ARTICLE Using Multivariate Analyses to Assess Effects of Fluvial Type on Plant Species Distribution in a Mediterranean River Claudia Angiolini & Alessia Nucci & Flavio Frignani & Marco Landi Received: 12 April 2010 / Accepted: 1 November 2010 / Published online: 12 January 2011 # Society of Wetland Scientists 2011 Abstract We propose a method to assess the distribution of plant assemblages along rivers delimiting homogeneous fluvial types using cluster analysis applied to morphological features, quantified with aerial photos and geographic information system software. A stratified random sampling design along the elevational gradient was used to analyze riparian plant species. Multivariate statistics were applied to detect patterns of variation in the species data, and among functional and ecological groups. Cluster analysis identified four fluvial types: headwater, low sinuosity, braided, and incised. Canonical Correspondence Analysis, INdicator SPe- cies ANalysis, and partial ordinations all suggested that fluvial types were characterized by well-defined indicator species. The differences found by Redundancy Analysis and non- parametric analysis of variance for functional and ecological groups also supported the fluvial type division, showing different distributional trends for annual and woody species, and the greatest ecological distance between braided and headwater types. Based on the ordination results, dividing fluvial types according to morphological features was justified by environmental and floristic differences, although plant species variability was only partially described. Our results illustrated that the fluvial type classification created using this methodology was consistent with natural plant species distribution patterns. Keywords Ellenberg indicator values . Floristic assemblages . Functional groups . Morphology . Riparian vegetation . River classification Introduction In many regions, riparian areas constitute a small propor- tion of the total watershed area, yet they play a prominent ecological role. They are important pathways and migration corridors for the flow of energy, matter, and organisms across the landscape, and act as ecotones between terrestrial and aquatic zones (Malanson 1993; Forman 1997). More- over, riparian habitats are considered hotspots of biodiver- sity (Dècamps and Tabacchi 1994; Dudgeon et al. 2006). Unfortunately, streams and rivers throughout the world have been degraded by human activities (Baattrup-Pedersen et al. 2005). Mediterranean rivers, in particular, have a long history of human disturbances at basin and corridor scales (Di Castri 1991; Aguiar and Ferreira 2005). Given the magnitude of past loss and conversion of floodplains, as well as on-going threats, we should better understand how best to conserve remnant habitats. Rapid assessment of plant species diversity and distribution along rivers would be useful (Stohlgren et al. 1997), but resources or expertise to quantify total biodiversity of an area are lacking (Pharo et al. 1999; Hermy and Cornelis 2000). Determining the main factors influencing plant species distribution in riparian areas has become a priority. Recent studies revealed river morphology to be a strong determinant of riparian ecosystem function. Reviews by Steiger et al. (2005) and Corenblit et al. (2007) establish how landforms and physical processes drive the dynamics of biological communities. Strong linkages exist among watershed morphometry, stream hydro-geomorphology, and C. Angiolini : F. Frignani : M. Landi Department of Environmental Sciences “G. Sarfatti”, University of Siena, P.A. Mattioli 4, 53100 Siena, Italy A. Nucci (*) Department of Botany, University of Cagliari, Viale Sant’Ignazio da Laconi 13, 09123 Cagliari, Italy e-mail: ale.nucci@gmail.com Wetlands (2011) 31:167–177 DOI 10.1007/s13157-010-0118-7