Preface: physical template and river ecosystem functioning: interdisciplinary feedbacks for improving rivers

Abstract

This special issue in Hydrobiologia comprises papers that were presented in 2011 during an oral and a poster session at the 7th Symposium for European Freshwater Sciences (SEFS) in Girona, Spain, entitled ‘Form and function: channel morphology, hydraulic integrity and river ecosystem functioning’, as well as selected articles on recent aspects of the subject. The aim of this session was to promote communication between hydrologists, geomorphologists and ecologists to improve the understanding of river forms and processes and associated ecosystems on the one hand, and to provide knowledge on river restoration as well as on benefiting ecosystem services on the other. River ecosystems depend on the dynamic interplay between flow and channel morphology, which together set the physical template for fluvial communities, and ultimately for ecosystem functioning (Elosegi et al., 2010). There is still a need for research on the significance of hydromorphology on riverine communities, notably in terms of responses to restoration actions (Palmer et al., 2010). Further, research is needed on the effect of channel morphology and hydraulics on ecosystem functions, such as the transformation of organic matter or the maintenance of water quality, which are the basis for ecosystem services and of key importance for the human society (Palmer & Febria, 2012). Most river ecosystem functions are actually provided by coupled processes, which relate to river form on a wide range of temporal and spatial scales (Malard et al., 2002). Hence, focusing on ecosystem functions opens the perspective of hydromorphological integrity from a set of standard variables that are commonly assessed in river restoration and monitoring to a complex set of interacting multiple environmental drivers on these ranges of scales. River scientists are today equipped with a large toolkit of techniques, ideas and approaches to link hydromorphology with river functioning and ecosystem services, which should be regarded in assessment, management and restoration of riverine ecosystems. Rivers change over time, owing to a set of human drivers (e.g., embankment, damming, landuse change, discharge regulation...) (Kondolf & Piegay, 2003; Brierley & Fryirs, 2005), such that their biological Guest editors: A. Elosegi, M. Mutz & H. Piegay / Form and function: channel form, hydraulic integrity, and river ecosystem functioning