Patterns of alien plant invasions in northwestern Patagonia, Argentina

Invasive plant species are a growing concern in many regions of the world, yet little information is available on the effects of habitat type and distance to urban settlements on the ability of alien plants to become established. We studied plant communities from the arid steppes to the Andean forest within two national parks and surroundings, in northwestern Patagonia, Argentina. Alien and native vascular plant species were sampled using 90 × 100 m² plots and analyzed in relation to both climatic and environmental variables and distance to urban centres. We also compared life-forms of alien and native species. Precipitation and distance to an urban centre were important determinants of alien species community richness and composition, and shrubland sites had significantly more alien species than forest or steppe sites. Alien flora (15% of the species) was composed of a higher proportion of annuals and biennials than native flora. Our results suggest that precipitation, distance to source population, and anthropogenic disturbance influence the invasion process in this region, together with the availability of open niches. This work stresses the importance of monitoring invasive species in natural reserves, and of considering habitat types as well as idiosyncratic characteristics of the non-natives for developing management strategies.     

Temporal and spatial patterns of tenebrionid beetle diversity in NW Patagonia, Argentina

Spatial and temporal variation in abundance, richness and composition of Tenebrionidae beetle assemblages were described for north-western Patagonia. Beetles were collected using 450 pitfall traps arranged in 50 plots across an area of about 22,500 km² representative of the Subantarctic-Patagonian transition of Argentina. The study area included three different habitats: forest, scrub, and steppe. Beetles were trapped at five, eight day sampling periods in spring-summer between November 2004 and March 2006. A total of 30 species and 938 individuals were collected. Total abundance was higher in November and January than in March, and species richness did not change among samplings. Species richness was greater in the steppe than scrub. Assemblages differed between the northern and southern transects. There was little correlation between the measured environmental variables and species composition. Historical factors might explain the observed patterns, but other environmental variables such as soil characteristics may be more informative in explaining the present distribution of tenebrionid species.     

Waste Mica as Alternative Source of Plant-Available Potassium: Evaluation of Agronomic Potential Through Chemical and Biological Methods

The potassium supplying capacity of the waste mica powder (WMP) was evaluated through chemical and biological means. Four different size fractions of the WMP were studied in laboratory by different chemical extractants. At the same time, experiment of the plant growth was conducted in pot using K-deficient soil. The K release from the WMP by different extractants followed an increasing trend with an increase in the fineness of the particles. The highest K release was recorded by boiling 1 M HNO₃ (376.4–1726.4 mg kg^?1) followed by 1 M ammonium acetate (33.5–226.5 mg kg^?1), 0.01 M citric acid (31.6–158.3 mg kg^?1) and water (12.0–112.0 mg kg^?1) irrespective of the various size fractions. Significantly, higher cumulative K release from the WMP in successive extraction was recorded with 1 M boiling HNO₃ that predicts its slow-release property. The K release by different extractants was correlated significantly and positively with the biomass yield and K uptake by plants. 1 M boiling HNO₃ extractable K showed higher correlation values with the biomass yield and K uptake. Therefore, it suggests that the extractant might be a better indicator of K supplying capacity of the WMP. The plant intervention was able to extract 32.8% of total K from the WMP simultaneously improving the exchangeable and non-exchangeable K pool in soil. These above-mentioned results conclude that plants can get access to a significant amount of K from the WMP and it could be an effective source of K in highly weathered tropical soils under K deficiency.

     

Diatom-based reconstruction of Holocene hydrological changes along the Colorado River floodplain (northern Patagonia,Argentina)

Diatom assemblages recovered from a Colorado River delta core in northern Patagonia, Argentina were analyzed in order to assess past environmental conditions. A total of 35 samples were selected from a 172-cm core extracted 37 km from the mouth (39°36′19.6″S; 62°29′26.1″W). One-hundred and thirty-eight taxa were recognized and grouped according to life forms. Two diatom zones were identified by cluster analysis. At the base of the sequence, the Diatom Zone I (DZI; 4132 ± 35 ??2919?±?27 ¹⁴C yr BP), consisted of clays, and was characterized by assemblages dominated by aerophilous and benthic taxa and chrysophyte stomatocysts, which led to inferences of a sedimentary environment corresponding to a pond experiencing dry periods. The upper section (DZII) was dominated by fine sands and silts encompassing the last ~?150 yr with abundant planktonic and tychoplanktonic diatoms. Benthic diatoms were abruptly replaced by planktonic forms in this zone indicating a shift to deeper waters. These results characterize the meandering dynamics of a deltaic system. During the Mid-Holocene, more arid periods would have favored the deactivation of meanders and the formation of riverine and oxbow wetlands. In Late-Holocene and historical times, more humid conditions and the hydrological system across the floodplain reactivated the paleochannel. Today, the dominant diatom species are brackish/freshwater fragilaroids. A non-multidimensional scaling analysis showed a lack of analogy between fossil and modern samples. The change in diatom floras in recent historical times was attributed to anthropogenic disturbances, a consequence of the regulation of the river flow. This regulation is evidenced by less discharge, morphological modifications in the floodplain and increased salinity in the last decade.     

Landsat,aerial photography and state factors in soil survey of arid and humid Patagonia,Argentina

Frederiksen, Peter: LANDSAT, aerial photography and state factors in soil survey of arid and humid Patagonia, Argentina. Geografisk Tidsskrift 81: 39–48. Copenhagen, June, 1981

The applicability of LANDSAT, aerial photography, and topographical maps was tested in relation to soil survey of humid and arid Patagonia, Argentina. Fieldwork was carried out as toposequence-studies in five vegetation zones and observations of roadcuts. These data were compared with LANDSAT and aerial photography. Only observations on state factors of soil formation were obtained. These showed as a first rough approximation a consistent relationship between observed state factors as expressed in land systems and stage of soil development.     

钾肥需求模拟研究

旨在模拟预测中国钾肥需求,为钾肥市场参与者和决策者提供基本的数据和理论支持。运用主成份分析法和多元回归计量经济模型模拟我国钾肥需求。首先,运用主成份分析法对钾肥需求影响因子进行降维处理;其次,采用多元统计非线性回归计量经济学模型模拟钾肥需求。结果表明:(1)钾肥需求与人均耕地、受灾面积、钾肥价格呈负相关关系;(2)钾肥需求与耕地、粮食用地、农产品价格存正相关关系;(3)钾肥需求预测可由较易得的人均耕地、耕地、粮食用地、受灾面积、农产品价格和钾肥价格数据代入模型模拟获得,且模拟数据与现实数据吻合较好;(4)此方法可较广泛运用,不需大量的野外试验和较大的工作量,且无空间跨度差异;(5)政府行为对钾肥需求有着极大的影响作用,政府应发挥其积极性,制定出一套有序的制度安排,以弥补市场本身潜在的问题,引导市场机制不断完善。     

Climatically induced lake level changes during the last two millennia as reflected in sediments of Laguna Potrok Aike,southern Patagonia (Santa Cruz,Argentina)

The volcanogenic lake Laguna Potrok Aike, Santa Cruz, Argentina, reveals an unprecedented continuous high resolution climatic record for the steppe regions of southern Patagonia. With the applied multi-proxy approach rapid climatic changes before the turn of the first millennium were detected followed by medieval droughts which are intersected by moist and/or cold periods of varying durations and intensities. The total inorganic carbon content was identified as a sensitive lake level indicator. This proxy suggests that during the late Middle Ages (ca. AD 1230–1410) the lake level was rather low representing a signal of the Medieval Climate Anomaly in southeastern Patagonia. At the beginning of the Little Ice Age the lake level rose considerably staying on a high level during the whole period. Subsequently, the lake level lowered again in the course of the 20th century.     

Effects of soil degradation on infiltration rates in grazed semiarid rangelands of northeastern Patagonia, Argentina

In grazed semiarid ecosystems, considerable spatial variability in soil infiltration exists as a result of vegetation and soil patchiness. Despite widespread recognition that important interactions and feedbacks occur between vegetation, runoff and erosion, currently there is only limited quantitative information on the control mechanisms that lead to differences in infiltration from different vegetation types. In this paper, we determine (i) the relationship between vegetation and soil surface characteristics and (ii) the soil infiltration rate by using rainfall simulations on runoff plots (0.60 × 1.67 m) in three plant communities of northeastern Patagonia: grass (GS), degraded grass with scattered shrubs (DGS), and degraded shrub steppes (DSS). Our results clearly indicate that vegetation and soil infiltration are closely coupled. Total infiltration was significantly higher in the GS (69.6 mm) compared with the DGS and DSS (42.9 and 28.5 mm, respectively). In the GS, soil infiltration rate declined more slowly than the others communities, reaching a terminal infiltration rate significantly greater (57.7 mm) than those of DGS and DSS (25.7 and 12.9 mm, respectively). The high rate of water losses via overland-flow may limit the possibilities for grass seedling emergence and establishment and favor the persistent dominance of shrubs.     

Selective erosion of clay,organic carbon and total nitrogen in grazed semiarid rangelands of northeastern Patagonia,Argentina

In arid and semiarid rangelands, soil erosion has been widely considered an important soil degradation process and one of the main factors responsible for declining soil fertility. In this study, we determined the sediment production and the enrichment ratios of clay, organic C, and total N by using rainfall simulations on runoff plots (0.60 × 1.67 m) in three plant communities of northeastern Patagonia: grass (GS), degraded grass with scattered shrubs (DGS), and degraded shrub steppes (DSS). Our results clearly indicate that spatial variability in soil loss rate and enrichment process exists as a result of the local differences in both plant composition and soil surface characteristics. Sediment production was significantly lower in the GS (14.2 g m⁻²) compared with the DGS and DSS (38.2 and 51.5 g m⁻², respectively). In the GS, the enrichment ratio of clay was significantly greater (3.9) and enrichment ratio of organic C was lower (3.1) than in the DGS and the DSS, though differences in enrichment ratios of total N were not significant. The high rate of soil loss and nutrients through overland-flow may limit the opportunities that promote the pathway from DGS back to GS community, favoring the dominance of shrubs.     

Responses of testate amoebae assemblages (Amoebozoa: Arcellinida) to recent volcanic eruptions,inferred from the sediment record in Laguna Verde,southern Patagonia,Argentina

Journal of Paleolimnology - There is little knowledge about testate amoebae in lakes and their responses to volcanic eruptions. To address this knowledge gap, we studied the paleoecology of these...     

Reconstructing recent environmental changes using non-biting midges (Diptera: Chironomidae) in two high mountain lakes from northern Patagonia,Argentina

Remote lakes of northern Patagonia are ideal sites for examining climate- and non-climate-driven changes in aquatic ecosystems because there is little evidence of human influence and there is no detailed information on recent environmental trends in the region (i.e. the last 200 years). Subfossil chironomids (Diptera: Chironomidae) are useful paleoindicators due to their specific response to numerous environmental factors. Here, we analyze the chironomid subfossil assemblages from two remote lakes located in different environmental settings in Nahuel Huapi National Park of northern Patagonia, Argentina. Chironomids combined with sedimentary pigments (chlorophyll derivatives and total carotenoids) and organic matter provided information on the environmental history of the lakes for the last ca. 200 years. The ²¹⁰Pb chronology and tephra layers are used to establish the chronology of changes in the chironomid assemblages associated to different environmental factors that impacted the area during the period covered by the study. The deposition of volcanic ash affected the abundance and composition of chironomid assemblage throughout the record of both lakes. However, changing climate conditions and human activities are also responsible for chironomid changes in the last 50 years.     

A Miocene algal assemblage dominated by Pediastrum leonensis n. sp. (Chlorophyceae) from Patagonia, Argentina: paleoenvironmental implications

Taxonomic identification of Pediastrum species in an Early Miocene assemblage from southeast Patagonia, Argentina, is used to assess paleoecological conditions. Pediastrum leonensis n. sp. is described based on unique features of the coenobia morphology. It belongs to the P. kawraiskyi–mustersii–patagonicum complex and has no known living counterpart. This group seems to have a long evolutionary history in the region. P. kawraiskyi and P. mustersii are recorded for the first time in pre-Quaternary deposits and their presence suggests a depositional environment represented by a cold stenothermal lake conditions, indicating a temperate to a cold-temperate climate.     

Comparison of traditional wild plant knowledge between aboriginal communities inhabiting arid and forest environments in Patagonia, Argentina

The Mapuche people have a deeply rooted tradition of wild plant use for their subsistence. In this study we evaluated whether plant selection by the Mapuche is influenced by environmental constraints. Selection patterns of wild plant richness were compared in two Mapuche communities sharing the same traditions and beliefs but inhabiting different environments. Similarities and differences in the use patterns of wild medicinal and edible plants were quantitatively analyzed by using concepts derived from ecological theory. The Cayulef community is settled in the NW Patagonian (herbaceous) steppe while the Curruhuinca community is established near the Andean temperate forest, 100 km away from each other. Free-listing and semi-structured interviews were conducted with 32 families in Cayulef and 39 in Curruhuinca corresponding to 80% and 40% of each population, respectively. Data were analyzed by means of the Jaccard similarity index and statistical tests. The main results of this study showed that the home environment is a determinant factor that influences which plant species are utilized, as is the anthropic environment (with its high exotic species richness) in each community. However, similar patterns were found with respect to plant families, ways of utilization, plant parts and life forms utilized irrespective of where the communities are settled. In addition, in both populations, wild plant richness was significantly higher for medicinal than for edible species. Our results showed that the use of wild plants is primarily based on the utilization of species belonging to the nearest ecological environments that have both therapeutic and dietary functions.     

Differences in production and mortality of reproductive structures in two Prosopis L. (Mimosaceae) shrub species from Patagonia, Argentina

Prosopis L. pods have been proposed as a source of gum (galactomannans), with potential applications as a thickening agent in the food industry. The objective of this work was to compare, under field conditions, the production and mortality of reproductive structures in two sympatric shrub species of Prosopis: P. alpataco Phillipi and P. denudans Bentham. Our results indicate that fruit production in Prosopis denudans and P. alpataco is very low and erratic in non-irrigated lands. Although large quantities of flowers (15,000–25,000 flowers*0.40 m⁻²) can be found in one flowering season, 70–80% are shed before they reach anthesis and 20–28% are aborted between anthesis and fruit set. We conclude that the utilization of native populations of Prosopis denudans and P. alpataco for fruit production in Patagonian steppe, could not guarantee a consistent supply for the food industry.     

Palaeomagnetism and K—Ar age of the Upper Ordovician Alcaparrosa Formation, Argentina

Summary. Palaeomagnetic data from 71 hand samples of igneous rocks of Late Ordovician age exposed in western Argentina (31.3°S, 69.4°W, Alcaparrosa Formation) are given. Stable remanent magnetization was isolated in the majority of samples; they yield a palaeomagnetic pole at 56°S 33°E ( N = 8, α₉₅= 16°). Whole rock K-Ar age determinations yield an age of 416 ± 10 Myr for a pillow lava of the Alcaparrosa Formation.
Palaeomagnetic data for South America, Africa, Australia, Antarctica and India suggest that Gondwana was a unit at least as far back as 1000 Myr. The palaeomagnetic data define a rapid polar migration for Gondwana in Ordovician time which is consistent with the widespread occurrences of Late Ordovician glacial deposits across this supercontinent.     

Refining stratigraphy and tectonic history using detrital zircon maximum depositional age: an example from the Cerro Fortaleza Formation,Austral Basin,southern Patagonia

The north–south trending, Late Cretaceous to modern Magallanes–Austral foreland basin of southernmost Patagonia lacks a unified, radiometric, age‐controlled stratigraphic framework. By simplifying the sedimentary fill of the basin to deep‐marine, shallow‐marine and terrestrial deposits, and combining 13 new U‐Pb detrital zircon maximum depositional ages (DZ MDAs) with published DZ MDAs and U‐Pb ash ages, we provide the first attempt at a unified, longitudinal stratigraphic framework constrained by radiometric age controls. We divide the foreland basin history into two phases, including (1) an initial Late Cretaceous shoaling upward phase and (2) a Cenozoic phase that overlies a Palaeogene unconformity. New DZ samples from the shallow‐marine La Anita Formation, the terrestrial Cerro Fortaleza Formation and several previously unrecognized Cenozoic units provide necessary radiometric age controls for the end of the Late Cretaceous foreland phase and the magnitude of the Palaeogene unconformity in the Austral sector of the basin. These samples show that the La Anita and Cerro Fortaleza Formations have Campanian DZ MDAs, and that overlying Cenozoic strata have Eocene to Miocene DZ MDAs. By filling this data gap, we are able to provide a first attempt at constructing a basinwide, age‐controlled stratigraphic framework for the Magallanes–Austral foreland basin. Results show southward progradation of shallow marine and terrestrial environments from the Santonian through the Maastrichtian, as well as a northward increase in the magnitude of the Palaeogene unconformity. Furthermore, our new age data significantly impact the chronology of fossil flora and dinosaur faunas in Patagonia.     

固体钾肥产品中钾含量的放射性测定

基于钾的天然放射性 ,用放射性方法测定固体钾肥产品中的钾含量。结果表明 ,对于均匀粉末状固体钾盐产品 ,放射性方法的测定误差在± 5 %以内 (同重量法相比)     

Holocene Vegetation History and Palaeoenvironmental Conditions on the Temperate Atlantic Coast of Argentina,as Inferred from Multi-Proxy Lacustrine Records

Holocene vegetation history and palaeoenvironmental conditions are investigated at the south coast of Buenos Aires Province, Argentina. La Olla 1 and Laguna del Sauce Grande sediment sequences are analysed for pollen, calcareous microfossil (ostracods and foraminifers) and plant macrofossil remains (mainly seeds and charophyte oospores). Supplementary information is provided by sedimentological analysis. Modern surface sample data are used to assist in the interpretation of the fossil records. La Olla 1 sequence covers the period 7890 to 7630 cal. BP. The microfauna recovered is characteristic of a shallow marginal-marine environment such as a coastal lagoon. The microfossils indicate a marine connection between 7850 and 7800 cal. BP. Plant macrofossil remains and pollen analyses indicate an extension of the water body after 7780 cal. BP. The pollen record reveals the development of a halophytic plant community in a coastal environment. The sediment record from Laguna del Sauce Grande comprises the last 3000 years. Microfossils and macrofossil remains indicate that the lake history begins with a temporary brackish-water phase. More stable conditions and higher salinity values occur between 1940 and 900 cal. BP. Periods of water level fluctuations occur after 900 cal. BP, with high water levels between 660 and 270 cal. BP. The uppermost samples of the sequence show similar conditions to present day. Pollen spectra indicate a relatively stable vegetation composition throughout the last 3000 years. Pollen assemblages reflect the present regional grassland vegetation with taxa characteristic of the surrounding dune communities.