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7 páginas.- 4 figuras.- 32 referencias.- Supplementary materials: science.org/doi/10.1126/science.abq4062 Materials and Methods Figs. S1 to S19 Tables S1 to S28 References (33–269) MDAR Reproducibility Checklist Movie S1.- Grazing represents the most extensive use of land worldwide. Yet its impacts on ecosystem services remain uncertain because pervasive interactions between grazing pressure, climate, soil properties, and biodiversity may occur but have never been addressed simultaneously. Using a standardized survey at 98 sites across six continents, we show that interactions between grazing pressure, climate, soil, and biodiversity are critical to explain the delivery of fundamental ecosystem services across drylands worldwide. Increasing grazing pressure reduced ecosystem service delivery in warmer and speciespoor drylands, whereas positive effects of grazing were observed in colder and species-rich areas. Considering interactions between grazing and local abiotic and biotic factors is key for understanding the fate of dryland ecosystems under climate change and increasing human pressure. Copyright © 2022 the authors, Grazing represents the most extensive use of land worldwide. Yet its impacts on ecosystem services remain uncertain because pervasive interactions between grazing pressure, climate, soil properties, and biodiversity may occur but have never been addressed simultaneously. Using a standardized survey at 98 sites across six continents, we show that interactions between grazing pressure, climate, soil, and biodiversity are critical to explain the delivery of fundamental ecosystem services across drylands worldwide. Increasing grazing pressure reduced ecosystem service delivery in warmer and species-poor drylands, whereas positive effects of grazing were observed in colder and species-rich areas. Considering interactions between grazing and local abiotic and biotic factors is key for understanding the fate of dryland ecosystems under climate change and increasing human pressure. Copyright © 2022 the authors, Funding: This research was funded by the European Research Council [ERC grant agreement 647038 (BIODESERT)] and Generalitat Valenciana (CIDEGENT/2018/ 041). F.T.M. acknowledges support from a Rei Jaume I Award, the Alexander von Humboldt Foundation, and the Synthesis Center (sDiv) of the German Centre for Integrative Biodiversity Research Halle–Jena–Leipzig (iDiv). C.A.G., S.C., and N.E. acknowledge support from iDiv and the Deutsche Forschungsgemeinschaft (DFG– FZT 118, 202548816; Flexpool proposal 34600850). Y.L.B.-P. was supported by a Marie Sklodowska-Curie Actions Individual Fellowship (MSCA-IF) within the European Program Horizon 2020 (DRYFUN Project 656035). N.G. was supported by CAP 20-25 (16-IDEX-0001) and the AgreenSkills+ fellowship program, which has received funding from the EU’s Seventh Framework Programme under grant agreement N° FP7-609398 (AgreenSkills+ contract). B.B. and B.E. were supported by the Taylor Family–Asia Foundation Endowed Chair in Ecology and Conservation Biology. J.D., A.Ro., and H.C. acknowledge support from the Fundação para a Ciência e a Tecnologia (IF/00950/ 2014 and 2020.03670.CEECIND, SFRH/BDP/108913/2015, and in the scope of the framework contract foreseen in the numbers 4-6 of the article 23, of the Decree-Law 57/2016, August 29, changed by Law 57/2017, July 19, respectively), as well as from the MCTES, FSE, UE, and the CFE (UIDB/04004/2020) research unit financed by Fundação para a Ciência e a Tecnologia/MCTES through national funds (PIDDAC). C.P. acknowledges support from the Spanish Ministry of Science and Innovation (ref. AGL201675762-R, AEI/FEDER, UE, and PID2020-116578RB-I00, MCIN/AEI/10.13039/501100011033) and the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement no. 101000224. E.V. was funded by the 2017 program for attracting and retaining talent of Comunidad de Madrid (no. 2017‐T2/ AMB‐5406). M.A.B. acknowledges support from the School of Forestry and College of the Environment, Forestry and Natural Sciences of Northern Arizona University. E.H.-S. acknowledges support from the Consejo Nacional de Ciencia y Tecnología (SEP-CB-2015-01-251388, PN 2017-5036 and PRONAII 319059). F.M.H. acknowledges support from the National Council for Scientific and Technological Development (CNPq - PCI/INMA) of the Brazilian Ministry of Science, Technology and Innovation (MCTI, processes number 302381/2020-1). H.L.T. acknowledges support from the US National Science Foundation (NSF) (DEB 0953864). A.N. and M.K. acknowledge support from the Fundação para a Ciência e a Tecnologia (SFRH/BD/130274/2017, CEECIND/02453/2018/CP1534/CT0001, PTDC/ASP-SIL/7743/2020 and UIDB/00329/2020). A.A.C. acknowledges support from the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001. J.E.K. and T.P.M. acknowledge the National Research Foundation of South Africa (grant no. 114412). F.J. and N.B. acknowledge support from the German Federal Ministry of Education and Research (BMBF) in the framework of the SPACES projects OPTIMASS (FKZ: 01LL1302A) and ORYCS (FKZ:01LL1804A). A.Li. and A.S.K.F. acknowledge support from the German Federal Ministry of Education and Research (BMBF) in the framework of the SPACES projects Limpopo Living Landscapes (FKZ: 01LL1304D) and SALLnet (FKZ: 01LL1802C). L.W. acknowledges support from the US NSF (EAR 1554894). L.H.F. acknowledges support from the Natural Sciences and Engineering Research Council of Canada Industrial Research Chair Program in Ecosystem Reclamation. S.C.R. acknowledges support from the US Geological Survey Ecosystems Mission Area and the US Bureau of Land Management. G.M.W. acknowledges support from the Australian Research Council. L.v.d.B. and K.T. acknowledge support from the German Research Foundation (DFG) priority research program SPP-1803 “EarthShape: Earth Surface Shaping by Biota” (TI 338/14-1). 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). P.J.R. and A.J.M. acknowledge support from Fondo Europeo de Desarrollo Regional through the FEDER Andalucía operative program, FEDER-UJA 1261180 project. A.F. thanks ANID PIA/BASAL FB210006 and Millennium Science Initiative Program NCN2021-050. A.J. acknowledges support from the Bavarian Research Alliance Germany (BayIntAn_UBT_2017_61). C.B. acknowledges the National Natural Science Foundation of China (grant no. 41971131). Biodiversity and ecosystem function research in the B.K.S. laboratory is funded by the Australian Research Council (DP210102081). Any use of trade, product, or firm names in this paper is for descriptive purposes only and does not imply endorsement by the US government. H.S. is supported by a María Zambrano fellowship funded by the Ministry of Universities and European Union-Next Generation plan. G.P. and C.V.L. acknowledge support from Universidad Nacional de Río Negro (PI 40-C-873 and 654). V.R. acknowledges support from the Regional Government of Extremadura (Spain) through a “Talento” fellowship (TA18022). M.F. acknowledges support from the Department of Range and Watershed Management, Ferdowsi University of Mashhad, Mashhad, Iran. Participation of recent graduates in collecting field data at four sites in Namibia was supported by a capacity building grant to Gobabeb–Namib Research Institute by the Environmental Investment Fund in Namibia.

Description du sujet. Ces quatre dernières décennies ont été marquées par la lutte contre la désertification et la protection des écosystèmes steppiques, devenues des priorités en Algérie. Plusieurs modalités de restauration ont été retenues pour gérer, voire restaurer les parcours steppiques sensibles. Objectifs. L’étude menée vise à quantifier l’effet de deux techniques de restauration (mise en défens et plantation fourragère) quatre ans après leur mise en place sur le recouvrement par la végétation, les paramètres physico-chimiques du sol et l’état de sa surface dans des parcours arides algériens initialement dégradés. Méthode. Trois-cent-douze relevés phytoécologiques et pédologiques ont été effectués quatre ans après la mise en œuvre de la gestion (plantation + mise en défens ou mise en défens seule) ainsi que sur des parcelles non aménagées. Des paramètres descripteurs de la végétation, les éléments de la surface du sol et les paramètres chimiques des horizons de surface ont été mesurés pour chaque modalité de traitement.Résultats. De nombreux paramètres phytoécologiques et édaphiques sont significativement différents dans les espaces restaurés par rapport aux espaces non aménagés, particulièrement les taux d’azote total et de matière organique. Les paramètres granulométriques sont stables.Conclusions. Notre étude montre que les deux techniques de restauration dans les régions arides permettent en un temps relativement court (quatre ans) une amélioration des propriétés physico-chimiques du sol. Nous suggérons l’utilisation du pourcentage de la surface du sol sous forme d’éléments grossiers comme indicateur de l’état de restauration du système et comme aide à la décision de rouvrir au pâturage les surfaces restaurées., Fencing and planting: two restoration strategies for the improvement of vegetation, soil fertility and soil surface properties in Algerian arid rangelandsDescription of the subject. The struggle against desertification and the implementation of consecutive steppic ecosystem protection plans have become a priority in Algeria over the last four decades. Among the restoration techniques set up to manage or even restore sensitive steppic rangelands have been (i) fencing and (ii) fencing and the planting of exotic shrubs. Objectives. This study aims at describing the effect of these two restoration modes with control plots after four years on soil physico-chemical and surface state parameters and phyto-ecological properties.Method. Three hundred twelve phyto-ecological and pedological relevés were performed both on the restored plots and on controls four years after the initial implementation of management strategies. Phyto-ecological, soil surface and soil chemical parameters were measured for each modality.Results. Numerous parameters differed between the restored plots and the controls, including levels of total nitrogen and soil organic matter. However, textural parameters did not differ between the restored and the control plots.Conclusions. Our study shows that the implementation of both the restoration techniques in an arid region led within a relatively short space of time (four years) to an improvement in soil physico-chemical properties. We recommend the measurement of the percentage of coarse elements on the soil surface as an indicator of the system restoration state, and the use of the results as an important decision-making tool in reopening restored areas to grazing.

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