1,721,022 research outputs found
Floristic, phenological and chorological differences in the annual vegetation of Sardinia.
No full textThe therophytic flora of Sardinia has been split into four main groups, basing on the ecologic requirements of species. The following groups have been recognized: flora of dry entisoils, flora of periodically swampy or submerged entisoils, flora of coastal sites, flora of fields, road edges and human settlements. Either, most frequent or exclusive species were ascribed to each group. A species was considered “exclusive” when its relative frequency outside a given group was estimated ≤10%. Differences have been highlighted within the groups, dealing with chorology, growth form, flowering time, colour of flowers, pollination and seed dispersal strategies
A stochastic model of seed dispersal pattern to assess seed predation by ants in annual dry grasslands
No full textA combined field experiment and modelling approach has been used to provide evidence that ants may be responsible for an observed lower patchiness and higher plant diversity in the neighbourhood of ant nests, within Mediterranean dry grasslands belonging to the phytosociological class Tuberarietea guttatae. The hypothesis was that seeds occurring in clumps may have an higher probability to be harvested than seeds having a scattered distribution. In order to test this hypothesis, four analysis steps have been performed. First, the seed productivity and dispersal pattern was recorded for four plant species found, either more abundant beside the ant nests (Tuberaria guttata, Euphorbia exigua) or away from the ant nests (Bromus scoparius and Plantago bellardi). Second, a stochastic model was developed to simulate the observed dispersal patterns of each studied species. Third, ten seed arranges in accordance to the distribution patterns created by the model were offered to the ants and the positions of the predated seeds was recorded. Finally, the observed pattern of seed predation was matched to models performed by different distributions of probability. Results confirmed the initial hypothesis, showing that the probability of being predated decreases with the increase of the reciprocal distance of seeds. It was concluded that the preference of ants for high concentrations of food items holds down the dominant species sufficiently to allow the subordinates to survive. The observed higher frequency of small-seeded, small-sized, or creeping therophytes close to the ant nests can be therefore seen as an example of indirect mirmecophily
Plant-ant interaction in xerophilous ephemeral vegetation of S.E. Sardinia.
No full textFrequency and abundance of annual plants have been measured in 40 square plots, 0.36 m2 each, settled in an area of approximately 5 ha at the foothill of the Sarrabus massif, in S.E. Sardinia. 20 plots were randomly distributed at less than 5 m from the ant nests, further 20 at more than 30 m from the ants nests. The results showed a significantly lower plant density next to the ant nests, together with an higher species richness. Far from the nests, plots resulted dominated by relatively few species with a patchy distribution, while next to the nests the distribution of frequencies resulted more homogeneous. It is suggested that harvesting ants may contribute to the small-scale regulation of frequency and abundance of annual species and therefore contrast the natural tendency towards increasing the spatial order (and reducing the plant diversity) by the formation of patches. Being ants nests more frequent on secondary vegetation linked to a slight grazing-pressure, such traditional land-use might benefit indirectly the spatial heterogeneity and diversity of plant communities dominated by annuals
Nuovi dati morfologici, ecologici, distributivi e comportamento fitosociologico di Linaria arcusangeli Atzei & Camarda
No full textThe present study has permitted us to describe more precisely, the morphological characters, the ecology and phenology by Linaria arcusangeli Atzei et Camarda. Ten new stations have been individualized, thus better defining the area of distribution of the species and typifying a new association and subassociation endemic to Southern Sardini
Contribution to the knowledge of the therophytic flora of Sardinia
No full textThe abundance of therophytes, largely contributes to the naturalistic value of Sardinia. Moreover, most of the annual species belonging to the Sardinian flora have an historical and cultural value, as they followed the men in his migrations and still reflect the different ways of traditional land exploitation characterising the island. As a matter of fact, the development of human technology increased number and frequency of the annual plants of Sardinia.
Nowadays, annuals occur in several habitats of the island, where they play a primary ecological role, both as biomass producers and protecting the soil from rill erosion during the rainy season, at least where the environmental factors do not let a thick layer of perennial plants.
In the frame of a research about the ephemeral flora and vegetation of Sardinia, an updated checklist of the annual plant occurring on the island will be presented. The list is based on the available bibliography, integrated with data collected in the field.
Synthetic diagrams dealing with chorology, growth form, dispersal strategies, blooming period and anthesic colour of the Sardinian annual plants will be related both to the Italian flora and to the following phytosociological classes: Tuberarietea guttatae, Saginetea maritimae, Cakiletea maritimae, Thero-Suaedetea, Isoeto-Nanojuncetea, Polygono arenastri-Poetea annuae, Stellarietea mediae
Aggiornamento lista bibliografica (Sardegna). In: AA.VV. – Lista bibliografica (1994-1999)
No full textAggiornamento lista bibliografia (Sardegna). In: AA.VV. - Lista bibliografica (1994-1999)
No full textStudio fitosociologico delle cenosi a Carex microcarpa Bertol. ex Moris della Sardegna meridionale
Full text linkPhytosociological study on Carex microcarpa Bertol. ex Moris communities in southern Sardinia (Italy). Results of a phytosociological study on
Carex microcarpa Bertol. ex Moris communities in southern Sardinia (Italy), are herein presented. For the vegetation analysis ten phytosociological
relevés, five soil profiles and a bioclimatic analysis on thermopluviometric stations present in Sulcis-Iglesiente and Sarrabus-Gerrei regions, were
carried out. All data were elaborated and subsequently submitted to multivariate statistical analysis. This permitted to recognize two principal groups
that correspond with to two different subassociations which are vicarious in relation to the substrate and its physical chemistry features. All relevés
are referable to the Hyperico hircini-Caricetum microcarpae ass. nova. In particular those of the former group belong to the typical subassociation
oenanthetosum crocatae subass. nova. and those of the second one to adiantetosum capilli-veneris subass. nova. The typical subassociation develops
on deep, very rich in humus, from subalkaline to neutral and with limited slope soils. The adiantetosum capilli-veneris subassociation develops on
very wet substrate, it is characteristic of dripping rocks and spring areas. The communities are syntaxonomically related to the Sardo-Corsican
endemic alliance Caricion microcarpae
Note sul genere Helichrysum Miller (Asteraceae) in Sardegna
No full textTaxonomical remarks on the genus Helichrysum Miller (Asteraceae) in Sardinia – On the basis of field work
and herbarium investigation, a taxonomical study about the genus Helichrysum in Sardinia, including ecologic and chorological
considerations, was carried out. The following taxa resulted to be present on the island: H. saxatile ssp. saxatile, an
endemic chasmophyte circumscribed to the calcareous massifs of CE Sardinia; H. saxatile ssp. morisianum ssp. nov.,
endemism localized in some rocky places of S Sardinia; H. italicum ssp. italicum, a widely distributed Tyrrhenian element,
in Sardinia only occurring on some mountains places; H. italicum ssp. pseudolitoreum, a C Mediterranean chasmophyte,
localized in the calcareous cliffs of the SW Sardinia; H. italicum ssp. microphyllum, a subspecies distributed in Crete,
Sardinia, Corsica and Balearic Islands, widely ranging in Sardinia from the sea level to the highest peaks, on all kind of
soils; H. frigidum, endemic to Sardinia and Corsica, widespread on the granitic Corsican massifs, but in Sardinia only
found on Mount Limbara, according to old herbarium specimens never reasserted in recent times; H. montelinasanum, a
chasmophyte allied to the previous one and exclusive on some siliceous mountains of SW Sardinia
- …
