Search results for "VEGETATION"
showing 10 items of 1069 documents
Contribution of raindrop impact to the change of soil physical properties and water erosion under semi-arid rainfalls
2017
Soil erosion by water is a three-phase process that consists of detachment of soil particles from the soil mass, transportation of detached particles either by raindrop impact or surface water flow, and sedimentation. Detachment by raindrops is a key component of the soil erosion process. However, little information is available on the role of raindrop impact on soil losses in the semi-arid regions where vegetation cover is often poor and does not protect the soil from rainfall. The objective of this study is to determine the contribution of raindrop impact to changes in soil physical properties and soil losses in a semiarid weakly-aggregated agricultural soil. Soil losses were measured und…
Plant communities, synusiae and the arithmetic of a sustainable classification
2022
We propose an equation to evaluate the efficiency of a classification as a function of the effort required and the population size of data collectors. The formula postulates a “classification efficiency coefficient”, which relates not only to the complexity of the object to be classified, but also to the data availability and representativeness. When applied to the classification of phytocoenoses, the equation suggests that a classification system based on vascular plants offers the best compromise between sampling effort, resolution power and data availability. We discuss the possibility of basing a vegetation classification on plot records for all macroscopic photoautotrophic organisms co…
Biodiversità vegetale degli stagni temporanei della Sicilia
2009
Gli ambienti umidi effimeri ospitano comunità vegetali specializzate e sono sede esclusiva di rare microterofite nonché autentiche stazioni di rifugio per molte specie a ciclo effimero. Per l’interesse bio-ecologico, Braun-Blanquet ha definito queste fitocenosi un gioiello floristico. Anche la Comunità Europea, con la direttiva Habitat 92/43/CEE, riconosce agli stagni temporanei mediterranei una notevole importanza e li individua come habitat prioritario (3170*). Questi ambienti, essendo stagionali, di modesta estensione, spazialmente dispersi e difficilmente cartografabili, spesso vengono trascurati negli studi a scala di paesaggio. Tali habitat, invece, rappresentano veri e propri micro-h…
Revegetation of harvested peat surfaces in relation to substrate quality
1994
. The relationship between substrate quality and pattern of revegetation of harvested peat surfaces was studied by means of a survey and a field experiment examining influences of modest NPK-fertilization on plant colonization of an initially bare peat surface. The harvested peat surfaces varied a great deal in their chemical and physical characteristics and the sites differed in revegetation pattern. Early successional vegetation was dominated by perennial species native to nutrient-poor habitats on all sites. Soluble phosphorus and ash content, mean particle size of surface peat, and thickness of peat layer had the strongest influence in a CCA-ordination of species. The species compositio…
Evaluating the effects of forest tree species on rill detachment capacity in a semi-arid environment
2021
Abstract The beneficial effects of plant roots in decreasing soil detachment in forest ecosystems exposed to rill erosion are well known. However, these effects vary largely between different plant species. There has been lots of research into the relationship between root-soil systems and rill erodibility with a particular focus on grass species. Conversely, fewer studies are available for tree species, especially in forests of semi-arid or arid environments. Greater knowledge is therefore needed to identify the most effective tree species against rill erosion in these ecosystems, where water availability is the limiting factor for vegetation growth and afforestation is often the only solu…
Phenology Estimation From Meteosat Second Generation Data
2013
Many studies have focused on land surface phenology, for example as a means to characterize both water and carbon cycles for climate model inputs. However, the Spinning Enhanced Visible Infra-Red Imager (SEVIRI) sensor onboard Meteosat Second Generation (MSG) geostationary satellite has never been used for this goal. Here, five years of MSG-SEVIRI data have been processed to retrieve Normalized Difference Vegetation Index (NDVI) daily time series. Due to existing gaps as well as atmospheric and cloud contamination in the time series, an algorithm based on the iterative Interpolation for Data Reconstruction (IDR) has been developed and applied to SEVIRI NDVI time series, from which phenologi…
Learning main drivers of crop progress and failure in Europe with interpretable machine learning
2021
Abstract A wide variety of methods exist nowadays to address the important problem of estimating crop yields from available remote sensing and climate data. Among the different approaches, machine learning (ML) techniques are being increasingly adopted, since they allow exploiting all the information on crop progress and environmental conditions and their relations with crop yield, achieving reliable and accurate estimations. However, interpreting the relationships learned by the ML models, and hence getting insights about the problem, remains a complex and usually unexplored task. Without accountability, confidence and trust in the ML models can be compromised. Here, we develop interpretab…
Syntaxonomy of the Parietarietea judaicae class in Europe.
1999
On the basis of literature and unpublished data, a syntaxonomical review about the chasmophilous sinanthropic vegetation occurring in the Mediterranean territories and in the Atlantic and Central Europe was carried out. These plant communities are linked to masonry walls and rocky faces heavily disturbed by men, which are colonized by a fairly specialized flora dominated by hemicriptophytes, chamaephytes and mosses. From the syntaxonomical point of view, in accordance with the greatest part of the authors who studied the matter, the wall vegetation must be considered in a well-distinguished class whose valid name is Parietarietea judaicae Oberd. 1977, rather than in the Asplenietea trichoma…
Mapping evapotranspiration on vineyards: A comparison between Penman-Monteith and energy balance approaches for operational purposes
2012
Estimation of evapotranspiration (ET) in Sicilian vineyard is an emerging issue since these agricultural systems are more and more converted from rainfed to irrigated conditions, with significant impacts on the management of the scarce water resources of the region. The choice of the most appropriate methodology for assessing water use in these systems is still an issue of debating, due to the complexity of canopy and root systems and for their high spatial fragmentation. In vineyards, quality and quantity of the final product are dependent on the controlled stress conditions to be set trough irrigation. This paper reports an application of the well-known Penman-Monteith approach, applied i…
Accuracy assessment of fraction of vegetation cover and leaf area index estimates from pragmatic methods in a cropland area
2009
The fraction of vegetation cover (FVC) and the leaf area index (LAI) are important parameters for many agronomic, ecological and meteorological applications. Several in-situ and remote sensing techniques for estimating FVC and LAI have been developed in recent years. In this paper, the uncertainty of in-situ FVC and LAI measurements was evaluated by comparing estimates from LAI-2000 and digital hemispherical photography (DHP). The accuracy achieved with a spectral mixture analysis algorithm and two vegetation indices-based methods was assessed using atmospherically corrected Landsat Thematic Mapper (TM) data over the Barrax cropland area where the European Space Agency (ESA) SENtinel-2 and …