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We present a meta-analysis of plant responses to fertilization experiments conducted in lowland, species-rich, tropical forests. We also update a key result and present the first species-level analyses of tree growth rates for a 15-yr factorial nitrogen (N), phosphorus (P), and potassium (K) experiment conducted in central Panama. The update concerns community-level tree growth rates, which responded significantly to the addition of N and K together after 10 yr of fertilization but not after 15 yr. Our experimental soils are infertile for the region, and species whose regional distributions are strongly associated with low soil P availability dominate the local tree flora. Under these circumstances, we expect muted responses to fertilization, and we predicted species associated with low-P soils would respond most slowly. The data did not support this prediction, species-level tree growth responses to P addition were unrelated to species-level soil P associations. The meta-analysis demonstrated that nutrient limitation is widespread in lowland tropical forests and evaluated two directional hypotheses concerning plant responses to N addition and to P addition. The meta-analysis supported the hypothesis that tree (or biomass) growth rate responses to fertilization are weaker in old growth forests and stronger in secondary forests, where rapid biomass accumulation provides a nutrient sink. The meta-analysis found no support for the long-standing hypothesis that plant responses are stronger for P addition and weaker for N addition. We do not advocate discarding the latter hypothesis. There are only 14 fertilization experiments from lowland, species-rich, tropical forests, 13 of the 14 experiments added nutrients for five or fewer years, and responses vary widely among experiments. Potential fertilization responses should be muted when the species present are well adapted to nutrient-poor soils, as is the case in our experiment, and when pest pressure increases with fertilization, as it does in our experiment. The statistical power and especially the duration of fertilization experiments conducted in old growth, tropical forests might be insufficient to detect the slow, modest growth responses that are to be expected.

Forest soils typically harbour a vast diversity of fungi, but are usually dominated by filamentous (hyphae‐forming) taxa. Compared to temperate and boreal forests, though, we have limited knowledge about the fungal diversity in tropical rainforest soils. Here we show, by environmental metabarcoding of soil samples collected in three Neotropical rainforests, that Yeasts dominate the fungal communities in terms of the number of sequencing reads and OTUs. These unicellular forms are commonly found in aquatic environments, and their hyperdiversity may be the result of frequent inundation combined with numerous aquatic microenvironments in these rainforests. Other fungi that are frequent in aquatic environments, such as the abundant Chytridiomycotina, were also detected. While there was low similarity in OTU composition within and between the three rainforests, the fungal communities in Central America were more similar to each other than the communities in South America, reflecting a general biogeographic pattern also seen in animals, plants and protists.

Effective societal responses to rapid climate change in the Arctic rely on an accurate representation of region-specific ecosystem properties and processes. However, this is limited by the scarcity and patchy distribution of field measurements. Here, we use a comprehensive, geo-referenced database of primary field measurements in 1,840 published studies across the Arctic to identify statistically significant spatial biases in field sampling and study citation across this globally important region. We find that 31% of all study citations are derived from sites located within 50 km of just two research sites: Toolik Lake in the USA and Abisko in Sweden. Furthermore, relatively colder, more rapidly warming and sparsely vegetated sites are under-sampled and under-recognized in terms of citations, particularly among microbiology-related studies. The poorly sampled and cited areas, mainly in the Canadian high-Arctic archipelago and the Arctic coastline of Russia, constitute a large fraction of the Arctic ice-free land area. Our results suggest that the current pattern of sampling and citation may bias the scientific consensuses that underpin attempts to accurately predict and effectively mitigate climate change in the region. Further work is required to increase both the quality and quantity of sampling, and incorporate existing literature from poorly cited areas to generate a more representative picture of Arctic climate change and its environmental impacts.

There is much interest in understanding ecosystem responses to local-scale soil fertility variation, which has often been studied using retrogressive chronosequences that span thousands of years an ...

Many northern forests are limited by nitrogen (N) availability, slight changes in which can have profound effects on ecosystem function and the activity of ectomycorrhizal (EcM) fungi. Increasing N and phosphorus (P) availability, an analog to accelerated soil organic matter decomposition in a warming climate, could decrease plant dependency on EcM fungi and increase plant productivity as a result of greater carbon use efficiency. However, the impact of altered N and P availability on the growth and activity of EcM fungi in boreal forests remains poorly understood despite recognition of their importance to host plant nutrition and soil carbon sequestration. To address such uncertainty we examined above and belowground ecosystem properties in a boreal black spruce forest following five years of factorial N and P additions. By combining detailed soil, fungal, and plant δ15N measurements with in situ metrics of fungal biomass, growth, and activity, we found both expected and unexpected patterns. Soil nitrate isotope values became 15N enriched in response to both N and P additions; fungal biomass was repressed by N yet both biomass and growth were stimulated by P; and, black spruce dependency on EcM derived N increased slightly when N and P were added alone yet significantly declined when added in combination. These findings contradict predictions that N fertilization would increase plant P demands and P fertilization would further exacerbate plant N demands. As a result, the prediction that EcM fungi predictably respond to plant N limitation was not supported. These findings highlight P as an under appreciated mediator of the activity of denitrifying bacteria, EcM fungi, and the dynamics of N cycles in boreal forests. Further, use of δ15N values from bulk soils, plants, and fungi to understand how EcM systems respond to changing nutrient availabilities will often require additional ecological information.

Forest soils typically harbour a vast diversity of fungi, but are usually dominated by filamentous (hyphae-forming) taxa. Compared to temperate and boreal forests, though, we have limited knowledge about the fungal diversity in tropical rainforest soils. Here we show, by environmental metabarcoding of soil samples collected in three Neotropical rainforests, that Yeasts dominate the fungal communities in terms of the number of sequencing reads and OTUs. These unicellular forms are commonly found in aquatic environments, and their hyperdiversity may be the result of frequent inundation combined with numerous aquatic microenvironments in these rainforests. Other fungi that are frequent in aquatic environments, such as the abundant Chytridiomycotina, were also detected. While there was low similarity in OTU composition within and between the three rainforests, the fungal communities in Central America were more similar to each other than the communities in South America, reflecting a general biogeographic pattern also seen in animals, plants, and protists.Contactdunthorn@rhrk.uni-kl.de

International audience; Temperature is a primary driver of the distribution of biodiversity as well as of ecosystem boundaries. Declining temperature with increasing elevation in montane systems has long been recognized as a major factor shaping plant community biodiversity, metabolic processes, and ecosystem dynamics. Elevational gradients, as thermoclines, also enable prediction of long-term ecological responses to climate warming. One of the most striking manifestations of increasing elevation is the abrupt transitions from forest to treeless alpine tundra However, whether there are globally consistent above-and belowground responses to these transitions remains an open question. To disentangle the direct and indirect effects of temperature on ecosystem properties, here we evaluate replicate treeline ecotones in seven temperate regions of the world. We find that declining temperatures with increasing elevation did not affect tree leaf nutrient concentrations, but did reduce ground-layer community-weighted plant nitrogen, leading to the strong stoichiometric convergence of ground-layer plant community nitrogen to phosphorus ratios across all regions. Further, elevation-driven changes in plant nutrients were associated with changes in soil organic matter content and quality (carbon to nitrogen ratios) and microbial properties. Combined, our identification of direct and indirect temperature controls over plant communities and soil properties in seven contrasting regions suggests that future warming may disrupt the functional properties of montane ecosystems, particularly where plant community reorganization outpaces treeline advance.

Foliar nitrogen (N) isotope ratios (δ15N) are used as a proxy for N-cycling processes, including the “openness” of the N cycle and the use of distinct N sources, but there is little experimental support for such proxies in lowland tropical forest. To address this, we examined the δ15N values of soluble soil N and canopy foliage of four tree species after 13 years of factorial N and P addition to a mature lowland rainforest. We hypothesized that N addition would lead to 15N-enriched soil N forms due to fractionating losses, whereas P addition would reduce N losses as the plants and microbes adjusted their stoichiometric demands. Chronic N addition increased the concentration and δ15N value of soil nitrate and δ15N in live and senesced leaves in two of four tree species, but did not affect ammonium or dissolved organic N. Phosphorus addition significantly increased foliar δ15N in one tree species and elicited significant N × P interactions in two others due to a reduction in foliar δ15N enrichment under N and P co-addition. Isotope mixing models indicated that three of four tree species increased their use of nitrate relative to ammonium following N addition, supporting the expectation that tropical trees use the most available form of mineral N. Previous observations that anthropogenic N deposition in this tropical region have led to increasing foliar δ15N values over decadal time-scales is now mechanistically linked to greater usage of 15N-enriched nitrate.

Summary The concentration, stoichiometry and resorption of nitrogen (N) and phosphorus (P) in plant leaves are often used as proxies of the availability of these growth-limiting nutrients, but the responses of these metrics to changes in nutrient availability remain largely untested for tropical forest trees. We evaluated changes in N and P concentrations, N/P ratios and resorption for four common tree species after 13 years of factorial N and P additions in a lowland tropical forest in Panama. Chronic P addition increased foliar P concentrations, decreased P resorption proficiency and decreased N/P ratios in three locally common eudicot tree species (Alseis blackiana, Heisteria concinna, Tetragastris panamensis). The increase in foliar P involved similar proportional increases in organic and inorganic P in two species and a disproportionately large increase in inorganic P in A. blackiana. Nitrogen addition did not alter foliar N concentrations in any species, but did decrease N resorption proficiency in H. concinna. A fourth species, the palm Oenocarpus mapora, demonstrated remarkably static foliar nutrient concentrations, responding only with a marginal decrease in P resorption proficiency under N plus P co-addition. Synthesis. Collectively, these results suggest that adjustment of N/P ratios can be expected in eudicots exposed to elevated P, but foliar N appears to already be at optimal levels in these lowland rain forest tree species. The complexity of species-specific responses to altered nutrient availability highlights the difficulty in predicting future responses of tropical forest trees to a changing world.

The Clavariaceae is a diverse family of mushroom-forming fungi composed of species that produce simple clubs, coralloid, lamellate-stipitate, hydnoid and resupinate sporocarps. Here we present a systematic and ecological overview of the Clavariaceae based on phylogenetic analysis of sequences of the nuclear large subunit ribosomal RNA (nLSU), including nine from type collections. Forty-seven sequences from sporocarps of diverse taxa across the Clavariaceae were merged with 243 environmental sequences from GenBank and analyzed phylogenetically to determine major clades within the family. Four major clades or lineages were recovered: (i) Mucronella, (ii) Ramariopsis-Clavulinopsis, (iii) Hyphodontiella and (iv) Clavaria-Camarophyllopsis-Clavicorona. Clavaria is paraphyletic, within which the lamellate and pileate-stipitate genus Camarophyllopsis is derived and composed of two independent lineages. The monotypic genus Clavicorona also appears nested within Clavaria. The monophyly of Clavaria and Camarophyllopsis, however, cannot be statistically rejected. We compared differing classification schemes for the genera Ramariopsis and Clavulinopsis, most of which are inconsistent with the molecular phylogeny and are statistically rejected. Scytinopogon, a genus classified in the Clavariaceae by several authors, shares phylogenetic affinities with the Trechisporales. Overall 126 molecular operational taxonomic units can be recognized in the Clavariaceae, roughly half of which are known only from environmental sequences, an estimate that exceeds the known number of species in the family. Stable isotope ratios of carbon and nitrogen were measured from specimens representing most major phylogenetic lineages to predict trophic strategies. These results suggest that most non-lignicolous species feature a biotrophic mode of nutrition. Ancestral state reconstruction analysis highlights the taxonomic significance of at least nine morphological traits at various depths in the family tree.

Nitrogen (N) availability influences the productivity and distribution of plants in tropical montane forests. Strategies to acquire soil N, such as direct uptake of organic compounds or associations with root symbionts to enhance N acquisition in exchange for carbon (C), may facilitate plant species coexistence and ecosystem N retention. Alternatively, rapid microbial turnover of soil N forms in tropical soils might promote flexible plant N-uptake strategies and mediate species coexistence. We tested whether sympatric plant species with different root symbiont associations, and therefore potentially different nutrient acquisition strategies, partition chemical forms of N or show plasticity in N uptake in a tropical pre-montane forest in Panama. We traced the movement of three 15 N forms into soil pools, microbes, and seedlings of eleven species differing in root traits. Seedlings were grown in a split-plot field transplant experiment, with plots receiving equimolar mixtures of ammonium, nitrate, and glycine, with one form isotopically labeled in each block. After 48 h, more 15 N was recovered in microbes than in plants, while all pools (extractable organic and inorganic N, microbial biomass, and leaves) contained greater amounts of 15 N from nitrate than from ammonium or glycine. Furthermore, 13 C from dual-labeled glycine was not recovered in the leaves of any seedling, suggesting the studied species do not directly take up organic N or transform organic N prior to translocation to leaves. Nitrogen uptake differed by root symbiont group only for nitrate, with greater 15 N recovery in plants with arbuscular mycorrhizal (AM) associations or proteoid roots compared to orchids. Some root trait groups differed in 15 N recovery among N forms, with greater nitrate uptake than ammonium or glycine by AM-associated and N2 -fixing plants. However, only five of eleven species showed differences in uptake among N forms. These results indicate flexibility in uptake of N forms in tropical plants across root trait groups, with only a few species displaying weak preferences for a specific N form.

High animal and plant richness in tropical rainforest communities has long intrigued naturalists. It is unknown if similar hyperdiversity patterns are reflected at the microbial scale with unicellular eukaryotes (protists). Here we show, using environmental metabarcoding of soil samples and a phylogeny-aware cleaning step, that protist communities in Neotropical rainforests are hyperdiverse and dominated by the parasitic Apicomplexa, which infect arthropods and other animals. These host-specific parasites potentially contribute to the high animal diversity in the forests by reducing population growth in a density-dependent manner. By contrast, too few operational taxonomic units (OTUs) of Oomycota were found to broadly drive high tropical tree diversity in a host-specific manner under the Janzen-Connell model. Extremely high OTU diversity and high heterogeneity between samples within the same forests suggest that protists, not arthropods, are the most diverse eukaryotes in tropical rainforests. Our data show that protists play a large role in tropical terrestrial ecosystems long viewed as being dominated by macroorganisms.

Animal and plant richness in tropical rainforests has long intrigued naturalist. More recent work has revealed that parasites contribute to high tropical tree diversity (Bagchi et al., 2014; Terborgh, 2012) and that arthropods are the most diverse eukaryotes in these forests (Erwin, 1982; Basset et al., 2012). It is unknown if similar patterns are reflected at the microbial scale with unicellular eukaryotes or protists. Here we show, using environmental metabarcoding and a novel phylogeny-aware cleaning step, that protists inhabiting Neotropical rainforest soils are hyperdiverse and dominated by the parasitic Apicomplexa, which infect arthropods and other animals. These host-specific protist parasites potentially contribute to the high animal diversity in the forests by reducing population growth in a density-dependent manner. By contrast, we found too few Oomycota to broadly drive high tropical tree diversity in a host-specific manner under the Janzen-Connell model (Janzen, 1970; Connell, 1970). Extremely high OTU diversity and high heterogeneity between samples within the same forests suggest that protists, not arthropods, are the most diverse eukaryotes in tropical rainforests. Our data show that microbes play a large role in tropical terrestrial ecosystems long viewed as being dominated by macro-organisms.Contact: dunthorn@rhrk.uni-kl.de

Global patterns in soil, plant, and fungal stable isotopes of N (δ15N) show promise as integrated metrics of N cycling, particularly the activity of ectomycorrhizal (ECM) fungi. At small spatial scales, however, it remains difficult to differentiate the underlying causes of plant δ15N variability and this limits the application of such measurements to better understand N cycling. We conducted a landscape-scale analysis of δ15N values from 31 putatively N-limited monospecific black spruce (Picea mariana) stands in central Alaska to assess the two main hypothesized sources of plant δ15N variation: differing sources and ECM fractionation. We found roughly 20% of the variability in black spruce foliar N and δ15N values to be correlated with the concentration and δ15N values of soil NH4 + and dissolved organic N (DON) pools, respectively. However, 15N-based mixing models from 24 of the stands suggested that fractionation by ECM fungi obscures the 15N signature of soil N pools. Models, regressions, and N abundance data all suggested that increasing dependence on soil DON to meet black spruce growth demands predicates increasing reliance on ECM-derived N and that black spruce, on average, received 53% of its N from ECM fungi. Future research should partition the δ15N values within the soil DON pool to determine how choice of soil δ15N values influence modeled ECM activity. The C balance of boreal forests is tightly linked to N cycling and δ15N values may be useful metrics of changes to these connections.

Mycorrhizal and saprotrophic (SAP) fungi are essential to terrestrial element cycling due to their uptake of mineral nutrients and decomposition of detritus. Linking these ecological roles to specific fungi is necessary to improve our understanding of global nutrient cycling, fungal ecophysiology, and forest ecology. Using discriminant analyses of nitrogen (delta(15)N) and carbon (delta(13)C) isotope values from 813 fungi across 23 sites, we verified collector-based categorizations as either ectomycorrhizal (ECM) or SAP in > 91% of the fungi, and provided probabilistic assignments for an additional 27 fungi of unknown ecological role. As sites ranged from boreal tundra to tropical rainforest, we were able to show that fungal delta(13)C (26 sites) and delta(15)N (32 sites) values could be predicted by climate or latitude as previously shown in plant and soil analyses. Fungal delta(13)C values are likely reflecting differences in C-source between ECM and SAP fungi, whereas (15)N enrichment of ECM fungi relative to SAP fungi suggests that ECM fungi are consistently delivering (15)N depleted N to host trees across a range of ecosystem types.

Quantifying global patterns of terrestrial nitrogen (N) cycling is central to predicting future patterns of primary productivity, carbon sequestration, nutrient fluxes to aquatic systems, and climate forcing. With limited direct measures of soil N cycling at the global scale, syntheses of the 15N:14N ratio of soil organic matter across climate gradients provide key insights into understanding global patterns of N cycling. In synthesizing data from over 6000 soil samples, we show strong global relationships among soil N isotopes, mean annual temperature (MAT), mean annual precipitation (MAP), and the concentrations of organic carbon and clay in soil. In both hot ecosystems and dry ecosystems, soil organic matter was more enriched in 15N than in corresponding cold ecosystems or wet ecosystems. Below a MAT of 9.8°C, soil δ15N was invariant with MAT. At the global scale, soil organic C concentrations also declined with increasing MAT and decreasing MAP. After standardizing for variation among mineral soils in soil C and clay concentrations, soil δ15N showed no consistent trends across global climate and latitudinal gradients. Our analyses could place new constraints on interpretations of patterns of ecosystem N cycling and global budgets of gaseous N loss. Fil: Craine, Joseph M. Kansas State University. Division of Biology; Estados Unidos Fil: Elmore, Andrew J. University of Maryland Center for Environmental Science. Appalachian Laboratory; Estados Unidos Fil: Wang, Lixing. Indiana University-Purdue University Department of Earth Sciences; Estados Unidos Fil: Augusto, Laurent. INRA. Bordeaux Sciences Agro; Francia Fil: Baisden, Troy. GNS Science. National Isotope Centre; Nueva Zelanda Fil: Brookshire, E.N.J. Montana State University. Department of Land Resources and Environmental Sciences; Estados Unidos Fil: Cramer, Michael D. University of Cape Town. Department of Biological Sciences; Sudáfrica Fil: Hasselquist, Niles. Swedish University of Agricultural Sciences. Forest Ecology and Management; Suecia Fil: Hobbie, Erik A. University of New Hampshire. Earth Systems Research Center; Estados Unidos Fil: Kahmen, Ansgar. Departement of Environmental Sciences - Botany; Suiza Fil: Kaba, Keisuke. Tokyo University of Agriculture and Technology. Institute of Agriculture; Japón Fil: Kranabetter, M. British Columbia (Canadá). Ministry of Forests, Lands and Natural Resource Operations; Canadá Fil: Mack, M. University of Florida. Department of Biology; Estados Unidos Fil: Marin-Spiotta, E. University of Wisconsin. Department of Geography; Estados Unidos Fil: Mayor, J.R. Swedish University of Agricultural Sciences. Department of Forest Ecology & Management; Suecia Fil: McLauchlan, K.K. Kansas State University. Department of Geography; Estados Unidos Fil: Michelsen, A. University of Copenhagen. Department of Biology; Dinamarca Fil: Nardoto, G.B. Universidade de Brasília. Faculdade UnB Planaltina; Brasil Fil: Oliveira, R.S. Universidade Estadual de Campinas. Instituto de Biologia. Departamento de Biologia Vegetal; Brasil Fil: Perakis, S.S. Forest and Rangeland Ecosystem Science Center; Estados Unidos Fil: Peri, Pablo Luis. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Santa Cruz; Argentina. Universidad Nacional de la Patagonia Austral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Quesada, C. Instituto Nacional de Pesquisas da Amazonia. Coordenação de Dinâmica Ambiental; Brasil Fil: Richter, A. University of Vienna. Department of Terrestrial Ecosystem Research; Austria Fil: Schipper, L.A. University of Waikato. Environmental Research Institute; Nueva Zelanda Fil: Stevenson, B.A. Landcare Research; Nueva Zelanda Fil: Turner, B.L. Smithsonian Tropical Research Institute; Panamá Fil: Viani, R.A.G. Universidade Federal de São Carlos. Centro de Ciências Agrárias; Brasil Fil: Wanek, W. University of Vienna. Department of Terrestrial Ecosystem Research; Austria Fil: Zeller, B. INRA Nancy. Biogéochimie des Ecosystèmes Forestiers; Francia

Ectomycorrhizal (EcM)-mediated nitrogen (N) acquisition is one main strategy used by terrestrial plants to facilitate growth. Measurements of natural abundance nitrogen isotope ratios (denoted as δ(15) N relative to a standard) increasingly serve as integrative proxies for mycorrhiza-mediated N acquisition due to biological fractionation processes that alter (15) N:(14) N ratios. Current understanding of these processes is based on studies from high-latitude ecosystems where plant productivity is largely limited by N availability. Much less is known about the cause and utility of ecosystem δ(15) N patterns in the tropics. Using structural equation models, model selection and isotope mass balance we assessed relationships among co-occurring soil, mycorrhizal plants and fungal N pools measured from 40 high- and 9 low-latitude ecosystems. At low latitudes (15) N-enrichment caused ecosystem components to significantly deviate from those in higher latitudes. Collectively, δ(15) N patterns suggested reduced N-dependency and unique sources of EcM (15) N-enrichment under conditions of high N availability typical of the tropics. Understanding the role of mycorrhizae in global N cycles will require reevaluation of high-latitude perspectives on fractionation sources that structure ecosystem δ(15) N patterns, as well as better integration of EcM function with biogeochemical theories pertaining to climate-nutrient cycling relationships.

High-throughput sequencing platforms are continuing to increase resulting read lengths, which is allowing for a deeper and more accurate depiction of environmental microbial diversity. With the nascent Reagent Kit v3, Illumina MiSeq now has the ability to sequence the eukaryotic hyper-variable V4 region of the SSU-rDNA locus with paired-end reads. Using DNA collected from soils with analyses of strictly- and nearly identical amplicons, here we ask how the new Illumina MiSeq data compares with what we can obtain with Roche/454 GS FLX with regard to quantity and quality, presence and absence, and abundance perspectives. We show that there is an easy qualitative transition from the Roche/454 to the Illumina MiSeq platforms. The ease of this transition is more nuanced quantitatively for low-abundant amplicons, although estimates of abundances are known to also vary within platforms.

Boletellus exiguus sp. nov. and Boletellus dicymbophilus sp. nov. (Boletaceae, Boletales, Basidiomycota) are described as new to science. These boletes were collected from tropical forests dominated by ectomycorrhizal Dicymbe corymbosa (Caesalpiniaceae) in the Pakaraima Mountains of western Guyana.

This work tested the hypothesis that ectomycorrhizas (EM) of Dicymbe corymbosa alter leaf-litter decomposition and residual litter quality in tropical forests of Guyana. Mass loss of leaf litter in litter bags was determined on three occasions, in two experiments, during a 12-month period. Paired root-exclusion plots were located randomly within a D. corymbosa forest. Both D. corymbosa and mixed-species leaf litters were reciprocally transplanted into their respective forest types. Elemental analysis was performed on the residual D. corymbosa leaf litter after 1 yr. Leaf litter mass loss in the D. corymbosa forest was not influenced by EM, despite high EM colonization. Elemental analysis of D. corymbosa leaf litter residues demonstrated reduced calcium levels in the presence of EM, which were negatively correlated with EM rootlet-colonizing mass. The lack of EM effect on the litter decomposition rate, coupled with high EM colonization, suggests an important but indirect role in mineral nutrient acquisition. Lowered Ca concentration in leaf litter exposed to EM may suggest a high Ca demand by the ectotroph system.

Summary • In Guyana, we investigated seed output, and resulting seedling establishment and survival, during a ‘mast’ year, by the ectomycorrhizal, monodominant rainforest canopy tree Dicymbe corymbosa (Caesalpiniaceae), a species with high, synchronous seed production at intermittent years. • By utilizing seed traps, the mast seed output, predation, carbon and mineral investment, and masting synchrony were quantified in 2003 in primary D. corymbosa forests. Establishment of seedling cohorts was monitored, and climatic conditions associated with masting were assessed. • During 2003, D. corymbosa in the Pakaraima Mountains exhibited high, synchronous seed production with low dispersal and predation. Investment in reproductive biomass was large relative to that in other tropical forests. Recent D. corymbosa reproductive events followed El Nino-induced droughts, with little intervening seed production. Over 12 months, 40% of the 2003 seedling cohort survived. • Our results suggest that D. corymbosa has a strongly bimodal fruiting pattern that allows the establishment of a large seedling bank, facilitating persistent monodominance. Resource investment in large seed crops may depend on mineral recycling via ectomycorrhizas, coupled with the reallocation of carbon from vegetative maintenance.

Fungi play integral roles in soil nutrient cycling, but the determinants of fungal diversity and biogeographic patterns of key functional groups remain poorly understood. By using pyrosequencing data from hundreds of globally distributed soil samples, we demonstrated fungal diversity that expands upon the taxonomic and molecular diversity recorded so far. Except for ectomycorrhizal symbionts, fungal functional group richness was unrelated to plant diversity and plant-to-fungus richness ratio declined exponentially towards the poles. Climatic factors, followed by edaphic and spatial variables, constituted the best predictors of fungal richness and community composition at the global scale. Fungi follow general biogeographic patterns and latitudinal diversity gradients with several exceptions. Fil: Tedersoo, Leho. University Of Tartu.; Estonia Fil: Bahram, Mohammad. University Of Tartu.; Estonia Fil: Põlme, Sergei. University Of Tartu.; Estonia Fil: Kõljalg, Urmas. University Of Tartu.; Estonia Fil: Yorou, Nourou. Université de Parakou. Faculté d′Agronomie; Benín Fil: Nouhra, Eduardo Ramon. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Greslebin, Alina Gabriela. Universidad Nacional de la Patagonia; Argentina Fil: Kohout, Petr. University Of Tartu.; Estonia Fil: Hosaka, Kentaro. National Museum of Nature and Science. Department of Botany; Japón Fil: Hiiesalu, Indrek. University Of Tartu.; Estonia Fil: Henkel, Terry W.. Humboldt State University. Department of Biological Sciences; Estados Unidos Fil: Harend, Helery. University Of Tartu.; Estonia Fil: Guo, Liang-dong. Chinese Academy of Sciences. Institute of Microbiology. State Key Laboratory of Mycology; China Fil: Geml, József. Fil: Grelet, Gwen. Landcare Research. Ecosystems and Global Change Team; Nueva Zelanda Fil: Gates, Genevieve. Tasmanian Institute of Agriculture; Australia Fil: Dunstan, William. Murdoch University. School of Veterinary and Life Sciences; Australia Fil: Dunk, Chris. Swedish University of Agricultural Sciences. Department of Forest Ecology and Management; Suecia Fil: Drenkhan, Rein. Estonian University of Life Sciences. Institute of Forestry and Rural Engineering; Estonia Fil: Dearnaley, John. University of Southern Queensland. Faculty of Health, Engineering and Sciences; Australia Fil: De Kesel, André. Botanic Garden Meise; Bélgica Fil: Dang,Tan. Vietnamese Academy of Forest Sciences; Vietnam Fil: Chen, Xin. Zhejiag University. College of Life Sciences; China Fil: Buegger, Franz. Helmholtz Zentrum München. Institute of Soil Ecology; Alemania Fil: Brearley, Francis Q.. Manchester Metropolitan University. School of Science and the Environment; Reino Unido Fil: Bonito, Gregory. Royal Botanic Gardens Melbourne; Australia Fil: Anslan, Sten. University Of Tartu.; Estonia Fil: Abell, Sandra. James Cook University. School of Marine and Tropical Biology; Australia Fil: Abarenkov, Kessy. University Of Tartu.; Estonia