Understanding how tropical rainforest trees may respond to the precipitation extremes predicted in future climate change scenarios is paramount for their conservation and management. Tree species ...clearly differ in drought susceptibility, suggesting that variable water transport strategies exist. Using a multi-disciplinary approach, we examined the hydraulic variability in trees in a lowland tropical rainforest in north-eastern Australia. We studied eight tree species representing broad plant functional groups (one palm and seven eudicot mature-phase, and early-successional trees). We characterised the species' hydraulic system through maximum rates of volumetric sap flow and velocities using the heat ratio method, and measured rates of tree growth and several stem, vessel, and leaf traits. Sap flow measures exhibited limited variability across species, although early-successional species and palms had high mean sap velocities relative to most mature-phase species. Stem, vessel, and leaf traits were poor predictors of sap flow measures. However, these traits exhibited different associations in multivariate analysis, revealing gradients in some traits across species and alternative hydraulic strategies in others. Trait differences across and within tree functional groups reflect variation in water transport and drought resistance strategies. These varying strategies will help in our understanding of changing species distributions under predicted drought scenarios.
•Diversity effect on aboveground biomass is dependent on forests’ land-use history and surrounding landscape matrix.•Disturbance can modulate the relationship between evolutionary diversity and ...biomass storage.•Evolutionary diversity is positively related to aboveground biomass only in old-growth, non-urban forests.•Niche complementarity leads to higher above-ground biomass in certain ecological contexts.•Strategies for conservation and restoration should account for past land-use and the surrounding landscape matrix.
Understanding the drivers of aboveground biomass (AGB) variation in present-day tropical forests can contribute to management strategies that help mitigate against CO2-driven climate change and provide other services related to high AGB. Higher tree diversity can lead to higher woody productivity and carbon storage, but how diversity interacts with land-use history is less certain. We assessed variation in AGB across forests with different land-use histories and surrounding landscapes in southeastern Brazil and how AGB relates to tree diversity per se, while controlling for important factors such as mean functional trait values, stem density and soil fertility. Our findings indicate that aboveground biomass of forests is dependent on land-use history and the landscape matrix in which they occur (urban or non-urban). We found that tree diversity, measured as the average evolutionary divergence among close relatives, shows a strong positive relationship to AGB, but only in old-growth, non-urban forests. This suggests that higher niche complementarity leads to higher AGB in certain ecological contexts. Forests in an urban matrix, and those that regenerated from cropland (in an urban or non-urban matrix), showed weak or insignificant relationships between AGB and diversity, and forests that regenerated from completely denuded landscapes, including soil removal, actually showed a negative relationship between diversity and AGB. Meanwhile, across all forest classes, the abundance-weighted mean wood density of tree species present showed a consistent positive correlation with AGB, indicating the ubiquity of mass-ratio effects on AGB. Overall, our study suggests that strategies for conservation and restoration should account for past land-use and the matrix where forests are inserted, as the distribution of carbon stocks and biodiversity may need to be considered separately.
Large‐scale data compilation is increasing steadily in tropical forest research, but the lack of standardized methods for data collection limits drawing inference from large datasets and cross‐biome ...analyses. Different inclusion methods and minimum tree diameter threshold are among these varying factors. To tackle this issue, we evaluated how different approaches for tree sampling affects our understanding of diversity and functioning in different tropical vegetation types.
We used a unique dataset of 44 inventory plots (43.54 ha) encompassing an aridity gradient: evergreen moist forests, semideciduous and deciduous tropical forests. Data were collected using the by‐tree inclusion method, in which, all stems are measured if the equivalent diameter of the tree reaches the minimum threshold. We simulated the impact of adopting different inclusion methods (by‐stem and by‐tree) and different minimum diameter thresholds on the estimation of number of trees and stems, biomass and species richness. We used linear and nonlinear mixed models to investigate the effect of minimum diameter threshold and inclusion method on our different response variables. We also evaluated species chance to be sampled under different minimum inclusion criteria.
Inclusion method and minimum diameter threshold mainly affect the estimation of number of trees and stems and species richness, especially in deciduous and semideciduous forests, where resprouting is a prevalent strategy. In these forests, many trees that have several stems do not reach the minimum size individually when adopting the by‐stem method, yet they do reach the minimum size threshold when all stems are considered together. For these environments under water stress, our analysis showed that using large minimum sizes, such as the 10 cm typically used in rainforests, implies large sampling losses, especially when used jointly with the by‐stem inclusion method.
The by‐tree inclusion method represents an alternative approach that offers a more reliable sampling in different vegetation types, particularly in those habitats where resprouting is a widely encountered strategy along all age classes. We demonstrate the infeasibility of adopting broad and standard minimum thresholds for different tropical vegetation types, particularly considering their widely different ecological strategies.
Resumo
A compilação de dados em grande escala tem aumentado expressivamente nas pesquisas sobre florestas tropicais. No entanto, a falta de métodos padronizados para a coleta de dados limita a capacidade de inferência em grandes conjuntos de dados, assim como as comparações entre biomas. A adoção de diferentes métodos de inclusão e de tamanho mínimo de inclusão de árvores são exemplos de métodos com grande variação na literatura. Para buscar resolver este problema, avaliamos como diferentes abordagens para amostragem de árvores afetam nossa compreensão da diversidade e funcionamento de diferentes tipos de vegetação tropical.
Usamos um conjunto de dados único de 44 florestas tropicais (43,54 ha) abrangendo um gradiente de aridez: florestas ombrófilas, florestas semidecíduas e florestas decíduas. Os dados foram coletados utilizando‐se o método de inclusão por árvore, em que todos os fustes são medidos se o diâmetro equivalente da árvore atingir o tamanho mínimo. Simulamos o impacto da adoção de diferentes métodos de inclusão (por árvore e por fuste) e diferentes tamanhos mínimos de inclusão na estimativa do número de árvores e fustes, biomassa e riqueza de espécies. Usamos modelos lineares e não lineares mistos para investigar o efeito do tamanho mínimo de inclusão e do método de inclusão em nossas diferentes variáveis resposta. Também avaliamos a chance de as espécies serem amostradas sob diferentes tamanhos mínimos de inclusão.
O método de inclusão e o tamanho mínimo de inclusão afetam principalmente a estimativa do número de árvores, fustes e a riqueza de espécies, especialmente em florestas decíduas e semideciduais, onde o perfilhamento é uma estratégia ecológica importante. Nessas florestas, muitas árvores que possuem vários fustes não atingem o tamanho mínimo individualmente ao adotar o método por fuste, mas atingem o tamanho mínimo quando todos os fustes são considerados juntos. Para esses ambientes sob estresse hídrico, nossa análise mostrou que o uso de grandes tamanhos mínimos, como os 10 cm normalmente usados em florestas tropicais ombrófilas, implica em grandes perdas de amostragem, especialmente quando usado em conjunto com o método de inclusão por fuste.
O método de inclusão por árvore representa uma abordagem alternativa que oferece uma amostragem mais confiável em diferentes tipos de vegetação, particularmente naqueles onde perfilhamento é uma estratégia amplamente encontrada em todas as classes etárias. Nós demonstramos a inviabilidade de adotar tamanhos mínimos amplos e padronizados para diferentes tipos de vegetação tropical, particularmente considerando suas estratégias ecológicas amplamente diferentes.
In this paper, the performance assessment of three software single-phase phase-locked loop (PLL) algorithms is carried out by means of dynamic analysis and experimental results. Several line ...disturbances such as phase-angle jump, voltage sag, frequency step, and harmonics are generated by a DSP together with a D/A converter and applied to each PLL. The actual minus the estimated phase-angle values are displayed, providing a refined method for performance evaluation and comparison. Guidelines for parameters adjustments are also presented. In addition, practical implementation issues such as computational delay effects, ride-through, and computational load are addressed. The developed models proved to accurately represent the PLLs under real test conditions.
Aim
Global carbon cycle models do not incorporate the stabilizing effect of biodiversity on productivity despite this phenomenon has been widely described in several local scale manipulative ...experiments. The reason is a lack of evidence supporting the importance of biodiversity on spatial scales at which climate models are built. Here, we test the hypothesis that diversity enhances productivity stability at a large scale.
Location
South American dryland known as Caatinga (~830,000 km2).
Time period
2001–2010.
Major taxa studied
Woody plants.
Methods
We used the enhanced vegetation index of Caatinga vegetation remnants, from 2001 to 2010, to calculate vegetation productivity stability across years. We used occurrence records of 606 woody species from floristic surveys to derive species richness and phylogenetic diversity at ~5 km and ~55 km (0.5°) resolution. Climate data were obtained from global databases.
Results
Plant phylogenetic diversity has a strong positive correlation with productivity stability even after controlling for several climatic variables, such as rainfall, temperature and cloudiness, at both resolutions. Species richness was not significant when climatic variables were included.
Main conclusions
This result expands by several orders of magnitude the spatial scale of the evidence that biodiversity strengths the resilience of key ecosystem functions. We highlight that, by incorporating plant phylogenetic diversity, regional and global climate models can generate more accurate predictions about future ecosystem functioning and services that are critical to humankind.
Environmental gradients play a key role in shaping diversity in tropical forests. However, we have a little understanding of how evolutionary diversity is affected by gradients and the role of niche ...persistence in flooded forests in dry biomes. Here, we assessed the evolutionary diversity across a flooding gradient in the Caatinga Domain of South America. We established 120 plots across four tributaries of the São Francisco River, eastern Brazil, consisting of 72 plots in flooded, 24 in occasionally flooded, and 24 in unflooded forests. We computed richness, phylogenetic diversity (PD), mean nearest taxon distance (MNTD), and mean pairwise phylogenetic distance (MPD) and their standardized effect sizes (ses. PD, ses. MNTD, and ses. MPD). We found low richness, low PD, and high MNTD values in flooded forests relative to unflooded and occasionally flooded forests. MPD did not differ across the flooding gradient. The standardized effect size metrics were higher in flooded forests. Despite the unflooded and occasionally flooded forests being rich in terms of species and correlated phylogenetic structure, flooded forests showed more lineage diversity than expected by chance. We assessed whether this pattern could be driven by resprouting ability testing its phylogenetic signal. Resprouting is randomly distributed across phylogeny, but plant communities are likely assembled from random draws of the resprouters’ lineage pool. Quantifying evolutionary diversity across flooding gradients in dry environments brought new insights to how the same environmental filters may lead to disparate patterns of evolutionary diversity and the role of response traits in allowing certain clades to persist in flooded habitats.
Resprouting is a plant persistence strategy in response to disturbance or stressful environmental conditions. Resprouters can dominate in stressful environments such as tropical dry forests (TDFs), ...but our knowledge of resprouting in TDFs is limited. Here, using a dataset of forest inventories in 16 TDF fragments (covering 15,642 trees and 321 species), we investigated patterns of resprouting in ecosystems subject to substantial seasonal water stress. We focused on two resprouting metrics: the proportion of trees that are multistemmed (resprouting frequency) and the number of stems per tree. In addition, we investigated the relative importance of environmental factors, taxonomic identity, and evolutionary history in resprouting response. Taxa with low to medium resprouting frequencies (17.19%–40.2%) are the most prevalent in TDF, compared to non‐resprouters and high‐frequency resprouters. Overall, resprouting ability appears to be an intrinsic trait that varies in response to environmental conditions but only within a range constrained by taxonomic identity. However, we found no phylogenetic signal above the genus level for any resprouting variables. Thus, the variation in resprouting across TDF lineages likely has been shaped by divergence between closely related taxa and convergence between distantly related ones, reflecting the specific environmental and disturbance factors to which they have been subjected.
Resprouting is a common ecological strategy in trees in tropical dry forest (TDF).
Resprouting by trees is a very variable ecological strategy.
The patterns of resprouting in TDF is mainly conditioned by taxonomic identify, but not present phylogenetical structure.
The tree species composition of seasonally dry tropical forests (SDTF) in north‐eastern and central Brazil is analyzed to address the following hypotheses: (1) variations in species composition are ...related to both environment (climate and substrate) and spatial proximity; (2) SDTF floristic units may be recognized based on peculiar composition and environment; and (3) the Arboreal Caatinga, a deciduous forest occurring along the hinterland borders of the Caatinga Domain, is one of these units and its flora is more strongly related to the caatinga vegetation than to outlying forests. The study region is framed by the Brazilian coastline, 50th meridian west and 21st parallel south, including the Caatinga Domain and extensions into the Atlantic Forest and Cerrado Domains. Multivariate and geostatistic analyses were performed on a database containing 16,226 occurrence records of 1332 tree species in 187 georeferenced SDTF areas and respective environmental variables. Tree species composition varied significantly with both environmental variables and spatial proximity. Eight SDTF floristic units were recognized in the region, including the Arboreal Caatinga. In terms of species composition, its tree flora showed a stronger link with that of the Cerrado Dry Forest Enclaves. On the other hand, in terms of species frequency across sample areas, the links were stronger with two other units: Rock Outcrops Caatinga and Agreste and Brejo Dry Forests. There is a role for niche‐based control of tree species composition across the SDTFs of the region determined primarily by the availability of ground water across time and secondarily by the amount of soil mineral nutrients. Spatial proximity also contributes significantly to the floristic cohesion of SDTF units suggesting a highly dispersal‐limited tree flora. These units should be given the status of eco‐regions to help driving the conservation policy regarding the protection of their biodiversity.
Multivariate and geostatisctic analyses showed that the tree species composition of 187 seasonally dry tropical forests (SDTF) in North‐eastern and Central Brazil varied significantly with both environmental variables and spatial proximity. There is a role for niche‐based control of tree species composition across the SDTFs areas determined primarily by the availability of ground water across time and secondarily by the amount of soil mineral nutrients. Spatial proximity also contributes significantly to the floristic cohesion of SDTF units suggesting a highly dispersal‐limited tree flora.
Summary
Understanding the anatomical basis of plant water transport in forest ecosystems is crucial for contextualizing community‐level adaptations to drought, especially in life‐form‐rich tropical ...forests. To provide this context, we explored wood functional anatomy traits related to plant hydraulic architecture across different plant functional groups in a lowland tropical rain forest.
We measured wood traits in 90 species from six functional groups (mature‐phase, understorey and pioneer trees; understorey and pioneer shrubs; vines) and related these traits to intrinsic water‐use efficiency (WUEi) as a measure of physiological performance. We also examined vessel size distribution patterns across groups to determine trade‐offs in theoretical hydraulic safety vs. efficiency.
Some plant functional groups exhibited significant differences in vessel parameters and WUEi. Vessel diameters in vines and pioneer trees were two‐ to threefold greater on average than in understorey trees and shrubs. Contrastingly, vessels in understorey trees and shrubs fell within the smaller size classes, suggesting greater safety mechanisms. In addition to these trends, large vessel dimensions were important predictors of WUEi among the functional groups.
We conclude that wood functional anatomy profiles varied across plant functional groups in a tropical rain forest. These groups can therefore serve as a framework for further investigations on structure–function relationships and a sound basis for modelling species responses to drought.
A lay summary is available for this article.
Lay Summary
Summary
Women with absolute uterine factor infertility cannot get pregnant. The current experience in uterine transplantation is limited and the use of a deceased donor uterus in this area is ...incipient after some initial unsuccessful attempts. The birth of healthy babies through this modality in four different centers has given a new impetus to the use of this transplantation technique. We aimed to develop a technique for uterus procurement and preparation for transplantation from a brain dead donor. Fifteen uteri were retrieved from multi‐organ donor patients, 10 of these were used in bench surgeries with the proposed technique. All procedures were performed after obtaining family's consent. This study allowed the clinical use of two of the 15 organs that were procured for transplantation. One of these organs resulted in the first live birth worldwide using a uterus transplanted from a deceased donor, a landmark in reproductive medicine. Another outcome was the optimization of the surgical technique involving less manipulation of the uterine vascular pedicles. The success of this novel technique suggests that the proposed model can be replicated and optimized further to facilitate the transplantation of uterus from deceased donors.
This manuscript resumes a Brazilian and Colombian experience with fifteen uterus retrieval from deceased donors, it explains the surgical technique evolution and compares it with other experiences around the world in the same field.
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