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Search Results: 1 - 10 of 146819 matches for " THOMAS T VEBLEN "
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Temperature and foliage quality affect performance of the outbreak defoliator Ormiscodes amphimone (F.) (Lepidoptera: Saturniidae) in northwestern Patagonia, Argentina
PARITSIS,JUAN; VEBLEN,THOMAS T;
Revista chilena de historia natural , 2010, DOI: 10.4067/S0716-078X2010000400012
Abstract: in the temperate forests of chile and argentina the phytophagous moth ormiscodes amphimone (f.) causes severe defoliation on the southern beech tree nothofagus pumilio (poepp. & endl.) krasser. the recent increase in defoliation frequency in some áreas appears to be influenced by a warmer climate. to evalúate the effects of temperature and the spatial heterogeneity of foliage quality on the performance and relative consumption rate of o. amphimone in northwestern patagonia, argentina we conducted a factorial experiment. larval performance was measured as relative growth rate, developmental time, larval survival, and pupal weight. larvae of o. amphimone were reared under two constant temperature regimes (15 °c and 20 °c) and fed with two n. pumilio foliage types (from a mesic and from a xeric site). larvae at the higher temperature and fed with leaves from the mesic site showed higher performance and consumption rate than larvae in the other treatments. higher temperature and mesic foliage had positive effects on o. amphimone's relative growth rate, development time and relative consumption rate. however, pupal weight was positively influenced by mesic foliage but not by temperature, and larval survival did not show significant differences among treatments. our results preliminarily suggest that o. amphimone performance and consumption rate may increase under higher temperature conditions, especially in the mesic portions of the precipitation gradient. however, these findings should be carefully interpreted as further research is necessary to assess the influence of higher temperatures on the foliar quality of n. pumilio.
Temperature and foliage quality affect performance of the outbreak defoliator Ormiscodes amphimone (F.) (Lepidoptera: Saturniidae) in northwestern Patagonia, Argentina La temperatura y la calidad del follaje afectan el desempe o del defoliador epidémico Ormiscodes amphimone (F.) (Lepidoptera: Saturniidae) en el noroeste de la Patagonia argentina
JUAN PARITSIS,THOMAS T VEBLEN
Revista chilena de historia natural , 2010,
Abstract: In the temperate forests of Chile and Argentina the phytophagous moth Ormiscodes amphimone (F.) causes severe defoliation on the southern beech tree Nothofagus pumilio (Poepp. & Endl.) Krasser. The recent increase in defoliation frequency in some áreas appears to be influenced by a warmer climate. To evalúate the effects of temperature and the spatial heterogeneity of foliage quality on the performance and relative consumption rate of O. amphimone in northwestern Patagonia, Argentina we conducted a factorial experiment. Larval performance was measured as relative growth rate, developmental time, larval survival, and pupal weight. Larvae of O. amphimone were reared under two constant temperature regimes (15 °C and 20 °C) and fed with two N. pumilio foliage types (from a mesic and from a xeric site). Larvae at the higher temperature and fed with leaves from the mesic site showed higher performance and consumption rate than larvae in the other treatments. Higher temperature and mesic foliage had positive effects on O. amphimone's relative growth rate, development time and relative consumption rate. However, pupal weight was positively influenced by mesic foliage but not by temperature, and larval survival did not show significant differences among treatments. Our results preliminarily suggest that O. amphimone performance and consumption rate may increase under higher temperature conditions, especially in the mesic portions of the precipitation gradient. However, these findings should be carefully interpreted as further research is necessary to assess the influence of higher temperatures on the foliar quality of N. pumilio. En los bosques templados de Chile y Argentina la polilla fitófaga Ormiscodes amphimone (F.) genera severas defoliaciones sobre la lenga (Nothofagus pumilio [Poepp. & Endl.] Krasser). El reciente aumento en la frecuencia de defoliación en algunas áreas de la Patagonia parecería estar influenciada por un clima más cálido. Para evaluar los efectos de la temperatura y la heterogeneidad espacial en la calidad del follaje sobre el desempe o y la tasa de consumo relativo del defoliador O. amphimone en el noroeste de la Patagonia argentina llevamos a cabo un experimento factorial. El desempe o larval fue medido como tasa de crecimiento relativo, tiempo de desarrollo, supervivencia larval y peso de las pupas. Las larvas de O. amphimone fueron criadas bajo dos temperaturas constantes (15 °C y 20 °C) y alimentadas con dos tipos de follaje de N. pumilio (de un sitio mésico y de uno xérico). Las larvas criadas a la temperatura más alta y alimentadas
Incendios en bosques de Araucaria araucana y consideraciones ecológicas al madereo de aprovechamiento en áreas recientemente quemadas
GONZáLEZ,MAURO E; VEBLEN,THOMAS T;
Revista chilena de historia natural , 2007, DOI: 10.4067/S0716-078X2007000200009
Abstract: fire is the most important kind of disturbance shaping the araucaria araucana forest landscapes of south-central chile and argentina. in the araucarian region, climate and humans have influenced historical fire regimes over many centuries. in the summer of 2002 widespread, severe fires burned in chilean araucaria forests and became the center of much interest among politicians, scientists and the general public. the 2002 fires focused attention on the importance of understanding the causes and effects of such severe events in the forest ecosystems. major wildfires generate large quantities of dead and downed trees, and promote the development of other structural attributes known as biological legacies that play critical roles in ecosystem recovery after such events. the potential for severe fire, either of natural or human origin, create pressures to either replace native forests with plantations of fast-growing exotic trees or to conduct salvage logging. salvage harvesting can impede or alter the trajectory of recovery of affected areas, and it potentially may decrease forest regeneration and have detrimental impacts on key ecological processes. forest policy and management decisions should be informed by a better understanding of the past occurrence of fire and its role in shaping the modern araucaria forest ecosystem. particularly, in the context of the exceptional ecological and cultural value of these ecosystems, managers should consider policies that effectively secure and are consistent with the restoration of the key attributes and processes of araucaria forest ecosystems
Incendios en bosques de Araucaria araucana y consideraciones ecológicas al madereo de aprovechamiento en áreas recientemente quemadas Wildfire in Araucaria araucana forests and ecological considerations about salvage logging in areas recently burned
MAURO E GONZáLEZ,THOMAS T VEBLEN
Revista chilena de historia natural , 2007,
Abstract: El fuego es el tipo de disturbio más importante en conformar el paisaje forestal de Araucaria araucana en la zona centro-sur de Chile y Argentina. En la Región de la Araucanía el clima y el ser humano han influenciado el régimen de fuego durante al menos los últimos mil a os. Los incendios catastróficos ocurridos recientemente (a o 2002) que afectaron los bosques de Araucaria atrajeron la atención pública, política y científica generando una importante necesidad de entender las causas y efectos de tales eventos en los ecosistemas forestales. Estos grandes incendios produjeron una abundante cantidad de material muerto en pie y en el suelo, promoviendo el desarrollo de otros atributos estructurales conocidos como legados biológicos que tienen un rol crítico en la recuperación de los ecosistemas luego de este tipo de eventos. El madereo de aprovechamiento ("salvage logging") es considerado un factor negativo en la recuperación de áreas afectadas significando tanto una pérdida o menoscabo de la capacidad de regeneración como un deterioro en otros procesos ecológicos clave. Incendios catastróficos de alta severidad, ya sea antrópicos o naturales, crean presiones tanto para reemplazar el bosque nativo por plantaciones de especies de crecimiento rápido o llevar a cabo operación de madereo de aprovechamiento. Las decisiones de manejo deben estar basadas en un mejor entendimiento de la ocurrencia pasada de incendios y su rol en modelar los presentes ecosistemas de Araucaria. Particularmente, en el contexto del excepcional valor ecológico y cultural de estos ecosistemas, las agencias y profesionales del manejo forestal deberían considerar políticas que efectivamente aseguren y sean consistentes con la restauración de procesos ecológicos y atributos clave en los ecosistemas de Araucaria Fire is the most important kind of disturbance shaping the Araucaria araucana forest landscapes of south-central Chile and Argentina. In the Araucarian region, climate and humans have influenced historical fire regimes over many centuries. In the summer of 2002 widespread, severe fires burned in Chilean Araucaria forests and became the center of much interest among politicians, scientists and the general public. The 2002 fires focused attention on the importance of understanding the causes and effects of such severe events in the forest ecosystems. Major wildfires generate large quantities of dead and downed trees, and promote the development of other structural attributes known as biological legacies that play critical roles in ecosystem recovery after such events. The potential f
Mortality of the outbreak defoliator Ormiscodes amphimone (Lepidoptera: Saturniidae) caused by natural enemies in northwestern Patagonia, Argentina
PARITSIS,JUAN; QUINTERO,CAROLINA; KITZBERGER,THOMAS; VEBLEN,THOMAS T;
Revista chilena de historia natural , 2012, DOI: 10.4067/S0716-078X2012000100009
Abstract: outbreaks of the defoliator moth ormiscodes amphimone are occurring more frequently in numerous nothofagus forests of patagonia. however, little is known about the life history of this species including its natural enemies as mortality agents. in this work we quantified mortality by parasitoids and generalist predators at the egg, larval and pupal life stages of o. amphimone in a nothofagus pumilio (poepp. & endl.) krasser forest in northwestern patagonia. parasitism of eggs was relatively low (ca. 11 %), and we did not record significant larval predation by insectivorous birds. however, we recorded elevated mortality caused by larval parasitoids (ca. 50 % in third instar larvae) and pupal predators (ca. 75 %), which suggests that these natural enemies could play a significant role in regulating o. amphimone populations. our research is an initial step towards understanding the influence of natural enemies on o. amphimone population dynamics.
Mortality of the outbreak defoliator Ormiscodes amphimone (Lepidoptera: Saturniidae) caused by natural enemies in northwestern Patagonia, Argentina Mortalidad del defoliador epidémico Ormiscodes amphimone (Lepidoptera: Saturniidae) causada por enemigos naturales en el noroeste de la Patagonia Argentina
JUAN PARITSIS,CAROLINA QUINTERO,THOMAS KITZBERGER,THOMAS T VEBLEN
Revista chilena de historia natural , 2012,
Abstract: Outbreaks of the defoliator moth Ormiscodes amphimone are occurring more frequently in numerous Nothofagus forests of Patagonia. However, little is known about the life history of this species including its natural enemies as mortality agents. In this work we quantified mortality by parasitoids and generalist predators at the egg, larval and pupal life stages of O. amphimone in a Nothofagus pumilio (Poepp. & Endl.) Krasser forest in northwestern Patagonia. Parasitism of eggs was relatively low (ca. 11 %), and we did not record significant larval predation by insectivorous birds. However, we recorded elevated mortality caused by larval parasitoids (ca. 50 % in third instar larvae) and pupal predators (ca. 75 %), which suggests that these natural enemies could play a significant role in regulating O. amphimone populations. Our research is an initial step towards understanding the influence of natural enemies on O. amphimone population dynamics. Las irrupciones poblacionales de la polilla defoliadora Ormiscodes amphimone están ocurriendo de manera más frecuente en numerosos bosques de Nothofagus de la Patagonia. Sin embargo, se sabe poco de la historia natural de esta especie y, particularmente, de sus enemigos naturales. En este estudio se cuantificó la depredación de huevos, larvas y pupas de O. amphimone por parasitoides y otros depredadores en un bosque de Nothofagus pumilio (Poepp. & Endl.) Krasser en el noroeste de la Patagonia. Se encontró que el parasitismo de huevos fue relativamente bajo (ca. 11 %) y no se registró depredación significativa de larvas por aves insectívoras. No obstante, registramos niveles elevados de mortalidad causada por parasitoides de larvas (ca. 50 % en larvas en tercer instar) y por depredadores de pupas (ca. 75 %), lo que parece indicar que estos enemigos naturales desempe an un papel significativo en la regulación de poblaciones de O. amphimone. Este estudio representa un paso inicial hacia el entendimiento de la influencia de los enemigos naturales de O. amphimone en la dinámica de poblaciones de esta polilla.
New host-plant records for the defoliator Ormiscodes amphimone (Fabricius) (Lepidoptera: Saturniidae)
Paritsis, Juan;Elgueta, Mario;Quintero, Carolina;Veblen, Thomas T;
Neotropical Entomology , 2010, DOI: 10.1590/S1519-566X2010000600032
Abstract: ormiscodes amphimone (fabricius) is a phytophagous moth species known to severely defoliate woody species in chile and argentina. here we document new records of o. amphimonehost associations emphasizing the role of nothofagus pumilio as its primary host in our study area. this new record for argentina is highly significant given the economic importance of n. pumilio as a timber resource and the potential of o. amphimone to generate extensive outbreaks.
Effects of Mountain Pine Beetle on Fuels and Expected Fire Behavior in Lodgepole Pine Forests, Colorado, USA
Tania Schoennagel, Thomas T. Veblen, José F. Negron, Jeremy M. Smith
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0030002
Abstract: In Colorado and southern Wyoming, mountain pine beetle (MPB) has affected over 1.6 million ha of predominantly lodgepole pine forests, raising concerns about effects of MPB-caused mortality on subsequent wildfire risk and behavior. Using empirical data we modeled potential fire behavior across a gradient of wind speeds and moisture scenarios in Green stands compared three stages since MPB attack (Red [1–3 yrs], Grey [4–10 yrs], and Old-MPB [~30 yrs]). MPB killed 50% of the trees and 70% of the basal area in Red and Grey stages. Across moisture scenarios, canopy fuel moisture was one-third lower in Red and Grey stages compared to the Green stage, making active crown fire possible at lower wind speeds and less extreme moisture conditions. More-open canopies and high loads of large surface fuels due to treefall in Grey and Old-MPB stages significantly increased surface fireline intensities, facilitating active crown fire at lower wind speeds (>30–55 km/hr) across all moisture scenarios. Not accounting for low foliar moistures in Red and Grey stages, and large surface fuels in Grey and Old-MPB stages, underestimates the occurrence of active crown fire. Under extreme burning conditions, minimum wind speeds for active crown fire were 25–35 km/hr lower for Red, Grey and Old-MPB stands compared to Green. However, if transition to crown fire occurs (outside the stand, or within the stand via ladder fuels or wind gusts >65 km/hr), active crown fire would be sustained at similar wind speeds, suggesting observed fire behavior may not be qualitatively different among MPB stages under extreme burning conditions. Overall, the risk (probability) of active crown fire appears elevated in MPB-affected stands, but the predominant fire hazard (crown fire) is similar across MPB stages and is characteristic of lodgepole pine forests where extremely dry, gusty weather conditions are key factors in determining fire behavior.
Respuesta inicial de la regeneración arbórea luego de la floración y muerte de Chusquea culeou (Poaceae) en bosques andinos del centro-sur de Chile Early response of tree regeneration after Chusquea culeou (Bambuceae) dieback in Andean old-growth forests of south-central Chile
Ariel A Mu?oz,Mauro E González,Constanza Celedón,Thomas T Veblen
Bosque (Valdivia) , 2012,
Abstract: En bosques templados lluviosos (> 600 m s.n.m.) de Sudamérica la bambúcea Chusquea culeou (colihue) es la especie dominante del sotobosque. Su floración y muerte puede generar una oportunidad para el establecimiento o crecimiento de la regeneración arbórea, especialmente en claros del dosel. En este estudio fue evaluado el efecto de esta alteración endógena sobre el establecimiento de especies arbóreas y el crecimiento de la regeneración avanzada en claros de dos bosques primarios -uno dominado por Nothofagus dombeyi-Saxegothaea conspicua-Dasyphyllum diacantoides y el otro dominado por Araucaria araucana-Nothofagus-, ubicados en la cordillera andina del centro-sur de Chile. En cada bosque (San Pablo de Tregua y Quetrupillán), entre los a os 2001-2003 se registró el establecimiento del colihue post-floración y los cambios demográficos y el crecimiento de la regeneración arbórea en claros con colihue vivo y muerto. En ambos bosques, la mortalidad de la regeneración avanzada fue superior en claros con colihue muerto. Solamente en San Pablo de Tregua el crecimiento en altura de Saxegothaea conspicua fue mayor en claros con colihue muerto. El establecimiento de individuos post-floración fue bajo, sin presentar diferencias entre condiciones. El reclutamiento de plántulas de colihue fue superior en claros con colihue muerto en ambos bosques, siendo el patrón más claro de respuesta ante el evento de su propia muerte. La muerte del colihue puede favorecer el crecimiento de la regeneración avanzada pero sin representar una gran oportunidad para el establecimiento de especies arbóreas en estos bosques. In temperate rainforests at mid-elevation (> 600 m a.s.l.) in South-America the Chusquea culeou bamboo (colihue) is the dominant understory species and potentially can impede tree regeneration. Dieback of colihue subsequent to its gregarious flowering may result in an opportunity for tree establishment or growth release of previously suppressed juvenile trees, especially in canopy gaps. In this research we evaluated the bamboo dieback effect on tree species establishment and advance regeneration growth in two old-growth forests. The first forest is dominated by Nothofagus dombeyi-Saxegothaea-conspicua-Dasyphyllum diacantoides and the second is dominated by Araucaria araucana-Nothofagus, located in the Andean Cordillera of south-central Chile. In each forest (San Pablo de Tregua and Quetrupillán) following the gregarious flowering and dieback of colihue, between 2001 and 2003, we recorded new establishment of colihue and tree demographic changes and growth of advance
Examining Historical and Current Mixed-Severity Fire Regimes in Ponderosa Pine and Mixed-Conifer Forests of Western North America
Dennis C. Odion, Chad T. Hanson, André Arsenault, William L. Baker, Dominick A. DellaSala, Richard L. Hutto, Walt Klenner, Max A. Moritz, Rosemary L. Sherriff, Thomas T. Veblen, Mark A. Williams
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0087852
Abstract: There is widespread concern that fire exclusion has led to an unprecedented threat of uncharacteristically severe fires in ponderosa pine (Pinus ponderosa Dougl. ex. Laws) and mixed-conifer forests of western North America. These extensive montane forests are considered to be adapted to a low/moderate-severity fire regime that maintained stands of relatively old trees. However, there is increasing recognition from landscape-scale assessments that, prior to any significant effects of fire exclusion, fires and forest structure were more variable in these forests. Biota in these forests are also dependent on the resources made available by higher-severity fire. A better understanding of historical fire regimes in the ponderosa pine and mixed-conifer forests of western North America is therefore needed to define reference conditions and help maintain characteristic ecological diversity of these systems. We compiled landscape-scale evidence of historical fire severity patterns in the ponderosa pine and mixed-conifer forests from published literature sources and stand ages available from the Forest Inventory and Analysis program in the USA. The consensus from this evidence is that the traditional reference conditions of low-severity fire regimes are inaccurate for most forests of western North America. Instead, most forests appear to have been characterized by mixed-severity fire that included ecologically significant amounts of weather-driven, high-severity fire. Diverse forests in different stages of succession, with a high proportion in relatively young stages, occurred prior to fire exclusion. Over the past century, successional diversity created by fire decreased. Our findings suggest that ecological management goals that incorporate successional diversity created by fire may support characteristic biodiversity, whereas current attempts to “restore” forests to open, low-severity fire conditions may not align with historical reference conditions in most ponderosa pine and mixed-conifer forests of western North America.
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