Using Multivariate Analyses to Assess Effects of Fluvial Type on Plant Species Distribution in a Mediterranean River

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 SPecies ANalysis, and partial ordinations all suggested that fluvial types were characterized by well-defined indicator species. The differences found by Redundancy Analysis and nonparametric 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.

Assessment of flora diversity in a minor river valley using ecological indicator values, Geographical Information Systems and Digital Elevation Models

“…In many regions, riparian landscapes constitute a rather small proportion of the total watershed area, but they play a prominent ecological role [3,4,[7][8][9][10][11]13,14,19,31].…”

“…phytosociological releves [20,22,26,41, and the present study]. Multivariate statistics [24,25] have become a useful tool for detection of patterns of vascular species richness and distribution of their ecological groups on the background of primary and secondary topographic attributes of a given terrain, including riparian landscapes [9,10,22,[26][27][28].…”

“…Habitat complexes of river valleys are characterized by considerable heterogeneity defined as variability of spatial and temporal patterns and processes [2]. Environmental heterogeneity of the riparian landscape is a result of river fluvial activity (erosion, transport, sedimentation), organic-matter dynamics, climatic factors, and hydrological relationships between all abiotic and biotic environmental elements [3][4][5][6][7][8][9][10]. The vegetation landscape of the river valley is characterized by specific zonal toposequence of plant communities [6,9,11].…”

“…Environmental heterogeneity of the riparian landscape is a result of river fluvial activity (erosion, transport, sedimentation), organic-matter dynamics, climatic factors, and hydrological relationships between all abiotic and biotic environmental elements [3][4][5][6][7][8][9][10]. The vegetation landscape of the river valley is characterized by specific zonal toposequence of plant communities [6,9,11]. Biodiversity of river systems may be considered at various levels of organization -from the physicogeographical region to the habitat patch, i.e., from the macro-to nanoscale [3,[11][12][13][14].…”

“…DEM derivatives related to species occurrence [22] and vegetation diversity [23] are also analyzed. Multivariate canonical analyses are currently in common use for identifying repeatable patterns in species distribution in terms of environmental factors [9,22,[24][25][26][27][28].…”