Festuca gracillima community: phytolith analysis in their southernmost distribution area, Tierra del Fuego ecotone (Tierra del Fuego, Argentine)

FERNÁNDEZ PEPI, M.G.; ZUCOL ALEJANDRO F.; ARRIAGA, M.O.

Estes Park, Colorado

Congreso; 8th International Meeting on Phytolith Research; 2011

PaleoResearch Institute, Golden, Colorado

Biodiversity studies in the central fueguian ecotone (S 53 º 48 'and W 67 º 48', 10 m altitude), Rio Fuego region,  Tierra del Fuego province (Argentine), allowed to know the composition and its landscape variants of natural plant communities. With human activity, these communities have been significantly modified, mainly through overgrazing of sheep. This contribution is part of the analysis being carried out to determine the evolutionary history of these vegetation and their changes in the recent past.Beginning the phytolith study of the natural communities, the Festuca gracillima steppe, considered the least affected by grazing, that  occupies the ecotone fueguino valley bottoms, plateaus and slopes. This community is dominated by Festuca gracillima in consocies with Deschampsia patula, Phleum alpinum, Festuca magellanica, Hordeum pubiflorum, Poa pratensis, Trisetum spicatum,and others herbs and shrubs suchAnemone multifida, Gamochaeta nivalis empetrifolia and B. microphylla, and in some areas is important the presence of chamaephytes cushions (Empetrum rubrum, Azorella trifurcata, Bolax gummifera, Baccharis magellanica). Changes in this community loss promotes of some of these plant elements and a greater abundance of adventitious species such as Poa.  Therefore, we first studied the species composition of of phytoliths, with principal emphasis on grasses. As foliar phytoliths assemblages of these components were characterized by the presence of sinuate trapezoid (pooid and festucoid-boats),  truncated cones, crescents, elongate prismatic elements with ondulate to smooth contour, stomata complex elements and silicified hair and hooks phytoliths.Moreover, among the dicotyledons showed the presence of polyhedral,  rectangular phytoliths jointly with irregular ones, silicified hairs, vascular elements phytoliths and articulated stomata complex. At the time, have begun studies of soils from different sampling stations. The first profiles analyzed showed  abundant silica microremains, jointly with microcharcoal and partially degraded tissular fragments. Among phytoliths, has observed an abundance of graminoids elements with elonagted, point-shaped, conical and sinuate trapezoids phytolith types. These analyzed samples although a marked abundance of grasses in the recent past, not-graminoid phytoliths make possible to distinguish certain assemblage variants in different sector of the profiles.While a preliminary way, this paper presents the first results obtained in the study of changes of the ecotone communities in Tierra del Fuego, which show that phytolith analysis is a valuable tool to be applied in this southern region.