oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 59 )

2018 ( 308 )

2017 ( 276 )

2016 ( 376 )

Custom range...

Search Results: 1 - 10 of 167445 matches for " E. Chuvieco "
All listed articles are free for downloading (OA Articles)
Page 1 /167445
Display every page Item
Modelos de Simulación de Reflectividad en ecología: potencialidades y problemas
M. Yebra,E. Chuvieco
Ecosistemas , 2008,
Abstract: El uso de modelos de simulación de la reflectividad (MSR) para la estimación de parámetros biofísicos mediante imágenes de satélite se ha desarrollado notablemente en los últimos a os, gracias a su poder de generalización. No obstante, resultan complejos de parametrizar, lo que dificulta su uso operativo. En este trabajo se presentan los principales problemas que plantea el uso de los MSR en teledetección, resaltando la importancia de considerar relaciones ecofisiológicas entre las variables de entrada de estos modelos. Se presenta como caso práctico la estimación del contenido de humedad de matorrales mediterráneos a partir de imágenes MODIS, empleando los MSR denominados PROSPECT y SAILH. El análisis muestra cómo, al considerar la co-variación de las variables de entrada en la parametrización de los MSR se logran estimaciones más precisas (con errores medios cercanos al 30%) que si las variables se parámetrizan aleatoriamente (errores próximos al 50%).
Modelling long-term fire occurrence factors in Spain by accounting for local variations with geographically weighted regression
J. Martínez-Fernández, E. Chuvieco,N. Koutsias
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2013,
Abstract: Humans are responsible for most forest fires in Europe, but anthropogenic factors behind these events are still poorly understood. We tried to identify the driving factors of human-caused fire occurrence in Spain by applying two different statistical approaches. Firstly, assuming stationary processes for the whole country, we created models based on multiple linear regression and binary logistic regression to find factors associated with fire density and fire presence, respectively. Secondly, we used geographically weighted regression (GWR) to better understand and explore the local and regional variations of those factors behind human-caused fire occurrence. The number of human-caused fires occurring within a 25-yr period (1983–2007) was computed for each of the 7638 Spanish mainland municipalities, creating a binary variable (fire/no fire) to develop logistic models, and a continuous variable (fire density) to build standard linear regression models. A total of 383 657 fires were registered in the study dataset. The binary logistic model, which estimates the probability of having/not having a fire, successfully classified 76.4% of the total observations, while the ordinary least squares (OLS) regression model explained 53% of the variation of the fire density patterns (adjusted R2 = 0.53). Both approaches confirmed, in addition to forest and climatic variables, the importance of variables related with agrarian activities, land abandonment, rural population exodus and developmental processes as underlying factors of fire occurrence. For the GWR approach, the explanatory power of the GW linear model for fire density using an adaptive bandwidth increased from 53% to 67%, while for the GW logistic model the correctly classified observations improved only slightly, from 76.4% to 78.4%, but significantly according to the corrected Akaike Information Criterion (AICc), from 3451.19 to 3321.19. The results from GWR indicated a significant spatial variation in the local parameter estimates for all the variables and an important reduction of the autocorrelation in the residuals of the GW linear model. Despite the fitting improvement of local models, GW regression, more than an alternative to "global" or traditional regression modelling, seems to be a valuable complement to explore the non-stationary relationships between the response variable and the explanatory variables. The synergy of global and local modelling provides insights into fire management and policy and helps further our understanding of the fire problem over large areas while at the same time recognizing its local character.
Presentación
Chuvieco, Emilio
Estudios Geográficos , 2001,
Abstract:
Es el cristianismo responsable de la crisis ambiental del planeta?
Chuvieco Salinero, Emilio
Estudios Geográficos , 2012,
Abstract: As a result of a paper published in the sixties, Christianity has been frequently accused of being behind earth’s environmental degradation, on the grounds that it has given humans the religious support to adopt a dominant role over the rest of Creation. This paper explores some of the answers to those criticisms, both from a historical and theological point of view. In the second part, the paper explores to what extent the environmental degradation supposedly caused by Christianity has affected those countries with mostly Christian populations, comparing them with those with other religious traditions. Several indicators of environmental health and ecosystem conservation are used for the comparisons. A high correlation between per capita income and environmental performance for the Christian and Buddhist countries was observed, while poor trends were observed for Hindu and Islamic countries. Comparing representative countries of both large and medium population size, the Christian countries outperform others in most indicators. Even though it cannot be concluded that Christianity, in fact, encourages environmental conservation, the results from our analysis at least provide grounds to reject the opposite hypothesis, as Christian countries do not have significantly lower environmental indicators than those representing other major religions. En los a os sesenta se inicia el debate sobre el papel que el cristianismo ha tenido en la degradación ambiental del planeta, acusándosele de haber concedido al ser humano un estatus dominante frente al resto de los seres creados. En este artículo se revisan las distintas respuestas que se han dado a estas críticas desde el punto de vista histórico y teológico. En la segunda parte, se analiza hasta qué punto este supuesto carácter agresivo del cristianismo frente a otras religiones se manifiesta en la situación ambiental de los países cristianos frente a otros donde son mayoritarias otras religiones. Para ello, se emplean distintos indicadores relacionados con la salud ambiental y la salud de los ecosistemas. Se concluye que los países cristianos no presentan una peor situación ambiental que los representativos de otras religiones. Se observa una correlación clara entre nivel de riqueza y de calidad ambiental para los países cristianos, que no es tan evidente en los hindúes o musulmanes. A similar nivel de riqueza y población, los países cristianos de hecho ofrecen valores más altos de calidad ambiental que los encontrados en países con otras tradiciones religiosas. Si bien de nuestro análisis no puede concluirse que
Bibliografía
Bosque Sendra, Joaquín,Chuvieco, Emilio
Estudios Geográficos , 2001,
Abstract:
Cartografía de modelos de combustible con teledetección: aportaciones a un desarrollo ambiental sostenible
Ria?o, David,Salas, Javier,Chuvieco, Emilio
Estudios Geográficos , 2001,
Abstract: The conjugation of human development and sustainability of natural resources is a critical issue to our present society. The role of human activity in fire ocurrence is a good example of the difficult dialogue between development and conservation. Recent changes in land use patterns have carried along an increasing rate of fire occurrence, which implies in some cases severe effects on soil erosion and vegetation degradation. For this reason, it is critical to improve current tools to prevent and assess forest fires, so that fire occurrence may be reduced. This paper explores the use of remote sensing methods to derive fuel type maps. These maps are basic sources of information for fire behaviour modelling, since they make it possible to take into account vegetation characteristics for fire propagation. The study area is located in Caba eros National Park (Central Spain). The fuel type mapping was based in the analysis of two satellite Landsat-TM images and auxiliary information (digital elevation models and texture images). The digital classification worked out to have a global accuracy of 83 %. The larger problems found were to distinguish between the different heights of shrubs and identifying the existence of shrubs under the tress. [es] La conjunción entre desarrollo y sostenibilidad del medio ambiente se torna un aspecto de singular importancia en nuestra sociedad. La incidencia de la actividad humana en la aparición de incendios forestales supone un ejemplo nítido de esa afirmación, ya que los cambios recientes en los patrones de utilización del territorio van acompa ados de un notable aumento de los incendios forestales, con la consiguiente degradación del suelo y la cubierta vegetal. En este contexto, resulta de suma importancia mejorar las herramientas de prevención de incendios y evaluación de sus efectos, de cara a reducir la ocurrencia o paliar los efectos de este fenómeno. En este artículo analizamos el papel de la teledetección espacial para obtener cartografía de modelos de combustible. Estos mapas aportan una información básica en los sistemas de prevención, predicción y modelado de incendios forestales, ya que permiten analizar las características y estructura de la vegetación de cara a la propagación del fuego. Hemos utilizado como área de estudio el Parque Nacional de Caba eros (Ciudad Real). La cartografía de combustible se ha basado en el análisis de dos imágenes de satélite Landsat- TM, junto con información auxiliar (modelos digitales de elevación y texturas). Los resultados de la clasificación ofrecieron una precisión promedio del
VALIDACIóN PARA COLOMBIA DE LA ESTIMACIóN DE áREA QUEMADA DEL PRODUCTO L3JRC EN EL PERIODO 2001-2007
Anaya-Acevedo,Jesús A.; Chuvieco-Salinero,Emilio;
Actualidades Biológicas , 2010,
Abstract: this document presents a validation of the global burned area product (l3jrc) in colombia, using the method of the confusion matrix where landsat images are used as a proxy for fieldwork. the product l3jrc is a burned area map based on remote sensing spot-vegetation data and generated by tansey et al. in 2007. determination of burned area using satellite data is possible because of the difference in reflectance before and after a fire. a pattern toward larger omission errors was found in the validation process, although commission errors also were present. disregarding the type of error, it was shown that the product l3jrc underestimates 40% of the burned area of the country. with this accuracy of assessment, it was concluded that the annual average burned area in colombia during the annual study period was 14,807 km2, taking into account omission values burned area may exceed 21.000 km2. orinoquia region has more than (90%), of the total burned area of the country, where vichada, meta, arauca, and casanare were the most affected colombian departments.
VALIDACIóN PARA COLOMBIA DE LA ESTIMACIóN DE áREA QUEMADA DEL PRODUCTO L3JRC EN EL PERIODO 2001-2007 VALIDATION OF THE L3JRC BURNED AREA PRODUCT ESTIMATION IN COLOMBIA FROM 2001 TO 2007
Jesús A. Anaya-Acevedo,Emilio Chuvieco-Salinero
Actualidades Biológicas , 2010,
Abstract: Este documento presenta la validación del producto global de área quemada L3JRC en Colombia utilizando el método de matrices de confusión e imágenes de satélite Landsat como sustituto a la verdad terreno. El producto L3JRC, generado por Tansey et al. en el a o 2007, es un mapa de áreas quemadas obtenido por teledetección con datos del instrumento SPOT-VEGETATION. La determinación del área quemada generada por los incendios se obtiene por teledetección gracias a la diferencia en reflectividad antes del fuego (vegetación) y después del fuego. La validación del producto demuestra clara tendencia hacia la omisión de áreas quemadas, aunque también con errores importantes por comisión. Sin tener en cuenta el tipo de error, se encontró que el producto L3JRC subestima en 40% la superficie quemada del país. Con las consideraciones en la fiabilidad se concluye que el promedio anual de área quemada en Colombia es de 14.807 km2 aunque podría superar los 21.000 km2 si se tienen en cuenta los altos valores de omisión y subestimación detectados en la validación. La región de la Orinoquia tiene más del 90% del área total del país, siendo los departamentos colombianos con mayor área quemada Vichada, Meta, Arauca y Casanare. This document presents a validation of the global burned area product (L3JRC) in Colombia, using the method of the confusion matrix where Landsat images are used as a proxy for fieldwork. The product L3JRC is a burned area map based on remote sensing SPOT-VEGETATION data and generated by Tansey et al. in 2007. Determination of burned area using satellite data is possible because of the difference in reflectance before and after a fire. A pattern toward larger omission errors was found in the validation process, although commission errors also were present. Disregarding the type of error, it was shown that the product L3JRC underestimates 40% of the burned area of the country. With this accuracy of assessment, it was concluded that the annual average burned area in Colombia during the annual study period was 14,807 km2, taking into account omission values burned area may exceed 21.000 km2. Orinoquia region has more than (90%), of the total burned area of the country, where Vichada, Meta, Arauca, and Casanare were the most affected Colombian departments.
Interpolación espacial de la evapotranspiración del cultivo de referencia, ET0 a partir de imágenes de satélite
Sánchez Martínez, Marcela,Chuvieco Salinero, Emilio
Estudios Geográficos , 2002,
Abstract: This paper intends to obtain accurate estimations of reference évapotranspiration from multitemporal analysis of NOAA-AVHRR images. The study area corresponds to the Autonomous Community of Andalucía, and the period of analysis comprehends the spring and summer seasons of 1994 to 1997. Results obtained from multiple regression analysis are compared with those derived from spatial interpolation, using geostatistical methods. The results show a better fitting and more realistic trends for those maps derived from satellite data than those generated from spatial interpolation. A partir de análisis de regresión múltiple entre valores de evapotranspiración del cultivo de referencia diaria, ET0, estimados con el método de Penman-Monteith y diversas variables derivadas de imágenes NOAA-AVHRR, se generan modelos que permiten estimar la ET0 en la Comunidad Autónoma de Andalucía en el período comprendido entre los a os 1994 y 1997. Los modelos fueron evaluados satisfactoriamente en las estaciones meteorológicas utilizadas, así como también a través de mapas regionales de porcentajes de variación entre valores observados y estimados. De acuerdo con estos resultados es posible afirmar la utilidad de la teledetección en la determinación de la ET0 a escala regional.
Método basado en teledetección para estimar la emisión de gases efecto invernadero por quema de biomasa
Anaya Acevedo,Jesús Adolfo; Chuvieco Salinero,Emilio; Palacios-Orueta,Alicia;
Revista Ingenierías Universidad de Medellín , 2011,
Abstract: biomass burning is a major source of greenhouse gas emissions in developing countries. in colombia, land use change, forestry and agriculture are responsible for more than 50% of the total greenhouse gas emissions. fire is commonly used as a mechanism for land use change. in colombia the llanos orientales and the amazonia are subject to biomass burning every year during the dry season, especially from january to march. studies of the spatial and temporal distribution of emissions are required for emissions report at a national level. the goal of this state of the art article is to describe a method to estimate emissions with a remote sensing approach and to present some of the variables already measured in colombia.
Page 1 /167445
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.