Search

Plant–soil biodiversity interactions are fundamental for the functioning of terrestrial ecosystems. Yet, the existence of a set of globally distributed topsoil microbial and small invertebrate organisms consistently associated with land plants (i.e., their consistent soil-borne microbiome), together with the environmental preferences and functional capabilities of these organisms, remains unknown. We conducted a standardized field survey under 150 species of land plants, including 58 species of bryophytes and 92 of vascular plants, across 124 locations from all continents. We found that, despite the immense biodiversity of soil organisms, the land plants evaluated only shared a small fraction (less than 1%) of all microbial and invertebrate taxa that were present across contrasting climatic and soil conditions and vegetation types. These consistent taxa were dominated by generalist decomposers and phagotrophs and their presence was positively correlated with the abundance of functional genes linked to mineralization. Finally, we showed that crossing environmental thresholds in aridity (aridity index of 0.65, i.e., the transition from mesic to dry ecosystems), soil pH (5.5; i.e., the transition from acidic to strongly acidic soils), and carbon (less than 2%, the lower limit of fertile soils) can result in drastic disruptions in the associations between land plants and soil organisms, with potential implications for the delivery of soil ecosystem processes under ongoing global environmental change.

Plant–soil biodiversity interactions are fundamental for the functioning of terrestrial ecosystems. Yet, the existence of a set of globally distributed topsoil microbial and small invertebrate organisms consistently associated with land plants (i.e., their consistent soil-borne microbiome), together with the environmental preferences and functional capabilities of these organisms, remains unknown. We conducted a standardized field survey under 150 species of land plants, including 58 species of bryophytes and 92 of vascular plants, across 124 locations from all continents. We found that, despite the immense biodiversity of soil organisms, the land plants evaluated only shared a small fraction (less than 1%) of all microbial and invertebrate taxa that were present across contrasting climatic and soil conditions and vegetation types. These consistent taxa were dominated by generalist decomposers and phagotrophs and their presence was positively correlated with the abundance of functional genes linked to mineralization. Finally, we showed that crossing environmental thresholds in aridity (aridity index of 0.65, i.e., the transition from mesic to dry ecosystems), soil pH (5.5; i.e., the transition from acidic to strongly acidic soils), and carbon (less than 2%, the lower limit of fertile soils) can result in drastic disruptions in the associations between land plants and soil organisms, with potential implications for the delivery of soil ecosystem processes under ongoing global environmental change.

Acknowledgments We would like to thank C. Walsh and R. Ochoa-Hueso for advice on bioinformatics and statistical analyses. We also thank M. Martin for revising the English of the manuscript. In addition, we thank J. Owojori for connecting us with our sampling collaborator in Nigeria, A. R. Bamigboye. Funding: M.D.-B. and this project were supported by a 2019 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation (URBANFUN) and by the BES grant agreement no. LRB17\1019 (MUSGONET). M.D.-B. is also supported by a Ramón y Cajal grant from the Spanish Ministry of Science and Innovation (RYC2018-025483-I). N.F. was supported by grants from the U.S. National Science Foundation (DEB1556090 and DEB1542653). L.T. acknowledges support from Norway-Baltic collaboration grant EMP442 and Estonian Science Foundation grant PRG632. B.K.S. acknowledges a research award by the Humboldt Foundation and funding from the Australian Research Council (DP190103714). F.A. is supported by ANID FONDECYT 11180538 and 1170995. S.A. is funded by ANID FONDECYT 1170995 and ANID ANILLO ACT192027. F.B. and J.L.M. acknowledge support from the Spanish Ministry and FEDER funds for the project AGL2017-85755-R, the i-LINK+ 2018 (LINKA20069) from CSIC, as well as funds from “Fundación Séneca” from Murcia Province (19896/GERM/15). C.P. acknowledges support from the Spanish State Plan for Scientific and Technical Research and Innovation (2013–2016), award reference AGL201675762-R (AEI/FEDER, UE). M.B. acknowledges support from a Juan de la Cierva Formación grant from the Spanish Ministry of Economy and Competitiveness (FJCI-2018-036520-I). T.P.M. would like to acknowledge contributions from the National Research Foundation of South Africa and cities involved in the South African survey. Slovenian coauthors were supported by the research project J4-1766 “Methodology approaches in genome-based diversity and ecological plasticity study of truffles from their natural distribution areas” and the Resea, The structure and function of the soil microbiome of urban greenspaces remain largely undetermined. We conducted a global field survey in urban greenspaces and neighboring natural ecosystems across 56 cities from six continents, and found that urban soils are important hotspots for soil bacterial, protist and functional gene diversity, but support highly homogenized microbial communities worldwide. Urban greenspaces had a greater proportion of fast-growing bacteria, algae, amoebae, and fungal pathogens, but a lower proportion of ectomycorrhizal fungi than natural ecosystems. These urban ecosystems also showed higher proportions of genes associated with human pathogens, greenhouse gas emissions, faster nutrient cycling, and more intense abiotic stress than natural environments. City affluence, management practices, and climate were fundamental drivers of urban soil communities. Our work paves the way toward a more comprehensive global-scale perspective on urban greenspaces, which is integral to managing the health of these ecosystems and the well-being of human populations., Depto. de Biodiversidad, Ecología y Evolución, Fac. de Ciencias Biológicas, TRUE, pub

The sensitivity of soil microbial respiration to warming (Q10) remains a major source of uncertainty surrounding the projections of soil carbon emissions to the atmosphere as the factors driving Q10 patterns across ecosystems have been assessed in isolation from each other. Here we report the results of a warming experiment using soils from 332 sites across all continents and major biomes to simultaneously evaluate the main drivers of global Q10 patterns. Compared with biochemical recalcitrance, mineral protection, substrate quantity and environmental factors, the soil microbiome (that is, microbial biomass and bacterial taxa) explained the largest portion of variation in Q10 values. Our work provides solid evidence that soil microbiomes largely govern the responses of soil heterotrophic respiration to warming and thus need to be explicitly accounted for when assessing land carbon–climate feedbacks.

Phosphorus (P) limitation in the coming decades calls for the utilization of alternative fertilizers in agriculture. Struvite is a promising P source, but its potential fertilizer role is dependent on different physical, chemical and biological properties, which are very heterogeneous in soil and complicate the prediction of the best soil conditions for its application. Here, we evaluated the solubility of struvite in soil, its redistribution into P fractions, and its potential abiotic and biotic drivers in 62 globally-distributed soils with contrasting properties through an incubation assay. We found that after 40 days, about 35% of the struvite-P is redistributed into soil fractions that are more accessible to plants and microbes. P redistribution from struvite is driven by a complex suite of chemical, physical, environmental and microbial properties that varied across soils. Soil texture played a critical role in determining the entrapping of P in struvite-amended soils in soluble (H2O), labile (NaHCO3), and moderately labile (NaOH) fractions. In addition, the soil cations solution was one the most important driver for struvite-P available fractions. The great importance of texture and cations in determining struvite-P fractions in soil contrasted with the relatively minor role of pH. At the microbial level, the number of bacterial operational taxonomic units (OTUs) from the original soils that correlated with struvite-P fractions was higher than that of fungi. In comparison with the soluble fraction (PH2O), the number of OTUs that correlated with the struvite-P labile fraction (PNaHCO3) was dominated by bacteria rather than by fungi. Overall, this study provided a predictive framework of the potential use of struvite as a P fertilizer in contrasting soils.

Photoautotrophic soil cyanobacteria play essential ecological roles and are known to exhibit large changes in their diversity and abundance throughout early succession. However, much less is known about how and why soil cyanobacterial communities change as soil develops over centuries and millennia, and the effects that vegetation have on such communities. We combined an extensive field survey, including 16 global soil chronosequences across contrasting ecosystems (from deserts to tropical forests), with molecular analyses to investigate how the diversity and abundance of photosynthetic and nonphotosynthetic soil cyanobacteria are affected by vegetation change during soil development, over time periods from hundreds to thousands of years. We show that, in most chronosequences, the abundance, species richness and community composition of soil cyanobacteria are relatively stable as soil develops (from centuries to millennia). Regardless of soil age, forest chronosequences were consistently dominated by nonphotosynthetic cyanobacteria (Vampirovibrionia), while grasslands and shrublands were dominated by photosynthetic cyanobacteria. Chronosequences undergoing drastic vegetation shifts (e.g. transitions from grasslands to forests) experienced significant changes in the composition of soil cyanobacterial communities. Our results advance our understanding of the ecology of cyanobacterial classes, and of the understudied nonphotosynthetic cyanobacteria in particular, and highlight the key role of vegetation as a major driver of their temporal dynamics as soil develops.

The sensitivity of soil microbial respiration to warming (Q10) remains a major source of uncertainty surrounding the projections of soil carbon emissions to the atmosphere as the factors driving Q10 patterns across ecosystems have been assessed in isolation from each other. Here we report the results of a warming experiment using soils from 332 sites across all continents and major biomes to simultaneously evaluate the main drivers of global Q10 patterns. Compared with biochemical recalcitrance, mineral protection, substrate quantity and environmental factors, the soil microbiome (that is, microbial biomass and bacterial taxa) explained the largest portion of variation in Q10 values. Our work provides solid evidence that soil microbiomes largely govern the responses of soil heterotrophic respiration to warming and thus need to be explicitly accounted for when assessing land carbon–climate feedbacks.

Aim Cyanobacteria have shaped the history of life on Earth and continue to play important roles as carbon and nitrogen fixers in terrestrial ecosystems. However, their global distribution and ecological preferences remain poorly understood, particularly for two recently discovered non-photosynthetic cyanobacterial classes (Sericytochromatia and Melainabacteria). Location Two hundred and thirty-seven locations across six continents encompassing multiple climates (arid, temperate, tropical, continental and polar) and vegetation types (forests, grasslands and shrublands). Time period Sampling was carried out between 2003 and 2015. Major taxa studied Photosynthetic and non-photosynthetic cyanobacterial taxa. Methods We conducted a field survey and used co-occurrence network analysis and structural equation modelling to evaluate the distribution and environmental preferences of soil cyanobacteria across the globe. These ecological preferences were used to create a global atlas (predictive distribution maps) of soil cyanobacteria. Results Network analyses identified three major groups of cyanobacterial taxa, which resembled the three main cyanobacterial classes: the photosynthetic Oxyphotobacteria-dominated cluster, which were prevalent in arid and semi-arid areas, and the non-photosynthetic Sericytochromatia- and Melainabacteria-dominated clusters, which preferred hyper-arid oligotrophic and acidic/humid environments, respectively. Main conclusions This study provides new insights into the environmental preferences of non-photosynthetic cyanobacteria in soils globally. Our findings highlight the contrasting environmental preferences among the three clusters of cyanobacteria and suggest that alterations in environmental conditions linked to climate change might result in important changes in the ecology and biogeography of these functionally important microorganisms.

Photoautotrophic soil cyanobacteria play essential ecological roles and are known to experience large changes in their diversity and abundance throughout early succession. However, much less is known about how and why soil cyanobacterial communities change as soil develops from centuries to millennia, and the effects of vegetation on them. We combined an extensive field survey including 16 global soil chronosequences across contrasting ecosystems (from deserts to tropical forests) with molecular analyses to investigate how the diversity and abundance of photosynthetic and non-photosynthetic soil cyanobacteria under vegetation change during soil development from hundreds to thousands of years. We show that, in most chronosequences, the abundance, species richness and community composition of soil cyanobacteria were relatively stable as soil develops (from centuries to millennia). Regardless of soil age, forest chronosequences were consistently dominated by non-photosynthetic cyanobacteria (Vampirovibrionia), while grasslands and shrublands were dominated by photosynthetic cyanobacteria. Chronosequences undergoing drastic vegetation shifts (e.g. transitions from grasslands to forests) experienced significant changes in the composition of soil cyanobacteria communities. Our results advance our understanding of the ecology of cyanobacterial classes, specially the understudied non-photosynthetic ones and highlight the key role of vegetation as a major driver of their temporal dynamics as soil develops.

The structure and function of the soil microbiome of urban greenspaces remain largely undetermined. We conducted a global field survey in urban greenspaces and neighboring natural ecosystems across 56 cities from six continents, and found that urban soils are important hotspots for soil bacterial, protist and functional gene diversity, but support highly homogenized microbial communities worldwide. Urban greenspaces had a greater proportion of fast-growing bacteria, algae, amoebae, and fungal pathogens, but a lower proportion of ectomycorrhizal fungi than natural ecosystems. These urban ecosystems also showed higher proportions of genes associated with human pathogens, greenhouse gas emissions, faster nutrient cycling, and more intense abiotic stress than natural environments. City affluence, management practices, and climate were fundamental drivers of urban soil communities. Our work paves the way toward a more comprehensive global-scale perspective on urban greenspaces, which is integral to managing the health of these ecosystems and the well-being of human populations.

Soil carbon losses to the atmosphere through soil respiration are expected to rise with ongoing temperature increases, but available evidence from mesic biomes suggests that such response disappears after a few years of experimental warming. However, there is lack of empirical basis for these temporal dynamics in soil respiration responses, and for the mechanisms underlying them, in drylands, which collectively form the largest biome on Earth and store 32% of the global soil organic carbon pool. We coupled data from a 10 year warming experiment in a biocrust‐dominated dryland ecosystem with laboratory incubations to confront 0–2 years (short‐term hereafter) versus 8–10 years (longer‐term hereafter) soil respiration responses to warming. Our results showed that increased soil respiration rates with short‐term warming observed in areas with high biocrust cover returned to control levels in the longer‐term. Warming‐induced increases in soil temperature were the main drivers of the short‐term soil respiration responses, whereas longer‐term soil respiration responses to warming were primarily driven by thermal acclimation and warming‐induced reductions in biocrust cover. Our results highlight the importance of evaluating short‐ and longer‐term soil respiration responses to warming as a mean to reduce the uncertainty in predicting the soil carbon–climate feedback in drylands.

Aim: Cyanobacteria have shaped the history of life on Earth and continue to play important roles as carbon and nitrogen fixers in terrestrial ecosystems. However, their global distribution and ecological preferences remain poorly understood, particularly for two recently discovered non‐photosynthetic cyanobacterial classes (Sericytochromatia and Melainabacteria). Location: Two hundred and thirty‐seven locations across six continents encompassing multiple climates (arid, temperate, tropical, continental and polar) and vegetation types (forests, grasslands and shrublands). Time period: Sampling was carried out between 2003 and 2015. Major taxa studied: Photosynthetic and non‐photosynthetic cyanobacterial taxa. Methods: We conducted a field survey and used co‐occurrence network analysis and structural equation modelling to evaluate the distribution and environmental preferences of soil cyanobacteria across the globe. These ecological preferences were used to create a global atlas (predictive distribution maps) of soil cyanobacteria. Results: Network analyses identified three major groups of cyanobacterial taxa, which resembled the three main cyanobacterial classes: the photosynthetic Oxyphotobacteria‐dominated cluster, which were prevalent in arid and semi‐arid areas, and the non‐photosynthetic Sericytochromatia‐ and Melainabacteria‐dominated clusters, which preferred hyper‐arid oligotrophic and acidic/humid environments, respectively. Main conclusions: This study provides new insights into the environmental preferences of non‐photosynthetic cyanobacteria in soils globally. Our findings highlight the contrasting environmental preferences among the three clusters of cyanobacteria and suggest that alterations in environmental conditions linked to climate change might result in important changes in the ecology and biogeography of these functionally important microorganisms.

Understanding the present and future distribution of soil-borne plant pathogens is critical to supporting food and fibre production in a warmer world. Using data from a global field survey and a nine-year field experiment, we show that warmer temperatures increase the relative abundance of soil-borne potential fungal plant pathogens. Moreover, we provide a global atlas of these organisms along with future distribution projections under different climate change and land-use scenarios. These projections show an overall increase in the relative abundance of potential plant pathogens worldwide. This work advances our understanding of the global distribution of potential fungal plant pathogens and their sensitivity to ongoing climate and land-use changes, which is fundamental to reduce their incidence and impacts on terrestrial ecosystems globally.