Extreme drought events have negative effects on forest diversity and functioning. At the species level, however, these effects are still unclear, as species vary in their response to drought through ...specific functional trait combinations. We used long‐term demographic records of 21,821 trees and extensive databases of traits to understand the responses of 338 tropical dry forests tree species to ENSO2015, the driest event in decades in Northern South America. Functional differences between species were related to the hydraulic safety‐efficiency trade‐off, but unexpectedly, dominant species were characterised by high investment in leaf and wood tissues regardless of their leaf phenological habit. Despite broad functional trait combinations, tree mortality was more widespread in the functional space than tree growth, where less adapted species showed more negative net biomass balances. Our results suggest that if dry conditions increase in this ecosystem, ecological functionality and biomass gain would be reduced.
Extreme drought events have negative effects on forest diversity and functioning. We used long‐term demographic records of 21,821 trees and extensive databases of traits to understand the responses of 338 tropical dry forests tree species to an extreme. Our results indicate that irrespective of the drought adaptations, most trees will be negatively affected under drier scenarios predicted for tropical dry forests.
Summary
Leaf habit has been hypothesized to define a linkage between the slow‐fast plant economic spectrum and the drought resistance‐avoidance trade‐off in tropical forests (‘slow‐safe vs ...fast‐risky’). However, variation in hydraulic traits as a function of leaf habit has rarely been explored for a large number of species.
We sampled leaf and branch functional traits of 97 tropical dry forest tree species from four sites to investigate whether patterns of trait variation varied consistently in relation to leaf habit along the ‘slow‐safe vs fast‐risky’ trade‐off.
Leaf habit explained from 0% to 43.69% of individual trait variation. We found that evergreen and semi‐deciduous species differed in their location along the multivariate trait ordination when compared to deciduous species. While deciduous species showed consistent trait values, evergreen species trait values varied as a function of the site. Last, trait values varied in relation to the proportion of deciduous species in the plant community.
We found that leaf habit describes the strategies that define drought avoidance and plant economics in tropical trees. However, leaf habit alone does not explain patterns of trait variation, which suggests quantifying site‐specific or species‐specific uncertainty in trait variation as the way forward.
Although one-quarter of plant and vertebrate species are threatened with extinction, little is known about the potential effect of extinctions on the global diversity of ecological strategies. Using ...trait and phylogenetic information for more than 75,000 species of vascular plants, mammals, birds, reptiles, amphibians, and freshwater fish, we characterized the global functional spectra of each of these groups. Mapping extinction risk within these spectra showed that larger species with slower pace of life are universally threatened. Simulated extinction scenarios exposed extensive internal reorganizations in the global functional spectra, which were larger than expected by chance for all groups, and particularly severe for mammals and amphibians. Considering the disproportionate importance of the largest species for ecological processes, our results emphasize the importance of actions to prevent the extinction of the megabiota.
Abstract
We tested the idea that functional trade‐offs that underlie species tolerance to drought drive shifts in community composition via their effects on demographic processes and subsequently on ...shifts in species' abundance. Using data from 298 tree species from tropical dry forests during the extreme ENSO‐2015, we scaled‐up the effects of trait trade‐offs from individuals to communities. Conservative wood and leaf traits favoured slow tree growth, increased tree survival and positively impacted species abundance and dominance at the community‐level. Safe hydraulic traits, on the other hand, were related to demography but did not affect species abundance and communities. The persistent effects of the conservative–acquisitive trade‐off across organizational levels is promising for generalization and predictability of tree communities. However, the safety–efficient trade‐off showed more intricate effects on performance. Our results demonstrated the complex pathways in which traits scale up to communities, highlighting the importance of considering a wide range of traits and performance processes.
Seasonally dry tropical forests are distributed across Latin America and the Caribbean and are highly threatened, with less than 10% of their original extent remaining in many countries. Using 835 ...inventories covering 4660 species of woody plants, we show marked floristic turnover among inventories and regions, which may be higher than in other neotropical biomes, such as savanna. Such high floristic turnover indicates that numerous conservation areas across many countries will be needed to protect the full diversity of tropical dry forests. Our results provide a scientific framework within which national decision-makers can contextuaiize the floristic significance of their dry forest at a regional and continental scale.
Question
Trait‐based ecology is built on the notion that traits impact individual performance, but trait–growth relationships have rarely been tested considering the intraspecific variation, trait ...interactions, and potential nonlinearity in these relationships.
Location
Seven tropical dry forests throughout Colombia.
Methods
We examined trait–growth relationships in 263 woody species of tropical dry forests in Colombia, including trait and growth information measured in the same individuals. We measured height, stem, and leaf traits related to growth and hydraulic safety–efficiency in 967 individuals in seven permanent plots (1 ha). We assessed trait–growth relationships using random forest models for each plot with different trait resolutions (individual, plot, area) and complexity of trait interactions (low, medium, high).
Results
Trait–growth relationships were generally weak without significant differences among trait resolutions or levels of interactions between traits. However, when considering leaf phenology, the proportion of growth variation explained in deciduous species was almost three times higher than in evergreen species. Finally, we found that the effect of traits on growth was consistent across plots and phenological strategies, with both stem (vessel area and pit diameter aperture) and leaf (leaf area and specific leaf area) traits ranked as important predictors, the relevance of which depended on the species’ leaf phenology.
Conclusions
Our findings indicate that growth is probably limited by different factors depending on the species’ physiology according to the leaf habit considered. However, other factors not included in the analysis, such as microenvironmental variability, might influence trait–growth relationships in tropical dry forests. Overall, our results suggest that a trait coordination approach at the whole‐plant level is needed to better understand plants’ performance and demographic rates in this ecosystem. Further studies on the traits of regional flora and consideration of longer growth periods would help to elucidate the dynamics governing trait composition in these forests, which is essential for the design of adequate forest restoration and conservation practices.
This study provides insights into the limited predictive power of functional traits for individual growth in Colombian tropical dry forests. However, some stem and leaf traits emerged as important predictors, emphasizing the role of leaf phenology in growth patterns: deciduous species show greater explained variation in growth than evergreens. These findings advocate for a whole‐plant research approach, accounting for fine‐grained environmental variation.
Apremilast, an oral phosphodiesterase 4 inhibitor, downregulates intracellular inflammatory mediator synthesis by elevating cyclic adenosine monophosphate levels. The PALACE 2 trial evaluated ...apremilast efficacy and safety in patients with active psoriatic arthritis (PsA) despite prior conventional disease-modifying antirheumatic drugs and/or biologic therapy.
Eligible patients were randomized (1:1:1) to placebo, apremilast 20 mg BID, or apremilast 30 mg BID. At Week 16, patients with swollen and tender joint count improvement < 20% entered early escape, with placebo patients rerandomized (1:1) to apremilast 20 mg BID or 30 mg BID while apremilast patients continued on their initial apremilast dose. At Week 24, patients remaining on placebo were rerandomized to apremilast 20 mg BID or 30 mg BID. The primary endpoint was the proportion of patients achieving > 20% improvement in American College of Rheumatology response criteria (ACR20) at Week 16.
In the intent-to-treat population (N = 484), ACR20 at Week 16 was achieved by more patients receiving apremilast 20 mg BID 37.4% (p = 0.0002) and 30 mg BID 32.1% (p = 0.0060) versus placebo (18.9%). Clinically meaningful improvements in signs and symptoms of PsA, physical function, and psoriasis were observed with apremilast through Week 52. The most common adverse events were diarrhea, nausea, headache, and upper respiratory tract infection. Diarrhea and nausea generally occurred early and usually resolved spontaneously with continued treatment. Laboratory abnormalities were infrequent and transient.
Apremilast demonstrated clinical improvements in PsA for up to 52 weeks, including signs and symptoms, physical function, and psoriasis. No new safety signals were observed. ClinicalTrials.gov identifier: NCT01212757.
Aims
Tropical dry forests are among the most threatened ecosystems on Earth, and understanding the effects of climate on their species distributions is critical to mitigate global change impacts. ...Here, we assessed the impact of precipitation and dispersal limitation by natural and anthropogenic causes on phylogenetic and taxonomic beta diversity of woody‐plant communities.
Location
Cauca River Canyon in the Northwest Andean mountains, Colombia.
Methods
We used inventory data from 160 0.02‐ha plots and a phylogenetic tree to calculate phylogenetic and taxonomic beta diversity and their components (nestedness and replacement) across plots. We used redundancy analysis to assess the effects of precipitation, spatial distance, and connectivity (a proxy of fragmentation) on changes in beta diversity metrics and estimated each variable's relative contribution.
Results
We found that both phylogenetic and taxonomic replacement were highly related to precipitation differences. Spatial distance and connectivity explained only a small proportion of the variance in phylogenetic and taxonomic replacement. None of the predictor variables explained phylogenetic or taxonomic nestedness.
Conclusions
Patterns of phylogenetic and taxonomic replacement across woody‐plant communities suggest that species and clades are highly specialized to particular precipitation regimes with a minor role for dispersal limitation. Both climate change and fragmentation could drastically influence the future community composition of tropical dry forests.
The patterns of phylogenetic and taxonomic replacement across woody plant communities suggest that species and clades are highly specialized to particular precipitation regimes with a minor role for dispersal limitation. Both climate change and fragmentation could drastically influence the future community composition of tropical dry forests.
The aim of this study was to improve our understanding of what controls the isotope composition of Cu, Zn and Pb in particulate matter (PM) in the urban environment and to develop these isotope ...systems as possible source tracers. To this end, isotope ratios (Cu, Zn and Pb) and trace element concentrations (Fe, Al, Cu, Zn, Sb, Ba, Pb, Cr, Ni and V) were determined in PM10 collected at two road sites with contrasting traffic densities in central London, UK, during two weeks in summer 2010, and in potential sources, including non-combustion traffic emissions (tires and brakes), road furniture (road paint, manhole cover and road tarmac surface) and road dust. Iron, Ba and Sb were used as proxies for emissions derived from brake pads, and Ni, and V for emissions derived from fossil fuel oil.
The isotopic composition of Pb (expressed using 206Pb/207Pb) ranged between 1.1137 and 1.1364. The isotope ratios of Cu and Zn expressed as δ65CuNIST976 and δ66ZnLyon ranged between −0.01‰ and +0.51‰ and between −0.21‰ and +0.33‰, respectively. We did not find significant differences in the isotope signatures in PM10 over the two weeks sampling period and between the two sites, suggesting similar sources for each metal at both sites despite their different traffic densities. The stable isotope composition of Pb suggests significant contribution from road dust resuspension and from recycled leaded gasoline. The Cu and Zn isotope signatures of tires, brakes and road dust overlap with those of PM10. The correlation between the enrichments of Sb, Cu, Ba and Fe in PM10 support the previously established hypothesis that Cu isotope ratios are controlled by non-exhaust traffic emission sources in urban environments (Ochoa Gonzalez et al., 2016). Analysis of the Zn isotope signatures in PM10 and possible sources at the two sites suggests significant contribution from tire wear. However, temporary additional sources, likely high temperature industrial emissions, need to be invoked to explain the isotopically light Zn found in 3 out of 18 samples of PM10.
•Copper, Zn and Pb isotope ratios of PM10 at two sites with different traffic densities in London were determined.•Stable isotopic compositions of Cu, Zn and Pb suggest similar sources for these trace metals at both sites.•Anthropogenic sources including recycled gasoline and road dust remain important for lead.•Non-exhaust emissions are the major source of Cu in PM10.•Re-suspended road dust and non-exhaust traffic sources dominate the sources of Zn.
Tropical dry forests (TDF) are known to be resource‐limited due to a marked seasonality in precipitation. However, TDF are also shaped by factors such as solar radiation, wind speed, soil fertility, ...and land‐cover transformation. Together, these factors may determine different gradients of environmental harshness that are likely to drive changes in plant community attributes. Here, we evaluated the effects of environmental harshness on plant community diversity and structure of Colombian TDF, based on floristic and environmental data from 15 1‐ha permanent plots. We also analyzed these effects on legumes species only (including both deciduous and non‐deciduous species), deciduous species only (including both legumes and non‐legumes species), and on the whole community excluding either legumes or deciduous separately. Drier conditions and higher land‐cover transformation had the strongest negative effects on species diversity, basal area (BA), and canopy height. Soil fertility, on the contrary, did not have a significant effect on any of the evaluated response variables. Interestingly, legumes maintained their diversity and BA along the climatic gradient, while deciduous species were negatively affected by drier conditions and by an increase in secondary vegetation at the landscape level. Our results suggest that although TDF are limited by water availability, land‐cover transformation strongly increases environmental harshness. Yet, both legumes and deciduous species were differentially impacted by climatic and land transformation variables. Thus, to better understand TDF plant community attributes, it is necessary to consider these gradients and to disentangle their effects on different plant functional groups.
in Spanish is available with online material.
Resumen
Es ampliamente conocido que los bosques secos tropicales (BST) tienen fuertes limitaciones de recursos derivadas de estacionalidad de la precipitación. Sin embargo, otros factores como la radiación solar, la velocidad del viento, la fertilidad de los suelos y la transformación de las coberturas también dan forma a las condiciones ambientales restrictivas de este ecosistema. En conjunto, estos factores determinan la dureza ambiental que rige el BST y probablemente explican los cambios en los atributos comunitarios de las plantas a lo largo de gradientes. Evaluamos los efectos de la dureza ambiental sobre la diversidad de plantas y atributos estructurales del BST con base en datos florísticos y ambientales para 15 parcelas permanentes de 1 ha, para toda la comunidad de plantas, y subgrupos de plantas que incluyeron solo especies de leguminas y solo caducifolias por separado. Las condiciones secas y coberturas altamente transformadas tuvieron los efectos negativos sobre la diversidad de especies, el área basal y la altura del dosel a nivel comunitario, mientras que la fertilidad del suelo no afectó a ninguno de los atributos evaluados. Interesantemente, el grupo de especies leguminosas mantuvieron su diversidad y área basal a lo largo del gradiente de severidad climática, mientras que el grupo de especies de hoja caduca se vio negativamente afectado por las condiciones más secas y el aumento en el área de coberturas secundarias. Nuestros resultados sugieren que, aunque el BST esta claramente limitado por la disponibilidad del agua, la transformación de las coberturas naturales impulsa el aumento de la dureza ambiental en este ecosistema. Donde, las especies de leguminosas y caducifolias se ven afectadas de manera diferente a toda la comunidad de plantas. De tal forma, para un mejor entendimiento de como cambian los atributos comunitarios de las plantas en los BST es necesario tener en cuenta todas las fuentes de variación ambiental, así como, desagregar los efectos particulares para determinados grupos funcionales de plantas.
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