Search results for "VEGETATION"
showing 10 items of 1069 documents
Phytosociology and ecology of deciduous forests in Tajikistan (Middle Asia)
2017
Aims: To present the first syntaxonomical classification for the mesophilous deciduous forests of the PamirAlai Mountains in Tajikistan with some remarks on its environmental gradients. Location: Tajikistan. Methods: Altogether 201 relevés were sampled between 2008‒2013 using the seven-degree cover-abundance scale of Braun-Blanquet. They were classified by the modified TWINSPAN method using the four-step interval scale with cutoff levels of 0%, 2%, 5% and 10% and total inertia as a measure of cluster heterogeneity. Diagnostic species were identified using the phi coefficient as a fidelity measure. Detrendended Correspondence Analysis was used to determine the relation between samples, veget…
The impact of in-canopy wind profile formulations on heat flux estimation in an open orchard using the remote sensing-based two-source model
2010
Abstract. For open orchard and vineyard canopies containing significant fractions of exposed soil (>50%), typical of Mediterranean agricultural regions, the energy balance of the vegetation elements is strongly influenced by heat exchange with the bare soil/substrate. For these agricultural systems a "two-source" approach, where radiation and turbulent exchange between the soil and canopy elements are explicitly modelled, appears to be the only suitable methodology for reliably assessing energy fluxes. In strongly clumped canopies, the effective wind speed profile inside and below the canopy layer can strongly influence the partitioning of energy fluxes between the soil and vegetation co…
Effects of rainfall events on the evapotranspiration retrieved by an energy balance model
2009
An alternative way to map the actual evapotranspiration (ET) spatial distribution at daily scale is the application of residual surface energy balance models to satellite images that are characterised by high temporal frequency and moderate spatial resolution, like those acquired by the MODIS sensors on board of TERRA and AQUA platforms. Within this research the well-known SEBAL model has been applied on an area located in the southern part of Sicily (Imera Meridionale catchment) using four images acquired between the 27th of March and the 11th of April 2007. The catchment extends for about 2000 km2 and includes both mountains and hill areas: the first are located in the northern part (the …
Prediction of rapid versus prolonged healing of infective endocarditis by monitoring vegetation size.
1991
The diagnostic value of transesophageal echocardiography in monitoring the clinical course has been evaluated in 83 patients with echocardiographic evidence of infective endocarditis. A total of 103 vegetations attached to the aortic or mitral valves were detected by use of the transesophageal approach. The patients were monitored for a mean of 74 weeks and underwent a minimum of two consecutive transesophageal echocardiographic examinations. Group A included patients with increasing or remaining constant size of vegetation (8.2 +/- 1.5 to 11.2 mm, p less than 0.05) during 4 to 8 weeks of antimicrobial therapy, whereas group B was formed by patients with decreasing vegetation size (8.3 +/- …
Multisensor comparison of NDVI for a semi‐arid environment in Spain
2009
The joint use of multiresolution sensors from different satellites offers many opportunities to describe vegetation and its dynamics. This paper introduces the concept of a virtual constellation (defined as an ensemble of all Earth Observation satellites in orbit that satisfy common requirements) for agricultural applications and contributes to providing the necessary inter-sensor calibration methodology for spectral reflectances and NDVI. For this purpose, we performed an observational study, comparing reflectances and the Normalized Difference Vegetation Index (NDVI), from near-synchronous image pairs of Landsat 7 Enhanced Thematic Mapper Plus (ETM+), as the reference sensor and Landsat 5…
Improved land surface emissivities over agricultural areas using ASTER NDVI
2006
Abstract Land surface emissivity retrieval over agricultural regions is important for energy balance estimations, land cover assessment and other related environmental studies. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) produces images of sufficient spatial resolution (from 15 m to 90 m) to be of use in agricultural studies, in which fields of crops are too small to be well-resolved by low resolution sensors. The ASTER project generates land surface emissivity images as a Standard Product (AST05) using the Temperature/Emissivity Separation (TES) algorithm. However, the TES algorithm is prone to scaling errors in estimating emissivities for surfaces with low s…
Vegetation dynamics from NDVI time series analysis using the wavelet transform
2009
A multi-resolution analysis (MRA) based on the wavelet transform (WT) has been implemented to study NDVI time series. These series, which are non-stationary and present short-term, seasonal and long-term variations, can be decomposed using this MRA as a sum of series associated with different temporal scales. The main focus of the paper is to check the potential of this MRA to capture and describe both intra- and inter-annual changes in the data, i.e., to discuss the ability of the proposed procedure to monitor vegetation dynamics at regional scale. Our approach concentrates on what wavelet analysis can tell us about a NDVI time series. On the one hand, the intra-annual series, linked to th…
Column aerosol characterization in a semi‐arid region around Marrakech during the WATERMED 2003 campaign
2008
In the framework of the WATERMED (WATer use efficiency in natural vegetation and agricultural areas by Remote sensing in the MEDiterranean basin) project, an experimental field campaign was carried out in a semi‐arid region near Marrakech, Morocco, during March 2003. This work focused on the columnar aerosol characterization from spectroradiometric and photometric measurements of direct solar irradiance and sky radiance at ground level. The results show a high dependence of the aerosol optical properties on the air masses present in the area. Two periods with different aerosol loads were observed in the campaign. In the first, Atlantic‐origin aerosols showed a marine particle accumulation m…
The decline of the cork oak growing in Sicily is accompanied by the loss of the functions proper to agroforestry systems
2021
The cork oak is one of the most important tree species in the Mediterranean basin, where it covers more than 2 million hectares. Among evergreen oaks, Quercus suber stands out for the variety of cultural systems in which it has been successfully employed, including typical agroforestry systems. Accordingly, a wide range of ecosystem services may be associated to cork oak, including the preservation of biodiversity, carbon sequestration and forage production. In the Mediterranean, the cork oak represents a key species for many natural and seminatural landscapes and habitats, as well as playing a prominent role for the economic and social development of local communities. However, there is in…
First insights into weed communities of rice agrocoenoses in southern Thailand
2015
The study presents the results of geobotanical investigations conducted in rice fields in southern Thailand in 2013. It is focussed on the classification of plant communities poorly investigated from a geobotanical standpoint. Altogether 125 phytosociological relevés were collected, using the Braun-Blanquet method. We noted more than 100 species in the vegetation plots, including many rare ones. We classified the vegetation into seven communities, including six associations. Five associations are proposed as new: Nymphaeetum nouchali, Fimbristylido miliaceae-Sphenocleetum zeylanicae, Ischaemo rugosi-Cyperetum pulcherrimi, Pentapeto phoeniceae-Aeschynomenetum indicae and Marsileetum minutae.…