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We studied the diversity of endophytic fungal assemblages associated with Empetrum rubrum Vahl ex Willd (Ericaceae), a medicinal plant from austral South America, collected at the eastern Malvinas/Falkland Islands. From the leaves and stems of E. rubrum, 83 endophytic fungal isolates were recovered and identified using molecular biology taxonomy methods within 18 genera and 24 different taxa. Fungi from the Leotiomycetes class were the most abundant, followed by those of Dothideomycetes, Sordariomycetes, Eurotiomycetes, and Pezizomycetes. Phacidium, Allantophomopsis, Preussia, and Cladosporium were the most abundant genera. In addition, 18 taxa were detected as singlets representing rare taxa within the fungal assemblages. From the stem tissues of E. rubrum, 11 exclusive fungal genera from 15 taxa were recovered. In contrast, six fungal genera and seven taxa were identified in the leaves. Only endophytic Phacidium pseudophacidioides was found in the stem and leaf tissues. Our results showed that the tissues of E. rubrum, a medicinal species from austral South America, harbored a diverse endophytic fungal assemblage similar to those reported for the plants in the Ericaceae family from temperate regions. However, E. rubrum displayed unusual fungal taxa, reported as endophytes, such as Allantophomopsis cytisporea, Humicolopsis cephalosporioides, Phacidium grevilleae, Pseudocercospora pseudophacidioides, Pseudocercospora brackenicola, and Pseudopithomyces sp. Additionally, the E. rubrum fungal assemblage was dominated by rare species (singlets).

Dwarf shrubs are a dominant plant type across many regions of the Earth and have hence a large impact on carbon and nutrient cycling rates. Climate change impacts on dwarf shrubs have been extensively studied in the Northern Hemisphere, and there appears to be large variability in response between ecosystem types and regions. In the Southern Hemisphere, less data are available despite dwarf shrub vegetation being a dominant feature of southern South America and mountainous regions of the Southern Hemisphere. Here, we present the response of an Empetrum rubrum dwarf shrub and a Poa grass community to 12 years of experimental climate manipulation achieved using open top chambers on the Falkland Islands, a cold temperate island group in the South Atlantic. The dwarf shrub and grass vegetation did not change significantly in cover, biomass or species richness over the 12 years period in response to climate warming scenarios of up to 1°C reflecting annual warming levels predicted in this region for the coming decades. The soil microarthropod community, however, responded with declines in abundance (37%) under warming conditions in the grass community, but no such changes were observed in the dwarf shrub community. Overall, our data indicate that dwarf shrub communities are resistant to the levels of climate warming predicted over the coming decades in the southern South America region and will, therefore, remain a dominant driver of local ecosystem properties.

Following the theory on costs of reproduction, sexually dimorphic plants may exhibit several trade-offs in energy and resources that can determine gender dimorphism in morphological or physiological traits, especially during the reproductive period. In this study we assess whether the sexes of the dioecious species Empetrum rubrum differ in morphological and ecophysiological traits related to water economy and photochemical efficiency and whether these differences change in nearby populations with contrasting plant communities. We conducted physiological, morphological, sex ratio, and cover measurements in E. rubrum plants in the Magellanic steppe, North-Eastern part of Tierra del Fuego (Argentina), from two types of heathlands with differing community composition. We found differences between sites in soil pH and wind speed at the canopy level. E. rubrum plants exhibited lower photosynthetic height and higher LAI (leaf area index), lower RWC (relative water content) and higher water-use efficiency (lower Δ13C) in the heathland with harsher environmental conditions. Gender dimorphism in the physiological response was patent for photochemical efficiency and water use (RWC and Δ13C discrimination), with males showing a more conservative strategy in relation to females. Accordingly, male-biased sex ratio in the stress-prone community suggested a better performance of male plants under stressful environmental conditions. The integrated analysis of all variables (photochemical efficiency, RWC, leaf dry matter content (LDMC), pigments, and Δ13C) indicated an interaction between gender and heathland community effects in the physiological response. We suggest that female plants may exhibit compensatory mechanisms to face their higher reproductive costs.

El objetivo del presente trabajo fue determinar el contenido vegetal en un coprolito humano hallado en el sitio arqueológico Cerro Casa de Piedra 7, a partir de estudios microhistológicos. Se hidrató 1 gr de un coprolito y se fltró a través de seis mallas de gasa de aproximadamente 500 μm de poro para recuperar la fracción gruesa. La totalidad de esta fracción, previa decoloración, se montó en portaobjetos con gelatina-glicerina. Se identificaron restos de epidermis de hojas y frutos de Empetrum rubrum y de Gaultheria mucronata. Los restos de frutos encontrados de estas especies, indican que el individuo que los consumió ocupaba el sitio durante el verano. Los resultados obtenidos constituyen un complemento de los análisis palinológicos realizados en los mismos coprolitos, ya que permiten precisar la identificación a nivel específico de algunos vegetales consumidos.

n-Alkane distributions are frequently used as palaeoclimate proxies in ombrotrophic peat deposits. Although n-alkane distributions differ strongly between plant species, n-alkanes are not species-specific molecules. For a proper interpretation, it is important to understand the different abundances of n-alkanes in various plant species as well as the changes that occur when plant litter is transformed to peat. In particular because molecular markers are especially valuable in highly decomposed peat where plant remains are no longer recognizable, it is important to understand the effects of decomposition on n-alkane distributions. The organic matter (OM) of a high-resolution sampled, 9 m thick, ombrotrophic peat deposit from Tierra del Fuego was analysed with pyrolysis-gas chromatography/mass spectrometry (pyrolysis-GC/MS). The same samples were analysed for carbon (C) and nitrogen (N) content. Depth profiles of C:N ratio, the summed lignin and summed polysaccharide pyrolysis products, and markers specific for Sphagnum spp., Empetrum rubrum and Nothofagus antarctica, enabled a reconstruction of changes in vegetation composition to be made. This reconstruction was used to examine the validity of the n-C23 alkane to indicate Sphagnum and the summed long chain n-alkanes (C29 and C31) to reflect leaf input of the woody species E. rubrum and N. antarctica. Our results show that even in Sphagnum-dominated peat, the n-alkane distribution is not determined by Sphagnum but by leaf input of E. rubrum and N. antarctica. However, good correlations between the n-C23 alkane and the Sphagnum marker 4-isopropenylphenol, and between the summed n-C29 and n-C31 alkanes and the marker of N. antarctica support that their relative change with depth can be used to indicate the abundance of these species in Sphagnum-dominated peat. In peat with relatively low contributions of Sphagnum, both n-alkane proxies (C23 and C29 + C31) reflect the degree of decomposition. We evaluated the influence of Sphagnum dominance, decomposition, and pyrolysis on the n-alkane distributions in peat OM.

Association between soil properties and two host plants for arbuscular mycorrhizal fungi in a field study involving grasslands exhibiting a range of degradation as a result of long-term modes of sheep grazing in Tierra del Fuego (Argentina) was researched. Vegetation rich in prostrate shrubs (Empetrum rubrum) of little forage value that grow in soils of low pH, high carbon, low N, and low Ca + Mg were associated with selective long-term grazing at high intensity. Vegetation with large proportions of mycorrhizal grasses such as Poa rigidifolia and Deschampsia flexuosa, which species grow in soil of less acidity, low carbon/nitrogen ratio, high NO3− and high exchangeable Ca + Mg, were associated with selective grazing at moderate intensities or nonselective grazing at high intensity in short term. These two grasses, representing more palatable and nutritious plants for sheep, were present at different degrees of coverage and AM-spore densities in their rhizospheric soils. Twenty-five species of AM-fungal spores belonging to the Acaulosporaceae (41.4%), Glomeraceae (36.2%), Ambisporaceae (13.6%), Pacisporaceae (8.4%), and Scutellosporaceae (0.4%) were identified. Ambisporaceae spores were associated with low fertility and light soils, Glomeraceae spores with more fertile soils and disturbed ecosystems, and Acaulosporacea spores with less disturbed ecosystems. Our results indicated that the sheep-grazing mode and intensity affected vegetation and soil fertility in grasslands. AM-fungal population in rhizopheric soils of palatable grasses would thus provide an indicator of grassland degradation and fertility.

Although positive interactions among plants are believed to be common in primary succession, they have rarely been demonstrated on glacial moraines. In Patagonia, the prostrate shrub Empetrum rubrum is dominant in early succession in recently deglaciated valleys, eventually being replaced by the small tree Nothofagus antarctica. This study experimentally evaluates the effects of E. rubrum shrubs on density, biomass, growth and survival of N. antarctica seedlings. The initial density of the seedlings was significantly higher under the canopy of Empetrum than in open areas. A removal experiment was performed to evaluate the influence of Empetrum on survival and growth of seedlings that germinated naturally beneath the canopy of this species. The shrub cover was removed from half of a sample of randomly selected seedlings, and left intact above the remainder. One year later, seedlings with an intact cover of E. rubrum showed significantly higher survival, growth and leaf number than seedlings which had been exposed. The results suggest that the presence of E. rubrum facilitates the establishment of N. antarctica in post-glacial succession, mainly as a result of more favourable microclimatic conditions under the shrub canopy.

Summary • Tierra del Fuego is subject to increases in solar UV-B radiation in the austral spring and summer due to ozone depletion. • Plastic films were used to filter solar UV-B radiation over peatland plots through six field seasons, resulting in near-ambient (c. 90%) and reduced (c. 17%) solar UV-B treatments. • As in the first three field seasons of treatments, near-ambient UV-B caused reduced height growth but had no effect on biomass production of the moss Sphagnum magellanicum. It reduced leaf and rhizome growth of Tetroncium magellanicum. Height growth and morphology of Empetrum rubrum and Nothofagus antarctica were only affected by solar UV-B during the fourth to sixth field seasons. There was also a decrease in Tetroncium leaf nitrogen under near-ambient UV-B. • Growth of Sphagnum was less affected than that of most emergent vascular plants. This enabled the Sphagnum mat to engulf more Nothofagus, and limit the escape of Empetrum under near-ambient UV-B. Yet, differences in the response of species to solar UV-B were not expressed as changes in plant community composition.

1. Plant growth and pigmentation of the moss Sphagnum magellanicum and the vascular plants Empetrum rubrum, Nothofagus antarctica and Tetroncium magellanicum were measured under near-ambient (90% of ambient) and reduced (20%) ultraviolet-B (UV-B) radiation for three growing seasons in a Sphagnum peatland in Tierra del Fuego, Argentina (55°S). 2. Reduction of solar UV-B increased height growth but decreased volumetric density in S. magellanicum so that biomass production was not influenced during the 3 years. The morphology of vascular plants tended not to respond to UV-B reduction. 3. A 10-20% decrease in UV-B-absorbing compounds occurred in T. magellanicum under solar UV-B reduction. No effects were seen on chlorophyll or carotenoids in S. magellanicum, although, for UV-B-absorbing compounds, a significant interaction between UV-B and year suggests some response to solar UV-B reduction. 4. The climate-related growth of the dwarf shrub E. rubrum was assessed retrospectively by correlating an 8-year record of annual stem elongation with macroclimatic factors including solar UV-B and visible radiation, precipitation and temperature. 5. No significant negative correlations were found between annual E. rubrum stem elongation and ambient solar UV-B, the ratio of UV-B: visible radiation, or the 305-nm: 340-nm irradiance ratio for an 8-year record (1990-91 to 1997-98), nor was stem elongation affected by solar UV-B reduction in our experimental field plots after 3 years. 6. The role of solar UV-B radiation on plant growth in Sphagnum peatlands in Tierra del Fuego, Argentina, is likely to depend on the severity of stratospheric ozone depletion over the next several decades. The increases in ambient solar UV-B associated with ozone depletion over the last 20 years are less than the difference between our radiation treatments. Therefore, providing that the ozone layer substantially recovers by the middle of this century, only modest effects of increased solar UV-B on plant growth may be expected. Fil: Searles, Peter Stoughton. State University of Utah; Estados Unidos Fil: Flint, Stephan D.. State University of Utah; Estados Unidos Fil: Diaz, Susana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Rousseaux, Maria Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Ballare, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Caldwell, Martyn M.. State University of Utah; Estados Unidos

Vegetation in the high Central Andes: Bardas Blancas-Pehuenche Pass (Malargue, Mendoza, Argentina). The vegetation occurring between Bardas Blancas and Pehuenche Pass in the south of Mendoza is studied for the purpose of obtaining floristic-ecological information about plant communities. Work is carried out along an altitudinal gradient from 1420 to 2800 m a.s.l., using phytosociological method. The major plant communities yielded by analyses of comparative survey tables are described. In all, 19 plant communities are revealed, including high- and low-altitude wetlands, and 24 floristic groups characterized by diagnostic, exclusive, preferential and accompanying species. Analysis of dispersal and of hierarchical conglomerates allows confirming the close relationships of plant communities with temperature and altitude. The chorological analysis allowed to identificate two phytogeographic provinces: Patagonia and High Andes. There is a floristic-ecological relationship of phytogeographic environments with life forms. The phytosociological study revealed three vegetation belts: 1- scrubland of Neosparton ephedroides, Larrea nitida, Colliguaja integerrima and Fabiana imbricata, 2- scrubland of Adesmia volckmannii, Chuquiraga oppositifolia, Adesmia pinifolia and Adesmia obovata, and 3- steppe of Azorella monantha, Nassauvia revoluta, Empetrum rubrum and Ochetophila nana. The results may probably allow extrapolation in the north and south of the area.

Stratospheric ozone depletion occurs over Tierra del Fuego, southern Argentina and Chile, in the austral spring and summer due to the precession of the Antarctic ‘ozone hole’ and the general erosion of the ozone layer. Plots receiving either near-ambient or reduced UV-B radiation were established using different louvered plastic film filters over Sphagnum bog and Carex fen ecosystems in October 1996. In the Sphagnum bog system, growth measurements during the late spring and summer showed no significant differences in the moss Sphagnum magellanicum, or the vascular plants (Empetrum rubrum, Nothofagus antarctica, and Tetroncium magellanicum) between near-ambient and attenuated UV-B radiation treatments. In the Carex fen system, leaf length and spike height did not differ in the two dominant species, Carex decidua and C. curta, between UV-B radiation treatments. The length of individual spikelets of C. curta under near-ambient UV-B radiation was less than under the reduced UV-B radiation treatment, but this was not evident in C. decidua. No differences in seed number, seed mass, or viability were seen in either Carex species between the UV-B treatments. Two important constituents of the microfauna that inhabit the Sphagnum bog are testate amoebae and rotifers. These both appeared to be more numerous under near-ambient UV-B radiation than under reduced UV-B radiation. The subtle responses of the Sphagnum and Carex ecosystems may become more apparent in subsequent years as the treatments are continued. Trophic-level changes, such as the differences in number of amoebae and rotifers, may be more sensitive to solar UV-B radiation than growth and productivity of the vegetation.

The effects of increasing nutrient availability and liming on the growth of Dactylis glomerata and its neighboring vegetation were studied in dry heath communities dominated by Empetrum rubrum from northern Tierra del Fuego (Argentina). We carried out three pot experiments and a field experiment using acid heath soils collected from communities dominated by different degrees of cover by E. rubrum. All studies were consistent in showing high responses of D. glomerata to phosphorus (P) additions. Lime amendments depressed plant growth. This was attributed to two effects, increased sorption of added P by lime and decreased desorption of native P. The results also showed that the growth of D. glomerata on soil containing a high proportion of E. rubrum leaf litter was severely depressed. In the field experiment, additions of P increased the growth of D. glomerata and other grass species. This suggests that increasing nutrient availability may change the competitive relationship between shrub species a...

We studied the response curves of Dactylis glomerata to addition of nitrogen (N), potassium (K), and lime in presence of a range of added phosphorus (P) on an acid xeric heath soil (pH 4.3) of Tierra del Fuego (Argentina). The heath community developed on the soil has dominated by a 50% of cover of an evergreen dwarf shrub (Empetrum rubrum) of very little forage value. Addition of P alone or combined with any of amendments increased significantly the growth of Dactylis. In contrast, absence of P, even supplying 50 ppm of N or K, no increase in growth of Dactylis was detected. This suggested that P was the most important nutrient limiting the growth of forage plants in this heath soil. By fitting response curves, we studied three different aspects: the maximum and the minimum yield approached, and the slope of the response curve to reach the maximum yield. Increasing added P, the maximum yield reached was greatest for N addition, lowest for lime, and intermediate for K and P alone. The minimum yie...

Fil: Fernandez Pepi, Maria Gabriela. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina

The aim of the present study was to develop a seasonality palynological model from modern feces of Lama guanicoe for the interpretation of pollen found in coprolites. For this purpose, fecal samples of L. guanicoe were collected during a year from dung piles located in the ecotone Subantarctic Forest-Patagonian Steppe, Perito Moreno National Park (PMNP) (NW Santa Cruz province, Argentina). For every season, the food items were characterized and the post-depositional pollen contamination of feces was evaluated. The results showed differences among the pollen sets of feces from every season and no post-depositional pollen contamination of the superficial fecal subsamples. Pollen concentration and percentage values evidenced high pollen abundance of: a) Asteraceae subfam. Asteroideae-Senecio type, Mulinum spinosum and Rumex in summer feces; b) Poaceae in autumn feces; c) Empetrum rubrum in winter feces; and d) Nassauvia, Plantago and Poaceae in spring feces. Seasonality variations in the feces were related to the phenology of plants, to variations in the diet and to the supply of palatable resources for L. guanicoe. This seasonal feces model will be useful as an analog in studies on Holocene camelid coprolites found in Cerro Casa de Piedra (PMNP) sites. It will allow clarifying the seasonality in site use. On the other hand, it will contribute data to the L. guanicoe´s diet, which represent an important information for the species´ regional sustainable management. Fil: Velázquez, Nadia Jimena. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Biología. Laboratorio de Palinología y Bioantropología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina Fil: Burry, Lidia Susana. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Biología. Laboratorio de Palinología y Bioantropología; Argentina

The present paper describes and illustrates features of Empetrum rubrum epidermis and transverse leaf section. It also describes and quantifie siliceous and calcium phytoliths.Biomineralization quantification is expressed as the media biomineral content (% from dry weight) withvalues of 1.58% ± 0.51 in silica phytoliths and 0.82% in calcicum phytoliths. E. rubrum is a native species from the austral end of South America. We here compare features of its leaf anatomy and biomineralization quali-quantifications with those from E. nigrum, a native species fromthe northern hemisphere. The comparison between the characters described for this species and those from macroremains and phytoliths recovered from surface soils provides valuable tools for taxonomical, ecological, paleontological and paleoecological studies. Knowledge of said charactersfurther provides valuable information to infer changes in plant communities in the recent past as well as insight into the environmental and soil conditions at the time when such changes took place. En este trabajo se describe e ilustra las características anatómicas de la epidermis y transcorte de hoja de Empetrum rubrum. Se han descrito y cuantificado a los cuerpos silíceos y cálcicos. La cuantificación de biomineralizaciones se expresa en valores medios del contenido de biominerales (% en peso seco) obteniéndose valores de 1,58% ± 0,51 correspondientes a silicofitolitos (biomineralizaciones silíceas) y 0,82% de calciofitolitos (biomineralizaciones cálcicas). La especie E. rubrum es nativa del sur de América del Sur, sus características anatómico foliares y los caracteres cuali-cuantitativos de sus biomineralizaciones han sido comparados con los de E. nigrum nativa del Hemisferio Norte. Los caracteres descriptos para esta especie, al compararlos con macrorestos o silicofitolitos recuperados en suelos recientes, constituyen herramientas de gran valor en estudios de taxonomía, de ecología, paleontología y paleoecología, aportando datos importantes para determinar las modificaciones pasadas de estas comunidades vegetales, como así también, las condiciones ambientales y del suelo en que se produjeron dichas modificaciones. Fil: Fernández Pepi, María Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Arriaga, Mirta Olga. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Zucol, Alejandro Fabián. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; Argentina

The relationship of environmental and soil-nutrient variables with the floristic composition of Empetrum rubrum heathlands and related communities from northern Tierra del Fuego were studied by means of ordination techniques. A floristic gradient was found which had its axis of major variation closely related to a gradient in soil trophic status. Increases in the densities of Empetrum and other cushion plants (Bolax gummifera, Azorella lycopodioides, Pernettya pumila) along the floristic gradient were: (a) associated with a lower number of species and total cover, and greater soil erosion; (b) positively correlated with the C/N ratio and aluminium content in the soil; and (c) negatively correlated with pH, calcium content and base saturation.

In the above-timberline zone of south-central Chile, stepped microtopography commonly develops on slopes of unstable volcanic ash deposits. Between the Nothofagus timberline and the high-altitude sparse fellfields, a scrubgrassland vegetation dominated by prostrate shrubs such as Empetrum rubrum and Pernettya spp. and tussock grasses such as Hierochloe utriculata and Cortaderia pilosa characteristically occurs on the stepped microtopography. Species interactions and species-microtopography interactions during the course of succession on the recent volcanic deposits were investigated by means of pattern analysis. Scales of pattern associated with individual plant morphology and interspecific interactions are present but, in general, the scales of pattern attributed to environmental variation are more evident. Cyclic changes occur in the scrub-grassland under the influence of periodic burial by the unstable ash substrate and the life cycles of the dominant prostrate shrubs. Such cyclic changes are part of a long-term linear successional trend following disturbance by catastrophic vulcanism. In contrast to the basic assumption of classic successional theory, in both the short-term and long-term the physical habitat in the above-timberline zone of south-central Chile is fundamentally unstable.