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1. Contrasting adaptation and optimization of stomatal traits across communities at continental scale

   https://doi.org/10.1093/jxb/erac266  

   Liu, Congcong; Sack, Lawren; Li, Ying; He, Nianpeng (June 2022, Journal of Experimental Botany)

   Lawson, Tracy (Ed.)

   Abstract Shifts in stomatal trait distributions across contrasting environments and their linkage with ecosystem productivity at large spatial scales have been unclear. Here, we measured the maximum stomatal conductance (g), stomatal area fraction (f), and stomatal space-use efficiency (e, the ratio of g to f) of 800 plant species ranging from tropical to cold-temperate forests, and determined their values for community-weighted mean, variance, skewness, and kurtosis. We found that the community-weighted means of g and f were higher in drier sites, and thus, that drought ‘avoidance’ by water availability-driven growth pulses was the dominant mode of adaptation for communities at sites with low water availability. Additionally, the variance of g and f was also higher at arid sites, indicating greater functional niche differentiation, whereas that for e was lower, indicating the convergence in efficiency. When all other stomatal trait distributions were held constant, increasing kurtosis or decreasing skewness of g would improve ecosystem productivity, whereas f showed the opposite patterns, suggesting that the distributions of inter-related traits can play contrasting roles in regulating ecosystem productivity. These findings demonstrate the climatic trends of stomatal trait distributions and their significance in the prediction of ecosystem productivity. 

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2. Temporally disjunct herbaceous species differ in leaf embolism resistance

   https://doi.org/10.1111/nph.70335  

   Rimer, Ian M; McAdam, Scott_A M (September 2025, New Phytologist)

   Summary In the temperate Northern Hemisphere, herbaceous community composition undergoes major seasonal phenological shifts. Despite significant variation in water availability across growing seasons, few studies have associated physiological traits with seasonal shifts in community composition.Key ecophysiological traits, including leaf embolism resistance, were measured in 41 phylogenetically diverse herbaceous species native to the central forest‐grassland ecotone of North America. Traits were tracked monthly inSolidago canadensisL. to explore seasonal plasticity. Correlations between ecophysiological traits and flowering time, plant height, and ecological guild were examined. Further analyses were conducted to investigate if traits were constrained by phylogeny or seasonal differences in climatic variables.Taller and later flowering species had more embolism‐resistant leaf xylem and greater stomatal safety margins (SSM) than smaller, spring‐flowering species. We found no seasonal variation in traits inS. canadensis, suggesting minimal seasonal phenotypic plasticity in these traits. No phylogenetic signal was found for any trait suggesting that climate rather than phylogeny drives variation in ecophysiological traits in herbs.We conclude that leaf embolism resistance and SSM are adaptively relevant traits associated with the phenological differentiation of temporally disjunct herbaceous species. The association of leaf embolism resistance and phenology has implications for herbaceous community adaptation to changing climates. 

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3. Tree functional traits across Caribbean island dry forests are remarkably similar

   https://doi.org/10.1111/jbi.14743  

   Lopez‐Bustamante, Pablo; Rosa‐Santiago, Alanis; Hulshof, Catherine M.; Franklin, Janet (October 2023, Journal of Biogeography)

   Abstract AimTo examine the climatic and biogeographic drivers of plant trait variation across Caribbean tropical dry forests, a system characterised by high rates of plant endemism despite low moisture availability, high rainfall variability and persistent exposure to hurricanes. LocationCaribbean tropical dry forests. TaxonWoody plants. MethodsWe used a database of 572 woody vegetation plots spanning across the Caribbean, including Florida. We then extracted seed mass, specific leaf area and wood density from global trait databases. We supplemented additional trait data from herbaria collections and calculated phylogenetic imputation of traits. Furthermore, we calculated presence–absence community means and functional diversity and correlated these metrics with bioclimatic variables in addition to island and dry forest area using generalised additive models. ResultsDespite occurring in climatically distinct regions, Caribbean tropical dry forests are functionally similar, and the trait space of many dry forests are nested within the functional space of others. In line with island biogeographic theory, island area, dry forest area and island isolation were correlated with functional diversity. Although temperature and precipitation were important determinants of trait variation and functional diversity, environmental variables differently impacted trait variation and the variance explained was generally low. Main ConclusionsThe high functional overlap among Caribbean dry forests is remarkable given the broad climatic gradient across these islands. High functional overlap suggests that environmental and biogeographic filters constrain plant form and function in these intrinsically fascinating systems. The trait space of these insular dry forest systems points to dispersal‐limitation, in addition to high temperature and water limitations, and favouring persistence strategies to withstand high frequency hurricane disturbance. 

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4. Traits of dominant plant species drive normalized difference vegetation index in grasslands globally

   https://doi.org/10.1111/geb.13644  

   Engel, Thore; Bruelheide, Helge; Hoss, Daniela; Sabatini, Francesco M; Altman, Jan; Arfin‐Khan, Mohammed_A S; Bergmeier, Erwin; Černý, Tomáš; Chytrý, Milan; Dainese, Matteo; et al (May 2023, Global Ecology and Biogeography)

   Abstract AimTheoretical, experimental and observational studies have shown that biodiversity–ecosystem functioning (BEF) relationships are influenced by functional community structure through two mutually non‐exclusive mechanisms: (1) the dominance effect (which relates to the traits of the dominant species); and (2) the niche partitioning effect [which relates to functional diversity (FD)]. Although both mechanisms have been studied in plant communities and experiments at small spatial extents, it remains unclear whether evidence from small‐extent case studies translates into a generalizable macroecological pattern. Here, we evaluate dominance and niche partitioning effects simultaneously in grassland systems world‐wide. LocationTwo thousand nine hundred and forty‐one grassland plots globally. Time period2000–2014. Major taxa studiedVascular plants. MethodsWe obtained plot‐based data on functional community structure from the global vegetation plot database “sPlot”, which combines species composition with plant trait data from the “TRY” database. We used data on the community‐weighted mean (CWM) and FD for 18 ecologically relevant plant traits. As an indicator of primary productivity, we extracted the satellite‐derived normalized difference vegetation index (NDVI) from MODIS. Using generalized additive models and deviation partitioning, we estimated the contributions of trait CWM and FD to the variation in annual maximum NDVI, while controlling for climatic variables and spatial structure. ResultsGrassland communities dominated by relatively tall species with acquisitive traits had higher NDVI values, suggesting the prevalence of dominance effects for BEF relationships. We found no support for niche partitioning for the functional traits analysed, because NDVI remained unaffected by FD. Most of the predictive power of traits was shared by climatic predictors and spatial coordinates. This highlights the importance of community assembly processes for BEF relationships in natural communities. Main conclusionsOur analysis provides empirical evidence that plant functional community structure and global patterns in primary productivity are linked through the resource economics and size traits of the dominant species. This is an important test of the hypotheses underlying BEF relationships at the global scale. 

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5. Trait velocities reveal that mortality has driven widespread coordinated shifts in forest hydraulic trait composition

   https://doi.org/10.1073/pnas.1917521117  

   Trugman, Anna T.; Anderegg, Leander D.; Shaw, John D.; Anderegg, William R. (April 2020, Proceedings of the National Academy of Sciences)

   Understanding the driving mechanisms behind existing patterns of vegetation hydraulic traits and community trait diversity is critical for advancing predictions of the terrestrial carbon cycle because hydraulic traits affect both ecosystem and Earth system responses to changing water availability. Here, we leverage an extensive trait database and a long-term continental forest plot network to map changes in community trait distributions and quantify “trait velocities” (the rate of change in community-weighted traits) for different regions and different forest types across the United States from 2000 to the present. We show that diversity in hydraulic traits and photosynthetic characteristics is more related to local water availability than overall species diversity. Finally, we find evidence for coordinated shifts toward communities with more drought-tolerant traits driven by tree mortality, but the magnitude of responses differs depending on forest type. The hydraulic trait distribution maps provide a publicly available platform to fundamentally advance understanding of community trait change in response to climate change and predictive abilities of mechanistic vegetation models. 

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