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Jason S Sibold - One of the best experts on this subject based on the ideXlab platform.
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influence of fire severity on stand development of Araucaria araucana nothofagus pumilio stands in the andean cordillera of south central chile
Austral Ecology, 2010Co-Authors: Mauro E Gonzalez, Thomas T Veblen, Jason S SiboldAbstract:Fire is the prevalent disturbance in the Araucaria-Nothofagus forested landscape in south-central Chile. Although both surface and stand-replacing fires are known to characterize these ecosystems, the variability of fire severity in shaping forest structure has not previously been investigated in Araucaria-Nothofagus forests. Age structures of 16 stands, in which the ages of approximately 650 trees were determined, indicate that variability in fire severity and frequency is key to explaining the mosaic of forest patches across the Araucaria-Nothofagus landscape. High levels of tree mortality in moderate- to high-severity fires followed by new establishment of Nothofagus pumilio typically result in stands characterized by one or two cohorts of this species. Large Araucaria trees are highly resistant to fire,and this species typically survives moderate- to high-severity fires either as dispersed individuals or as small groups of multi-aged trees. Small post-fire cohorts of Araucaria may establish, depending on seed availability and the effects of subsequent fires. Araucaria's great longevity (often >700 years) and resistance to fire allow some individuals to survive fires that kill and then trigger new Nothofagus cohorts. Even in relatively mesic habitats, where fires are less frequent, the oldest Araucaria-Nothofagus pumilio stands originated after high-severity fires. Overall, stand development patterns of subalpine Araucaria-N. pumilio forests are largely controlled by moderate- to high-severity fires, and therefore tree regeneration dynamics is strongly dominated by a catastrophic regeneration mode.
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fire history of Araucaria nothofagus forests in villarrica national park chile
Journal of Biogeography, 2005Co-Authors: Mauro E Gonzalez, Thomas T Veblen, Jason S SiboldAbstract:Aim In this study we examine fire history (i.e. c. 500 yr bp to present) of Araucaria–Nothofagus forests in the Andes cordillera of Chile. This is the first fire history developed from tree rings for an Araucaria–Nothofagus forest landscape. Location The fire history was determined for the Quillelhue watershed on the north side of Lanin volcano in Villarrica National Park, Chile. The long-lived Araucaria araucana was commonly associated with Nothofagus pumilio and N. antarctica in more mesic and drier sites respectively. Methods Based on a combination of fire-scar proxy records and forest stand ages, we reconstructed fire frequency, severity, and the spatial extent of burned areas for an c. 4000 ha study area. We used a composite fire chronology for the purpose of determining centennial-scale changes in fire regimes and comparing the pre-settlement (pre-1883) and post-settlement fire regimes. In addition, we contrasted Araucaria and Nothofagus species as fire-scar recorders. Results In the study area, we dated a total of 144 fire-scarred trees, representing 46 fire years from ad 1446 to the present. For the period from ad 1696 to 2000, using fire dates from Araucaria and Nothofagus species, the composite mean fire interval varied from 7 years for all fires to 62 years for widespread events (i.e. years in which ≥ 25% of recorder trees were scarred). Sensitivity to fire was different for Araucaria and Nothofagus species. More than 98% of the fires recorded by Nothofagus species occurred during the 1900s. The lack of evidence for older fire dates (pre-1900) in Nothofagus species was due to their shorter longevity and greater susceptibility to being killed by more severe fires. Whereas the thin-barked N. pumilio and N. antarctica are often destroyed in catastrophic fire events, large and thick-barked Araucaria trees typically survive. The spatial extent of fires ranged from small patchy events to those that burned more than 40% of the entire landscape (c. > 1500 ha). Main conclusions Fire is the most important disturbance shaping the Araucaria–Nothofagus landscape in the Araucarian region. The forest landscape has been shaped by a mixed-severity fire regime that includes surface and crown fires. High-severity widespread events were relatively infrequent (e.g. 1827, 1909 and 1944) and primarily affected tall Araucaria–N. pumilio forests and woodlands dominated by Araucaria–N. antarctica. Although there is abundant evidence of the impact of Euro-Chilean settlers on the area, the relative influence of this settlement on the temporal pattern of fire could only be tentatively established due to the relatively small number of pre-1900 fire dates. An apparent increase in fire occurrence is evident in the fire record during Euro-Chilean settlement (post-1880s) compared with the Native American era, but it may also be the result of the destruction of evidence of older fires by more recent stand-devastating fires (e.g. 1909 and 1944). Overall, the severe and widespread fires that burned in Araucaria–Nothofagus forests of this region in 2002, previously interpreted as an ecological novelty, are within the range of the historic fire regimes that have shaped this forested landscape.
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Fire history of Araucaria–Nothofagus forests in Villarrica National Park, Chile
Journal of Biogeography, 2005Co-Authors: Mauro E Gonzalez, Thomas T Veblen, Jason S SiboldAbstract:Aim In this study we examine fire history (i.e. c. 500 yr bp to present) of Araucaria–Nothofagus forests in the Andes cordillera of Chile. This is the first fire history developed from tree rings for an Araucaria–Nothofagus forest landscape. Location The fire history was determined for the Quillelhue watershed on the north side of Lanin volcano in Villarrica National Park, Chile. The long-lived Araucaria araucana was commonly associated with Nothofagus pumilio and N. antarctica in more mesic and drier sites respectively. Methods Based on a combination of fire-scar proxy records and forest stand ages, we reconstructed fire frequency, severity, and the spatial extent of burned areas for an c. 4000 ha study area. We used a composite fire chronology for the purpose of determining centennial-scale changes in fire regimes and comparing the pre-settlement (pre-1883) and post-settlement fire regimes. In addition, we contrasted Araucaria and Nothofagus species as fire-scar recorders. Results In the study area, we dated a total of 144 fire-scarred trees, representing 46 fire years from ad 1446 to the present. For the period from ad 1696 to 2000, using fire dates from Araucaria and Nothofagus species, the composite mean fire interval varied from 7 years for all fires to 62 years for widespread events (i.e. years in which ≥ 25% of recorder trees were scarred). Sensitivity to fire was different for Araucaria and Nothofagus species. More than 98% of the fires recorded by Nothofagus species occurred during the 1900s. The lack of evidence for older fire dates (pre-1900) in Nothofagus species was due to their shorter longevity and greater susceptibility to being killed by more severe fires. Whereas the thin-barked N. pumilio and N. antarctica are often destroyed in catastrophic fire events, large and thick-barked Araucaria trees typically survive. The spatial extent of fires ranged from small patchy events to those that burned more than 40% of the entire landscape (c. > 1500 ha). Main conclusions Fire is the most important disturbance shaping the Araucaria–Nothofagus landscape in the Araucarian region. The forest landscape has been shaped by a mixed-severity fire regime that includes surface and crown fires. High-severity widespread events were relatively infrequent (e.g. 1827, 1909 and 1944) and primarily affected tall Araucaria–N. pumilio forests and woodlands dominated by Araucaria–N. antarctica. Although there is abundant evidence of the impact of Euro-Chilean settlers on the area, the relative influence of this settlement on the temporal pattern of fire could only be tentatively established due to the relatively small number of pre-1900 fire dates. An apparent increase in fire occurrence is evident in the fire record during Euro-Chilean settlement (post-1880s) compared with the Native American era, but it may also be the result of the destruction of evidence of older fires by more recent stand-devastating fires (e.g. 1909 and 1944). Overall, the severe and widespread fires that burned in Araucaria–Nothofagus forests of this region in 2002, previously interpreted as an ecological novelty, are within the range of the historic fire regimes that have shaped this forested landscape.
Mauro E Gonzalez - One of the best experts on this subject based on the ideXlab platform.
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influence of fire severity on stand development of Araucaria araucana nothofagus pumilio stands in the andean cordillera of south central chile
Austral Ecology, 2010Co-Authors: Mauro E Gonzalez, Thomas T Veblen, Jason S SiboldAbstract:Fire is the prevalent disturbance in the Araucaria-Nothofagus forested landscape in south-central Chile. Although both surface and stand-replacing fires are known to characterize these ecosystems, the variability of fire severity in shaping forest structure has not previously been investigated in Araucaria-Nothofagus forests. Age structures of 16 stands, in which the ages of approximately 650 trees were determined, indicate that variability in fire severity and frequency is key to explaining the mosaic of forest patches across the Araucaria-Nothofagus landscape. High levels of tree mortality in moderate- to high-severity fires followed by new establishment of Nothofagus pumilio typically result in stands characterized by one or two cohorts of this species. Large Araucaria trees are highly resistant to fire,and this species typically survives moderate- to high-severity fires either as dispersed individuals or as small groups of multi-aged trees. Small post-fire cohorts of Araucaria may establish, depending on seed availability and the effects of subsequent fires. Araucaria's great longevity (often >700 years) and resistance to fire allow some individuals to survive fires that kill and then trigger new Nothofagus cohorts. Even in relatively mesic habitats, where fires are less frequent, the oldest Araucaria-Nothofagus pumilio stands originated after high-severity fires. Overall, stand development patterns of subalpine Araucaria-N. pumilio forests are largely controlled by moderate- to high-severity fires, and therefore tree regeneration dynamics is strongly dominated by a catastrophic regeneration mode.
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climatic influences on fire in Araucaria araucana nothofagus forests in the andean cordillera of south central chile
Ecoscience, 2006Co-Authors: Mauro E Gonzalez, Thomas T VeblenAbstract:ABSTRACT Tree-ring records of fires were used to examine the effects of inter-annual climatic variability on fire occurrence in forests dominated by the fire-adapted Araucaria araucana in the Andes of south-central Chile. Instrumental as well as tree-ring proxy records of climate indicate that low moisture availability is the main factor influencing fire occurrence. Years of widespread fire are strongly associated with warmer and drier summers. Years of extensive fire also tend to be favoured by one or two preceding years of dry climatic conditions. The El Nino–Southern Oscillation (ENSO) and its strong influence over large-scale climatic features is an important factor promoting fire activity. Years of high fire activity coincide with warm and dry summers following El Nino events. Fire in the Araucarian region is strongly related to inter-annual climatic variation associated primarily with the coupled effect of ENSO events and variations in the intensity and latitudinal position of the southeast Pacific ...
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fire history of Araucaria nothofagus forests in villarrica national park chile
Journal of Biogeography, 2005Co-Authors: Mauro E Gonzalez, Thomas T Veblen, Jason S SiboldAbstract:Aim In this study we examine fire history (i.e. c. 500 yr bp to present) of Araucaria–Nothofagus forests in the Andes cordillera of Chile. This is the first fire history developed from tree rings for an Araucaria–Nothofagus forest landscape. Location The fire history was determined for the Quillelhue watershed on the north side of Lanin volcano in Villarrica National Park, Chile. The long-lived Araucaria araucana was commonly associated with Nothofagus pumilio and N. antarctica in more mesic and drier sites respectively. Methods Based on a combination of fire-scar proxy records and forest stand ages, we reconstructed fire frequency, severity, and the spatial extent of burned areas for an c. 4000 ha study area. We used a composite fire chronology for the purpose of determining centennial-scale changes in fire regimes and comparing the pre-settlement (pre-1883) and post-settlement fire regimes. In addition, we contrasted Araucaria and Nothofagus species as fire-scar recorders. Results In the study area, we dated a total of 144 fire-scarred trees, representing 46 fire years from ad 1446 to the present. For the period from ad 1696 to 2000, using fire dates from Araucaria and Nothofagus species, the composite mean fire interval varied from 7 years for all fires to 62 years for widespread events (i.e. years in which ≥ 25% of recorder trees were scarred). Sensitivity to fire was different for Araucaria and Nothofagus species. More than 98% of the fires recorded by Nothofagus species occurred during the 1900s. The lack of evidence for older fire dates (pre-1900) in Nothofagus species was due to their shorter longevity and greater susceptibility to being killed by more severe fires. Whereas the thin-barked N. pumilio and N. antarctica are often destroyed in catastrophic fire events, large and thick-barked Araucaria trees typically survive. The spatial extent of fires ranged from small patchy events to those that burned more than 40% of the entire landscape (c. > 1500 ha). Main conclusions Fire is the most important disturbance shaping the Araucaria–Nothofagus landscape in the Araucarian region. The forest landscape has been shaped by a mixed-severity fire regime that includes surface and crown fires. High-severity widespread events were relatively infrequent (e.g. 1827, 1909 and 1944) and primarily affected tall Araucaria–N. pumilio forests and woodlands dominated by Araucaria–N. antarctica. Although there is abundant evidence of the impact of Euro-Chilean settlers on the area, the relative influence of this settlement on the temporal pattern of fire could only be tentatively established due to the relatively small number of pre-1900 fire dates. An apparent increase in fire occurrence is evident in the fire record during Euro-Chilean settlement (post-1880s) compared with the Native American era, but it may also be the result of the destruction of evidence of older fires by more recent stand-devastating fires (e.g. 1909 and 1944). Overall, the severe and widespread fires that burned in Araucaria–Nothofagus forests of this region in 2002, previously interpreted as an ecological novelty, are within the range of the historic fire regimes that have shaped this forested landscape.
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Fire history of Araucaria–Nothofagus forests in Villarrica National Park, Chile
Journal of Biogeography, 2005Co-Authors: Mauro E Gonzalez, Thomas T Veblen, Jason S SiboldAbstract:Aim In this study we examine fire history (i.e. c. 500 yr bp to present) of Araucaria–Nothofagus forests in the Andes cordillera of Chile. This is the first fire history developed from tree rings for an Araucaria–Nothofagus forest landscape. Location The fire history was determined for the Quillelhue watershed on the north side of Lanin volcano in Villarrica National Park, Chile. The long-lived Araucaria araucana was commonly associated with Nothofagus pumilio and N. antarctica in more mesic and drier sites respectively. Methods Based on a combination of fire-scar proxy records and forest stand ages, we reconstructed fire frequency, severity, and the spatial extent of burned areas for an c. 4000 ha study area. We used a composite fire chronology for the purpose of determining centennial-scale changes in fire regimes and comparing the pre-settlement (pre-1883) and post-settlement fire regimes. In addition, we contrasted Araucaria and Nothofagus species as fire-scar recorders. Results In the study area, we dated a total of 144 fire-scarred trees, representing 46 fire years from ad 1446 to the present. For the period from ad 1696 to 2000, using fire dates from Araucaria and Nothofagus species, the composite mean fire interval varied from 7 years for all fires to 62 years for widespread events (i.e. years in which ≥ 25% of recorder trees were scarred). Sensitivity to fire was different for Araucaria and Nothofagus species. More than 98% of the fires recorded by Nothofagus species occurred during the 1900s. The lack of evidence for older fire dates (pre-1900) in Nothofagus species was due to their shorter longevity and greater susceptibility to being killed by more severe fires. Whereas the thin-barked N. pumilio and N. antarctica are often destroyed in catastrophic fire events, large and thick-barked Araucaria trees typically survive. The spatial extent of fires ranged from small patchy events to those that burned more than 40% of the entire landscape (c. > 1500 ha). Main conclusions Fire is the most important disturbance shaping the Araucaria–Nothofagus landscape in the Araucarian region. The forest landscape has been shaped by a mixed-severity fire regime that includes surface and crown fires. High-severity widespread events were relatively infrequent (e.g. 1827, 1909 and 1944) and primarily affected tall Araucaria–N. pumilio forests and woodlands dominated by Araucaria–N. antarctica. Although there is abundant evidence of the impact of Euro-Chilean settlers on the area, the relative influence of this settlement on the temporal pattern of fire could only be tentatively established due to the relatively small number of pre-1900 fire dates. An apparent increase in fire occurrence is evident in the fire record during Euro-Chilean settlement (post-1880s) compared with the Native American era, but it may also be the result of the destruction of evidence of older fires by more recent stand-devastating fires (e.g. 1909 and 1944). Overall, the severe and widespread fires that burned in Araucaria–Nothofagus forests of this region in 2002, previously interpreted as an ecological novelty, are within the range of the historic fire regimes that have shaped this forested landscape.
Sergio Archangelsky - One of the best experts on this subject based on the ideXlab platform.
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A new Araucarian pollen cone with in situ Cyclusphaera Elsik from the Aptian of Patagonia, Argentina
Cretaceous Research, 2005Co-Authors: Georgina M Del Fueyo, Sergio ArchangelskyAbstract:Abstract A new Araucarian pollen cone Alkastrobus peltatus gen. et sp. nov. is described from the Anfiteatro de Tico Formation (Baquero Group) of Aptian age in Santa Cruz province, Argentina. The pollen cones are mostly compressions and their microsporangia contain the well-known Cyclusphaera Elsik pollen. The morphology, anatomy and ultrastructure of the pollen cones along with the pollen grains were examined under light, scanning and transmission electron microscopy. An affinity with the Araucariaceae is established on the basis of microsporophyll anatomy and morphology, and comparison of Cyclusphaera with other Araucarian pollen grains. In Patagonia during the Cretaceous Period, plants producing Araucariacites, Balmeiopsis and Cyclusphaera pollen lived together. All three types of pollen are found inside microsporangia. Araucariacites, the only type that has survived to the present day, is found in the extant genera Araucaria and Agathis. The new genus confirms the broad diversity that Araucariaceae attained during the Early Cretaceous within western Gondwana.
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A new Araucarian pollen cone with in situ Cyclusphaera Elsik from the Aptian of Patagonia, Argentina
Cretaceous Research, 2005Co-Authors: Georgina M Del Fueyo, Sergio ArchangelskyAbstract:Abstract A new Araucarian pollen cone Alkastrobus peltatus gen. et sp. nov. is described from the Anfiteatro de Tico Formation (Baquero Group) of Aptian age in Santa Cruz province, Argentina. The pollen cones are mostly compressions and their microsporangia contain the well-known Cyclusphaera Elsik pollen. The morphology, anatomy and ultrastructure of the pollen cones along with the pollen grains were examined under light, scanning and transmission electron microscopy. An affinity with the Araucariaceae is established on the basis of microsporophyll anatomy and morphology, and comparison of Cyclusphaera with other Araucarian pollen grains. In Patagonia during the Cretaceous Period, plants producing Araucariacites, Balmeiopsis and Cyclusphaera pollen lived together. All three types of pollen are found inside microsporangia. Araucariacites, the only type that has survived to the present day, is found in the extant genera Araucaria and Agathis. The new genus confirms the broad diversity that Araucariaceae attained during the Early Cretaceous within western Gondwana.
Thomas T Veblen - One of the best experts on this subject based on the ideXlab platform.
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influence of fire severity on stand development of Araucaria araucana nothofagus pumilio stands in the andean cordillera of south central chile
Austral Ecology, 2010Co-Authors: Mauro E Gonzalez, Thomas T Veblen, Jason S SiboldAbstract:Fire is the prevalent disturbance in the Araucaria-Nothofagus forested landscape in south-central Chile. Although both surface and stand-replacing fires are known to characterize these ecosystems, the variability of fire severity in shaping forest structure has not previously been investigated in Araucaria-Nothofagus forests. Age structures of 16 stands, in which the ages of approximately 650 trees were determined, indicate that variability in fire severity and frequency is key to explaining the mosaic of forest patches across the Araucaria-Nothofagus landscape. High levels of tree mortality in moderate- to high-severity fires followed by new establishment of Nothofagus pumilio typically result in stands characterized by one or two cohorts of this species. Large Araucaria trees are highly resistant to fire,and this species typically survives moderate- to high-severity fires either as dispersed individuals or as small groups of multi-aged trees. Small post-fire cohorts of Araucaria may establish, depending on seed availability and the effects of subsequent fires. Araucaria's great longevity (often >700 years) and resistance to fire allow some individuals to survive fires that kill and then trigger new Nothofagus cohorts. Even in relatively mesic habitats, where fires are less frequent, the oldest Araucaria-Nothofagus pumilio stands originated after high-severity fires. Overall, stand development patterns of subalpine Araucaria-N. pumilio forests are largely controlled by moderate- to high-severity fires, and therefore tree regeneration dynamics is strongly dominated by a catastrophic regeneration mode.
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climatic influences on fire in Araucaria araucana nothofagus forests in the andean cordillera of south central chile
Ecoscience, 2006Co-Authors: Mauro E Gonzalez, Thomas T VeblenAbstract:ABSTRACT Tree-ring records of fires were used to examine the effects of inter-annual climatic variability on fire occurrence in forests dominated by the fire-adapted Araucaria araucana in the Andes of south-central Chile. Instrumental as well as tree-ring proxy records of climate indicate that low moisture availability is the main factor influencing fire occurrence. Years of widespread fire are strongly associated with warmer and drier summers. Years of extensive fire also tend to be favoured by one or two preceding years of dry climatic conditions. The El Nino–Southern Oscillation (ENSO) and its strong influence over large-scale climatic features is an important factor promoting fire activity. Years of high fire activity coincide with warm and dry summers following El Nino events. Fire in the Araucarian region is strongly related to inter-annual climatic variation associated primarily with the coupled effect of ENSO events and variations in the intensity and latitudinal position of the southeast Pacific ...
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fire history of Araucaria nothofagus forests in villarrica national park chile
Journal of Biogeography, 2005Co-Authors: Mauro E Gonzalez, Thomas T Veblen, Jason S SiboldAbstract:Aim In this study we examine fire history (i.e. c. 500 yr bp to present) of Araucaria–Nothofagus forests in the Andes cordillera of Chile. This is the first fire history developed from tree rings for an Araucaria–Nothofagus forest landscape. Location The fire history was determined for the Quillelhue watershed on the north side of Lanin volcano in Villarrica National Park, Chile. The long-lived Araucaria araucana was commonly associated with Nothofagus pumilio and N. antarctica in more mesic and drier sites respectively. Methods Based on a combination of fire-scar proxy records and forest stand ages, we reconstructed fire frequency, severity, and the spatial extent of burned areas for an c. 4000 ha study area. We used a composite fire chronology for the purpose of determining centennial-scale changes in fire regimes and comparing the pre-settlement (pre-1883) and post-settlement fire regimes. In addition, we contrasted Araucaria and Nothofagus species as fire-scar recorders. Results In the study area, we dated a total of 144 fire-scarred trees, representing 46 fire years from ad 1446 to the present. For the period from ad 1696 to 2000, using fire dates from Araucaria and Nothofagus species, the composite mean fire interval varied from 7 years for all fires to 62 years for widespread events (i.e. years in which ≥ 25% of recorder trees were scarred). Sensitivity to fire was different for Araucaria and Nothofagus species. More than 98% of the fires recorded by Nothofagus species occurred during the 1900s. The lack of evidence for older fire dates (pre-1900) in Nothofagus species was due to their shorter longevity and greater susceptibility to being killed by more severe fires. Whereas the thin-barked N. pumilio and N. antarctica are often destroyed in catastrophic fire events, large and thick-barked Araucaria trees typically survive. The spatial extent of fires ranged from small patchy events to those that burned more than 40% of the entire landscape (c. > 1500 ha). Main conclusions Fire is the most important disturbance shaping the Araucaria–Nothofagus landscape in the Araucarian region. The forest landscape has been shaped by a mixed-severity fire regime that includes surface and crown fires. High-severity widespread events were relatively infrequent (e.g. 1827, 1909 and 1944) and primarily affected tall Araucaria–N. pumilio forests and woodlands dominated by Araucaria–N. antarctica. Although there is abundant evidence of the impact of Euro-Chilean settlers on the area, the relative influence of this settlement on the temporal pattern of fire could only be tentatively established due to the relatively small number of pre-1900 fire dates. An apparent increase in fire occurrence is evident in the fire record during Euro-Chilean settlement (post-1880s) compared with the Native American era, but it may also be the result of the destruction of evidence of older fires by more recent stand-devastating fires (e.g. 1909 and 1944). Overall, the severe and widespread fires that burned in Araucaria–Nothofagus forests of this region in 2002, previously interpreted as an ecological novelty, are within the range of the historic fire regimes that have shaped this forested landscape.
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Fire history of Araucaria–Nothofagus forests in Villarrica National Park, Chile
Journal of Biogeography, 2005Co-Authors: Mauro E Gonzalez, Thomas T Veblen, Jason S SiboldAbstract:Aim In this study we examine fire history (i.e. c. 500 yr bp to present) of Araucaria–Nothofagus forests in the Andes cordillera of Chile. This is the first fire history developed from tree rings for an Araucaria–Nothofagus forest landscape. Location The fire history was determined for the Quillelhue watershed on the north side of Lanin volcano in Villarrica National Park, Chile. The long-lived Araucaria araucana was commonly associated with Nothofagus pumilio and N. antarctica in more mesic and drier sites respectively. Methods Based on a combination of fire-scar proxy records and forest stand ages, we reconstructed fire frequency, severity, and the spatial extent of burned areas for an c. 4000 ha study area. We used a composite fire chronology for the purpose of determining centennial-scale changes in fire regimes and comparing the pre-settlement (pre-1883) and post-settlement fire regimes. In addition, we contrasted Araucaria and Nothofagus species as fire-scar recorders. Results In the study area, we dated a total of 144 fire-scarred trees, representing 46 fire years from ad 1446 to the present. For the period from ad 1696 to 2000, using fire dates from Araucaria and Nothofagus species, the composite mean fire interval varied from 7 years for all fires to 62 years for widespread events (i.e. years in which ≥ 25% of recorder trees were scarred). Sensitivity to fire was different for Araucaria and Nothofagus species. More than 98% of the fires recorded by Nothofagus species occurred during the 1900s. The lack of evidence for older fire dates (pre-1900) in Nothofagus species was due to their shorter longevity and greater susceptibility to being killed by more severe fires. Whereas the thin-barked N. pumilio and N. antarctica are often destroyed in catastrophic fire events, large and thick-barked Araucaria trees typically survive. The spatial extent of fires ranged from small patchy events to those that burned more than 40% of the entire landscape (c. > 1500 ha). Main conclusions Fire is the most important disturbance shaping the Araucaria–Nothofagus landscape in the Araucarian region. The forest landscape has been shaped by a mixed-severity fire regime that includes surface and crown fires. High-severity widespread events were relatively infrequent (e.g. 1827, 1909 and 1944) and primarily affected tall Araucaria–N. pumilio forests and woodlands dominated by Araucaria–N. antarctica. Although there is abundant evidence of the impact of Euro-Chilean settlers on the area, the relative influence of this settlement on the temporal pattern of fire could only be tentatively established due to the relatively small number of pre-1900 fire dates. An apparent increase in fire occurrence is evident in the fire record during Euro-Chilean settlement (post-1880s) compared with the Native American era, but it may also be the result of the destruction of evidence of older fires by more recent stand-devastating fires (e.g. 1909 and 1944). Overall, the severe and widespread fires that burned in Araucaria–Nothofagus forests of this region in 2002, previously interpreted as an ecological novelty, are within the range of the historic fire regimes that have shaped this forested landscape.
Georgina M Del Fueyo - One of the best experts on this subject based on the ideXlab platform.
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A new Araucarian pollen cone with in situ Cyclusphaera Elsik from the Aptian of Patagonia, Argentina
Cretaceous Research, 2005Co-Authors: Georgina M Del Fueyo, Sergio ArchangelskyAbstract:Abstract A new Araucarian pollen cone Alkastrobus peltatus gen. et sp. nov. is described from the Anfiteatro de Tico Formation (Baquero Group) of Aptian age in Santa Cruz province, Argentina. The pollen cones are mostly compressions and their microsporangia contain the well-known Cyclusphaera Elsik pollen. The morphology, anatomy and ultrastructure of the pollen cones along with the pollen grains were examined under light, scanning and transmission electron microscopy. An affinity with the Araucariaceae is established on the basis of microsporophyll anatomy and morphology, and comparison of Cyclusphaera with other Araucarian pollen grains. In Patagonia during the Cretaceous Period, plants producing Araucariacites, Balmeiopsis and Cyclusphaera pollen lived together. All three types of pollen are found inside microsporangia. Araucariacites, the only type that has survived to the present day, is found in the extant genera Araucaria and Agathis. The new genus confirms the broad diversity that Araucariaceae attained during the Early Cretaceous within western Gondwana.
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A new Araucarian pollen cone with in situ Cyclusphaera Elsik from the Aptian of Patagonia, Argentina
Cretaceous Research, 2005Co-Authors: Georgina M Del Fueyo, Sergio ArchangelskyAbstract:Abstract A new Araucarian pollen cone Alkastrobus peltatus gen. et sp. nov. is described from the Anfiteatro de Tico Formation (Baquero Group) of Aptian age in Santa Cruz province, Argentina. The pollen cones are mostly compressions and their microsporangia contain the well-known Cyclusphaera Elsik pollen. The morphology, anatomy and ultrastructure of the pollen cones along with the pollen grains were examined under light, scanning and transmission electron microscopy. An affinity with the Araucariaceae is established on the basis of microsporophyll anatomy and morphology, and comparison of Cyclusphaera with other Araucarian pollen grains. In Patagonia during the Cretaceous Period, plants producing Araucariacites, Balmeiopsis and Cyclusphaera pollen lived together. All three types of pollen are found inside microsporangia. Araucariacites, the only type that has survived to the present day, is found in the extant genera Araucaria and Agathis. The new genus confirms the broad diversity that Araucariaceae attained during the Early Cretaceous within western Gondwana.