Gradients of salinity and plant community richness and diversity in two different Mediterranean coastal ecosystems in NW Sardinia.

Alfredo Maccioni,Valeria Cubeddu,Elisabetta Cucca,Simone Dessena,Bachisio Mario Padedda,Rossella Filigheddu,Luisa Canopoli,Samuele Morittu,Emmanuele Farris

doi:10.3897/bdj.9.e71247

Abstract

This study aimed to test if differences in soil salinity, plant richness and diversity were significantly affected by habitat, site and distance from the seashore at three sandy and three rocky coastal sites in north-western Sardinia.Each site has been divided into three belts placed at an equal distance of 50 m from the shoreline. We measured soil salinity using a probe and vascular plants richness and diversity using linear transects at all sites. Average soil salinity varied from 0.115 g/l to 0.180 g/l; it was higher in the rocky habitats than in the sandy ones. A total of 21 species were found per transect/site at the rocky sites and 30 species per transect/site at the sandy sites, with an average of Shannon and Weaver's Diversity Index of 1.8 per each belt at each site. These data confirm that, also in the Mediterranean islands, there are coastal gradients of soil salinity from the seashore to inland areas and that also vascular plant richness and diversity are influenced by the distance from the sea. Soil salinity was strongly affected by the type of habitat, being average at the rocky coasts and negligible at the sandy shores. The site effect was not significant for both soil salinity and plant richness and diversity.

Highlights

Studies on the effects of biotic and abiotic factors on biodiversity are a central topic in plant ecology (Klanderud et al 2015)
The majority of contributions on soil salinity in Mediterranean coastal environments have dealt with laboratory measurements of conductivity on soil samples collected mainly on dunes (Molina et al 2003, Carboni et al 2011, Angiolini et al 2013, Fenu et al 2013, Ruocco et al 2014,Ciccarelli et al 2016, Cusseddu et al 2016), whereas in this research, we present a contribution, based on in situ measurements
Species number and biodiversity index follows an opposite trend with respect to soil salinity, both being higher at the vegetation belt more distant from the seashore, where soil salinity is lower

Summary

Introduction

Studies on the effects of biotic and abiotic factors on biodiversity are a central topic in plant ecology (Klanderud et al 2015). Several studies have investigated the responses of vascular plant species to burial and salt spray in sandy environments (Donnelly and Pammenter 1983, Rozema et al 1985, Maun and Perumal 1999, Wilson and Sykes 1999, Owen et al 2004, Gormally and Donovan 2010), identifying them as the most important factors for determining environmental gradients on coastal dunes (Maun and Perumal 1999, Gormally and Donovan 2010) and controlling the zonation of psammophilous vegetation (Griffiths 2006, Lane et al 2008, Fenu et al 2013). Biotic interactions (Farris et al 2017), disturbance (Blondel 2006) and historical and geographical factors (Thompson 2020) should be considered

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