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More frequent and more severe forest fires mean more severely burned wood in streams. Instream wood provides habitat complexity, alters geomorphology, retains organic and inorganic material, promotes hyporheic flow and acts as substrate for biofilm and invertebrates. However, little is known about instream wood functions in fire‐prone biomes and how they combine with wood burning levels to guide postfire management efforts.Over 3 years, we tracked instream wood following forest fires in central Portugal. We examined for the first time the influence of burning level, season and a large suite of driving factors on the likelihood of four different functions having primary ecological consequences—retention of organic matter, serving as substrate for aquatic biota, being key pieces forming wood jams and deflecting flow including pool habitat formation.One of the main ecological functions of wood in rivers is to provide substrate for vegetation, periphyton, biofilm and oviposition. Our results show that this can be negatively affected when the wood is severely burned.Except for jam formation, the probability of each stream wood function changed markedly with season and the probability of non‐function was nearly twice as high in the Euro‐Mediterranean dry season than in the wet season.More anchored and decayed wood increased the probability of all functions, whereas the effect of submergence depended on the function. Challenging the 'size paradigm' that larger sized pieces provide more function, our data suggest that the effect of size is function‐specific.Synthesis and applications. We show how postfire stream restoration success can be maximized by selecting the most appropriate wood and taking advantage of attribute‐function relationships. We urge managers to refrain from removing wood or to selectively remove the most severely carbonized only, allowing the persistence of great potential to provide substrate for stream biota. The non‐attraction of severely burned wood as substrate can be compensated for by other wood with attributes enhancing this function, such as wood deeper within the bankfull area, and with large diameters. These results will help to inform successful management, as is increasingly asked from restoration ecology. [ABSTRACT FROM AUTHOR]

Characterising food‐web responses to environmental factors could greatly improve our understanding of environment‐biota relationships, and especially in floodplains where trophic interactions can be particularly important during phases of hydrological disconnection. The effects of floodplain hydrology and environmental attributes on structural aspects of biotic assemblages have been extensively studied, but responses at the functional level remain largely unknown.Here, we characterised a central aspect of food‐web architecture, the food chain length, as the maximum trophic position within 24 macroinvertebrate communities of parafluvial habitats in the Maggia river floodplain, in Switzerland. We investigated how the food chain length changed with different levels of habitat size, primary productivity and disturbance, the three factors potentially affecting food chain length in both theoretical and empirical studies.We found that food chain length was lower in frequently flooded habitats and immediately after a flood. We also showed that trophic omnivory, where predators fed at lower trophic levels after flooding, and in more frequently flooded habitats, may explain these changes.These findings show that trophic omnivory may explain how predators resist disturbance and are maintained in highly dynamic landscapes. More importantly, given that trophic omnivory may overall weaken trophic linkages and thus increase food‐web stability, this suggests that it could be a key mechanism in sustaining biodiversity in river floodplains. [ABSTRACT FROM AUTHOR]

The greater Yellowstone Area ecosystem experienced major wildfires in 1988, resulting in a substantial number of catchments being burned. We studied diatom assemblage structure at 14 sites over 5 years in catchments ranging from 0 to over 90% burned. Coefficient of variation for selected physical measures provided a good assessment of the degree of disturbance experienced by the various sites and correlated highly with percentage of catchment burned. Principal components analysis quantitatively estimated the degree of temporal change in diatom assemblages at a site. The more extensively burned catchments showed the greatest amount of structural change in diatom taxa among years. Navicula permitis Hust. and Nitzschia inconspicua Grun. were predominant in the heavily disturbed systems, whereas Achnanthes minutissima Kuetz., A. lanceolata (Breb.) Grun., Rhoicosphenia curvata (Kuetz.) Grun. ex Rabh., and Diatoma hiemale var. mesodon (Ehr.) Grun. were common in less disturbed streams. The results demonstrate that recovery trajectories of lotic diatom assemblages following major landscape-scale disturbances are a function of disturbance intensity resulting from differences in catchment characteristics. [ABSTRACT FROM AUTHOR]

Rivers regulated by dams display several ecosystem alterations due to modified flow and sediment regimes. Downstream from a dam, ecosystem degradation occurs because of reduced disturbance, mostly derived from limitations on flow variability and sediment supply. In the last decade, most flow restoration/dam impact mitigation was oriented towards the development of environmental flows. Flow variability (and consequent disturbance) can be reintroduced by releasing artificial high flows (experimental floods). Flow-sediment interactions during experimental floods represent strong ecosystem drivers, influencing nutrient dynamics, and metabolic and functional properties. In river networks, sediment and water inputs from tributaries generate points of discontinuity that can drive major changes in environmental conditions, affecting habitat structure and determining functional differences between upstream and downstream. However, despite the relevance for management, flow/sediment relations during environmental flows − and more importantly during experimental floods − remain poorly understood, mostly due to the lack of empirical evidence. In this study, we examined how a major tributary (source of water and sediments) modified the physical habitat template of a regulated river, thereby influencing ecological and geomorphological responses to experimental floods. Methods combined high-resolution drone mapping techniques with a wide range of biological samples collected in field surveys before, during, and after experimental floods in an alpine river. Data were used to quantify changes in relevant functional and structural ecosystem properties, relating ecological responses to geomorphological dynamics. Results highlight the importance of tributaries in restoring ecosystem properties lost after damming, enhancing the resilience of the system. In addition, we observed that disturbance legacy played a fundamental role in determining ecological conditions of a river prior to experimental floods, thus confirming that considering flow variability and sediment availability is crucial in adaptive dam management and environmental flows design. • Experimental floods mitigate dam impacts restoring flow variability and disturbance. • Sediment supply and disturbance legacy shape eco-morphological responses to floods. • Tributaries can modify the effect of experimental floods on ecosystem properties. [ABSTRACT FROM AUTHOR]