Mauro E. González

Tree regeneration responses in a lowland Nothofagus-dominated forest after bamboo dieback in South-Central Chile

The bamboo Chusquea quila (Poaceae:Bambuseae) is the most abundant understory species ofNothofagus-dominated forests at low elevations inthe Chilean Lake District. Species of this genus strongly inhibit theestablishment and growth of tree species, especially those of the genusNothofagus. At intervals of many years, this bambooflowerssynchronously and dies, creating large-scale disturbances. The mainobjective of this study was to determine the influence of bamboo dieback ontreeregeneration, especially of shade-intolerant species. The forest studiedis a remnant stand of old-growth forest dominated by emergent individualsof N. obliqua and Eucryphiacordifoliawhich project about 10 m above a main canopy formed byAextoxicon punctatum, Laureliaphilippiana, and Podocarpus saligna. Treeseedlings that established prior to bamboo dieback were recorded in six gapsdensely covered by bamboo. After the dieback event in the early 1990s,recruitment, height growth and survivorship were monitored in four gaps duringtwo growing seasons. After the synchronous mass flowering and death ofChusqueaquila, both reorganization of advance regeneration and new seedlingrecruitment were observed in gaps. The advance regeneration consisted mainly ofthe shade-tolerant species A. punctatum,L. philippiana, and Amomyrtus luma.These species together with E. cordifolia accounted forover 90% of the total individuals in gaps. During the following twoseasons, c. 40% of the advance regeneration either died or was damaged.Root suckers of E. cordifolia and L.philippiana were taller and grew faster than the seedlings of otherspecies. Nothofagus obliqua was unable to establishadvanceregeneration in gaps formerly dominated by bamboo. New recruitment resulted inthe synchronized establishment of treeseedlings, especially less shade-tolerant species such as N.obliqua, Aristotelia chilensis,Rhaphithamnus spinosus, and E.cordifolia. These species recruited into the gaps almost entirelyduring the first season right after the bamboo dieback. However, by the end ofthe second season, these species had a lower density due to a combination oflower recruitment rate, shortened recruitment period, and greater mortalityratecompared to the shade-tolerant species. New bamboo seedlings grew fasterand were more abundant than tree seedlings, except for root suckers (bothnew establishment and advance regeneration) of E.cordifolia which is more likely to successfully recruit into thecanopy. Seedlings of N. obliqua compete poorly with bambooseedlings; its successful recruitment may require bamboo flowering coincidentwith a mast seed year for the tree species.

The historical range of variability of fires in the Andean–Patagonian Nothofagus forest region

The present synthesis addresses key questions about several extreme fire events that occurred in the Nothofagus forest region of southern Argentina and Chile in the late 1990s and early 2000s: (1) are there historical precedents for the extent and severity of these recent wildfires? (2) To what extent can large, severe fires be attributed to influences from modern humans, either indirectly through land-use practices or directly through ignition? (3) What are the relationships of these fire events to interannual climatic variability and trends? (4) What are the medium-term ecological consequences of these fire events, particularly in terms of the resiliency of the burned ecosystems? Historic fire regimes vary greatly across the different ecosystem types in the southern Andean region, and the tree-ring record shows that before the 20th century, large severe fires also played a significant ecological role in shaping even the wettest forests. Recent severe droughts at an annual time scale have been facilitated by a trend towards higher temperatures since the mid-1970s. In large parts of the region, the risk of wildfire ignition and spread has been exacerbated by increases in lightning associated with higher temperatures, increased ignitions associated with exurban development, and conversion of less flammable native vegetation to more flammable plantations of exotic conifers.

Climatic influences on fire in Araucaria araucana–Nothofagus forests in the Andean cordillera of south-central Chile

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 Niño–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 Niño 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 anticyclone.

Cambio climático y su impacto potencial en la ocurrencia de incendios forestales en la zona centro-sur de Chile (33º - 42º S)

En muchas regiones del mundo los incendios estan siendo cada vez mas frecuentes y severos. Las principales causas de estos patrones se asociarian tanto a cambios en el clima como en las practicas de uso de la tierra. La presente contribucion examina sucintamente los recientes cambios y proyecciones climaticas y su potencial influencia en la ocurrencia de incendios en la zona centro-sur de Chile, asi como las medidas de adaptacion necesarias para hacer frente a este problema. Diversos estudios coinciden en que el mayor efecto del cambio climatico en esta zona estara asociado a la disminucion de las precipitaciones lo cual incidiria en un incremento de la ocurrencia y area afectada por incendios forestales. Bajo este escenario, el principal desafio esta en definir acertadamente las politicas y estrategias de mitigacion y adaptacion sectoriales con la finalidad de promover bosques mas saludables, -en terminos de productividad, diversidad y resiliencia- asegurando una provision continua de servicios ecosistemicos bajo un clima cambiante.

Spatio-temporal effects of human drivers on fire danger in Mediterranean Chile

El objetivo de este estudio fue analizar la influencia de factores humanos, en especifico del cambio de cobertura y uso de suelo (CCUS), en el peligro de incendios forestales en una region mediterranea de Chile. Para ello, se evaluo la probabilidad de ignicion y la inflamabilidad del paisaje como componentes clave del peligro de incendio. La probabilidad de ignicion fue determinada a traves de una de regresion autologistica para los anos 1999 y 2009, utilizando como base los registros de la Corporacion Nacional Forestal y variables generadas a partir de bases de datos geograficas. La inflamabilidad se evaluo mediante la combinacion de las categorias de vegetacion presentes en el Catastro y evaluacion de recursos vegetacionales de Chile de 1999 y su actualizacion de 2009, y el modelo de combustible desarrollado por Julio (1995). Se llevo a cabo un analisis espacio-temporal de inflamabilidad el que se relaciono con los principales procesos CCUS (expansion de plantaciones, regeneracion forestal y abandono de tierras agricolas). Se combino la probabilidad de ignicion y el analisis de inflamabilidad para producir mapas de peligro de incendios. Los resultados mostraron que el peligro de incendio es un indicador dinamico que depende en gran medida de factores humanos. En 1999, las areas de alto peligro concentraron 31.399 hectareas, mientras que para el ano 2009 esta area aumento en 54.705 ha. En ambos periodos el peligro tuvo una distribucion espacial similar, concentrandose cerca de las carreteras, principales ciudades (26,3 % de la zona de peligro) y en areas cubiertas por plantaciones forestales (33,2 % de la superficie bajo peligro alto de incendio)

Efectos de distintas dosis de fertilizante de liberación controlada (Osmocote®) en el desarrollo de plantas de coigüe, raulí y ulmo

Resumen es: El presente estudio tuvo por objetivo determinar en coigue (Nothofagus dombeyi), rauli (Nothofagus nervosa) y ulmo (Eucryphia cordifolia) la respuesta en...

Patrones de regeneración arbórea en claros a una década de la floración y muerte masiva de Chusquea quila (Poaceae) en un remanente de bosque antiguo del valle central en el centro-sur de Chile

En bosques de elevaciones bajas del centro-sur de Chile (38-42° S) Chusquea quila (Poaceae) es la especie del sotobosque de mayor influencia en el proceso de regeneracion de especies arboreas en claros naturales y antropogenicos. Su floracion y muerte sincronica, despues de un extenso periodo en estado vegetativo, constituye una alteracion de gran escala que puede afectar importantemente la dinamica de regeneracion arborea en claros. El ultimo episodio de muerte masiva de C. quila (1989-1995), que afecto a los escasos remanentes de bosques antiguos dominados por Nothofagus obliqua y especies siempreverdes, ofrecio la oportunidad de monitorear la respuesta de la regeneracion arborea en seis claros del dosel entre los anos 1994 y 2003. El objetivo central de este estudio fue analizar, luego de 10 anos desde dicho evento, los principales patrones de respuesta de la regeneracion arborea en claros. La regeneracion avanzada -establecida en los claros previa a la floracion y muerte de C. quila- estuvo dominada por las especies tolerantes Aextoxicon punctatum, Laureliopsis philippiana y Amomyrtus luma. Despues de 10 anos desde la muerte de C. quila en los claros, la mortalidad de la regeneracion avanzada fue 42 % y ocurrio principalmente en individuos originados de semillas. Por su parte, la respuesta de los nuevos establecimientos estuvo marcada por la abundante regeneracion de N. obliqua, Podocarpus saligna y Aristotelia chilensis durante los primeros anos postdisturbio; sin embargo, al cabo de 10 anos solo unos pocos individuos de estas especies sobrevivieron a la competencia de la nueva cohorte de C. quila. Los individuos originados por rebrotes de raices de las especies Eucryphia cordifolia, Gevuina avellana y L. philippiana presentaron mayor sobrevivencia y crecimiento que aquellos originados de semillas. Finalmente, el aumento temporal de recursos asociado a la muerte de C. quila en claros, favorece a especies arboreas tolerantes y semitolerantes, especialmente a aquellas de exitosa reproduccion vegetativa. Especies pioneras en estos bosques como N. obliqua no fueron favorecidas por esta alteracion endogena en claros pequenos (< 1.000 m2), sugiriendo que alteraciones de mayor magnitud serian necesarias para su exitoso establecimiento.

Southern Annular Mode drives multicentury wildfire activity in southern South America

Significance Fire is a key ecological process affecting ecosystem dynamics and services, driven primarily by variations in fuel amount and condition, ignition patterns, and climate. In the Southern Hemisphere, current warming conditions are linked to the upward trend in the Southern Annular Mode (SAM) due to ozone depletion. Here we use tree ring fire scar data obtained from diverse biomes ranging from subtropical dry woodlands to sub-Antarctic rainforests to assess the effect of the SAM on regional fire activity over the past several centuries. Our findings reveal a tight coupling between fire activity and the SAM at all temporal scales and in all biomes, with increased wildfire synchrony and activity during the 20th century compared with previous centuries. The Southern Annular Mode (SAM) is the main driver of climate variability at mid to high latitudes in the Southern Hemisphere, affecting wildfire activity, which in turn pollutes the air and contributes to human health problems and mortality, and potentially provides strong feedback to the climate system through emissions and land cover changes. Here we report the largest Southern Hemisphere network of annually resolved tree ring fire histories, consisting of 1,767 fire-scarred trees from 97 sites (from 22 °S to 54 °S) in southern South America (SAS), to quantify the coupling of SAM and regional wildfire variability using recently created multicentury proxy indices of SAM for the years 1531–2010 AD. We show that at interannual time scales, as well as at multidecadal time scales across 37–54 °S, latitudinal gradient elevated wildfire activity is synchronous with positive phases of the SAM over the years 1665–1995. Positive phases of the SAM are associated primarily with warm conditions in these biomass-rich forests, in which widespread fire activity depends on fuel desiccation. Climate modeling studies indicate that greenhouse gases will force SAM into its positive phase even if stratospheric ozone returns to normal levels, so that climate conditions conducive to widespread fire activity in SAS will continue throughout the 21st century.

Tectonic ecology of the temperate forests of South America and New Zealand

ABSTRACT Ecological disturbances triggered by earthquakes and volcanic eruptions are of fundamental importance in structuring the temperate forests of southwestern South America and New Zealand. We review studies of the ecological effects of these tectonic phenomena and how they have been central to progress in the modern development of forest ecology in both regions. Studies of tectonic influences on the dynamics of southern temperate rainforests of Chile and New Zealand published in the 1970s and early 1980s contributed prominently to the shift away from the equilibrium paradigms dominant globally in the 1960s and towards modern non-equilibrium frameworks of forest dynamics. Empirical studies of tectonic ecology in these temperate forests in combination with critical evaluations of earlier successional theory have significantly advanced understanding of the roles of coarse-scale disturbance in the dynamics of forests in southwestern South America and New Zealand. Recognition that cohort forest structures triggered by exogenous disturbances such as wind storms and tectonic events are the norm rather than all-aged structures has been of fundamental importance to understanding the dynamics of these forests. The non-equilibrium patch dynamics framework for interpreting forest structure and dynamics bolstered by tectonic ecology studies in southern South America and New Zealand was of key importance in refining older views of these forests as being out of equilibrium with contemporary climate, revising understanding of the effects of introduced browsing animals on forest structure, and guiding the development of appropriate forest management practices.

Poblaciones de araucaria enana (Araucaria araucana) en la Cordillera de Nahuelbuta, Chile

Araucaria araucana (araucaria o pehuen) desarrolla normalmente en su habitat natural un crecimiento arboreo con altura > 20 m. Sin embargo, en 1984, en la cima de la Cordillera de Nahuelbuta se encontraron dos poblaciones enanas. En este trabajo se caracterizo la estructura, composicion y edades de ambas poblaciones de A. araucana y Nothofagus dombeyi como especie asociada mas importante, asi como las caracteristicas fisicas y quimicas de los suelos donde crecen. El enanismo se manifesto en ambas especies. En A. araucana los individuos raramente sobrepasaron 10 m de altura con una alta relacion diametro/altura respecto a la de arboles normales de edad similar. El crecimiento diametral anual fue < 0,12 cm para edades cercanas a 300 anos y diametros de base de alrededor de 36 cm. El desarrollo de troncos cortos con ramas extendidas y delgadas, como patas de arana, refuerza el aspecto de arboles enanos. En N. dombeyi (edades de 36 a 37 anos) el crecimiento diametral anual fue de 0,26 a 0,27 cm; la mayor parte de los individuos (60-75%) presento diametro de base < 15 cm y altura entre 1 y 6,5 m. La ubicacion topografica en la cima de la Cordillera de Nahuelbuta, sobre 1.000 m de altitud, y la exposicion abierta hacia el oceano Pacifico definen un clima de rigurosidad extrema que, junto con la escasa profundidad del suelo y pobreza de nutrientes, influyen en el bajo crecimiento, reducido tamano y formas tortuosas de los arboles.