Abstract. Structural (density, height, basal area, above‐ground tree biomass, leaf area index) and functional (leaf phenology, growth rate, fine litter fall, leaf decomposition) traits were quantified in four mature forests of Nothofagus pumilio (lenga) along an altitudinal sequence in Tierra del Fuego, Argentina. Three erect forest stands at 220, 440 and 540m and a krummholz stand at 640 m a.s.l. were selected. Along the altitudinal sequence, stem density increased while DBH, height, biomass, leaf‐size and growth period, mean growth rate and decay rate decreased. Dead stems increased and basal area and fine‐litter fall decreased with an increase in elevation among erect forests, but these trends inverted at krummholz. We suggest that krummholz is not only a morphological response to the adverse climate but is also a life form with functional advantages.

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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The significant mortality of the Austrocedrus chilensis (D. Don) Pic. Serm. et Bizarri forests, locally known as ''Mal del Cipre ´s'', has been reported since 1945 for most sites across its distribution in Argentina. However, the cause of this decline is still a topic of discussion. In this study, radial growth patterns from symptomatic and asymptomatic A. chilensis trees were analyzed to determine the influence of drought events on tree growth. Fifty pairs of symptomatic and asymptomatic trees with similar DBH, competition, and microsite conditions were cored at five pure A. chilensis stands near El Bolso ´n, Rı ´o Negro, Argentina. A reference chronology from nonaffected trees was used to cross-date all cores and to determine the relationship between A. chilensis radial growth and climate. The growth of A. chilensis is favored by above average precipitation in late spring-early summer (November and December). A strong relationship was also observed between radial growth patterns and the Palmer drought severity index, a measure of the regional water deficit. Significant differences in growth patterns were recorded between symptomatic and asymptomatic trees. Following extreme drought events, the growth of symptomatic trees is consistently lower than in asymptomatic trees. Based on the larger number of droughts recorded during the past decades and on future climatic predictions suggesting increasing trends in the frequency and intensity of drought events in northern Patagonia, a gradual increase in the number of trees affected by ''Mal del Cipre ´s'' along the twenty-first century is likely expected.

& Introduction Silviculture systems applied in Nothofagus pumilio forests are based on opening the canopy to stimulate natural regeneration by modifying light and soil moisture. The objective is to evaluate regeneration dynamics of N. pumilio along different forest canopy and solar radiation gradients. & Materials and methods Regeneration data and seed production were obtained in 98 permanent plots established in old-growth and harvested stands along a crown cover gradient (19-93%). Volumetric soil water content and basal area were also measured, while crown cover and solar radiation transmission were estimated using hemispherical photographs. Sapling height was modeled using plant age, crown cover, and solar radiation transmission of the stands as explanatory variables. & Results Natural regeneration dynamics were closely related to crown cover values, which determined seed production and the successful establishment and subsequent regeneration growth. Height growth was found to be related to crown cover and solar radiation transmission, where N. pumilio regeneration is optimized at intermediate crown cover levels (45% crown cover, 0.5 effective leaf area index, 26 W m 2 global radiation, and 65% percentage of global radiation). & Conclusion These findings can be used to develop new silvicultural methods or to adjust the current practices to ensure regeneration establishment and maximize height growth at the stand level.