High-Andean vegetation and environmental gradients in northwestern Patagonia,Argentina

Abstract. We analysed the heterogeneity of high-elevation vegetation on three mountains along a west-east transect at 41 °S lat. in the Andes of northwestern Patagonia, Argentina. In this area, high-Andean vegetation occurs as islands on mountain tops above Nothofagus pumilio forests ? with the timberline at ca. 1700 m a.s.l. We recorded floristic, topographic and substrate data in 166 sites stratified according to longitude, altitude, slope and aspect. Vegetation data were classified with TWINSPAN and ordinated with Detrended Correspondence Analysis. The relationship between environmental and floristic variation was analysed using Canonical Correspondence Analysis. In order of importance, geographical longitude, altitude and aspect were the major determinants of vegetation variation, whereas substrate texture and slope appeared less important. The combination of these factors resulted in two main vegetation gradients. The first gradient is related to a moisture availability gradient, primarily determined by longitude and secondarily to variation in wind exposure (east vs. west aspect). The second vegetation gradient is related to variation in temperature, primarily determined by altitude, and secondarily by variation in insolation related to the contrast between north and south aspects. The four communities obtained with TWINSPAN are therefore associated with four characteristic habitat types: moist-cold, moist-warm, dry-cold and dry-warm. The community of warm and dry environments is the richest and has elements in common with dry steppe communities situated at lower elevations to the east, while the vegetation of the cold-moist habitat type has unique elements that are typical of the southern Andes. Although current climatic factors appear to be the major determinants of high-Andean vegetation gradients, historical events of Pleistocene times probably also affected the vegetation patterns we see today.     

Soil seed bank in and between vegetation patches in arid Patagonia,Argentina

This study was conducted at two sites, 1.5 km from 1 to another in arid Argentina (39°S, 69°W). Vegetation is distributed in patches. Four microenvironments can be identified in the soil surface of these patches, and the bare interspaces among them. Hypotheses were that (1) at any time during the sampling periods, buried (viable + damaged) seeds of the most common vegetation in the patches, Larrea divaricata Cav., Atriplex lampa Gill ex Moquin, Stipa neaei Nees ex Steudel and Leymus erianthus (Phil.) Dubcovsky, are present in the soil seed bank at all four microenvironments within any vegetation patch and its associated interspace, and (2) natural plant recruitment from the soil seed bank occurs for L. divaricata, A. lampa, S. neaei, L. erianthus, Bromus tectorum L. and Poa lanuginosa Poiret ap. Lamarck in all study microenvironments. In undisturbed field areas, 32 soil samples were periodically taken using an auger in 1999. Viable and damaged seeds contained in the soil organic matter were counted for L. divaricata, A. lampa, S. neaei, and L. erianthus. In a further study, emergence and subsequent growth of L. divaricata, A. lampa, S. neaei, L. erianthus, B. tectorum and P. lanuginosa from the soil seed bank were evaluated in the various microenvironments; permanent plots (0.04 m²) were placed on each of the two study sites using four vegetation patches and their associated interspaces per site. Results supported the first hypotheses only for L. divaricata and A. lampa. However, natural recruitment from the soil only included S. neaei and P. lanuginosa through asexual, and B. tectorum through sexual reproduction. Despite the presence of buried seeds of L. divaricata and A. lampa in microenvironment 4 during most of the sampling period, bare interspaces among vegetation patches can be naturally vegetated through sexual reproduction by B. tectorum, during years of abundant, higher than long-term, annual precipitation.     

Cultural transmission of ethnobotanical knowledge in a rural community of northwestern Patagonia, Argentina

In the present study we analyzed medicinal and edible plant utilization in Cuyin Manzano, a small rural population located near the Andean forests of Argentina. We also studied where and when plant knowledge was learned, who the principal transmitters were, and how people were taught. The participants were interviewed individually and at random, by means of a semi-structured questionnaire. Interviews were carried out in 16 families in order to examine the present use of wild plants. The inhabitants of Cuyin Manzano cited 87 plants: 63 medicinal and 24 edible species. They mentioned on average 31 ± 10 species per person. Similar patterns of plant use were found in young and old people alike, irrespective of gender. Learning about useful plants took place at an early age as a result of family tradition. This local knowledge is acquired and taught “by doing,” and is mostly transmitted vertically through family dissemination. Wild plant learning implies the acquisition of plants' physical and functional features as well as their environmental characteristics.     

Synergistic influences of introduced herbivores and fire on vegetation change in northern Patagonia,Argentina

Question: We investigated how cattle and European hares, the two most widespread exotic herbivores in Patagonia, affect species composition, life‐form composition and community structure during the first 6 years of vegetation recovery following severe burning of fire‐resistant subalpine forests and fire‐prone tall shrublands. We asked how the effects of introduced herbivores on post‐fire plant community attributes affect flammability of the vegetation. Location: Nahuel Huapi National Park, northwest Patagonia, Argentina Methods: We installed fenced plots to exclude livestock and European hares from severely burned subalpine forests of Nothofagus pumilio and adjacent tall shrublands of N. antarctica. The former is an obligate seed reproducer, whereas the latter and all other woody dominants of the shrubland vigorously resprout after burning. Results: Repeated measures ANOVA of annual measurements over the 2001‐2006 period indicate that cattle and hare exclusion had significant but complex effects on the cover of graminoids, forbs, climber species and woody species in the two burned community types. Significant interactions between the effects of cattle and hares varied by plant life forms between the two communities, which implies that their synergistic effects are community dependent. Conclusions: Following severe fires, the combined effects of cattle and hares inhibit forest recovery and favour transition to shrublands dominated by resprouting woody species. This herbivore‐induced trend in vegetation structure is consistent with the hypothesis that the effects of exotic herbivores at recently burned sites contribute to an increase in the overall flammability of the Patagonian landscape.     

Vertebral pneumatic structures in the Early Cretaceous sauropod dinosaur Pilmatueia faundezi from northwestern Patagonia,Argentina

One of the diagnostic characters of dicraeosaurid sauropods is a reduction of pneumatization of dorsal and caudal vertebrae relative to their Flagellicaudata sister taxon, Diplodocidae. Here, we analyse pneumatic structures in the dicraeosaurid sauropod Pilmatueia faundezi, compare them to those of diplodocoids and report the first record of camerate chambers in a dicraeosaurid. The pneumatic structures are in a posterior cervical centrum (MLL-Pv-002) and consist of lateral pneumatic fossae on the centrum that communicate internally with large camerae. By contrast, Pilmatueia's dorsal and caudal vertebrae (MLL-Pv-005-016) lack pneumatic fossae on the centra, which is consistent with the previously reported reduced pneumaticity in dicraeosaurids. Nevertheless, the base of the neural arch and possibly the base of the bifid neural spines of a posterior dorsal vertebra (MLL-Pv-005) show pneumatic internal chambers. The pneumatic features of the Pilmatueia cervical centrum and dorsal neural arch we describe indicate that the degree of pneumatization is variable within dicraeosaurids.     

Vegetation disturbance by fire affects plant reproductive phenology in a shrubland community in northwestern Patagonia, Argentina

Reproductive phenology is likely to vary spatially with environmental conditions that alter microclimate, in particular temperature. We hypothesized that within the same plant community type, environmental changes produced by recent burning would alter plant phenological patterns and temporal structure of the plant community. Specifically, we predicted accelerated flowering and fruiting dates in the burned, open environment compared with the unburned, intact community. We tested this hypothesis in a post-fire tall shrubland (matorral) in northwestern Patagonia, Argentina. During the reproductive season, phenological stages of seven vascular plant species were monitored weekly. Temperature, humidity, soil nutrients and photosynthetically-active radiation were also recorded. At the burned site, flowering began earlier in all species and the success rate of fruiting was higher. These patterns correlated with significant environmental differences, including higher mean temperatures at the burned site.     

The impact of livestock grazing on the spatial pattern of vegetation in north-eastern Patagonia,Argentina

Background: The occurrence of shrub patches, alternating with either bare soil or low herbaceous cover, is a common feature in arid and semi-arid shrublands throughout the world. This patchy pattern of vegetation may result from water limitation, modulated by plant interactions; grazing (offtake and tramping) by livestock may cause further patchiness vegetation structure.

Aims: We hypothesised that vegetation patchiness in the semi-arid shrublands of north-eastern Patagonia would be increased by livestock grazing, but not by positive interactions between adult plants of shrubs and grasses.

Methods: We compared vegetation cover and pattern at three grazing intensities (exclosure, light and heavy grazing) and measured the growth of a representative shrub and grass in the presence and absence of the other to quantify the role of plant-to-plant interactions and its interaction with grazing for vegetation structure.

Results: In the grazing exclosure and in moderately grazed areas, vegetation cover among shrub patches was larger, whereas the top cover of shrubs was lower than in the heavily grazed areas. We did not find any evidence of positive interactions between shrub and grass life forms.

Conclusions: Our results were consistent with the hypothesis that livestock grazing increased the formation of patchy vegetation cover in arid and semi-arid shrublands.     

Afforestation causes changes in post‐fire regeneration in native shrubland communities of northwestern Patagonia,Argentina

Question: What are the effects of fire in native shrubland communities and in pine plantations established in these shrublands? Location: Northern Patagonia, Argentina. Methods: We surveyed four sites in Chall‐Huaco valley, located in northwest Patagonia. Each site was a vegetation mosaic composed of an unburned Pinus ponderosa plantation, a plantation burned in 1996, and an unburned matorral and a matorral burned by the same fire. We recorded the cover of all vascular plant species. We also analysed species richness, total cover, proportion of exotic species, abundance of woody species and herb species, cover of exotic species, abundance of woody and herb species and differences in composition of species. For both shrubs and tree species we recorded the main strategy of regeneration (by resprouting or by seed). Results: We found that fire had different effects on native matorral and pine plantations. Five years after fire, plantations came to be dominated by herbs and exotic species, showing differences in floristic composition. In contrast, matorral communities remained very similar to unburned matorral in terms of species richness, proportion of woody species, and herb species and proportion of exotics. Also, pine plantations were primarily colonized by seedlings, while matorrals were primarily colonized by resprouting. Conclusions: Matorrals are highly fire resilient communities, and the practice of establishing plantations on matorrals produces a strong reduction in the capacity of matorral to return to its original state. The elimination of shrubs owing to the effect of plantations can hinder regeneration of native ecosystems. Burned plantations may slowly develop into ecosystems similar to the native ones, or they may produce a new ecosystem dominated by exotic herbs. This study shows that plantations of exotic conifers affect native vegetation even after they have been removed, as in this case by fire.     

First study of fossil rodent middens as source of paleoparasitological evidences (northwestern Patagonia,Argentina)

The present paper reports the first paleoparasitological results obtained from coprolites of fossil rodent middens and demonstrates the potential of rodent middens as a source of paleoparasitological evidences in South America. Ten fossil rodent middens from northwestern Patagonia, Argentina, were studied. Five coprolites of each midden were fully processed, rehydrated, homogenized, subjected to spontaneous sedimentation, and examined through light microscopy. Eight of the 10 examined rodent middens contained parasite eggs. The eggs of parasites were assigned to Heteroxynema (Cavioxyura) viscaciae Sutton & Hugot, 1989 and Helminthoxys sp. (Nematoda: Oxyuridae), Trichuris sp. (Nematoda: Trichuridae) and one unidentified nematode. Fossil rodent middens were assigned to Lagidium viscacia (Caviomorph: Chinchillidae). The excellent preservation of parasite remains in coprolites from fossil rodent middens provided an opportunity to perform paleoparasitological inferences. The results of this papers demonstrates that fossil rodent middens offer an excellent opportunity for the recovery of parasite remains for future paleoparasitological studies in the southwest of South America.     

Presence of Pleurotus ostreatus in Patagonia,Argentina

Specimens belonging to the genus Pleurotus were collected growing on fallen trunks of Araucaria araucana, a native tree with a poorly known mycoflora, which grows in Patagonia, Argentina. Fruitbodies were produced in culture on sawdust from an isolated strain. Interspecific pairing tests performed between mating types of Pleurotus from Patagonia and tester strains of P. pulmonarius and P. ostreatus showed the Patagonia strain to be 100% compatible with P. ostreatus and incompatible with P. pulmonarius. Dikaryons obtained on sawdust were fertile, since they were able to produce fruitbodies and viable spores. This is the first documented record of P. ostreatus from Argentina and the first gilled fungus found growing on Araucaria araucana.     

Nest-site habitat selection by Lesser Rheas ( Rhea pennata pennata ) in northwestern Patagonia, Argentina

Selection of nest-site habitat by a population of wild Lesser Rheas (Rhea pennata pennata) was studied in the northwestern Patagonia steppe, Argentina, during two reproductive seasons (2004/2005 and 2005/2006). Nest spatial distribution was compared with randomly selected points in the study area. Contrary to observations in other ratite species, nest distribution showed an aggregate pattern associated with “mallín” (meadow) areas, which are habitats of higher productivity in the Patagonia steppe. Moreover, similar to observations made on the Greater Rhea (Rhea americana), vegetation cover was higher in nest sites than in randomly selected sites, probably because higher vegetation provides concealment from predators and protection from the strong westerly winds that frequent in this region. Our results reinforce the importance of “mallín” areas for the reproduction and conservation of this threatened ratite species.     

Yeast communities associated with the bulk-soil, rhizosphere and ectomycorrhizosphere of a Nothofagus pumilio forest in northwestern Patagonia, Argentina

Soil microorganisms play an important role in soil quality and they interact closely with vegetation. Little is known about yeast diversity and function in forest soil ecosystems and their interactions with other biotic soil components, particularly in the mycorrhizosphere. We studied the diversity of yeasts inhabiting the bulk-soil, rhizosphere and ectomycorrhizosphere of a Nothofagus pumilio forest in Nahuel Huapi National Park (Bariloche, Argentina). Ectomycorrhizal infection was observed in all N. pumilio trees studied. A total of 126 yeast isolates were obtained, including 18 known and three possibly new species. Basidiomycetous yeasts were predominant in all soil fractions, and the most frequently isolated species was Cryptococcus podzolicus. Diversity indices and multivariate analyses were used to study and compare yeast communities in the bulk-soil, rhizosphere and ectomycorrhizosphere. Yeasts able to ferment glucose were found associated with the rhizosphere. Many of the recovered yeast species were associated with lignocelluloses compound degradation, which suggest that yeast plays an important role as a decomposer in these forest soils. Each soil fraction has a distinct yeast assemblage related to their physiologic capacities and soil nutrient availability.     

A Perplexing Outbreak of Mice in Patagonia,Argentina

Early in spring, 1997, remarkably large numbers of mice appeared in the dense forests near the western end of Lago Nahuel Huapi, Argentina. Dead mice that washed up on nearby beaches at this time were fat, had full stomachs and were young or young-adults born unusually late in the preceding autumn and winter. These mice represented an aperiodic outbreak that extended over 300 km along the Andes. By analysis of trapped samples, the demographics of the two main species in this outbreak (Oligoryzomys longicaudatus and Abrothrix longipilis) were compared with demographics of the same species during the preceding 21 years. In spring of 1997, trap success for O. longicaudatus in areas of the outbreak was as high as 46%; for A. longipilis it was 22%. Neither males nor females of either species entered breeding condition in 1997 during the usual season of reproduction in spring, nor in the following summer, leading to the collapse of the populations. Numbers of Oligoryzomys decreased steadily to 15% in autumn and a normal 2% in the following spring, at which time reproduction resumed. The 1997 springtime populations in adjacent ecotone and steppe habitats to the east had not increased, contained no young individuals, and overwinter individuals reproduced normally. During the breeding season, O. longicaudatus in these populations increased more rapidly than did A. longipilis, and during the winter, they decreased faster. The unusual winter reproduction preceding the outbreak may have resulted from an increase in some deep-forest food source that in turn was responding to two successive, unusually warm winters. Predation played a negligible role in the population collapse. The mouse outbreak was not accompanied by an increase in human cases of hanta pulmonary syndrome, a disease for which O. longicaudatus is a reservoir.     

A hot-spot of biodiversity in Northern Patagonia,Argentina

Located along the Argentine coastline of northern Patagonia, are San Matías (SMG) and San José (SJG) gulfs; although they are regarded as an area with a high-priority conservational status, knowledge on their diversity is currently fragmentary. Studies on molluscs from this area have been historically centred in economic resources and few works have referred to non-commercial species. The present study aims to document the biological diversity of molluscs at the SMG/SJG area, in order to determine the significance of these two gulfs in the context of the Argentine marine fauna; to evaluate how well represented is this fauna in three protected areas; and to compare the fauna present in the protected areas with that of a non-protected area. For that purpose, molluscs coming from 132 sampling stations, ranging from the intertidal to 170 m depth, were studied, and a thorough bibliographic compilation was performed. A total of 196 species of molluscs are reported for the area. Surprisingly, almost one third of these species lacked previous records for SMG/SJG, including several new/possibly new species. The three studied protected areas contain 88.3% of the species recognised for the entire SMG/SJG area. Although several species appear as exclusive from one of these three areas, many of them are also present in an intermediately located, non-protected area. Molluscan diversity at the SMG/SJG area is greater than previously thought, comprising about 41.4% of the bivalves and 37.8% of the gastropods present in the Argentine shelf; thus suggesting that the area may be considered as a hot-spot of diversity in the Argentine Sea.     

Late Cretaceous Aquatic Plant World in Patagonia,Argentina

In this contribution, we describe latest Cretaceous aquatic plant communities from the La Colonia Formation, Patagonia, Argentina, based on their taxonomic components and paleoecological attributes. The La Colonia Formation is a geological unit deposited during a Maastrichtian-Danian transgressive episode of the South Atlantic Ocean. This event resulted in the deposition of a series of fine-grained sediments associated with lagoon systems occurring along irregular coastal plains in northern Patagonia. These deposits preserved a diverse biota, including aquatic and terrestrial plants and animals. The aquatic macrophytes can be broadly divided into two groups: free-floating and rooted, the latter with emergent or floating leaves. Free-floating macrophytes include ferns in Salviniaceae (Azolla and Paleoazolla) and a monocot (Araceae). Floating microphytes include green algae (Botryoccocus, Pediastrum and Zygnemataceae). Among the rooted components, marsileaceous water ferns (including Regnellidium and an extinct form) and the eudicot angiosperm Nelumbo (Nelumbonaceae) are the dominant groups. Terrestrial plants occurring in the vegetation surrounding the lagoons include monocots (palms and Typhaceae), ferns with affinities to Dicksoniaceae, conifers, and dicots. A reconstruction of the aquatic plant paleocommuniy is provided based on the distribution of the fossils along a freshwater horizon within the La Colonia Formation. This contribution constitutes the first reconstruction of a Cretaceous aquatic habitat for southern South America.     

Eimeriid oocysts from archaeological samples in Patagonia, Argentina

Oocysts attributable to E. macusaniensis Guerrero et al. 1971, were found in coprolites and in archaeological sediments dating to the Holocene of Patagonia, Argentina. By means of a non-parametric regression using a generalized additive model, a significant relationship was found between the size of the oocysts and their antiquity. Specifically, a reduction in oocyst size over time was discovered, probably due to a parasite response to host replacement, to an extinct eimeriid species common during the Pliestocene-Holocene transition, or to environmental changes known for the Holocene. Explanations regarding coevolution between parasites, hosts and paleoenvironmental conditions are discussed herein.     

The biology of Mustelus schmitti in southern Patagonia, Argentina

The relationship of body weight and total length (L_T) of Mustelus schmitti in southern Patagonia was different between sexes. Changes in maturity stages in males appear at larger sizes in Ría Deseado specimens than in the Mar del Plata area. Mature females ranged from 795 to 913 mm while all male specimens >759 mm L_T were mature. The data suggest that mating occurs before parturition, with simultaneous ovulation. The diet of adult M. schmitti was mainly carcinophage and the diet of young-of-the-year and adults differed. The young-of-the-year use the Ría Deseado as a pupping area.     

Lower Permian bivalves from central Patagonia, Argentina

The earliest Permian faunal successions of central Patagonia show compositional changes that probably reflected the environmental warming at the end of the Gondwana glaciations. Bivalves of Asselian to probably Early Tastubian age are described. A new genus,Sueroa, is proposed to reunite a previously known species and a new species,Sueroa andreisi n. sp. Another five new species:Parallelodon? quichaurensis n. sp.,Heteropecten cortignasi n. sp.,Etheripecten saraviae n. sp.,Streblopteria montgomeryi n. sp. andPraeundulomya moreli n. sp. are described. Two previously known species:Malimania patagoniensis (González) andEuchondria sabattiniae González are revised and new occurrences are reported. A further eleven species are described, but they are left in open nomenclature being because they are insufficiently known; these are:Phestia? n. sp.,Modiolus sp.,Palaeoneilo sp.,Stutchburia sp.,Schizodus sp.,Vacunella? sp.,Edmondia sp.,Myonia? n. sp.,Myonia? sp. andPachymyonia? n. sp.     

Monoterpene emissions from three Nothofagus species in Patagonia,Argentina

Abstract

Isoprenoid emissions have key roles in plant biology and plant interactions with the environment. Global emission inventories of isoprenoid emissions still lack information from a large number species, especially from South American vegetation other than the rainforest ecosystem. A study was conducted to identify the basal emission of isoprenoid under field conditions from three Nothofagus species. The three Nothofagus species were characterized as strong monoterpene emitters while the emission of isoprene was undetectable. The two deciduous species, N. pumilio and N. antarctica, had similar photosynthetic parameters, but monoterpene emission rate and, consequently, the fraction of photosynthetic carbon re-emitted in the atmosphere as monoterpenes, were more than three-fold higher in N. pumilio than in N. Antarctica. The evergreen species N. dombeyi showed intermediate values of both monoterpene emission rate and fraction of photosynthetic carbon re-emitted. The monoterpene emission spectrum was very similar among the three Nothofagus species screened, but clearly different from the spectrum reported in other monoterpene-emitting species of the Fagaceae family. The importance of these findings for atmospheric chemistry and phylogenic evolution are discussed.