Search results for "forest"

Modelling the occurrence of rainy days under a typical Mediterranean climate

2014

The statistical inference of the alternation of wet and dry periods in daily rainfall records can be achieved through the modelling of inter-arrival time-series, IT, defined as the succession of times elapsed from a rainy day and the one immediately preceding it. In this paper, under the hypothesis that ITs are independent and identically distributed random variables, a modelling framework based on a generalisation of the commonly adopted Bernoulli process is introduced. Within this framework, the capability of three discrete distributions, belonging to the Hurwitz–Lerch-Zeta family, to reproduce the main statistical features of IT time-series was tested. These distributions namely Lerch-se…

Modeling Fire Danger in Galicia and Asturias (Spain) from MODIS images

2014

Forest fires are one of the most dangerous natural hazards, especially when they are recurrent. In areas such as Galicia (Spain), forest fires are frequent and devastating. The development of fire risk models becomes a very important prevention task for these regions. Vegetation and moisture indices can be used to monitor vegetation status; however, the different indices may perform differently depending on the vegetation species. Eight different spectral indices were selected to determine the most appropriate index in Galicia. This study was extended to the adjacent region of Asturias. Six years of MODIS (Moderate Resolution Imaging Spectroradiometer) images, together with ground fire data…

The origin of in-plane stresses in axially moving orthotropic continua

2016

In this paper, we address the problem of the origin of in-plane stresses in continuous, two-dimensional high-speed webs. In the case of thin, slender webs, a typical modeling approach is the application of a stationary in-plane model, without considering the effects of the in-plane velocity field. However, for high-speed webs this approach is insufficient, because it neglects the coupling between the total material velocity and the deformation experienced by the material. By using a mixed Lagrange–Euler approach in model derivation, the solid continuum problem can be transformed into a solid continuum flow problem. Mass conservation in the flow problem, and the behaviour of free edges in th…

Testing different approaches to characterize Burundian soils by the best procedure

2011

Abstract The Beerkan Estimation of Soil Transfer parameters (BEST) procedure seems attractive for soil hydraulic characterization but it has received little testing so far. The objective of this investigation was to test BEST with different application approaches for some soils in Burundi, where there is the need of using simple methods to characterize soils. Most (14) of the 19 sampled sites had a clay soil texture whereas texture ranged from silty clay to loam in the other cases. On average, the fitting ability of both the particle size distribution (PSD) model (mean relative error, Me ( E r ) = 2.0%) and the cumulative infiltration model ( Me ( E r ) = 2.3%) was good according to recomme…

Infiltration Measurements for Soil Hydraulic Characterization

2016

This book summarises the main results of many contributions from researchers worldwide who have used the water infiltration process to characterize soil in the field. Determining soil hydrodynamic properties is essential to interpret and simulate the hydrological processes of economic and environmental interest. This book can be used as a guide to soil hydraulic characterization and in addition it gives a complete description of the treated techniques, including an outline of the most significant research results, with the main points that still needing development and improvement.

Determining hydraulic properties of a loam soil by alternative infiltrometer techniques

2015

Testing infiltrometer techniques to determine soil hydraulic properties is necessary for specific soils. For a loam soil, the water retention and hydraulic conductivity predicted by the BEST (Beerkan Estimation of Soil Transfer parameters) procedure of soil hydraulic characterization was compared with data collected by more standard laboratory and field techniques. Six infiltrometer techniques were also compared in terms of saturated soil hydraulic conductivity, Ks. BEST yielded water retention values statistically similar to those obtained in the laboratory and Ks values practically coinciding with those determined in the field with the pressure infiltrometer (PI). The unsaturated soil hyd…

DETERMINING THE SATURATED HYDRAULIC CONDUCTVITY OF A LOAM SOIL WITH DIFFERENT INFILTROMETER TECHNIQUES

2015

The saturated soil hydraulic conductivity, Ks, is one of the most important soil hydraulic properties since it controls many hydrological processes. This hydrodynamic parameter depends on soil texture and structure and it is very difficult to measure. Infiltrometer techniques are becoming very popular to determine Ks in the field but testing alternative approaches is necessary for specific soil types. For a loam soil, the estimated Ks values with six infiltrometer techniques were compared. The so-called BEST procedure of soil hydraulic characterization, the pressure infiltrometer (PI), single head experiments with both the tension infiltrometer (TI) and the mini disk infiltrometer (MDI), th…

MODIS-Based Monthly LST Products over Amazonia under Different Cloud Mask Schemes

2016

One of the major problems in the monitoring of tropical rainforests using satellite imagery is their persistent cloud coverage. The use of daily observations derived from high temporal resolution sensors, such as Moderate Resolution Imaging Spectroradiometer (MODIS), could potentially help to mitigate this issue, increasing the number of clear-sky observations. However, the cloud contamination effect should be removed from these results in order to provide a reliable description of these forests. In this study the available MODIS Land Surface Temperature (LST) products have been reprocessed over the Amazon Basin (10 N–20 S, 80 W–45 W) by introducing different cloud masking schemes. The mont…

REUTILIZACIÓN DE RESIDUOS DE PODA DE VID Y DE POSIDONIA OCEANICA EN LAS OBRAS DE BIOINGENIERÍA DEL PAISAJE

La popolazione mondiale è in continua espansione e la crescita demografica ed economica inducono allo sfruttamento progressivo dell’ambiente ed al depauperamento delle risorse naturali (acqua ed energia in particolare), con conseguenti impatti potenzialmente importanti sul cambiamento globale. Si rende, pertanto, necessaria ed urgente una più efficiente gestione delle risorse basata sulla rielaborazione di obiettivi sostenibili di politiche e strategie ambientali e sulla riduzione del consumo delle risorse, promuovendo la transizione da un modello di economia lineare ad uno circolare, costituito da un ciclo continuo di sviluppo positivo che preserva e migliora il capitale naturale, ottimizz…

Analysis of dust exposure during chainsaw forest operations

2017

Abstract: In 1999, the European Union proclaimed hardwood dust carcinogenic based on the classification of the International Agency for Research on Cancer (IARC) issued in 1995. The operational exposure limit (OEL) for inhalable wood dust has been set to 5 mg m-3 by EU directives, though in different countries the OEL ranges from 1 to 5 mg m-3. The objective of this study was to determine the exposure to wood dust of forest workers in chainsaw cutting and processing and suggest possible countermeasures. The study took into consideration different silvicultural treatments (coppice clear cut, conifer thinning, conifer pruning, and sanitary cut) and chainsaw fuel (normal two-stroke gasoline mi…