Tropical Forest Biome Research Articles

Community Structure in an Isolated Tropical Forest Biome: One Year of Fruit-Feeding Butterfly Trapping in Four Habitats in the Western Ghats, India

Insect communities in tropical forests tend to be structured vertically and with respect to tree fall gaps and edges. Furthermore, insect communities vary over time. Insight into such habitat specificity and temporal variation is needed to design and interpret biodiversity surveys and to compare conservation value among habitats. Some aspects of tropical insect community structure, such as the proportion of canopy specialists and temporal variation, vary among biogeographical regions and climatic zones. To date, few regions have been sampled systematically, so generalization remains difficult. We compared fruit-feeding butterfly communities among understory, canopy, natural treefalls, and forest edge, in a tropical forest of the Western Ghats, a strip of rainforest that is isolated from Sundaland, the large rainforest block of South-East Asia. During a yearlong study, we captured 3018 individuals belonging to 32 species and representing 14 genera. While some butterflies were captured in the canopy, no species was significantly more abundant in the canopy than in the understory. This observation was contrary to studies elsewhere in the tropics where 14–55% of the species could be classified as canopy specialists. Even though the largest number of species was captured at forest edges, species diversity was highest in the gaps. The communities at the forest edge differed importantly from those in treefall gaps: at the forest edge, we caught grassland species in addition to the forest species. Larger treefall gaps had higher butterfly abundance than smaller gaps. Both abundance and diversity peaked during the late monsoon season, and all common species in our sample also peaked during this period. The spatiotemporal community structure appears to depend on biogeography (less vertical stratification further from large forest blocks) and climate (more synchrony among species in seasonal abundance when there is a more severe dry season).

Implications of zero-deforestation palm oil for tropical grassy and dry forest biodiversity.

Many companies have made zero-deforestation commitments (ZDCs) to reduce carbon emissions and biodiversity losses linked to tropical commodities. However, ZDCs conserve areas primarily based on tree cover and aboveground carbon, potentially leading to the unintended consequence that agricultural expansion could be encouraged in biomes outside tropical rainforest, which also support important biodiversity. We examine locations suitable for zero-deforestation expansion of commercial oil palm, which is increasingly expanding outside the tropical rainforest biome, by generating empirical models of global suitability for rainfed and irrigated oil palm. We find that tropical grassy and dry forest biomes contain >50% of the total area of land climatically suitable for rainfed oil palm expansion in compliance with ZDCs (following the High Carbon Stock Approach; in locations outside urban areas and cropland), and that irrigation could double the area suitable for expansion in these biomes. Within these biomes, ZDCs fail to protect areas of high vertebrate richness from oil palm expansion. To prevent unintended consequences of ZDCs and minimize the environmental impacts of oil palm expansion, policies and governance for sustainable development and conservation must expand focus from rainforests to all tropical biomes.

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.

Mapping tropical forest functional variation at satellite remote sensing resolutions depends on key traits

Although tropical forests differ substantially in form and function, they are often represented as a single biome in global change models, hindering understanding of how different tropical forests will respond to environmental change. The response of the tropical forest biome to environmental change is strongly influenced by forest type. Forest types differ based on functional traits and forest structure, which are readily derived from high resolution airborne remotely sensed data. Whether the spatial resolution of emerging satellite-derived hyperspectral data is sufficient to identify different tropical forest types is unclear. Here, we resample airborne remotely sensed forest data at spatial resolutions relevant to satellite remote sensing (30 m) across two sites in Malaysian Borneo. Using principal component and cluster analysis, we derive and map seven forest types. We find ecologically relevant variations in forest type that correspond to substantial differences in carbon stock, growth, and mortality rate. We find leaf mass per area and canopy phosphorus are critical traits for distinguishing forest type. Our findings highlight the importance of these parameters for accurately mapping tropical forest types using space borne observations.

Conservation of Biocultural Diversity in the Huasteca Potosina Region, Mexico

The Huasteca Potosina region has a relevant landscape heritage of biocultural diversity, due to high biological diversity and the presence of the Teenek (Huastec Mayan), Nahua, and Xi’iuy (Pame) ethnic groups. The object of this study is to analyze, among the different cultural groups of the region, how the performances of the relevant Socioecological Systems (SESs) influence the conservation of biocultural diversity. Quantitative approaches are used to determine the expected trends of indices (Informant Consensus Factor, ICF; Cultural Importance Index, CII; Shannon–Wiener Biodiversity Index, SWI) commonly used in the ethnobotanical field. Data of the main domestic forest species used by the groups mentioned above were collected in 2021. We analyzed the SES profile for each of the ethnic groups and a mestizo group, as well as their relationship with the biome they mainly inhabit and the domestic functions fulfilled by the ethnobotanical species. As a result, we found that the low deciduous forest and the sub-evergreen tropical forest biomes, which co-evolved mainly with the Nahua and the Teenek SESs, present higher diversity and effective use of species so that offer better chances for conserving the landscape heritage of biocultural diversity. Otherwise, the results also show the critical nature regarding the biomes inhabited by the Pame and the mestizo’s SESs.

Assessing variation in the effectiveness of IUCN protected area categorisation. What remotely sensed forest integrity and human modification reveals across the major tropical forest biomes

• We focused on evaluating the efficacy of forested protected areas (PAs) across the three main tropical biomes- Congo Basin, Tropical Andes, insular Malaysia and Indonesia. • PA efficacy was evaluated on the basis of ecoregional representation, human modification and forest integrity. • Representation of key ecoregions varied with 7%, 11% and 22% of named ecoregions being unprotected within each major region. • IUCN management categories play a minor role in influencing PA efficacy. • PA size was an important determinant of PA efficacy. One of the major threats facing protected areas (PAs) in hyper-diverse tropical forest ecosystems is human modification of their natural habitats. With a focus on forested PAs situated across three of the world’s major tropical regions, the Congo Basin, insular Indonesia Malaysia and the Tropical Andes. We analyse their representation of identified ecoregions and remote sensing data of human modification and forest integrity levels within PAs and used a generalized linear modelling approach to estimate the influences on these pressures, with a particular focus on IUCN management categorisation, PA size, and geographic location. Representation of key ecoregions varied with 7%, 11% and 22% of named ecoregions being unprotected within each major region. Overall, the IUCN management category allocation played a minor role in influencing the modification and forest integrity observed within PAs. Instead, PA size was the most important determinant of these variables across the different regions under consideration. This work provides further evidence to suggest that the assignment of PAs to IUCN categories in their current form is not interpreted consistently across different regions and does not correspond to the conservation benefits expected to be conferred by this categorisation.

Cropland expansion, intensification, and reduction in Mato Grosso state, Brazil, between the crop years 2000/01 to 2017/18

Growing populations require increased food production through increasing yields and expanding land use. Thus, agricultural production has a dialectical relationship with natural resource conservation. South America has been the recent site of both intensification and areal expansion of crop production. The presented study investigates the dynamics of land use and land cover (LULC) in Mato Grosso state at two-year intervals for an 18-year period consisting of the 2000/01 and 2017/18 crop years. We used a stratified sampling approach and visual interpretation of satellite image time series data to obtain estimates of LULC extent and dynamics, including area of cropland expansion, intensification, and reduction. Cropland dynamics exhibited an overall increase in both extent and intensification. The cropland use area in Mato Grosso increased from 38,324 km2 (±5618 km2) in 2000/01 to 97,394 km2 (±9938 km2) in 2017/2018. For the Cerrado tropical woodland biome portion of Mato Grosso, the expansion of cropland areas was related to soy and corn prices. For the humid tropical forest biome of Amazonia, soy production and deforestation were found to not be directly correlated. The intensification in Mato Grosso was increased from 8142 km2 (±1.39%) in the period from 2008/09 to 2010/11, to 30,487 km2 (±2.56%) in the period from 2010/11 to 2012/13. Overall dynamics reflect public and private conservation policies, soy market, climate and technology factors that spur or inhibit increased production of commodity crops. The end result reflects Brazil's increasing role as a global commodity crop producer.

The Remote Emerging Disease Intelligence-NETwork.

Accurate prediction of zoonotic spillover events requires a detailed understanding of baseline pathogens circulating in differing global environments. By characterizing the diversity and determining the natural baseline of pathogens in a given biological system, any perturbations to this balance can be detected, leading to estimates of risk for emerging diseases. As epidemics and probability for pandemics increase, there is a fundamental need for building global collaborations to fill gaps in the surveillance effort, especially to build remote in-county capacity and standardize timely sample processing and data analysis. To this point, a new consortium, the Remote Emerging Disease Intelligence-NETwork (REDI-NET) has been established to enhance surveillance approaches and characterize natural pathogens in temperate, tropical forest, and tropical grassland biomes. The REDI-NET is envisioned to be a long-term, phased initiative. All phases will integrate accompanying training resources such as videos reflecting SOPs and Quick Reference Guides. Routine bio- and xenosurveillance will facilitate the characterization of ecological parameters, enhance the accuracy of vector species identification using artificial intelligence technology, and guide the establishment of epidemiological risk thresholds critical for mitigating disease outbreaks in a timely manner. A key deliverable of the REDI-NET is a custom-designed electronically merged (e-MERGE) data pipeline and alert dashboard that integrates remotely captured data with state-of-the-art metagenomic next-generation sequencing technology. This pipeline incorporates data generated from field and laboratory best practices, to furnish health decision-makers with a centralized, timely, and rigorous database to efficiently search interdisciplinary and heterogeneous data sources necessary to alert, prepare and mitigate health threats. The e-MERGE pipeline, once fully established, will be a flexible, scalable, and expandable tool for varied health applications. Program success will result in an operational framework that addresses resource gaps in pathogen surveillance and enhances health protection with broad global applicability. The objective of this manuscript is to introduce the REDI-NET framework to anticipated stakeholders engaged in metagenomics, epidemiological surveillance, and One Health with a focus on Phase 1.

A Pantropical Overview of Soils across Tropical Dry Forest Ecoregions

Pantropical variation in soils of the tropical dry forest (TDF) biome is enormously high but has been poorly characterized. To quantify variation in the global distribution of TDF soil physical and chemical properties in relation to climate and geology, we produced a synthesis using 7500 points of data with gridded fields representing lithologic, edaphic, and climatic characteristics. Our analyses reveal that 75 TDF ecoregions across five biogeographic domains (Afrotropical, Australasian, Indo-Malayan, Neotropical, and Oceanian) varied strongly with respect to parent material: sediment (57%), metamorphic (22%), volcanic (13%), and plutonic (7%). TDF ecoregions support remarkably high variability in soil suborders (32), with the Neotropical and Oceanian realms being especially diverse. As a whole, TDF soils trend strongly toward low fertility with strong variation across biogeographic domains. Similarly, the exhibited soil properties marked heterogeneity across biogeographic domains, with soil depth varying by an order of magnitude and total organic C, N, and P pools varying threefold. Organic C and N pool sizes were negatively correlated with mean annual temperature (MAT) and positively correlated with mean annual precipitation (MAP). By contrast, the distribution of soil P pools was positively influenced by both MAT and MAP and likely by soil geochemistry, due to high variations in soil parent material across the biogeographic domains. The results summarized here raise important questions as to how climate and parent material control soil biogeochemical processes in TDFs.

Investigating the response of leaf area index to droughts in southern African vegetation using observations and model simulations

Abstract. In many regions of the world, frequent and continual dry spells are exacerbating drought conditions, which have severe impacts on vegetation biomes. Vegetation in southern Africa is among the most affected by drought. Here, we assessed the spatiotemporal characteristics of meteorological drought in southern Africa using the standardized precipitation evapotranspiration index (SPEI) over a 30-year period (1982–2011). The severity and the effects of droughts on vegetation productiveness were examined at different drought timescales (1- to 24-month timescales). In this study, we characterized vegetation using the leaf area index (LAI) after evaluating its relationship with the normalized difference vegetation index (NDVI). Correlating the LAI with the SPEI, we found that the LAI responds strongly (r=0.6) to drought over the central and southeastern parts of the region, with weaker impacts (r<0.4) over parts of Madagascar, Angola, and the western parts of South Africa. Furthermore, the latitudinal distribution of LAI responses to drought indicates a similar temporal pattern but different magnitudes across timescales. The results of the study also showed that the seasonal response across different southern African biomes varies in magnitude and occurs mostly at shorter to intermediate timescales. The semi-desert biome strongly correlates (r=0.95) to drought as characterized by the SPEI at a 6-month timescale in the MAM (March–May; summer) season, while the tropical forest biome shows the weakest response (r=0.35) at a 6-month timescale in the DJF (December–February; hot and rainy) season. In addition, we found that the spatial pattern of change of LAI and SPEI are mostly similar during extremely dry and wet years, with the highest anomaly observed in the dry year of 1991, and we found different temporal variability in global and regional responses across different biomes. We also examined how well an ensemble of state-of-the-art dynamic global vegetation models (DGVMs) simulate the LAI and its response to drought. The spatial and seasonal response of the LAI to drought is mostly overestimated in the DGVM multimodel ensemble compared to the response calculated for the observation-based data. The correlation coefficient values for the multimodel ensemble are as high as 0.76 (annual) over South Africa and 0.98 in the MAM season over the temperate grassland biome. Furthermore, the DGVM model ensemble shows positive biases (3 months or longer) in the simulation of spatial distribution of drought timescales and overestimates the seasonal distribution timescales. The results of this study highlight the areas to target for further development of DGVMs and can be used to improve the models' capability in simulating the drought–vegetation relationship.

Phylogenomics and a revised tribal classification of subfamily Dipterocarpoideae (Dipterocarpaceae)

AbstractDipterocarpoideae, the largest subfamily in the Meranti family (Dipterocarpaceae) are an ecologically dominant group of trees throughout much of wet tropical Asia. Increasing anthropogenic pressures on this economically important tree family make it essential to resolve their complex evolutionary relationships and understand the distribution of genetic diversity throughout the family and distribution range. Dipterocarpaceae have been the focal group in a wide range of studies, owing to their economic value, importance in historical biogeography and key role in the evolution of the Asian tropical forest biome. Despite this, persistent taxonomic and evolutionary questions remain, ranging from questions on the geographic origin, sequence of dispersal and the identification of diagnostic characters to circumscribe proper evolutionary groups. Here we present a comprehensive phylogenomic hypothesis for Dipterocarpoideae, based on the analyses of plastome and nuclear cistron (NRC) data, and provide an in‐depth review on the validity of morphological characters underlying the new tribal classification proposed here for the subfamily. Phylogenomic relationships were inferred using maximum likelihood and Bayesian approaches. Estimates of origin and onset of diversification in major clades and lineages were reconstructed using plastome, nuclear and combined datasets. Results of the separate and combined genomic datasets partly corroborate elements of previous classification systems (with improved support at all levels for major clades) but provide strong support for revising the tribal classification of the subfamily into four main clades: Dipterocarpeae (Dipterocarpus), Dryobalanopseae (Dryobalanops), Shoreeae (Hopea,Neobalanocarpus,Parashorea, and all parts of a polyphyleticShorea) and Vaterieae (including all other presently accepted Dipterocarpoideae genera). Multi‐fossil‐dated divergence time estimation suggests Vaterieae first originated in the Late Cretaceous, followed by Dipterocarpeae, with subsequent rise of the Dryobalanopseae and Shoreeae in the Eocene. Diversification of all tribes commenced before the Early Miocene. Our results provide strong support for the position ofNeobalanocarpus heimii,Parashoreaand (sub‐)sections of the generaAnisoptera,Hopea,ShoreaandVatica. Hypotheses on the origin ofNeobalanocarpus heimiiby intergeneric hybridisation betweenAnthoshorea(maternally inherited) andHopea(paternally inherited) species were corroborated. Finally, our study provides support for future revisionary changes: (1) the elevation to generic rank of sections inShorea; and (2) revising the infrageneric classification ofHopeaas all (sub‐)sections were recovered as not monophyletic.

Bioeconomy for the Amazon: concepts, limits, and trends for a proper definition of the tropical forest biome

The term bioeconomy has emerged in the last years as an important element for the transition to low carbon economies. However, as a relatively new term, it still encompasses a myriad of meanings, not all of them adequate for the Amazon biome or for biodiversity conservation.This document combines literature review from different areas of social sciences as to forge a concept proposal specific for the Amazonian biome. Here, it is argued that the concept should be process-focused and able to sustain the social-biodiversity of the region, favouring the strengthening of economic trajectories that are linked with the standing forest and flowing rivers, aided by traditional communities’ ties with their surroundings. To that effect, by providing a space for development of certain economic practices, amazon cities can play a key role in developing better relationships between society and nature.

Defining Biologically Meaningful Biomes Through Floristic, Functional, and Phylogenetic Data

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.

Discovering the forest in plain sight: a pop-up Symposium focusing on seasonally dry tropical forests.

Discovering the forest in plain sight: a pop-up Symposium focusing on seasonally dry tropical forests.

Range Extension of Gauromydas mystaceus (Wiedemann, 1830) (Diptera, Mydidae) for the Maranhão State, Brazil and Cerrado Biome

The present study expands the distribution of Gauromydas mystaceus (Wiedemann, 1830) for the Maranhão state, northeastern Brazil in Cerrado biome. Previously, this species was only recorded in Brazil (Pará), French Guyana, Guyana and Surinam on Tropical Forest biome.

Annual changes in the Biodiversity Intactness Index in tropical and subtropical forest biomes, 2001–2012

Few biodiversity indicators are available that reflect the state of broad-sense biodiversity—rather than of particular taxa—at fine spatial and temporal resolution. One such indicator, the Biodiversity Intactness Index (BII), estimates how the average abundance of the native terrestrial species in a region compares with their abundances in the absence of pronounced human impacts. We produced annual maps of modelled BII at 30-arc-second resolution (roughly 1 km at the equator) across tropical and subtropical forested biomes, by combining annual data on land use, human population density and road networks, and statistical models of how these variables affect overall abundance and compositional similarity of plants, fungi, invertebrates and vertebrates. Across tropical and subtropical biomes, BII fell by an average of 1.9 percentage points between 2001 and 2012, with 81 countries seeing an average reduction and 43 an average increase; the extent of primary forest fell by 3.9% over the same period. We did not find strong relationships between changes in BII and countries’ rates of economic growth over the same period; however, limitations in mapping BII in plantation forests may hinder our ability to identify these relationships. This is the first time temporal change in BII has been estimated across such a large region.

Vulture Abundance and Habitat Association Following Major Hurricane Disturbance in the Tropical Dry Forest of Western Mexico

Scavenger birds are common species frequently associated with open habitats, but sympatric vulture species have differing natural history traits that may influence seasonal habitat relationships and responses to natural disturbances, such as hurricanes. We evaluated seasonality and habitat relationships of Black Vultures (Coragyps atratus) and Turkey Vultures (Cathartes aura) at sites within and outside the path of maximum winds of Hurricane Patricia in western Mexico. We used 1.5-km line transects to survey vultures during dry and rainy seasons in four habitats of the tropical dry forest biome over a 2-yr period after hurricane landfall. We measured habitat structure along each transect using the point-centered quarter method, and determined landscape composition within a 3000-ha circular plot centered around the midpoint of each transect. Vulture abundance was influenced by habitat structure variables of open areas, but at sites affected by hurricane disturbance vulture abundance was positively associated with increased cover of wetlands and agricultural land. Both species of vultures had low abundance in forests, and Black Vultures had significantly higher abundance in agricultural land and wetlands. Season significantly influenced vulture abundance by habitat: agricultural land and wetlands had higher vulture abundance in the rainy season, but forests had higher abundance in the dry season. Disturbance by a major hurricane induced species-specific changes in spatial-temporal abundance of vultures: the Black Vulture in particular had higher abundance in all habitats except wetlands during the dry season, and greater abundance in the first months after hurricane landfall. Hence, although vultures occur predominantly in open areas, they show species-specific habitat associations and responses to hurricane disturbance.

Cryptonanus agricolai (Didelphimorphia, Didelphidae) in the Atlantic Forest core: occurrence of a xeric associated species in a tropical forest biome

Cryptonanus agricolai (Didelphimorphia, Didelphidae) in the Atlantic Forest core: occurrence of a xeric associated species in a tropical forest biome

Detecting vulnerability of humid tropical forests to multiple stressors

Detecting vulnerability of humid tropical forests to multiple stressors

Global tropical dry forest extent and cover: A comparative study of bioclimatic definitions using two climatic data sets.

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 km2 of closed canopy (≥ 40% forest cover) tropical dry forest in 2000 and 4,369,695 km2 in 2020 with a gross loss of 561,719 km2 (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.