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Cerberiopsis candelabra Vieill. is a long-lived, monocarpic (= semelparous) and mass-flowering rain-forest tree, endemic to New Caledonia. Population size structures suggest establishment has been episodic, followed by a recruitment gap that might signal population decline. Here, we use age structures based on tree rings to better assess population dynamics and persistence, and investigate influences of tree size, age and growth rate on flowering. Age structures of populations surveyed in 2007–2008 were unimodal, with establishment over c. 15–81 y, followed by a recruitment gap of c. 23–79 y. Seedling mortality was generally high. High densities of flowering trees or large-scale exogenous disturbances may be necessary for in-situ regeneration. There was no evidence of a simple flowering threshold: flowering in 2017 occurred across a wide range of tree size, age and growth rate. Instead, evidence suggested that size and age at flowering may vary among plants depending on their growth trajectory. Environmental triggers of flowering were not identified by dating tree establishment, but the last three mass-flowering events occurred in years of tropical cyclones. Regeneration and persistence might be facilitated if large-scale disturbances trigger flowering, improving reproductive efficiency by synchronising flowering and linking reproduction with environmental conditions that enhance seedling recruitment.

The high mortality and low recruitment of the myrmecophytic Acacia drepanolobium are not consistent with the demographic rates of monodominant species. The positive conspecific density dependence observed from the spatial analysis is consistent with the defensive benefits conferred by symbiotic ants to trees when they grow close to each other. Patches of savanna dominated by Acacia drepanolobium occur throughout East Africa on nutrient-rich vertisols, also known as black cotton soils. We assessed the survival and recruitment for all freestanding trees with diameter at knee height (dkh) ≥ 10 mm in one of such mono-dominated patches (47 ha) at the Mpala Research Centre, Kenya, with the aim of identifying demographic traits that might explain the dominance of this species. Over a mean 6-year interval, mortality and recruitment rates in the habitat were 4.55%/year and 1.42%/year respectively, resulting in a net loss of 17.8% of the initial individuals. Of the 30 species recorded from the first census, 11 decreased in abundance, nine increased, and the remainder 10 did not change in abundance. The monodominant A. drepanolobium had a high mortality (4.69%/year), a low recruitment (1.31%/year), and a 19% population decline. There was no evidence of conspecific negative density dependence for this species. Rather, we found a statistically significant positive correlation between the number of conspecific neighbors and individual-level probability of survival, consistent with the “shared defense” benefits that symbiotic ant colonies occupying multiple trees can confer to these latter in a small neighborhood. Thus, mortality of A. drepanolobium was higher in areas where it occurred in lower densities, which resulted in an increase in the spatial aggregation of conspecifics. Mortality increased with dkh size classes and was mostly caused by elephants and stem-boring beetles. The demographic rates during the study period in theory are inconsistent with those of monodominant species. The protection against herbivory conferred by mutualistic ants associated with this species remains the most probable explanation of its dominance in this habitat.

The long-term dynamics of regeneration in tropical forests dominated by single tree species remains largely undocumented, yet is key to understanding the mechanisms by which one species can gain dominance and resist environmental change. We report here on the long-term regeneration dynamics in a monodominant stand of Brosimum rubescens Taub. (Moraceae) at the southern border of the Amazon forest. Here the climate has warmed and dried since the mid-1990′s. Twenty-one years of tree and liana regeneration were evaluated in four censuses in 30 plots by assessing species abundance, dominance, and diversity in all regeneration classes up to 5 cm diameter. The density of B. rubescens seedlings declined markedly, from 85% in 1997 to 29% in 2018 after the most intense El Niño-driven drought. While the fraction contributed by other tree species changed little, the relative density of liana seedlings increased from just 1 to 54% and three-quarters of liana species underwent a ten-fold or greater increase in abundance. The regeneration community experienced a high rate of species turnover, with changes in the overall richness and species diversity determined principally by lianas, not trees. Long-term maintenance of monodominance in this tropical forest is threatened by a sharp decline in the regeneration of the monodominant species and the increase in liana density, suggesting that monodominance will prove to be a transitory condition. The close association of these rapid changes with drying indicates that monodominant B. rubescens forests are impacted by drought-driven changes in regeneration, and therefore are particularly sensitive to climatic change.

QUESTION: The existence of monodominant forest in highly diverse tropical rainforest has been the subject of much debate. One hypothesis suggests that the combination of advantageous traits and long periods of low disturbance is key for this forest's persistence. Here we ask whether there is evidence for the long‐term presence of monodominant Gilbertiodendron forest in the absence of fire and climate change. LOCATION: Republic of Congo. METHODS: We extracted fossil pollen and macro‐charcoal from a sediment sequence collected in present‐day monodominant Gilbertiodendron forest stand that spans the last 2,700 years. Climatic changes were inferred using other published palaeoecological records from Central Africa. We also looked at Gilbertiodendron dewevrei's present‐day ecological tolerances. RESULTS: Gilbertiodendron pollen was found in every sample covering the last 2,700 years in similar percentages to present‐day soil surface samples. In addition, no statistically significant change in pollen composition was found during this time despite vegetation changes being documented in nearby mixed and swamp forest cores over the same time period. No evidence of fire was found for a period of 2,400 years. Only minimal burning occurred over the last 300 years in this monodominant stand. The analysis of ecological tolerances shows G. dewevrei has a broad niche for precipitation (1,300–2,460 mm). CONCLUSIONS: Our pollen record is the first to describe the long‐term ecological history of an African monodominant forest. Our results show this monodominant stand existed over the past 2,700 years mostly in the absence of fire, providing support for the low disturbance hypothesis as an explanation for monodominance persistence. However, we show that the monodominant forest was continuous, at this site, despite climatic fluctuations in the immediate region. This combined with the broad tolerance of water requirements of the species suggests a potential resilience to future climate variability. However, additional pollen records from a wider area are needed to confirm this.

The OCBIL theory comprises a set of hypotheses to comprehend the biota of old, climatically buffered, infertile landscapes (OCBILs). Here, we review evidence from the literature to evaluate the extent to which this theory could apply to the biodiversity hotspot of New Caledonia. We present geological, pedological and climatic evidence suggesting how the island might qualify as an OCBIL. The predictions of OCBIL theory are then reviewed in the context of New Caledonia. There is evidence for a high rate of micro-endemism, accumulation of relict lineages, a high incidence of dioecy, myrmecochory and nutritional specializations in plants. New Caledonian vegetation also exhibits several types of monodominant formations that reveal the importance of disturbances on the island. Fires and tropical storms are likely to be important factors that contribute to the dynamic of New Caledonian ecosystems. Although naturally infertile, there is archaeological evidence that humans developed specific horticultural practices in the ultramafic landscapes of New Caledonia. Further comparisons between New Caledonia and other areas of the world, such as South Africa and Southwest Australia, are desirable, to develop the OCBIL theory into a more robust and generalized, testable framework and to determine the most efficient strategies to preserve their outstanding biodiversity.

The mechanisms regulating community composition and local dominance of trees in species-rich forests are poorly resolved, but the importance of interactions with soil microbes is increasingly acknowledged. Here, we show that tree seedlings that interact via root-associated fungal hyphae with soils beneath neighbouring adult trees grow faster and have greater survival than seedlings that are isolated from external fungal mycelia, but these effects are observed for species possessing ectomycorrhizas (ECM) and not arbuscular mycorrhizal (AM) fungi. Moreover, survival of naturally-regenerating AM seedlings over ten years is negatively related to the density of surrounding conspecific plants, while survival of ECM tree seedlings displays positive density dependence over this interval, and AM seedling roots contain greater abundance of pathogenic fungi than roots of ECM seedlings. Our findings show that neighbourhood interactions mediated by beneficial and pathogenic soil fungi regulate plant demography and community structure in hyperdiverse forests., Associations with mycorrhizal fungi can affect the outcome of plant competition in complex ways. Here the authors use a decade-long field survey and two hyphal exclusion experiments to reveal a critical role of underground fungal networks in facilitating seedling growth and fitness of ectomycorrhizal plants but not arbuscular mycorrhizal plants.

The conspecific negative density dependence hypothesis states that mortality of young trees (seedlings and saplings) is higher near conspecific adults due to mechanisms such as allelopathy, intraspecific competition, and pest facilitation, explaining why in the tropics, most of plant species tend to be rare and live dispersed. However, there are some tree species that defy this expectation and grow in large clusters of conspecific juveniles and adults. We hypothesize that conspecifics living in clusters show higher and/or more variable defensive profiles than conspecifics with dispersed distributions.We evaluated our hypothesis by assessing the expression of physical leaf traits (thickness, and the resistance to punch, tear and shear) and leaf chemical defenses for six clustered and six non‐clustered tree species in Yasuní National Park, Ecuadorian Amazon. We ask ourselves whether (a) clustered species have leaves with higher physical resistance to damage and more chemical defenses variability than non‐clustered species; (b) saplings of clustered species may show higher physical resistance to damage and higher variation on chemical leaf defenses than their conspecific adults, and (c) saplings of non‐clustered species show lower resistance to physical damage and lower variation in chemical defenses compared to conspecific adults.Overall, our study did not support any of our hypotheses. Remarkably, we found that soluble metabolites were significantly species‐specific.Our study suggests that plants physical but not chemical leaf antiherbivore defenses may be a crucial strategy for explaining survivorship of clustered species. Trees in Yasuní may also fall along a suite of tolerance/escape/defense strategies based on limitations of each species physiological constraints for survival and establishment. We conclude that other mechanisms, such as those related to indirect defenses, soil nutrient exploitation efficiency, volatile organic compounds, delayed leaf‐greening, and seed dispersal mechanisms, shall be evaluated to understand conspecific coexistence in this forest.

Floating meadows are widespread globally, but ecological information on their vegetation structure and functions is lacking. We examined the structure and composition of the vegetation of the floating meadows of Keibul Lamjao National Park, Manipur, located in the Indo-Burma Biodiversity Hotspot. The floating meadows in the park are crucial for the survival of the globally threatened Eld’s deer (Rucervus eldii) and the hog deer (Axis porcinus). Vegetation data were collected from 936 plots of size 0.5 m × 0.5 m during winter and summer. The vegetation data were analyzed using two-way indicator species analysis (TWINSPAN) with PC-ORD version 4.20. Nine plant communities were observed in summer and eight in winter, with two communities being common to the two seasons. The overall Shannon and Simpson diversity indices, species richness and evenness of the communities varied significantly between summer and winter. The evenness (0.713) and diversity (H′, 1.335) indices in summer indicate high species diversity, which is mainly due to homogenous distribution of the species. The Ivlev Electivity Index (IVI) indicates that plant communities have a specific preference for meadow thickness, i.e., communities that prefer thick meadows avoid thin meadows. Competition among plant communities in terms of moisture and nutrient availability appears to be low due to the hypereutrophic condition of the lake and the floating nature of the meadows. But Capillipedium spp., Phragmites karka, Leersia hexandra and Zizania latifolia appear to exhibit monodominance, as indicated by their frequency and abundance in most of the communities. Protection of areas with thick meadow from further deterioration is crucial for the long-term conservation of the Eld’s deer and associated wild ungulates.

The invasive liana Euonymus fortunei (Turcz.) Hand.-Maz. (wintercreeper) is an emerging invader that through monodominance of woodlands can drastically reduce native species diversity and alter nutrient cycling. We studied how the vegetation and soils of invaded (INV), “native” (NAT), and wintercreeper removal (REM) site treatments influenced seed germination and seedling survival of this invader. The effect of aril (with vs. without) was also tested for wintercreeper seeds under field and in vitro conditions as a proxy for gravity vs. animal dispersal of seed, respectively. Germination was significantly delayed for seeds sown with an aril (vs. without), as well as those sown in INV soils (vs. NAT or REM), but neither site nor aril affected total germination. The proportion of germinated seedlings that survived after the first winter was significantly different based on site (p = 0.054) and aril (p = 0.071) treatments, with lower survival resulting from seeds sown without arils, and for seeds sown in INV sites. Magnesium (Mg) concentrations were significantly higher among INV soils (vs. NAT) and provide further support that wintercreeper is a driver of soil nutrient change. Our findings that aril-enclosed (gravity-dispersed) seeds yielded greater survival, despite being locally dispersed within invaded sites (where survival was lowest), support the historically slow rate of spread for this species.

Monodominant forests are characterized by the strong influence of a single species on the structure and diversity of the community. In the tropics, monodominant forests are rare exceptions within the generally highly diverse tropical forest biome. Some studies have shown that tree monodominance may be a transient state caused by successional and demographic variation among species over time. Working in a Brosimum rubescens Taub. (Moraceae) monodominant forest at the southern edge of Amazonia, we tested the hypotheses that local-scale variation in intra- and interspecific spatial patterns of dominant tree species is affected by i) demographic rates of recruitment and mortality following severe droughts, ii) local variation in edaphic properties, and iii) occupation of species in the vertical layer of the forest. We quantified intra- and interspecific spatial patterns and edaphic associations of the five most abundant species using aggregation and association distance indices, and examined changes over time. We found some support for all hypotheses. Thus, intra- and interspecific spatial patterns of most species varied over time, principally after severe drought, emphasizing species-level variability and their interactions in sensitivity to this disturbance, even as B. rubescens monodominance was maintained. While positive and negative spatial associations with edaphic properties provide evidence of habitat specialization, the absence of negative spatial associations of B. rubescens with edaphic properties indicates that this species experiences little environmental restriction, and this may be one of the factors that explain its monodominance. Spatial repulsion and attraction between species in the same and in different vertical layers, respectively, indicates niche overlap and differentiation, while changes over time indicate that the relationships between species are dynamic and affected by drought disturbance.

Soil has been proposed as a driver explaining the development of monodominant forests in the tropics, for example, Gilbertiodendron dewevrei forests (GDF) in central Africa. The aim of this study was to compare the physical and chemical properties of soils under GDF with those under an adjacent mixed forest (AMF), while controlling for topography. To this end, we set up sixteen 0.25-ha plots according to forest type and topography (plateau vs. bottomland), in the Yoko forest reserve, Democratic Republic of Congo. In each plot, we measured litter thickness and collected a total of 80 soil samples at depths of 0–5, 5–10, 10–20, 20–40 and 120–150 cm, for standard physical and chemical analyses. When controlling for topography and soil texture, we found that most of the chemical properties of soils under GDF did not differ from those of soils under AMF, particularly acidity, cation concentration, total N and the C:N ratio. The litter layer was 2.3 times thicker under GDF than under AMF stands, and, for a given texture, soils under GDF had a slightly higher organic C concentration in the 0–5 cm soil layer. This study suggests that G. dewevrei stands modify organic matter dynamics, which may be important in maintaining its monodominance.

Plant-soil feedback (PSF) can structure plant communities, promoting coexistence (negative PSF) or monodominance (positive PSF). At higher trophic levels, predators can alter plant community structure by re-allocating resources within habitats. When predator and plant species are spatially associated, predators may alter the outcome of PSF. Here, I explore the influence of plant-associated predators on PSF using a generalised cellular automaton model that tracks nutrients, plants, herbivores and predators. I explore key contingencies in plant-predator associations such as whether predators associate with live vs. senesced vegetation. Results indicate that plant-associated predators shift PSF to favour the host plant when predators colonise live vegetation, but the outcome of PSF will depend upon plant dispersal distance when predators colonise dead vegetation. I apply the model to two spider-associated invasive plants, finding that spider predators should shift PSF dynamics in a way that inhibits invasion by one forest invader, but exacerbates invasion by another.

The viability of propagules during topsoil stockpiling is a limiting factor in ecological restoration projects and little is known about the species distributed in the campos de altitude. This work was carried out to investigate the viability of propagules present in the topsoil under campos de altitude vegetation, stockpiled for up to 12 months after the stripping of areas to be mined. In the south of Minas Gerais, Brazil, between November 2011 and November 2012, four collections of the seed bank were carried out, considering three depths (0 to 10, 90 to 100, and 190 to 200 cm) of the plot of stockpiled topsoil. Using the multivariate analysis, it was verified that the depth factor does not statistically affect the abundance of emerged individuals, while the factor time of stockpiling negatively affects the viability of the seeds. Some species were affected by the stockpiling conditions, only emerging in some collections, while others (Achyrocline satureioides, Ageratum fastigiatum, Baccharis dracunculifolia, Borreria capitata, Echinolaena inflexa and Melinis minutiflora) had individuals emerged in all collection periods. This study points out the need for the return of the topsoil until the fourth month of stocking, under the risk of monodominance, with a prevalence of species more adapted to predominant conditions of campos de altitude. RESUMO A viabilidade dos propágulos durante a estocagem de topsoil é um fator limitante em projetos de restauração ecológica, e pouco se sabe sobre as espécies distribuídas nos campos de altitude. Este trabalho foi realizado com o objetivo de investigar a viabilidade de propágulos presente no topsoil sob vegetação de campos de altitude, estocado por até 12 meses após o decapeamento de áreas a serem mineradas. Entre o período de novembro de 2011 a novembro de 2012 foram realizadas quatro coletas do banco de sementes, sendo consideradas três profundidades (0 a 10, 90 a 100 e 190 a 200 cm) da leira de topsoil estocada. Utilizando a análise multivariada, verificou-se que o fator profundidade não afeta estatisticamente a abundância de indivíduos emergidos, enquanto o fator tempo de estocagem afeta negativamente a viabilidade das sementes. Algumas espécies foram afetadas pelas condições de estoque do topsoil, emergindo somente em algumas coletas, enquanto outras (Achyrocline satureioides, Ageratum fastigiatum, Baccharis dracunculifolia, Borreria capitata, Echinolaena inflexa e Melinis minutiflora) tiveram indivíduos emergidos em todos os períodos de coleta. Este estudo aponta a necessidade do retorno do topsoil até o quarto mês de armazenamento, sob o risco de ocorrer monodominância, com predominância de espécies mais adaptadas as condições campestres.

Contains fulltext : 225690.pdf (Publisher’s version ) (Open Access) Abstract Plant-soil legacies consisting of species-specific microbial communities are hypothesized to play a critical, structuring role in plant species coexistence processes. Plant species are thought to perform worse on soil conditioned by the same species compared to soil of other species, which serves as a self-limitation mechanism and averts monodominance of strong competitors. Here, we test in a multispecies community setting, whether root colonization and resource utilization of soil patches with distinct soil legacies are consistent with this hypothesis. We grew eight grassland species together in an outdoor mesocosm set-up in unconditioned soil and created soil patches in these communities conditioned by one of four plant species, or a soil mixture of all four. During two subsequent growing seasons, we tested the effect of these conditioned soil patches on below-ground root colonization into the patches of each surrounding plant species using a novel sequencing-based approach. In addition, we tested the effect of soil conditioning on local root functioning by injecting tracers into the soil patches and measuring the recovery in above-ground biomass. Against expectations, plant species did not place less roots in own soil patches compared to foreign soil patches, nor did species take up less tracer from own compared to foreign soil patches. Using structural equation modelling, we found that tracer uptake of the plant species was to a varying degree explained by root densities in the various soil patches and by differing soil nutrient availability of the soil patches. We conclude that soil legacy effects are inextricably connected to soil nutrient availability, which needs to be taken into account in plant-soil feedback research to understand the processes that shape plant communities. Synthesis. We found that soil legacy effects in complex, multispecies semi-field conditions did not match expectations based on theory and experiments in controlled conditions. Among the many complicating factors that may modify or even overrule soil legacy effects in semi-field settings, we identified soil nutrient availability as a critical force that may, together with soil biota, shape plant species coexistence processes. 13 p.

Negative plant-soil feedback (PSF) , where plant performance is reduced in soils conditioned by conspecifics, are widely documented in plant communities. However, the strength and sometimes direction of PSF can vary widely, presumably due to environmental context. We hypothesized that soil fertility and light availability influence the direction and strength of plant-soil feedback experienced by tree seedlings. We conducted a 10-week greenhouse experiment and assessed survivorship of black cherry (Prunus serotina) in low (~1% full sun) vs. high (~18% full sun) light availability and in non-sterile vs. sterile soils collected under the canopy of conspecific vs. heterospecific adult trees at five sites that vary in nutrient availability in Manistee National Forest, Michigan, USA. Northern red oak (Quercus rubra) also was included in the experiment, but no seedlings died and thus there are no survivorship responses to report. Prunus serotina seedlings experienced microbe-mediated negative plant-soil feedback in low fertility sites (higher C:N ratios and lower NH4+) but positive feedback at high fertility sites, but these feedbacks occurred only under high light availability. Consistent with these results, microbe-mediated negative PSF increased with soil Fe3+ and C:N ratios and decreased with NH4+. Thus lower fertility soils, characterized by high C:N and Fe3+availability and low NH4+, are associated with stronger negative conspecific feedback for P. serotina seedlings. Conversely, higher fertility soils flip the feedback to positive. Our results demonstrate the important role of environmental context, specifically light and soil nutrient availability, on the magnitude and direction of conspecific plant soil feedback. Thus, PSF is likely an important driver in plant community dynamics that may be either destabilizing (promote species coexistence) or stabilizing (promote monodominance) depending upon environmental context.

Monodominant patches of forest dominated by Gilbertiodendron dewevrei are commonly found in central African tropical forests, alongside forests with high species diversity. Although these forests are generally found sparsely distributed along rivers, their occurrence is not thought to be (clearly) driven by edaphic conditions but rather by trait combinations of G. dewevrei that aid in achieving monodominance. Functional community structure between these monodominant and mixed forests has, however, not yet been compared. Additionally, little is known about nondominant species in the monodominant forest community. These two topics are addressed in this study. We investigate the functional community structure of 10 one-hectare plots of monodominant and mixed forests in a central region of the Congo basin, in DR Congo. Thirteen leaf and wood traits are measured, covering 95% (basal area weighted) of all species present in the plots, including leaf nutrient contents, leaf isotopic compositions, specific leaf area, wood density, and vessel anatomy. The trait-based assessment of G. dewevrei shows an ensemble of traits related to water use and transport that could be favorable for its location near forest rivers. Moreover, indications have been found for N and P limitations in the monodominant forest, possibly related to ectomycorrhizal associations formed with G. dewevrei. Reduced leaf N and P contents are found at the community level for the monodominant forest and for different nondominant groups, as compared to those in the mixed forest. In summary, this work shows that environmental filtering does prevail in the monodominant G. dewevrei forest, leading to lower functional diversity in this forest type, with the dominant species showing beneficial traits related to its common riverine locations and with reduced soil N and P availability found in this environment, both coregulating the tree community assembly.

Gilbertiodendron dewevrei (De Wild.) J.Leonard monodominant forests (MOF) and Scorodophloeus zenkeri Harms mixed forests (MIF) frequently co-occur on similar soil conditions in the Central Congo basin. Although tree species composition is known to impact C storage, the patterns of C sequestration between those contrasted forest types as well as the associated drivers remain unknown. Annual litterfall, as well as soil (forest floor and mineral soil down to 220 cm depth) organic C (SOC) and aboveground C (AGC) stocks were investigated in MIF and MOF located on highly weathered sandy soils in the Yoko Reserve (DRC). The annual leaf litterfall was similar under both forests but litterfall quality in MOF strongly differed by a set of traits related to organic matter recalcitrance. The SOC stock down to 220 cm was 55% higher under MOF compared to MIF, and the differences between forests remained significant down to 100 cm. While the combined SOC and AGC stocks were similar in both forests, the SOC stocks accounted for ca. 19 and 33% of the total C stocks in MIF and MOF, respectively. Because of similar litterfall C inputs, we conclude that the greater SOC accumulation under G. dewevrei results from a limitation of the decomposition rate, in agreement with the traits of the corresponding leaf litter.

Environmental filters affect species diversity. Understanding their influence on plant communities is one of the main challenges of ecology in the search for solutions to the management and conservation of floodable savannas. To shed more light on this challenge, the present work asked if the interactions between flood and fire influence the richness of community and favor the abundance and basal area of the monodominant Pantanal species Tabebuia aurea. We also asked what role earth-mounds play in this process. To address these questions, we used Landsat-5 and -8 and Resourcesat-1 satellite data; to access the fire history in monodominant stands of T. aurea in the Pantanal from 2003 to 2017. We chose 37 areas with 2 to 9 annual fire episodes. A total of 125 25 × 25 m plots were established in the different areas, to sample arboreal strata. We sampled all individuals ≥3.18 cm in diameter at breast height (dbh). In each plot, we measured height by the watermark from the last flooding on each individual as a proxy of inundation level. We applied generalized linear model (GLM) analyses to compare effects of flood and fire on abundance, richness and basal area, on and off earth-mounds using negative binomial, Poisson and Gaussian distribution, respectively. We sampled 2411 individuals distributed among 19 families, 31 genera and 36 species. Under higher fire frequency, abundance, richness and basal area of all species decreased with increase of water level. However, the abundance and basal area of Tabebuia aurea remained higher than those of other species. Under lower fire frequency, the abundance and richness of all species in the community increased with water level. Basal area, however, decreased with increasing water level, such that individuals with larger basal area were found under lower fire frequency. Under high fire frequency earth-mounds protected T. aurea individuals from fire and flood. Earth-mounds influenced species richness and basal area only under medium-low fire frequency. Results show that monodominance of T. aurea benefits from the interaction between fire and flood, with some help from earth-mounds. Individuals of other tree species, show tolerance to high flood levels or high fire frequencies, but not the interaction between fire and flood. This dynamic strengthens the monodominance of T. aurea, as the number of individuals also increases. Our results show that flood and fire are important to the conservation of this monodominant community.

Made available in DSpace on 2020-12-12T01:40:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-12-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Tropical forests are known for their high diversity. Yet, forest patches do occur in the tropics where a single tree species is dominant. Such “monodominant” forests are known from all of the main tropical regions. For Amazonia, we sampled the occurrence of monodominance in a massive, basin-wide database of forest-inventory plots from the Amazon Tree Diversity Network (ATDN). Utilizing a simple defining metric of at least half of the trees ≥ 10 cm diameter belonging to one species, we found only a few occurrences of monodominance in Amazonia, and the phenomenon was not significantly linked to previously hypothesized life history traits such wood density, seed mass, ectomycorrhizal associations, or Rhizobium nodulation. In our analysis, coppicing (the formation of sprouts at the base of the tree or on roots) was the only trait significantly linked to monodominance. While at specific locales coppicing or ectomycorrhizal associations may confer a considerable advantage to a tree species and lead to its monodominance, very few species have these traits. Mining of the ATDN dataset suggests that monodominance is quite rare in Amazonia, and may be linked primarily to edaphic factors. Biodiversity Dynamics Naturalis Biodiversity Center, PO Box 9517 Systems Ecology Free University, De Boelelaan 1087 Department of Biological Sciences Humboldt State University, 1 Harpst Street Programa de Pós-Graduação em Ecologia e Conservação Universidade do Estado de Mato Grosso Department of Ecological Modelling Helmholtz Centre for Environmental Research - UFZ, Permoserstr. 15 Institute of Forest Growth and Computer Sciences Technische Universitaet Dresden, Postfach 1117 AMAP IRD CIRAD CNRS INRA Université de Montpellier, TA A-51/PS2, Bd. de la Lironde, A comprehensive Coordenação de Biodiversidade Instituto Nacional de Pesquisas da Amazônia - INPA, Av. André Araújo, 2936, Petrópolis Programa Professor Visitante Nacional Sênior na Amazônia - CAPES Universidade Federal Rural da Amazônia, Av. Perimetral, s/n Coordenação de Botânica Museu Paraense Emílio Goeldi, Av. Magalhães Barata 376, C.P. 399 EMBRAPA – Centro de Pesquisa Agroflorestal de Roraima, BR 174, km 8 – Distrito Industrial School of Geography University of Leeds, Woodhouse Lane Grupo de Investigación en Biodiversidad Medio Ambiente y Salud-BIOMAS Universidad de las Américas, Campus Queri Keller Science Action Center The Field Museum, 1400S. Lake Shore Drive Departamento de Botânica Instituto de Pesquisas Científicas e Tecnológicas do Amapá - IEPA, Rodovia JK, Km 10, Campus do IEPA da Fazendinha Herbario Amazónico Colombiano Instituto SINCHI, Calle 20 No 5-44 Coordenação de Pesquisas em Ecologia Instituto Nacional de Pesquisas da Amazônia - INPA, Av. André Araújo, 2936, Petrópolis Dep. of Wetland Ecology Institute of Geography and Geoecology Karlsruhe Institute of Technology - KIT, Josefstr.1 Biogeochemistry Max Planck Institute for Chemistry, Hahn-Meitner Weg 1 Naturalis Biodiversity Center, PO Box 9517 Coordenação de Dinâmica Ambiental Instituto Nacional de Pesquisas da Amazônia - INPA, Av. André Araújo, 2936, Petrópolis Science and Education The Field Museum, 1400S. Lake Shore Drive Jardín Botánico de Missouri Departamento de Ecologia Universidade Estadual Paulista - UNESP – Instituto de Biociências – IB, Av. 24A, 1515, Bela Vista Divisao de Sensoriamento Remoto – DSR Instituto Nacional de Pesquisas Espaciais – INPE, Av. dos Astronautas, 1758, Jardim da Granja Herbario Vargas Universidad Nacional de San Antonio Abad del Cusco, Avenida de la Cultura, Nro 733 Departamento de Geografia Universidade Estadual Paulista -UNESP – Instituto de Geociências e Ciências Extas – IGCE Bela Vista Centro de Biociências Departamento de Ecologia Universidade Federal do Rio Grande do Norte, Av. Senador Salgado Filho, 3000 Departamento de Biologia Universidade Federal de Rondônia, Rodovia BR 364s/n Km 9,5 - Sentido Acre, Unir Programa de Pós- Graduação em Biodiversidade e Biotecnologia PPG- Bionorte Universidade Federal de Rondônia, Campus Porto Velho Km 9,5 bairro Rural Department of Biology and Florida Museum of Natural History University of Florida Centre for Tropical Environmental and Sustainability Science and College of Science and Engineering James Cook University Instituto de Investigaciones de la Amazonía Peruana (IIAP), Av. A. 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The upper canopy of some rain forests in New Caledonia is dominated by single species. These monodominants are commonly secondary species, their dominance not persisting without disturbance. We tested whether dominance is associated with efficient uptake and use of nutrients (N, P and K), comparing between seedlings of monodominants (Nothofagus spp., Arillastrum gummiferum and Cerberiopsis candelabra) and 14 subordinates, grown in a nursery house. We also tested whether this trend applies more broadly to shade-intolerant trees that regenerate episodically (ER species) versus shade-tolerant trees that regenerate continuously (CR species). In the sun treatment, monodominants had higher photosynthetic nutrient-use efficiency and productivity for N and K, and uptake efficiency for N, P and K, than subordinates; ER species had higher photosynthetic nutrient-use efficiency for N, P and K, and uptake efficiency for N and P, than CR species. Uptake efficiency and productivity per nutrient mass were uncorrelated across species, yet Nothofagus spp., A. gummiferum and C. candelabra combined high levels of both traits for N, and Nothofagus spp. and A. gummiferum combined moderate to high levels for P, in sun-grown seedlings. This trait combination may contribute substantially to competitiveness and post-disturbance dominance on these nutrient-poor soils.

Contents Summary 1076 I. Introduction 1076 II. Historical overview 1077 III. Identities and distributions of tropical ectomycorrhizal plants 1077 IV. Dominance of tropical forests by ECM trees 1078 V. Biogeography of tropical ECM fungi 1081 VI. Beta diversity patterns in tropical ECM fungal communities 1082 VII. Conclusions and future research 1086 Acknowledgements 1087 References 1087 SUMMARY: Ectomycorrhizal (ECM) associations were historically considered rare or absent from tropical ecosystems. Although most tropical forests are dominated by arbuscular mycorrhizal (AM) trees, ECM associations are widespread and found in all tropical regions. Here, we highlight emerging patterns of ECM biogeography, diversity and ecosystem functions, identify knowledge gaps, and offer direction for future research. At the continental and regional scales, tropical ECM systems are highly diverse and vary widely in ECM plant and fungal abundance, diversity, composition and phylogenetic affinities. We found strong regional differences among the dominant host plant families, suggesting that biogeographical factors strongly influence tropical ECM symbioses. Both ECM plants and fungi also exhibit strong turnover along altitudinal and soil fertility gradients, suggesting niche differentiation among taxa. Ectomycorrhizal fungi are often more abundant and diverse in sites with nutrient-poor soils, suggesting that ECM associations can optimize plant nutrition and may contribute to the maintenance of tropical monodominant forests. More research is needed to elucidate the diversity patterns of ECM fungi and plants in the tropics and to clarify the role of this symbiosis in nutrient and carbon cycling.

Various explanations have been put forward for monodominance in otherwise diverse tropical forests. This study assesses if the monodominance of Peltogyne gracilipes on Maraca Island in the northern Amazon can be related to edaphic factors. The basal area of P. gracilipes and the five other most common tree species on Maraca Island (Astrocaryum aculeatum, Attalea maripa, Ecclinusa guianensis, Licania kunthiana and Pradosia surinamensis) were recorded in 30 regularly-spaced 0.5 ha plots distributed over an area of 25 km2, for which data on topography and concentration of mineral elements in the soil were also obtained. Stems of P. gracilipes accounted for ≥50% of the basal area in five of the plots, which we consider indicative of monodominance, whilst the highest relative basal area that any of the other species achieved in any plot was 31%. The soils data explained more of the variation in the basal area of P. gracilipes than it did for the other five species. The presence vs. absence and basal area of P. gracilipes was positively related to concentrations of magnesium (Mg), aluminium (Al), iron (Fe), phosphorus (P) and silt in the soil and to Mg:Ca ratios. These soils were found in the plots at the lowest elevations, which suggests that drainage factors may also be important. Overall, our results suggest that edaphic factors may explain, at least partially, monodominance in this Amazonian forest.

Some species-rich secondary forests in New Caledonia have a monodominant canopy. Here we investigate growth and biomass allocation traits that might explain single-species’ dominance of these post-disturbance stands, and their later decline in the absence of large-scale disturbance. Seedlings of 20 rain-forest trees were grown in two light treatments in a nursery house. In the sun treatment, monodominants grew faster (56.7 ± 1.4 mg g−1 wk−1) than subordinates (40.2 ± 2.6 mg g−1 wk−1). However, some episodically regenerating (ER) subordinates had high growth rates similar to those of monodominants. In the shade treatment, monodominants and subordinates had similar growth rates (33.7 ± 2.6 and 34.0 ± 1.9 mg g−1 wk−1 respectively). Notably, monodominants in both sun and shade treatments had lower root mass fraction (0.29 ± 0.02 and 0.27 ± 0.02 g g−1 respectively) than subordinates (0.39 ± 0.02 and 0.37 ± 0.02 g g−1). Fast growth in sunny conditions is probably imperative for these relatively shade-intolerant ER monodominants. In field conditions, high shoot mass fraction combined with efficient root performance may facilitate faster growth in monodominants competing with other ER species in sunlit sites. Slower growth in shade may contribute to loss of dominance over time in undisturbed forests.

Monodominant tropical forests occur on several continents, including the Brazilian Amazon. In this study, we tested the hypothesis that seedling escape from leaf herbivory contributes to the maintenance of the monodominant Brosimum rubescens forest. The study was undertaken both in a monodominant forest of B. rubescens and in an adjacent seasonal forest in the transitional zone between the Cerrado and the Amazonian forest biomes. Percentage of leaf area damaged and herbivory rates were evaluated on young and mature leaves of seedlings of Brosimum rubescens, Protium pilosissimum and Tetragastris altissima in the understory and in the gap between the monodominant and seasonal forests. Little evidence of any significant relationship between leaf herbivory and seedling density indicates that the monodominant species does not follow the hypothesized pattern of an intensive herbivore attack in areas of higher seedling density. The escape of Brosimum rubescens from herbivore pressure under conditions of high see...

Aim Large trees (d.b.h. 70 cm) store large amounts of biomass. Several studies suggest that large trees may be vulnerable to changing climate, poten- tially leading to declining forest biomass storage. Here we determine the importance of large trees for tropical forest biomass storage and explore which intrinsic (species trait) and extrinsic (environment) variables are associated with the density of large trees and forest biomass at continental and pan-tropical scales. Location Pan-tropical.

International audience; Convergence occurs in both species traits and community structure, but how convergence at the two scales influences each other remains unclear. To address this question, we focus on tropical forest monodominance, in which a single, often ectomycorrhizal (EM) tree species occasionally dominates forest stands within a landscape otherwise characterized by diverse communities of arbuscular mycorrhizal (AM) trees. Such monodominance is a striking potential example of community divergence resulting in alternative stable states. However, it is observed only in some tropical regions. A diverse suite of AM and EM trees locally codominate forest stands elsewhere. We develop a hypothesis to explain this geographical difference using a simulation model of plant community assembly. Simulation results suggest that in a region with a few EM species (e.g., South America), EM trees experience strong selection for convergent traits that match the abiotic conditions of the environment. Consequently, EM species successfully compete against other species to form monodominant stands via positive plant-soil feedbacks. By contrast, in a region with many EM species (e.g., Southeast Asia), species maintain divergent traits because of complex plant-soil feedbacks, with no species having traits that enablemonodominance. An analysis of plant trait data from Borneo and Peruvian Amazon was inconclusive. Overall, this work highlights the utility of geographical comparison in understanding the relationship between trait convergence and community convergence.

Bamboos play an important role in forest dynamics, but management strategies are needed to avoid monodominance. Understanding how climate change would influence the geographic distribution of bamboos could provide management tools for habitat conservation, as well as prevent the expansion of this group. We investigated the distribution patterns of Merostachys species that are endemic to the Brazilian Atlantic Forest, under current and future climate scenarios. We obtained occurrence records based on field collection, herbaria data and online databases. We used the Maxent algorithm to model potential distribution. Future scenarios considered the IPCC forecasted climate for 2070. Our models showed that a reduction in suitable areas for Merostachys species will likely occur, but the existence of suitable areas under climate changes in the Brazilian Atlantic Forest indicates climatic stability in some areas of occurrence of these species in their richness center. Since the fact that in places with local dominance of woody bamboos there is a decrease in the diversity of other plant species, the occurrence of Merostachys throughout the suitable areas may represent risks to biodiversity conservation. Investigations of the synergistic effects of climate change and the local dominance of woody bamboos are required. Therefore, management measures may be very important to control the occurrence of woody bamboos in the Brazilian Atlantic Forest, mainly in climatically stable areas.

Many alien species become invasive because they lack coevolutionary history with the native community; for instance, they may lack specialized enemies. These evolutionary advantages may allow the invader to establish and persist when rare within a community and lead to its monodominance through positive frequency dependence, i.e. increasing per capita population growth rate with increasing frequency of conspecifics. However, this advantage could degrade through time due to evolutionary and ecological changes in the invasive and native plant and microbial communities. We investigated survival rates and individual biomass as proxies for per capita population growth rates for the invasive grass, Microstegium vimineum, across a gradient of conspecific frequencies (10-100% relative cover of M. vimineum) within 12 sites that varied in time since invasion. We expected M. vimineum frequency dependence to become more negative and its proxies for population growth at low conspecific frequency to decline across invasion history. We also explored the belowground fungal community associated with M. vimineum, since we hypothesized that changes in M. vimineum population dynamics may result from shifting microbial interactions over time. Microstegium vimineum frequency dependence changed from negative to neutral across invasion history and the shift was driven by a decline in survival at low frequency. Changes in M. vimineum root fungal community were associated with time since invasion. Our results do not support a shift in frequency dependence from positive to negative across invasion history. However, our results suggest M. vimineum populations may be less prone to persist at older invaded sites and thus more vulnerable to management intervention.

Tropical forests are highly diverse ecosystems, but within such forests there can be large patches dominated by a single tree species. The myriad presumed mechanisms that lead to the emergence of such monodominant areas is currently the subject of intensive research. We used the most generic of these mechanisms, large seed mass and low dispersal ability of the monodominant species, in a spatially explicit model. The model represents seven identical species with long-distance dispersal of small seeds, competing with one potentially monodominant species with short-distance dispersal of large seeds. Monodominant patches emerged and persisted only for a narrow range of species traits; these results have the characteristic features of phase transitions. Additional mechanisms may explain monodominance in different ecological contexts, but our results suggest that percolation-like phenomena and phase transitions might be pervasive in this type of system., M.K. was supported by ERC advanced grant no. 233066. P.B. gratefully acknowledges the support of the German Centre of Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig supported by the German Research Foundation (FZT 118).

The main interest in studying monodominant forests in the tropics (i.e. single-dominant forest sensu Richards 1996 and Connell & Lowman 1989) is that processes leading to monodominance may highlight mechanisms controlling species diversity (Hart et al. 1989). Among the various cases of monodominant forest (Hart 1990), the most intriguing are the rare ones that stand in contact with a considerably more diverse forest, without apparent environmental boundaries, and for many generations (i.e. type I sensu Connell & Lowman 1989). Rather than a single mechanism, it is likely that this type of monodominance results from a suite of interacting traits (Torti et al. 2001). This has been well illustrated for the neotropical tree Dicymbe corymbosa whose monodominance relies on: (1) ectomycorrhizal symbiosis (Henkel et al. 2002) linked to (2) mast fruiting (Henkel et al. 2005), (3) high seedling survival rate (Henkel et al. 2005, McGuire 2007a, 2007b) and, potentially, (4) slow litter decomposition (Mayor & Henkel 2006, McGuire et al. 2010), moreover, (5) the reiterative habit of D. corymbosa slows the gap dynamics, and reduces species richness (Woolley et al. 2008). Thus, a comprehensive understanding of monodominance may only emerge from the comparison of many case studies to point out shared mechanisms. Here, we report a new case of a monodominant species: Spirotropis longifolia (DC.) Baill.

A novel explanation of the origin of cereal agriculture is proposed, based on the ecology and adaptive morphology of wild cereals ancestral to our founder cereals (einkorn, emmer and barley). Wild cereals are unusually large-seeded. A natural evolutionary-ecological syndrome relates l arge seed, a wns and m onodominance (LAM). Awns bury attached seeds in the soil, protecting seed from fire; buried seed needs to be large to emerge on germination; large seeds, growing without competition from small-seeded plants, will produce monodominant vegetation. Climatic and edaphic instability at the Pleistocene–Holocene boundary would have provided an impetus for the spread of annual ruderal grasses. LAM grassland provided an obvious natural model for the origins of cereal agriculture. Subsequent field management would mimic the natural niche (MNN). The fact that monodominance is a long-standing character of the natural LAM syndrome validates cereal monocultures (now producing most of our food). An alternative explanation of crop domestication, by auditioning a great range of species for a human-constructed niche (NCT), is rejected.

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.

A-09-20; International audience; Tropical rain forests generally have a complex structure and a high diversity of species in their canopy, but in some rain forests the upper canopy is dominated by a single species. The factors controlling this dominance are uncertain. In New Caledonia, Nothofagus species dominate the upper canopy of some rain forests on ultramafic soils. Here we investigate whether leaf-level nutrient-use efficiency (NUE) could explain dominance by Nothofagus. We found no evidence of a competitive advantage in Nothofagus in terms of leaf-level NUE: Nothofagus species did not have lower leaf macronutrient concentrations, nor did they resorb more nutrients than co-occurring species on average. They did, however, have lower foliar Ni concentrations on average. Leaf decay rate across all species in a glasshouse-based trial correlated positively with foliar P and negatively with cell wall content, lignin:P, C:P, lignin:N, leaf toughness and tannin activity. Multivariate analysis suggested that total cell wall concentration exerted the strongest independent effect on variation among species in decomposition rate. Slow decomposition of Nothofagus leaf litter may facilitate continued dominance of the upper canopy by suppressing establishment and growth of co-occurring species or by promoting disturbance through fire, since disturbance has been suggested as necessary for regeneration and maintenance of dominance by Nothofagus species. However, the biological mechanisms allowing Nothofagus to achieve initial dominance of these post-disturbance forests are uncertain, and may still include plant-level NUE.