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Abstract Forests sequester a substantial portion of anthropogenic carbon emissions. Many open questions concern how. We address two of these questions. Has leaf and fine litter production changed? And what is the contribution of old‐growth forests? We address these questions with long‐term records (≥10 years) of total, reproductive, and especially foliar fine litter production from 32 old‐growth forests. We expect increases in forest productivity associated with rising atmospheric carbon dioxide concentrations and, in cold climates, with rising temperatures. We evaluate the statistical power of our analysis using simulations of known temporal trends parameterized with sample sizes (in number of years) and levels of interannual variation observed for each record. Statistical power is inadequate to detect biologically plausible trends for records lasting less than 20 years. Modest interannual variation characterizes fine litter production, and more variable phenomena will require even longer records to evaluate global change responses with sufficient statistical power. Just four old‐growth forests have records of fine litter production lasting longer than 20 years, and these four provide no evidence for increases. Three of the four forests are in central Panama, also have long‐term records of wood production, and both components of aboveground production are unchanged over 21–38 years. The possibility that recent increases in forest productivity are limited for old‐growth forests deserves more attention. 

Abstract Predicting tropical tree demography is a key challenge in understanding the future dynamics of tropical forests. Although demographic processes are known to be regulated by leaf trait diversity, only the effect of inter‐specific trait variation has been evaluated, and it remains unclear as to what degree the intra‐specific trait plasticity across light gradients (hereafter light plasticity) regulates tree demography, and how this will further shape long‐term community and ecosystem dynamics. By combining in situ trait measurements and forest census data with a terrestrial biosphere model, we evaluated the impact of observation‐constrained light plasticity on demography, forest structure, and biomass dynamics in a Panamanian tropical moist forest. Modeled leaf physiological traits vary across and within plant functional types (PFT), which represent the inter‐specific trait variation and the intra‐specific light plasticity, respectively. The simulation using three non‐plastic PFTs underestimated 20‐year average understory growth rates by 41%, leading to a biased forest size structure and leaf area profile, and a 44% underestimate in long‐term biomass. The simulation using three plastic PFTs generated accurate understory growth rates, resulting in a realistic forest structure and a smaller biomass underestimate of 15%. Expanding simulated trait diversity using 18 nonplastic PFTs similarly improved the prediction of demography and biomass. However, only the plasticity‐enabled model predicted realistic long‐term PFT composition and within‐canopy trait profiles. Our results highlight the distinct role of light plasticity in regulating forest dynamics that cannot be replaced by inter‐specific trait diversity. Accurately representing light plasticity is thus crucial for trait‐based prediction of tropical forest dynamics. 

The Barro Colorado Nature Monument in Panama, which includes Barro Colorado Island and nearby mainland peninsulas, supports the best studied tropical forest in the world. This 98-chapter edited volume reviews the history and contributions of research undertaken at this moist tropical forest to advance our understanding of tropical plants and ecosystems. The first section describes the setting, including soils, land use history, forest structure, and plant species composition. Nine additional sections concern plant reproduction and seedling regeneration, plant physiology, plant community ecology, population genetics, interactions with microbes and herbivores, remote sensing, observational ecosystem studies, experimental ecosystem studies, and focal taxa and functional group accounts. The authoritative reviews in this volume provide a foundation for future research in this and other tropical forest sites. 

ABSTRACT Examining the cues and drivers influencing seed production is crucial to better understand forest resilience to climate change. We explored the effects of five climatic variables on seed production over 22 years in an everwet Amazonian forest, by separating direct effects of these variables from indirect effects mediated through flower production. We observed a decline in seed production over the study period, which was primarily explained by direct effects of rising nighttime temperatures and declining average vapour pressure deficits. Higher daytime temperatures were positively related to seed output, mainly through a flower‐mediated effect, while rainfall effects on seed production were more nuanced, showing either positive or negative relationships depending on the seasonal timing of rains. If these trends continue, they are likely to lead to significant changes in forest dynamics, potentially impacting both forest structure and species composition. 

We provide data on mean dry and wet mass of > 800 species from Yasuní National Forest, Ecuador collected between 2000 and 2014. Species include trees, shrubs, lianas and herbs. We also provide data on number of seeds per fruit for >1100 species compiled in 2016, along with information on fruit type and dispersal mode. Both of these data sets supplement previously published data on flowering and fruiting phenology from this equatorial, ever-wet rainforest in eastern Ecuador (Garwood et al. 2023). Garwood, N.C., S.J. Wright, R. Valencia, and M.R. Metz. 2023. Rainforest phenology: flower, fruit and seed production from biweekly collections of 200 traps in the Yasuní Forest Dynamics Plot, Ecuador, 2000-2018 ver 1. Environmental Data Initiative. https://doi.org/10.6073/pasta/5e6cb3d7ff741fd9d21965c4a904bc1f (Accessed 2024-03-27). 

Forests sequester a substantial portion of anthropogenic carbon emissions. Many open questions concern how. We address two of these questions (Wright and Calderón 2025). Has leaf and fine litter production changed? And what is the contribution of old-growth forests? We address these questions with long-term records (≥10 years) of total, reproductive, and especially foliar fine litter production from 32 old-growth forests. We expect increases in forest productivity associated with rising atmospheric carbon dioxide concentrations and, in cold climates, with rising temperatures. We evaluate the statistical power of our analysis using simulations of known temporal trends parameterized with sample sizes (number of years) and levels of interannual variation observed for each record. Statistical power is inadequate to detect biologically plausible trends for records lasting less than 20 years. Just four old-growth forests have records of fine litter production lasting longer than 20 years, and these four provide no evidence for increases. Three of the four forests are in central Panama, also have long-term records of wood production, and both components of aboveground production are unchanged over 21 to 38 years. The possibility that recent increases in forest productivity are limited for old-growth forests deserves more attention. Modest interannual variation characterizes fine litter production, and more variable phenomena will require even longer records to evaluate global change responses with sufficient statistical power. The data files and R scripts in this data package recreate the analyses of Wright and Calderón (2025). References Wright, S. J. and O. Calderón. 2025. Statistical power and the detection of global change responses: The case of leaf production in old-growth forests. Ecology (accepted 28 October 2024; manuscript ECY23-1254.R1) 

Forests sequester a substantial portion of anthropogenic carbon emissions. Many open questions concern how. We address two of these questions. Has leaf and fine litter production changed? And what is the contribution of old-growth forests? We address these questions with long-term records (≥10 years) of total, reproductive, and especially foliar fine litter production from 32 old-growth forests. We expect increases in forest productivity associated with rising atmospheric carbon dioxide concentrations and, in cold climates, with rising temperatures. We evaluate the statistical power of our analysis using simulations of known temporal trends parameterized with sample sizes (number of years) and levels of interannual variation observed for each record. Statistical power is inadequate to detect biologically plausible trends for records lasting less than 20 years. Modest interannual variation characterizes fine litter production. More variable phenomena will require even longer records to evaluate global change responses with sufficient statistical power.  Just four old-growth forests have records of fine litter production lasting longer than 20 years, and these four provide no evidence for increases. Three of the four forests are in central Panama, also have long-term records of wood production, and both components of aboveground production are unchanged over 21 to 38 years. The possibility that recent increases in forest productivity are limited for old-growth forests deserves more attention. This data package contains previously unpublished data from four old-growth forests in central Panama. Data compiled from the published literature for another 28 forests and the R scripts required to recreate our analyses can be found here: https://smithsonian.dataone.org/view/urn:uuid:8bbcd334-059b-45b1-9b83-94b52abbd6f8. 

Fine roots are key to ecosystem-scale nutrient, carbon (C), and water cycling, yet our understanding of fine root trait variation within and among tropical forests, one of Earth’s most C-rich ecosystems, is limited. We characterized root biomass, morphology, nutrient content, and arbuscular mycorrhizal fungal (AMF) colonization to 1.2 m depths across four distinct lowland Panamanian forests, and related root characteristics to soil C stocks. We hypothesized that: (H1) Fine root characteristics vary consistently with depth across seasonal tropical forests, with deeper roots exhibiting more exploratory traits, such as for deep water acquisition; (H2) fine root characteristics vary among tropical forests mainly in surface soils, where resource availability also varies. We found consistent variation with depth across the four forests, including decreased root biomass, root tissue density, and AMF, and increased specific root length. Among the forests, there was variation in some fine root characteristics, including greater surface root biomass and lower SRL in the wettest forest, and smaller fine root diameter in the driest forest. We also found that root characteristics were related to total soil C stocks, which were positively related to root biomass and negatively related to specific root length. These results indicate emergent properties of root variation with depth across tropical forests, and show site-scale variation in surface root characteristics. Future work could explore the flexibility in root characteristics under changing conditions such as drought. 

Summary Climate models predict that everwet western Amazonian forests will face warmer and wetter atmospheric conditions, and increased cloud cover. It remains unclear how these changes will impact plant reproductive performance, such as flowering, which plays a central role in sustaining food webs and forest regeneration. Warmer and wetter nights may cause reduced flower production, via increased dark respiration rates or alteration in the reliability of flowering cue‐based processes. Additionally, more persistent cloud cover should reduce the amounts of solar irradiance, which could limit flower production.We tested whether interannual variation in flower production has changed in response to fluctuations in irradiance, rainfall, temperature, and relative humidity over 18 yrs in an everwet forest in Ecuador.Analyses of 184 plant species showed that flower production declined as nighttime temperature and relative humidity increased, suggesting that warmer nights and greater atmospheric water saturation negatively impacted reproduction. Species varied in their flowering responses to climatic variables but this variation was not explained by life form or phylogeny.Our results shed light on how plant communities will respond to climatic changes in this everwet region, in which the impacts of these changes have been poorly studied compared with more seasonal Neotropical areas.