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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.

10 Pags.- 4 Figs.- 1 Tabl. © 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license, The surface of many European mountain grasslands is decreasing due to global change and extensive grazing stands out as a key tool for their conservation. Sound knowledge of grassland ecosystem functioning and its feedback processes is required to implement sustainable grazing management. This study aimed to understand the effect of different grazing intensities on herbivore-plant-soil feedbacks in Mediterranean mountain grasslands. We estimated spatial distribution of sheep grazing intensity using GPS technology in order to assess the effect of grazing pressure on vegetation and soil properties measured throughout the study area. Our results showed that grazing intensity ranged from 0.06 to 2.85 livestock units / ha, corresponding to a gradient of pasture utilisation rates varying from 2.38% to 45.60% of annual productivity from pasture. Increasing grazing pressure was associated with smaller relative cover and species richness of non-leguminous forbs, while the opposite trends were observed for graminoids. Forage had a greater concentration of N and smaller C:N ratio in more heavily grazed areas. Increasing grazing intensity was also associated with higher values of total soil N, NO3-, NH4+, soil organic carbon, microbial biomass C and activity of β-glucosidase. Higher litter quality was the main factor explaining greater content of soil organic matter, which favoured both soil microbes and plant productivity. Grazing induced changes in the plant community triggered positive hervibore-plant-soil feedbacks, as they ultimately improved forage quality and productivity, which significantly influenced the pasture preference of free-ranging domestic grazers. Our work showed that grazing management aiming pasture utilisation rates of around 45% is critical in sustaining positive herbivore-plant-soil feedbacks and preserving or enhancing the whole ecosystem functioning in the Mediterranean mountain grasslands studied., This work was funded by Ministerio de Ciencia, Innovación y Universidades del Gobierno de España, Spain (project CGL2016-80783-R, 2016; and Ph.D. scholarship FPU16/05508, 2016).

Pastoralism is a traditional land use in the Mediterranean region lasting for several thousands of years, where vegetation and animal communities are adapted to deal with summer drought periods and grazing pressure. There is a difference between the two shores of the Mediterranean in terms of pastoralism, it is more a mode of subsistence in the South, whereas in the North is a complementary activity each time less profitable. In addition, there is a clear North-South climatic gradient that determines rangelands productivity, carrying capacity, sustainable management and resilience. The environmental and socio-economical differences among the Northern and the Southern shores of the basin determine separated trends in both shores, leading to different management and future perspectives of rangelands. In addition to climate, differences in demographic pressure and socio-economical context influence rangeland status across the Mediterranean basin. Abandonment of grazing activities in North Mediterranean region vs. grazing intensification or even sedentarization in South Mediterranean region are the main socio-economical drivers, with important consequences on rangeland conservation. Despite regional differences, global warming affects the Mediterranean rangelands as a whole, increasing the shortage of water availability and the summer stress. These common perspective should promote that northern and southern rangeland managers and researchers learn from each other to deal with rangeland conservation, management and restoration. The latest research address pastoral production systems as a whole, and considers pastoral improvement techniques as a component in a holistic approach.

Reduced precipitation treatments often are used in field experiments to explore the effects of drought on plant productivity and species composition. However, in seasonally snow-covered regions reduced precipitation also reduces snow cover, which can increase soil frost depth, decrease minimum soil temperatures and increase soil freeze-thaw cycles. Therefore, in addition to the effects of reduced precipitation on plants via drought, freezing damage to overwintering plant tissues at or below the soil surface could further affect plant productivity and relative species abundances during the growing season. We examined the effects of both reduced rainfall (via rain-out shelters) and reduced snow cover (via snow removal) at 13 sites globally (primarily grasslands) within the framework of the International Drought Experiment, a coordinated distributed experiment. Plant cover was estimated at the species level and aboveground biomass was quantified at the functional group level. Among sites, we observed a negative correlation between the snow removal effect on minimum soil temperature and plant biomass production the next growing season. Three sites exhibited significant rain-out shelter effects on plant productivity, but there was no correlation among sites between the rain-out shelter effect on minimum soil moisture and plant biomass. There was no interaction between snow removal and rain-out shelters for plant biomass, although these two factors only exhibited significant effects simultaneously for a single site. Overall, our results reveal that reduced snowfall, when it decreases minimum soil temperatures, can be an important component of the total effect of reduced precipitation on plant productivity.

Additional file 1. Methods and results for the determination of aqueous extracts concentration.

10 páginas, 5 figuras, 3 tablas.-- El PDF del artículo es la copia de autor. There is increased interest in vegetation spatial pattern as an indicator of transition shifts following catastrophes. Much, however, remains unknown about the mechanisms that underlie spatial pattern formations. In this study, we examined how the spatial heterogeneity of species distributions in the grasslands of the Central Pyrenees and Middle Atlas Mountains is associated with plant species diversity and the importance of self-organizing processes in the control of pattern formations. In the grasslands of the Central Pyrenees and Middle Atlas, the spatial heterogeneity of species distributions increased along a habitat degradation gradient defined by an increase in bare soil. In Central Pyrenees grasslands, however, the increase in heterogeneity was associated with self-organizing bare soil formations, rather than the self-organizing distribution of plant species. In Middle Atlas grasslands, the increased heterogeneity of species spatial distributions was a consequence of the self-organizing capacity of the composing species; the increase in bare soil was randomly distributed. In the more heavily grazed grasslands (Middle Atlas), but not in the more lightly grazed and better preserved ecosystem (Central Pyrenees), plant species richness and diversity declined significantly with an increase in grazing pressure because fewer species were able to colonize empty space. On the contrary, the colonization of bare soil by new species increased the diversity and spatial organization of new colonizing species in Central Pyrenees grassland. We gratefully acknowledge the support of the Spanish CICYT (Project Parques Nacionales 059/2002) Valoraci ´on ecol ´ogica y productiva de los pastos supraforestales del PNOMP. The research was part of the DRASME (Desertification Risk Assessment in Silvopastoral Mediterranean Ecosystems) Collaborative Research Project. DRASME is funded by the EU under the INCO-DC Program(contract number ERBIC18-CT98-0392). The support from both programs is gratefully acknowledged.

International audience

Soil water presents high temporal and spatial variability in drylands. The temporal variability is determined by the heterogeneous and unpredictable rainfall pattern in these ecosystems. The spatial variability is associated to the well-known “source-sink” eco-hydrological dynamics occurring in drylands, related to the patchy vegetation and bare soil structure with water run-off generated on the bare soil patches and water infiltration preferentially into vegetated areas. These run-off – run-on systems has been extensively studied and the processes involved are well known, including the role of different plant types capturing the water run-on, increasing infiltration and reducing evaporation under plant canopies. However, integrative studies of hydrological and ecological processes in a whole ecosystem during a prolonged time period are scarce, despite the relevance of this approach to understand the role of hydrological processes (and what hydrological process are most important) determining plant dynamics and spatial pattern. We present an eco-hydrological study conducted in a semiarid Mediterranean ecosystem in the Middle Ebro Valley (NE Spain), where soil water content and patterns of plant establishment were followed during 30 months in 4 microsites: open bare areas, under two shrub species (Salsola vermiculata and Artemisia herba-alba) and one perennial grass species (Lygeum spartum). These 4 microsites represent the vast majority of the land in the ecosystem under study. Water infiltration, photosynthetic photon flux and soil temperature were also recorded in the 4 microsites. Simultaneously, seedling establishment and survival were recorded twice per year in the same microsites. Lygeum spartum was the microsite with the largest increment in water infiltration, and with the largest reduction in both solar radiation and soil temperature when compared with the measurement in the open bare areas. However, soil water content after rainfall under the canopy of Salsola vermiculata was the largest, indicating that canopy interception could be a less relevant process under the canopy of S. vermiculata than under the canopy of L. spartum. Moreover, there was an interactive effect of the soil water content before rainfall and the magnitude of the rainfall with the microsite (i.e. wet bare soils infiltrated more water than dry bare soils, being this difference less relevant in the vegetated microsites). Patterns of seedling establishment and survival correlated to patterns in soil water content, pointing out the relevance of the eco-hydrological spatio-temporal heterogeneity in the dynamics and spatial pattern of plant communities. Seedling establishment occurs in the first centimetres of soil, where competition for water (under Lygeum spartum) and evaporation (in the open bare soil areas) seems to reduce the water availability for plant establishment.

4 Pags., 2 Figs., El pastoreo modifica las condiciones edáficas de los ecosistemas pastorales, siendo la compactación del suelo uno de los principales efectos. Este trabajo estudia el efecto del pastoreo sobre las propiedades hidro-físicas de un suelo localizado en la zona semiárida del centro del valle del Ebro. Para tal fin se seleccionó, sobre un mismo tipo de suelo, dos tratamientos diferentes con pastoreo (P) y sin pastoreo (NP) de ganado ovino. Se efectuaron las siguientes medidas sobre el horizonte superficial del suelo (0-10 cm): contenido en yeso, CaCO3 y materia orgánica (MO), textura del suelo, densidad aparente (b), resistencia del suelo a la penetración (RP), sorptividad (S) y conductividad hidráulica (K) del suelo a saturación y curva de retención de agua (CRA) en muestras inalteradas de suelo. Los resultados muestran un contenido de MO similar en ambos tratamientos. Los valores de b y RP observados en P fueron mayores a los medidos en NP. Como consecuencia, los resultados muestran como el pastoreo tiene un efecto negativo sobre la infiltración de agua en el suelo, que se manifiesta por una menor K y S, y sobre la curva de retención de agua en muestras inalteradas de suelo, cuyos tratamientos pastados muestras una menor capacidad de almacenamiento de agua., El presente trabajo ha sido financiado los proyecto DGA-Obra social La Caixa, Ref: GA-LC020/2010; GA-LC-010/2008.

24 páginas, [ES] La tendencia general de la población humana en el Parque Nacional de Ordesa y Monte Perdido (PNOMP) durante la segunda mitad del siglo XX ha sido su migración desde los pueblos y áreas rurales a las grandes urbes industrializadas. Como consecuencia la presión de la ganadería disminuyó, dando lugar a la invasión de especies leñosas en los pastos (matorralización). No obstante, en determinadas situaciones, los pastos alpinos han mostrado un alto grado de persistencia, permaneciendo con pocos cambios específicos después de 20 años de exclusión al pastoreo. En este proyecto investigamos la influencia de los factores biofísicos y antrópicos sobre los procesos de matorralización. Los resultados obtenidos de las comparaciones entre las tres imágenes de satélite (1989, 1998 y 2007) y entre tres fotografías aéreas (1957, 1981 y 2003), revelaron un incremento del bosque y del matorral y una disminución de la superficie de pastos. Asociados a esos cambios observamos un incremento de las poblaciones de ungulados silvestres, tales como el jabalí Sus scrofa. El incremento del jabalí ha provocado un aumento de sus perturbaciones, principalmente hozaduras, en los pastos alpinos del PNOMP. Estas perturbaciones a su vez modifican e incluso puede llegar a degradar estos pastos. Una de las especies que presenta una mayor influencia en la reducción de los pastos es el erizón, Echinospartum horridum, debido a su capacidad de expansión, formando grandes y densas manchas monoespecíficas que pueden cubrir varias hectáreas, y dónde sólo unas pocas especies sobreviven en los pequeños claros. La velocidad de expansión del erizón entre 1981 y 2003 varió entre 2,09 m año-1 en las pendientes elevadas a 1,93 m año-1 en las pendientes suaves. El modelo de enrejado realizado para simular la expansión de E. horridum con los valores de los parámetros estimados en el campo, dio como resultado una tasa de expansión similar a la observada. Se simularon diferentes escenarios de gestión consistentes en un gradiente de pastoreo y de quemas controladas para identificar diferentes situaciones de control de la expansión del erizón en los pastos. La dinámica de la población sugiere que la colonización del erizón continuará en los pastos del PNOMP., [EN] The general human population trend in Ordesa and Monte Perdido National Park (OMPNP) during the second half of the XX century has been its migration from the villages to the big nearest industrialized cities. Consequently, livestock pressure declined, leading to the invasion of woody species into the grasslands. Nevertheless, if grasslands have not been invaded by shrubs, alpine grasslands showed a large inertia to change after 20 years of exclusion from grazing. Results of the comparisons between the three satellite images (1989, 1998 and 2007) and the three aerial photographs (1957, 1981 and 2003) revealed an increase of forest and shrublands and a declining of grasslands. The influence of biophysical and anthropic variables on those changes was investigated. Associated to those changes we observed an increase of wild ungulates as wild boar Sus scrofa. The increase in wild boar numbers has led to an increase in the extent of its disturbances, mainly rooting, in the alpine and subalpine grasslands of OMPNP. These rooting modify and may even degrade these grasslands. One of the species that is showing a larger influence on the grassland reduction is Echinospartun horridum, which forms large and dense monospecific patches that can cover several hectares, where only a few other plant species survive within small gaps. The speed of diffusion from 1981 to 2003 varied from 2.09 m year-1 on the steep slopes to 1.93 m year-1 on the less pronounced slopes. The lattice-structured model performed to simulate encroachment by the E. horridum using parameter values estimated in the field generated an erizón expansion rate equivalent to the one observed in the field. Different management scenarios consisting of a gradient of livestock pressures and fire events were simulated to identify scenarios able to control the expansion of E. horridum into grasslands. Plant dynamics suggest that colonization by E. horridum will continue in the grasslands of the OMPNP., Agradecemos al Organismo Autónomo Parques Nacionales del Ministerio de Medio Ambiente y Medio Rural y Marino, la financiación del proyecto 002/2007. Agradecemos además de forma especial la atención y apoyo que nos prestó en todo momento la guardería y personal del Parque Nacional de Ordesa. JJC agradece el apoyo de ARAID.