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5 figuras.- 1 tabla.- This article is in Press, Journal Pre-proof, Climate change is a fundamental process affecting terrestrial ecosystems. However, there is relatively little knowledge about its impacts on soil communities, with a large degree of uncertainty regarding their resistance to predicted alterations in temperature and, particularly, precipitation. Moreover, most studies exploring the response of soil biota to predicted rainfall reduction have focused on mesic environments and soil microbes, which limit our ability to find general patterns across ecosystems and soil organisms. In this study, we analysed the impact of predicted climate change scenarios of rainfall reduction on soil food webs of Mediterranean water-limited forests using nematodes as bioindicators. We took advantage of replicated rainfall exclusion infrastructures (30% exclusion) established in Quercus forests of southern Spain in 2016 (2-year exclusion) and of southern France in 2003 (15-year exclusion) to explore the sensitivity of the soil food web to predicted reductions at short- and long-term scales. Rainfall reduction had large negative short-term effects on nematode abundance, particularly of lower trophic groups (bacterivores and fungivores). Rainfall reduction had also consistent short- and long-term impacts on community composition (decrease of fungivores, marginal increase of omnivores) and nematode-based indicators of soil food web structure (higher maturity and structure index, lower prey:predator ratio). These results can be considered indicative of a low resistance of the soil food web to rainfall reductions predicted by climate change. Overall, our findings demonstrate the sensitivity of water-limited forests to further reductions in soil water availability, which might substantially alter their soil communities and likely affect the many ecosystem processes that they control., This study was funded by the MICINN projects INTERCAPA (CGL2014-56739-R) and MICROFUN (RTI2018-094394-B-I00). P.H. was supported by a FPI-MICINN grant. L.M. was supported by the fellowship IV2 from VI-PPIT (Univ. Sevilla) and the project PID2019-108288RA-I00 (MINECO). OG acknowledges financial support provided by the Spanish Ministry of Economy and Competitiveness (MINECO) and by the European Social Fund through the Ramón y Cajal Program (RYC-2017-23666). Puéchabon is supported by the OSU OREME (UMS 3282) and the French national research infrastructure ANAEE-France (ANR-11-INBS-0001).

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.

11 páginas.- 5figuras.- 1 tablas.- referencias.- Supplementary data associated with this article can be found in the online version at doi:10.1016/j.agee.2023.108449 .- This work was framed in the net of experiments of the “Unidad Asociada Uso Sostenible del Suelo y el Agua en Agricultura” (CSIC-Universidad de Sevilla)., Climate change, especially in Mediterranean countries, might have a detrimental effect on agro‑ecosystems and agricultural production, as well as on the price, quantity and quality of the products. This study assesses the potential impact of drought predictions on a faba bean crop, and evaluates the adoption of conservation tillage practices to reduce this effect. For this purpose, a rainfall exclusion experiment was carried out in a Mediterranean rotation in Southwest Spain, where a long-term tillage experiment was running since 2008. Soil water storage (SWS), crop productivity and mineral nutrition, plant ecophysiology and biomass quality, as well as the colonization of roots by arbuscular mycorrhizal fungi (AMF) and symbiotic Rhizobium bacteria were evaluated over one growth cycle to study the combined effect of different tillage systems - non-tillage (NT), reduced tillage (RT) and traditional tillage (TT)- and rainfall reduction. Rainfall reduction had a negative impact on faba bean germination on the TT system, and on its aboveground biomass across the three tillage systems, but did not affect grain production. The percentage of biomass yield reduction by rainfall exclusion was 30% for NT, 50% for RT and 20% for TT. In the case of RT, low yields were influenced by a high incidence of weeds under rainfall reduction. The negative effect of water exclusion was especially evident on photosynthesis rates and stomatal conductance across all tillage types, while leaf water potential was affected by drought only in the TT system. These ecophysiological indicators were positively associated to some variables of arbuscular mycorrhizal colonization and Rhizobium nodulation in roots. Changes in the patterns of symbiotic interactions in response to drought depended on the tillage type. We conclude that, despite no effect on soil water storage, in the conservation tillage systems the increase in the mycorrhizal colonization in roots, particularly under NT, could be beneficial for plants to face drought stress. However, in a scenario of reduced rainfall it will be necessary to invest more resources in weed control under RT., This study was funded by FEDER funds research projects US-1260627 (Programa Operativo FEDER, Junta de Andalucía), by the Spanish Ministry of Science and Innovation (project PID2021–122628OB-I00 WASTE4DROUGHT and project CGL2017-85891-R DEGRAMED) and European funds. L. Morales thanks the Ministry of Science and Innovation for her FPI fellowship (PRE2018–084467). This work was framed in the net of experiments of the “Unidad Asociada Uso Sostenible del Suelo y el Agua en Agricultura” (CSIC-Universidad de Sevilla).

15 páginas.- 11 figuras.-. 7 tablas.- referencias, Sustainability and functioning of silvopastoral ecosystems are being threatened by the forecasted warmer and drier environments in the Mediterranean region. Scattered trees of these ecosystems could potentially mitigate the impact of climate change on herbaceous plant community but this issue has not yet tested experimentally. We carried out a field manipulative experiment of increased temperature (+2–3 °C) using Open Top Chambers and rainfall reduction (30%) through rain-exclusion shelters to evaluate how net primary productivity and digestibility respond to climate change over three consecutive years, and to test whether scattered trees could buffer the effects of higher aridity in Mediterranean dehesas. First, we observed that herbaceous communities located beneath tree canopy were less productive (351 g/m2) than in open grassland (493 g/m2) but had a higher digestibility (44% and 41%, respectively), likely promoted by tree shade and the higher soil fertility of this habitat. Second, both habitats responded similarly to climate change in terms of net primary productivity, with a 33% increase under warming and a 13% decrease under reduced rainfall. In contrast, biomass digestibility decreased under increased temperatures (−7.5%), since warming enhanced the fiber and lignin content and decreased the crude protein content of aerial biomass. This warming-induced effect on biomass digestibility only occurred in open grasslands, suggesting a buffering role of trees in mitigating the impact of climate change. Third, warming did not only affect these ecosystem processes in a direct way but also indirectly via changes in plant functional composition. Our findings suggest that climate change will alter both the quantity and quality of pasture production, with expected warmer conditions increasing net primary productivity but at the expense of reducing digestibility. This negative effect of warming on digestibility might be mitigated by scattered trees, highlighting the importance of implementing strategies and suitable management to control tree density in these ecosystems., Este trabajo fue apoyado por el proyecto MICINN DECAFUN ( CGL2015-70123-R ) y la Asociación de Amistad Hispano-Francesa (AVENIR-DIALOGO). MD Hidalgo-Galvez fue financiado por un contrato de ' Formación de Investigador Personal (FPI)' ( BES-2016-078248 ).

The constant provision of plant productivity is integral to supporting the liability of ecosystems and human wellbeing in global drylands. Drylands are paradigmatic examples of systems prone to experiencing abrupt changes in their functioning. Indeed, space-for-time substitution approaches suggest that abrupt changes in plant productivity are widespread, but this evidence is less clear using observational time series or experimental data at a large scale. Studying the prevalence and, most importantly, the unknown drivers of abrupt (rather than gradual) dynamical patterns in drylands may help to unveil hotspots of current and future dynamical instabilities in drylands. Using a 20-y global satellite-derived temporal assessment of dryland Normalized Difference Vegetation Index (NDVI), we show that 50% of all dryland ecosystems exhibiting gains or losses of NDVI are characterized by abrupt positive/negative temporal dynamics. We further show that abrupt changes are more common among negative than positive NDVI trends and can be found in global regions suffering recent droughts, particularly around critical aridity thresholds. Positive abrupt dynamics are found most in ecosystems with low seasonal variability or high aridity. Our work unveils the high importance of climate variability on triggering abrupt shifts in vegetation and it provides missing evidence of increasing abruptness in systems intensively managed by humans, with low soil organic carbon contents, or around specific aridity thresholds. These results highlight that abrupt changes in dryland dynamics are very common, especially for productivity losses, pinpoint global hotspots of dryland vulnerability, and identify drivers that could be targeted for effective dryland management., Proceedings of the National Academy of Sciences of the United States of America, 119 (43), ISSN:0027-8424, ISSN:1091-6490