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Greater scientific knowledge, changing societal values, and legislative mandates have emphasized the importance of implementing large-scale flow experiments (FEs) downstream of dams. We provide the first global assessment of FEs to evaluate their success in advancing science and informing management decisions. Systematic review of 113 FEs across 20 countries revealed that clear articulation of experimental objectives, while not universally practiced, was crucial for achieving management outcomes and changing dam-operating policies. Furthermore, changes to dam operations were three times less likely when FEs were conducted primarily for scientific purposes. Despite the recognized importance of riverine flow regimes, four-fifths of FEs involved only discrete flow events. Over three-quarters of FEs documented both abiotic and biotic outcomes, but only one-third examined multiple taxonomic responses, thus limiting how FE results can inform holistic dam management. Future FEs will present new opportunities to advance scientifically credible water policies. ; Full Text

Global change threatens invertebrate biodiversity and its central role in numerous ecosystem functions and services. Functional trait analyses have been advocated to uncover global mechanisms behind biodiversity responses to environmental change, but the application of this approach for invertebrates is underdeveloped relative to other organism groups. From an evaluation of 363 records comprising >1.23 million invertebrates collected from rivers across nine biogeographic regions on three continents, consistent responses of community trait composition and diversity to replicated gradients of reduced glacier cover are demonstrated. After accounting for a systematic regional effect of latitude, the processes shaping river invertebrate functional diversity are globally consistent. Analyses nested within individual regions identified an increase in functional diversity as glacier cover decreases. Community assembly models demonstrated that dispersal limitation was the dominant process underlying these patterns, although environmental filtering was also evident in highly glacierized basins. These findings indicate that predictable mechanisms govern river invertebrate community responses to decreasing glacier cover globally. ; This work was funded by the following organisations: The UK Natural Environment Research Council grants and studentships GR9/2913, NE/E003729/1, NE/E004539/1, NE/E004148/1, 20 NE/G523963/1, NER/S/A/2003/11192, and NE/L002574/1; the European Union Environment and Climate Programme Arctic and Alpine Stream Ecosystem Research (AASER) project (ENV-CT95-0164); EU-FP7 Assessing Climate impacts on the Quality and quantity of WAter (ACQWA) project (212250); Icelandic Research Council (954890095, 954890096); University of Iceland Research Fund (GMG96, GMG97, GMG98), Wyoming Center for Environmental Hydrology and Geophysics-National Science Foundation (1208909); USA-Wyoming NASA Space Grant Faculty Research Initiation (#NNX10A095H); USA-NSF Wyoming Epscor; Nationalpark Hohe Tauern, Austria; the Royal Society (International Outgoing Grant 2006/R4); the Leverhulme Trust; the Universities of Leeds, Birmingham, Iceland and Innsbruck; European Centre for Arctic Environmental Research (ARCFAC): a Research Infrastructures Action of the European Community FP6 (026129-2008- 72); the Stelvio National Park (2000-2001); the Autonomous Province of Trento (HIGHEST project, 2001-2004, del. PAT n. 1060/2001; VETTA project, 2003-2006, del. PAT n. 3402/2002); MUSE-Museo delle Scienze. We are grateful to Russell Taylor and Mike Winterbourn at the University of Canterbury, NZ, who helped to collect NZ invertebrate data and assisted with identification, and to Hakon Adalsteinsson who contributed to data collection in Iceland. Many other people, too numerous to mention, assisted with fieldwork at all of the study locations. The European Science Foundation sponsored an exploratory ┘ラヴニゲエラヮ WミデキデノWS さGノ;IキWヴ-fed rivers, hydroecology and climate change: current knowledge and future network of monitoring sites (GLAC-HYDROECO-NETぶざ デエ;デ ┘;ゲ エWノS キミ Birmingham, UK in September of 2013 where some of the ideas in this paper were first discussed ; Peer Reviewed

Este artículo contiene 13 páginas, 4 figuras, 2 tablas. ; Intermittent rivers and ephemeral streams (IRES) encompass fluvial ecosystems that eventually stop flowing and run dry at some point in space and time. During the dry phase, channels of IRES consist mainly of dry riverbeds (DRBs), prevalent yet widely unexplored ecotones between dry and wet phases that can strongly influence the biogeochemistry of fluvial networks. DRBs are often overlooked because they do not strictly belong to either domain of soil or freshwater science. Due to this dual character of DRBs, we suggest that concepts and knowledge from soil science can be used to expand the understanding of IRES biogeochemistry. Based on this idea, we propose that DRBs can be conceptually understood as early stage soils exhibiting many similarities with soils through two main forces: i) time since last sediment transport event, and ii) the development status of stabilizing structures (e.g. soil crusts and/or vascular plants). Our analysis suggests that while DRBs and soils may differ in master physical attributes (e.g. soil horizons vs fluvial sedimentary facies), they become rapidly comparable in terms of microbial communities and biogeochemical processes. We further propose that drivers of DRBs biogeochemistry are similar to those of soils and, hence, concepts and methods used in soil science are transferable to DRBs research. Finally, our paper presents future research directions to advance the knowledge of DRBs and to understand their role in the biogeochemistry of intermittent fluvial networks. ; This paper resulted from discussions conducted as part of working group 3 "Coupled Aquatic-terrestrial Biogeochemistry in IRES" based upon work from COST Action CA15113 (SMIRES, Science and Management of Intermittent rivers and Ephemeral streams; www. smires.eu) supported by COST (European Cooperation in Science and Technology). Additional support was provided for MIA by an Alexander von Humboldt Grant (Ref: 1162886) and a Juan de la Cierva Grant (Ref: FJCI-2015-26192), for CM-L by an Early Career Fellowship from the Graduate Research School (GRS) at BTU Cottbus-Senftenberg and by the French Agency for Biodiversity (ONEMA-AFB, Action 13, Colmatage, échange snappe-rivière et processus biogéochimiques), for MA by the Spanish Government (Ref: DISECO CGL-2014-55-405-R) and by a Juan de la Cierva Grant (Ref: IJCI-2015-23500), for NC by a Juan de la Cierva Grant (Ref: FJCI-2014-23064), for SB by Spanish Government (Ref: NICUS CGL-2014-55234-JIN), for RG by the Science and Technology Agency of Murcia Region (SENECA Foundation, Ref: 19525/PI/14), for OS by the SMART joint Doctorate Programme (Science for the MAnagement of Rivers and their Tidal systems, funded by the Erasmus Mundus programme of the European Union) and for Fig. 4. Conceptual framework indicating the degree of similarity in three dimensions of dry riverbeds (DRBs): physical structure, microbial community and biogeochemistry, with soils as a function of two main drivers: (T) time since the last sediment transport event, and (S) development status of stabilizing structures (e.g. biocrusts and/or vascular plants). M.I. Arce et al. Earth-Science Reviews 188 (2019) 441–453 449 DvS by the Spanish Government (Ref: CGL2016-77487-R) and Basque Government (Ref: IT951-16). Symbols for diagrams used in the art work are courtesy of the Integration and Application Network (ian.umces. edu/symbols). ; Peer reviewed