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1. Montane Temperate-Boreal Forests Retain the Leaf Economic Spectrum Despite Intraspecific Variability

   https://doi.org/10.3389/ffgc.2021.754063  

   Hecking, Matthew J.; Zukswert, Jenna M.; Drake, John E.; Dovciak, Martin; Burton, Julia I. (January 2022, Frontiers in Forests and Global Change)

   Trait-based analyses provide powerful tools for developing a generalizable, physiologically grounded understanding of how forest communities are responding to ongoing environmental changes. Key challenges lie in (1) selecting traits that best characterize the ecological performance of species in the community and (2) determining the degree and importance of intraspecific variability in those traits. Recent studies suggest that globally evident trait correlations (trait dimensions), such as the leaf economic spectrum, may be weak or absent at local scales. Moreover, trait-based analyses that utilize a mean value to represent a species may be misleading. Mean trait values are particularly problematic if species trait value rankings change along environmental gradients, resulting in species trait crossover. To assess how plant traits (1) covary at local spatial scales, (2) vary across the dominant environmental gradients, and (3) can be partitioned within and across taxa, we collected data on 9 traits for 13 tree species spanning the montane temperate—boreal forest ecotones of New York and northern New England. The primary dimension of the trait ordination was the leaf economic spectrum, with trait variability among species largely driven by differences between deciduous angiosperms and evergreen gymnosperms. A second dimension was related to variability in nitrogen to phosphorous levels and stem specific density. Levels of intraspecific trait variability differed considerably among traits, and was related to variation in light, climate, and tree developmental stage. However, trait rankings across species were generally conserved across these gradients and there was little evidence of species crossover. The persistence of the leaf economics spectrum in both temperate and high-elevation conifer forests suggests that ecological strategies of tree species are associated with trade-offs between resource acquisition and tolerance, and may be quantified with relatively few traits. Furthermore, the assumption that species may be represented with a single trait value may be warranted for some trait-based analyses provided traits were measured under similar light levels and climate conditions. 

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2. Influence of tree height and age on leaf drip‐tip morphology in lowland tropical rainforest trees

   https://doi.org/10.1111/1365-2435.70218  

   Grover, Emma C; Metz, Margaret R; Valencia, Renato; Queenborough, Simon A (December 2025, Functional Ecology)

   Across biomes, plant form and function are driven largely by variation in climate, particularly the availability of light and water. Strong gradients of these resources also exist within plant communities. For example, light availability above the canopy of an old‐growth tropical forest decreases to less than 2% photosynthetically active radiation at the forest floor, meaning that as an individual ages and grows taller it will encounter variation in light or other microclimate conditions in higher canopy layers. Exploring associations between leaf morphology and environmental variables can therefore illuminate the processes that drive selection on leaf traits. Drip‐tips (long, acuminate leaf apices) are a characteristic functional trait of rainforest trees. They are thought to aid the removal of water from the leaf surface, enabling a rapid return to photosynthesis and evapotranspiration. The utility of drip‐tips for this purpose should vary with a tree's microclimatic conditions and be especially beneficial to plants in the humid, light‐limited forest understory. In this study, we assessed variation in leaf drip‐tips in an ever‐wet, hyper‐diverse tropical rainforest, using a mixture of field and herbarium leaf samples from a 50‐hectare forest dynamics plot in Yasuní National Park, Ecuador. We examined how tree developmental stage and species canopy height maxima are associated with variation in the absolute length of drip‐tips. Within individual trees, we found that drip‐tips were longer by 0.27 ± 0.06 cm (mean ± SE) in leaves collected 25 years ago than from the same tree today, and across species by 0.95 ± 0.09 cm in shorter than taller trees. These differences tended to be larger for species with a growth form that reached greater maximum canopy heights than species that inhabit the understory. Synthesis. These findings support the hypothesis that longer drip‐tips are more advantageous in the dark, humid understory compared to the well‐lit, dry canopy. Further, drip‐tip variation is likely linked to the gradual changes in microclimate associated with tree development. Even minute increases in drip‐tip length while trees occupy the forest understory could play a substantial role in drying the leaf surface and moderating leaf–climate interactions. 

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3. Successful Alien Plant Species Exhibit Functional Dissimilarity From Natives Under Varied Climatic Conditions but Not Under Increased Nutrient Availability

   https://doi.org/10.1111/jvs.70032  

   Milanović, Marija; Bakker, Jonathan D; Biederman, Lori; Borer, Elizabeth T; Catford, Jane A; Cleland, Elsa; Hagenah, Nicole; Haider, Sylvia; Harpole, W Stanley; Komatsu, Kimberly; et al (March 2025, Journal of Vegetation Science)

   ABSTRACT AimsThe community composition of native and alien plant species is influenced by the environment (e.g., nutrient addition and changes in temperature or precipitation). A key objective of our study is to understand how differences in the traits of alien and native species vary across diverse environmental conditions. For example, the study examines how changes in nutrient availability affect community composition and functional traits, such as specific leaf area and plant height. Additionally, it seeks to assess the vulnerability of high‐nutrient environments, such as grasslands, to alien species colonization and the potential for alien species to surpass natives in abundance. Finally, the study explores how climatic factors, including temperature and precipitation, modulate the relationship between traits and environmental conditions, shaping species success. LocationIn our study, we used data from a globally distributed experiment manipulating nutrient supplies in grasslands worldwide (NutNet). MethodsWe investigate how temporal shifts in the abundance of native and alien species are influenced by species‐specific functional traits, including specific leaf area (SLA) and leaf nutrient concentrations, as well as by environmental conditions such as climate and nutrient treatments, across 17 study sites. Mixed‐effects models were used to assess these relationships. ResultsAlien and native species increasing in their abundance did not differ in their leaf traits. We found significantly lower specific leaf area (SLA) with an increase in mean annual temperature and lower leaf Potassium with mean annual precipitation. For trait–environment relationships, when compared to native species, successful aliens exhibited an increase in leaf Phosphorus and a decrease in leaf Potassium with an increase in mean annual precipitation. Finally, aliens' SLA decreased in plots with higher mean annual temperatures. ConclusionsTherefore, studying the relationship between environment and functional traits may portray grasslands' dynamics better than focusing exclusively on traits of successful species, per se. 

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4. The pace of life for forest trees

   https://doi.org/10.1126/science.adk9616  

   Bialic-Murphy, Lalasia; McElderry, Robert M; Esquivel-Muelbert, Adriane; van_den_Hoogen, Johan; Zuidema, Pieter A; Phillips, Oliver L; de_Oliveira, Edmar Almeida; Loayza, Patricia Alvarez; Alvarez-Davila, Esteban; Alves, Luciana F; et al (October 2024, Science)

   Tree growth and longevity trade-offs fundamentally shape the terrestrial carbon balance. Yet, we lack a unified understanding of how such trade-offs vary across the world’s forests. By mapping life history traits for a wide range of species across the Americas, we reveal considerable variation in life expectancies from 10 centimeters in diameter (ranging from 1.3 to 3195 years) and show that the pace of life for trees can be accurately classified into four demographic functional types. We found emergent patterns in the strength of trade-offs between growth and longevity across a temperature gradient. Furthermore, we show that the diversity of life history traits varies predictably across forest biomes, giving rise to a positive relationship between trait diversity and productivity. Our pan-latitudinal assessment provides new insights into the demographic mechanisms that govern the carbon turnover rate across forest biomes. 

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5. On the modelling of tropical tree growth: the importance of intra-specific trait variation, non-linear functions and phenotypic integration

   https://doi.org/10.1093/aob/mcaa085  

   Yang, Jie; Song, Xiaoyang; Cao, Min; Deng, Xiaobao; Zhang, Wenfu; Yang, Xiaofei; Swenson, Nathan G (May 2020, Annals of Botany)

   null (Ed.)

   Abstract Background and Aims The composition and dynamics of plant communities arise from individual-level demographic outcomes, which are driven by interactions between phenotypes and the environment. Functional traits that can be measured across plants are frequently used to model plant growth and survival. Perhaps surprisingly, species average trait values are often used in these studies and, in some cases, these trait values come from other regions or averages calculated from global databases. This data aggregation potentially results in a large loss of valuable information that probably results in models of plant performance that are weak or even misleading. Methods We present individual-level trait and fine-scale growth data from >500 co-occurring individual trees from 20 species in a Chinese tropical rain forest. We construct Bayesian models of growth informed by theory and construct hierarchical Bayesian models that utilize both individual- and species-level trait data, and compare these models with models only using individual-level data. Key Results We show that trait–growth relationships measured at the individual level vary across species, are often weak using commonly measured traits and do not align with the results of analyses conducted at the species level. However, when we construct individual-level models of growth using leaf area ratio approximations and integrated phenotypes, we generated strong predictive models of tree growth. Conclusions Here, we have shown that individual-level models of tree growth that are built using integrative traits always outperform individual-level models of tree growth that use commonly measured traits. Furthermore, individual-level models, generally, do not support the findings of trait–growth relationships quantified at the species level. This indicates that aggregating trait and growth data to the species level results in poorer and probably misleading models of how traits are related to tree performance. 

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