Moraine In-Transit as Parent Material for Soil Development and the Growth of Valdivian Rain Forest on Moving Ice: Casa Pangue Glacier, Mount Tronador (Lat. 41°10's), Chile

Abstract

Casa Pangue glacier is a regenerated valley glacier, covered by supraglacial moraine of variable thickness (1 to 3 m). Seven moraine in-transit arcs have originated from avalanches falling on the ice from the steep walls at the head of the valley. The debris has been relocated by glacier movement, and vegetation has become established on areas with sediment cover. Primitive soil has developed very rapidly, probably in less than 100 a. Chemical analysis of soil samples show that it is acid (pH 4.6 to 4.7), nitrogen and organic matter are absent, calcium content is low, and potassium content is high. Pedogenic processes are mostly related to intense chemical weathering, under conditions of more than 4 000 mm a−l of total precipitation.The plant communities established on the moraine are essentially similar to the Va1divian rain forest that characterizes the region. The most frequent tree is “coihue” (Nothofagus dombeyi), followed by “teniú“ (Weinmannia trichosperma) and “notro” (Embothrium coccineum). One specimen of N.dombeyi was found to be 18 m tall and 0.62 m in diameter; many others were taller than 12 m and reproduction was abundant. Dendrochronological analysis indicates a minimum age of 45 a for the oldest tree. Other plants found here are shrubs, some hemiparasitic and creeping plants, mosses, lichens, ferns, and fungi.Using air photographs of 1942, 1953, 1970, and our own oblique photographs of 1978, taken from the summit of a neighbouring peak 1 200 m above the glacier tongue, average surface velocity of the glacier tongue was estimated at 22.5 m a−l for the lower and intermediate sectors where the trees are growing. If the total length of the regenerated valley glacier is taken into account, the mean annual movement rate is 35.0 m a−l. If this value is extrapolated over the last 45 a, the trees have moved an average distance of at least 1 000 m in that time.The discovery of established communities (also observed at Río Blanco glacier, southwest of Mt Tronador) on moving ice constitutes an event not previously recorded in glaciological literature. Some significant aspects are discussed: time lapse for soil development on moraine deposits, primary plant succession on moraine deposits, the need of stable ground for plant colonization, the absolute validity of radiocarbon dating of glacier advances using fossil wood found within terminal moraines, and the validity of lichenometric techniques in deglaciated terrain.

Climate changes and recent glacier behaviour in the Chilean Lake District

“…1). This is a regenerated valley glacier with a debriscovered ablation area, located at the foot of icefalls falling from the head of the basin (Lliboutry, 1956;Rabassa et al, 1981). Supraglacial debris can have a strong influence on glaciers by isolating them from atmospheric heat, and thus, reducing ablation (Nakawo and Young, 1982;Benn and Evans, 1998).…”

Fluctuations of Glaciar Esperanza Norte in the north Patagonian Andes of Argentina during the past 400 yr

“…At this site, frontal variations since the LIA have been documented for Glaciar Río Manso, Castaño Overo and Frías on the Argentinean side (Rabassa et al, 1984;Villalba et al, 1990;Masiokas et al, 2010;. Rabassa et al (1978a) provide a detailed account of the 20th century behavior of Tronador glaciers on the Argentinean side, and Bown and Rivera (2007) studied the frontal and surface elevation changes of the Chilean Glaciar Casa Pangue during the 20th century. The available information indicates that Glaciar Frías reached the LIA maximum extent in the early 17th century, whereas at Río Manso and Castaño Overo this occurred in the 19th century.…”

“…Over the 20th century all glaciers have experienced a very noticeable frontal retreat and thinning . A minor readvance culminating in [1976][1977] has been identified at most sites: at Frías this advance has been very well documented by field measurements and dendro-geomorphological determinations (Rabassa et al, 1978a;Villalba et al, 1990). provide a climatic interpretation of the length variations of Glaciar Frías since the LIA using a combination of a simplified surface energy-balance model and a flowline model to account for the dynamical response of the glacier to changes in the climatic forcing.…”

Spatial patterns of microsite colonisation on two young lava flows on Mount Hekla, Iceland

“…The retreat of glaciers is a conspicuous sign of climate change during the last century in the Patagonian Andes (Masiokas et al, 2009), yet there have been only a few attempts to investigate the processes of primary succession on these sites. Some studies have analyzed the pattern of Nothofagus establishment on glacier moraines (Lawrence and Lawrence, 1959;Heusser, 1960Heusser, , 1964Pisano, 1978;Rabassa et al, 1981;Veblen et al, 1989;Dollenz, 1991;Armesto et al, 1992;Henríquez and Lusk, 2005). However, these studies have mostly focused on later stages of primary succession and rarely considered other components of the vegetation such as algae, lichens, bryophytes, and small vascular plants.…”