Resumen. La estrecha relación existente entre la vegetación y el polen que ésta produce favorece el estudio de las comunidades vegetales desde un punto de vista palinológico. De esta manera es posible obtener información sobre la distribución de la vegetación por medio de la dispersión y depositación de los granos de polen. La caracterización polínica de las comunidades vegetales permite investigar la historia de la vegetación desde la perspectiva actualista. El objetivo de este trabajo es caracterizar la dispersión-depositación del polen actual en relación con la distribución de la vegetación utilizando análisis estadísticos multivariados (clasifi cación y correspondencia) como un paso esencial para futuros estudios de la historia ambiental del Holoceno de la Isla Grande de Tierra del Fuego. El área de estudio está localizada en el sector argentino de la Isla Grande de Tierra del Fuego a 52°40'S-55°07'S; 65°05'O-68°40'O. El resultado de los métodos numéricos y su asociación con los parámetros ambientales ha permitido la diferenciación de un continuum de comunidades que pertenecen a diferentes unidades fi sonómicas: bosque y estepa graminosa. Palabras clave: palinología, lluvia de polen, comunidades, vegetación, análisis multivariados, Tierra del Fuego.
RESUMENEl estudio de coprolitos permite abordar aspectos ecológicos y culturales de poblaciones pasadas, como reconstrucciones del paleoambiente, de paleodietas, inferir estacionalidad en el uso de los recursos y situaciones de parasitismo. El objetivo de este trabajo es reconocer el aporte del análisis polínico de coprolitos para las reconstrucciones paleoambientales e identificar posibles ítems de la dieta de guanacos del Holoceno del área cercana al sitio Cerro Casa de Piedra 7 (Parque Nacional Perito Moreno, Santa Cruz, Argentina). Se analizó el contenido polínico de 15 coprolitos de guanaco provenientes de 7 capas arqueológicas entre 9.640 ± 190 y 5.400 ± 64 14 C años AP. La extracción polínica se llevó a cabo mediante acetólisis y se realizó la determinación y recuento bajo microscopio óptico. Se registró la presencia de tejido vegetal y de restos de parásitos. Se comparó el espectro polínico de los coprolitos con el espectro de los sedimentos y se realizaron análisis estadísticos. Los tipos polínicos dominantes fueron: Nothofagus, Empetrum rubrum, Asteraceae subfam. Asteroideae y Nassauvia, Poaceae y Caryophyllaceae. Los conjuntos polínicos de coprolitos y sedimentos contemporáneos presentan similitudes en algunos casos y diferencias en proporciones o en composición en otros. Las similitudes encontradas entre coprolitos y sedimentos permiten inferir que el polen de los coprolitos refleja los taxones dominantes de la vegetación, por el contrario cuando hay mayor abundancia de ciertos tipos polínicos en los coprolitos que en los sedimentos, podría deberse a que el polen de los coprolitos está sesgado con sobrerrepresentaciones de los ítems preferidos por el guanaco, mientras que si la abundancia es mayor en los sedimentos que en los coprolitos, podría deberse a que las plantas consumidas no estaban en su período de floración. Los resultados de este trabajo muestran el valor de los coprolitos como indicadores paleoambientales y aportan datos para la reconstrucción paleoambiental y de dieta de los guanacos.PALABRAS CLAVES: coprolitos, camélidos, paleoambiente, Patagonia, polen.
ABSTRACTThe study of coprolites permits to deal with ecological and cultural aspects of past populations, such as palaeoenvironmental reconstructions, palaeodiets, inferences related to the use of resources and parasitism status. The objective of this work is the recognition of the contribution of studies of pollen in coprolites to the palaeoenvironmental reconstructions, and the identification of probable items in the diet of guanacos living during the Holocene in the area near the site Cerro Casa de Piedra 7 (Perito Moreno National Park, Santa Cruz, Argentina). The pollen content of 15 coprolites of guanacos coming from seven archaeological layers dated by 14 C and resulting in ages between 9.640 ± 190 years BP and 5.400 ± 64 years BP were analysed. Pollen extraction was performed through acetolysis, and determination and counting under optical microscope. The presence of plant tissue and parasite remains was recorded. The coprolite...
Plant Palaeocommunities of Central Tierra del Fuego during the Early and Late Holocene.This study presents new data for the history of vegetation of central Tierra del Fuego. The goal is to identify the vegetation types before and after the middle Holocene, having in mind previous studies proposing a forest expansion started in early Holocene times following a SW-NE precipitation gradient. Two segments of a Sphagnum peat bog profile (R-2: 54°32'S, 67°04'W), now surrounded by the Nothofagus pumilio (Poepp et Endl.) deciduous forest, were analyzed. The following results were obtained through the modern analogs method: steppe and woodland were found in the older segment and open and closed forest in the younger segment. We concluded that an asynchronous establishment of the involved plant communities occurred. In fact, ca. 7000 years BP, while in other sites of the central island forests were already established, in R-2, located eastwards from those sites, the steppe-woodland ecotone dominated. On the other hand, from ca. 2000 years AP to modern times both open and closed forests covered the central area. The humidity carried by the Southern Westerlies could have influenced the late development of Nothofagus. This study represents an advancement in the knowledge of the vegetation history, and provides new data about the asynchrony in the establishment of communities.
A soil profile from the southern margin of Colhue Huapi Lake, at La Campanita site (45º38' S, 68º37' W), was analysed for pollen and algae content to know the past vegetation communities and to infer changes in lake water level occurred during the Late Holocene. Samples were dated by AMS 14 C methods. Radiocarbon ages were of 1711 ± 35 14 C yr BP at the base, 95cm depth, and another of 979 ± 42 14 C yr BP at 40cm depth. The record was dominated by no arboreal taxa, Chenopodiaceae being the principal shrub taxon and Cyperaceae the herbaceous one. Changes in the pollen record occurred mainly at a local scale and few differences were observed in the input of regional and extra regional pollen. From 1711 ± 35 14 C yr BP until ca. 1212 yr BP, a high lake water level was indicated by the low representation of Cyperaceae associated with few shallow areas available to be colonized and high percentages of Pediastrum and Botryococcus algae. Between ca. 1212 and 414 yr BP a period of changes with several fluctuations in water depth developed. This trend would modify at 979 ± 42 14 C yr BP with a decrease in the waters reflected by the expansion of Cyperaceae and algal reduction. From ca. 414 yr BP until 195 yr BP lake water level continued falling with a less fluctuating and net trend as indicated by the highest percentage of Cyperaceae in the sequence and a low algal representation. The subsequent reduction in Cyperaceae percentage and the moderate increase in the algae would indicate a recovery of the lake water level for the last ca. 195 yr BP. Additionally La Campanita sequence was statistically compared with a sequence obtained from the northwestern margin of the lake. Both sites registered a similar trend before 979 ± 42 14 C yr BP.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.