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A guide to the vascular plants
of the temporary ponds of Sardinia (Italy)

Pier Luigi Nimis, Simonetta Bagella, Maria Carmela Caria, Rossella Filigheddu, Andrea Moro, Elena Pittao, Stefano Martellos
Images by Andrea Moro

The Mediterranean temporary ponds are small bodies of freshwater which are fed almost exclusively by rain, and hence ephemeral and highly dependent on annual rainfall. Under these unstable and unpredictable conditions a unique and highly specialized flora is developed, that includes many rare species of conservation interest, also called 'dwarf flora' to emphasize the small size of the species. The dominant species are annual plants with a short life cycle, able to bloom and fruit even within a few weeks after germination; they also produce many seeds that germinate in an opportunistic way, ensuring the survival of the species during particularly dry years. Important are also several slow-growing and stress-tolerant geophytes (eg. Isoetes sp. pl.). Along with this highly specialized flora, temporary ponds are also home to more generalist, terrestrial opportunistic species, that mainly appear in the peripheral areas and spread to the central area during dry periods.
The Mediterranean temporary ponds are habitats of high biological and biogeographical interest. The Habitat Directive recognizes them as Habitats of Community Interest, included in the group of freshwater stagnant vegetation with the codes 3120, 3130 and 3170 *.
In Sardinia, the Mediterranean temporary ponds, locally referred to as paulis and pischinas, are mainly located in the plateaus and in the lowlands at altitudes ranging from 10 and 1200 m, in bioclimatic conditions which vary from the meso-Mediterranean belt (mean annual temperature: 15°C, annual precipitation: 946 mm) to the temperate-sub-Mediterranean belt (mean annual temperature: 10°C, annual precipitation 1000 mm). They occupy small depressions on hydromorphic soils and on impermeable bedrock with poor drainage (eg. granite). The maximum depth of the water varies in relation to the morphology of the substrate, and often it is possible to recognize a zonation of vegetation into three belts: an external belt, an intermediate belt and a central belt.
The surrounding vegetation is diversified in relation to the type of substrate: neutro-acidophilous forests with cork oak (Quercus suber), often converted into wooded pastures, on the plateaus; oak forests dominated by the deciduous oak of Sardinia (Q. ichnusae) on siliceous substrates in central-northern Sardinia; mixed-mesophilous evergreen forests (Q. suber, Q. ilex) in lowland areas. The use of these habitats is characterized by extensive agro-pastoral activities that contribute to their conservation by controlling the colonization of trees and shrubs.
The list of plants included into this identification tool was created in the framework of the project 'Vascular plants, bryophytes and aquatic fauna of the Mediterranean temporary ponds of Sardinia: biodiversity, ecology and conservation. - Acronym: Paulis', funded by the Region of Sardinia - Regional Law 7 August 2007, n. 7: 'Promotion of scientific research and technological innovation in Sardinia'.
The field surveys were integrated with literature data and with information deriving from herbarium specimens of the University of Cagliari (CAG), Florence (FI), Sassari (SS and SASSA) and Torino (TO). The list includes all entities which were hitherto found in the temporary ponds of Sardinia, including xerophilous herbaceous plants and some woody plants that colonize these habitats especially in areas that are no longer used for extensive agro-pastoral activities.

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