear regression techniques were adopted, using environmental variables in the area as predictors. Spatial modeling was performed using the geostatistical kriging approach with the model residuals. The model developed presented a reasonable fit for the volume m3 ha with r2 of 0.54 and Root Mean Square Error (RMSE) of 10.9 m3 ha–1. The kriging of ordinary residuals suggested low error estimates in unsampled locations and balance in the under and overestimates of the model. The regression kriging approach provided greater detailing of the global wood volume stock map, yielding volume estimates that ranged from 0.01 to 109 m3 ha–1. Elevation, mean annual temperature, and precipitation of the driest month are strong environmental predictors for volume estimation. This information is necessary to development action plans for sustainable management and use of the Caatinga SDTF in Bahia State, Brazil.

Differences in the structure of bat assemblages among habitats in the Caatinga dry forest

Abstract The Caatinga is the largest seasonal tropical dry forest with extreme environmental and meteorological conditions. It harbours many phytophysiognomies and vegetational units, but bat fauna is poorly known in many regions. We analysed the structure of bat assemblages by mist-netting during 99 nights in seven habitats throughout six sites in the northeasternmost region of the Caatinga in Rio Grande do Norte State, in the Brazilian northeast. With a sampling effort of 239 665 m2h, we captured 1575 individuals of 31 species of bats. Bat assemblages’ structure and species distribution changed according to the habitat type, and differences in richness, abundance, species composition, and trophic guild representation were found. The frugivore A. planirostris was widespread, and its superabundance hold for all habitats. The distinct array of the most abundant species with several exclusive species in each habitat suggests species- and trophic guild-specific preferences to particular habitats. Differences in the structure of bat assemblages may be driven by each habitat’s vegetational structure and plant composition (e.g., semi-open habitats vs. tall forest stands) that offers distinct exploitable resources (e.g., food and roosts). Finally, we discuss the importance of foraging habitats for the conservation of these unique bat assemblages in the northeasternmost region of the Caatinga dry forest.

Land-Use and Land-Cover Dynamics in the Brazilian Caatinga Dry Tropical Forest

The use of remote sensing to determine land-use and land-cover (LULC) dynamics is often applied to assess the levels of natural forest conservation and monitor deforestation worldwide. This study examines the loss of native vegetation in the Campo Maior Complex (CMC), in the Brazilian Caatinga dry tropical forest, from 2016 to 2020, considering the temporal distribution of rainfall and discussing the trends and impacts of forest-degradation vectors. The Google Earth Engine (GEE) platform is used to obtain the rainfall data from the CHIRPS collection and to create the LULC maps. The random forest classifier is used and applied to the Landsat 8 collection. The QGIS open software and its SPC plugin are used to visualize the LULC dynamics. The results show that the months from June to October have the lowest average rainfall, and that 2019 is the year with the highest number of consecutive rainy days below 5 mm. The LULC maps show that deforestation was higher in 2018, representing 20.19%. In 2020, the proportion of deforestation was the lowest (11.95%), while regeneration was the highest (20.33%). Thus, the characterization of the rainfall regime is essential for more accurate results in LULC maps across the seasonally dry tropical forests (SDTF).

Micropropagation and Germplasm Conservation of Ficus americana Aubl. and F. obtusifolia Kunth from Lambayeque (Peru)

Ficus americana and F. obtusifolia are among the most important tree species in Seasonally Dry Tropical Forests (SDTF) due to their evergreen condition and high levels of biomass. However, the SDTF of Lambayeque and northern Peru is greatly diminishing due to the advance of migratory agriculture, illegal mining, and deforestation. The objective of this work was to study the taxonomic aspects of both species, as well as seed germination, micropropagation, and in vitro germplasm conservation. Seed germination was 100% for both species up to three months after collection. As for micropropagation, rooting, and germplasm conservation, the Piper culture medium was effective, as it was constituted by MS mineral salts with 0.02 mg.L-1 IAA and 0.02 mg.L-1 GA3. In vitro germplasm conservation lasted more than 24 months for both species. Acclimatization under greenhouse conditions reached 50% survival for both species.

Gross primary productivity by remote sensing in the Serra das Confusões National Park, Piauí, Brazil

The increase in anthropogenic CO2 emissions has raised the Earth's surface temperature in an anomalous and unprecedented way. Among the activities that contribute most to these increased emissions is the burning of fossil fuels and the change in land use. Part of these emissions are absorbed by terrestrial ecosystems, potentially productive and important carbon sinks (C) among them, we can mention the seasonally dry tropical forests (SDTF), which are found mainly in the Caatinga biome. Although little explored, the role they play in the global carbon (C) cycle is not negligible. Therefore, this research aimed to evaluate the seasonal behavior of biophysical variables and their effect on gross primary productivity (GPP) in a Conservation Unit in the Caatinga biome. The study area is located in the Conservation Unit (UC) of the Serra das Confusões National Park, located in the southwest region of the state of Piauí. Data for the years 2010–2020 were obtained from the MODIS sensor, which is inserted in the Terra satellite. Data on air temperature, precipitation, relative humidity and global solar radiation were obtained from the National Institute of Meteorology. According to the results obtained, the dynamics of GPP is modulated by the seasonal distribution of precipitation, presenting an average value of 5.53 gC m−2 day−1 in the months of higher precipitation and 1.43 gC m−2 day−1 in the period of lower precipitation. Additionally, precipitation also exerts a strong influence on vegetation status, as observed from the Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI) and Leaf Area Index (LAI) the maximum values observed during the rainy season, reflecting directly on the radiative and water components. However, even subjected to adverse environmental conditions, the potential of the area as a sink for C. Thus, in a future scenario of projected climate changes, and considering the vulnerability of these ecosystems, studies that evaluate the seasonal behavior of its structure and functioning is of fundamental importance for the knowledge of its resilience mechanisms and also as a contribution to the implementation of public policies that promote the conservation of the ecosystem.

Small mammals from the Caatinga: A dataset for the Brazilian semiarid biome.

The Caatinga is an exclusively Brazilian biome, and is the largest and most biodiverse Seasonal Tropical Dry Forest in the world. Despite that, the mammalian fauna, especially small mammals, is the least studied of all Brazilian biomes. In order to fill gaps and provide detailed information on small mammals (Didelphimorphia, Rodentia) in the Caatinga biome, we compiled reliable records focusing on richness, composition and some biometric data. These records came from mammal collections, papers, theses, books, and unpublished data, prioritizing records with vouchers housed in scientific collections. We compiled a total of 3133 records from 816 locations, resulting in a richness of 47 native species (12 marsupials and 35 rodents, plus three exotic rodents, Rattus rattus, Rattus norvegicus, and Mus musculus). This dataset includes records of three new species for the biome and its transition zone: the rodents Calomys mattevii, Holochilus oxe, and Nectomys squamipes. Of the total number of records, 1808 (57.71%) are from consulting activities, 95 (3.03%) are from zoonoses studies and 104 (3.32%) are from the National Plague Service (SNP). All nine Brazilian states with territory in the Caatinga have sampling data for small mammals, but the number of records and localities are unevenly distributed, with the state of Rio Grande do Norte having the lowest number of records and locations sampled. Our dataset is the first of its kind for the Caatinga biome and has considerable potential value for studies of habitat use, landscape ecology, macroecology, biogeography, and conservation. There are no copyright restrictions on the data. Please cite this data paper when the data are used in publications. We also request that researchers and teachers inform us of how they are using the data.

Disparate biomes within the Caatinga region are not part of the same evolutionary community: A reply to Araujo et al. (2022)

In recent attempts to estimate plant and bird species diversity in the Caatinga, the largest nucleus of the Seasonally Dry Tropical Forest and Woodland biome in South America, we called into question a widely used delimitation of this region that includes areas of disparate biomes. We argued that the Caatinga is best delimited without rainforest and savanna enclaves that exist in the region, and that such enclaves should be treated as part of those other biomes rather than part of the Caatinga. In a response to our proposal, Araujo et al. (2022) advocated the continued adoption of that broader delimitation. Here we review Araujo et al.’s (2022) criticism and elaborate on this problem. We demonstrate that using a delimitation of the Caatinga that includes areas of disparate biomes precludes measures of biome-specific information, cross-biome comparisons, and large-scale syntheses, and we argue that such a delimitation is a poor framework for both studies of biological phenomena and regional conservation planning.

Effects of Fire on Diversity and Aboveground Biomass of Understory Communities in Seasonally Dry Tropical Forest in Western Thailand

Fire is a necessary disturbance in tropical deciduous forests, as it helps clear the understory community and allows regeneration of grasses and forbs for local wildlife. Huai Kha Khaeng Wildlife Sanctuary (HKK) and Huai Thab Salao-Huai Rabum Non-Hunting Area (HTS) are parts of a few places in Southeast Asia with deciduous forests. However, this area was heavily logged up until 1989, followed by a long period of fire suppression. The consequences of these changes on understory communities have not been investigated. Therefore, the current study aimed to examine the understory communities and their aboveground biomass before and after the annual prescribed burns in HKK and HTS. Understory plant composition and biomass were surveyed in November 2018 (before the fire) and May 2019 (three months after the fire) in 128 temporary plots, covering of deciduous dipterocarp forest, mixed deciduous forest, mixed deciduous forest with bamboo, and open area. We identified a total of 480 understory species, including 37 grass species, 214 forb species, 73 shrub species, 153 tree seedling species and three species of bamboo in the study plots. Grasses in the DDF plots were at 72.79 ± 22.41 kg ha−1, accounting for only ten percent of the understory plants in the plots. The understory community in the DDF plots was dominated by shrubs and tree seedlings of competing species, especially after the fire. The results suggested that past logging activities and long-term fire suppression had reduced the number of mature key dipterocarp forests and hindered the regeneration of grasses and forbs. Maintaining the structure of dipterocarp forests and sufficient food sources for the local wildlife species will require more active habitat management of the study areas.

Scented at day and night: diel variation in the floral scent chemistry of the threatened tree Amburana cearensis (Leguminosae) and effects of this variation on its pollinators

The reproductive success of most angiosperms depends on pollinators. A combination of floral traits, including olfactory cues, are involved in attracting these animals. The emission and chemical composition of floral volatile organic compounds (VOCs) is often associated with the sensory preferences of the most frequent floral visitors. However, the relationship between VOCs and nocturnal and diurnal pollinators is poorly known in tropical dry forests. Our study describes the dynamics of floral scent chemistry throughout the anthesis of Amburana cearensis (Leguminosae) and its association with floral visitors in the Caatinga dry forest, one of the largest expanses of seasonally dry tropical forest (SDTF) in the world. The species is a threatened tree with high socioeconomic importance in the Caatinga and other SDTFs of South America (exploited for timber and medicinal uses). Its flowers emit an intense, pleasant and sweet fragrance throughout anthesis, starting at ∼16:00 h and ending at ∼15:00 h of the following day (lasting 23 h). We used dynamic headspace sampling and gas chromatography coupled with mass spectrometry (GC-MS) to collect and analyze the floral scent within a natural population. The fragrance of A. cearensis was characterized by the dominant presence of monoterpenes, especially linalool and (Z)-linalool oxide (furanoid) and (Z)-linalool oxide (pyranoid), as well as (E,E)-α-farnesene and an aromatic benzenoid, benzyl alcohol. The relative proportions of floral VOCs emitted by A. cearensis changed during anthesis, with a marked presence of linalool in daytime samples (day: 45% / night: 27%) and furanoid (Z)-linalool oxide at night (day: 12% / night: 29%). The dominance of benzyl alcohol, linalool and its oxides in the floral scent of A. cearensis is possibly related to the attraction of nocturnal and diurnal Lepidoptera as pollen vectors. Indeed, we observed six species of butterflies and seven species of moths pollinating the flowers of A. cearensis in 41 h of observations. However, other terpenoids in the fragrant blend possibly contribute to the attraction of additional diurnal floral visitors, including bees, which are also effective pollinators. The continuous scent production throughout anthesis, and the changes in floral scent with a peak of linalool production during the day, may be related to the wide spectrum of pollinators of A. cearensis. This association between floral visitors and dynamics of VOCs presentation may therefore increase the reproductive success of the species, which only blooms every two years and is strictly self-incompatible.

Effects of El Niño drought on seedling dynamics in a seasonally dry tropical forest in Northern Thailand.

As El Niño is predicted to become stronger and more frequent in the future, it is crucial to understand how El Niño-induced droughts will affect tropical forests. Although many studies have focused on tropical rainforests, there is a paucity of studies on seasonally dry tropical forests (SDTFs), particularly in Asia, and few studies have focused on seedling dynamics, which are expected to be strongly affected by drought. Seedlings in SDTFs are generally more drought-tolerant than those in the rainforests, and the effects of El Niño-induced droughts may differ between SDTF and tropical rainforests. In this study, we explored the impact of El Niño-induced drought at an SDTF in northern Thailand by monitoring the seedling dynamics at monthly intervals for 7 years, including a period of strong El Niño. The effects were compared between two forest types in an SDTF: a deciduous dipterocarp forest (DDF), dominated by deciduous species, and an adjacent lower montane forest (LMF) with more evergreen species. El Niño-induced drought increased seedling mortality in both the forest types. The effect of drought was stronger in evergreen than in the deciduous species, resulting in higher mortality in the LMF during El Niño. However, El Niño increased seedling recruitment only in the DDF, mainly because of the massive recruitment of the deciduous oak, Quercus brandisiana (Fagaceae), which compensated for the mortality of seedlings in the DDF. As a result, El Niño increased seedling density in the DDF and decreased it in the LMF. This is the first long-term study to identify the differences in the impacts of El Niño on seedlings between the two forest types, and two leaf habits, evergreen and deciduous, in Southeast Asia. Our findings suggest that future climate change may alter the species composition and spatial distribution of seedlings in Asian SDTFs.

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.