Seed bank patterns of Festuca pallescens in semiarid Patagonia (Argentina): a possible limit to bunch reestablishment

The pre- and postdispersal spatial patterns of the germinable seed bank of Festuca pallescens were evaluated in semiarid grasslands of Patagonia disturbed by sheep grazing. Before dispersal, the seed bank showed spatial heterogeneity and was significantly smaller than the postdispersal seed bank. The postdispersal seed bank was uniformly distributed in patches of bare soil. The size of the germinable seed bank varied with the topographic condition of sites. On slopes, bunches exhibited more panicles and the germinable seed bank was larger after dispersal and smaller before dispersal as compared with upland sites. Losses of the germinable seed bank during autumn and spring are partially accounted for by germination rates. Predominant westerly winds influenced the patterns of seed dispersal, but other agents such as predation or sheet wash may also be active, especially on slopes. The low persistence of the seed bank of F. pallescens, particularly at canopy gaps, indicates that this may constitute a primary control of the regeneration of this species in semiarid grasslands of Patagonia. Management of these grasslands for restoration should accordingly include practices oriented to an adequate replenishment of the germinable seed bank at these places.     

Notes on Erysiphales (Ascomycetes) from Patagonia, Argentina

Fifteen Erysiphaceous taxa found on 20 host plant species in Patagonia are documented. A new species Oidium maculatae (type host: Viola maculata) is described. Berberis linearifolia, Buddleja globosa, Prosopis alpataco and Viola maculata, are new host plants for Erysiphales. Three new combinations on fungi and host plant species were founded: Erysiphe howeana – Fuchsia magellanica; E. patagoniaca – Nothofagus pumilio and N. antarctica. The genus Sawadaea and the species S. bicornis on Acer negundo and A. pseudoplatanus, are new records for South America. New host plants recorded for Argentina: Consolida ajacis, Galega officinalis and Plantago lanceolata. New host plants recorded for Patagonia: Galium aparine, Melilotus albus, Petunia × hybrida, Potentilla anserina, and Spiraea × bumalda. Oidium longipes is a new record for Argentina and Golovinomyces riedlianus is a new record for Patagonia.     

Variations in the periphytic community structure and dynamics of Lake Nahuel Huapi (Patagonia,Argentina)

Little is known about periphyton community in Patagonia and the influence that urban development has on a particular water body. Lake Nahuel Huapi is located in a National Park with little industrial or agricultural activity in the basin, but it is influenced by urban discharges from San Carlos de Bariloche, a town of 80000 inhabitants located on its south shore. Variations in structure and dynamics of the periphyton community in Lake Nahuel Huapi were studied during 1 year, to examine the influence of urban discharges on this community. Periphyton samples were collected on the shoreline of the lake and evaluated for biomass (as chlorophyll a concentration) and cell density of the main algal groups, at sites with and without urban influence. Results indicated the major influence of pollution from urban sources on periphyton at the most impacted sites, as well as the effect of different local events at each site (degree of contamination, type of coast, wind exposure, etc.). Higher biomass and cell densities at contaminated sites were evident, but the variation of main algal groups through the year was similar in all the sites. Periphyton in Lake Nahuel Huapi proved to be an important bioindicator of urban impacts on this water body.     

Influence of crude oil on changes of bacterial communities in Arctic sea-ice

The danger of a petroleum hydrocarbon spillage in the polar, ice-covered regions is increasing due to oil exploration in Arctic offshore areas and a growing interest in using the Northern Sea Route (NSR) as an alternative transportation route for Arctic oil and gas. However, little is known about the potential impact of accidental oil spills on this environment. We investigated the impact of crude oil on microbial community composition in six different Arctic sea-ice samples incubated with crude oil at 1 degrees C in microcosms for one year. Alterations in the composition of bacterial communities were analyzed with the culture-independent molecular methods DGGE (denaturing gradient gel electrophoresis) and FISH (fluorescence in situ hybridization). DGGE, FISH and cultivation methods revealed a strong shift in community composition toward the gamma-proteobacteria in sea-ice and melt pool samples incubated with crude oil. Marinobacter spp., Shewanella spp. and Pseudomonas spp. were the predominant phylotypes in the oil-treated microcosms. The ability of indigenous sea-ice bacteria to degrade hydrocarbons at low temperature (1 degrees C) was tested using four representative strains cultivated from sea-ice enriched with crude oil. [14C]Hexadecane was degraded by the sea-ice isolates at 20-50% capacity of the mesophilic type strain Marinobacter hydrocarbonoclasticus, a known hydrocarbon degrader, incubated at 22 degrees C.     

Land degradation affects shrub growth responses to precipitation in a semiarid rangeland of north‐eastern Patagonia (Argentina)

Arid land degradation diminishes the proportion of precipitation conducted to infiltration and increases the proportion lost to run‐off and evaporation. Consequently, we expect that the effects of annual precipitation on shrub growth vary with land degradation as a result of changes in soil available water. Chuquiraga avellanedae is the dominant shrub and the main indicator of land degradation in semiarid rangelands of north‐eastern Patagonia. We chose two communities with a different degree of land degradation: an herbaceous steppe with shrubs (HSS) and a degraded shrub steppe (SS). Vegetative growth of C. avellanedae was determined nondestructively using a double‐sampling approach. Soil water content was estimated for the two communities using a soil water balance model. Linear regressions were used to evaluate the relationships between shrub growth and (i) annual precipitation and (ii) mean available water during the period of high vegetative growth in the soil layer that each plant community concentrates their roots. In SS, with elevated clay content, there were more roots of C. avellanedae in the upper layers of soil while in HSS, with coarse‐textured soil, C. avellanedae had more roots in deeper layers. Vegetative growth of C. avellanedae, both in HSS and SS communities, was positively related to annual precipitation but, for a given precipitation, C. avellanedae presented higher vegetative growth in HSS than in SS. We also found a positive relationship between vegetative growth and soil available water, and this relationship did not differ between communities. SS presented lower water availability because of lower infiltration rates. Our results showed that, irrespective of the degree of land degradation, plants respond directly to water content of the soil layers where most roots are present at a specific window of time.     

不同类型原油污染土壤生物修复技术研究

对不同类型原油污染土壤在实用规模的预制床上采用堆制技术进行生物修复 .通过投加肥料、菌剂、控制水分和pH ,可使微生物获得较好的生态环境 .当稀油、高凝油、特稠油和稠油污染的土壤中原油总量为 2 5 .8～ 77.2 g·kg-1土时 ,经过近 2个月的运行 ,石油总量的去除率可达 38.37%～ 5 6 .74 % .石油中芳烃、沥青和胶质混合物是制约石油快速降解的主要因素 .在处理过程中筛选出石油降解的优势菌株 ,其中有 6株真菌、6株细菌和 1株放线菌 .研究结果为石油污染土壤异位生物修复技术实用化提供了理论依据 .     

Palynological characterization of honeys from the Andean Patagonia (Chubut,Argentina)

The pollen content of 58 honey samples of Apis mellifera L. from the Andean region of Chubut (Argentinian Patagonia) was analyzed. The samples were provided by beekeepers between 1999 and 2004. Eighty‐eight pollen types were identified, 30 of them are not reported in Argentinian honeys. Identified types belong to 47 families, of which the most diverse were Asteraceae (15 pollen types), Fabaceae (13 pollen types), and Rosaceae (four pollen types). From the samples analyzed, 47% were monofloral and corresponded to the following taxa: Trifolium spp. (16%), Rosaceae (10%), Aristotelia chilensis (Molina) Stuntz (7%), Discaria‐Colletia (5%), Escallonia spp. (3%), Schinus patagonica (Phil.) I. M. Johnst. (2%), Phacelia secunda J. F. Gmel. (2%), Myrtaceae (2%). The results of this study show a high level of utilization of native flora by Apis mellifera. Four new types of monofloral honey were recognized: Aristotelia chilensis, Discaria‐Colletia, Phacelia secunda, and Schinus patagonica. The high representation of native flora distinguishes these honeys geographically.     

Influence of chemical surfactants on the biodegradation of crude oil by a mixed bacterial culture.

The effects of surfactant physicochemical properties, such as the hydrophile-lipophile balance (HLB) and molecular structure, on the biodegradation of 2% w/v Bow River crude oil by a mixed-bacterial culture were examined. Viable counts increased 4.6-fold and total petroleum hydrocarbon (TPH) biodegradation increased 57% in the presence of Igepal CO-630, a nonylphenol ethoxylate (HLB 13, 0.625 g/L). Only the nonylphenol ethoxylate with an HLB value of 13 substantially enhanced biodegradation. The surfactants from other chemical classes with HLB values of 13 (0.625 g/L) had no effect or were inhibitory. TPH biodegradation enhancement by Igepal CO-630 occurred at concentrations above the critical micelle concentration. When the effect of surfactant on individual oil fractions was examined, the biodegradation enhancement for the saturate and aromatic fractions was the same. In all cases, biodegradation resulted in increased resin and asphaltene concentrations. Optimal surfactant concentrations for TPH biodegradation reduced resin and asphaltene formation. Chemical surfactants have the potential to improve crude oil biodegradation in complex microbial systems, and surfactant selection should consider factors such as molecular structure, HLB, and surfactant concentration.     

Fossil moonseeds from the Paleogene of West Gondwana (Patagonia,Argentina)

Premise of the Study

The fossil record is critical for testing biogeographic hypotheses. Menispermaceae (moonseeds) are a widespread family with a rich fossil record and alternative hypotheses related to their origin and diversification. The family is well‐represented in Cenozoic deposits of the northern hemisphere, but the record in the southern hemisphere is sparse. Filling in the southern record of moonseeds will improve our ability to evaluate alternative biogeographic hypotheses.

Methods

Fossils were collected from the Salamanca (early Paleocene, Danian) and the Huitrera (early Eocene, Ypresian) formations in Chubut Province, Argentina. We photographed them using light microscopy, epifluorescence, and scanning electron microscopy and compared the fossils with similar extant and fossil Menispermaceae using herbarium specimens and published literature.

Key Results

We describe fossil leaves and endocarps attributed to Menispermaceae from Argentinean Patagonia. The leaves are identified to the family, and the endocarps are further identified to the tribe Cissampelideae. The Salamancan endocarp is assigned to the extant genus Stephania. These fossils significantly expand the known range of Menispermaceae in South America, and they include the oldest (ca. 64 Ma) unequivocal evidence of the family worldwide.

Conclusions

Our findings highlight the importance of West Gondwana in the evolution of Menispermaceae during the Paleogene. Currently, the fossil record does not discern between a Laurasian or Gondwanan origin; however, it does demonstrate that Menispermaceae grew well outside the tropics by the early Paleocene. The endocarps’ affinity with Cissampelideae suggests that diversification of the family was well underway by the earliest Paleocene.     

A new baurusuchid crocodyliform (Archosauria) from the Late Cretaceous of Patagonia (Argentina)

A new baurusuchid, Wargosuchus australis gen. et sp. nov., coming from the Bajo de La Carpa Formation, Neuquén Province (Argentina), is described. This new taxon is based on a fragment of snout and a portion of the cranial roof. Wargosuchus differs from other crocodyliforms by possessing a deep median groove on the frontals, a contact between nasals and frontals extremely reduced, a large depression for the olfactory bulbs, three large foramina surrounding the large, smooth perinarial depression, and a hypertrophied, conical last premaxillary tooth followed by a large paracanine fossa. The finding of Wargosuchus in Patagonia (Argentina), a taxon with a strong resemblance to Brazilian baurusuchids, reinforces the hypothesis of a similar biota between both regions by the Late Cretaceous. Wargosuchus and Cynodontosuchus represent the only Argentinian mesoeucrocodylians to be included within Baurusuchidae. This finding extends the number of crocodyliforms from the Bajo de la Carpa Formation, which, in turn, corresponds to the most taxonomically diverse one in Argentina.     

Adaptation of the bacterial community to mercury contamination

The utilisation of 31 sole carbon sources by bacterial communities of soil in the presence of increasing concentrations of Hg(II) was measured by a colour development assay. The assay was performed on Biolog microtitre plates (Ecoplates) in the presence of Hg(II) and compared to Hg(II)-free Ecoplates. Furthermore, community tolerance to Hg(II) was measured by colour development in microtitre plates supplemented with LB broth and by enumeration of colony-forming units on LB agar plates. Both microtitre plates supplemented with LB and LB agar plates contained increasing concentrations of Hg(II). The difference in substrate utilisation profile, as shown by growth on 31 different carbon substrates in the Ecoplates, suggested an adaptation of the soil community that correlated with the metal exposure level in the soil. Similarly, growth on microtitre plates supplemented with LB and plate-spreading data showed an increased community tolerance with increasing levels of mercury in the soil. Both the multi-function microtitre plate assay (Ecoplate) and the LB broth microtitre plate assay are suitable for evaluating the adaptation of the bacterial community in soil to a heavy metal pollutant.     

Salt leaching leads to drier soils in disturbed semiarid woodlands of central Argentina

Disturbances in semiarid environments have revealed a strong connection between water, salt and vegetation dynamics highlighting how the alteration of water fluxes can drive salt redistribution process and long-term environmental degradation. Here, we explore to what extent the reciprocal effect, that of salt redistribution on water fluxes, may play a role in dictating environmental changes following disturbance in dry woodlands. We assessed salt and water dynamics comparing soil-solution electrical conductivity, chloride concentration, soil water content (SWC) and soil matric and osmotic water potential (Ψ_m, Ψ_os) between disturbed and undisturbed areas. A large pool of salts and chlorides present in undisturbed areas was absent in disturbed plots, suggesting deep leaching. Unexpectedly, this was associated with slight but consistently lower SWC in disturbed versus undisturbed situations during two growing seasons. The apparent paradox of increased leaching but diminishing SWC after disturbance can be explained by the effect of native salt lowering Ψ_os enough to prevent full soil drying. Under disturbed conditions, the onset of deep drainage and salt leaching would raise Ψ_os allowing a decline of Ψ_m and SWC. Soil water storage seems to be modulated by the presence (under natural conditions) and partial leaching (following selective shrub disturbance) of large salt pools. This counterintuitive effect of disturbances may be important in semiarid regions where deep soil salt accumulation is a common feature. Our results highlight the importance of water–salt–vegetation coupling for the understanding and management of these systems.     

Isolation and characterization of indigenous soil bacteria for bioaugmentation of PAH contaminated soil of semiarid Patagonia, Argentina

The aim of this work was to isolate PAH degrading-bacteria from contaminated Patagonia soil with the ability to tolerate the usual environmental stresses (oligotrophic and dryness conditions). Two approaches were utilized to obtain PAH-degrading bacteria from the Patagonian soil. With a traditional enrichment approach only the PAH- degrading strain 36 was isolated. Using a direct isolation approach three PAH-degrading strains (1A, 22A and 22B) were isolated. The phylogenetic analysis revealed that all isolates belonged to Sphingomonas genus. The PAH degrading activity and the resistance to stress conditions of the strains were determined and compared with those of the exogenous PAH-degrading Sphingomonas paucimobilis 20006FA. The strains 1A, 22A and 36 were phylogenetically closely related between them and with the strain 20006FA. The strain 22B, that showed a different phylogenetic position, was more resistant to C-starvation and drying conditions than other Patagonian strains. The effect of the inoculation of these strains on phenanthrene-induced mineralization and elimination was studied in Patagonian soil artificially contaminated, at different environmental conditions. The results suggest that strain 22B is the most suitable strain for bioaugmentation in PAH-contaminated soils of Central Patagonia, due to its adaptation to the usual environmental conditions. Our results show the importance of a detailed physiological characterization of isolates for autochthonous bioaugmentation strategies success.     

Phyllactinia chubutiana: a new species of Erysiphales from Patagonia (Argentina)

Phyllactinia chubutiana, a parasite on leaves of Lycium chilense (Solanaceae) collected in the arid Patagonian steppe, is proposed as a new species. The new combination Ovulariopsis insolita is introduced for its anamorph previously described as Oidium insolitum.     

Seasonal and spatial distribution of stoneflies in the Chubut River (Patagonia, Argentina)

Longitudinal and seasonal distributions of Plecoptera species were examined along the Chubut River in the Patagonian Precordillera and Plateau, Argentina. Chubut River (>1000 km) is the largest river in the area and the hydrological regime is modified in the lower section by an artificial reservoir (Florentino Ameghino Dam). Quantitative samples were collected in 13 sites in the higher, middle, and lower sections of the river basin. Sites were visited four times during 2004, and a total of nine species and 5772 individuals were collected in the study. Plecoptera richness decreased dramatically from the headwaters to the mouth of the river system. Two species, Antarctoperla michaelseni and Potamoperla myrmidon, were able to live below the impoundment but they were not abundant. Notoperlopsis femina and A. michaelseni abundances were higher in summer than in the other seasons, while Limnoperla jaffueli peaked in spring. Species–environmental relationships were examined using Canonical Correspondence Analysis and six independent variables were identified as the major factors structuring stoneflies assemblages. First axis was highly related to environmental variables reflecting the hydro-geological and land use gradients in the basin (conductivity, total suspended solids, periphyton Chlorophyll a). Second axis was more related to variables that changed seasonally (wet width, water temperature and soluble reactive phosphate).     

The impact of an exotic social wasp (Vespula germanica) on the native arthropod community of north-west Patagonia, Argentina: an experimental study

Abstract 1. Biological invasions are usually thought to have a negative impact on native communities. However, data supporting this idea are often based on comparative studies between invaded and non‐invaded areas, and are spatially and temporally limited. 2. The present study experimentally assessed the impact of an exotic wasp, Vespula germanica, on the native arthropod community of north‐west Patagonia during 3 years in an area of 80 ha. Vespula germanica is an exotic social vespid that invaded north‐west Patagonia 20 years ago. It has been suggested that its populations affect native arthropods because of its broad diet and also because Patagonia lacks natural enemies and potential competitors for these wasps. 3. Using wasp‐specific toxic baits, V. germanica abundance was reduced in five sites of native woodlands during 3 consecutive years. The abundance, species richness, and composition of arthropods between non‐poisoned (control) and poisoned sites was then compared, both before and after the wasps were poisoned. 4. Wasp abundance represented 6% of the total arthropod catches in non‐poisoned sites and was reduced, on average, by 50% in the treated areas. The abundance, species richness, and composition of the arthropod community (305 species, 24 600 individuals) did not differ between control areas and areas where the abundance of V. germanica was reduced. Significant differences in response variables were found only before wasp poisoning had begun and were related to variations among sites. 5. These results suggest that V. germanica is not affecting the local arthropod assemblages, contradicting past work in other regions. The low relative abundance of wasps in Patagonia, when compared with other invaded regions, might explain the findings. 6. The present study provides further evidence for the importance of large‐scale experimental work with before/after comparisons to fully understand the impact of invaders on natural communities.     

Plankton and hydrochemistry of Lake Futalaufquen (Patagonia,Argentina) during the growing season

Plankton communities and hydrochemistry of an oligotrophic lake occupying a glacial valley in Argentinian Patagonia (42 °49S; 71 °43W) were studied. Monthly samples at three stations integrated from 0 to 50 m and stratified samples at the site of maximum depth, were taken during the growing season. Transparency was always controlled by glacial silt, and not by phytoplankton. Lake water belongs to the calcium-bicarbonate type, with low conductivity (24 µS cm^–1), and poor buffering capacity. Forty-five phytoplankton taxa were found. Mean phytoplankton density was 49 cells ml^–1 and mean biomass 69 µg l^–1. N:P relationships, inorganic nitrogen exhaustion in the photic layer, and correlations between nutrients and phytoplankton density suggests nitrogen as the main limiting factor. Fifteen zooplankton species were found. Mean zooplankton density was 12.2 ind. l^–1 and mean biomass 22.9 µg l^–1. Diatoms and Boeckellidae were the dominant planktonic groups. Morphometry and hydrological factors were responsible for horizontal heterogeneity in phytoplankton and chemical variables.     

Tolerance of garden angelica to soil contamination with crude oil

Garden angelica (Archangelica officinalis L.) tolerance to the action of Urals crude oil was studied. It was established that, at the oil dose up to 30 g/kg of soil, plant weight was increased and the photosynthetic apparatus was activated. Garden angelica manifested tolerance to oil dose up to 60 g/kg. It is proposed to use this plant for remediation of areas contaminated with oil products.     

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.