Chain of events analysis in diving accidents treated by the Royal Netherlands Navy 1966-2023.

Introduction: Diving injuries are influenced by a multitude of factors. Literature analysing the full chain of events in diving accidents influencing the occurrence of diving injuries is limited. A previously published 'chain of events analysis' (CEA) framework consists of five steps that may sequentially lead to a diving fatality. This study applied four of these steps to predominately non-lethal diving injuries and aims to determine the causes of diving injuries sustained by divers treated by the Diving Medical Centre of the Royal Netherlands Navy. Methods: This retrospective cohort study was performed on diving injuries treated by the Diving Medical Centre between 1966 and 2023. Baseline characteristics and information pertinent to all four steps of the reduced CEA model were extracted and recorded in a database. Results: A total of 288 cases met the inclusion criteria. In 111 cases, all four steps of the CEA model could be applied. Predisposing factors were identified in 261 (90%) cases, triggers in 142 (49%), disabling agents in 195 (68%), and 228 (79%) contained a (possible-) disabling condition. The sustained diving injury led to a fatality in seven cases (2%). The most frequent predisposing factor was health conditions (58%). Exertion (19%), primary diver errors (18%), and faulty equipment (17%) were the most frequently identified triggers. The ascent was the most frequent disabling agent (52%). Conclusions: The CEA framework was found to be a valuable tool in this analysis. Health factors present before diving were identified as the most frequent predisposing factors. Arterial gas emboli were the most lethal injury mechanism.

Breakdown of the growth-mortality trade-off along a soil phosphorus gradient in a diverse tropical forest.

An ecological paradigm predicts that plant species adapted to low resource availability grow slower and live longer than those adapted to high resource availability when growing together. We tested this by using hierarchical Bayesian analysis to quantify variations in growth and mortality of ca 40 000 individual trees from greater than 400 species in response to limiting resources in the tropical forests of Panama. In contrast to theoretical expectations of the growth-mortality paradigm, we find that tropical tree species restricted to low-phosphorus soils simultaneously achieve faster growth rates and lower mortality rates than species restricted to high-phosphorus soils. This result demonstrates that adaptation to phosphorus limitation in diverse plant communities modifies the growth-mortality trade-off, with important implications for understanding long-term ecosystem dynamics.

Assessing the Role of Systems Thinking for Stocker Cattle Operations.

Bovine respiratory disease (BRD) is recognized as a complex multifactorial disease often resulting in significant economic losses for the stocker industry through reduced health and performance of feeder calves. Conventional approaches to manage BRD in stocker production systems can be challenged with a restricted view of the system, most importantly the structure, which drives the behavior of the system and fails to anticipate unintended consequences. The translation and implementation of systems thinking into veterinary medicine can offer an alternative method to problem-solving. Fundamental to the success of the systems thinker is the conceptualization of the Iceberg Diagram intended to identify root causes of complex problems such as BRD. Furthermore, veterinary and animal health professionals are well-positioned to serve as facilitators to establish creative tension, the positive energy necessary to identify high-leverage strategies. The interrelationships and interconnected behaviors of complex stocker systems warrant an understanding of various archetypes. Archetypes provide the systems thinker with a decision-making tool to explore tactics in a nonlinear fashion for the purpose of recognizing short- and long-term outcomes. Developing literacy in the discipline of systems thinking will further equip professionals with the skillset necessary to address the multitude of challenges ingrained in complex stocker cattle systems.

Beef Production Health Systems: Perspectives of a Trained Systems Thinker.

Managing beef cattle health across a segmented production and marketing system can be thought of as a perplexing problem due to the counterintuitive responses of the system to existing management strategies. The process of thinking in systems to recognize and develop systems thinking archetypes is emphasized. The 2 cases discussed are brought together to explore deeper but often unrecognized structure that contributes to reinforcing problematic behavior, the structure of mental models. Training in systems thinking and system dynamics modeling equips the scientist to translate within and between scientific disciplines, a much-needed skill for addressing current and emerging beef production problems.

Enhancing Phytate Availability in Soils and Phytate-P Acquisition by Plants: A Review.

Phytate (myo-inositol hexakisphosphate salts) can constitute a large fraction of the organic P in soils. As a more recalcitrant form of soil organic P, up to 51 million metric tons of phytate accumulate in soils annually, corresponding to ∼65% of the P fertilizer application. However, the availability of phytate is limited due to its strong binding to soils via its highly-phosphorylated inositol structure, with sorption capacity being ∼4 times that of orthophosphate in soils. Phosphorus (P) is one of the most limiting macronutrients for agricultural productivity. Given that phosphate rock is a finite resource, coupled with the increasing difficulty in its extraction and geopolitical fragility in supply, it is anticipated that both economic and environmental costs of P fertilizer will greatly increase. Therefore, optimizing the use of soil phytate-P can potentially enhance the economic and environmental sustainability of agriculture production. To increase phytate-P availability in the rhizosphere, plants and microbes have developed strategies to improve phytate solubility and mineralization by secreting mobilizing agents including organic acids and hydrolyzing enzymes including various phytases. Though we have some understanding of phytate availability and phytase activity in soils, the limiting steps for phytate-P acquisition by plants proposed two decades ago remain elusive. Besides, the relative contribution of plant- and microbe-derived phytases, including those from mycorrhizas, in improving phytate-P utilization is poorly understood. Hence, it is important to understand the processes that influence phytate-P acquisition by plants, thereby developing effective molecular biotechnologies to enhance the dynamics of phytate in soil. However, from a practical view, phytate-P acquisition by plants competes with soil P fixation, so the ability of plants to access stable phytate must be evaluated from both a plant and soil perspective. Here, we summarize information on phytate availability in soils and phytate-P acquisition by plants. In addition, agronomic approaches and biotechnological strategies to improve soil phytate-P utilization by plants are discussed, and questions that need further investigation are raised. The information helps to better improve phytate-P utilization by plants, thereby reducing P resource inputs and pollution risks to the wider environment.

ASAS-NANP Symposium: Mathematical Modeling in Animal Nutrition: Opportunities and challenges of confined and extensive precision livestock production.

Modern animal scientists, industry, and managers have never faced a more complex world. Precision livestock technologies have altered management in confined operations to meet production, environmental, and consumer goals. Applications of precision technologies have been limited in extensive systems such as rangelands due to lack of infrastructure, electrical power, communication, and durability. However, advancements in technology have helped to overcome many of these challenges. Investment in precision technologies is growing within the livestock sector, requiring the need to assess opportunities and challenges associated with implementation to enhance livestock production systems. In this review, precision livestock farming and digital livestock farming are explained in the context of a logical and iterative five-step process to successfully integrate precision livestock measurement and management tools, emphasizing the need for precision system models (PSMs). This five-step process acts as a guide to realize anticipated benefits from precision technologies and avoid unintended consequences. Consequently, the synthesis of precision livestock and modeling examples and key case studies help highlight past challenges and current opportunities within confined and extensive systems. Successfully developing PSM requires appropriate model(s) selection that aligns with desired management goals and precision technology capabilities. Therefore, it is imperative to consider the entire system to ensure that precision technology integration achieves desired goals while remaining economically and managerially sustainable. Achieving long-term success using precision technology requires the next generation of animal scientists to obtain additional skills to keep up with the rapid pace of technology innovation. Building workforce capacity and synergistic relationships between research, industry, and managers will be critical. As the process of precision technology adoption continues in more challenging and harsh, extensive systems, it is likely that confined operations will benefit from required advances in precision technology and PSMs, ultimately strengthening the benefits from precision technology to achieve short- and long-term goals.

Interest and investment in precision technologies are growing within the livestock sector. Though these technologies offer many promises of increased efficiency and reduced inputs, there is a need to assess the opportunities and challenges associated with precision technology implementation in livestock production systems. In this review, precision livestock measurement and management tools are explained in the context of a logical and iterative five-step process that highlights the need for systems computer modeling to realize anticipated benefits from these technologies and avoid unintended consequences. This review includes key case studies to highlight past challenges and current opportunities within operations that house animals in a central area or building with sufficient infrastructure (confined livestock production systems) and other operation settings that utilize large grasslands that contain far less infrastructure (extensive livestock production systems). The key to precision livestock management success is training the next generation of animal scientists in computer modeling, precision technologies, computer programming, and data science while still being grounded in traditional animal science principles.

Novel phytase PvPHY1 from the As-hyperaccumulator Pteris vittata enhances P uptake and phytate hydrolysis, and inhibits As translocation in Plant.

Developing P-efficient plants helps improve P uptake from soils with low-available P and reduce environmental damage by P runoff. Here, we investigated a novel root-specific phytase PvPHY1 from As-hyperaccumulator Pteris vittata, which can efficiently utilize phytate, a recalcitrant organic phosphorus in soil. Unlike other plants, expression of PvPHY1 in P. vittata was greater in the roots than the fronds. A pure phytase with considerable activity was obtained via prokaryotic expression. Expressing PvPHY1 in tobacco (PvPHY1-Ex) enhanced its growth (2.8 to 3.5-3.9 g per plant) and increased its P accumulation by 10-50% under low- and adequate-P conditions. Further, PvPHY1-Ex tobacco showed 25-32% lower intracellular phytate and 30-56% higher inorganic P in the roots, likely due to phytase-mediated hydrolysis of phytate. Decrease of phytate levels up-regulated phosphate transporter genes (NbPht1;1, NbPht1;2 and NbPht1;6), leading to greater P and As uptake. However, As translocation to the shoots was low, probably due to competition from increased inorganic P via phytate hydrolysis. As such, PvPHY1 facilitated P uptake from soils and phytate hydrolysis in plants, thereby promoting tobacco growth. Overall, PvPHY1 from P. vittata helps better understand the novel phytase to increase soil P utilization efficiency, thereby reducing P fertilizer requirements for crop production.

Extinction at the end-Cretaceous and the origin of modern Neotropical rainforests.

The end-Cretaceous event was catastrophic for terrestrial communities worldwide, yet its long-lasting effect on tropical forests remains largely unknown. We quantified plant extinction and ecological change in tropical forests resulting from the end-Cretaceous event using fossil pollen (>50,000 occurrences) and leaves (>6000 specimens) from localities in Colombia. Late Cretaceous (Maastrichtian) rainforests were characterized by an open canopy and diverse plant-insect interactions. Plant diversity declined by 45% at the Cretaceous-Paleogene boundary and did not recover for ~6 million years. Paleocene forests resembled modern Neotropical rainforests, with a closed canopy and multistratal structure dominated by angiosperms. The end-Cretaceous event triggered a long interval of low plant diversity in the Neotropics and the evolutionary assembly of today's most diverse terrestrial ecosystem.

Nitrogen deposition accelerates soil carbon sequestration in tropical forests.

Terrestrial ecosystem carbon (C) sequestration plays an important role in ameliorating global climate change. While tropical forests exert a disproportionately large influence on global C cycling, there remains an open question on changes in below-ground soil C stocks with global increases in nitrogen (N) deposition, because N supply often does not constrain the growth of tropical forests. We quantified soil C sequestration through more than a decade of continuous N addition experiment in an N-rich primary tropical forest. Results showed that long-term N additions increased soil C stocks by 7 to 21%, mainly arising from decreased C output fluxes and physical protection mechanisms without changes in the chemical composition of organic matter. A meta-analysis further verified that soil C sequestration induced by excess N inputs is a general phenomenon in tropical forests. Notably, soil N sequestration can keep pace with soil C, based on consistent C/N ratios under N additions. These findings provide empirical evidence that below-ground C sequestration can be stimulated in mature tropical forests under excess N deposition, which has important implications for predicting future terrestrial sinks for both elevated anthropogenic CO2 and N deposition. We further developed a conceptual model hypothesis depicting how soil C sequestration happens under chronic N deposition in N-limited and N-rich ecosystems, suggesting a direction to incorporate N deposition and N cycling into terrestrial C cycle models to improve the predictability on C sink strength as enhanced N deposition spreads from temperate into tropical systems.

Seasonal upwelling reduces herbivore control of tropical rocky intertidal algal communities.

Communities are shaped by a variety of ecological and environmental processes, each acting at different spatial scales. Seminal research on rocky shores highlighted the effects of consumers as local determinants of primary productivity and community assembly. However, it is now clear that the species interactions shaping communities at local scales are themselves regulated by large-scale oceanographic processes that generate regional variation in resource availability. Upwelling events deliver nutrient-rich water to coastal ecosystems, influencing primary productivity and algae-herbivore interactions. Despite the potential for upwelling to alter top-down control by herbivores, we know relatively little about the coupling between oceanographic processes and herbivory on tropical rocky shores, where herbivore effects on producers are considered to be strong and nutrient levels are considered to be limiting. By replicating seasonal molluscan herbivore exclusion experiments across three regions exposed to varying intensity of seasonal upwelling, separated by hundreds of kilometers along Panama's Pacific coast, we examine large-scale environmental determinants of consumer effects and community structure on tropical rocky shores. At sites experiencing seasonal upwelling, grazers strongly limited macroalgal cover when upwelling was absent, leading to dominance by crustose algae. As nutrients increased and surface water cooled during upwelling events, increases in primary productivity temporarily weakened herbivory, allowing foliose, turf and filamentous algae to replace crusts. Meanwhile, grazer effects were persistently strong at sites without seasonal upwelling. Our results confirm that herbivores are key determinants of tropical algal cover, and that the mollusk grazing guild can control initial stages of macroalgal succession. However, our focus on regional oceanographic conditions revealed that bottom-up processes regulate top-down control on tropical shorelines. This study expands on the extensive body of work highlighting the influence of upwelling on local ecological processes by demonstrating that nutrient subsidies delivered by upwelling events can weaken herbivory in tropical rocky shores.

A shift from phenol to silica-based leaf defences during long-term soil and ecosystem development.

The resource availability hypothesis predicts that plants adapted to infertile soils have high levels of anti-herbivore leaf defences. This hypothesis has been mostly explored for secondary metabolites such as phenolics, whereas it remains underexplored for silica-based defences. We determined leaf concentrations of total phenols and silicon (Si) in plants growing along the 2-million-year Jurien Bay chronosequence, exhibiting an extreme gradient of soil fertility. We found that nitrogen (N) limitation on young soils led to a greater expression of phenol-based defences, whereas old, phosphorus (P)-impoverished soils favoured silica-based defences. Both defence types were negatively correlated at the community and individual species level. Our results suggest a trade-off among these two leaf defence strategies based on the strength and type of nutrient limitation, thereby opening up new perspectives for the resource availability hypothesis and plant defence research. This study also highlights the importance of silica-based defences under low P supply.

Soil microbial communities influencing organic phosphorus mineralization in a coastal dune chronosequence in New Zealand.

The Haast chronosequence in New Zealand is an ∼6500-year dune formation series, characterized by rapid podzol development, phosphorus (P) depletion and a decline in aboveground biomass. We examined bacterial and fungal community composition within mineral soil fractions using amplicon-based high-throughput sequencing (Illumina MiSeq). We targeted bacterial non-specific acid (class A, phoN/phoC) and alkaline (phoD) phosphomonoesterase genes and quantified specific genes and transcripts using real-time PCR. Soil bacterial diversity was greatest after 4000 years of ecosystem development and associated with an increased richness of phylotypes and a significant decline in previously dominant taxa (Firmicutes and Proteobacteria). Soil fungal communities transitioned from predominantly Basidiomycota to Ascomycota along the chronosequence and were most diverse in 290- to 392-year-old soils, coinciding with maximum tree basal area and organic P accumulation. The Bacteria:Fungi ratio decreased amid a competitive and interconnected soil community as determined by network analysis. Overall, soil microbial communities were associated with soil changes and declining P throughout pedogenesis and ecosystem succession. We identified an increased dependence on organic P mineralization, as found by the profiled acid phosphatase genes, soil acid phosphatase activity and function inference from predicted metagenomes (PICRUSt2).

Demographic consequences of foraging ecology explain genetic diversification in Neotropical bird species.

Despite evidence that species' traits affect rates of bird diversification, biogeographic studies tend to prioritise earth history in Neotropical bird speciation. Here we compare mitochondrial genetic differentiation among 56 co-distributed Neotropical bird species with varying ecologies. The trait 'diet' best predicted divergence, with plant-dependent species (mostly frugivores and nectivores) showing lower levels of genetic divergence than insectivores or mixed-diet species. We propose that the greater vagility and demographic instability of birds whose diets rely on fruit, seeds, or nectar  known to vary in abundance seasonally and between years  relative to birds that eat primarily insects, drives episodic re-unification of otherwise isolated populations, resetting the divergence 'clock'. Testing this prediction using coalescent simulations, we find that plant-dependent species show stronger signals of recent demographic expansion compared to insectivores or mixed-diet species, consistent with this hypothesis. Our study provides evidence that localised ecological phenomena scale up to generate larger macroevolutionary patterns.

Temperate Forests Dominated by Arbuscular or Ectomycorrhizal Fungi Are Characterized by Strong Shifts from Saprotrophic to Mycorrhizal Fungi with Increasing Soil Depth.

In temperate and boreal forests, competition for soil resources between free-living saprotrophs and ectomycorrhizal (EcM) fungi has been suggested to restrict saprotrophic fungal dominance to the most superficial organic soil horizons in forests dominated by EcM trees. By contrast, lower niche overlap with arbuscular mycorrhizal (AM) fungi could allow fungal saprotrophs to maintain this dominance into deeper soil horizons in AM-dominated forests. Here we used a natural gradient of adjacent forest patches that were dominated by either AM or EcM trees, or a mixture of both to determine how fungal communities characterized with high-throughput amplicon sequencing change across organic and mineral soil horizons. We found a general shift from saprotrophic to mycorrhizal fungal dominance with increasing soil depth in all forest mycorrhizal types, especially in organic horizons. Vertical changes in soil chemistry, including pH, organic matter, exchangeable cations, and extractable phosphorus, coincided with shifts in fungal community composition. Although fungal communities and soil chemistry differed among adjacent forest mycorrhizal types, variations were stronger within a given soil profile, pointing to the importance of considering horizons when characterizing soil fungal communities. Our results also suggest that in temperate forests, vertical shifts from saprotrophic to mycorrhizal fungi within organic and mineral horizons occur similarly in both ectomycorrhizal and arbuscular mycorrhizal forests.

Author Correction: Soil carbon loss by experimental warming in a tropical forest.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The Role of Phosphorus Limitation in Shaping Soil Bacterial Communities and Their Metabolic Capabilities.

Phosphorus (P) is an essential nutrient that is often in limited supply, with P availability constraining biomass production in many terrestrial ecosystems. Despite decades of work on plant responses to P deficiency and the importance of soil microbes to terrestrial ecosystem processes, how soil microbes respond to, and cope with, P deficiencies remains poorly understood. We studied 583 soils from two independent sample sets that each span broad natural gradients in extractable soil P and collectively represent diverse biomes, including tropical forests, temperate grasslands, and arid shrublands. We paired marker gene and shotgun metagenomic analyses to determine how soil bacterial and archaeal communities respond to differences in soil P availability and to detect corresponding shifts in functional attributes. We identified microbial taxa that are consistently responsive to extractable soil P, with those taxa found in low P soils being more likely to have traits typical of oligotrophic life history strategies. Using environmental niche modeling of genes and gene pathways, we found an enriched abundance of key genes in low P soils linked to the carbon-phosphorus (C-P) lyase and phosphonotase degradation pathways, along with key components of the high-affinity phosphate-specific transporter (Pst) and phosphate regulon (Pho) systems. Taken together, these analyses suggest that catabolism of phosphonates is an important strategy used by bacteria to scavenge phosphate in P-limited soils. Surprisingly, these same pathways are important for bacterial growth in P-limited marine waters, highlighting the shared metabolic strategies used by both terrestrial and marine microbes to cope with P limitation.

Soil carbon loss by experimental warming in a tropical forest.

Tropical soils contain one-third of the carbon stored in soils globally1, so destabilization of soil organic matter caused by the warming predicted for tropical regions this century2 could accelerate climate change by releasing additional carbon dioxide (CO2) to the atmosphere3-6. Theory predicts that warming should cause only modest carbon loss from tropical soils relative to those at higher latitudes5,7, but there have been no warming experiments in tropical forests to test this8. Here we show that in situ experimental warming of a lowland tropical forest soil on Barro Colorado Island, Panama, caused an unexpectedly large increase in soil CO2 emissions. Two years of warming of the whole soil profile by four degrees Celsius increased CO2 emissions by 55 per cent compared to soils at ambient temperature. The additional CO2 originated from heterotrophic rather than autotrophic sources, and equated to a loss of 8.2 ± 4.2 (one standard error) tonnes of carbon per hectare per year from the breakdown of soil organic matter. During this time, we detected no acclimation of respiration rates, no thermal compensation or change in the temperature sensitivity of enzyme activities, and no change in microbial carbon-use efficiency. These results demonstrate that soil carbon in tropical forests is highly sensitive to warming, creating a potentially substantial positive feedback to climate change.

Competing effects of soil fertility and toxicity on tropical greening.

Tropical forests are expected to green up with increasing atmospheric CO2 concentrations, but primary productivity may be limited by soil nutrient availability. However, rarely have canopy-scale measurements been assessed against soil measurements in the tropics. Here, we sought to assess remotely sensed canopy greenness against steep soil nutrient gradients across 50 1-ha mature forest plots in Panama. Contrary to expectations, increases in in situ extractable soil phosphorus (P) and base cations (K, Mg) corresponded to declines in remotely sensed mean annual canopy greenness (r2 = 0.77-0.85; p < 0.1), controlling for precipitation. The reason for this inverse relationship appears to be that litterfall also increased with increasing soil P and cation availability (r2 = 0.88-0.98; p < 0.1), resulting in a decline in greenness with increasing annual litterfall (r2 = 0.94; p < 0.1). As such, greater soil nutrient availability corresponded to greater leaf turnover, resulting in decreased greenness. However, these decreases in greenness with increasing soil P and cations were countered by increases in greenness with increasing soil nitrogen (N) (r2 = 0.14; p < 0.1), which had no significant relationship with litterfall, likely reflecting a direct effect of soil N on leaf chlorophyll content, but not on litterfall rates. In addition, greenness increased with extractable soil aluminum (Al) (r2 = 0.97; p < 0.1), but Al had no significant relationship with litterfall, suggesting a physiological adaptation of plants to high levels of toxic metals. Thus, spatial gradients in canopy greenness are not necessarily positive indicators of soil nutrient scarcity. Using a novel remote sensing index of canopy greenness limitation, we assessed how observed greenness compares with potential greenness. We found a strong relationship with soil N only (r2 = 0.65; p < 0.1), suggesting that tropical canopy greenness in Panama is predominantly limited by soil N, even if plant productivity (e.g., litterfall) responds to rock-derived nutrients. Moreover, greenness limitation was also significantly correlated with fine root biomass and soil carbon stocks (r2 = 0.62-0.71; p < 0.1), suggesting a feedback from soil N to canopy greenness to soil carbon storage. Overall, these data point to the potential utility of a remote sensing product for assessing belowground properties in tropical ecosystems.

Greater root phosphatase activity of tropical trees at low phosphorus despite strong variation among species.

Soil phosphorus (P) availability in lowland tropical rainforests influences the distribution and growth of tropical tree species. Determining the P-acquisition strategies of tropical tree species could therefore yield insight into patterns of tree ß-diversity across edaphic gradients. In particular, the synthesis of root phosphatases is likely to be of significance given that organic P represents a large pool of potentially available P in tropical forest soils. It has also been suggested that a high root phosphatase activity in putative nitrogen (N) -fixing legumes might explain their high abundance in lowland neotropical forests under low P supply. Here, we measured phosphomonoesterase (PME) activity on the first three root orders of co-occurring tropical tree species differing in their N-fixation capacity, growing on soils of contrasting P availability in Panama. Our results show that root PME activity was higher on average in P-poor than in P-rich soils, but that local variation in PME activity among co-occurring species within a site was larger than that explained by differences in soil P across sites. Legumes expressed higher PME activity than nonlegumes, but nodulated legumes (i.e., actively fixing nitrogen) did not differ from legumes without nodules, indicating that PME activity is unrelated to N fixation. Finally, PME activity declined with increasing root order, but the magnitude of the decline varied markedly among species, highlighting the importance of classifying fine roots into functional groups prior to measuring root traits. Our results support the hypothesis that low-P promotes a high root PME activity, although the high local variation in this trait among co-occurring species points toward a high functional diversity in P-acquisition strategies within an individual community.

Why are tropical conifers disadvantaged in fertile soils? Comparison of Podocarpus guatemalensis with an angiosperm pioneer, Ficus insipida.

Conifers are, for the most part, competitively excluded from tropical rainforests by angiosperms. Where they do occur, conifers often occupy sites that are relatively infertile. To gain insight into the physiological mechanisms by which angiosperms outcompete conifers in more productive sites, we grew seedlings of a tropical conifer (Podocarpus guatemalensis Standley) and an angiosperm pioneer (Ficus insipida Willd.) with and without added nutrients, supplied in the form of a slow-release fertilizer. At the conclusion of the experiment, the dry mass of P. guatemalensis seedlings in fertilized soil was approximately twofold larger than that of seedlings in unfertilized soil; on the other hand, the dry mass of F. insipida seedlings in fertilized soil was ~20-fold larger than seedlings in unfertilized soil. The higher relative growth rate of F. insipida was associated with a larger leaf area ratio and a higher photosynthetic rate per unit leaf area. Higher overall photosynthetic rates in F. insipida were associated with an approximately fivefold larger stomatal conductance than in P. guatemalensis. We surmise that a higher whole-plant hydraulic conductance in the vessel bearing angiosperm F. insipida enabled higher leaf area ratio and higher stomatal conductance per unit leaf area than in the tracheid bearing P. guatemalensis, which enabled F. insipida to capitalize on increased photosynthetic capacity driven by higher nitrogen availability in fertilized soil.