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In the last decades many seabirds populations had suffered decreasing in their numbers, sometimes unnoticed. Monitoring activities are a key factor in order to achieve a proper management adapted to the reality of the ecosystem. In our study we analyses the imagery data collected through unmanned aerial vehicles (UAV) in order to count the individuals of a frigate bird Fregata magnificens colony in Manglares del Morro wilderness refugee (Ecuador). Nonetheless, the actual total number of individuals is unknown. Due to this scenario, an unmanned aerial vehicle model X8+ has been used to capture images above the colony, to make a partial geolocalized mosaic of the island through the processing of the data obtained in the flight, that will allow, by means of computer vision algorithms to estimate the population of the species.

Temporal stability of the relationship between a potential proxy climate record and the climate record itself is the foundation of palaeoproxy reconstructions of past climate variability. Dendroclimatologists have spent considerable effort exploring the issue of temporal instability of temperature records at high-latitude and −altitude Northern Hemisphere sites. Much of this work has focused on the Divergence Problem in which the modern ends of tree-ring chronologies exhibit pronounced departures from the climate-proxy relationships of preceding decades. However, there has been little scrutiny of how different methods might influence determinations of temporal instability at either the local scale or across broader spatial domains. Here we use four sets of Southern Hemisphere (SH) chronologies and three sets of synthetic data with known interventions to compare four methodologies that have been widely used to assess the temporal stability of relationships between tree-ring series and climate. Our analyses demonstrate that a determination of temporal instability may be partially dependent on method used to examine data, that some methods are more sensitive to standardisation choice than others, and that all methods are better at detecting high- rather than low-frequency instability. In all cases, the relatively modest strength of the relationships between the selected SH ring-width chronologies and temperature is likely to be an issue, especially if changes in trends are of interest. We recommend that robust assessment of temporal instability between tree-ring chronologies and observational climate data should use a range of methods and that unstable temporal relationships across space be carefully considered in the context of large climate field reconstructions. Fil: Allen, K. J.. University of Melbourne; Australia Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Lavergne, A.. Imperial College London; Reino Unido Fil: Palmer, J. G.. University of New South Wales; Australia Fil: Cook, E. C.. Lamont-Doherty Earth Observatory; Estados Unidos Fil: Fenwick, P.. Gondwana Tree-Ring Laboratory; Nueva Zelanda Fil: Drew, D. M.. Stellenbosch University; Sudáfrica Fil: Turney, C. S. M.. University of New South Wales; Australia Fil: Baker, P. J.. University of Melbourne; Australia

Under the current global warming trend, droughts are expected to increase, with serious implications for water resources management. This study analyzed the regional aspects of droughts in terms of streamflow deficiencies over the Andean rivers of Patagonia, Argentina. Based on the variable threshold level method, the main characteristics of streamflow droughts were obtained for the hydrological years 1962/63-2014/15, considering three different severity levels over 11 representative basins. Two distinct regional behaviors were identified in terms of temporal variations of streamflow drought duration and its cumulative deficit volume, dividing the study area into North and Central Patagonia. The effects of the Southern Annular Mode (SAM), the El Niño-Southern Oscillation (ENSO), and the Pacific Decadal Oscillation (PDO) on the interannual and interdecadal variability of streamflow droughts were assessed through an empirical decomposition applied to the regional time series. These large-scale climatic oscillations have a distinct regional and temporal behavior in terms of the modulation of streamflow drought variability. Considering the interannual streamflow drought variability, the El Niño signal is more consistent and contributes with humid conditions, especially over North Patagonia. The multi-decadal component of the streamflow drought time series is linked to the upward trend in SAM, particularly over Central Patagonia. Fil: Rivera, Juan Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Araneo, Diego Christian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Penalba, Olga Clorinda. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina

The Southern Annular Mode (SAM) is the leading mode of atmospheric interannual variability in the Southern Hemisphere (SH) extra-tropics. Here, we assess the stationarity of SAM spatial correlations with instrumental and paleoclimate proxy data for the past millennium. The instrumental period shows that temporal non-stationarities in SAM teleconnections are not consistent across the SH land areas. This suggests that the influence of the SAM index is modulated by regional effects. However, within key-regions with good proxy data coverage (South America, Tasmania, New Zealand), teleconnections are mostly stationary over the instrumental period. Using different stationarity criteria for proxy record selection, we provide new austral summer and annual mean SAM index reconstructions over the last millennium. Our summer SAM reconstructions are very robust to changes in proxy record selection and the selection of the calibration period, particularly on the multi-decadal timescale. In contrast, the weaker performance and lower agreement in the annual mean SAM reconstructions point towards changing teleconnection patterns that may be particularly important outside the summer months. Our results clearly portend that the temporal stationarity of the proxy-climate relationships should be taken into account in the design of comprehensive regional and hemispherical climate reconstructions. The summer SAM reconstructions show no significant relationship to solar, greenhouse gas and volcanic forcing, with the exception of an extremely strong negative anomaly following the AD 1257 Samalas eruption. Furthermore, reconstructed pre-industrial summer SAM trends are very similar to trends obtained by model control simulations. We find that recent trends in the summer SAM lie outside the 5–95% range of pre-industrial natural variability. Fil: Dätwyler, Christoph. University of Bern. Centre for Climate Change Research. Institute of Geography and Oeschger ; Suiza Fil: Neukom, Raphael. University of Bern. Centre for Climate Change Research. Institute of Geography and Oeschger ; Suiza Fil: Abram, Nerilie J.. Australian National University; Australia Fil: Gallant, Ailie J. E.. Monash University; Australia Fil: Grosjean, Martin. University of Bern. Centre for Climate Change Research. Institute of Geography and Oeschger ; Suiza Fil: Jacques-Coper, Martín. Universidad de Concepción; Chile Fil: Karoly, David J.. University of Melbourne; Australia Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina

The South American Dendroecological Fieldweek (SADEF) associated with the Third American Dendrochronology Conference was held in El Bolsón, Argentina, in March 2016. The main objective of the SADEF was to teach the basics of dendrochronology while applying specific knowledge to selected research questions. The course included participants and instructors from six different countries. This report describes activities of the course and briefly summarizes exploratory group projects. The Introductory Group developed an Austrocedrus chilensis chronology from 1629-2015 and documented a persistent decline in growth since 1977 which supports the fact that the current severe drought is the most severe in the 386-year record. Based on regional A. chilensis chronologies from 32° to 39°S Latitude, the Stream Flow Reconstruction Group developed a regional 525 year-long reconstruction from Río Chubut and found the most severe drought episodes from 1490 to the present occurred from 1680-1705, 1813-1828, 1900-1920, 1993-2002, and from 2011 to the present. The Drought Reconstruction Group used A. chilensis annual tree-ring width chronologies to develop preliminary spatial field reconstructions of the Palmer Drought Severity Index spanning the Central Andes region. The reconstructions explain up to 81% of the 1907-1975 PDSI variance, indicating this tree species is powerful for informing on historical drought especially in very arid domains. The Dendroecology Group documented three spreading fires since the 1850s with a 12-year return interval but lack of fire for the last 94 years; they also documented a persistent decline in their chronologies in recent years, dating back to 1965. Fil: Amoroso, Mariano Martin. Universidad Nacional de Río Negro. Sede Andina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Speer, James H.. Indiana State University; Estados Unidos Fil: Daniels, Lori D.. University of British Columbia; Canadá Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Cook, Edward. Lamont-Doherty Earth Observatory. Tree-Ring Laboratory; Estados Unidos Fil: Stahle, David. University Of Arkansas; Estados Unidos Fil: Srur, Ana Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Tardif, Jacques. University of Winnipeg; Canadá Fil: Conciatori, France. University of Winnipeg; Canadá Fil: Aciar, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Arco Molina, Julieta Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Bonada, Anabela Carmen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Coulthard, Bethany. Lamont-Doherty Earth Observatory. Tree-Ring Laboratory; Estados Unidos Fil: Haney, Jennifer. State University of Pennsylvania; Estados Unidos Fil: Isaac-Renton, Miriam. University of Alberta; Canadá Fil: Magalhães, Juliana. University of British Columbia; Canadá Fil: Marcotti, Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Meglioli, Pablo Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Montepeluso, María Sol. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Oelkers, Rose. Lamont-Doherty Earth Observatory. Tree-Ring Laboratory; Estados Unidos Fil: Pearl, Jessie. University of Arizona; Estados Unidos Fil: Garcia, Marin Pompa. Universidad Juárez del Estado de Durango; México Fil: Robson, Johanna. University Of Winnipeg; Canadá Fil: Rodriguez Catón, Milagros Rocío. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Soto, Pamela. Universidad de Magallanes; Chile Fil: Young, Amanda. State University of Pennsylvania; Estados Unidos

Estimating summer temperature fluctuations over long timescales in southern South America is essential for better understanding the past climate variations in the Southern Hemisphere. Here we developed robust 212 year long basal area increment (BAI) and δ13C chronologies from living temperature-sensitive Fitzroya cupressoides on the eastern slope of the northern Patagonian Andes (41°S). After removing the increasing trend from the growth records likely due to the CO2 fertilization effect, we tested the potential to reconstruct past summer temperature variations using BAI and δ13C as predictors. The reconstruction based on δ13C records has the strongest predictive skills and explains as much as 62% of the total variance in instrumental summer temperature (n = 81, p

Over the last decades, gradual changes in summer climate in the Southern Hemisphere have affected forest growth in contrasting ways in moist and dry regions. Here, we use correlation analysis and a forward process-based model (Vaganov-Shashkin-Lite) to investigate changes in climate limitation of the interannual tree-ring growth of Nothofagus pumilio at the upper treeline along a precipitation gradient in northern Patagonia. Patterns of climate limitation vary consistently along the gradient. At mesic and humid treelines, tree-ring growth is positively related to growing season temperature and negatively to precipitation. At xeric treelines, the opposite is observed. Moreover, the climate-growth relations are not stationary. In particular, according to the model, the step decrease in precipitation in 1952 induced an increase of the moisture limitation at the dry edge of the gradient. Correlation analyses evidence that the dependence of growth on moisture after 1952 has enhanced since 1976. While the model consistently reproduces tree-ring width variations over the 1931-1975 period, it does not capture the growth patterns in the following years. Some environmental parameters (cloudiness, snowpack, atmospheric CO2) affecting moisture, radiation and stomatal aperture may have reached thresholds beyond which the effect on tree-growth has become sizable. Fil: Lavergne, Aliénor. Centre National de la Recherche Scientifique; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Daux, V.. Centre National de la Recherche Scientifique; Francia Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Barichivich, J.. Centre National de la Recherche Scientifique; Francia. University of Leeds; Francia

Lopez, L., Villalba, R. 2015. Forest management criteria for 12 species of Tropical Native Forests of Bolivia based on dendrochronological methods. Ecosistemas 24(2): 24-29. Doi.: 10.7818/ECOS.2015.24-2.04. In this study, we present information on growth rates, Biological Cutting Cycles (BCC), Optimum Cutting Diameters (OCD) and Optimum Cutting Periods (OCP) for 12 forest species from the Cerrado Boliviano. The results of this study were compared with those from the management guidelines established by the Bolivia's Forestry Law and from the GOL (Growth Oriented Logging) practices. Most species require more than 100 years to reach the BCC. There are species like Anadenanthera colubrina that achieves the OCD at 34 cm diameter whereas others such as Hymenaea courbaril reaches the OCD at 72 cm in diameter. The fast-growing species reach OCP at ages above 62 years, whereas slow-growing species need over 95 years. Most species require more years to reach a certain diameter than those established by the Bolivian Forestry Law. These results emphasize the need to adapt the Bolivia forest management guidelines to practices based on the actual growth rates in tropical species in the Cerrado Boliviano.

Understanding forest responses to climate variations is urgently needed for anticipating changes in forest composition and biodiversity. We use twelve tree-ring chronologies from Nothofagus dombeyi, the dominant tree at mesic-to-humid sites, to characterize climate–growth relationships along the west-to-east precipitation gradient in Nahuel Huapi National Park, Argentina. A principal components analysis indicates that a large proportion of common variance in tree growth reflects regional-scale influences of climate. Correlation functions between climate and tree-ring indexes show that the critical factor regulating tree growth is spring–summer water deficit induced by above-average temperature and reduced precipitation during the growing season. At high elevations, however, tree growth appears to be less sensitive to water deficit but comparatively more sensitive to warmer conditions. Temporal trends in climate–tree growth relationships supported the occurrence of a dominant large-scale climatic response, but also identify changes in climate–growth relationships over time, primarily at wet and high-elevation sites. These variations in climate–growth relationships are interpreted as a convergence process to similar patterns in tree growth across the entire precipitation gradient, as wet–cool conditions at high-elevation sites turned to be less frequent due to drier and warmer years during the late twentieth century. Sampling along environmental gradients provides a comprehensive view of the potential range of responses of tree growth to climate which is not recorded using traditional dendrochronological sampling at marginal, more climate-sensitive sites. The recent changes in the relationships between climate and growth highlight the vulnerability of N. dombeyi to climate changes across its entire range of distribution in Argentina. Fil: Suarez, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Mundo, Ignacio Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina Fil: Schroeder, Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mendoza. Instituto Argentino de Investigaciones de Zonas Aridas; Argentina

Size fluctuations in endorheic lakes in northwestern Argentina (NWA) and southwestern Bolivia (SWB) are very sensitive to basin hydrological balances, and consequently, very vulnerable to deleterious effects from climatic changes. The management of these water resources and their biodiversity requires a comprehensive knowledge of their natural variability over multiple timescales. In this study, we present a multi-century reconstruction of past lake-area fluctuations in NWA and SWB. The evidence used to develop and validate this reconstruction includes satellite images and a century-long tree-ring record from P. tarapacana. Inter-annual fluctuations in lake area of nine lakes were quantified based on Landsat satellite images over the period 1975 to 2009. A regional P. tarapacana tree-ring chronology, composite from two sampling sites, was used as predictors in a regression model to reconstruct the mean annual (January-December) lake area from the nine lakes. The reconstruction model captures 62 % of the total variance in lake-area fluctuations and shows adequate levels of cross-validation. This high-resolution reconstruction covers the past 601 years and characterizes the occurrence of annual to multi-decadal lake area fluctuations and its main oscillation modes of variability. Our reconstruction points out that the late 20th century decrease in lake area was exceptional over the period 1407-2007; a persistent negative trend in lake area is clear in the reconstruction and consistent with glacier retreat and other climate proxies from the Altiplano and the tropical Andes. Since the mid 1970s, the Vilama-Coruto lake system recorded an accelerated decrease in area consistent with an increasing recurrence of extremely small lake-area events. Throughout the 601 years, the reconstruction provides valuable information about spatial and temporal stabilities of the relationships between changes in lake area, ENSO, and PDO, highlighting the Pacific influence over most modes of lake area variability. Global and regional climate models for the Altiplano project a marked reduction in precipitation to the end of the 21st century, exacerbating presently dry conditions. These results provide a baseline for the historical range of variability in lake fluctuations and thus should be considered for the management of biodiversity and water resources in the Central Andes during the next decades. Fil: Morales, Mariano Santos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Carilla, Julieta. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Grau, Hector Ricardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina

Flash floods represent a significant natural hazard in small mountainous catchments of the Patagonian Andes and have repeatedly caused loss to life and infrastructure. At the same time, however, documentary records of past events remain fairly scarce and highly fragmentary in most cases. In this study, we therefore reconstruct the spatiotemporal patterns of past flash flood activity along the Los Cipreses torrent (Neuquén, Argentina) using dendrogeomorphic methods. Based on samples from Austrocedrus chilensis, Pseudotsuga menziesii, and Nothofagus dombeyi, we document 21 flash flood events covering the period A.D. 1890-2009 and reconstruct mean recurrence intervals of events at the level of individual trees being impacted, which varies from 4 to 93. years. Results show that trees tend to be older (younger) in sectors of the torrent with gentler (steeper) slope gradients. Potential triggers of flash floods were analyzed using daily temperature and precipitation data from a nearby weather station. Weather conditions leading to flash floods are abundant precipitations during one to three consecutive days, combined with temperatures above the rain/snow threshold (2. °C) in the whole watershed. Fil: Casteller, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Institute for Snow and Avalanche Research; Suiza Fil: Stoffel, Markus. University of Bern; Suiza. University of Geneva. Institute for Environmental Sciences; Suiza Fil: Crespo, Sebastián Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Corona, Christophe. University of Bern; Suiza Fil: Bianchi, Emilio. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentina

Fire is a major disturbance affecting forests worldwide with significant economic, social, and ecological impacts. The southernmost forests on Earth extend continuously along the Andes from mid- to subantarctic latitudes in South America. In this region, warming and drying trends since the mid-20th century have been linked to a positive trend in the Southern Annual Mode (SAM), the leading mode of extratropical climate variability in the Southern Hemisphere. Due to the scarcity of documentary fire records and the lack of tree-ring fire histories, little is known about how wildfire activity responds to shifts in the westerly circulation pattern and associated climatic variability in the Andean region south of ~44° S. For the first time, we applied dendrochronological techniques to reconstruct fire history from the angiosperm Nothofagus pumilio at 16 sites distributed from ~44° to 50° S to determine relationships between fire occurrence and the two primary drivers of wildfire activity: climate variability and human activities. Partial cross-sections with fire scars were collected from 363 trees in Argentina and Chile. Chronologies of annually resolved fire-scar dates start in 1791 and show a pattern of higher fire frequency during the 20th century, concurrent with the human occupation and colonization processes in southern Patagonia. Years of widespread fire occurring synchronously in two or more disjunct sites are associated with broad-scale climatic anomalies. Intense droughts inferred from extreme departures in temperature, precipitation, and the Standardized Precipitation-Evapotranspiration Index (SPEI) during the growing seasons of 1944 and 1962 are consistent with the two most severe fires at northern sites. Extended droughts, reflected by the association of fire occurrence with six-month cumulative precipitation and SPEI, create conditions for widespread fires at the southern sites (south of ~46° S). Regional fires were concurrent with significant positive departures of SAM during the austral spring?summer. This tree-ring fire record reveals the influences of both climate variability and human activities on fire in the N. pumilio forests across the Andes, and also establishes the feasibility of using this tree species as a natural archive of fire history. Fil: Mundo, Ignacio Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Laboratorio de Dendrocronología e Historia Ambiental; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Veblen, Thomas. State University of Colorado Boulder; Estados Unidos Fil: Kitzberger, Thomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Ecotono; Argentina Fil: Holz, Andrés. Portland State University. Department of Geography; Estados Unidos Fil: Paritsis, Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Ecotono; Argentina Fil: Ripalta, Alberto. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Laboratorio de Dendrocronología e Historia Ambiental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina

Understanding the process of primary succession is a relevant topic in restoration and global change ecology, and provides the basis for classic dating methods in geomorphology, such as lichenometry and dendrochronology. The aim of this study is to investigate the colonization by lichens and vascular plants of two pro-glacial chronosequences encompassing the late- and mid-Holocene periods in the sub-Antarctic sub-region of South America. We use this information to address questions related to the pattern of Magellanic forests recovery after disturbance and the applicability of lichenometry for developing glacier retreat chronologies. Progression of succession to a state with high vascular plant cover was slow, and some moraines remained unforested for about 2000 years. Our results contrast with previous reports indicating a quick development of mature forest states on disturbed terrains, suggesting large regional variability on the course of succession. Environmental conditions seem propitious for lichens that colonize immediately after moraine formation. Lichens grow at relatively high rates in comparison to other world areas, but half as fast as in Antarctica and sub-Antarctic islands. Growth rates for the Rhizocarpon Ram. em. Th. Fr. sub-gen. Rhizocarpon group increase with lichen sizes up to ca. 50 mm and decrease in larger thalli, leading to a sigmoidal lichenometric growth curve that extends the applicable range of lichenometry to the last 5700 years in dry sites in the Magellanic province of the sub-Antarctic sub-region. Our results suggest that lichenometry is an effective technique in multi-proxy approaches for reconstructing glacier fluctuations, and agree with early studies in Antarctica suggesting that lichen annual growth rate is a sensitive attribute for the biomonitoring of climate changes. Fil: Garibotti, Irene Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina

During the period 2010-2015, the semi-arid Central Andes in Argentina (CAA) experienced one of the most severe and long-lasting hydrological droughts on record. Since the snowmelt is the most important source of water, the reduced snowfall over the mountains propagated the drought signal through the streamflows in the adjacent foothills east of the Andes ranges. Motivated by the widespread impacts on the socio-economic activities in the region, this study aims to characterize the recent hydrological drought in terms of streamflow deficits. Based on streamflow data from 20 basins, we used the standardized streamflow index (SSI) to characterize hydrological droughts during the period 1971-2016. We found that the regional extent of the 2010-2015 hydrological drought was limited to the basins located north of 38° S, with mean duration of 67 months and maximum drought severity exhibiting a heterogeneous pattern in terms of spatial distribution and time of occurrence. The drought event reached extreme conditions in 14 of the 15 basins in the CAA, being record-breaking drought in six of the basins. This condition was likely driven by a cooling in the tropical Pacific Ocean resembling La Niña conditions, which generated a decrease in snowfall over the Andes due to suppressed frontal activity. Fil: Rivera, Juan Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad ; Argentina Fil: Penalba, Olga Clorinda. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Araneo, Diego Christian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina

Los glaciares constituyen reservas hídricas en estado sólido y son componentes cruciales del sistema hidrológico de montaña. A pesar de su importancia, no existía en Argentina información precisa sobre el número, ubicación y tamaño de estos cuerpos de hielo. En el año 2010, se sanciona la Ley 26639 de “Presupuestos Mínimos para la Preservación de los Glaciares y el Ambiente Periglacial”, que tiene como principales objetivos proteger los glaciares considerados como reservas estratégicas de recursos hídricos y crear el Inventario Nacional de Glaciares (ING), donde se individualicen todos los glaciares y geoformas periglaciales que actúan como reservas hídricas con toda la información necesaria para su adecuada protección, control y monitoreo. El inventario y monitoreo del estado de los glaciares y del ambiente periglacial es llevado a cabo por el Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA-CONICET) con la coordinación de la autoridad nacional de aplicación de la ley, el Ministerio de Ambiente y Desarrollo Sustentable de Argentina (MAyDS). Este inventario se realiza en tres niveles que varían en complejidad y extensión espacial. En este trabajo se presentan los resultados preliminares obtenidos en el primer nivel, que consiste en el mapeo y caracterización de glaciares (descubiertos, cubiertos, manchones de nieve y de escombros) mediante sensores remotos. Estos datos son luego verificados en el campo en sectores seleccionados. Sobre un total de 70 cuencas y subcuencas delimitadas para el inventario se ha avanzado en 64. Hasta febrero de 2017, se han inventariado 15,482 glaciares que cubren una superficie de 5743 km2

In the Central Andes of Argentina (30–37°S), snowmelt is the main source of freshwater, an essential natural resource for ~2.2 million people in the adjacent arid lowlands. In this region, Laguna Llancanelo collects the water inputs from the Malargüe endorheic basin. Previous studies concerning the annual and intra-annual variations of this lagoon and its relationship with regional climate are rare. We obtained a monthly record for the Laguna Llancanelo area (LLA, 1984–2013) using the modified normalized difference water index derived from Landsat images. Monthly LLA ranges between 35 km2 and 411 km2 and is significantly related to variations of the Río Malargüe, the main snow-fed tributary to the lagoon. There is no long-term relationship between LLA and local rainfall, but rapid increases in LLA result from heavy rainfall around the lagoon. Conversely, rapid reductions in LLA encompass periods with both reduced discharge from the Río Malargüe and low local rainfall. The LLA integrates moisture of both Pacific (snowfall in the upper Andes) and Atlantic (lowland rainfall) origins; therefore, we propose using LLA as an indicator of regional water balance. Fil: Bianchi, Lucas Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Rivera, Juan Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Rojas, Juan Facundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Britos Navarro, Mauro Octavio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina

Very few studies of stable isotopes exist across the Andes in South America. This study is the first presenting annually resolved chronologies of both δ18O and δ13C in Nothofagus pumilio and Fitzroya cupressoides trees from Northern Patagonia. Interannual variability in δ18O and δ13C was assessed over the period 1952–2011. Based on these chronologies, we determined the primary climatic controls on stable isotopes and tree physiological responses to changes in atmospheric CO2 concentrations (ca), temperature and humidity. Changes in specific intrinsic water use efficiency (iWUE) were inferred from variations in δ13C whereas the effects of CO2 increase on stomatal conductance were explored using δ18O. Over the 60-year period, iWUE increased significantly (by ca. 25%) in coincidence with the rise of ca. The two species appear to have different strategies of gas-exchange. Whereas iWUE variations were likely driven by both stomatal conductance and photosynthetic assimilation rates in F. cupressoides, they were largely related to stomatal conductance in N. pumilio. After removing the low-frequency trends related to increasing ca, significant relationships between δ13C and summer temperatures were recorded for both species. However, δ13C variations in F. cupressoides were more strongly influenced by summer temperatures than in N. pumilio. Our results advocate for an indirect effect of summer temperatures on stable isotope ratios, which is mostly influenced by sunlight radiation in F. cupressoides and relative humidity/soil moisture in N. pumilio. δ13C variations in F. cupressoides were spatially correlated to a large area south of 35°S in southern South America. These promising results encourage the use of δ13C variations in F. cupressoides for reconstructing past variations in temperature and large-scale circulation indexes such as the Southern Annular Mode (SAM) in the Southern Hemisphere. Fil: Lavergne, Aliénor. Centre National de la Recherche Scientifique; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Aix-Marseille Université; Francia Fil: Daux, Valérie. Centre National de la Recherche Scientifique; Francia Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Pierre, Monique. Centre National de la Recherche Scientifique; Francia Fil: Stievenard, Michel. Centre National de la Recherche Scientifique; Francia Fil: Srur, Ana Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina

Forest decline is driven by several factors interacting in complex ways, and it is often exacerbated by climate, adding complexity to the process and making it more difficult to identify the causing factors. The long-term perspective provided by tree rings has proven to be successful for disentangling the causes of forest decline worldwide. We present recent dendroecological studies developed to determine the influences of climatic variation on the radial growth patterns and death of trees in declining Austrocedrus chilensis and Nothofagus pumilio forests in northern Patagonia, Argentina. These results were used to distinguish between possible causes and interactions of abiotic and biotic stress factors versus stand dynamics processes in the development of the forest declines. For our study forests, we found complex interactions between abiotic and biotic factors acting at different spatial and temporal scales that predispose trees, then incite and contribute to the development of the symptoms leading to their subsequent death. We summarize our findings in a conceptual model presenting forest decline as a spiral of processes driven by interactions between abiotic and biotic stress factors that predispose, incite and contribute to stand-level decline in these forests. Our framework formalizes an alternate hypothesis to single causal agents of decline in Patagonian forests by emphasizing the role and importance of climatic variability as a driver of decline.

Climate-induced changes in the annual regime of snow-fed rivers have serious implications for water resource management. In the Central Andes (CA, 28°–36°S) of Argentina–Chile, the snow accumulated in high-elevation mountains in winter is the dominant component of streamflows during the spring–summer melting season. Although topography introduces complexity in snowpack responses to the annual temperature cycle, streamflow series over a century in length make the CA particularly suitable for identification of long-term hydrological changes. Principal component (PC) analysis of Rio Atuel annual hydrographs from 1906 to 2012 discriminates between precipitation- and temperature-related components associated with variations in snow accumulation (49% of variance) and advances/delays of the streamflow annual peak (21% of variance), respectively. The temporal evolution of PC1 loadings reveals a predominant negative period from 1917 to 1976 and from 1988 to present, suggesting the propensity to undergo long periods with reduced flows. In turn, the PC2 pattern is predominantly positive from 1948 to the present, revealing a tendency to more frequent peak flows in late spring since the mid-20th century. Above-average streamflows related to abundant snowfalls in the CA are associated with northward shifts in stormtracks that are remotely induced by above-average sea surface temperatures in the equatorial Pacific. On the other hand, earlier streamflow peaks in November-December are concurrent with above-average temperatures across the Atuel basin induced by enhanced meridional circulation from the Tropics due to the strengthening of the South Atlantic anticyclone. These circulation anomalies are linked to the persistent positive phase of the Southern Annular Mode during the last decades. Additionally, years with reduced streamflows in January, and proportionally larger flow contributions in November-December, are associated with anomalous air cooling at high levels induced by low pressure centres over the region as part of a quasi-zonal stationary Rossby wave train that extends from Australia to the South American–South Atlantic sector.

This paper explores variation in maize consumption among human societies in arid environments of central-western Argentina over the last 2500 years. Increasingly positive human d13C signatures suggest a high intake of C4 resources (maize) until ca. A.D. 1400. After this time, the importance of maize in the diet drops and never reaches pre-Hispanic consumption rates, despite the known importance of maize to Inka and other late-prehistoric societies in the region. This decline appears to be related to colder temperatures during the Little Ice Age from the beginning of the 15th to the mid19th centuries. Fil: Gil, Adolfo Fabian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Museo de Historia Natural de San Rafael - Ianigla | Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Museo de Historia Natural de San Rafael - Ianigla | Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Museo de Historia Natural de San Rafael - Ianigla; Argentina Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Ugan, Andrew. University of Utah; Estados Unidos. Far Western ARG; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Museo de Historia Natural de San Rafael - Ianigla | Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Museo de Historia Natural de San Rafael - Ianigla | Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Museo de Historia Natural de San Rafael - Ianigla; Argentina Fil: Cortegoso, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Filosofia y Letras; Argentina Fil: Neme, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Museo de Historia Natural de San Rafael - Ianigla | Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Museo de Historia Natural de San Rafael - Ianigla | Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Museo de Historia Natural de San Rafael - Ianigla; Argentina Fil: Michieli, Catalina Teresa. Universidad Nacional de San Juan. Facultad de Filosofía, Humanidades y Artes. Instituto de Investigaciones Arqueológicas y Museo "Mariano Gambier"; Argentina Fil: Novellino, Paula Silvana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mendoza. Museo de Ciencias Naturales y Antropológicas J.Cornelio Moyano - ; Argentina Fil: Duran, Victor Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Filosofia y Letras; Argentina

The aim of this study is to evaluate the relationships between primary and secondary growth as well as the influences of climate variations on both types of growth. The relationships between apical (or primary) and radial (or secondary) growth, and climatic influences on both types of growth, were evaluated for Nothofagus pumilio (Nothofagaceae), the dominant subalpine tree in Patagonia. We measured the spacing and number of nodes of annual shoots developed in the period 2001–2010 in 40 N. pumilio trees growing near the upper treeline in the northern Patagonian Andes (41°S). Variations in ring width at the base of each trunk were also recorded. Interannual variations in primary and secondary growth were significantly related to each other, and to several climate variables. Mean temperatures in winter and early spring (June–October) prior to the period of shoot extension were positively associated with both primary and secondary growth. In addition, total summer precipitation (December–March) was positively related to shoot extension, whereas mean summer temperature during the previous growth season (January–March) was directly related to radial growth. These climatic influences on N. pumilio growth may play a major role in regulating the expressions of preformation and neoformation.

The meteorological factors involved in the formation of earlywood frost rings in Rocky Mountain bristlecone pine (Pinus aristata) have not been described in detail. This study used 51 tree-ring dated Rocky Mountain bristlecone pine trees growing at ca. 3500 m a.s.l. on Mt. Goliath, Colorado, to develop earlywood and latewood frost ring chronologies dating from 1930 to 2010 for investigation of the regional and large-scale weather anomalies responsible for these unusual growing season freeze events. The high-elevation meteorological station at Niwot Ridge, Colorado, was used to document the daily temperature anomalies most likely associated with these frost-damaged rings. NCEP-NCAR Reanalysis data were used to examine the synoptic meteorological conditions that tend to prevail during these unusual growing season temperature conditions. Earlywood frost rings occur during anomalous late-May and June freeze events in the Colorado Rockies associated with unseasonal mid-latitude circulation, including the penetration of a deep upper-level low pressure system and cold surface air temperatures into the west-central United States. The three latewood frost rings all occurred during September freeze events also associated with unseasonal and highly amplified mid-latitude circulation. The chronology of these early and late growing season freeze events may provide a useful independent check on daily temperature minima estimated with reanalysis techniques, and they can be extended into the pre-instrumental era thanks to the great age of Rocky Mountain bristlecone pine. Frost damage in Mt. Goliath bristlecone pine appears to be most frequent and severe in young trees found in the depressed tree line below a large cirque subject to intense cold air drainage. The development of the most detailed tree-ring records of past freeze events may therefore benefit from site selection in these cold air drainages, along with age-stratified tree sampling to ensure that the young and most frost susceptible age classes are well represented throughout the chronology.

Forestry use in Prosopis flexuosa woodlands in the Central Monte is limited by low wood productivity and by most of the trees being multi-stemmed. Desert inhabitants have turned pruning into a common practice to get some forest products, increase wood production and improve tree shape. In this study we tested pruning practices used by locals on trees of different diameter classes and different pruning intensities in the aeolian plains of the Central Monte Desert. Two trials were conducted: (a) we tested the effects of pruning on three types of trees: adult multi-stemmed trees (7.5–15 cm basal diameter; n = 12 for pruned trees and 10 for control), young trees (3–7.5 cm basal diameter; n = 20 for pruned trees and 18 for control), and saplings (

Subtropical forests in montane ecosystems grow under a wide range of environmental conditions. However, little is known about the growth responses of subtropical trees to climate along ecological gradients. To assess how, and to what extent climate controls tree growth, we analyzed tree responses to climate for 15 chronologies from 4 different species (Schinopsis lorentzii, Juglans australis, Cedrela lilloi, Alnus acuminata) across a variety of environments in subtropical forests from northwestern Argentina (22-28°S, 64-66°W). Using correlation and principal component analysis, site and species differences in tree-growth responses to precipitation and temperature were determined along the elevation gradient from the dry-warm Chaco lowlands to the wet-cool montane Yungas. Our results show that species responses differ according to the severity in climate conditions along the elevation gradient. At sites with unfavorable conditions, mainly located at the extremes of the environmental gradient, responses of different species to climate variations are similar; in contrast, at sites with relatively mild conditions, tree growth displays a large variety of responses reflecting differences in both local environmental conditions and species physiology. Our research suggests that individualistic responses to environmental variability would determine differences in the type and timing of the responses of dominant trees to climate, which ultimately may shift species? assemblages in montane subtropical regions of South America under future climate changes. Fil: Ferrero, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: de Membiela, Mónica. Universidad Politecnica de Madrid; España Fil: Ripalta, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Delgado, Silvia Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Paolini, Leonardo. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Ecología Regional; Argentina

Araucaria araucana (Araucaria) is a long-lived conifer growing along a sharp west-east biophysical gradient in the Patagonian Andes. The patterns and climate drivers of Araucaria growth have typically been documented on the driest part of the gradient relying on correlations with meteorological records, but the lack of in situ soil moisture observations has precluded an assessment of the growth responses to soil moisture variability. Here, we use a network of 21 tree-ring width chronologies to investigate the spatiotemporal patterns of tree growth through the entire gradient and evaluate their linkages with regional climate and satellite-observed surface soil moisture variability.We found that temporal variations in tree growth are remarkably similar throughout the gradient and largely driven by soil moisture variability. The regional spatiotemporal pattern of tree growth was positively correlated with precipitation (r = 0.35 for January 1920-1974; P < 0.01) and predominantly negatively correlated with temperature (r =- 0.38 for January-March 1920-1974; P < 0.01) during the previous growing season. These correlations suggest a temporally lagged growth response to summer moisture that could be associated with known physiological carry-over processes in conifers and to a response to moisture variability at deeper layers of the rooting zone. Notably, satellite observations revealed a previously unobserved response of Araucaria growth to summer surface soil moisture during the current rather than the previous growing season (r = 0.65 for 1979-2000;P < 0.05). This new response has a large spatial footprint across the mid-latitudes of the South American continent (35°-45°S) and highlights the potential of Araucaria tree rings for palaeoclimatic applications.The strong moisture constraint on tree growth revealed by satellite observations suggests that projected summer drying during the coming decades may result in regional growth declines in Araucaria forests and other water-limited ecosystems in the Patagonian Andes.

Past global climate changes had strong regional expression. To elucidate their spatio-temporal pattern, we reconstructed past temperatures for seven continental-scale regions during the past one to two millennia. The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century. At multi-decadal to centennial scales, temperature variability shows distinctly different regional patterns, with more similarity within each hemisphere than between them. There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructions show generally cold conditions between AD 1580 and 1880, punctuated in some regions by warm decades during the eighteenth century. The transition to these colder conditions occurred earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere regions. Recent warming reversed the long-term cooling; during the period AD 1971?2000, the area-weighted average reconstructed temperature was higher than any other time in nearly 1,400 years. Fil: Ahmed, Moinuddin. Federal Urdu University of Arts, Science and Technology. Department of Botany; Pakistán Fil: Anchukaitis, Kevin J.. Columbia University. Lamont Doherty Earth Observatory; Estados Unidos. Woods Hole Oceanographic Institution; Estados Unidos Fil: Asrat, Asfawossen . Addis Ababa University. School of Earth Sciences; Etiopía Fil: Borgaonkar, Hemant P.. Indian Institute of Tropical Meteorology; India Fil: Braida, Martina . University of Trieste. Dipartimento di Matematica e Geoscienze; Italia Fil: Buckley, Brendan M. . Columbia University. Lamont Doherty Earth Observatory; Estados Unidos Fil: Ulf Büntgen. Swiss Federal Research Institute WSL; Suiza Fil: Chase, Brian M.. Université Montpellier. Département Paléoenvironnements et Paléoclimats (PAL); Francia. University of Bergen. Department of Archaeology, History, Cultural Studies and Religion; Noruega Fil: Christie, Duncan A. . Universidad Austral de Chile. Laboratorio de Dendrocronología y Cambio Global; Chile. Universidad de Chile. Center for Climate and Resilience Research; Chile Fil: Cook, Edward R.. Columbia University. Lamont Doherty Earth Observatory; Argentina Fil: Curran, Mark A. J.. Australian Antarctic Division; Australia. University of Tasmania. Antarctic Climate & Ecosystems Cooperative Research Centre; Australia Fil: Diaz, Henry F. . National Oceanic and Atmospheric Administration. Cooperative Institute for Research in Environmental Sciences, ; Estados Unidos Fil: Esper, Jan. Johannes Gutenberg University. Department of Geography,; Alemania Fil: Fan, Ze-Xin . Chinese Academy of Sciences. Xishuangbanna Tropical Botanical Garden ; China Fil: Gaire, Narayan P. . Nepal Academy of Science and Technology. Faculty of Science,; Nepal Fil: Ge, Quansheng. Chinese Academy of Sciences. Institute of Geographical Sciences and Natural Resources Research, ; China Fil: Gergis, Joëlle. University of Melbourne. School of Earth Sciences; Australia Fil: González-Rouco, J Fidel. Universidad Complutense de Madrid. Departamento Astrofísica y CC de la Atmósfera; España Fil: Goosse, Hugues. Université Catholique de Louvain. LemaitreCenter for Earth and Climate Research, Earth and Life Institute; Bélgica Fil: Grab, Stefan W. . University of the Witwatersrand. School of Geography,Archaeology and Environmental Studies; Sudáfrica Fil: Graham, Nicholas. Hydrologic Research Center; Estados Unidos Fil: Graham, Rochelle . Hydrologic Research Center; Estados Unidos Fil: Grosjean, Martin . University of Bern. Oeschger Centre for Climate Change Research & Institute of Geography; Suiza Fil: Hanhijärvi, Sami T.. University of Helsinki. Department of Environmental Sciences; Finlandia Fil: Kaufman, Darrell S.. Northern Arizona University. School of Earth Sciences and Environmental Sustainability; Estados Unidos Fil: Kiefer, Thorsten . International Project Office, Past Global Changes (PAGES); Suiza Fil: Kimura, Katsuhiko. Fukushima University. Department of Symbiotic System Science; Japón Fil: Korhola, Atte A.. University of Helsinki. Department of Environmental Sciences; Finlandia Fil: Krusic, Paul J.. Stockholm University. Department of Physical Geography and Quaternary Geology; Suecia Fil: Lara, Antonio. Universidad Austral de Chile. Laboratorio de Dendrocronología y Cambio Global; Chile. Universidad de Chile. Center for Climate and Resilience Research; Chile Fil: Lézine, Anne-Marie. Université Pierre et Marie Curie. Laboratoire d’Océanographie et du Climat: Expérimentations et Approches Numériques (LOCEAN); Francia Fil: Ljungqvist, Fredrik C.. Stockholm University. Department of History, ; Suecia Fil: Lorrey, Andrew M.. National Institute of Water and Atmospheric Research Ltd., National Climate Centre Auckland; Nueva Zelanda Fil: Luterbacher, Jürg. Justus Liebig University. Department of Geography, Climatology, Climate Dynamics and Climate Change; Alemania Fil: Masson-Delmotte, Valérie . Laboratoire des Science du Climat et de l’Environnement, Gif-sur-Yvette; Francia Fil: McCarroll, Danny. Swansea University. Department of Geography; Reino Unido Fil: McConnell, Joseph R.. Nevada System of Higher Education. Desert Research Institute; Estados Unidos Fil: McKay, Nicholas P.. Northern Arizona University. School of Earth Sciences and Environmental Sustainability; Estados Unidos Fil: Morales, Mariano Santos. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Moy, Andrew D.. Australian Antarctic Division; Australia. University of Tasmania. Antarctic Climate & Ecosystems Cooperative Research Centre; Australia Fil: Mulvaney, Robert. British Antarctic Survey; Reino Unido Fil: Mundo, Ignacio Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Nakatsuka, Takeshi. Nagoya University. Department of Earth and Environmental Sciences; Japón Fil: Nash, David J.. University of the Witwatersrand. School of Geography,Archaeology and Environmental Studies; Sudáfrica. University of Brighton. School of Environment and Technology; Reino Unido Fil: Neukom, Raphael . Swiss Federal Research Institute WSL; Suiza Fil: Nicholson, Sharon E.. Florida State University. Department of Earth, Ocean and Atmospheric Sciences, ; Estados Unidos Fil: Oerter, Hans. Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association. Department of Glaciology; Alemania Fil: Palmer, Jonathan G.. University of Exeter. College of Life and Environmental Sciences; Reino Unido. University of New South Wales. Climate Change Research Centre; Australia Fil: Phipps, Steven J.. University of New South Wales. Climate Change Research Centre; Australia. University of New South Wales. ARC Centre of Excellence for Climate System Science; Australia Fil: Prieto, Maria del Rosario. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Rivera, Andres. Centro de Estudios Cientificos; Chile Fil: Sano, Masaki. Nagoya University. Department of Earth and Environmental Sciences; Japón Fil: Severi, Mirko. University of Florence. Department of Chemistry ‘Ugo Schiff’; Italia Fil: Shanahan, Timothy M.. University of Texas at Austin. Jackson School of Geosciences; Estados Unidos Fil: Shao, Xuemei. Chinese Academy of Sciences. Institute of Geographical Sciences and Natural Resources Research; China Fil: Shi, Feng. Chinese Academy of Sciences. LASG, Institute of Atmospheric Physics, ; China Fil: Sigl, Michael . Nevada System of Higher Education. Desert Research Institute,; Estados Unidos Fil: Smerdon, Jason E.. Columbia University. Lamont Doherty Earth Observatory; Estados Unidos Fil: Solomina, Olga N. . Russian Academy of Sciences. Institute of Geography; Rusia Fil: Steig, Eric J.. University of Washington. Department of Earth and Space Sciences; Estados Unidos Fil: Stenni, Barbara. University of Trieste. Dipartimento di Matematica e Geoscienze; Italia Fil: Thamban, Meloth. National Centre for Antarctic and Ocean Research; India Fil: Trouet, Valerie. University of Arizona. Laboratory of Tree-Ring Research; Estados Unidos Fil: Turney, Chris S.M.. University of New South Wales. Climate Change Research Centre; Australia Fil: Umer, Mohammed. Addis Ababa University. School of Earth Sciences; Etiopía Fil: van Ommen, Tas. Australian Antarctic Division; Australia. University of Tasmania. Antarctic Climate & Ecosystems Cooperative Research Centre; Australia Fil: Verschuren, Dirk. Ghent University. Department of Biology; Bélgica Fil: Viau, Andre E.. University of Ottawa. Department of Geography; Canadá Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Vinther, Bo M.. University of Copenhagen. Niels Bohr Institute; Dinamarca Fil: von Gunten, Lucien . Past Global Changes (PAGES). International Project Office, ; Suiza Fil: Wagner, Sebastian. Helmholtz-Zentrum Geesthacht. Institute for Coastal Research; Alemania Fil: Wahl, Eugene R.. National Oceanic and Atmospheric Administration. National Climatic Data Center; Estados Unidos Fil: Wanner, Heinz. University of Bern. Oeschger Centre for Climate Change Research & Institute of Geography; Suiza Fil: Werner, Johannes P.. Justus Liebig University. Department of Geography, Climatology, Climate Dynamics and Climate Change; Alemania Fil: White, James W.C.. University of Colorado. Institute of Arctic and Alpine Research; Estados Unidos Fil: Yasue, Koh. Shinshu University. Department of Forest Science; Japón Fil: Zorita, Eduardo. Helmholtz-Zentrum Geesthacht. Institute for Coastal Research; Alemania

We present the first glacier inventory of the Monte San Lorenzo region (47º35′S, 72º18′W) in the southern Patagonian Andes of Chile and Argentina. This region contains the largest and easternmost glaciers at these latitudes in South America. The inventory was developed using a combination of ASTER and Landsat ETM + scenes from 2005 and 2008, respectively, and a semi-automatic band ratio approach to map glacier ice. Manual corrections were applied to include debris-covered ice and ice in cast shadows. We inventoried 213 glaciers that cover a 2005/2008 total area of ca. 207 km2 and lie between 520 m and 3700 m in elevation. Landsat TM images acquired in 1985 and 2000 were subsequently used to assess changes in glacierized area over the 1985–2008 interval. Based on all available information, we determined an 18.6% reduction in the total glacier area since 1985. Glaciers smaller than 1 km2 have shown highly variable (0–100%) relative areal reduction, whereas the formation and growth of proglacial lakes promoted rapid recession of the, larger valley glaciers, which concentrate the major ice losses, representing ca. 32% of the total glacier area reduction. Glacier fragmentation has occurred for 50% of the ice bodies larger than 1 km2. These results agree with the generalized pattern of glacier retreat observed throughout the Patagonian Andes, but the lack of detailed meteorological and glaciological data in the area preclude a more refined analysis of the climate-glacier relationships and processes explaining the recent glacier trends. Fil: Falaschi, Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Bravo, Claudio. Departamento de Geofísica. Universidad de Chile; Chile Fil: Masiokas, Mariano Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Rivera, Andrés. Centro de Estudios Científicos; Chile

Grazing influences the morphology and growth rate of shrubs, and consequently, their population dynamics. It has been shown that grazing directly affects the growth of shrubs. On the other hand, the reduction of grass biomass by herbivores reduces soil-water competition between grasses and shrubs, and indirectly, could enhance the growth of shrubs. However, the lack of long and homogeneous records of plant dynamics and primary production in the arid Patagonia hampers the assessment of the long-term effects of grazing on the growth of shrubs. We combined allometric and growth-ring analyses to assess the direct effect of grazing on individuals of Anarthrophyllum rigidum, a leguminous shrub widely distributed across the Patagonian steppe. The evergreen, protein-rich leaves of A. rigidum constitute an important complement for the sheep diet, particularly in winter when the abundance of grasses is reduced. Our observations indicated that individuals nearby the water source are smaller in size (35.5 cm vs. 67.39 cm), and present a larger number of basal branches (23 vs. 12), and show slower rates of growth (8.2 mm yr-1 vs. 13.3mm yr-1) than those located far from the water source. Our first quantification of the long-term effects of grazing on A. rigidum individuals suggests that beneficial effects of grazing through the reduction of grasses that compete for soil water should be more obvious for non-preferred than preferred shrubs in the dry Patagonian steppe. Fil: Srur, Ana Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Golluscio, Rodolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Producción Animal; Argentina Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Hodara, Karina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Métodos Cuantitativos y Sistemas de Información; Argentina

Climate data of mean monthly temperature and total monthly precipitation compiled from different sources in northern Patagonia were interpolated to 20-km resolution grids over the period 1997–2010. This northern Patagonian climate grid (NPCG) improves upon previous gridded products in terms of its spatial resolution and number of contributing stations, since it incorporates 218 and 114 precipitation and temperature records, respectively. A geostatistical method using surface elevation from a Digital Elevation Model (DEM) as the ancillary variable was used to interpolate station data into even spaced points. The maps provided by NPCG are consistent with the broad spatial and temporal patterns of the northern Patagonian climate, showing a comprehensive representation of the latitudinal and altitudinal gradients in temperature and precipitation, as well as their related patterns of seasonality and continentality. We compared the performance of NPCG and various other datasets available to the climate community for northern Patagonia. The grids used for the comparison included those of the Global Precipitation Climatology Project, ERAInterim, Climate Research Unit (University of East Anglia), and University of Delaware. Based on three statistics that quantitatively assess the spatial coherence of gridded data against available observations (bias, MAE, and RMSE), NPCG outperforms other global grids. NPCG represents a useful tool for understanding climate variability in northern Patagonia and a valuable input for regional models of hydrological and ecological processes. Its resolution is optimal for validating data from the general circulation models and working with raster data derived from remote sensing, such as vegetation indices. Fil: Bianchi, Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentina Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Viale, Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Couvreux, Fleur. Centre National de Recherches Météorologiques; Francia Fil: Marticorena, Rocio. Autoridad Interjurisdiccional de Cuencas; Argentina

This paper presents results from studies of exposure to climate change and extreme events in the Mendoza River Basin in western Argentina, the Chinchina River basin in the Colombian Andes, and the Oldman River basin and Swift Current Creek watershed in the Canadian Prairies. These case studies are a major component of an international research project: “Vulnerability and Adaptation to Climate Extremes in the Americas” (VACEA). This project is very much interdisciplinary; with social and natural science providing context and direction for research in the other realm of scholarship, producing insights that very likely would not arise from a more narrow disciplinary perspective. A large number of interviews with local actors revealed that agricultural producers and local officials recognize their high degree of exposure and sensitivity to climate variability and extreme weather events, although they generally do not associate this with climate change. Case studies of exposure demonstrate that the perceptions of the local actors are consistent with the nature of the regional hydroclimatic regimes. In all four river basins, climate variability between years and decades masks any regional expression of global climate change. These modes of periodic variability dominate the paleoclimate of past centuries and the recorded hydroclimate of recent decades. The exposure variables examined in this paper, indices of stream flow, snowpack, water excess and deficit, vary in coherence with the characteristic frequencies of large-scale ocean–atmosphere circulation patterns, specifically the ENSO and PDO. Projections of the future states of these variables require the use of climate models that are able to simulate the internal variability of the climate system and the teleconnections between ocean–atmosphere oscillations and regional hydroclimate.

Tree mortality is a key factor influencing forest functions and dynamics, but our understanding of the mechanisms leading to mortality and the associated changes in tree growth rates are still limited. We compiled a new pan-continental tree-ring width database from sites where both dead and living trees were sampled (2970 dead and 4224 living trees from 190 sites, including 36 species), and compared early and recent growth rates between trees that died and those that survived a given mortality event. We observed a decrease in radial growth before death in ca. 84% of the mortality events. The extent and duration of these reductions were highly variable (1–100 years in 96% of events) due to the complex interactions among study species and the source(s) of mortality. Strong and long-lasting declines were found for gymnosperms, shade- and drought-tolerant species, and trees that died from competition. Angiosperms and trees that died due to biotic attacks (especially bark-beetles) typically showed relatively small and short-term growth reductions. Our analysis did not highlight any universal trade-off between early growth and tree longevity within a species, although this result may also reflect high variability in sampling design among sites. The intersite and interspecific variability in growth patterns before mortality provides valuable information on the nature of the mortality process, which is consistent with our understanding of the physiological mechanisms leading to mortality. Abrupt changes in growth immediately before death can be associated with generalized hydraulic failure and/or bark-beetle attack, while long-term decrease in growth may be associated with a gradual decline in hydraulic performance coupled with depletion in carbon reserves. Our results imply that growth-based mortality algorithms may be a powerful tool for predicting gymnosperm mortality induced by chronic stress, but not necessarily so for angiosperms and in case of intense drought or bark-beetle outbreaks., GGI by the Spanish Ministry of Economy and Competitiveness (Project AGL2014-61175-JIN)., AMH by the Spanish Ministry of Science and Innovation (Projects CGL2007-60120 and CSD2008-0040) and by the Spanish Ministry of Education via a FPU Scholarship., JJC, JCLC, and GSB by the Spanish Ministry of Economy (Projects CGL2015-69186-C2-1-R, CGL2013-48843-C2-2-R, and CGL2012-32965) and the EU (Project FEDER 0087 TRANSHABITAT).

International audience; Tree ring δ18O chronologies from two native species (Fitzroya cupressoides and Nothofagus pumilio) in northern Patagonia were developed to assess their potential for paleoclimate reconstructions. The five annually resolved cellulose δ18O chronologies (two for F. cupressoides and three for N. pumilio) are located on the Andes along the steep west-to-east precipitation gradient. Over the common 60 years long interval, the five site-δ18Ocell chronologies exhibit a strong common signal as indicated by the significant mean intercorrelation (r = 0.61, p \textless 0.05) and the high percentage (65%) of total variance explained by the first empirical orthogonal function. Although correlation analyses reveal that the two mean species-δ18Ocell chronologies are mainly modulated by December\textendashMay temperature, the N. pumilio chronology shows a greater sensitivity to record temperature variations (r = 0.57, p \textless 0.05). The δ18Ocell of N. pumilio contains a regional temperature signal representative of a large area in southern South America under the influence of the Southern Annular Mode. This study indicates that δ18Ocell in N. pumilio is a promising proxy to reconstruct past variations in temperature in South America south of 38°S.

As rainfall in South-Central Chile has decreased in recent decades, local communities and industries have developed an understandable concern about their threatened water supply. Reconstructing streamflows from tree-ring data has been recognized as a useful paleoclimatic tool in providing long-term perspectives on the temporal characteristics of hydroclimate systems. Multi-century long streamflow reconstructions can be compared to relatively short instrumental observations in order to analyze the frequency of low and high water availability through time. In this work, we have developed a Biobio River streamflow reconstruction to explore the long-term hydroclimate variability at the confluence of the Mediterranean-subtropical and the Temperate-humid climate zones, two regions represented by previous reconstructions of the Maule and Puelo Rivers, respectively. In a suite of analyses, the Biobio River reconstruction proves to be more similar to the Puelo River than the Maule River, despite its closer geographic proximity to the latter. This finding corroborates other studies with instrumental data that identify 37.5°S as a latitudinal confluence of two climate zones. The analyzed rivers are affected by climate forcings on interannual and interdecadal time-scales, Tropical (El Nino Southern Oscillation) and Antarctic (Southern Annular Mode; SAM). Longer cycles found, around 80-years, are well correlated only with SAM variation, which explains most of the variance in the Biobio and Puelo rivers. This cycle also has been attributed to orbital forcing by other authors. All three rivers showed an increase in the frequency of extreme high and low flow events in the twentieth century. The most extreme dry and wet years in the instrumental record (1943–2000) were not the most extreme of the past 400-years reconstructed for the three rivers (1600–2000), yet both instrumental record years did rank in the five most extreme of the streamflow reconstructions as a whole. These findings suggest a high level of natural variability in the hydro-climatic conditions of the region, where extremes characterized the twentieth century. This information is particularly useful when evaluating and improving a wide variety of water management models that apply to water resources that are sensitive to agricultural and hydropower industries.

Vegetation in primary succession is influenced by multiple stochastic and environmental factors at different spatial and temporal scales. In this study we analyze the effect of meso-topographic heterogeneity on vegetation development following the retreat of Glaciar Seco in the southern Patagonian Andes. Composition and cover of algae, lichens, mosses, and vascular plants were recorded in 580 plots located in different topographic positions within a chronosequence of eight consecutive moraines. Sample plots were characterized by topographical and surface features. Spatiotemporal patterns in vegetation composition and their relationships to environmental factors were assessed by classification and ordination. We recognized eight communities that correspond to four major successional stages. The successional sequence is characterized by a physiognomic development from pioneer saxicolous lichens (first stage) to secondary colonizer lichens (second stage), followed by shrub colonization (third stage)...

The lack of long-term records of productivity is a critical limitation to the study of ecosystem dynamics. Annual rings, a measure of growth in woody species, are a useful tool to document ecosystem dynamics. Time series of the Normalized Difference Vegetation Index (NDVI) provide estimates of ecosystem productivity through satellite-derived data on the fraction of photosynthetic active radiation absorbed by vegetation. In the Patagonian steppes, we relate changes in NDVI to interannual variations in the radial growth of the shrub Anarthrophyllum rigidum. A widely distributed network of 15 ring-width chronologies of A. rigidum was used to estimate changes in NDVI across the Patagonia steppe (35°–50°S). In most sites, interannual variations in shrub growth and NDVI are regulated by winter precipitation. The water accumulated in the soil during winter is used by A. rigidum during the growing season, concurrent with the maximum NDVI values. At 10 from the 15 selected sites, variations in the radial growth of A. rigidum explained between 23 and 62% of the total variance in seasonal NDVI, suggesting that the A. rigidum growth at some sites provides good estimates of productivity in the Patagonian shrubby steppes during the growing season. However, we were unable to determine clear relationships between radial growth and NDVI at high-elevation mountainous sites or where intensive grazing by sheep masked the effect of climate variability on shrub growth. We conclude that dendrochronological methods can complement other estimates to reconstruct variations of productivity, supplementing and extending the few short records available in the Patagonian steppe.

Deadwood is an important resource commonly used by inhabitants in arid lands. However, the low wood productivity and the presence of multi-stemmed trees restrict the use. Prosopis flexuosa woodlands are protected and inhabited by pastoralists who have land rights to use natural resources. As in other forests in the world, dead branches are the most commonly used. The factors causing the death of branches these trees are unknown. As P. flexuosa is a highly heliophilous species, branch mortality may depend on the growth habit and orientation of dry branches under the tree crown. With the participation of inhabitants, we assessed the present availability of deadwood in two Prosopis woodlands of different structure (semi-closed and open woodland), and evaluated the formation of deadwood in terms of shape and cardinal location of dry branches under the crown. We developed and compared regression models to estimate the amount of deadwood for erect, semi-erect and decumbent trees, and for the north and south areas under the crown ( n = 120 trees). In addition, to determine the period of growth decline and the factors determining branch mortality, we compared annual radial increment between live and dead branches ( n = 30 trees; 10 for each tree shape). The total amount of deadwood in adult Prosopis trees is higher in the semi-closed than in the open woodland (8.6 and 4.4 Tn ha −1 , respectively). Only tree size determined the amount of deadwood present in each Prosopis tree, since we found no evidence related to the shape of the tree or the position of dry branches in the canopy. Branch decay was a large process of 18–20 years, and branch death appears to be the result of the action of climatic factors (dry period). The results suggest that the use of deadwood by the desert inhabitants is a tool that can potentially be used; however, the use of this resource taking into account the generation rates of deadwood has not been developed in arid lands. These practices at appropriate sites can contribute to a sustainable management of these woodlands, including the removal of deadwood in a model of local management on a site where potential productivity is relatively low.

Snow avalanches recurrently cause substantial damage to infrastructure and losses in human lives in mountainous environments around the world. Densely populated regions have suffered more intensely the destructive forces of avalanches; however, settlers of these regions have developed tools to mitigate avalanche risk, including avalanche hazard maps. To design detailed hazard maps, accurate information on avalanche runout and frequency is necessary. In areas where avalanches are mostly undocumented, like in the Andes, dendrochronological methods become a valuable tool for reconstructing spatio-temporal avalanche patterns. At Lago del Desierto (southern Patagonian Andes, Argentina), trees from nine avalanche tracks were sampled. Nothofagus pumilio, a winter deciduous broad-leaved tree, was sampled in all cases. Avalanche activity is recognized based on the presence of scars, changes in stem eccentricity, reaction wood and abrupt growth changes. A rating system was used to define the relative importance of each tree-ring indicator in the reconstructed chronology of events. According to this chronology, widespread avalanche activity on the slope was found for the years 1918, 1930, 1931, 1971, 1995 and 1998. Superposed Epoch Analysis indicated that total monthly precipitation during the three snowiest months from May to October of 1971, 1995 and 1998 (years for which climatic data exists for validation) was significantly greater than for years without large avalanche activity. In contrast, no significant correlations were found between monthly temperature variations and years with large avalanche activity on the slope. Atmospheric circulation patterns associated with years of major avalanche activity show features typically observed during the cold phase of the El Nino–Southern Oscillation cycle, i.e. La Nina. For those cases, results also show an increase in the westerlies across the South Pacific and southern South America, resulting in both higher precipitation and stronger winds over the study area that favor snow avalanche episodes. We point out the need of a more systematic sampling strategy in order to reconstruct spatial avalanche patterns in the southern Andes, which are a complement of temporal patterns to design hazard maps.

A balance between forest production and protection is hard to achieve in arid zones due to their low potential for wood production. Prosopis flexuosa woodlands are the major woody formations in the Monte desert and are currently in a degraded state due to intense use. The main degradation factors in the study area are overgrazing and firewood extraction. We developed allometric models to estimate the aerial biomass of P. flexuosa, compared annual growth rates of one- and multi-stemmed individuals through dendrochronological methods, and estimated the productivity of four structurally different woodlands in the central Monte. Total dry weight was best estimated by power equations. Annual increments in basal area and dry weight were initially larger for multi- than one-stemmed individuals. However, whereas multi-stemmed individuals rapidly decreased their growth rates after 60 years of age, one-stemmed trees maintained steady growth rates during the first 100 years. Depending on woodland density and tree size, total woodland biomass varied between 4000 and 15 000 kg ha-1. Wood productivity was similar in all four woodlands studied (121.6-173.7 kg ha-1 year-1). Our results reveal the importance of tree growth habit to productivity, and suggest that regulated extraction of firewood and poles from old multi-stemmed individuals could optimize wood productivity and contribute to the sustainable use and conservation of these woodlands. Fil: Alvarez, Juan Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Villagra, Pablo Eugenio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Cony, Mariano Anibal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina Fil: Alberto, M.. Universidad Nacional de Cuyo; Argentina

In a recent study the authors developed the first regionally averaged, transnational records of snowpack and streamflow for the Andes between 30° and 37°S using Chilean and Argentinean data. That study was mainly intended to evaluate the relationships between the interannual variations in the regional snowpack record and large-scale atmospheric variables and indices. Here the focus is on the main intra- to multidecadal variations in updated records of winter snowpack and mean annual river flows. River discharges show similar temporal variations on both sides of the Andes with extreme dry conditions concentrated between the mid-1940s and 1976/77 and extreme wet conditions peaking between the late 1970s and the 1980s. A regional streamflow composite (1906–2007) has a nonsignificant negative trend but significant regime shifts in 1945, when mean levels dropped 31%, and in 1977 when they increased 28%. These events coincide almost exactly with well-known shifts in the Pacific decadal oscillation (PDO). The analyses are preliminary but suggest a PDO influence on the low-frequency modes of hydroclimatic variability in the study area. Analyses of the magnitude of 5–20-yr moving windows in the regional streamflow composite indicate that the most significant concentration of high (low) discharges occurred between 1977 and 1987 (1954 and 1971). Snowpack series show a more heterogeneous pattern of variations on a local basis but when aggregated into a regional series (1951–2008) they share remarkable similarities with river flows. However, the snowpack composite has a stronger year-to-year variability, a slight positive trend, and no significant regime shifts.

In this study, we use tree-ring records to determine the climate factors controlling the growth of Centrolobium microchaete, a high-value timber species from the tropical dry Chiquitano forest in Bolivia. We present the first tree-ring chronologies from C. microchaete for Concepcion and Santa Monica, Bolivia. Statistical analyses show that the chronologies are of good quality and have a significant common signal between trees. The growth of C. microchaete is strongly influenced by climatic conditions during late spring–early summer. Abundant precipitations concurrent with below-average temperatures during this period of the year favor tree growth. Climate variations in late spring–early summer explain >40 percent of the total variance in C. microchaete tree growth during the interval 1943–2005. Minor differences in tree responses to climate recorded between the two stands may reflect differences in the extent of the dry season and in soil water capacity between sites. Although the chronologies cover the past 180 yr, adding samples from older individuals would permit the extension of these records further back in time. The strong climate dependency of tree growth suggests that predicted future climate changes in the region could have a significant influence on C. microchaete tree growth during the 21st century. RESUMEN En este estudio se emplean los anillos de los arboles para determinar los factores climaticos que controlan el crecimiento de Centrolobium microchaete, una especie de alto valor maderable proveniente de los bosques tropicales secos de la Chiquitania en Bolivia. Se presentan las primeras cronologias de anillos de arboles de C. microchaete para las localidades de Concepcion y Santa Monica, Bolivia. Los analisis estadisticos muestran que las cronologias son de buena calidad y contienen una importante senal comun entre arboles. El crecimiento de C. microchaete esta fuertemente influenciada por las condiciones climaticas durante primavera-verano. Abundantes precipitaciones en conjunto con temperaturas por debajo del valor medio durante este periodo del ano favorecen el crecimiento radial de los arboles. Las variaciones climaticas a finales de la primavera-comienzos del verano explican mas del 40% de la varianza total en crecimiento de los arboles C. microchaete durante el intervalo 1943–2005. Pequenas diferencias en las respuestas de los arboles al clima registradas entre los dos rodales pueden reflejar diferencias en la extension de la estacion seca y en la capacidad de retencion de agua por el suelo entre ambos sitios. Aunque las cronologias solo cubren los ultimos 180 anos, la incorporacion de muestras provenientes de individuos de edad avanzada permitira extender estos registros dendrocronologicos mas atras en el tiempo. La fuerte dependencia climatica del crecimiento de los arboles indica que los futuros cambios climaticos predichos para la region podrian tener una influencia significativa en el crecimiento de los ejemplares de C. microchaete durante el siglo 21.

We statistically reconstruct austral summer (winter) surface air temperature fields back to ad 900 (1706) using 22 (20) annually resolved predictors from natural and human archives from southern South America (SSA). This represents the first regional-scale climate field reconstruction for parts of the Southern Hemisphere at this high temporal resolution. We apply three different reconstruction techniques: multivariate principal component regression, composite plus scaling, and regularized expectation maximization. There is generally good agreement between the results of the three methods on interannual and decadal timescales. The field reconstructions allow us to describe differences and similarities in the temperature evolution of different sub-regions of SSA. The reconstructed SSA mean summer temperatures between 900 and 1350 are mostly above the 1901-1995 climatology. After 1350, we reconstruct a sharp transition to colder conditions, which last until approximately 1700. The summers in the eighteenth century are relatively warm with a subsequent cold relapse peaking around 1850. In the twentieth century, summer temperatures reach conditions similar to earlier warm periods. The winter temperatures in the eighteenth and nineteenth centuries were mostly below the twentieth century average. The uncertainties of our reconstructions are generally largest in the eastern lowlands of SSA, where the coverage with proxy data is poorest. Verifications with independent summer temperature proxies and instrumental measurements suggest that the interannual and multi-decadal variations of SSA temperatures are well captured by our reconstructions. This new dataset can be used for data/model comparison and data assimilation as well as for detection and attribution studies at sub-continental scales

The significant mortality of the Austrocedrus chilensis (D. Don) Pic. Serm. et Bizarri forests, locally known as “Mal del Cipres”, has been reported since 1945 for most sites across its distribution in Argentina. However, the cause of this decline is still a topic of discussion. In this study, radial growth patterns from symptomatic and asymptomatic A. chilensis trees were analyzed to determine the influence of drought events on tree growth. Fifty pairs of symptomatic and asymptomatic trees with similar DBH, competition, and microsite conditions were cored at five pure A. chilensis stands near El Bolson, Rio Negro, Argentina. A reference chronology from nonaffected trees was used to cross-date all cores and to determine the relationship between A. chilensis radial growth and climate. The growth of A. chilensis is favored by above average precipitation in late spring–early summer (November and December). A strong relationship was also observed between radial growth patterns and the Palmer drought severity index, a measure of the regional water deficit. Significant differences in growth patterns were recorded between symptomatic and asymptomatic trees. Following extreme drought events, the growth of symptomatic trees is consistently lower than in asymptomatic trees. Based on the larger number of droughts recorded during the past decades and on future climatic predictions suggesting increasing trends in the frequency and intensity of drought events in northern Patagonia, a gradual increase in the number of trees affected by “Mal del Cipres” along the twenty-first century is likely expected., Laboratorio de Investigación de Sistemas Ecológicos y Ambientales, Instituto de Biotecnología y Biología Molecular

Little Ice Age (LIA) fluctuations of Glaciar R"o Manso, north Patagonian Andes, Argentina are studied using information from previous work and dendrogeomorphological analyses of living and subfossil wood. The most extensive LIA expansion occurred between the late 1700s and the 1830"1840s. Except for a massive older frontal moraine system apparently predating ca. 2240 14C yr BP and a small section of a south lateral moraine ridge that is at least 300 yr old, the early nineteenth century advance overrode surficial evidence of any earlier LIA glacier events. Over the past 150 yr the gently sloping, heavily debris-covered lower glacier tongue has thinned significantly, but several short periods of readvance or stasis have been identified and tree-ring dated to the mid-1870s, 1890s, 1900s, 1920s, 1950s, and the mid-1970s. Ice mass loss has increased in recent years due to calving into a rapidly growing proglacial lake. The neighboring debris-free and land-based Glaciar Fr"as has also retreated markedly in recent years but shows substantial differences in the timing of the peak LIA advance (early 1600s). This indicates that site-specific factors can have a significant impact on the resulting glacier records and should thus be considered carefully in the development and assessment of regional glacier chronologies.

Annual growth rings are well-defined in some shrubby species distributed along the Patagonian steppe and provide useful information to identify the environmental factors that influence the radial growth of shrubs in the region. However, little is known about variations in ring width from these species and their relationships with local environment. In this paper we present 18 growth ring width chronologies covering the last 2–3 decades from the shrub Anarthrophyllum rigidum (Fabaceae) encompassing most of its natural range of distribution in Argentina. Interannual variations in growth were first analyzed collectively to identify common regional patterns. In addition, shrub growth at each site was compared with local climate records and site-specific characteristics. Based on a principal component analysis (PCA), sites were joined in four major groups related to the site proximity to the Andes (foothills versus Patagonian plateau) and latitude (north versus south Patagonia). The relatively similar percentage of PCA variance associated with each group reflects environmental differences among sites. Consistent with this observation, we noted large variability in the responses of the A. rigidum woody growth to regional climatic fluctuations. At most sites, this species is favored by abundant winter precipitation, warmer spring and autumn temperatures (controlling the duration of the growing season), cool summers, or a combination of these factors. However, deviations from these patterns are also recorded. Our study represents the first large-scale dendroclimatological analysis of a shrubby species in southern South America. The results presented here provide information on the main patterns and factors affecting the growth of A. rigidum in Patagonia, and may be useful for determining well-suited practices for management and conservation of this ubiquitous species.

article i nfo This paper presents an updated, extensive review of glacier fluctuations during the past 1000 years in the extratropical Andes of South America between ca. 17° and 55°S. Given the variety of environmental conditions and evidence available for glacier fluctuations across this wide latitudinal range, regional accounts are given for the Desert Andes (∼17°-31°S), the Andes of central Chile and Argentina (31°-36°S), and the North (36°-45°S) and South (45°-55°S) Patagonian Andes. The techniques, dating limitations, and interpretations of the glacier records along this transect are also discussed. Information on glacier fluctuations in the Desert Andes is limited to the 20th century. Documentation on past glacier variations is more abundant in the Central Chilean-Argentinean Andes, but the number of chronologies dealing with glacier fluctuations prior to the 1900s is also limited. Most records indicate that glaciers were generally more extensive prior to the 20th century, with dates of maximum expansion ranging from the 16th to the 19th centuries. The number and extent of glaciers increase significantly in the Patagonian region, where the evidence available for dating glacier variations during the past centuries is more abundant and the dating control for glacier events is generally better than in the northern parts of the study area. For some Patagonian glaciers, maximum Little Ice Age (LIA) or post-LIA advances have been precisely dated by dendro- geomorphological determinations or in situ measurements. However, for most sites, the evidence available is still preliminary and there is considerable variability in the extent and timing of events related to the maximum LIA expansion identified in most areas between the 16th and 19th centuries. Evidence is starting to appear at a growing number of sites for glacier advances during the first half of the past millennium. These events were generally less extensive than the LIA maximum pulses. Despite the occurrence of several post- LIA readvances over the past 100-110 years, most areas in the Andes of extratropical South America have experienced a general pattern of glacier recession and significant ice mass losses. The differences in the glacier histories observed at local and regional scales probably reflect the inherent limitations associated with the glacier records and/or the dating techniques used in each case together with the varying dominance of precipitation, temperature and other climatic and non-climatic factors on glacier mass balance and glacier dynamics. These differences indicate that the late Holocene glacier history of southern South America is more complex than commonly assumed. The evidence discussed in this study highlights not only the immense potential for glaciological studies of this region but also a significant need for an increased number of detailed, well-dated records of glacier fluctuations.

High-resolution, multi-proxy climate reconstructions with a representative spatial coverage over the globe are arguably among the most important tools for the assessment of the responses of the Earth climate to natural and anthropogenic forcing. Whereas hemispheric or regional multi-proxy reconstructions for the past 500–1000 years are available for Europe and North America, the Southern Hemisphere including South America has remained largely terra incognita. In this special issue we present a comprehensive review of previously published and new data sets from a variety of paleoclimate archives across southern South America (south of ca. 15°S). The underlying collaborative research initiative started in 2006 under the umbrella of IGBP-PAGES Focus 2 “Regional Climate Dynamics” and aimed to (i) collate the large number of disperse paleoclimate data sets from various proxies for the last ca. 1000 years, and (ii) produce a spatially explicit, highly resolved, multi-proxy climate reconstruction for southern South America. The review and research articles in this special issue cover a variety of archives (historical documents, tree rings, ice cores, glacier fluctuations and lacustrine sediments) and suggest that, at least south of ca. 18°S, the spatial and temporal coverage of the data is adequate to develop synoptic multi-proxy reconstructions for the past ca. 400 years. Although additional high-quality proxy records are still needed to resolve the finer temporal and spatial structure of past climate variations, the currently available data do provide a consistent picture of climate fluctuations at a large scale. We have identified two major directions for future research: (i) a dedicated effort to build a comprehensive, quality-tested, and homogenized set of climate data during the (early) instrumental period in order to calibrate proxy data series, to test and extend reanalysis data sets, and to explore the multi-decadal variability of synoptic-scale atmospheric features, and (ii) expansion of the database of robust well-calibrated paleoclimate data series of adequate quality, temporal resolution and spatial representation; currently, this is the bottleneck for further improvements of the reconstructions. Existing older data sets should be updated to include the most recent years. While well-calibrated tree-ring archives and documentary data have restrictions in terms of spatial coverage and/or the length of the data series, calibration and quantification of proxy series from ice cores, glacier fluctuations, lake sediments and vegetation records are of utmost concern and require greatest attention.

We document the dendroclimatological potential of Polylepis tarapacana to estimate past temporal and spatial variations in precipitation across the Bolivian Altiplano (17–23°S). The P. tarapacana chronologies, which presently range between 110 and 705 years in length, represent the highest altitude tree-ring records worldwide. Interannual variations in fourteen tree-ring chronologies located between 3900 and 4850 m elevation were compared using correlation and principal component analyses. There is a strong common signal among the chronologies. For the common interval AD 1890–1999, three dominant patterns of tree growth across the Bolivian Altiplano were identified. The first pattern which explains 52% of the total variance in tree growth is associated with years of above- or below-average tree growth across the whole region. The second and third patterns, which are related to significantly lower common variance (13 and 8%, respectively), are associated with contrasting positive and negative anomalies of growth between the northern and southern sectors, and between the central-western sector and the rest of the region, respectively. In order to determine the climatic significance of the spatial variations of P. tarapacana growth, the interannual patterns in tree growth were compared with spatial anomalies in precipitation across the region. Uniform patterns of above (below) average tree growth are associated with positive (negative) precipitation anomalies in the preceding year that are uniformly distributed across the whole Altiplano. In the westernmost areas of the Altiplano, summer rainfall accounts for more than 80% of total annual precipitation. Therefore, relationships between tree growth and summer or annual precipitation are, in most cases, similar. Contrasting patterns of tree growth are related to opposite anomalies in precipitation during the preceding year in the different sub-regions in the Altiplano (north versus south, central versus north and south). Climatic preconditioning of tree growth was also identified for individual years. For instance, extremely reduced growth in the year 1967 reflects dry conditions in the two preceding years (1965–1966). Long-term intervals (3 or more years) with reduced tree growth resulted from several consecutive years with low precipitation. Our results indicate that the network of tree-ring chronologies of P. tarapacana in the Bolivian Altiplano has the potential to provide annually-resolved precipitation reconstructions in this region for the past 5–7 centuries. This is a valuable source to document decadal-to-century-scale precipitation variability in the Altiplano and its relation to large-scale ocean–atmosphere circulation features.

article i nfo El Nino-Southern Oscillation (ENSO) is the largest source of inter-annual variability operating in the earth's climate system with enormous ecological, social, and economic impacts. As the instrumental record of ENSO variability is limited to the past 150 yr, the search for proxies sensitive to ENSO has become a priority task in recent years. It is vital to expand the sparse network of annually resolved and exactly dated ENSO-sensitive proxies to entirely capture the spatial variability of the ENSO coupled ocean-atmospheric phenomenon. Several tree-ring records have been used to reconstruct past ENSO variability, however, none of them are from tropical South America. The Polylepis tarapacana woodlands form the world's highest elevation treeline. Trees grow on the Altiplano plateau between 4000-5200 m elevation (16°-23° S). The climate variability in this climatically transitional tropical-subtropical region is strongly modulated by ENSO. Two chronologies of P. tarapacana along the Western Cordillera in the tropical central Andes were analyzed to determine the strength of the ENSO signal present in these tree-ring records. The growth of P. tarapacana has a strong common signal amongst trees in a single site and between sites across the Altiplano. Ring formation is induced by climatic conditions during the previous and current growing season (December-February), at the time of the strongest ENSO influences on the Peruvian Coast. Tree growth variations show opposite relationships with climate between consecutive growing seasons. During the current growing season, ring-width variations show positive and negative relationships with temperature and precipitation, respectively. Both tree-ring chronologies are significantly correlated with austral spring-summer (August-February) SST in the Nino3.4 region and show oscillatory modes within the classical ENSO bandwidth. Our results support the idea that P. tarapacana chronologies from the south- central tropical Andes provide high-resolution records extremely sensitive to ENSO in the tropical Pacific, and represent an important component to be considered in future multiproxy ENSO reconstructions.