Invasion of Celtis tala forests by Ligustrum lucidum in Argentina: impact on soil properties and the arbuscular mycorrhizal community

The arrival of invasive plants can cause drastic changes to ecosystems, such as the displacement of native plant communities and the disruption of ecological functions. <i>Ligustrum lucidum</i> is an invasive tree species that has been registered in numerous regions worldwide. We analysed the effect of the expansion of <i>L. lucidum</i> on the edaphic properties and mycorrhizal fungal communities in forests of <i>Celtis tala</i> located in central-western Argentina. Sampling sites were established along a gradient of invasion, in which we measured the forest structure and soil physical-chemical factors and identified the fungal species using morphological techniques. The analysis of the variance revealed severe changes in the tree structure and a decrease in the concentrations of organic matter and nitrogen in the invaded sites. Thirty-two Glomeromycota species were identified, belonging to 6 families. The abundance of <i>Dentiscutata cerradensis</i> decreased with the invasion, whereas <i>Funneliformis mosseae</i> and <i>Septoglomus constrictum</i> increased. The alpha diversity of the arbuscular mycorrhizal communities showed no differences between sites. The beta diversity decreased at invaded sites, indicating a tendency towards convergence and reduced variability in these communities in the presence of the exotic species.

Early Jurassic Trigoniida (Bivalvia) from Argentina

Bivalves of the Order Trigoniida were abundant and diverse in the Andean Early Jurassic shallow-marine paleoenvironments. Based on extensive collections with detailed stratigraphic information from 40 localities in central-western Argentina, we describe 20 species (4 new) belonging to 11 genera (3 new) and 5 families (Groeberellidae, Trigoniidae, Prosogyrotrigoniidae, Frenguelliellidae, and Myophorellidae). The abundant material allows the description of ontogenetic development and intraspecific variability, highlighting the likely phylogenetic significance of previously underestimated features. Within Frenguelliellidae, we show that the stratigraphic range of Frenguelliella Leanza in the region is restricted to the Sinemurian–Pliensbachian. We propose Poultoniella new genus for some late Pliensbachian–Toarcian species. Jaworskiella Leanza is limited to its type species, whereas for certain convergent forms we propose Moerickella new genus (most likely the oldest Myophorellidae). Pseudovaugonia new genus likely descended from Moerickella n. gen., rather than from the highly diverse Promyophorella Kobayashi and Tamura, and is unrelated to Vaugonia Crickmay. Frenguelliella chubutensis (Feruglio) and Promyophorella basoaltorum new species are the most frequently occurring species. Some species were probably endemic (e.g., Promyophorella? sanjuanina new species), although a few (such as Frenguelliella eopacifica new species and Poultoniella jaworskii new genus new species) had a wide paleolatitudinal range and occur throughout the Pacific coasts and terranes of the Americas, revealing a significant faunal interchange among marine basins during Hettangian–Pliensbachian times. The well-documented Argentinian Early Jurassic record shows a rapid recovery and radiation of the Trigoniida after the Triassic/Jurassic extinction. Many of the new taxa that evolved in America eventually dispersed worldwide by Toarcian and Middle Jurassic times. UUID: http://zoobank.org/82c0d95e-f147-4736-a417-ebc252911181.

Similarity assessment and adjustment of integrated temperature databases. Cuyo region, Argentina

Given the frequent spatial-temporal limitations and deficiencies of instrumental meteorological records, the use of alternative information sources, such as integrated databases, are important for analyses and studies of diverse nature. The research aim was to evaluate the accuracy of integrated databases of monthly temperature, belonging to Climate Research Unit, University of Delaware and Global Historical Climatology Network, gridded with a pixel size of 3,098.01 km2 (0.5º x 0.5º), surface area of 151,802.5 km2 and temporary length of 22 years (1993-2014), through the modified structural similarity index (mSSIM). The study area is located in central-western Argentina (between 30º and 35º S, and 71º and 66º W). The University of Delaware grid showed the best fit of the data series from 10 weather stations located in the study area. Therefore, a proposal was presented to increase similarity indices, especially for those cells without instrumental reference information. The study determined that by applying this modification, the gridded datasets increases the similarity of the measured data, especially in mountainous areas, where originally there were differences of more than 7.5 ºC between the gridded data and observed one. The proposal decreases these differences to average values below 1 ºC. The use and subsequent adjustment of these integrated databases, allows access to information in areas without meteorological records.

A Decade of Hydrological Drought in Central-Western Argentina

Most of the water used for the development of the main socio-economic activities in Central-Western Argentina (CWA), an arid to semi-arid region, home to most of the Argentinean wine production, relies on surface streamflow from several snow-fed rivers. During the last decade (2010-2020), reduced snow accumulation over the higher elevations of the Andes mountains triggered the occurrence of hydrological drought over CWA, affecting winter tourism, restricting water use for irrigation and domestic use, and leading to socio-political disputes. This study provides a detailed description of the recent hydrological drought conditions through the use of streamflow records from 15 river basins, which were complemented by precipitation, snowpack, and water equivalent thickness measurements to provide a comprehensive picture of the water losses over the last decade. Hydrological drought indices derived from the threshold level method and the standardized streamflow index allowed characterizing the unusualness of this dry period in the context of the last 49 years. The hydrological deficit over the last decade highlighted the challenges faced by the water managers to provide water for irrigation in the main agricultural oases, with a likely overexploitation of the groundwater resources to supplement the limited surface runoff. The hydrological drought severity increased since 2017, with record-breaking levels in several basins, particularly during the period between July 2019 and June 2020 for the rivers located between 35° and 36°S. We identified the main hydrological drought impacts in CWA, as well as the need for improved mitigation strategies to cope with current and future drought conditions. We also analyzed the current limitations in terms of snow and groundwater observations, highlighting the necessity for an effective hydrological drought monitoring system, together with an improved forecast of snow accumulation in the headwaters, which can contribute to better regional water management plans.

Water Resources Change in Central-Western Argentina Under the Paris Agreement Warming Targets

This study documents the projected changes in several components (precipitation, runoff, snow cover and depth, soil moisture) of the hydrological cycle in Central-Western Argentina (CWA) based on the simulations from the IPSL-CM6A-LR model for the warming levels proposed in the Paris Agreement. These warming levels represent the future increase in mean annual temperature of 1.5 and 2°C compared to pre-industrial conditions. A novel regional approach, that uses a set of low-emissions shared socioeconomic pathways (SSP) compatible with the Paris Agreement goals, has been applied here for the evaluation of the potential impacts of temperature increase in both the mountainous areas of the Andes and the lowlands on the eastern portion of CWA. Our results show that the timing of reaching the 1.5°C warming level would be between 2032 and 2036 in the CWA lowlands east of the Andes, while this warming level in the Andes mountains of CWA would be 10–15 years earlier as result of the stronger warming with elevation. The higher 2°C warming level would be reached before 2050 in the Andes mountains. Even using the more aggressive mitigation pathways available in the scientific literature (SSP1-1.9 and SSP1-2.6), the IPSL-CM6A-LR model ensemble shows a robust drying signal in the wintertime precipitation over the Andes mountains, which is a concerning result because it implies a reduction of the already scarce water resources draining to the adjacent semi-arid foothills. Our results also show that this drying should be linked to the poleward expansion of the Hadley Circulation. In the lowlands farther east from the Andes, the summertime monsoonal precipitation provides the water resources that are projected to increase under the selected emissions pathways. The expected changes in the analyzed components of the hydrological cycle would be strengthened under the 2°C warming level, particularly the decline of snow amount and surface runoff in the Andes. The results of this study provide insights into the expected impacts of the 1.5 and 2°C warming levels in the CWA regional water resources, which may set the stage for the new discussions of possible options to mitigate them at country and regional levels.

Proposed chronostratigraphic units for the Carboniferous and Early Permian of the southwestern Gondwana margin

The western Andean belt of Argentina displays a comprehensive record of the Carboniferous and earliest Permian rocks so extensive that it allows an exceptional reconstruction of the Late Palaeozoic Ice Age of the southwestern margin of the South American Gondwana area. Severe endemism of the Gondwana biota during this period makes it difficult to achieve a precise correlation of these glacially influenced deposits with the coeval sequences of the Palaeoequatorial belt, where the subdivisions of the International Chronostratigraphic Chart are currently defined. The abundant paleontological record available from the Upper Palaeozoic deposits of central-western Argentina, central Patagonia, and eastern Argentina, makes it possible to recognize five successive faunal stages that allow a proper ordering of the sequences of this period. The proposed regional stages, and their assumed chronologic position regarding the standards of the current International Chronostratigraphic Chart, are: the Malimanian (late Tournaisian), Barrealian (Mid-Carboniferous or Serpukhovian-Bashkirian), Aguanegrian (Upper Pennsylvanian), Uspallatian (Asselian-Tastubian?) and Bonetian (Sakmarian). This paper aims to reiterate former recommendations about the convenience of having regional reference units and suggests the consideration of the available faunal stages as possible chronostratigraphic subdivisions for the Carboniferous-early Permian of the south-eastern margin of Gondwana.

Lead Isotopic Constraints on the Provenance of Antarctic Dust and Relevant Atmospheric Circulation Patterns Prior to the Mid-Brunhes Event (~430 Kyr Ago)

A lead (Pb) isotopic record, covering the two oldest glacial-interglacial cycles (~572 to 801 kyr ago), from the European Project for Ice Coring in Antarctica Dome C ice core provides isotopic evidence for the provenance of dust in deep Antarctic ice prior to the Mid-Brunhes Event (MBE), ~430 kyr ago, characterized by less warm interglacials. The isotopic signatures suggest Patagonia and central-western Argentina (CWA) as the primary sources of dust in central East Antarctica during both pre-MBE glacials and interglacials, in concert with an equatorward shift of the southern westerly winds (SWW). The contribution from extra-Antarctic volcanic emissions appears to be important for non-dust Pb in the pre-MBE interglacial and intermediate climates, most likely due to the reduction of wet removal efficiency with a weakening of the hydrologic cycle. Our results show a close coupling of the Southern Hemisphere atmospheric circulation patterns to climatic conditions prior to the MBE.