Incendios catastróficos en bosques andinos de Araucaria-Nothofagus: efecto de la severidad y respuesta de la vegetación
Autores: Mauro E. González, Michelle Szejner, Ariel A. Muñoz y Jorge Silva.
Resumen.
En bosques quemados con una alta severidad, la mortalidad fue prácticamente total de los individuos arbóreos y especies de sotobosque, comparada con aquellos quemados con severidad moderada, donde una importante proporción del sotobosque y dosel arbóreo sobrevivió. Tres años luego del incendio, la colonización de plantas establecidas vía semillas y rebrotes vegetativos (raíces, bulbos y rizomas) ha sido relativamente rápida. Individuos de Araucaria araucana han logrado establecerse exitosamente, bajo ambas severidades, tanto por semillas como por rebrotes vegetativos de individuos jóvenes quemados.
El fuego tiene un papel fundamental en la ecología y dinámica de los ecosistemas boscosos de Araucaria-Nothofagus en la cordillera de los Andes.
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Fire history in the Araucaria araucana forests of Argentina: human and climate influences.
Autores: A. Mundo A B D, T. Kitzberger C , F. A. Roig Juñent A , R. Villalba A and M. D. Barrera B.
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Abstract.
Little is known about drivers and trends of historic fire regimes in the Araucaria araucana forests of south-western Argentina. Fire history in these forests was reconstructed by the analysis of 246 fire-scarred partial cross-sections from this fire-resistant tree collected at 10 sites in Neuquén, northern Patagonia. Fire chronologies showed an increase in fire occurrence during the nineteenth century and a sharp decrease since the early twentieth century. The creation of Lanín National Park in 1937, the change in human activities, and the active suppression of wildfires led to a significant increase in mean fire intervals since 1930. In addition to these multidecadal to centennial scale drives of fire frequency, interannual variability in wildfire activity was associated with El Niño–Southern Oscillation. Years of widespread fire are related to negative departures of both Niño 3.4 and Pacific Decadal Oscillation indexes (i.e. La Niña conditions), as well as coincident phases of positive Southern Annular Mode and La Niña events. Temporal variations in the Araucaria fire history in Argentina clearly show the combined effect of human and climate influences on fire regimes. A comparison with previous fire history studies in the Araucaria forests of Chile reveals substantial differences related to differences in human activities on both sides of the Andes and the earlier implementation of protected areas in Argentina
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Efectos combinados del fuego y el ganado en matorrales y bosques del noroeste patagónico.
Autores: Melisa Blackhall, Estela Raffaele y Thomas T. Veblen.
Resumen.
En el noroeste patagónico, dos de los disturbios de mayor influencia sobre los paisajes y comunidades son el fuego y la herbivoría de ungulados introducidos. Existe una larga historia regional del fuego, pero la reiteración de incendios seguidos de intenso pastoreo constituye un nuevo tipo de régimen de disturbio en este paisaje. Nuestro objetivo fue analizar distintas condiciones micro-ambientales y parámetros de la vegetación en sitios afectados por la combinación de ambos disturbios. Dentro del Parque Nacional Nahuel Huapi, estudiamos 17 sitios bajo la influencia del fuego y el ganado vacuno: sitios no quemados (>50 años) o recientemente quemados (<15 años); y sin ganado o con herbivoría intensa. Encontramos un efecto contundente del tiempo transcurrido desde el último incendio y en menor medida del ganado. Ambos disturbios combinados sólo mostraron un efecto sinérgico sobre la humedad (durante las horas de mayor temperatura) y sobre la disponibilidad de luz, aumentando las condiciones adversas en los sitios recientemente quemados y con ganado.
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Landscape drivers of recent fire activity (2001-2017) in south-central Chile.
David B. McWethy, Aníbal Pauchard, Rafael A. García, Andrés Holz, Mauro E. González, Thomas T. Veblen, Julian Stahl & Bryce Currey.
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Abstract.
In recent decades large fires have affected communities throughout central and southern Chile with great social and ecological consequences. Despite this high fire activity, the controls and drivers and the spatiotemporal pattern of fires are not well understood. To identify the large-scale trends and drivers of recent fire activity across six regions in south-central Chile (~32–40° S Latitude) we evaluated MODIS satellite-derived fire detections and compared this data with Chilean Forest Service records for the period 2001–2017. MODIS burned area estimates provide a spatially and temporally comprehensive record of fire activity across an important bioclimatic transition zone between dry Mediterranean shrublands/sclerophyllous forests and wetter deciduous-broadleaf evergreen forests. Results suggest fire activity was highly variable in any given year, with no statistically significant trend in the number of fires or mean annual area burned. Evaluation of the variables associated with spatiotemporal patterns of fire for the 2001–2017 period indicate vegetation type, biophysical conditions (e.g., elevation, slope), mean annual and seasonal climatic conditions (e.g., precipitation) and mean population density have the greatest influence on the probability of fire occurrence and burned area for any given year. Both the number of fires and annual area burned were greatest in warmer, biomass-rich lowland Bío-Bío and Araucanía regions. Resource selection analyses indicate fire ‘preferentially’ occurs in exotic plantation forests, mixed native-exotic forests, native sclerophyll forests, pasture lands and matorral, vegetation types that all provide abundant, flammable and connected biomass for burning. Structurally and compositionally homogenous exotic plantation forests may promote fire spread greater than native deciduous-Nothofagaceae forests which were once widespread in the southern parts of the study area. In the future, the coincidence of warmer and drier conditions in landscapes dominated by flammable and fuel-rich forest plantations and mixed native-exotic and sclerophyll forests are likely to further promote large fires in south-central Chile.
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