Search results for "VEGETATION"
showing 10 items of 1069 documents
Analysis of the bryophyte diversity of mountain ranges in Sicily.
2015
The focus of this study was an analysis of the bryophyte flora of the main Sicilian mountain ranges, i.e., Peloritani, Nebrodi and Madonie mountains, located along the northern side of the Island, the Sicani mountains, located in the west-central Sicily and the Etna, the highest and most active volcano of Europe. The overall bryoflora consists of 504 taxa, 400 mosses and 104 liverworts and hornworts. It represent the 85.3% of the whole Sicilian flora; the mosses are referred to 37 families, the liverworts together with hornworts to 31 families. The phytogeographical analysis has shown the prevalence of the Mediterranean species, with the highest value on the Sicani mountains. It is notewort…
A survey of the epiphytic bryophyte flora of the Rif and Tazzeka Mountains (northern Morocco)
2005
SUMMARY The catalogue of the epiphytic bryophyte flora of the Rif Mountains includes a total of 72 taxa, of which 66 are mosses and six are liverworts. Some new records are provided: Hypnum resupinatum and Tortula israelis, new to northern Africa, Antitrichia curtipendula and Cryphaea heteromalla, new to Morocco, and Dicranoweisia cirrata, Isothecium alopecuroides and Orthotrichum macrocephalum ,n ew to the Rif Mountains. Epiphytic communities in the different forest types have been analysed, with the conclusion that altitude and humidity are the main factors that determine their composition. The epiphytic stratum is best developed at the highest altitudes on the Principal chain and Tazzeka…
Experimental analysis of the effect of vegetation on flow and bed shear stress distribution in high-curvature bends
2016
The cross-sectional circulation, which develops in meandering bends, exerts an important role in velocity and the boundary shear stress redistributions. This paper considers the effect of vegetation on cross-sectional flow and bed shear distribution along a high-curvature bend. The analysis is conducted with the aid of data collected in a large-amplitude meandering flume during a reference experiment without vegetation and an experiment with vegetation on the bed. The results show that the presence of vegetation modifies the curvature-induced flow pattern and the directionality of turbulent structures. In fact, in the presence of vegetation, the turbulent structures tend to develop within a…
Flow Resistance Law in Channels with Flexible Submerged Vegetation
2005
In this paper, experimental data collected in a straight flume having a bed covered by grasslike vegetation have been used to analyze flow resistance for flexible submerged elements. At first, the measurements are used to test the applicability of Kouwen’s method. Then, a calibration of two coefficients appearing in the semilogarithmic flow resistance equation is carried out. Finally, applying the P-theorem and the incomplete self-similarity condition, a flow resistance equation linking the friction factor with the shear Reynolds number, the depth-vegetation height ratio and the inflection degree is deduced.
Using the ARP-03 for high-resolution mapping of calcic horizons
2013
A b s t r a c t. The aim of this work is to present a fast and cheap method for high-resolution mapping of calcic horizons in vineyards based on geoelectrical proximal sensing. The study area, 45 ha located in southern Sicily (Italy), was characterized by an old, partially dismantled marine terrace and soils with a calcic horizon at different depths. The geoelectrical investigation consisted of a survey of the soil electrical resistivity recorded with the Automatic Resistivity Profiling-03 sensor. The electrical resistivity values at three pseudo-depths, 0-50, 0-100 and 0-170 cm, were spatialized by means of ordinary kriging. A principal component analysis of the three electrical resistivit…
Flexible vegetation behaviour and effects on flow conveyance: experimental observations
2015
As it is known, vegetation is an important component of aquatic ecosystems. Because of the variety of species and, thus, of the characteristics of the vegetation elements (form, size, stiffness, etc.), it is difficult to develop a widely applicable method to predict mean flow and flow resistance. Despite the intense activity research, much work has to be done in understanding hydrodynamics in vegetated channels. This is important to analyse many physical processes involved in the ecosystem at different spatial and time scales. In this paper, attention is restricted to flexible vegetation. After a brief description of results obtained in previous experimental works conducted in a rectangular…
Novel leaf-level measurements of chlorophyll fluorescence for photosynthetic efficiency
2015
Solar induced chlorophyll fluorescence (SIF) from vegetation can now be obtained from satellites as well as ground-based field studies, at select wavelengths associated with atmospheric features. At the leaf level, full spectrum (650–800 nm) chlorophyll emissions (ChlF) can be measured using specialized instrumentation to support interpretation of these SIF observations. We found that ChlF spectra differ for leaf bottoms versus upper leaf surfaces, potentially affecting within-canopy radiative scattering. Our ChlF measurements for leaves of eight tree species (n≥125) obtained during fall 2013 senescence at the Duke Forest in North Carolina, USA and the 2014 growing season (n=72) at the USDA…
Evaluation of a technical revegetation action performed on foredunes at Devesa de la Albufera, Valencia, Spain
2010
We have evaluated the level of restoration achieved by a technical revegetation action carried out on reconstructed foredunes at the Devesa de la Albufera and compared this level with that achieved by spontaneous succession. Foredunes 1, 3, 6 and 20 y old since revegetated (1, 3, 6 and 20 y, respectively) were considered as spatially separated stages representing a successional trend in the development of the restored plant community. Lower and similar levels of diversity (richness and H´ and Pielou´s indexes) and coverage, respectively, were found on dunes corresponding to the oldest stage of technical revegetation compared with that of the reference site. Diversity and coverage parameters…
Vegetation and firewood uses in the western Catalan plain from Neolithic to the Middle Age
2011
In this study is presented the synthesis of the results of the anthracological analysis in the western Catalan plain from the Neolithic to the Middle Ages. The data is evaluated in order to provide a preliminary approximation on the development of vegetation and forest exploitation. S. Vila is funded by a FI-DGR 2010 scholarship,granted by the Generalitat de Catalunya (AGAUR), in the framework of the projects HAR2008-05256, and SGR2009-198.
Effects of heavy metals on soil microflora
2000
Elevated concentrations of heavy metals are known to cause disturbances in all living organisms. A reduction in the activity of forest microbes, expressed as decreased carbon and nitrogen mineralisation, may result in a slower rate of litter decomposition and slower nutrient cycling in the whole ecosystem (Baath 1989). In areas severely polluted by heavy metals, this can be seen as an accumulation of undecomposed litter on the forest floor. Thus, in addition to the direct toxicity of heavy metals, the trees may suffer from nutrient deficiency resulting from the decrease in the mineralisation of nutrients from the litter. Heavy metals can also retard litter decomposition processes in less po…