Adult trees cause density‐dependent mortality in conspecific seedlings by regulating the frequency of pathogenic soil fungi

Negative density‐dependent seedling mortality has been widely detected in tropical, subtropical and temperate forests, with soil pathogens as a major driver. Here we investigated how host density affects the composition of soil pathogen communities and consequently influences the strength of plant‐soil feedbacks. In field censuses of six 1‐ha permanent plots, we found that survival was much lower for newly germinated seedlings that were surrounded by more conspecific adults. The relative abundance of pathogenic fungi in soil increased with increasing conspecific tree density for five of nine tree species; more soil pathogens accumulated around roots where adult tree density was higher, and this greater pathogen frequency was associated with lower seedling survival. Our findings show how tree density influences populations of soil pathogens, which creates plant‐soil feedbacks that contribute to community‐level and population‐level compensatory trends in seedling survival.     

The genetic dimension of pest pressure in the tropical rainforest

Wet tropical forests are among the most diverse ecosystems on Earth and can host several hundreds of tree species per hectare. To maintain such diversity, the community must contain large numbers of relatively rare species rather than be dominated by a few very common trees, as is often the case in temperate forests. Explaining the mechanisms preventing dominance by common species has been a major task of tropical forest ecology. One of the most promising mechanisms is negative density dependence (NDD) of tree abundance driven by pests, including fungal diseases (‘pest pressure’). NDD entails that the chance of survival of a sapling increases with the distance from a mature tree of the same species, thus preventing species from becoming locally dominant. Curiously, the strength of NDD is negatively correlated with abundance, meaning that tree species that are more common generally show weaker NDD (Comita et al. 2010 ). Interactions between plants and soil pathogens have been shown to play an important role in NDD (Klironomos 2002 ), and rare species are apparently more strongly affected (Mangan et al. 2010 ). However, the genetic mechanisms underlying this phenomenon have remained obscure. In this issue of Molecular Ecology, Marden et al. ( 2017 ) suggest that reduced diversity of the genes involved in pathogen recognition (Resistance genes or R genes) could explain why NDD is stronger in locally rare species.     

Limited contributions of plant pathogens to density‐dependent seedling mortality of mast fruiting Bornean trees

Fungal pathogens are implicated in driving tropical plant diversity by facilitating strong, negative density‐dependent mortality of conspecific seedlings (C‐NDD). Assessment of the role of fungal pathogens in mediating coexistence derives from relatively few tree species and predominantly the Neotropics, limiting our understanding of their role in maintaining hyper‐diversity in many tropical forests. A key question is whether fungal pathogen‐mediated C‐NDD seedling mortality is ubiquitous across diverse plant communities. Using a manipulative shadehouse experiment, we tested the role of fungal pathogens in mediating C‐NDD seedling mortality of eight mast fruiting Bornean trees, typical of the species‐rich forests of South East Asia. We demonstrate species‐specific responses of seedlings to fungicide and density treatments, generating weak negative density‐dependent mortality. Overall seedling mortality was low and likely insufficient to promote overall community diversity. Although conducted in the same way as previous studies, we find little evidence that fungal pathogens play a substantial role in determining patterns of seedling mortality in a SE Asian mast fruiting forest, questioning our understanding of how Janzen‐Connell mechanisms structure the plant communities of this globally important forest type.     

The Relative Importance of Fungal Infection,Conspecific Density and Environmental Heterogeneity for Seedling Survival in a Dominant Tropical Tree

A gap remains in our understanding of how host‐specific fungal pathogens impact negative density dependence (NDD). Here, we investigated survival of Cinnamomum subavenium Miq. seedlings, the dominant canopy species in a seasonal tropical evergreen forest, Thailand. It is infected by a host‐specific fungus that is easily identifiable in the field. We quantified the effects of conspecific seedling and adult density on fungal infection and seedling survival over a wide range of environmental heterogeneity in elevation, understory vegetation and presence of forest gaps. Generalized linear mixed models (GLMMs) for seedling survival revealed that fungal infection significantly reduced survival and had the strongest effect on seedling survival as compared with conspecific density and environmental heterogeneity. Adult conspecific density was not, however, significantly correlated with the probability of infection, and conspecific seedling density was positively associated with increased infection only at high elevations. In contrast to infection, we found a significant positive correlation between conspecific seedling density and the probability of seedling survival. Consequently, our results demonstrate that fungal infection can have major impacts on seedling survival, but not in a manner consistent with local NDD effects on seedlings, as assumed in the Janzen–Connell hypothesis. Our study provides an example of how quantifying the interaction between environmental heterogeneity and a host‐specific plant‐pathogen can yield unexpected insights into the dynamics of seedling populations. The combined effects of host‐specific pathogens and environmental heterogeneity on survival of dominant seedling species may ultimately provide a chance for rarer species to recruit.     

Leaf diseases drive the Janzen–Connell mechanism regardless of light conditions: a 3-year field study

In forests, negative density/distance-dependent seedling mortality (NDD) caused by natural enemies plays a key role in maintaining species diversity [Janzen–Connell (J–C) model]. However, the relative importance of natural enemies in mediating NDD under heterogeneous light conditions has remained unclear. We examined the relative importance of pathogens (i.e., soil pathogens, leaf diseases) on seedling performance in forest understories (FUs) and gaps (gaps) during a 3-year period (results of first year of our study have been previously reported). For the hardwood, Prunus grayana, we investigated seedling mortality, morbidity agents, growth, and root infection by arbuscular mycorrhizal fungi (AMF) beneath conspecific and heterospecific adults in FUs and gaps. Seedling mortality was higher beneath conspecific than heterospecific adults throughout 3 years at both sites, mainly due to continuous leaf disease (i.e., angular leaf spot), whereas damping-off diseases caused mortality only in the first year. Beneath each adult, seedling mortality was higher in FUs than in gaps until second year, but it did not differ between two habitat types in the third year, because leaf diseases caused severe damage even in gaps. Seedling mass was significantly lower beneath conspecific adults. AMF infection of seedlings was also lower beneath conspecific adults, while it was higher in gaps than in FUs beneath both adults. This study demonstrates that the J–C model in a hardwood tree, P. grayana is mainly driven by high NDD seedling mortality caused by airborne leaf diseases, which continuously attack seedlings in a NDD manner regardless of environmental light conditions.     

Changes in biotic and abiotic drivers of seedling species composition during forest recovery following shifting cultivation on Hainan Island,China

Seedlings play an important role in the processes of plant community succession. We compared seedling (dbh < 1 cm) species composition and diversity over a chronosequence (18‐, 30‐, 60‐year‐old second growth and old growth forest) after shifting cultivation in a tropical lowland rain forest area on Hainan Island, China. Seedling diversity reached a maximum in the 60‐year‐old second growth forest, which is consistent with the intermediate disturbance hypothesis. With the progression of secondary succession, canopy openness (CO), soil organic matter, soil phosphorus content, and tree abundance showed a general decreasing trend; soil water content and tree basal area showed a general trend of increase, while soil pH and other nutrients reached maximum values and tree richness reached a minimum value at intermediate stages of succession. Seedling composition and diversity were significantly affected by soil water, pH, soil nutrient content, and biotic factors in the 18‐year‐old second growth forests; by soil pH, soil nutrient content, and biotic factors in the 30‐year‐old second growth forests; by CO, soil nutrient content and tree abundance in the 60‐year‐old second growth forests; and by CO, soil pH, and soil nutrient content in the old growth forests. At earlier stages of succession, the effect of the proportion of old growth forest in the surrounding landscape on seedling diversity was greater than that of land‐use history, but the importance of these drivers was reversed at later stages of succession.     

Conspecific density dependence and community structure: Insights from 11 years of monitoring in an old‐growth temperate forest in Northeast China

Forest community structure may be influenced by seedling density dependence, however, the effect is loosely coupled with population dynamics and diversity in the short term. In the long term the strength of conspecific density dependence may fluctuate over time because of seedling abundance, yet few long‐term studies exist. Based on 11 years of seedling census data and tree census data from a 25‐ha temperate forest plot in Northeast China, we used generalized linear mixed models to test the relative effects of local neighborhood density and abiotic factors on seedling density and seedling survival. Spatial point pattern analysis was used to determine if spatial patterns of saplings and juveniles, in relation to conspecific adults, were in accordance with patterns uncovered by conspecific negative density dependence at the seedling stage. Our long‐term results showed that seedling density was mainly positively affected by conspecific density, suggesting dispersal limitation of seedling development. The probability of seedling survival significantly decreased over 1 year with increasing conspecific density, indicating conspecific negative density dependence in seedling establishment. Although there was variation in conspecific negative density dependence at the seedling stage among species and across years, a dispersed pattern of conspecific saplings relative to conspecific adults at the local scale (<10 m) was observed in four of the 11 species examined. Overall, sapling spatial patterns were consistent with the impacts of conspecific density on seedling dynamics, which suggests that conspecific negative density dependence is persistent over the long term. From the long‐term perspective, conspecific density dependence is an important driver of species coexistence in temperate forests.     

Community compensatory trend prevails from tropical to temperate forest

Community compensatory trend (CCT) is thought to facilitate persistence of rare species and thus stabilize species composition in tropical forests. However, whether CCT acts over broad geographical ranges is still in question. In this study, we tested for the presence of negative density dependence (NDD) and CCT in three forests along a tropical-temperate gradient. Inventory data were collected from forest communities located in three different latitudinal zones in China. Two widely used methods were used to test for NDD at the community level. The first method considered relationships between the relative abundance ratio and adult abundance. The second method emphasized the effect of adult abundance on abundance of established younger trees. Evidence for NDD acting on different growth forms was tested by using the first method, and the presence of CCT was tested by checking whether adult abundance of rare species affected that of established younger trees less than did abundance of common species. Both analyses indicated that NDD existed in seedling, sapling and pole stages in all three plant communities and that this effect increased with latitude. However, the extent of NDD varied among understory, midstory and canopy trees in the three communities along the gradient. Additionally, despite evidence of NDD for almost all common species, only a portion of rare species showed NDD, supporting the action of CCT in all three communities. So, we conclude that NDD and CCT prevail in the three recruitment stages of the tree communities studied; rare species achieve relative advantage through CCT and thus persist in these communities; CCT clearly facilitates newly established species and maintains tree diversity within communities across our latitudinal gradient.     

Community composition and diversity of Neotropical root‐associated fungi in common and rare trees

Interactions between plants and root‐associated fungi can affect the assembly, diversity, and relative abundances of tropical plant species. Host–symbiont compatibility and some degree of host specificity are prerequisites for these processes to occur, and these prerequisites may vary with host abundance. However, direct assessments of whether specificity of root‐associated fungi varies with host abundance are lacking. Here, in a diverse tropical forest in Los Tuxtlas, Mexico, we couple DNA metabarcoding with a sampling design that controls for host phylogeny, host age, and habitat variation, to characterize fungal communities associated with the roots of three confamilial pairs of host species that exhibit contrasting (high and low) relative abundances. We uncovered a functionally and phylogenetically diverse fungal community composed of 1,038 OTUs (operational taxonomic units with 97% genetic similarity), only 14 of which exhibited host specificity. Host species was a significant predictor of fungal community composition only for the subset of OTUs composed of putatively pathogenic fungi. We found no significant difference in the number of specialists associating with common versus rare trees, but we found that host abundance was negatively correlated with the diversity of root fungal communities. This latter result was significant for symbiotrophs (mostly arbuscular mycorrhizal fungi) and, to a lesser extent, for pathotrophs (mostly plant pathogens). Thus, root fungal communities differ between common and rare trees, which may impact the strength of conspecific negative density dependence. Further studies from other tropical sites and host lineages are warranted, given the role of root‐associated fungi in biodiversity maintenance.     

Environmental heterogeneity and biotic interactions mediate climate impacts on tropical forest regeneration

Predicting the fate of tropical forests under a changing climate requires understanding species responses to climatic variability and extremes. Seedlings may be particularly vulnerable to climatic stress given low stored resources and undeveloped roots; they also portend the potential effects of climate change on future forest composition. Here we use data for ca. 50,000 tropical seedlings representing 25 woody species to assess (i) the effects of interannual variation in rainfall and solar radiation between 2007 and 2016 on seedling survival over 9 years in a subtropical forest; and (ii) how spatial heterogeneity in three environmental factors—soil moisture, understory light, and conspecific neighborhood density—modulate these responses. Community‐wide seedling survival was not sensitive to interannual rainfall variability but interspecific variation in these responses was large, overwhelming the average community response. In contrast, community‐wide responses to solar radiation were predominantly positive. Spatial heterogeneity in soil moisture and conspecific density were the predominant and most consistent drivers of seedling survival, with the majority of species exhibiting greater survival at low conspecific densities and positive or nonlinear responses to soil moisture. This environmental heterogeneity modulated impacts of rainfall and solar radiation. Negative conspecific effects were amplified during rainy years and at dry sites, whereas the positive effects of radiation on survival were more pronounced for seedlings existing at high understory light levels. These results demonstrate that environmental heterogeneity is not only the main driver of seedling survival in this forest but also plays a central role in buffering or exacerbating impacts of climate fluctuations on forest regeneration. Since seedlings represent a key bottleneck in the demographic cycle of trees, efforts to predict the long‐term effects of a changing climate on tropical forests must take into account this environmental heterogeneity and how its effects on regeneration dynamics play out in long‐term stand dynamics.     

Altered climate leads to positive density‐dependent feedbacks in a tropical wet forest

Climate change is predicted to result in warmer and drier Neotropical forests relative to current conditions. Negative density‐dependent feedbacks, mediated by natural enemies, are key to maintaining the high diversity of tree species found in the tropics, yet we have little understanding of how projected changes in climate are likely to affect these critical controls. Over 3 years, we evaluated the effects of a natural drought and in situ experimental warming on density‐dependent feedbacks on seedling demography in a wet tropical forest in Puerto Rico. In the +4°C warming treatment, we found that seedling survival increased with increasing density of the same species (conspecific). These positive density‐dependent feedbacks were not associated with a decrease in aboveground natural enemy pressure. If positive density‐dependent feedbacks are not transient, the diversity of tropical wet forests, which may rely on negative density dependence to drive diversity, could decline in a future warmer, drier world.     

An ectomycorrhizal nitrogen economy facilitates monodominance in a neotropical forest

Tropical forests are renowned for their high diversity, yet in many sites a single tree species accounts for the majority of the individuals in a stand. An explanation for these monodominant forests remains elusive, but may be linked to mycorrhizal symbioses. We tested three hypotheses by which ectomycorrhizas might facilitate the dominance of the tree, Oreomunnea mexicana, in montane tropical forest in Panama. We tested whether access to ectomycorrhizal networks improved growth and survival of seedlings, evaluated whether ectomycorrhizal fungi promote seedling growth via positive plant–soil feedback, and measured whether Oreomunnea reduced inorganic nitrogen availability. We found no evidence that Oreomunnea benefits from ectomycorrhizal networks or plant–soil feedback. However, we found three‐fold higher soil nitrate and ammonium concentrations outside than inside Oreomunnea‐dominated forest and a correlation between soil nitrate and Oreomunnea abundance in plots. Ectomycorrhizal effects on nitrogen cycling might therefore provide an explanation for the monodominance of ectomycorrhizal tree species worldwide.     

Lower Within-Community Variance of Negative Density Dependence Increases Forest Diversity

Local abundance of adult trees impedes growth of conspecific seedlings through host-specific enemies, a mechanism first proposed by Janzen and Connell to explain plant diversity in forests. While several studies suggest the importance of this mechanism, there is still little information of how the variance of negative density dependence (NDD) affects diversity of forest communities. With computer simulations, we analyzed the impact of strength and variance of NDD within tree communities on species diversity. We show that stronger NDD leads to higher species diversity. Furthermore, lower range of strengths of NDD within a community increases species richness and decreases variance of species abundances. Our results show that, beyond the average strength of NDD, the variance of NDD is also crucially important to explain species diversity. This can explain the dissimilarity of biodiversity between tropical and temperate forest: highly diverse forests could have lower NDD variance. This report suggests that natural enemies and the variety of the magnitude of their effects can contribute to the maintenance of biodiversity.     

Negative density dependence of seed dispersal and seedling recruitment in a Neotropical palm

Negative density dependence (NDD) of recruitment is pervasive in tropical tree species. We tested the hypotheses that seed dispersal is NDD, due to intraspecific competition for dispersers, and that this contributes to NDD of recruitment. We compared dispersal in the palm Attalea butyracea across a wide range of population density on Barro Colorado Island in Panama and assessed its consequences for seed distributions. We found that frugivore visitation, seed removal and dispersal distance all declined with population density of A. butyracea, demonstrating NDD of seed dispersal due to competition for dispersers. Furthermore, as population density increased, the distances of seeds from the nearest adult decreased, conspecific seed crowding increased and seedling recruitment success decreased, all patterns expected under poorer dispersal. Unexpectedly, however, our analyses showed that NDD of dispersal did not contribute substantially to these changes in the quality of the seed distribution; patterns with population density were dominated by effects due solely to increasing adult and seed density.     

Ultraviolet‐C priming of strawberry leaves against subsequent Mycosphaerella fragariae infection involves the action of reactive oxygen species,plant hormones,and terpenes

Ultraviolet‐C (UV‐C) radiation has been reported to induce defence responses to pathogens in growing crops and described as a new environmentally friendly method for disease control. However, whether the effect of the induced defence mechanisms will persist after the stress imposed by UV‐C is alleviated and how these mechanisms interact with pathogen elicitors upon infection have not yet been investigated. Thus, we inoculated strawberry plants with Mycosphaerella fragariae, the causal agent of leaf spot disease, after 5 weeks of repeated UV‐C irradiation treatment (cumulative dose of 10.2 kJ m^?2) and investigated the alteration of gene expression and biochemical phenotypes. The results revealed that UV‐C treatment had a significant impact on gene expression in strawberry leaves and led to the overexpression of a set of genes involved in plant–pathogen interaction. UV‐C‐treated leaves displayed a stronger response to infection after inoculation, with reduced symptoms and increases in accumulation of total phenolics and volatile terpenes, higher expression of pathogenesis‐related proteins and the activity of several defence enzymes. This study presumptively describe, for the first time, the involvement of terpenes, reactive oxygen species, and abscisic acid, salicylic acid, jasmonic acid, and their transduction factors, in the network underpinning UV‐C priming of growing crops for improved protection against pathogens.     

Phylogenetic conservatism in plant‐soil feedback and its implications for plant abundance

We examined whether plant‐soil feedback and plant‐field abundance were phylogenetically conserved. For 57 co‐occurring native and exotic plant species from an old field in Canada, we collected a data set on the effects of three soil biota treatments on plant growth: net whole‐soil feedback (combined effects of mutualists and antagonists), feedback with arbuscular mycorrhizal fungi (AMF) collected from soils of conspecific plants, and feedback with Glomus etunicatum, a dominant mycorrhizal fungus. We found phylogenetic signal in both net whole‐soil feedback and feedback with AMF of conspecifics; conservatism was especially strong among native plants but absent among exotics. The abundance of plants in the field was also conserved, a pattern underlain by shared plant responses to soil biota. We conclude that soil biota influence the abundance of close plant relatives in nature.     

Density‐dependent Survival in Seedlings Differs among Woody Life‐forms in Tropical Wet Forests of a Caribbean Island

Negative density dependence contributes to seedling dynamics in forested ecosystems, but the relative importance of this factor for different woody plant life‐forms is not well‐understood. We used 1 yr of seedling survivorship data for woody seedlings in 17 different plots of lower to mid‐montane rain forests on the island of Dominica to examine how seedling height, abiotic factors, and biotic factors such as negative density dependence are related to seedling survival of five different life‐forms (canopy, midstory, and understory trees; shrubs; and lianas). Across 64 species, taller seedlings in seedling plots with higher canopy openness, greater seedling density, lower relative abundance of conspecific seedlings, and lower relative abundance of conspecific adults generally had a greater probability of surviving. Height was the strongest predictor of seedling survival for all life‐forms except lianas. Greater seedling density was positively related to survival for canopy and midstory trees but negatively related to survival for the other life‐forms. For trees, the relative abundance of conspecific seedling and adult neighbors had weak and strong negative effects on survival respectively. Neither shrub nor liana seedling survival was affected by the relative abundance of conspecific neighbors. Thus, negative density dependence is confirmed as an important structuring mechanism for tree seedling communities but does not seem to be important for lianas and shrubs in Dominican rain forests. These results represent the first direct assessment of controls on seedling survival of all woody life‐forms – an important step in understanding the dynamics and structure of the entire woody plant community.     

The ecology,distribution, conservation and management of large old trees

Large old trees are some of the most iconic biota on earth and are integral parts of many terrestrial ecosystems including those in tropical, temperate and boreal forests, deserts, savannas, agro‐ecological areas, and urban environments. In this review, we provide new insights into the ecology, function, evolution and management of large old trees through broad cross‐disciplinary perspectives from literatures in plant physiology, growth and development, evolution, habitat value for fauna and flora, and conservation management. Our review reveals that the diameter, height and longevity of large old trees varies greatly on an inter‐specific basis, thereby creating serious challenges in defining large old trees and demanding an ecosystem‐ and species‐specific definition that will only rarely be readily transferable to other species or ecosystems. Such variation is also manifested by marked inter‐specific differences in the key attributes of large old trees (beyond diameter and height) such as the extent of buttressing, canopy architecture, the extent of bark micro‐environments and the prevalence of cavities. We found that large old trees play an extraordinary range of critical ecological roles including in hydrological regimes, nutrient cycles and numerous ecosystem processes. Large old trees strongly influence the spatial and temporal distribution and abundance of individuals of the same species and populations of numerous other plant and animal species. We suggest many key characteristics of large old trees such as extreme height, prolonged lifespans, and the presence of cavities – which confer competitive and evolutionary advantages in undisturbed environments – can render such trees highly susceptible to a range of human influences. Large old trees are vulnerable to threats ranging from droughts, fire, pests and pathogens, to logging, land clearing, landscape fragmentation and climate change. Tackling such diverse threats is challenging because they often interact and manifest in different ways in different ecosystems, demanding targeted species‐ or ecosystem‐specific responses. We argue that novel management actions will often be required to protect existing large old trees and ensure the recruitment of new cohorts of such trees. For example, fine‐scale tree‐level conservation such as buffering individual stems will be required in many environments such as in agricultural areas and urban environments. Landscape‐level approaches like protecting places where large old trees are most likely to occur will be needed. However, this brings challenges associated with likely changes in tree distributions associated with climate change, because long‐lived trees may presently exist in places unsuitable for the development of new cohorts of the same species. Appropriate future environmental domains for a species could exist in new locations where it has never previously occurred. The future distribution and persistence of large old trees may require controversial responses including assisted migration via seed or seedling establishment in new locales. However, the effectiveness of such approaches may be limited where key ecological features of large old trees (such as cavity presence) depend on other species such as termites, fungi and bacteria. Unless other species with similar ecological roles are present to fulfil these functions, these taxa might need to be moved concurrently with the target tree species.     

Distance‐dependent effects of soil‐derived biota on seedling survival of the tropical tree legume Ormosia semicastrata

Question: How do seed germination and subsequent seedling survival of O. semicastrata (Hance forma litchiifolia How) vary with respect to distance from parent trees and conspecific density in different types of tropical forest? Are there effects of soil biota on O. semicastrata that systematically depend on distance from parent trees and conspecific density? Do soil pathogens differently affect survival of O. semicastrata in different types of tropical forest? Location: Tropical lowland rain forest and tropical montane rain forest in Jianfengling National Nature Reserve, Hainan Island, China. Methods: Individual adult O. semicastrata trees were selected in lowland rain forest and montane rain forest. Soil was collected at a distance of 0‐5 m or 15‐20 m from the parent tree. Soil samples from each distance were combined into a bulk sample. Half of the soil sample was sterilized by autoclaving. Surface‐sterilized seeds were then added to the soil material in shade‐houses at both forests. Results: Germination of O. semicastrata seeds at low‐ or high‐seed density was barely affected by the sterilization procedure. In both forests, seedlings grown in non‐sterilized soil collected close to parent trees had significantly higher mortality compared to those in sterilized soil. In contrast, seedling survival with soil collected far from parent trees was not affected by the soil sterilization procedure. Conclusions: Host‐specific pathogens concentrated in the soil around parent trees may regulate community structure of tropical trees at the stage of seedling development.     

Density‐dependence in common tree species in a tropical dry forest in Mudumalai,southern India

Abstract. Density‐dependence in tree population dynamics has seldom been examined in dry tropical forests. Using long‐term data from a large permanent plot, this study examined 16 common species in a dry tropical forest in southern India for density‐dependence. Employing quadrat‐based analyses, correlations of mortality, recruitment and population change with tree densities were examined. Mortality in 1–10 cm diameter trees was largely negatively correlated with conspecific density, whereas mortality in > 10 cm diameter trees was positively correlated. Mortality was, however, largely unaffected by the basal area and abundance of heterospecific trees. Recruitment was poor in most species, but in Lagerstroemia microcarpa (Lythraceae), Tectona grandis (Verbenaceae) and Cassia fistula (Fabaceae), species that recruited well, strong negative correlations of recruitment with conspecific basal area and abundance were found. In a few other species that could be tested, recruitment was again negatively correlated with conspecific density. In Lagerstroemia, recruitment was positively correlated with the basal area and abundance of heterospecific trees, but these correlations were non‐significant in other species. Similarly, although the rates of population change were negatively correlated with conspecific density they were positive when dry‐season ground fires occurred in the plot. Thus, the observed positive density‐dependence in large‐tree mortality and the negative density‐dependence in recruitment in many species were such that could potentially regulate tree populations. However, repeated fires influenced density‐dependence in the rates of population change in a way that could promote a few common species in the tree community.