A Proposed Framework for the Identification of Habitat Utilisation Patterns of Macrophytes in River Po Catchment Basin Lakes (Italy)

Abstract

The main aim of this study, which is based on cover-abundance values of 20 species of floating-leaved and submersed macrophytes collected in 18 lakes located within the River Po catchment basin (Italy), is to investigate the relationships between lake-scale environmental features (including morphology, hydrology, trophic state and water quality variables) and the changes in species composition and species richness in macrophyte communities. The findings reveal that the main changes in community composition of the pondweed communities, identified by principal component analysis, could be effectively explained by a newly introduced morpho-hydrological parameter (the theoretical laminar water renewal rate – R L) and by the trophic state of the lakes, expressed as Carlson’s trophic state index (TSI). The results of the multivariate analyses performed also show that the grouping of species is strictly related to growth-form traits. In particular, floating-leaved and submerged macrophytes appeared mutually exclusive in dominating different habitat types defined on the basis of the R L–TSI framework. An increasing trend in species richness was also observed in relation to R L. The possibility of using the bivariate R L–TSI framework for the identification of habitat utilisation patterns by single species was also investigated, and cover-abundance prediction maps based on the R L–TSI framework were produced for several macrophyte species. Observations in another system characterised by high spatial heterogeneity for hydrological and trophic conditions, support the predictions in terms of growth-form prevalence, species richness and single species cover-abundance (where available), and also suggest a more refined application of the proposed approach.