4,180 research outputs found
Influence of some geomorphological and vegetational features of river terraces on cover and density of Santolina etrusca (Lacaita) Marchi et D’Amato
No full textThe relationship between density and cover of Santolina etrusca, a plant species endemic to central Italy, and some ecological and geomorphological features of river terraces were studied by univariate and multivariate analysis. The results showed that S. etrusca achieves maximum density and cover on the second river terrace occasionally disturbed by flooding and with chamaephytic vegetation. On the first terrace its distribution is limited by frequent flooding and on the third by competition. Since S. etrusca grows on all the terraces considered in this study, it is a poor indicator of the gradient of disturbance due to flooding. It is not highly adapted to disturbance by flooding nor to competition ; nor is it potentially dominant if undisturbed.Nous avons étudié par analyses statistiques univariées et multivariées la relation entre la densité et le recouvrement de Santolina etrusca, plante endémique du centre de l’Italie et quelques caractéristiques écologiques et géomorphologiques des terrasses fluviales. Il résulte de l’analyse que S. etrusca présente les valeurs maximales de densité et de recouvrement sur la deuxième terrasse fluviale, perturbée sporadiquement par les crues et avec une végétation de garrigue. Sur la première terrasse, la densité de l'espèce est réduite par les fréquentes crues, alors que sur la troisième terrasse cette densité est réduite par la plus grande compétition interspécifique. S. etrusca pousse donc dans toutes les terrasses étudiées et elle n’est pas une indicatrice valable de l’impact des crues. En outre, cette espèce ne semble ni très adaptée à ce type de perturbation, ni compétitive quand les perturbations cessent.Angiolini Claudia, De Dominicis Vincenzo. Influence of some geomorphological and vegetation features of river terraces on cover and density of Santolina etrusca (Lacaita) Marchi & d’Amato. In: Ecologia mediterranea, tome 24 n°1, 1998. pp. 33-41
Soil-Plant Relationships in Mediterranean Salt Marshes across Dune-Cultivated Land Gradient
No full textThe relationships between soil factors and plant species were investigated in salt marshes on the west coast of central Italy along a dune-cultivated land gradient with similar topographic elevations. Plant community composition was quantified in three zones (marsh-dune border, central marsh, and marsh-cultivated land border) identified across the gradient. The results suggest that the distribution and variation in abundance "performance" of plant species is mainly ruled by salinity and soil texture gradients (from sandy to silt-clay). Texture seemed to affect vegetation zonation in the marshes near sand dunes, since at the marsh-dune border the percentage of wind-blown sand increases. Variations in field capacity, total organic carbon, pH, and calcium carbonate did not appear to control the performance of plant species. Indications on the performance of six species are provided. Limbarda crithmoides increased with the amount of sand and was often located at the marsh-dune border. Elymus repens and Phragmites australis increased with decreasing salinity and were frequently found at marsh borders, however E. repens also increased with the amount of silt-clay. Sarcocornia fruticosa increased with salinity and silt-clay, while Halimione portulacoides increased with salinity and seemed less subject to changes in soil texture. Elymus pycnanthus increased with salinity and decreased with the amount of silt-clay, however, the ordination suggested that other factors may be determinant for this species. These species could be useful to map saline environments and to reconstruct an appropriate scenario in restoration projects of Mediterranean salt marshes
The vegetation gradient along the longitudinal profile of a braided stream: a case study in central Italy
No full textThe aim of this study was to evaluate the importance of the variation of environmental variables (geomorphological, topographical and climatic factors) along the lon gitudinal profile of a braided stream for the distribution of plant species and communities at a local scale. This was achieved by means of a case study in central Italy. Vegetation data from the river bed were grouped according to floristic and ecological affinities as follows: semi aquatic, helophytic, hygrophilous pioneer grasses, synantropical grasses, mesohygrophilous and pioneer grasses, garigues, hygrophilous shrubs, thermophilous shrubs, xerothermophilous shrubs and grasses, hygrophilous forest and thermophilous forest. A clear division between herbaceous and woody communities was observed along the first DCA axis and was inter preted as a transversal gradient of the stream due to decreasing flooding. Canonical Correspon dence Analysis suggested that altitude, distance from sea and bed width are the most important environmental variables explaining community distribution along the longitudinal profile. However, on this local scale, partial CCA showed that the abiotic variables explained 49.6% of the species data variation. This result, together with the lack of a correlation between environ mental factors and DCA axes 1 and 2, suggests that factors other than those included in the analysis, and probably only marginally linked to the longitudinal gradient, influenced the dis tribution of communities as well. On a local scale, we observed that there was no variation in the floristic composition of the coenoses along the longitudinal gradient. Consequently there is no vicariance of communities in terms of climate and/or biogeographic region. Along the longitudinal profile we found, however, the presence of coenoses that were ecologically (hard wood and soft wood) or structurally (dominance of woods, garigues, or pioneer coenoses) different in terms of geomorphological and topographical variables
Vegetation of stream-bed garigues in the antiapennine range of Tuscany and Latium (central Italy), especially the new association Santolino etruscae-Saturejetum montanae
No full textThe authors describe the prevalently chamaephytic vegetation found on terraces of fluvial origin along water courses in the Antiapennine range of Tuscany and Latium (Provinces of Siena, Grosseto and Viterbo) on stable or rarely disturbed sandy-pebbly alluvium. This vegetation is of the primary type, characterized principally by Santolina etrusca, Satureja montana, Teucrium montanum, Helichrysum italicum, Linum tenuifolium and Bromus erectus, strongly determined by soil and closely related to the geomorphological and hydrological features of the station. The syntaxonomic, synecological and syndynamic setting of this vegetation is discussed by comparison with similar types described in other places. A new association, Santolino etruscae-Saturejetum montanae, is proposed. It is temporarily collocated in the alliance Xerobromion (Festuco-Brometea), and has at least two subassociations: the first, saturejetosum, on consolidated material hardly ever subject to disturbance by flooding; the second, inuletosum, on wider, occasionally disturbed terraces. Contact vegetation, linked to the different ecological conditions occurring in these biotopes, is briefly described
Mulino di Tifo wetland: One biotope of notable botanical interest in Val di Farma (Siena, southern Tuscany) [L'area umida del Mulino di Tifo: un biotopo di notevole interesse botanico in Val di Farma (Siena, Toscana meridionale)]
No full textAuthors describe the swampy resurgent zone of Mulino di Tifo in Val di Farma, a limited size area, recently discovered, but very interesting from botanical point of view. The vegetational analisys has been carried out through phytosociological relevés referred to different syntaxonomical units. The analisys was mainly focused on the most important hydrohygrophilous vegetational type, paying particular attention to priority habitats (Cladietum marisci) and environments of community interest (herbaceous coenoses of Isoëto-Nanojuncetea and of Bidentetea and woods of Alnetea glutinosae). In the biotope there are some species rare in Tuscany and in the most part of the italian peninsula such as Cladium mariscus, Thelypteris palustris and Osmunda regalis. The floristical research is summarized in the list and in the biological and chorological spectrum. The survey has been integrated with some comments and indications for the conservation of this wetland. © 2018 Società Botanica Italiana onlus
Ecological responses of Osmunda regalis to forest Canopy cover and Grazing
No full textABSTRACT.—The density and frond traits of the dimorphic fern Osmunda regalis were examined in
45 populations situated in central Italy, along a gradient of forest canopy cover and deer grazing.
The survey involved 1704 ramets containing 6416 fronds, of which 5643 were sterile and 773
fertile. Within the ramets, the number of fertile fronds increased with the number of sterile fronds
and with the mean height of ramets. Light seemed to promote fertility, as the number of fertile
fronds decreased with increasing canopy cover. Fewer and smaller fronds were found in plots with
high forest canopy cover. Our results showed that O. regalis performed best in conditions of full
sunlight but can persist and recruit young sporophytes under closed canopy. As many marsh and
lake environments have disappeared or been altered by human activity, more populations were
located under high canopy cover in the forest than in open habitats. Deer grazing caused a
significant decrease in fertile fronds, in total frond area and in ramet height, but the number of
ramets and sterile fronds were unaffected. In conclusion, plant density and frond traits of O. regalis
responded differently to the availability of light and to grazing
Population Structure of Osmunda regalis in Relation to Environment and Vegetation: An Example in the Mediterranean Area
No full textThe structure of 42 natural populations of the endangered fern Osmunda regalis was studied at the southern limit of its European distribution. The aims were to i) investigate the population structures and status of the species; ii) test which local habitat and population characteristics correlate with the different population structures in the Mediterranean area; iii) evaluate which habitat types are suitable to support viable populations. The structure of populations is determined by the attribution of different stages of development of the sporophyte. This study documented the life-stage structure of O. regalis using an original classification of life stages that may be applicable to other fern populations with similar morphology. Using statistical analyses we distinguished: i) dynamic populations, which are characterized by a large proportion of sporelings and vegetative adults and are associated with streams and nemoral species; ii) stable populations, with a higher proportion of generative adults, growing prevalently in habitats rich in hygrophilous grasses and shrubs, with lower tree cover; iii) senile populations, with a relatively higher proportion of senescent individuals and with marked rejuvenation dominated by vegetative adults, which are prevalently located in spring swamps. The proportion of senescent stage individuals is positively correlated with the mean geographic distance between populations. Spring swamps, with populations that provide a clear example of remnant dynamics, are the habitat with the most stable conditions for O. regalis in the Mediterranean area
Considerazioni ecologiche e sintassonomiche su alcune garighe dell'entroterra tra Siena e Viterbo (Italia centrale)
No full textHabitat characteristics and vegetation context of Osmunda regalis L. at the southern edge of its distribution in Europe
No full textThe abundance of Osmunda regalis was investigated in 42 natural populations in central Italy in order to (i) test which habitat characteristics correlate with its abundance at regional scale and at local scale, and (ii) identify the optimal habitats for the species in a Mediterranean area. This knowledge may contribute to the effective conservation of O. regalis, which is under threat in Italy. Ramets (rosettes of fronds) were counted in several plots of 25 m(2) within each population and related to habitat characteristics as well as plant species composition using univariate and multivariate statistics. The abundance of ramets at regional scale was positively correlated with mean annual precipitation and altitude. Large populations mainly occurred at sites with northeastern exposure, i.e. a cool and humid microclimate. The density of ramets at local scale was negatively correlated with rockiness, stoniness and shrub cover. Vascular plant species associated with high density of O. regalis were pioneer species typical of open woods and stagnant waters. Spring swamps therefore represent the habitat with the most favourable edaphic, microclimatic and vegetational conditions for the species at the southern edge of its distribution in Europe, where the limiting factor is the annual water availability
Osmundo-Alnion woods in Tuscany (Italy): A phytogeographical analysis from a west European perspective
No full textRiparian woods with
Alnus glutinosa
and
Osmunda regalis
in Tuscany (central Italy) were studied, whilst western European
riparian alderwoods were analysed from a phytogeographical perspective, with particular reference to
Osmundo–Alnion
and
its suballiances. Two associations were identified through the phytosociological analysis of the Tuscan coenoses:
Carici
pallescentis–Osmundetum regalis ass. nova
for mainland Tuscany and
Carici microcarpae–Alnetum glutinosae
for the Tuscan
islands. A phytogeographical analysis for western Europe (47 phytocoenoses, 567 relevés) was performed using floristic
classification and chorology-based discriminant analysis. These allowed us to identify phytocoenoses: (1) attributed to
Alnion incanae
, correlated with the Eurasian and Boreal chorotypes; and (2) attributed to
Osmundo–Alnion
, correlated with
the west Mediterranean, wide-distribution and Atlantic chorotypes. The floristic and ecological differences allowed us to
divide
Osmundo–Alnion
into two suballiances: (1) phytocoenoses distributed on the Iberian peninsula, correlated with the
Atlantic and endemic Iberian chorotypes, attributable to
Osmundo–Alnenion
; and (2) phytocoenoses distributed in Algeria,
Corsica, Sardinia, Sicily and Tyrrhenian Italy, correlated with the Mediterranean, endemic Sardinian–Corsican and
endemic Italian chorotypes, attributable to
Hyperico hircini–Alnenion glutinosae
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