Tropical Landscapes Research Articles

Demography of the understory herb Heliconia acuminata (Heliconiaceae) in an experimentally fragmented tropical landscape.

Habitat fragmentation remains a major focus of research by ecologists decades after being put forward as a threat to the integrity of ecosystems. While studies have documented myriad biotic changes in fragmented landscapes, including the local extinction of species from fragments, the demographic mechanisms underlying these extinctions are rarely known. However, many of them-especially in lowland tropical forests-are thought to be driven by one of two mechanisms: (1) reduced recruitment in fragments resulting from changes in the diversity or abundance of pollinators and seed dispersers or (2) increased rates of individual mortality in fragments due to dramatically altered abiotic conditions, especially near fragment edges. Unfortunately, there have been few tests of these potential mechanisms due to the paucity of long-term and comprehensive demographic data collected in both forest fragments and continuous forest sites. Here we report 11 years (1998-2009) of demographic data from populations of the Amazonian understory herb Heliconia acuminata (LC Rich.) found at Brazil's Biological Dynamics of Forest Fragments Project (BDFFP). The data set comprises >66,000 plant × year records of 8586 plants, including 3464 seedlings established after the first census. Seven populations were in experimentally isolated fragments (one in each of four 1-ha fragments and one in each of three 10-ha fragments), with the remaining six populations in continuous forest. Each population was in a 50 × 100 m permanent plot, with the distance between plots ranging from 500 m to 60 km. The plants in each plot were censused annually, at which time we recorded, identified, marked, and measured new seedlings, identified any previously marked plants that died, and recorded the size of surviving individuals. Each plot was also surveyed four to five times during the flowering season to identify reproductive plants and record the number of inflorescences each produced. These data have been used to investigate topics ranging from the way fragmentation-related reductions in germination influence population dynamics to statistical methods for analyzing reproductive rates. This breadth of prior use reflects the value of these data to future researchers. In addition to analyses of plant responses to habitat fragmentation, these data can be used to address fundamental questions in plant demography and the evolutionary ecology of tropical plants and to develop and test demographic models and tools. Though we welcome opportunities to collaborate with interested users, there are no restrictions on the use of this data set. However, we do request that those using the data for teaching or research purposes inform us of how they are doing so and cite this paper and the data archive when appropriate. Any publication using the data must also include a BDFFP Technical Series Number in the Acknowledgments. Authors can request this series number upon the acceptance of their article by contacting the BDFFP's Scientific Coordinator or E. M. Bruna.

Amazonian secondary forests are greatly reducing fragmentation and edge exposure in old-growth forests

Restoration of tropical landscapes through the expansion of secondary forests is crucial for climate change mitigation and offers co-benefits for biodiversity. However, the strength of these benefits is influenced by the position of these secondary forests within the landscape. Recovery of both carbon stocks and biodiversity in secondary forests are enhanced by proximity to old-growth forests, and old-growth forests may benefit from secondary forests in return through buffering of edge effects and reduced fragmentation. However, to date there has been no biome-wide assessment of secondary forest location relative to old-growth forests. We mapped Amazonian secondary forests and explored their proximity to old-growth forests of different conditions. We then calculated the extent to which secondary forests buffer old-growth edge forest (<120 m from an edge) and the influence of secondary forests on fragmentation. In 2020, 41.2% of Amazonian secondary forest was directly adjacent to old-growth forest and 94.1% was within a fragment connected to old growth. However, adjacency and connectedness fell to 20.1% and 57.4% respectively when only considering extensive structurally intact old-growth forest. Secondary forests buffered 41.1% of old-growth edge forest and, when acting as corridors, reduced the total number of old-growth fragments by 2 million. Our results reveal the importance of understanding spatial context when examining the potential benefits of increasing secondary forest cover. Improved understanding of the benefits of locating secondary forests next to old-growth forests could support the development of more effective climate change mitigation and restoration strategies.

Emergent structure and dynamics of tropical forest-grassland landscapes

Previous work indicates that tropical forest can exist as an alternative stable state to savanna. Therefore, perturbation by climate change or human impact may lead to crossing of a tipping point beyond which there is rapid forest dieback that is not easily reversed. A hypothesized mechanism for such bistability is feedback between fire and vegetation, where fire spreads as a contagion process on grass patches. Theoretical models have largely implemented this mechanism implicitly, by assuming a threshold dependence of fire spread on flammable vegetation. Here, we show how the nonlinear dynamics and bistability emerge spontaneously, without assuming equations or thresholds for fire spread. We find that the forest geometry causes the nonlinearity that induces bistability. We demonstrate this in three steps. First, we model forest and fire as interacting contagion processes on grass patches, showing that spatial structure emerges due to two counteracting effects on the forest perimeter: forest expansion by dispersal and forest erosion by fires originating in adjacent grassland. Then, we derive a landscape-scale balance equation in which these two effects link forest geometry and dynamics: Forest expands proportionally to its perimeter, while it shrinks proportionally to its perimeter weighted by adjacent grassland area. Finally, we show that these perimeter quantities introduce nonlinearity in our balance equation and lead to bistability. Relying on the link between structure and dynamics, we propose a forest resilience indicator that could be used for targeted conservation or restoration.

Towards tree-based systems disturbance monitoring of tropical mosaic landscape using a time series ensemble learning approach

Tree clearing and degradation inside and outside forest ecosystems in Africa are important contributors to global carbon budget and emissions. Part of the uncertainties in emission estimates, among other things, is related to the non-inclusion of disturbances across all tree-based systems and limitations in the capacity of existing methodologies to detect subtle changes or degradation. Here, we present a tree-based system (TBS) disturbance monitoring approach in a mosaic landscape in East Africa. For this purpose, high- and low-intensity disturbance detection time series algorithms, namely Breaks for Additive Season and Trend monitor (BFASTmonitor), Continuous Degradation Detection (CODED), and Landsat-based detection of Trends in Disturbance and Recovery (LandTrendr), were used. These algorithms were tested in three approaches based on reference canopy cover change data from repeated airborne laser scanning. Data processing was performed using Collection 2 Landsat (5, 7, and 8) time series in Google Earth Engine. The approaches were based on testing the accuracy of 1) the algorithms' magnitude of change outputs using multispectral information (i.e., several vegetation indices and bands); 2) multispectral ensemble learning approach applied at each of the three algorithms; and 3) combining the multiple algorithms in an ensemble learning approach. Our results showed an improvement in the accuracy of detecting a TBS disturbance from approach 1 to 3. The best result (44% omission error and 31% commission error against reference airborne laser scanning data) was obtained when BFASTmonitor and CODED were combined in an ensemble learning approach. The shortwave infrared bands were more important for detecting TBS disturbance than green, red, and near-infrared bands. The application of the best model in TBS disturbance monitoring in the region revealed that disturbances were more dominant outside forest ecosystems than inside. Improved disturbance monitoring in TBS can contribute to more accurate emission estimates in Africa and elsewhere in the tropics.

Land cover and forest health indicator datasets for central India using very-high resolution satellite data

Satellite imagery has been used to provide global and regional estimates of forest cover. Despite increased availability and accessibility of satellite data, approaches for detecting forest degradation have been limited. We produce a very-high resolution 3-meter (m) land cover dataset and develop a normalized index, the Bare Ground Index (BGI), to detect and map exposed bare ground within forests at 90 m resolution in central India. Tree cover and bare ground was identified from Planet Labs Very High-Resolution satellite data using a Random Forest classifier, resulting in a thematic land cover map with 83.00% overall accuracy (95% confidence interval: 61.25%–90.29%). The BGI is a ratio of bare ground to tree cover and was derived by aggregating the land cover. Results from field data indicate that the BGI serves as a proxy for intensity of forest use although open areas occur naturally. The BGI is an indicator of forest health and a baseline to monitor future changes to a tropical dry forest landscape at an unprecedented spatial scale.

Drivers of field-saturated soil hydraulic conductivity: Implications for restoring degraded tropical landscapes

Water security represents a major challenge in East Africa, affecting the livelihoods of millions of people and hindering sustainable development. Predicted increases in rainfall intensity and variability are expected to exacerbate water insecurity and land degradation. Improving soil infiltrability is an effective strategy for addressing water insecurity and land degradation. Research on soil infiltrability is often highly localized; therefore, scientific understanding of the drivers of infiltrability on larger spatial scales is limited. The aim of this study was to understand the main drivers of infiltrability across five contrasting landscapes in Kenya. We measured field-saturated hydraulic conductivity (Kfs) in 257 plots and collected data for variables representing soil properties (sand content, soil organic carbon (SOC) and pH), land degradation (grazing pressure and presence of erosion), vegetation quantity (woody aboveground biomass), and vegetation quality (functional properties and diversity). We used generalized mixed-effects models to test for the effects of these variables on Kfs. Median Kfs for the five sites ranged between 23.8 and 101.8 mm h−1. We found that Kfs was positively associated with sand content (standardized effect 0.39), SOC content (0.15), and functional diversity of woody vegetation (0.09), while it had a negative relationship with the presence of erosion (−0.24) and grazing pressure (−0.09). Subsequently, we conclude that infiltrability can be enhanced through using land restoration strategies which specifically target parameters that affect Kfs. The results further support that Kfs is not solely dictated by inherent soil properties, and that management interventions which boost SOC, reduce erosion, and minimize unsustainable grazing can help address water scarcity by restoring soil hydrological function.

Soil toposequences, soil erosion, and ancient Maya land use adaptations to pedodiversity in the tropical karstic landscapes of southern Mexico

The soil mantle of the tropical karst landscapes of southern Mexico was a key resource for ancient Maya agriculture and experienced deep transformation due to long-term human impacts under changing environmental conditions. We conducted a comparative analysis of three compound soil toposequences in mountainous (Sierra de Chiapas/Middle Usumacinta Valley, Busiljá, and Chinikihá archaeological sites) and platform (NE Yucatán Peninsula, Yalahau region) karst landscapes to reconstruct general tendencies and regional variations in pedodiversity development and soil–human interactions since the Early Preclassic Period. Toposequence characterization is based on macro- and micromorphological observations, accompanied by a suite of laboratory data. Calcareous upland geoforms of all toposequences have similar soil combinations consisting of shallow Rendzina and deep red clayey Terra Rossa types of profiles. We argue that Rendzinas, now dominant in the upland soil cover, in most cases, are not a product of incipient pedogenesis on limestone; they have developed from the residues of Terra Rossa soils after their advanced erosion. Pedosediments generated by ancient soil erosion have been found in the piedmont and depression positions in the mountainous landscapes of Chiapas, as a result of lateral downslope soil removal, and in the subsurface karstic cavities in the platform of NE Yucatán, indicating vertical “soil piping.” The soils of the lowland domains show contrasting differences between the toposequences: gleyic clay–rich soils and humic alluvial soils prevail in Chinikihá and Busiljá, whereas hydromorphic carbonate soils have formed in Yalahau karstic depressions. These differences in the lowland soil properties led to divergent ancient Maya land use strategies; in Chinikihá and Busiljá, the major agricultural domain was developed in the lowlands, implying largescale artificial drainage. On the contrary, in Yalahau, mostly upland Rendzinas were cultivated, implying “precision agriculture” and “container gardening.”

On the hydro-geomorphology of steepland coffee farming: Runoff and surface erosion

Soil compaction and natural vegetation removal associated to agriculture tends to promote runoff and soil erosion with potentially adverse onsite, downstream, and global impacts. Although coffee farming represents a fraction of the world’s harvested lands, it is a vital crop for many developing nations where it is frequently cultivated on erosion prone, high-relief, wet tropical landscapes. However, limited empirical data exists on coffee farm erosion. This article attends this need by describing the results of rainfall simulation experiments designed to evaluate the impact of sun-grown coffee-farming on precipitation excess, soil infiltration rates, and surface erosion by overland flow. Results show that infiltration rates on coffee-cultivated fields are ∼60 – 80% relative to undisturbed forested slopes, and that cultivation increases erosion rates by one to two orders of magnitude depending on the presence or absence of mulch or weed cover. The magnitude of the impact suggests that erosion on coffee-cultivated land is unsustainable from both a soil formation and an agricultural productivity point of view. Unsurfaced access roads display an even greater impact than cultivated surfaces with infiltration rates ∼10% of undisturbed soils and erosion up to four-orders of magnitude above background depending on grading history and slope. Farm-scale annualized erosion is ∼3–24 Mg ha-1 yr-1 depending on actively used unpaved road abundance as roads account for ∼99% of net erosion. Implementing efficient erosion control strategies for coffee farms is therefore essential to reduce their current impacts, but also for the future given the worldwide surge in coffee harvesting areas projected for the upcoming decades.

The ecological functions of dung beetles are shaped by multiple dimensions of diversity

Abstract A mechanistic understanding of the relationship between multiple dimensions of species diversity and ecosystem functioning is needed to safeguard ecological processes critical to human well‐being. We evaluated how taxonomic, functional and phylogenetic diversities, as well as the assembly mechanisms of dung beetle communities, percent forest cover and landscape fragmentation, affect dung burial, soil excavation efficiency and dung fly larvae abundance in Los Tuxtlas Biosphere Reserve, a complex tropical landscape. Dung beetle functions were measured in 15 landscapes representing a gradient of forest cover loss (0%–100%). Phylogenetically clustered assemblages of large tunneler dung beetles showed the highest dung burial efficiency across the landscape. Fly larvae abundance was negatively correlated with the taxonomic diversity and functional evenness of dung beetles. Forest cover and landscape fragmentation did not significantly affect dung burial effectiveness, suggesting a high degree of functional redundancy. Dung burial efficacy is mainly driven by selection mechanisms, in which a single or a few phylogenetically close species disproportionately affect a given function. Fly larvae abundance was controlled by a complementary functional effect where each dung beetle species additively affected fly larvae survival. Hence, multiple functions are maintained by contrasting mechanisms and different diversity dimensions. High dung beetle species richness may foster pest fly control in tropical landscapes such as Los Tuxtlas Biosphere Reserve. Our findings highlight the need to assess multiple dimensions of diversity since each can operate concurrently and contrastingly on the different ecological functions of species assemblages.

The Effects of Anthropogenic Disturbances on the Spatiotemporal Patterns of Medium-Large Mammals in Tropical Volcanic Landscapes.

A comprehensive understanding of the consequences of human interactions with mammals is a critical factor in supporting and conserving species in landscapes dominated by humans, which are increasingly threatened. This study aimed to identify the spatial and temporal interactions between humans and mammals. A non-parametric statistical approach with kernel density was used to detect human-mammal temporal interactions. The species interaction factor (SIF) was applied to calculate the spatial overlap based on the two-species occupancy detection model. The activity patterns of medium mammals were nocturnal, diurnal, and cathemeral. The human-medium mammal pairs with SIF values that were <1 and statistically significant included the human-long-tailed macaque (Macaca fascicularis) pair, the human-leopard cat (Prionailurus bengalensis) pair, and the human-barking deer (Muntiacus muntjac) pair. Based on their SIF values and the high overlap in their activity times, the human-macaque pairings had a high risk of conflict. Barking deer and leopard cats displayed a coexistence with humans via time-sharing activities. Due to temporal niche variations with human activities, the existence of nocturnal mammals was relatively uninterrupted. This study showed that most mammals are able to adapt spatially and temporally to various human activities. Nonetheless, efforts to mitigate human-wildlife conflict must be maintained, particularly in the case of severely endangered species, such as the Sunda pangolin.

Epilithic biofilms provide large amounts of nitrogen to tropical mountain landscapes.

We show that epilithic biofilms are a relevant nitrogen (N) source in a rocky mountain range in Brazil. During different seasons, we quantified nitrate, ammonium, dissolved organic N (DON) and total dissolved N (TDN) leached by a simulated short rain event. We quantified the epilithic autotrophic biomass by taxonomic groups and its correlation with leached N. We hypothesized that leached N would be correlated to heterocystous cyanobacteria biomass since they are more efficient N2 fixers. We estimated a landscape N supply of 8.5 kg.ha-1 .year-1 considering the mean precipitation in the region. TDN in leachate was mainly composed of DON (83.8% ± 22%), followed by nitrate (12.1% ± 3%) and ammonium (5% ± 5%). The autotrophic epilithic community was mainly composed of non-heterocystous (Gloeocapsopsis) and heterocystous cyanobacteria (Scytonema and Stigonema), except for a site more commonly affected by fire events that showed a dominance of Chlorophyta. Biogeochemical upscaling was facilitated by the fact that N leaching was not different among sites or related to autotrophic epilithic biomass or assemblage composition. In conclusion, the capacity of epilithic biofilms to provide N to surrounding systems is an ecosystem service that underscores the necessity to conserve them and their habitats.

A comparison between time‐constrained counts and line transects as methods to estimate butterfly diversity and monitor populations in tropical habitats

Abstract Long‐term species monitoring programmes have revealed catastrophic declines in insect populations and disruption of biological communities that are contributing to biodiversity loss. Such discoveries have been possible because of standardised methods, such as line transects, of counting butterflies and other insects. However, line transects are not feasible in many tropical and mountainous habitats, so alternative methods must be explored. To tackle this issue, we devised time‐constrained (30‐min) counts and compared butterfly diversity estimated through timed counts and line transects in three tropical habitats in India (evergreen forest, dry deciduous forest and an urban woodland). We tested the relative performance of the two methods in sampling species richness and abundance, as well as numbers of rare, endemic and specialist butterflies. We observed greater overall species richness, and more species of habitat specialists and endemics per sample in time‐constrained counts in the evergreen forest, but not in the other two habitats. Thus, time‐constrained counts were relatively more efficient in detecting species in the species‐rich evergreen habitat. Apart from this difference, the two sampling methods captured similar levels of species richness and other measures of diversity. Our study thus shows that time‐constrained counts are a suitable if not a superior alternative to line transects to conduct butterfly diversity surveys and population monitoring in complex tropical landscapes. Due to methodological flexibility and simplicity, time‐constrained counts may be particularly useful to study the impacts of climate change, habitat fragmentation and land use practices on butterfly, Odonata and other insect populations in populous and tech‐ready tropical countries using citizen science frameworks.

Importing Arcadia into 18th‐century Madras: Poetics of the contact zone and the politics of genre in Eyles Irwin's Saint Thomas's Mount

AbstractEyles Irwin (1751–1817), an East India Company official who spent much of his life in the British settlement of Fort St. George, Madras, was one of the earliest practitioners of anglophone belles lettres in the Indian subcontinent, and his writings predate the development of a robust culture of English‐language literary composition in the colony by quite a few years. The scant scholarly attention he has received belies his importance as an anticipator of the momentous literary‐historical processes that would transform India's public sphere in the 19th century. This essay offers a contextual reading of Saint Thomas's Mount (1774), his earliest extant poem, which is avowedly modelled on canonical English topographical poems like Alexander Pope's Windsor‐Forest (1713) and makes use of a host of neoclassical conventions, but which also differs from them in terms of the kind of landscape that is represented (Irwin's is a tropical landscape, with abundant mangoes, palms, and Oriental fauna, unlike Pope's pleasant, idyllic British park). However, Irwin's target readership being chiefly metropolitan, he contends with the difficulty of highlighting India's irreducible foreignness while simultaneously trying to ensure that readers in London do not find the Oriental descriptions too alien, incredible, and unrelatable. The authorial strategies he adopts to navigate this difficulty constitute the focus of the first part of the essay. The second (and final) part seeks to shed light on his hybrid, hyphenated identity as an Indian‐born Irish poet, and on his perception of himself as somehow fundamentally unlike those Britons who never ventured beyond the geographical confines of Europe, let alone setting down roots in places on the very fringes of the British empire. The affiliative bonds he forges with expatriate colonial officials living in and confronting the hardships of life in the monsoonal tropics mark him as a member of the steadily growing community of Anglo‐Indians in the Indian subcontinent. While noting the shifting connotations of the term ‘Anglo‐Indian’ in the 18th and 19th centuries, this essay will also examine the implications of identifying Irwin as a member of this initially amorphous but steadily growing community.

Spatiotemporal dynamics reveals forest rejuvenation, fragmentation, and edge effects in an Atlantic Forest hotspot, the Pernambuco Endemism Center, northeastern Brazil.

Large forested tracts are increasingly rare in the tropics, where conservation managers are often presented with the challenge of preserving biodiversity in small and isolated fragments. The Atlantic Forest is one of the world's most important biodiversity hotspots, jeopardized by habitat loss and fragmentation. The Pernambuco Endemism Center (PEC) is the most degraded of the Atlantic Forest regions and because of the dramatic levels of deforestation, fragmentation, and ongoing species losses, studies on the distribution and configuration of the PEC's forest cover are necessary. However, across dynamic tropical landscapes, investigating changes over time is essential because it may reveal trends in forest quality attributes. Here, we used Google Earth Engine to assess land use and land cover data from MapBiomas ranging from 1985 to 2020 to calculate current landscape metrics and to reveal for the first time the spatiotemporal dynamics of the PEC's forests. We identified a forest cover area that ranged from 571,661 ha in 1985 to 539,877 ha in 2020, and about 90% of the fragments were smaller than 10 ha. The average fragment size was about 11 ha, and only four fragments had more than 5,000 ha. Deforestation was mostly concentrated in northern Alagoas, southern Pernambuco, and non-coastal Paraíba and Rio Grande do Norte. On average, borders represented 53.6% of the forests from 1985 to 2020, and younger forests covered 52.3% of the area in 2017, revealing a vegetation rejuvenation process 2.5 times higher than in total Atlantic Forest. In 2017, older forest cores in fragments larger than 1000 ha (i.e., higher-quality habitats) represented only 12% of the remaining forests. We recommend that the amount of forest cover alone may poorly assist conservation managers, and our results indicate that ensuring legal protection and increasing surveillance of the PEC's few last higher-quality habitats is urgently needed.

Land use diversification may mitigate on-site land use impacts on mammal populations and assemblages.

Land use is a major cause of biodiversity decline worldwide. Agricultural and forestry diversification measures, such as the inclusion of natural elements or diversified crop types, may reduce impacts on biodiversity. However, the extent to which such measures may compensate for the negative impacts of land use remains unknown. To fill that gap, we synthesised data from 99 studies that recorded mammal populations or assemblages in natural reference sites and in cropland and forest plantations, with or without diversification measures. We quantified the responses to diversification measures based on individual species abundance, species richness and assemblage intactness as quantified by the mean species abundance indicator. In cropland with natural elements, mammal species abundance and richness were, on average, similar to natural conditions, while in cropland without natural elements they were reduced by 28% and 34%, respectively. We found that mammal species richness was comparable between diversified forest plantations and natural reference sites, and 32% lower in plantations without natural elements. In both cropland and plantations, assemblage intactness was reduced compared with natural reference conditions, but the reduction was smaller if diversification measures were in place. In addition, we found that responses to land use were modified by species traits and environmental context. While habitat specialist populations were reduced in cropland without diversification and in forest plantations, habitat generalists benefited. Furthermore, assemblages were impacted more by land use in tropical regions and landscapes containing a larger share of (semi)natural habitat compared with temperate regions and more converted landscapes. Given that mammal assemblage intactness is reduced also when diversification measures are in place, special attention should be directed to species that suffer from land use impacts. That said, our results suggest potential for reconciling land use and mammal conservation, provided that the diversification measures do not compromise yield.

Racial Disparities in Puerto Rican Law-Making as a Result of the Americanized Census

The island of Puerto Rico is characterized not only by its tropical landscapes but also by its extensive history of “mestizaje” and welcoming nature, regardless of race and ethnicity. However, the apparent lack of racial prejudice in its culture is contradicted by the recent increase in racial inequality throughout the island's municipalities. Such racial and ethnic inequalities in Puerto Rico result from the lack of government institutions, tools, and models specifically designed for the island's complex national identity. In particular, implementing the census and its Americanized view on race has further increased inequality among racial minorities in Puerto Rico. Despite the U.S. government's attempts to broaden the census' scope of racial understanding, many of the island's inhabitants remain disadvantaged and unacknowledged by a system that cannot accurately identify their needs, perpetuating the cycle of governmental inaction through inaccurate data regarding Puerto Rican's racial composition.

Anthropogenic disturbance modifies tree functional traits in the only remnant swamp forest of Bangladesh

The relationship between ecosystem functions and plant functional traits has been well documented and is considered to be one of the most vital topics in ecology. However, the correlation between anthropogenic disturbance and tree functional trait diversity remains largely unclear. The present study investigates the role of anthropogenic disturbance on selected tree functional traits in Ratargul Swamp Forest (RSF) – the only remnant tropical freshwater swamp forest ecosystem in Bangladesh. We established 50 plots and collected six plant traits, i.e., tree height, specific leaf area (SLA), wood density (WD), leaf dry matter content (LDMC), seed mass, and bark thickness. A two-way analysis of variance (ANOVA) was carried out to test the interaction between plant functional traits and anthropogenic disturbance in RSF. Our study found that anthropogenic disturbance has a significant (p&amp;lt; 0.05) influence on deciduous swamp forest tree species’ functional traits but none on evergreen tree species’ functional traits. For deciduous trees, disturbance has a significant positive effect on CWM.SLA (p&amp;lt; 0.05) and CWM.Height (p&amp;lt; 0.05) and a negative impact on CWM.Bark-thickness and CWM.Seed-mass (p&amp;lt; 0.05). There were no significant effects of disturbance on CWM.WD and CWM.LDMC. We believe the present study will contribute toward improving our understanding of the effect of disturbances on tree functional trait diversity in tropical human-dominated landscapes where anthropogenic pressure is increasing at an unprecedented rate. It will also function as an essential conservation for related decision-making of Ratargul Swamp Forest in northeastern Bangladesh and elsewhere in the tropics with a similar context.

Habitat modification destabilizes spatial associations and persistence of Neotropical carnivores

Spatial relationships between sympatric species underpin biotic interactions, structure ecological communities, and maintain ecosystem health. However, the resilience of interspecific spatial associations to human habitat modification remains largely unknown, particularly in tropical regions where anthropogenic impacts are often greatest. We applied multi-state multi-species occurrence models to camera trap data across nine tropical landscapes in Colombia to understand how prominent threats to forest ecosystems influence Neotropical carnivore occurrence and interspecific spatial associations, with implications for biotic interactions. We show that carnivore occurrence represents a delicate balance between local environmental conditions and interspecific interactions that can be compromised in areas of extensive habitat modification. The stability of carnivore spatial associations depends on forest cover to mediate antagonistic encounters with apex predators and structurally intact forests to facilitate coexistence between competing mesocarnivores. Notably, we demonstrate that jaguars play an irreplaceable role in spatially structuring mesocarnivore communities, providing novel evidence on their role as keystone species. With increasing global change, conserving both the extent and quality of tropical forests is imperative to support carnivores and preserve the spatial associations that underpin ecosystem stability and resilience.

Urban forests support natural regeneration of cloud forest trees and shrubs, albeit with limited occurrence of late-successional species

In highly diverse tropical landscapes, urban and peri-urban forests can play a crucial role as reservoirs of biodiversity. However, urbanization has negatively impacted the natural and anthropogenic vegetation, including the composition, diversity, and functions of urban forests. Tree regeneration plays an essential role in the long-term functionality of forests. Few studies have investigated how natural regeneration occurs in urbanized tropical landscapes, as well as the factors that drive this process. We assessed whether natural regeneration of the tropical montane cloud forest is occurring in urban and peri-urban forests and examined the influence of environmental factors (elevation, annual precipitation, air temperature, canopy cover, and soil physicochemical characteristics) on the regeneration. We used the density and diversity of seedlings, saplings, and juveniles of trees and shrubs in 42 plots across seven urban and peri-urban sites in the Neotropical city of Xalapa, Mexico. In the natural regeneration, 42 tree and 22 shrub species were recorded. Of these species, 83% were native and 17% were non-native. There was a lower abundance of tree (34%) compared to shrub (66%) individuals. Early-successional species were more abundant (51%) than intermediate (35%) and late-successional (14%) species. The numbers of species in the seedling, sapling, and juvenile stages, and the number of early-successional species, were higher in urban than in peri-urban forests. The species richness of both native and non-native taxa was higher in urban than in peri-urban forests (95% CI). We found no significant differences in the density of the young life stages, the density of successional groups, or the density of native and non-native species, between urban and peri-urban forests, probably due to high variability across the sites. Canopy cover had a consistently positive effect on density in most groups. Forest type, soil phosphorus, and soil bulk density also explained densities, except for the late-successional species, where these factors were not statistically significant. The limited richness and density of late-successional species highlight the need to assist the regeneration of this vulnerable group. Understanding natural regeneration patterns can inform the management and restoration of urbanized areas in the distributional regions of tropical montane cloud forest, one of the most important and threatened tropical ecosystems.

Effects of historical land use and recovery pathways on composition, structure, ecological function, and ecosystem services in a Caribbean secondary forest

Regenerated secondary forests in the tropics are resilient ecosystems. Differences in land-use history and disturbance, abiotic and biotic site conditions, and successional pathways can influence secondary forest biodiversity, structure, ecological functions, and ecosystem services. However, studies assessing the supply of ecosystem services of secondary forests are limited. We examined trees in plots located across late successional stage secondary forest in the Luquillo Experimental Forest, Puerto Rico with three combinations of historical canopy cover (circa 1936) and post-agricultural recovery pathways: (1) > 50% canopy cover and passive regeneration (>50 P), (2) < 50% canopy cover and passive regeneration (<50 P), and (3) < 50% canopy cover and assisted + passive regeneration (<50 A+P). Using i-Tree Eco methodology, we investigated if differences in historical cover and passive vs assisted natural regeneration resulted in differences in composition and structure, hydrological functions, and estimated regulating ecosystem services, and compared the results between native and non-native species. The <50 P plots had greater species richness than the >50 P and <50 A+P plots, while the <50 A+P plots had significantly greater DBH, height, basal area, aboveground biomass, and estimated quantities of evaporation and transpiration, carbon storage, and removal of airborne contaminants compared to the other recovery pathways. Differences among plot groups can be attributed to historical management actions in concert with successional trajectories characteristic of novel secondary forests. Native species dominated throughout these secondary forests and cumulatively exhibited services that were 1.3 to 3.5 times greater than those of non-native species. However, non-native trees contributed disproportionally to basal area and aboveground biomass, and thus to some ecosystem services. Both natives and non-natives exhibited service provision that varied significantly with diameter size class and service type, and large trees were observed to be dominant service providers irrespective of species origin. Our study marks the first landscape-scale quantitative assessment of forest composition, structure and ecological functioning that is explicitly linked to exploring regulating ecosystem services within the montane secondary forest in Puerto Rico and expands representation of this research from the Caribbean. The findings underscore the role of historical land use and recovery pathways in driving services of tropical forests and show how ecosystem functions can vary in accordance with dynamic structural attributes of individual trees. This research can provide a useful point of comparison for analysis of biomass accumulation, ecosystem service provision, and evaluating service tradeoffs associated with forest structure in other recovering and old-growth tropical landscapes.