1,720,990 research outputs found
Contribución al estudio de la vulnerabilidad al cambio climático en México /
No full text\ua0tesis que para obtener el grado de Doctor en Geografía presenta Alejandro Ismael Monterroso Rivas ; Directora de tesis Cecilia Conde Álvarez154 páginas :\ua0ilustracionesDoctorado en Geografía\ua0Universidad Nacional Autónoma de México,\ua02012\ua0Programa de Posgrado en Geografí
Estrategias de mitigación de CO2 a partir de la respiración del suelo
Full text linkSoil, in addition to storing is a source of CO2 to the atmosphere emitted by soil respiration, mainly due to land use change. The objective of the research was to evaluate soil respiration in different uses and quantify its CO2 emissions at two different times of the year, as well as estimate the storage of this to make a balance to establish strategies that allows with the climate change mitigation. Using a closed dynamic chamber placed on the soil and integrated with an infrared gas analyzer measured the CO2 emission every 30 min, as well as temperature and moisture of the soil with sensors. Three land uses (agroforestry, forestry and agricultural) and two seasons of the year (summer and winter) were analyzed for 24 continuous hours at each site. Positive correlation between ambient temperature and soil respiration was found to exist. The agricultural system stores low carbon content in the soil (50.31 t C ha-1) and emits 9.28 t of C ha-1 in the highest temperature season, in contrast to a natural system that emits 3.98 t of C ha-1 and stores 198.90 t of C ha-1. The balance sheet reflects the need to know CO2 emissions to the atmosphere from soils and not just warehouses. Having scientific support from the ground to the atmosphere is an important step in decision-making that will contribute to climate change mitigation.O solo, além de ser armazenado, é uma fonte de CO2 para a atmosfera emitida pela respiração do solo, principalmente devido à mudança de uso do solo. O objectivo da investigação era avaliar a respiração do solo em diferentes usos e quantificar as emissões de CO2 em dois momentos diferentes do ano, bem como estimar o seu armazenamento para fazer um balanço que permita estabelecer estratégias que ajudem a mitigar as alterações climáticas. Utilizando uma câmara dinâmica fechada colocada no solo e integrada com um analisador de gases infravermelhos, as emissões de CO2 foram medidas a cada 30 minutos, bem como a temperatura e humidade do solo com sensores. Três utilizações da terra (agroflorestação, silvicultura e agricultura) e duas estações (Verão e Inverno) foram analisadas continuamente durante 24 horas em cada local. Verificou-se que existe uma correlação positiva entre a temperatura ambiental e a respiração do solo. O sistema agrícola armazena baixo carbono no solo (50,31 t C ha-1 ) e liberta até 9,28 t C ha-1 na estação de temperaturas mais elevadas, em contraste com um sistema natural que emite 3,98 t C ha-1 e armazena 198,90 t C ha-1. O equilíbrio reflecte a necessidade de conhecer as emissões de CO2 para a atmosfera provenientes do solo e não apenas das instalações de armazenamento. Ter apoio científico do solo para a atmosfera é um passo importante na tomada de decisões que contribuem para a mitigação das alterações climáticas.El suelo, además de almacenar es fuente de CO2 a la atmósfera emitido por la respiración del suelo a causa, principalmente del cambio de uso del suelo. El objetivo de la investigación fue evaluar la respiración del suelo en diferentes usos y cuantificar las emisiones de CO2 en dos diferentes momentos del año, así como estimar el almacén de este para hacer un balance que permita establecer estrategias que ayuden con la mitigación del cambio climático. Mediante una cámara dinámica cerrada colocada en el suelo e integrada con un analizador de gas infrarrojo se midió la emisión de CO2 cada 30 min, así como temperatura y humedad del suelo con sensores. Se analizaron tres usos del suelo (agroforestal, forestal y agrícola) y dos temporadas del año (verano e invierno) durante 24 horas continuas en cada en sitio. Se encontró que existe correlación positiva entre temperatura ambiental y respiración del suelo. El sistema agrícola almacena bajo contenido de carbono en el suelo (50,31 t C ha-1) y libera hasta 9,28 t de C ha-1 en la temporada de mayor temperatura, en contraste con un sistema natural que emite 3,98 t de C ha-1 y almacena 198,90 t de C ha-1. El balance refleja la necesidad de conocer las emisiones de CO2 a la atmósfera por los suelos y no sólo los almacenes. Contar con soporte científico desde la respiración del suelo a la atmósfera es un paso importante para la toma de decisiones que contribuyan a la mitigación del cambio climático
Retos de adaptación al cambio climático para la agricultura de México
Full text linkPonencia presentada en: XII Congreso de la Asociación Española de Climatología celebrado en Santiago de Compostela entre el 19 y el 21 de octubre de 2022.[ES]El estudio del impacto del cambio climático sobre la actividad agrícola ha sido
explorado desde hace varios años a nivel nacional. Desde el Departamento de Suelos
de la Universidad Autónoma Chapingo un equipo de trabajo multidisciplinario ha
trabajado desde hace varios años en proyectos de adaptación al cambio climático. Por
lo que el objetivo del presente es mostrar los principales impactos del cambio
climático a partir de los estudios antes indicados y otros más en la actividad agrícola
nacional. Se muestran indicadores que sugieren el seguimiento a las acciones de
adaptación en el sector. Cabe recordar que la actividad agrícola es parte importante de
la economía en México por lo que es menester evidenciar su vulnerabilidad a los
cambios en el clima. Se muestran resultados sobre los impactos del cambio climático
sobre las aptitudes actuales y futuras, con escenarios de cambio climático, de poco
mas de quince cultivos de importancia; también sobre el cambio en el periodo de
crecimiento que muestra los posibles impactos en esta variable. Sobre los cultivos
estudiados se muestra el cambio en los rendimientos futuros para evaluar el cambio
potencial y establecer un impacto por esta variable. Así mismo, los resultados incluyen
el cambio en temperatura y humedad de los suelos de México.[EN]The study of the impact of climate change on agricultural activity has been explored
for several years at the national level. From the Department of Soils of the Universidad
Autónoma Chapingo, a multidisciplinary work team has been working for several
years on climate change adaptation projects. Therefore, the objective of the present is
to show the main impacts of climate change based on the aforementioned studies and
others in the national agricultural activity. Indicators are shown that suggest the
monitoring of adaptation actions in the sector. It should be remembered that
agricultural activity is an important part of the economy in Mexico, so it is necessary
to demonstrate its vulnerability to changes in the climate. Results are shown on the
impacts of climate change on current and future skills, with climate change scenarios,
of just over fifteen important crops; also on the change in the growth period that shows
the possible impacts on this variable. On the crops studied, the change in future yields
is shown to evaluate the potential change and establish an impact for this variable.
Likewise, the results include temperature and humidity of the soils of Mexico
Estratégias de mitigação de CO2 da respiração do solo
No full textSoil, in addition to storing is a source of CO2 to the atmosphere emitted by soil respiration, mainly due to land use change. The objective of the research was to evaluate soil respiration in different uses and quantify its CO2 emissions at two different times of the year, as well as estimate the storage of this to make a balance to establish strategies that allows with the climate change mitigation. Using a closed dynamic chamber placed on the soil and integrated with an infrared gas analyzer measured the CO2 emission every 30 min, as well as temperature and moisture of the soil with sensors. Three land uses (agroforestry, forestry and agricultural) and two seasons of the year (summer and winter) were analyzed for 24 continuous hours at each site. Positive correlation between ambient temperature and soil respiration was found to exist. The agricultural system stores low carbon content in the soil (50.31 t C ha-1) and emits 9.28 t of C ha-1 in the highest temperature season, in contrast to a natural system that emits 3.98 t of C ha-1 and stores 198.90 t of C ha-1. The balance sheet reflects the need to know CO2 emissions to the atmosphere from soils and not just warehouses. Having scientific support from the ground to the atmosphere is an important step in decision-making that will contribute to climate change mitigation.El suelo, además de almacenar es fuente de CO2 a la atmósfera emitido por la respiración del suelo a causa, principalmente del cambio de uso del suelo. El objetivo de la investigación fue evaluar la respiración del suelo en diferentes usos y cuantificar las emisiones de CO2 en dos diferentes momentos del año, así como estimar el almacén de este para hacer un balance que permita establecer estrategias que ayuden con la mitigación del cambio climático. Mediante una cámara dinámica cerrada colocada en el suelo e integrada con un analizador de gas infrarrojo se midió la emisión de CO2 cada 30 min, así como temperatura y humedad del suelo con sensores. Se analizaron tres usos del suelo (agroforestal, forestal y agrícola) y dos temporadas del año (verano e invierno) durante 24 horas continuas en cada en sitio. Se encontró que existe correlación positiva entre temperatura ambiental y respiración del suelo. El sistema agrícola almacena bajo contenido de carbono en el suelo (50,31 t C ha-1) y libera hasta 9,28 t de C ha-1 en la temporada de mayor temperatura, en contraste con un sistema natural que emite 3,98 t de C ha-1 y almacena 198,90 t de C ha-1. El balance refleja la necesidad de conocer las emisiones de CO2 a la atmósfera por los suelos y no sólo los almacenes. Contar con soporte científico desde la respiración del suelo a la atmósfera es un paso importante para la toma de decisiones que contribuyan a la mitigación del cambio climático.O solo, além de ser armazenado, é uma fonte de CO2 para a atmosfera emitida pela respiração do solo, principalmente devido à mudança de uso do solo. O objectivo da investigação era avaliar a respiração do solo em diferentes usos e quantificar as emissões de CO2 em dois momentos diferentes do ano, bem como estimar o seu armazenamento para fazer um balanço que permita estabelecer estratégias que ajudem a mitigar as alterações climáticas. Utilizando uma câmara dinâmica fechada colocada no solo e integrada com um analisador de gases infravermelhos, as emissões de CO2 foram medidas a cada 30 minutos, bem como a temperatura e humidade do solo com sensores. Três utilizações da terra (agroflorestação, silvicultura e agricultura) e duas estações (Verão e Inverno) foram analisadas continuamente durante 24 horas em cada local. Verificou-se que existe uma correlação positiva entre a temperatura ambiental e a respiração do solo. O sistema agrícola armazena baixo carbono no solo (50,31 t C ha-1 ) e liberta até 9,28 t C ha-1 na estação de temperaturas mais elevadas, em contraste com um sistema natural que emite 3,98 t C ha-1 e armazena 198,90 t C ha-1. O equilíbrio reflecte a necessidade de conhecer as emissões de CO2 para a atmosfera provenientes do solo e não apenas das instalações de armazenamento. Ter apoio científico do solo para a atmosfera é um passo importante na tomada de decisões que contribuem para a mitigação das alterações climáticas
Caracterización del índice de aridez en México usando dos alternativas de estimación de la evapotranspiración potencial y escenarios de cambio climático
Full text linkPonencia presentada en: VIII Congreso de la Asociación Española de Climatología celebrado en Salamanca entre el 25 y el 28 de septiembre de 2012.[ES]Se delimitaron las Áreas de Influencia Climática (AIC) para todo el territorio de México
mediante la sobreposición de las capas de precipitación (P) y temperatura (T) media anual
delimitadas a escala 1:250 000 con una herramienta de un Sistema de Información Geográfica. Para
cada AIC se generaron las bases de datos mensuales de variables climáticas y se estimó la
Evapotranspiración Potencial (ETP) por dos metodologías: a) Thorthwaite modificado por Dunne
y Leopold y b) Penman modificado por Monteith. Se calculó el Índice de Aridez (IA) a partir de la
relación P/ETP para el escenario base (promedio de 1970 a 2000) usando los valores de ETP
calculados por los dos métodos indicados. Asimismo, en cada AIC a las variables climáticas
mensuales se aplicaron las razones de cambio de los modelos generales de circulación atmosférica
GFDLCM 2.0 y el HADGEM 1, en el escenario A2 para el horizonte de tiempo al 2050 y se
estimaron los respectivos IA con los valores de P y ETP obtenidos. Se elaboraron los mapas y las
bases de datos del IA para el escenario base y cada uno de los escenarios de cambio climático
mencionados, agrupando este parámetro en cuatro categorías (Áridos, Semiáridos, Subhúmedos
secos y Subhúmedos húmedos y húmedos).[EN]The Areas of Climatic Influence (ACI) were delimitated for the entire Mexican territory by
overlapping the shape files of mean annual precipitation (P) and mean annual temperature (T) that
were previously delimited at 1: 250 000 scale using a Geographic Information System. For each ACI
a monthly climatic variables data base were generated and then estimated the Potential
Evapotranspiration (PET) using two methodologies a) the Thornthwaite modified by Dunne y
Leopold and b) the Penman modified by Monteith. The Aridity Index (AI) was calculated using the
ratio of P/PET for the base scenario (climatic variables averages from 1970 to 2000), for each ACI
two AI were estimated one for the Thorntwaite PET and the other for Penman PET. Also, for each
ACI were obtained the change ratios of the climatic variables by the Atmospheric General
Circulation Models GFDLCM 2.0 and HADGEM 1, for the scenario A2 to the year 2050. Those
change ratios were applied to the climatic variables in each ACI and calculated the PET for the two
methodologies described and with the new values of P and PET the AI were estimated. The AI
maps for the base scenario and the ones calculated for each climate change scenario were constructed, grouping the AI into four categories (Arid, Semiarid, Sub humid dry and Sub humid
moist and humids)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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