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1. Functional traits and ecological niches as correlates of the interspecific growth–mortality trade‐off among seedlings of 14 tropical tree species

   https://doi.org/10.1111/1365-2435.14624  

   Zhang, Caicai; Gu, Rong; Lin, Luxiang; Russo, Sabrina E (July 2024, Functional Ecology)

   The interspecific trade‐off between growth versus mortality rates of tree species is thought to be driven by functional biology and to contribute to species ecological niche differentiation. Yet, functional trait variation is often not strongly correlated with growth and mortality, and few studies have investigated the relationships of both traits and niches, specifically encompassing above and belowground resources, to the trade‐off itself. These relationships are particularly relevant for seedlings, which must often survive resource limitation to reach larger size classes.We investigated the functional basis of the interspecific growth–mortality trade‐off and its relationship with ecological niches for seedlings of 14 tree species in a tropical forest in southwest China.We found evidence for an interspecific growth–mortality trade‐off at the seedling stage using 15 functional traits and 15 ecological niche variables. None of the organ‐level traits correlated with growth, mortality, nor the trade‐off, whereas specific stem length (SSL), a biomass allocation trait, was the only trait to have a significant correlation (positive). Moreover, light‐defined niches were not correlated with growth, mortality or the trade‐off, but soil‐defined niches did. Species at the faster growth/higher mortality end of the trade‐off were associated with higher fertility defined by lower soil bulk density and slope, and higher soil organic matter concentration and soil total nitrogen.Our findings indicate the importance of stem elongation and soil fertility for growth, mortality and their trade‐off at the seedling stage in this Asian tropical forest. Our findings contrast with analogous studies in neotropical forests showing the importance of photosynthesis‐related leaf traits related to insolation. Therefore, the functional drivers of demographic rates and trade‐offs, as well as their consequences for ecological niches, can vary among forests, likely owing to differences in biogeography, canopy disturbance rates, topography and soil properties. Moreover, the effects of functional trait variation on demographic rates and trade‐offs may be better revealed when biomass allocation is accounted for in a whole‐plant context. Read the freePlain Language Summaryfor this article on the Journal blog. 

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2. Unveiling the integration of above- and below-ground tree carbon-hydraulic traits in Amazonian trees across hydrological niches

   https://doi.org/10.1093/treephys/tpaf063  

   Brum, Mauro; Oliveira-Junior, Raimundo Cosme; Alves, Luciana F; Agee, Elizabeth; Pereira, Luciano; Penha, Deliane; Araujo, Carina; Mayer, Juliana_L S; Pereira_Moutinho, Victor Hugo; Oliveira, Rafael S; et al (July 2025, Tree Physiology)

   Johnson, Daniel (Ed.)

   Abstract Understanding trait coordination and trade-offs along the root-to-leaf hydraulic pathway is critical for assessing forest functioning, as these traits significantly impact ecosystem carbon allocation and water use. Here, we investigated the relationship between carbon and hydraulic traits in 11 Amazonian tree species distributed across vertically structured hydrological niches. Using a carbon-hydraulic framework, we tested the hypothesis that interspecific differences arise from the optimization of xylem hydraulic efficiency, reflecting how tropical trees balance water transport efficiency with the carbon costs of maintaining transport tissues across vertical canopy positions. Our results show that above-ground traits were largely explained by canopy position (vertical stratification), whereas below-ground carbon-hydraulic traits were predominantly influenced by interspecific differences. Upper canopy trees exhibited lower and less variable specific root length (SRL) than shallow-rooted understory trees, indicating divergent carbon allocation strategies. Thicker terminal roots had higher hydraulic conductivity (Ks) than finer roots, but Ks declined from roots to terminal branches in most species. Additionally, branch and leaf Ks increase with tree size, indicating greater hydraulic efficiency in larger canopy species. Below-ground, we presented evidence that an increase in SRL is linked to decreased hydraulic conductivity and is influenced by root diameter. Above-ground, branch and leaf hydraulic conductivity tend to be higher in species with higher wood density, which are also more prevalent in upper canopy layers. Together, our findings reveal a coordinated above- and below-ground carbon-hydraulic trait framework across Amazonian trees. Species that occupy different vertical above-ground hydrological niches in lowland Amazon forests exhibit different carbon allocation strategies, which helps explain variation in species dominance and resource use throughout the vertical forest profile. 

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3. Predicting plant species climate niches on the basis of mechanistic traits

   https://doi.org/10.1111/1365-2435.14422  

   Medeiros, Camila D; Henry, Christian; Trueba, Santiago; Anghel, Ioana; Guerrero, Samantha_Dannet_Diaz_de Leon; Pivovaroff, Alexandria; Fletcher, Leila R; John, Grace P; Lutz, James A; Méndez Alonzo, Rodrigo; et al (November 2023, Functional Ecology)

   Abstract Improved estimation of climate niches is critical, given climate change. Plant adaptation to climate depends on their physiological traits and their distributions, yet traits are rarely used to inform the estimation of species climate niches, and the power of a trait‐based approach has been controversial, given the many ecological factors and methodological issues that may result in decoupling of species' traits from their native climate.For 107 species across six ecosystems of California, we tested the hypothesis that mechanistic leaf and wood traits can robustly predict the mean of diverse species' climate distributions, when combining methodological improvements from previous studies, including standard trait measurements and sampling plants growing together at few sites. Further, we introduce an approach to quantify species' trait‐climate mismatch.We demonstrate a strong power to predict species mean climate from traits. As hypothesized, the prediction of species mean climate is stronger (and mismatch lower) when traits are sampled for individuals closer to species' mean climates.Improved resolution of species' climate niches based on mechanistic traits can importantly inform conservation of vulnerable species under the threat of climatic shifts in upcoming decades. Read the freePlain Language Summaryfor this article on the Journal blog. 

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4. Metabarcoding Reveals Temporal Patterns of Community Composition and Realized Thermal Niches of Thalassiosira Spp. (Bacillariophyceae) from the Narragansett Bay Long-Term Plankton Time Series

   https://doi.org/10.3390/biology9010019  

   Rynearson, Tatiana A.; Flickinger, Sarah A.; Fontaine, Diana N. (January 2020, Biology)

   Diatoms generate nearly half of marine primary production and are comprised of a diverse array of species that are often morphologically cryptic or difficult to identify using light microscopy. Here, species composition and realized thermal niches of species in the diatom genus Thalassiosira were examined at the site of the Narragansett Bay (NBay) Long-Term Plankton Time Series using a combination of light microscopy (LM), high-throughput sequencing (HTS) of the 18S rDNA V4 region and historical records. Thalassiosira species were identified over 6 years using a combination of LM and DNA sequences. Sixteen Thalassiosira taxa were identified using HTS: nine were newly identified in NBay. Several newly identified species have small cell diameters and are difficult to identify using LM. However, they appeared frequently and thus may play a significant ecological role in NBay, particularly since their realized niches suggest they are eurythermal and able to tolerate the >25 °C temperature range of NBay. Four distinct species assemblages that grouped by season were best explained by surface water temperature. When compared to historical records, we found that the cold-water species Thalassiosira nordenskioeldii has decreased in persistence over time, suggesting that increasing surface water temperature has influenced the ecology of phytoplankton in NBay. 

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5. ‘Slow‐Fast’ Plant Trait Spectra Are Associated With Ecological Niches Across Global Climatic Gradients

   https://doi.org/10.1111/geb.70115  

   Chen, Yuheng; Hautier, Yann; Kowalchuk, George A; Barry, Kathryn E (September 2025, Global Ecology and Biogeography)

   ABSTRACT AimGlobal climate change is compressing species' realised niches and further threatening their distributions. Species traits, especially the trait spectra synthesised from traits, are one way in which species can match changes in their environment. Hence, integrating trait spectra and niches will help us understand how species adapt to their environment under global change. LocationGlobal. Time PeriodPresent. Major Taxa StudiedAngiosperms. MethodWe collected root traits from 158 angiosperm species and leaf traits from 512 angiosperm species from a global trait database to construct the leaf and root trait ‘slow‐fast’ spectrum based on resource acquisition strategy, as well as the collaboration spectrum related to root mycorrhizal colonisation. After rebuilding their phylogenetic relationships and defining species' environmental niches based on 213,979 occurrences of these species, we examined the relationship between these trait spectra and environmental niches along global climatic patterns. ResultPlants with ‘slow’ leaf traits were generally associated with narrow niche breadths and marginal niche positions, especially in high precipitation areas. The relationship between the ‘slow‐fast’ spectrum in root traits and ‘marginal‐central’ niche position reversed with decreasing precipitation. However, the relationships between leaf traits and niche variables were significant for woody species but not for herbaceous species. Main ConclusionOur research expands the plant trait spectra in macroecology applications. The root and leaf ‘slow‐fast’ trait spectra of angiosperms are driven by both macroclimate and long‐term evolutionary pressure. Understanding how these traits relate to the niche of species helps to predict how that species is likely to adapt to environmental change, which can enhance the predictive ability of niche theory for plant environmental adaptability. 

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