This study is part of a general project to analyse the biological and ecological mechanisms that influence the invasion of Mediterranean sand dune ecosystems by alien plants. In this paper we analyse the morphological and functional traits of coastal dune wild species (natives and aliens) based mainly on information from the literature. The most common 130 wild species occurring on the recent (Holocenic) coastal dunes were included considering the invasive status of alien plants. A comparative analysis of functional groups was performed through ordination techniques (PCoA using the Gower index). This reveals four functional groups related to the most important plant communities in coastal vegetation zonation. Alien plants were found in all functional groups and no trait or set of traits was specifically related to them. This indicates that aliens show similar traits to those natives growing in different communities of the coastal dune zonation, from the small beach annuals to the evergreen taller shrubs of the Mediterranean macchia. When the invasive status of alien species was taken into account, however, some differences emerged: a) casual aliens were found in almost all groups but their traits were not interpreted as being due to any particular adaptive strategy; b) naturalised aliens were only found in the less fluctuating habitats of the inner coastal zones; c) invasive alien species were connected with two major plant strategies: annual invasive aliens (quick-to-mature low grasses and herbs) and perennial invasive aliens (taller and often strongly clonal).
Authors:A. Stanisci, D. Lavieri, A. Acosta, and C. Blasi
Structure and diversity trends (β-diversity and species richness) across the Fagus sylvatica timberline in the central Apennines were investigated. Twenty-three belt transects were laid out across the upper forest line in the Simbruini Mountains. Number of species, plant cover, and height of different layers were recorded in each quadrat. The moving split-window method was used to detect ecological discontinuities across beech timberlines. We show how β-diversity changes along timberlines and we put forward some hypotheses about the possible dynamics of these transitions. Fourmodels resulted from the analysis of β-diversity trends: two β-diversity peaks indicated a transition where shrubs, mainly Juniperus communis ssp. alpina, (two high peaks) or beech scrub (two small peaks) formed a mantle that could allow forest expansion. One high β-diversity peak referred to an anthropo-zoogenic boundary maintained by disturbance, without the presence of a mantle. A little peak indicated a gradual transition at the upper potential timberline limit where beech forest had lost its typical floristical composition and structural characteristics.
Authors:C. Ricotta, A. Stanisci, G. C. Avena, and C. Blasi
Connectivity determines a large number of ecological functions of the landscape, including seed and animal dispersal, gene flow and disturbance propagation, and is therefore a key to understanding fluxes of matter and energy within land mosaics. Several approaches to quantifying landscape connectivity are possible. Among these, graph theory may be used to represent a landscape as a series of interconnected patches, where flows occur as a result of structural and/or functional patch connectivity. Within this context, we propose the use of a graph-theoretic index (i.e., the Harary index) as a measure of landscape connectivity. Results derived from the analysis of the vegetation map of Palmarola (central Italy) show that, from a statistical and ecological viewpoint, the Harary index may be a better measure of landscape connectivity than more traditional indices derived from transportation geography.