The south of , as most of Argentina, is a semiarid region. Its economy is based on rain-fed agriculture and livestock. Traditionally, the climate has been studied considering the analyses of monthly and annual climate parameters, but there is evidence that in this type of areas, the short-term climatic events have a substantial impact on the climate. Therefore, this study aimed at developing a climate regionalization from the analysis of daily temperature and precipitation extremes in the south of the Pampas for the period 1970-2017. Subsequently, it focuses on analyzing both trends and breakpoints of these events in the different sub-climates. To do so, we applied a Cluster-based Principal Component Analyses with a Ward hierarchical supervised method to generate a climate regionalization considering 29 daily extreme climatic indices and the elevation. We identify four sub-regions, and we analyzed trends during 1970-2017, and in the two-time series defined by applying breakpoints. Both minimum and maximum temperatures and precipitation had structural changes in the last 15 years, exposing the region to warming and dryness trends. The maximum temperature increases 0.5ºC, while precipitation decreases 30 mm. The short-term climate variability allows us to identify areas climatically more detailed and to conclude that the south of the Pampas is characterized by its high dependency on short-term climatic events. Regionalización y tendencias climáticas basadas en eventos extremos térmicos y pluviométricos diarios en el sur de la Región Pampeana (Argentina)RESUMEN. El sur es, al igual que la mayor parte de Argentina, una región semiárida. Su economía se basa en la agricultura de secano y la ganadería. Tradicionalmente, el clima Ferrelli et al. 394Cuadernos de Investigación Geográfica 45 (1), 2019, pp. 393-416 ha sido estudiado considerando los eventos térmicos y pluviométricos mensuales y anuales. Sin embargo, existe evidencia científica de que los eventos climáticos a corto plazo (diarios) tienen un impacto sustancial en el clima. El objetivo de este trabajo es desarrollar una regionalización climática a partir del análisis de las temperaturas y precipitaciones diarias extremas en el sur de la Región Pampeana durante el período 1970-2017. Complementariamente, este trabajo se enfoca en analizar las tendencias de estos eventos en cada sub-clima durante dos períodos de tiempo de la serie 1970-2017. Para generar la regionalización, aplicamos un Análisis de Componentes Principales y un Análisis de Conglomerados utilizando el método supervisado de Ward, considerando 29 índices climáticos extremos diarios y la elevación. Como resultado obtuvimos cuatro subregiones. Además, analizamos la tendencia de los 29 índices climáticos extremos diarios durante el período 1970-2017 y en dos sub-series dentro de este período definidas mediante la aplicación de puntos de interrupciones o cambios estructurales. En el sur de la región Pampeana, la temperatura y la precipitación presentaron cambios estructurales en los últimos 15 años, lo q...

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Understanding the drivers and how they affect ecosystem metabolism is essential for developing effective management policy and plans. In this study, net ecosystem production (NEP), ecosystem respiration (R), and gross primary production (GPP) rates were estimated in relation to physicochemical, hydrological, and meteorological variables in La Salada (LS) and Sauce Grande (SG), two shallow lakes located in an important agricultural region with water management. LS is a mesosaline, mesotrophic-eutrophic lake, whereas SG is a hyposaline and eutrophic lake. GPP and R showed daily and seasonal variations, with R exceeding GPP during most of the study period in both lakes. Net heterotrophic conditions prevailed during the study period (NEP LS: −1.1 mmol O2 m−2 day−1 and NEP SG: −1.25 mmol O2 m−2 day−1). From data analysis, the temperature, wind speed, and lake volume are the main drivers of ecosystem metabolism for both lakes. Despite the significant differences between the two lakes, the NEP values were similar. The different hydrological characteristics (endorheic vs. flushing lake) were crucial in explaining why the two different systems presented similar ecosystem metabolic rates, emphasizing the importance of water management.