About

James W Dalling is a Professor of Plant Biology at the University of Illinois, with additional appointments at the Center for Latin American and Caribbean Studies and the Center for Global Studies. He holds a B.A. from Oxford University (1988) and a Ph.D. from Cambridge University (1992). His research focuses on tropical forest dynamics, particularly the population and community ecology of tropical forests. He investigates how soil nutrient availability and soil microbial communities influence the composition and diversity of tree communities. Much of his research is conducted in collaboration with the Smithsonian Tropical Research Institute in Panama, where he serves as a Research Associate Scientist. His fieldwork is primarily based on Barro Colorado Island in the Panama Canal Watershed, as well as the Fortuna Forest Reserve and Volcan Barú in western Panama, where he has established and maintains a network of forest dynamics plots spanning a wide range of soil nutrient availabilities and elevations from 700 to 3200 meters. Current projects in his lab explore seed-infecting fungi as a model system to understand plant-pathogen interactions and plant defense traits, the role of soil nutrient availability in structuring tree communities and plant functional traits, and the role of wood nutrients as a nutrient store in nutrient-poor soils and as a determinant of wood decomposer community composition and decay rate. Professor Dalling has been recognized as a Delcomyn Professorial Scholar and has held visiting fellowships at Magdalen College, Oxford, and St John's College, Cambridge.

Research topics

• Biology
• Ecology
• Geography
• Geology
• Environmental science
• Sociology
• Atmospheric sciences
• Remote sensing
• Meteorology
• Materials science
• Botany
• Oceanography

Selected publications

• A handbook for standardised measurements of plant reproductive traits: from pollen grain to seedling

  Australian Journal of Botany · 2026-01-20 · 5 citations

  article

  A lack of standardised sampling protocols prevents functional traits from expressing their full potential to advance plant ecology, biogeography, and evolutionary biology. Handbooks providing protocols for standardised measurements of plant functional traits allow researchers to tackle large-scale ecological questions but have traditionally focused on vegetative traits such as leaves, stems and roots. This handbook provides standardised protocols for 58 reproductive traits of flowers (10 traits), fruits (6 traits), seeds (36 traits) and seedlings (6 traits). It is the first effort to standardise sampling for relevant reproductive traits to better understand processes, such as pollination, frugivory, seed dispersal, seed longevity, germination, and seedling establishment. The protocols were designed to embrace the global diversity of ecological contexts experienced by flowers, fruits, seeds, and seedlings and incorporate methods for temperate to tropical, dry to moist and fire-prone to fire-sensitive ecosystems. We offer general guidelines for sampling, storing, and processing reproductive traits. Before laying out the protocol, we briefly describe each trait functionality, trade-offs, and sources of variability to give a broad context. Standardised protocols to estimate reproductive plant traits will unlock the full potential of plants to mitigate land-use and climate-change impacts, and support restoration of degraded ecosystems.

  PublisherDOI

• Getting by with a little help from fungal friends: seed endophytes contribute to seed defense against fungal pathogens in keystone tropical trees

  2026-01-02

  articleOpen access

  1. Soil-borne fungal pathogens are known to be major causes of seed mortality in tropical forests; however, not all fungal infections of seeds are necessarily lethal. It has been hypothesized that the seed microbiome may contribute to seed defense and persistence in soil seed banks and is especially important for non-dormant seeds with limited physical and chemical defenses. 2. This study examined microbially mediated seed defense in two fig (Ficus) species from a tropical forest in the Western Ghats, India. One species, Ficus callosa has a free-standing habit, and the other, Ficus beddomei is a hemi-epiphyte (seeds germinate in the canopy of host trees and send roots to soil). We inoculated seeds using pre-dispersal and soil-borne seed fungal isolates obtained from the same fig species, classified their effects as endophytic or pathogenic, then tested the effect of pre-treatment of seeds with endophytes before exposure to pathogens. 3. We predicted that (i) fungi infecting seeds prior to dispersal will have less negative effects on survival compared to soil-borne fungi (ii) the hemi-epiphytic figs are more susceptible to soil borne fungi, and (iii) prior infection by non-pathogenic, pre-dispersal and soil-borne endophytic fungi excludes pathogens and increases seed survival. 4. We found that inoculation with pre-dispersal fungal taxa did not affect seed germination for either fig species, while the soil borne fungi were frequently pathogenic, especially in the hemi-epiphytic fig. Incubation with endophytic fungi prior to pathogen exposure increased seed survival depending on endophyte and pathogen identities, and was more likely to occur in the free-standing fig. 5. Synthesis: Our findings show that prior seed infection by endophytes could be a plausible mechanism of seed defense against fungal pathogens. It highlights the potential for dynamic seed-fungal interactions to increase seed survival, with implications for tree populations and diversity in tropical forests.

  PublisherOA PDFDOI

• Germination data for inoculation experiments involving Ficus seeds and fungal taxa isolated from these seeds

  Open MIND · 2026-01-01

  dataset

  This dataset contains seed germination data from two inoculation experiments involving two fig species, Ficus beddomei and Ficus callosa, found in the tropical forests of the Western Ghats, India, and fungal taxa that were isolated from them. The file "first_inoculation_expt_Nov_2025" contains germination data for screening of select fungal taxa for their effects on the two fig species. The file "serial_inoculation_expt_Nov_2025" contains germination data from a serial inoculation experiment involving successive inoculation of seeds with an endophytic followed by a pathogenic fungal taxon.

  DOI

• Functional traits of ectomycorrhizal trees influence surrounding soil organic matter properties

  Functional Ecology · 2025-04-24 · 3 citations

  articleOpen access

  Abstract Ectomycorrhizal (EM) effects on forest ecosystem carbon (C) and nitrogen (N) cycling are highly variable, which may be due to underappreciated functional differences among EM‐associating trees. We hypothesise that differences in functional traits among EM tree genera will correspond to differences in soil organic matter (SOM) dynamics. We explored how differences among three genera of angiosperm EM trees ( Quercus , Carya , and Tilia ) in functional traits associated with leaf litter quality, resource use and allocation patterns, and microbiome assembly related to overall soil biogeochemical properties. We found consistent differences among EM tree genera in functional traits. Quercus trees had lower litter quality, lower δ 13 C in SOM, higher δ 15 N in leaf tissues, greater oxidative extracellular enzyme activities, and higher EM fungal diversity than Tilia trees, while Carya trees were often intermediary. These functional traits corresponded to overall SOM‐C and N dynamics and soil fungal and bacterial community composition. Our findings suggest that trait variation among EM‐associating tree species should be an important consideration in assessing plant–soil relationships such that EM trees cannot be categorised as a unified functional guild. Read the free Plain Language Summary for this article on the Journal blog.

  PublisherOA PDFDOI

• Mycorrhizal Barriers to the Upslope Migration of Tropical Trees

  Biotropica · 2025-09-01 · 1 citations

  articleOpen access1st authorCorresponding

  ABSTRACT Mycorrhizae can impact soil nutrient cycling, with reduced nitrogen availability and increased litter depth beneath ectomycorrhizal Fagales. The presence of Fagales‐dominated montane forests in parts of Asia and Central America could impose a significant barrier to the upslope migration of lowland arbuscular mycorrhizal tree species migrating under climate change.

  PublisherOA PDFDOI

• Life history is a key driver of temporal fluctuations in tropical tree abundances

  Proceedings of the National Academy of Sciences · 2025-01-24 · 5 citations

  articleOpen access

  The question of what mechanisms maintain tropical biodiversity is a critical frontier in ecology, intensified by the heightened risk of biodiversity loss faced in tropical regions. Ecological theory has shed light on multiple mechanisms that could lead to the high levels of biodiversity in tropical forests. But variation in species abundances over time may be just as important as overall biodiversity, with a more immediate connection to the risk of extirpation and biodiversity loss. Despite the urgency, our understanding of the primary mechanisms driving fluctuations in species abundances has not been clearly established. Here, we introduce a theoretical framework based around life history; the schedule of birth, growth, and mortality over a lifespan, and its systematic variation across species. We develop a mean field model to predict expected fluctuations in abundance for a focal species in a larger community, and we quantify empirical life history variation among 90 tropical forest species in a 50 ha plot in Panama. Putting theory and data together, we show that life history provides a critical piece of this puzzle, allowing us to explain patterns of abundance fluctuations more accurately than previous models incorporating demographic stochasticity without life history variation, and without introducing unobserved couplings between species and their environment. This framework provides a starting point for more general models that incorporate multiple factors in addition to life history variation, and suggests the potential for a fine-grained assessment of extirpation risk based on the impacts of anthropogenic change on demographic rates across life stages.

  PublisherDOI

• Soil and biomass carbon storage is much higher in Central American than Andean montane forests

  Biogeosciences · 2025-07-29 · 2 citations

  articleOpen accessSenior authorCorresponding

  Abstract. Tropical montane forests (TMFs) play a key role in the global carbon (C) cycle and in climate regulation by sequestering large amounts of aboveground and belowground carbon. Elevation gradients in TMFs have helped reveal the influence of environmental factors on C stocks. Few studies have evaluated the influence of elevation and soil nutrient availability on C stocks in the context of mixed ectomycorrhizal (EM) and non-EM-associated forests in the neotropics, especially in the mountains. We estimated aboveground biomass (AGB), coarse wood debris (CWD), and soil C based on field inventories in ten 1 ha plots along an elevational gradient from 880 to 2920 ma.s.l. varying in relative abundance of EM trees in western Panama. Trees with ≥ 10 cm diameter at breast height (DBH) and CWD with ≥ 10 cm diameter were measured to calculate biomass and necromass. Soil C to 1 m depth was estimated. Furthermore, climate and edaphic characteristics were described for each plot to evaluate the influence on these variables on each C pool. AGB, downed CWD, and soil C were strongly positively correlated with elevation. We found exceptionally high AGB up to 574.3 Mg ha−1 and soil C up to 577.9 Mg ha−1 at higher elevations. After controlling for elevation, neither nutrient availability nor EM dominance had an effect on AGB or soil C. Nonetheless, high AGB at high elevations was attributed to the presence of Quercus species. We found previous lidar-derived estimates for our site substantially underestimated the aboveground carbon (AGC) present in the plots, being between 2 and 6 times lower than our field-based estimates. Remarkably high soil C at high elevations might be a consequence of reduced decomposition rates associated with lower temperature, or geological history, where repeated volcanic eruptions buried surface soil organic layers. Our results highlight large regional uncertainty in C pool estimates in neotropical montane forests, with potentially large underestimates for Central American C stocks.

  PublisherOA PDFDOI

• Nitrogen addition alters interactions between ectomycorrhizal host trees and fungal communities in a mixed mycorrhizal tropical rainforest

  Plant and Soil · 2025-03-04 · 3 citations

  article
  PublisherDOI

• Seed survival in tropical pioneer trees is unrelated to conspecific distance but linked to fungal infection

  Oikos · 2025-10-20

  article

  Plant demography is heavily influenced by individual survival at local scales, with host‐specific natural enemies potentially reducing the survival of seeds and seedlings in high density patches near conspecific adults, favoring heterospecific recruitment, and ultimately increasing local plant diversity. Natural enemy pressure should differ 1) between sites directly beneath and away from their hosts' crowns, 2) between sites where their hosts are abundant versus rare, and 3) among potentially competing plant species. Assessing the potential pathways by which natural enemies affect diversity at local scales requires coupling experimental approaches that track plant performance with characterization of their natural enemy communities. Here, we focused on the fate of individuals at the seed stage, a critical demographic bottleneck in the plant life cycle. We tested how seed germination is affected by fungal infection, distance from the adult tree, burial duration, and host tree identity. We conducted a seed burial experiment on Barro Colorado Island, Panama, using four pioneer tree species ( Jacaranda copaia , Cecropia insignis , C. peltata and C. longipes ). Seeds were buried beneath and 30 m away from adult C. insignis and J. copaia trees and retrieved after 3 and 12 months. We measured germination, cultured seed‐infecting fungi, and evaluated fungal communities using a culture‐independent approach. Germination rates of all tree species declined with burial time. Germination of seeds buried below versus away from focal trees also did not differ. Fungal isolation frequency and richness increased after burial but did not change with distance or identity of the adult tree. Fungal communities in seeds differed markedly among tree species, but distance, burial duration, and seed viability status had little effect on community composition. Consequently, we found limited evidence that distance from conspecifics drives seed mortality in the soil. Nonetheless, seed exposure to the soil increases fungal infections and decreases seed survival, highlighting the role of fungi in seed demography. We recommend that future research explore the mechanisms by which host‐generalist soilborne fungi may drive seed mortality in plant communities.

  PublisherDOI

• Homogenization of a temperate old-growth forest remnant in central Illinois following the introduction of Dutch elm disease (Ophiostoma novo-ulmi) and emerald ash borer (Agrilus planipennis)

  Forest Ecology and Management · 2025-04-08 · 1 citations

  articleOpen access

  Forests in the eastern United States are undergoing wide-scale transformations driven by the combined effects of biological and anthropogenic factors. Understanding how these drivers interact to affect forest dynamics is important for predicting the resilience of forest ecosystem services, but few long-term records exist for old-growth forests that have not been directly altered by humans. In this study, we utilized historical datasets covering a 96-year period to investigate temporal changes in forest structure and composition at Trelease Woods, an old-growth temperate forest remnant in central Illinois. Our objectives were to (1) characterize shifts in forest composition and structure, and (2) determine how tree mortality due to biotic invasions may have affected the dynamics. Our findings documented substantial compositional changes across the different census periods. Species richness and diversity both declined over time, with saplings exhibiting markedly lower diversity values. The relative densities and basal areas of sugar maple ( Acer saccharum L.) and Ohio buckeye ( Aesculus glabra ) increased across the sapling (< 10 cm) and mid-sized (10–50.7 cm) strata, while the overstory (> 50.7 cm) has become heavily dominated by sugar maple since 1936. These observed temporal trends suggest that Trelease Woods is experiencing species homogenization likely driven by tree mortality associated with pest and pathogen outbreaks, rising deer populations, and mesophication due to fire suppression. These findings provide insights into the historical compositional and structural shifts that temperate forests in the eastern U.S. have undergone over the past century and the potential implications for future changes in dynamics of old-growth forests in eastern North America. • Analyzed 96 years of temporal changes in structure and composition. • Evidence of species homogenization, especially in the sapling layer. • Species richness and diversity declined throughout all strata. • Sugar maple and Ohio buckeye dominance increased across all size classes. • Elm and ash density, basal area, and importance declined rapidly.

  PublisherDOI

Recent grants

• DISSERTATION RESEARCH: The influence of soil fertility on tropical tree species carbon and nutrient storage: A comparison between lowland and montane forests

  NSF · $20k · 2013–2015

• Collaborative Research: Seed defense syndromes of tropical forest trees: emergent properties of seed dormancy, defense and microbial interactions

  NSF · $378k · 2011–2016

• Collaborative Research: Effects of Soil-Borne Resources on the Structure and Dynamics of Lowland Tropical Forests

  NSF · $179k · 2002–2007

• RAPID: Acquisition of high resolution LiDAR for Barro Colorado Nature Monument, Panama

  NSF · $62k · 2009–2010

Frequent coauthors

• Stephen P. Hubbell

  University of California, Los Angeles

  62 shared

• Paul‐Camilo Zalamea

  58 shared

• Benjamin L. Turner

  Gyeongsang National University

  55 shared

• David F. R. P. Burslem

  University of Aberdeen

  39 shared

• Carolina Sarmiento

  Front Range Scientific Computations

  38 shared

• Kyle E. Harms

  34 shared

• Adam S. Davis

  University of Illinois Urbana-Champaign

  34 shared

• Jérôme Chave

  Institut de Recherche pour le Développement

  33 shared

Education

• PhD, Plant Sciences

  University of Cambridge

  1992

• BA, Plant Sciences

  University of Oxford

  1988

Awards & honors

• Delcomyn Professorial Scholar
• Visiting Fellow, Magdalen College, Oxford
• Beaufort Visiting Fellow, St John's College, Cambridge