Find research datasets worth reusing

Dependence of tropical cyclone weakening rate in response to an imposed moderate environmental vertical wind shear on the warm-core strength and height of the initial vortex

This study investigated the dependence of the early tropical cyclone (TC) weakening rate in response to an imposed moderate environmental vertical wind shear (VWS) on the warm-core strength and height of the TC vortex using idealized numerical simulations. Results show that the weakening of the warm core by upper-level ventilation is the primary factor leading to the early TC weakening in response to an imposed environmental VWS. The upper-level ventilation is dominated by eddy radial advection of the warm-core air. The TC weakening rate is roughly proportional to the warm-core strength and height of the initial TC vortex. The boundary-layer ventilation shows no relationship with the early weakening rate of the TC in response to an imposed moderate VWS. The findings suggest that some previous diverse results regarding the TC weakening in environmental VWS could be partly due to the different warm-core strengths and heights of the initial TC vortex.

Data from: Nitrogen niche partitioning between tropical legumes and grasses conditionally weakens under elevated CO2

Plant community biodiversity can be maintained, at least partially, by shifts in species interactions between facilitation and competition for resources as environmental conditions change. These interactions also drive ecosystem functioning, including productivity, and can promote over-yielding- an ecosystem service prioritized in agro-ecosystems, such as pastures, that occurs when multiple species together are more productive than the component species alone. Importantly, species interactions that can result in over-yielding may shift in response to rising CO2 concentrations and changes in resource availability, and the consequences these shifts have on production is uncertain especially in the context of tropical mixed-species grasslands. We examined the relative performance of two species pairs of tropical pasture grasses and legumes growing in monoculture and mixtures in a glasshouse experiment manipulating CO2. We investigated how over-yielding can arise from nitrogen (N) niche partitioning and biotic facilitation using stable isotopes to differentiate soil N from biological N fixation (BNF) within N acquisition into aboveground biomass for these two-species mixtures. We found that N niche partitioning in species-level use of soil N vs. BNF drove species interactions in mixtures. Importantly partitioning and overyielding were generally reduced under elevated CO2. However, this finding was mixture-dependent based on biomass of dominant species in mixtures and the strength of selection effects for the dominant species. This study demonstrates that rising atmospheric CO2 may alter niche partitioning between co-occurring species, with negative implications for the over-yielding benefits predicted for legume-grass mixtures in working landscapes with tropical species. Furthermore, these changes in inter-species interactions may have consequences for grassland composition that are not yet considered in larger-scale projections for impacts of climate change and species distributions.

Data for: Shifts in grasses diversity patterns between two contrasting 40-year climate periods in tropical dry islands

Grasses are one of the most successful and dispersed plant families worldwide and their environmental and economic values are widely acknowledged. They dominate the landscape of Cabo Verde, the southernmost and driest archipelago of Macaronesia, and are relevant natural resources for local populations, but a comprehensive evaluation of their distribution patterns is still lacking. In this study, we aim to evaluate the potential effects of climate changes using the long-term data concerning grass distribution in Cabo Verde and the widely recognized climatic variability of this archipelago, which entails a huge irregularity in spatial and temporal rainfall. We identified two contrasting climatic periods (wet, from 1929 to 1968, and dry, from 1969 to 2007) and gathered all the information available from the bibliography, herbaria and fieldwork concerning spontaneous grass species recorded in Cabo Verde during those two periods, which amounted to 107 taxa. This information was then used to disclose the patterns of grass diversity as related to climatic and topographic variables (altitude and windward vs leeward aspects). Different altitudinal shifts in the distribution patterns of grass species assemblages and an assemblage specific to the wet period were revealed by comparing the two climatic periods. The role of exposure in delimiting the altitudinal distribution of the various assemblages was highlighted; the trade winds clearly determine the distribution of grass assemblages. We detected shifts in the distribution of grass assemblages according to the climatic periods (related to the macroclimate) and local topographic factors (associated with mesoclimates). Also, functional traits (i.e., annuals vs. perennials, C3 vs. C4 grasses, and tropical vs. temperate species) were found to vary between wet and dry periods, as well as with altitude and with slope aspect. Understanding species distributions and the role of the climatic variability of Cabo Verde is crucial to predict how climate change will affect them and thus to support effective management and conservation actions.

opencc-by-4.0Dec 2021View details →

Tropical forest seedling census data from Danum Valley, Sabah, Malaysia (2019-2021)

Data Link This is a link to a dataset affiliated with SEARRP but that is stored in a different repository. Please find the link to the dataset below, and be sure to cite the data correctly via that repository. Correct Citation Burslem, D.F.R.P.; Banin, L.F.; Bartholomew, D.C.; Bin Suis, M.A.F.; Bittencourt, P.R.L.; Chapman, D.; Dent, D.H.; Hayward, R.M.; O’Brien, M.J.; Rowland, L.M. (2022). Tropical forest seedling census data from Danum Valley, Sabah, Malaysia, 2019-2021. NERC EDS Environmental Information Data Centre. (Dataset). https://doi.org/10.5285/c1813d0d-193f-4f23-82c6-333d5d099b42 Abstract Southeast Asian tropical forests have been subjected to recent intense pressure due to selective logging and widespread clearance for Oil Palm cultivation. Consequently there is an emerging interest in restoring degraded forests using either natural regeneration or active restoration treatments. However, the reproductive biology of Southeast Asian tropical forest trees limits research on the effectiveness of these approaches, because most large canopy trees only flower and fruit very rarely. These sporadic mass reproductive events are responsible for establishing new cohorts of seedlings that grow up to become the next generation of adult canopy trees, and it is critical to discover whether the success of these episodic attempts at regeneration is as great in forests that have been degraded by logging as they are in primary forests, and whether the processes leading to seedling recruitment are restored effectively in forests where treatments such as tree planting and climber cutting have been applied. However, because these regeneration events occur so infrequently and unpredictably it is very difficult to incorporate them into the conventional planning cycle for research, despite the critical importance of the events that occur early in the life cycle of trees to future forests. In this project we will rapidly establish sampling sites in Sabah, Malaysia, where we know that a mass flowering of canopy trees was initiated in May 2019, for the first time since 2010. We aim to compare the amount and diversity of fruits and seedlings produced during this masting event in primary (undisturbed, unlogged) forests, and in adjacent forests that have been logged and either left to regenerate naturally or restored by planting tree seedlings and maintaining them for five years by climber cutting. Because the restoration of logged forests began more than 20 years ago, the original cohort of planted seedlings are now, in some cases, large canopy trees that may contribute seeds and seedlings for the first time during the reproductive event this year. We will also measure the expression of traits that determine how plants capture and use resources such as light and nutrients for the most common species that occur in each of the three types of forest, which will determine whether the community of seedlings that establish in the restored forests functions in a more similar way to that in the undisturbed primary forest than in the forests left to regenerate naturally after logging. A key focus on this study will be on species of the dominant family of canopy and emergent trees, the Dipterocarpaceae, which are targeted for logging. Logged forests possess a lower density of large reproductively mature dipterocarp individuals, and a key aim of restoration is to re-establish the dominance and diversity of this family by planting and maintaining dipterocarp seedlings. Dipterocarps possess an unusual trait for the tree flora of tropical forests, which is that they form mutualistic associations with root-colonising ectomycorrhizal fungi (ECM), whereas most other species in the forest form a different type of root association with arbuscular mycorrhizas (AM). Our recent research has shown that ECM seedlings benefit from proximity to a high density of ECM adults, possibly because they exchange resources through a common below-ground fungal network and because ECM species suppress root pathogens. In contrast, AM seedlings have lower survival when located close to a high density of adults of the same species. A final aim of our project is to test whether the beneficial effects of high adult density for ECM species is reduced in logged forests where the density of ECM adults is much lower, and whether these effects are offset by restoration. This research will therefore contribute results that are vital to understanding how Southeast Asian forests regenerate during masting events, and whether the negative effects of logging can be mitigated by restoration. Link to project website: <a href="https://gtr.ukri.org/projects?ref=NE%2FT006560%2F1">GtR (ukri.org)</a> Link to data repository: <a href="https://doi.org/10.5285/c1813d0d-193f-4f23-82c6-333d5d099b42" target="_blank" rel="noopener">DOI</a>

Systematic review of field research reveals critical shortfalls for restoration of tropical grassy biomes

Scientists and policymakers are becoming aware of the pressing need to restore tropical grassy biomes (TGB), which are home to unique biodiversity and provide essential ecosystem services to hundreds of millions of people. However, TGB face increasing threats, including the forest- and tree-centric approaches that promote their degradation though we still lack a systematic assessment of where and how TGB restoration research has been done to guide policy and practice. We synthesised knowledge on field restoration experiments by conducting a systematic literature review to map TGB restoration field studies, examine the association of restoration techniques and degradations sources, and investigate the diversity of indicators used to monitor restoration outcomes. TGB restoration was concentrated in Brazilian and Australian savannas, with large blindspots in Asia, Africa, and northern and western South America. Studies were largely context-dependent, with an inconsistent usage of restoration techniques to different sources of degradation. Less than half of the indicators evaluated were monitored consistently through time, often using a low-dimensional approach related to ecosystem functioning. Few studies manipulated fire, herbivores, and soils, the key drivers for the re-establishment of TGB dynamics. Unfortunately, many studies lacked negative (degraded ecosystems), positive (reference ecosystems) controls, or both, impairing attempts to robustly determine restoration outcomes. Our overview of field research on TGB restoration highlights that research needs improvement to refine our ability to assess, plan, implement, and monitor restoration. Severe issues with experimental designs and data reporting are identified as barriers to finding generality and upscale TGB restoration to meet the goals of the UN Decade on Ecosystem Restoration. Synthesis and implications: Our synthesis calls for enhanced field experiments, transparent data reporting, and quantitative syntheses to guide large-scale TGB restoration. The overall lack of knowledge on improving resilience and measuring outcomes hampers meaningful comparisons between studies and hinders synthetic views essential for determining appropriate restoration techniques for different degradation sources and suitable monitoring indicators. To overcome the scarcity of reliable and transparent data supporting TGB restoration, we propose a simple checklist for minimum research reporting information and a more complete multilingual standardized guideline.

opencc-by-4.0Mar 2024View details →

Additional files for 'spatial scales of tropical isotope change' project

Additional files for tropical-d18O-scales repository on github. Associated code and other files are associated with DOI: 10.5281/zenodo.11053701.

Data from: Advancing transdisciplinary research on grassy biomes to support resilience in tropical ecosystems and livelihoods

Madagascar-wide metadata relating to Malagasy Grassy Biomes. The understanding of vegetation dynamics in tropical grassy biomes is severely limited across spatio-temporal scales, limiting effective management and support for livelihoods and biodiversity. Despite their extent, utility, and central importance to people and ecosystem function, grassy biomes are often uncritically regarded as degraded, valueless landscapes that result primarily from destructive anthropogenic forces. Moreover, this characterization is often presented without investigation of their history, biodiversity, or ecological complexity. Iconically, Madagascar's grassy biomes cover approximately 80% of the island's land surface today and exemplify core challenges to understanding tropical grassy ecosystems and their interactions with anthropogenic activities across spatio-temporal scales. Intersections between human history and environmental change have sparked debates about the role of land use in shaping grassy biomes (e.g., pastoralism, cultivation, fire use), echoing land use debates globally, and highlighting obstacles to ecosystem and livelihood resilience. Like many tropical biodiversity hotspots, Madagascar faces converging challenges that can be aided by an improved understanding of grassy ecosystems and the livelihoods they support, including food and health insecurity, economic inequities, biodiversity loss, climate change, land conversion, and limited resource access. Centered on improved understanding and management of grassy biomes, we present a framework to guide transdisciplinary research across the tropics by: (1) establishing a common terminology; (2) summarising data contributions and knowledge gaps that reflect those in other tropical regions; (3) identifying priority research questions; and (4) highlighting transdisciplinary and inclusive approaches to resolve knowledge gaps and co-benefit ecosystems and livelihoods.

Variation in functional composition of reef fishes along a tropical to temperate gradient

Aims Transformations of species and functional compositions on subtropical reefs are ongoing due to poleward range shifts of some tropical species, with largely unknown consequences to ecosystem functioning. Trait-based approaches are powerful tools to quantify such changes. Here, we evaluated changes in the trait composition of coral-associated fish communities along a tropical to a temperate environmental gradient of ca.1400 km in southern Japan with abundance-weighted trait expression to assess how trait complexity changes with increasing latitude. Location Ryukyu Islands and southern Pacific coast of Japan Taxon Reef fish Methods We tested for shifts in trait space and functional redundancy, based on five morphological, life history, and behavioural traits: maximum length, pelagic larval duration, trophic level, substrate preference, and reproductive mode. Our trait database was coded with two approaches, first, by attributing a single value to each trait per species, and second, by fuzzy coding that allows more than one value per trait and hence considers some intraspecific trait variation. Results We found a reduction in specialist habitat traits (coral substrate preference, nesters, herbivores) and an increase in generalist traits (predators) with increasing latitude, along with a contraction in trait space from tropical to temperate reefs. Functional redundancy declined with increasing latitude. These trends were closely linked with latitudinal gradients in temperature, along with changes in other environmental factors such as turbidity and photosynthetically active radiation. Main Conclusion Functional turnover and contractions are thus likely due to the marginal conditions for coral-associated fishes at higher latitudes, favouring generalist species, whereas increased resources at lower latitudes favour high redundancy and niche partitioning. Accounting for intraspecific trait variation indicated the same trends but highlighted increased functional vulnerability across all sites. We show that trait complexity in coral-associated fish communities decreases from tropical to temperate reefs, highlighting the reduced functional scope that comes with marginal environmental conditions.

opencc-by-4.0Dec 2021View details →

Tropical forest seedling trait data collected in Danum Valley, Sabah, Malaysia, in February 2020

Leech-derived iDNA complements traditional surveying methods, enhancing species detections for rapid biodiversity sampling in the tropics

Deforestation, exploitation, and other drivers of biodiversity loss in Madagascar leave its highly endangered and predominantly endemic wildlife at risk of extinction. Decreasing biodiversity threatens to compromise ecosystem functions and vital services provided to people. New, economical, and diverse methods of biodiversity monitoring can help to establish reliable baseline and long-term records of species richness. Metabarcoding with invertebrate-derived DNA (iDNA) has emerged as a promising new biosurveillance tool. An unexpected wet forest fragment tucked in the dry cliffs of Madagascar's southcentral plateau, the Ivohibory Protected Area (IPA), hosts a unique mosaic of species diversity, featuring both dry and wet forest species. Recently elevated to protected status, the IPA has been surveyed for flora and fauna with a range of inventory methods over three years and six expeditions (2016, 2017, & 2019). We collected 1,451 leeches over 12 days from the IPA to supplement known species richness and to compare results against current records. With iDNA, we pooled tissues, and isolated, and amplified bloodmeal DNA with five sets of primers. We detected 20 species of which four are species of frogs previously undetected and three of which are previously unknown to exist in this region. iDNA surveys can provide complementary data to traditional surveying methods like camera traps, line transects, and bioacoustic methods.

Empirical data and model simulations of the effect of repeated hurricanes on soil carbon dynamics in a humid tropical forest

Increasing hurricane frequency and intensity with climate change is likely to affect soil organic carbon (C) stocks in tropical forests. We examined the cycling of C between soil pools and with depth at the Luquillo Experimental Forest in Puerto Rico in soils over a 30-year period that spanned repeated hurricanes. We used a non-linear matrix model of soil C pools and fluxes ("soilR") and constrained the parameters with soil and litter survey data. Soil chemistry and stable and radiocarbon isotopes were measured from three soil depths across a topographic gradient in 1988 and 2018. Our results suggest that pulses and subsequent reduction of inputs caused by severe hurricanes in 1989, 1998, and two in 2017 led to faster mean transit times and younger mean ages of soil C in the particulate, occluded, and mineral-associated soil organic matter pools at 0–10 cm and 35–60 cm depths relative to a modeled control soil with constant inputs over the thirty years. Between 1988 and 2018, the occluded C stock increased, and d13C in all pools decreased, while changes in particulate and mineral-associated C were undetectable. The differences between 1988 and 2018 suggest that hurricane disturbance results in a dilution of the occluded light C pool with an influx of young, debris-deposited C, and possible microbial scavenging of old and young C in the particulate and mineral-associated pools. These effects led to a younger total soil C pool with faster mean transit times. Our results suggest that increasing frequency of intense hurricanes will speed up rates of C cycling in tropical forests, and eventually lead to net losses of C from tropical forest soils.

opencc-zeroDec 2023View details →

Evolutionary history and environmental variability structure contemporary tropical vertebrate communities

Tropical regions harbor over half of the world's mammals and birds, but how their communities have assembled over evolutionary timescales remains unclear. To compare eco-evolutionary assembly processes between tropical mammals and birds, we tested how hypotheses concerning niche conservatism, environmental stability, environmental heterogeneity, and time-for-speciation relate to tropical vertebrate community phylogenetic and functional structure. We used in-situ observations of species identified from systematic camera trap sampling as realized communities from 15 protected tropical rainforests in four tropical regions worldwide. We quantified standardized phylogenetic and functional structure for each community and estimated the multi-trait phylogenetic signal (PS) in ecological strategies for the four regional species pools of mammals and birds. Using linear regression models, we test three non-mutually exclusive hypotheses by comparing the relative importance of colonization time, paleo-environmental changes in temperature and land cover since 3.3 Mya, contemporary seasonality in temperature and productivity, and environmental heterogeneity for predicting community phylogenetic and functional structure. The phylogenetic and functional structure showed non-significant yet varying tendencies toward clustering or dispersion in all communities. Mammals had stronger multi-trait PS in ecological strategies than birds (mean PS: mammal = 0.62, bird = 0.43). Distinct dominant processes were identified for mammal and bird communities. For mammals, colonization time and elevation range significantly predicted phylogenetic clustering and functional dispersion tendencies, respectively. For birds, elevation range and contemporary temperature seasonality significantly predicted phylogenetic and functional clustering tendencies, respectively, while habitat diversity significantly predicted functional dispersion tendencies. Our results reveal different eco-evolutionary assembly processes structuring contemporary tropical mammal and bird communities over evolutionary timescales that have shaped tropical diversity. Our study identified marked differences among taxonomic groups in the relative importance of historical colonization and sensitivity to environmental change.

opencc-zeroApr 2024View details →

Data from: Land-use intensity and relatedness to native plants promote exotic plant invasion in a tropical biodiversity hotspot

Exotic plant invasions threaten biodiversity and are costly to farmers. Land use is a major pathway promoting the spread of exotic plant species; however, little is known about the processes underlying the success of exotic plants in tropical agricultural landscapes. Focussing on the heterogeneous smallholder landscapes of north-eastern Madagascar, we studied exotic plants of understorey communities across a land-use intensity gradient from unburned lands (old-growth forests, forest fragments, and forest-derived vanilla agroforests) to burned ones (fallow-derived vanilla agroforests, woody fallows, and herbaceous fallows). We quantified the absolute species richness, abundance, and cover of exotic plants across land-use types and their proportional contribution to community richness, abundance, and cover as indicators of exotic plant invasion. We tested for the effects of land-use parameters, namely land-use history, canopy closure, and landscape-level forest cover, on exotic plants. Additionally, we tested whether the phylogenetic relatedness between exotic and native species in the same plot affected invasion success, testing Darwin's naturalization and pre-adaptation hypotheses. All indicators of exotic plant invasion were lowest in old-growth forests and forest fragments and highest in fallow-derived vanilla agroforests, woody fallows, and herbaceous fallows. Absolute and proportional exotic richness was negatively affected by canopy closure, and landscapes with high forest cover had lower proportions of exotic plant richness. High phylogenetic relatedness between exotics and natives was associated with lower proportional richness but higher proportions of exotics in abundance and cover. However, individual exotic species showed contrasting responses to land-use parameters and relatedness to natives. Synthesis and applications: Our results indicate that maintaining unburned lands, land-use types with dense canopies, and landscapes with high forest cover prevents the spread of exotic plants within agricultural landscapes of north-eastern Madagascar. Supporting Darwin's pre-adaptation hypothesis, exotic plants phylogenetically closely related to native plants are more likely to become successful invaders in terms of abundance and cover. Nevertheless, individual species show different responses to land-use changes and phylogenetic relatedness. Therefore, land-use decisions and management choices can be tailored to limit the spread of exotic species and to preserve native plants in this global biodiversity hotspot.

opencc-by-nd-4.0Jan 2024View details →

Figure 5. A in Defensive behaviour of a moth (Crambidae: Eoophyla sp.) that mimics jumping spiders (Araneae: Salticidae) in tropical India

Figure 5. A, Composite image showing four successive positions (1-4) occupied by a female Plexippus paykulli on a vertical wall, near a stationary Eoophyla that was displaying its hindwings. Initially (1-2) this spider fed on a captured moth, but about 2 minutes later (3-4) it approached the Eoophyla from above. B, Detail of inset from (a).

opencc-by-nd-4.0Jan 2024View details →

Figure 3. A in Defensive behaviour of a moth (Crambidae: Eoophyla sp.) that mimics jumping spiders (Araneae: Salticidae) in tropical India

Figure 3. A spider' view of a Eoophyla with elevated hindwings, from the front (A), and from a more lateral position (B-C). BC, Note that, with more direct illumination (C), reflection in the "eyes" of the salticid image on the hindwing can be seen.

opencc-by-nd-4.0Jan 2024View details →

Figure 2 in Defensive behaviour of a moth (Crambidae: Eoophyla sp.) that mimics jumping spiders (Araneae: Salticidae) in tropical India

Figure 2. Eoophyla before (A) and after (B) raising its hindwings to display the image of a salticid in two directions, on a vertical wall.

opencc-by-4.0Apr 2024View details →

GFDL AM2.1 Model Output -Changes in Monsoon Meteorological Elements Due to the Warming of the Tropical Indian Ocean

Changes in Climatological Mean Stream Function, Eddy Flux, Wind Field, Moisture Flux, and Precipitation from May to September Due to the Warming of the Indian Ocean

opencc-zeroApr 2024View details →

Phenotypic plasticity in tropical butterflies is linked to climatic seasonality on a macroevolutionary scale

Phenotypic plasticity can be adaptive in fluctuating environments by providing rapid environment-phenotype matching and this applies particularly in seasonal environments. African Bicyclus butterflies have repeatedly colonized seasonal savannahs from ancestral forests around the Late Miocene and many species now exhibit seasonal polyphenism. On a macroevolutionary scale, it can be expected that savannah species will exhibit higher plasticity due to them experiencing stronger environmental seasonality than forest species. We quantified seasonality using environmental niche modelling, and surveyed the degree of plasticity in a key wing pattern element (eyespot size) using museum specimens. We show that species occurring in highly seasonal environments display strong plasticity, while species in less seasonal or aseasonal environments exhibit surprisingly variable degrees of plasticity, including strong to no plasticity. Furthermore, eyespot size plasticity has a moderate phylogenetic signal and the ancestral Bicyclus likely exhibited some degree of plasticity. We propose hypotheses to explain the range of plasticity patterns seen in less seasonal environments, and generate testable predictions for the evolution of plasticity in Bicyclus. Our study provides one of the most compelling cases showing links between seasonality and phenotypic plasticity on a macroevolutionary scale and the potential role of plasticity in facilitating the colonization of novel environments.

opencc-by-4.0Aug 2023View details →

Novel climates are already widespread beneath the world's tropical forest canopies.

R code and data to accompany 'Novel climates are already widespread beneath the world’s tropical forest canopies'.