In association with a devastating earthquake in 1960, thousands of debris avalanches, landslides, and mudflows occurred in the Andes of south-central Chile. Catastrophic mass movements associated with seismic activity have affected the Andes of south-central Chile several times in the past 400 years and have profoundly influenced the regional vegetation.

Catastrophic influences on the vegetation of the Valdivian Andes, Chile

Late quaternary vegetation of southern Isla Grande de Chiloé, Chile

Summary Nothofagus dombeyi (Mirb.) Blume and Nothofagus nitida (Phil.) Krasser are closely related evergreen trees native to south central Chile. Nothofagus dombeyi is a pioneer in habitats subject to high daytime irradiances and nighttime freezing temperatures and has a wider altitudinal and latitudinal distribution than N. nitida, which is restricted to more oceanic climates. We postulated that N. dombeyi has a greater cold-acclimation capacity, expressed as a greater capacity to maintain a functional photosynthetic apparatus at low temperatures, than N. nitida. Because cold-acclimation may be related to the accumulation of cryoprotective substances, we investigated relationships between ice nucleation temperature (IN), freezing temperature (FT), and the temperature causing injury to 50% of the leaf tissues (LT50) on the one hand, and concentrations of total soluble carbohydrates (TSC), starch and proline on the other hand. Observations were made throughout a seasonal cycle in adults and seedlings in the field and in seedlings in the laboratory under cold-acclimation inductive and non-inductive conditions. In adults, LT50 values were lower in N. dombeyi than in N. nitida, suggesting that N. dombeyi is the more frost tolerant species. Adults of both species tolerated freezing in autumn and winter but not in spring and summer. In the fall and winter, seedlings of N. dombeyi had a much lower LT 50 than those of N. nitida. Nothofagus nitida seedlings, in autumn and winter, exhibited freezing avoidance mechanisms. Although elevated TSC and proline concentrations may contribute to freezing tolerance in adults of both species, an increase in proline concentration is unlikely to be the dominant frost tolerance response in adults because proline concentrations were higher in N. nitida than in N. dombeyi. In seedlings, however, there were large differences in proline accumulation between species that may account for the difference between them in freezing tolerance. Starch concentration in both species decreased during winter. Chlorophyll fluorescence indicated that maximal photochemical efficiency (Fv/Fm )r emained at optimal values (~0.8) throughout the year. The effective photochemical efficiency of PSII (φPSII) and relative electron transport rates (ETR r) decreased in winter in both species. In seedlings, fluorescence parameters were more affected in winter in N. nitida than in N. dombeyi. We concluded that adults and seedlings of N. dombeyi are hardier than adults and seedlings of N. nitida, which is consistent with its wider latitudinal and altitudinal distribution.

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Low temperature responses of Nothofagus dombeyi and Nothofagus nitida, two evergreen species from south central Chile.

In unpolluted regions, where inorganic nitrogen (N) inputs from the atmosphere are minimal, such as remote locations in southern South America, litterfall dynamics and N use efficiency of tree species should be coupled to the internal N cycle of forest ecosystems. This hypothesis was examined in two evergreen temperate forests in southern Chile (42°30'S), a mixed broad-leaved forest (MBF) and a conifer forest (CF). Although these forests grow under the same climate and on the same parental material, they differ greatly in floristic structure and canopy dynamics (slower in the CF). In both forests, biomass, N flux, and C/N ratios of fine litterfall were measured monthly from May 1995 to March 1999. There was a continuous litter flux over the annual cycle in both forests, with a peak during autumn in the CE In the MBF, litterfall decreased during spring. In both forests, the C/N ratios of litterfall varied over the annual cycle with a maximum in autumn. Annual litterfall biomass flux (Mean ± SD = 3.3 ± 0.5 vs 2.0 ± 0.5 Mg ha -1 ) and N return (34.8 ± 16 vs 9.1 ± 2.8 kg N ha -1 ) were higher in the MBF than in the CE At the ecosystem level, litterfall C/N was lower in the MBF (mean C/N ratio = 60.1 ± 15, n = 3 years) suggesting decreased N use efficiency compared with CF (mean C/N ratio = 103 ± 19.6, n = 3 years). At the species level, subordinated (subcanopy) tree species in the MBF had significantly lower C/N ratios ( 85). The litterfall C/N ratio and percentage N retranslocated were significantly correlated and were lower in the MBF. The higher net N mineralization in soils of the MBF is related to a lower N use efficiency at the ecosystem and species level.

Litterfall dynamics and nitrogen use efficiency in two evergreen temperate rainforests of southern Chile

The regeneration status of Fitzroya cupressoides in the Cordillera Pelada, Chile.

Beziehungen zwischen mikroklimatischen Faktoren und natürlicher Verjüngung araukano-patagonischer Nothofagus-Arten

In Sudchile folgen in sudlicher Richtung vier Vegetationsgebiete aufeinander: Hartlaubwalder (arid), temperierte Sommerwalder (semihumid — humid), nordpatagonische und subantarktische Regenwalder (humid — perhumid, temperiert bis kuhl). In der valdivianischen Ubergangszone zwischen 38–42° sudl. Br. treffen sich Florenelemente insbesondere der letzten drei Formationen. Unter diesen wurden 53 immergrune Geholze ausgewahlt und einige ihrer Resistenzeigenschaften untersucht.

P. Weinberger

Papers

Beziehungen zwischen mikroklimatischen Faktoren und natürlicher Verjüngung araukano-patagonischer Nothofagus-Arten

Untersuchungen Über Die Dürreresistenz Patagonischer Immergrüner Gehölze

Ein methodischer Beitrag zur Bestimmung des subletalen (kritischen) Wassers ättigungsdefizits