Six decades of changes in the riparian corridor of a Mediterranean river: a synthetic analysis based on historical data sources

Abstract

(2012). Six decades of changes in the riparian corridor of a Mediterranean river: A synthetic analysis based on historical data sources. Ecohydrology, 6 (4): 536¿553. doi:10.1002/eco.1330.1 This is a pre-copyedited, author-produced PDF version following peer review of the article: Garófano-Gómez, V., F. Martínez-Capel, W. Bertoldi, A. Gurnell, J. Estornell, F. Segura-Beltrán. 2013 ABSTRACTRiparian corridors in semi-arid Mediterranean environments are ecosystems of high biodiversity and complexity. However, they are threatened because of high levels of human intervention. River damming and related flow manipulation is considered as one of the most prominent human impacts on riparian corridors. This study combines historical time series information on river flows and their human manipulation, historical aerial images depicting changes in riparian land cover and ground observations of the species -age composition and morphology of the riparian corridor of a Mediterranean river (the Mijares River, Eastern Spain) over the last 60 years. In this sense, we explored how to integrate information from a wide variety of data sources, and we extracted a variety of indices and undertook analyses that identified and summarized spatio-temporal changes in riparian structure and in the driving flow processes.Results revealed an increase in the cover and density of woody vegetation and a decrease in bare sediment areas (essential for recruitment of riparian pioneer species), with a synchronous reduction in the complexity of the riparian corridor of the middle reaches of the Mijares River. These vegetation changes have accompanied a decrease in the magnitude and variability of river flows over the last six decades, with higher severity since dam closure. This study illustrates the effectiveness of combining disparate historical data sources and the effectiveness of processing these sources to extract informative metrics that can improve the understanding and management of riparian systems.

The abundance and distribution of guilds of riparian woody plants change in response to land use and flow regulation

“…Many responses of riparian communities to regulation of flows and water levels have been identified world‐wide (Greet, Cousens, & Webb, ; Johnson & Waller, ; Nilsson & Berggren, ), including vegetation encroachment, interruptions of natural regeneration, senescence of forests, increasing stress and disease‐induced mortality, reduced growth rate, altered recruitment, failure of seedling establishment, longitudinal and lateral fragmentation (Belmar, Bruno, Martínez‐Capel, Barquín, & Velasco, ; Garófano‐Gómez et al., ; González, González‐Sanchís, Cabezas, Comín, & Muller, ; González, González‐Sanchis, Comín, & Muller, ), and shifts in the composition and diversity of riparian vegetation (Bejarano, Nilsson, González del Tánago, & Marchamalo, ; Rood, Braatne, & Goater, ; Webb et al., ). The responses to altered flows of the riparian ecosystems remain a long‐standing challenge in Mediterranean regions (Belmar et al., ; Dallas, ; Garófano‐Gómez et al., ), likely a result of the multiple external pressures that influence these ecosystems, either directly or indirectly.…”

“…Our understanding of the functioning of riparian ecosystems in hydropower rivers is still limited. Several studies have shed light on the spatio‐temporal changes in dammed rivers within the novel hydrogeomorphological environments (Aguiar, Martins, Silva, & Fernandes, ; Garófano‐Gómez et al., ; Gurnell, Bertoldi, & Corenblit, ), whereas others have shown the effects of water diversion on channel geometry and riparian plant community composition and diversity (Caskey et al., ). Besides the alteration of timing, quantity, quality and predictability of flows due to damming, riparian forests are stressed by intensive land use pressures, particularly in the Mediterranean Europe (Clerici, Paracchini, & Maes, ; Dufour, Rinaldi, Piégay, & Michalon, ; Santos, ).…”

Evidence of increase in woody vegetation in a river corridor, Northwest England, 1984–2007

“…Methods for mapping and analysing channel changes have been widely developed and applied (Garófano-Gómez et al, 2013;Gurnell, 1997;Hooke, 1984;Hooke & Yorke, 2010). Likewise, vegetation changes have been studied both in riverine and other environments, many studies using satellite imagery (Bertoldi, Drake, & Gurnell, 2011) but many, especially on decadal timescales, have used aerial photographs, as here (Dixon & Johnson, 1999;Garófano-Gómez et al, 2013;Gonzalez, Gonzalez-Sanchis, Cabezas, Comin, & Muller, 2010;Kondolf, Piegay, & Landon, 2007;Lunt, Winsemius, McDonald, Morgan, & Dehaan, 2010;Yang & Tien, 2010).…”

“…Likewise, vegetation changes have been studied both in riverine and other environments, many studies using satellite imagery (Bertoldi, Drake, & Gurnell, 2011) but many, especially on decadal timescales, have used aerial photographs, as here (Dixon & Johnson, 1999;Garófano-Gómez et al, 2013;Gonzalez, Gonzalez-Sanchis, Cabezas, Comin, & Muller, 2010;Kondolf, Piegay, & Landon, 2007;Lunt, Winsemius, McDonald, Morgan, & Dehaan, 2010;Yang & Tien, 2010). Increases in woody riparian area have been found but many of the cases are associated with change in river regime (Dixon & Johnson, 1999;Johnson, 1994;Perona, Molnar, Savina, & Burlando, 2009), especially due to dam control (Dixon, Johnson, Scott, Bowen, & Rabbe, 2012;Gonzalez et al, 2010;Merritt & Cooper, 2000).…”

Channel forms and vegetation adjustment to damming in a Mediterranean gravel‐bed river (Serpis River, Spain)

“…These vegetation communities were not yet present (or did not have adult form) in the 1994 aerial photograph but appeared clearly consolidated in the 2000 image, after a long period without floods (1993–2001) that could have favoured vegetation development at the flowing channel banks. In another river of the region affected by damming, the Mijares River, Garófano‐Gómez et al () observed a period of the same duration (40 years) between reservoir construction and the completion of the process of encroachment of dense woody vegetation, whereas Martínez‐Fernández et al () have identified a similar stage of stability between 2000 and 2015 in Northwestern Spain.…”