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9 páginas.- 4 figuras.- 38 referemcias.- Supplementary information The online version contains supplementary material available at https://doi.org/10.1038/s41558-023-01627-2, Increasing the number of environmental stressors could decrease ecosystem functioning in soils. Yet this relationship has not been globally assessed outside laboratory experiments. Here, using two independent global standardized field surveys, and a range of natural and human factors, we test the relationship between the number of environmental stressors exceeding different critical thresholds and the maintenance of multiple ecosystem services across biomes. Our analysis shows that having multiple stressors, from medium levels (>50%), negatively and significantly correlates with impacts on ecosystem services and that having multiple stressors crossing a high-level critical threshold (over 75% of maximum observed levels) reduces soil biodiversity and functioning globally. The number of environmental stressors exceeding the >75% threshold was consistently seen as an important predictor of multiple ecosystem services, therefore improving prediction of ecosystem functioning. Our findings highlight the need to reduce the dimensionality of the human footprint on ecosystems to conserve biodiversity and function., This project received funding from the British Ecological Society (agreement no. LRA17\1193; MUSGONET). M.D.-B. acknowledges support from the Spanish Ministry of Science and Innovation for the I+D+i project PID2020-115813RA-I00 funded by MCIN/AEI/10.13039/501100011033. M.D.-B. is also supported by a project of the Fondo Europeo de Desarrollo Regional (FEDER) and the Consejería de Transformación Económica, Industria, Conocimiento y Universidades of the Junta de Andalucía (FEDER Andalucía 2014-2020 Objetivo temático ‘01 - Refuerzo de la investigación, el desarrollo tecnológico y la innovación’) associated with the research project P20_00879 (ANDABIOMA). E.M.-J. thanks the Alexander von Humboldt Foundation for supporting his research stay in Germany (Fellowship for Experienced Researchers). M.C.R. acknowledges support from an ERC Advanced Grant (694368). M.G.A.H. acknowledges funding from the Swiss National Science Foundation (grant 310030_188799). M.B. is supported by Spanish Ministry of Science and Innovation through a Ramón y Cajal Fellowship (# RYC2021-031797-I)

11 páginas.- 4 figuras.- referencias.- Additional supporting information can be found online in the Supporting Information section at the end of this article., Soil micronutrients are capital for the delivery of ecosystem functioning and food provision worldwide. Yet, despite their importance, the global biogeography and ecological drivers of soil micronutrients remain virtually unknown, limiting our capacity to anticipate abrupt unexpected changes in soil micronutrients in the face of climate change. Here, we analyzed >1300 topsoil samples to examine the global distribution of six metallic micronutrients (Cu, Fe, Mn, Zn, Co and Ni) across all continents, climates and vegetation types. We found that warmer arid and tropical ecosystems, present in the least developed countries, sustain the lowest contents of multiple soil micronutrients. We further provide evidence that temperature increases may potentially result in abrupt and simultaneous reductions in the content of multiple soil micronutrients when a temperature threshold of 12–14°C is crossed, which may be occurring on 3% of the planet over the next century. Altogether, our findings provide fundamental understanding of the global distribution of soil micronutrients, with direct implications for the maintenance of ecosystem functioning, rangeland management and food production in the warmest and poorest regions of the planet., The sampling included in this study were supported by the European Research Council (ERC) grant 647038 (BIODESERT), the BES grant agreement No. LRB17\1019 (MUSGONET) and the Marie Skłodowska-Curie grant agreement 702057 (CLIMIFUN). We would like to thank the researchers originally involved in the BIODESERT, CLIMIFUN and MUSGONET projects for their help with samplings. E.M.-J. acknowledges the Humboldt Foundation for supporting his research stay in Germany (Fellowship for Experienced Researchers) and a project from the Spanish Ministry of Science and Innovation (PID2020-116578RB-I00). M.D.-B. is supported by a Ramón y Cajal grant (RYC2018-025483-I), a project from the Spanish Ministry of Science and Innovation (PID2020-115813RA-I00) and a project PAIDI 2020 from the Junta de Andalucía (P20_00879). E.G. is supported by the Conselleria de Innovación, Universidades, Ciencia y Sociedad Digital de la Generalitat Valenciana, and the European Social Fund grant APOSTD/2021/188 and European Research Council (ERC) grant 647038. F.T.M. is supported by European Research Council (ERC) grant 647038 and Generalitat Valenciana grant CIDEGENT/2018/041. M.D. and T.W.C. were funded by the Marc R. Benioff Revocable Trust and in collaboration with the World Economic Forum. This article is part of the contract between ETH Zurich and University of Alicante “Mapping terrestrial ecosystem structure at the global scale”. R.O.H. is supported by the Ramón y Cajal program from the MICINN (RYC-2017 22032), a PAIDI 2020 project from the Junta de Andalucía (Ref. 20_00323) and a project from the Spanish Ministry of Science and Innovation (PID2019-106004RA-I00/AEI/10.13039/501100011033). Authors acknowledge support by the Open Access Publication Initiative of Freie Universität Berlin. Open Access funding enabled and organized by Projekt DEAL.

Despite the centrality of staple grains for human well-being, both as a source of nutrients and of toxic ions, there is little understanding of where and how elements vary, and if there are particular elements that correlate. Here, for shop bought polished (white) rice, we comprehensively characterized trace (arsenic species, cadmium, copper, iron, manganese, molybdenum, rubidium and zinc) and macro-nutrients (calcium, chlorine, potassium, phosphorus and sulphur) for grain purchased in 18 countries, across four continents, a total of 1045 samples. This was to investigate if there were any major differences between geographic location and elemental content, and to observe if there were any patterns in elemental distribution. Greatest variation in the median was observed for the non-essential rubidium (15-fold) and arsenic species (fivefold). Rubidium was the highest in the Americas, lowest in Europe, while inorganic arsenic (iAs) and dimethylarsonic acid (DMA) were low for Africa and high in the South American and European continents. The highest concentrations of cadmium were found in Asian samples, and lowest in South America, with variation within these regions. At the extremes of individual counties, China had fivefold higher concentrations than the global median, while Tanzania was fourfold lower than this value. Calcium, potassium, molybdenum and phosphorus were the highest in European and lowest in African grain, though the fold-differences were relatively low, ~ 0.2, while iron was the highest in African grain and lowest in European, Asian and South American grain, with a ~ twofold difference. Selenium was also higher in Africa versus other regions, and copper, manganese and zinc were the highest in American grain. Factor analysis showed that copper, cadmium, molybdenum, rubidium and selenium were strongly associated together, and these element’s factor loadings were diametrically opposed to less tightly associated calcium, chlorine, manganese, potassium, phosphorus and sulphur. Stepwise additions linear region analysis was performed on log-transformed concentrations to investigate cadmium associations in more detail. Selenium was the greatest predictor of cadmium concentration, followed by molybdenum, accounting for over 50% of the contribution to the adjusted R2. Arsenic species were only weakly correlated with other elements. The implications for these findings with respect to dietary nutrition are discussed. Vietnamese rice was notable in being deficient in macro- and micro-nutrients while also being elevated in cadmium at a median of 0.02 mg/kg, with China though still having a median that is ~ 2.5-fold this concentration. These Chinese concentrations are of particular concern as the 75th percentile for China is 0.1 mg/kg, a value that triggers regulatory action for rice products.

The release of arsenic (As) adsorbed onto iron oxide (Fe-oxide) surfaces is affected by dissolved organic matter (DOM), phosphate (hereafter referred to as PO4), and silicic acid (H4SiO4). Further, the reductive dissolution of As from Fe-oxide phases is also affected in reduced soils and sediments. Thus, the aim of this study was to understand the adsorption competition and redox-related mechanisms by which DOM affects As mobilization from Fe-oxide in a complex system containing both H4SiO4 and PO4. The results demonstrated that the DOM-driven, microbially mediated As biotransformation, and, thus, mobilization of As significantly increased when both dissolved inorganic H4SiO4 and PO4 were present, as the co-presence of H4SiO4 and PO4 decreased As adsorption sites on Fe-oxides. The availability of DOM in the co-presence of H4SiO4 and PO4 increased the microbial activity in the system by providing more substrates for microbial metabolism, which also decreased the redox potential (reducing conditions) and consumed acidity, causing the pH to increase from 4 to 6.8. In addition, DOM, H4SiO4, and PO4 competed with As for sorption sites on Fe-oxides. The effects of DOM on As mobility by DOM-mediated or -triggered redox reactions were apparently stronger in the co-presence of H4SiO4 and PO4 than DOM competition with arsenate for sorption sites on Fe-oxide alone. These findings advance our understanding of As mobilization processes in natural systems and can provide information for soil As management.

Despite the centrality of staple grains for human well-being, both as a source of nutrients and of toxic ions, there is little understanding of where and how elements vary, and if there are particular elements that correlate. Here, for shop bought polished (white) rice we comprehensively characterize trace (arsenic species, cadmium, copper, iron, manganese, molybdenum, rubidium and zinc) and macro-nutrients (calcium, chlorine, potassium, phosphorus and sulphur) for grain purchased in 18 countries, across 4 continents, a total of 1045 samples, to investigate if there were any major differences between geographic location and elemental content, and to observe if there were any patterns in elemental distribution. Greatest variation in the median was observed for the non-essential rubidium (15-fold) and arsenic species (5-fold). Rubidium was highest in the Americas, lowest in Europe, while inorganic arsenic and dimethylarsonic acid (DMA) were low for Africa and high in the South American and European continents. Cadmium had the highest concentration in Asian samples and lowest in South America. Calcium, potassium, molybdenum and phosphorus, were highest in European and lowest in African grain, though the fold-differences were relatively low, ~ 0.2, while iron was highest in African grain and low in European, Asian and South American grain, with a ~ 2-fold difference. Selenium was also higher in Africa versus other regions, and copper, manganese and zinc where highest in American grain. Factor analysis showed that copper, cadmium, molybdenum, rubidium and selenium were strongly associated together, and these element’s factor loadings were diametrically opposed to less tightly associated calcium, chlorine, manganese, potassium, phosphorus and sulphur. Stepwise additions linear region analysis was performed on log transformed concentrations to investigate cadmium associations in more detail. Selenium was the greatest predictor of cadmium concentration, followed by molybdenum, accounting for over 50% of the contribution to the adjusted R2. Arsenic species were only weakly correlated with other elements. The implications for these findings with respect to dietary nutrition are discussed.

Dryland soils provide different societal and environmental services, such as food supply and biodiversity support. In Europe, most of the dryland areas are devoted to agriculture. In the next decades, both European and worldwide drylands are expected to suffer with increased intensity due to the expected climate change-derived rise in aridity. Many studies have focussed on aridity-induced changes in major nutrients in drylands, but little is known of the impact of environmental and biogeochemical factors on micronutrients with critical roles in life, and as inorganic contaminants with ecotoxicological implications. We analysed and explored drivers of total and available concentrations of micronutrients (Co, Cu, Fe, Mo, Mn, Ni and Zn) and contaminants (As, Cd and Pb) in 148 soil samples collected from European drylands covering a wide range of aridity and of other geochemical parameters. The availability of micronutrients increased with their total content, decreased with pH and was enhanced by organic C content. Aridity decreased the availability of Fe, a key element in human diet. Our findings also highlight the scarcity of this micronutrient in European drylands, as well as of some other important micronutrients like Zn and Mo in agricultural soils. Total content was the main driver of the availability of Cd and Pb, and organic matter exerted synergistic effects on contaminant release. Our data show the need for precise management practices to be incentivised by agricultural and environmental policies in order to ensure micronutrient supply and avoid contamination, thus maintaining adequate levels of agricultural productivity and simultaneously preserving dryland ecosystems. Highlights: Drylands are important for food production in Europe and sensitive to climate change. The occurrence of metals in European Union dry soils and the drivers influencing them were studied. Some micronutrients (Fe, Mo and Zn) were scarce while contaminants were abundant. SOC, pH and clays were the main drivers of element availability; aridity reduced Fe. Agricultural practises are needed to ensure nutrient supply and prevent contamination., This work was funded by a 2018 Leonardo Grant for Researchers and Cultural Creators of the Fundación BBVA (Spain).