The role of South American grazing lands in mitigating greenhouse gas emissions:A reply to "Reassessing the role of grazing lands in carbon-balance estimations: Meta-analysis and review", by Viglizzo et al., (2019)

The paper by Viglizzo et al. (2019) "Reassessing the role of grazing lands in carbon-balance estimations: Meta-analysis and review" proposed a new methodology to assess changes in soil organic carbon (SOC) stock associated with land use, and applied it to four countries of South America: Argentina, Brazil, Paraguay, and Uruguay, all members of the MERCOSUR trade bloc. One finding of their assessment was that grazing lands are currently accumulating SOC at rates high enough to"... generate C surpluses that could not only offset rural emissions, but could alsopartially or totally offset the emissions of non-rural sectors".Fil: Villarino, Sebastián Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias. Laboratorio de Agroecología; ArgentinaFil: Pinto, Priscila. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Della Chiesa, Tomás. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Jobbagy Gampel, Esteban Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; ArgentinaFil: Studdert, Guillermo Alberto. Universidad Nacional de Mar del Plata; ArgentinaFil: Bazzoni, Bruno. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Conti, Georgina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Rufino, Mariana Cristina. Lancaster University; Reino UnidoFil: Alvarez, Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Boddey, Robert. Embrapa Agrobiologia; BrasilFil: Bayer, Cimélio. Universidade Federal do Rio Grande do Sul; BrasilFil: de F. Carvalho, Paulo C.. Embrapa Agrobiologia; BrasilFil: Fernández, Roberto J.. Universidade Federal do Rio Grande do Sul; BrasilFil: Lattanzi, Fernando Alfredo. Universidade Federal do Rio Grande do Sul; BrasilFil: Oesterheld, Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Oyhantçabal, Walter. Instituto Nacional de Investigación Agropecuaria; UruguayFil: Paruelo, José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Pravia, Virginia. Ministerio de Ganadería; UruguayFil: Piñeiro, Gervasio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentin

Surface and groundwater dynamics in the sedimentary plains of the Western Pampas (Argentina)

The study describes groundwater dynamics and water-body expansion in a 10-year flooding cycle in the agricultural lands of the Western Pampas. It analyzes water-table depth, surface water coverage, and rainfall (1996 to 2005). Ground and surface water dynamics were closely coupled. This connection, and the relatively slow process of cumulative water accretion and coalescence of water bodies that precedes flood events, together offer the opportunity of developing warning systems that could help land managers adapt to climate changes. However, the link differs between lowlands and highlands. It also depends on whether the system is at the gaining or retraction stage

Hydrologic consequences of land cover change in central Argentina

Vegetation exerts a strong control on water balance and key hydrological variables like evapotranspiration. water yield or even the flooded area may result severely affected by vegetation changes. Particularly, transitions between tree- and herbaceous-dominated covers, which are taking place at increasing rates in South America, may have the greates.t impact on the water balance. Based on Landsat imagery analysis, soil sampling and hydrological modeling, we evaluated vapor and liquid ecosystem water fluxes and soil moisture changes in temperate Argentina and provided a useful framework to assess potential hydrological impacts of vegetation cover changes. Two types of native vegetation (grasslands and forests) and three modified covers (eucalyptus plantations. single soybean crop and wheat/soybean rotation) were considered in the analysis. Despite contrasting structural differences, native forests and eucalyptus plantations displayed evapotranspiration values remarkably similar ( -1100 mm y- 1) and significantly higher than herbaceous vegetation covers ( -780, - 670 and - 800 mm y-1 for grasslands, soybean and wheat/soybean (Triticum aestivum L, Glycine max L.) system, respectively. In agreement with evapotranspiration estimates, soil profiles to a depth of 3m were significantly drier in woody covers (31m3 m-3) compared to native grasslands (39m3 m-3 ). soybean (38.5 m3 m- 3) and wheat/soybean rotation (35m3 m-3 ). Liquid water fluxes (deep drainage+ surface runoff) were at least doubied in herbaceous covers. as suggested by modeling( - 170 mmy-1 and -357 mm y- 1. for woody and herbaceous covers. respectively). Our analysis revealed the hydrological outcomes of different vegetation changes trajectories and provided valuable tools that will help to anticipate likely impacts, minimize uncertainties and provide a solid base for sustainable land use planning

Reciprocal influence of crops and shallow ground water in sandy landscapes of the Inland Pampas

The analysis shows that in flat humid landscapes such as the Pampas, crops and shallow ground water are closely connected and influence each other. An optimum groundwater depth range where crop yields were highest was observed for all three crop species analyzed (wheat, maize, and soybean). The areas within these optimum bands had yields that were respectively, 3.7, 3 and 1.8 times larger than those where the water table was below 4 m. As groundwater levels become shallower crop yields declined sharply. Understanding complex interactions and simultaneous occurrences could provide keys to regulating the labile hydrology of these plains

Water subsidies from mountains to deserts : their role in sustaining groundwater-fed oases in a sandy landscape

The study indicates a reliance of ecosystem productivity on Andean snowmelt, which is increasingly being diverted to one of the largest irrigated regions of the continent. Deep soil coring, plant measurements, direct water-table observations, and stable isotopic analyses (2H and 18O) of meteoric, surface, and ground waters, were used to compare woodland stands, bare dunes, and surrounding shrublands. The isotopic composition of phreatic groundwaters closely matched the signature of water brought to the region by the Mendoza River, suggesting that mountain-river infiltration, rather than in situ rainfall deep drainage was the dominant mechanism of groundwater recharge

Interactive effects of water-table depth, rainfall variation, and sowing date on maize production in the Western Pampas

tShallow water-tables strongly influence agro-ecosystems and pose difficult management challenges tofarmers trying to minimize their negative effects on crops and maximize their benefits. In this paper, weevaluated how the water-table depth interacts with rainfall and sowing date to shape maize performancein the Western Pampas of Argentina. For this purpose, we analyzed the influence of water-table depthon the yields of 44 maize plots sown in early and late dates along eight growing seasons (2004–2012)that we rated as dry or wet. In addition, we characterized the influence of the water-table depth onintercepted radiation and crop water status by analyzing MODIS and Landsat images, respectively. Thefour conditions we evaluated (early sown-dry growing season, early-wet, late-dry, late-wet) showedsimilar yield response curves to water-table depth, with an optimum depth range (1.5–2.5 m) whereyields were highest and stable (∼11.6 Mg ha−1on average). With water-table above this range, yieldsdeclined in all conditions at similar rates (p > 0.1), as well as the crop water status, as suggested bythe Crop Water Stress Index, evidencing the negative effects of waterlogging. Water-tables deeper thanthe optimum range also caused declines of yield, intercepted radiation and crop water status, beingthese declines remarkably higher in early maize during dry seasons, evidencing a greater reliance of thiscondition on groundwater supply. Yield in areas with deep water-tables (>4 m) was significantly reducedto between a quarter and a half of yields observed in areas with optimum water-tables. Rainfall occurredaround flowering had a strong impact on maize yield in areas with deep water-tables, but not in areaswith optimum depth, where yields showed high temporal stability and independence from rainfall in thatperiod. Our study confirmed the strong influence of water-table on rainfed maize and provides severalguidelines to help farmers to take better decisions oriented to minimize hydrological risks and maximizethe benefits of shallow water-tables

Regional patterns and controls of ecosystem salinization with grassland afforestation along a rainfall gradient

In this study, salinization occurred rapidly where rainfall was insufficient to meet the water requirements of tree plantations, and where groundwater use compensated for this deficit, it was the driving factor for salt accumulation in the ecosystem. Vegetation change affects water fluxes, and influences the direction and intensity of salt exchange between ecosystems and groundwater. It can lead to an intense accumulation of salts in soils and aquifers, as evidenced in conversion from native grassland to tree plantation. An understanding of the vegetation-groundwater relationship helps predict and manage the consequences of groundwater use from stand to regional levels of analysis

Cambios en el uso de la tierra en Argentina y Uruguay : marcos conceptuales para su análisis

Resumen en inglés incluidoEl ser humano modifica el territorio para llevar a cabo actividades productivas o construir viviendas. Estas modificaciones producen importantes cambios en la estructura y el funcionamiento de los ecosistemas, afectando en última instancia la propia calidad de vida de las personas. En este artículo en primer término describimos algunos de los cambios ocurridos en el uso de la tierra en buena parte de Argentina y Uruguay. Utilizamos conjuntamente información aportada por estadísticas oficiales de ambos países y datos resultantes del procesamiento y clasificación de imágenes satelitales. Nuestros análisis muestran que tanto el área agrícola como forestal se han expandido en los últimos años. En Argentina, la mayor expansión la tuvieron los cultivos anuales (desde un 4% a un 14.3%, entre 1988 y 2002) y particularmente la soja, tanto en la provincia de Buenos Aires como en las provincias del Norte Argentino. En Uruguay la mayor expansión entre los censos de 1990 y 2000, estuvo dada por los cultivos forestales, los cuales llegaron a ocupar más del 35 % del área de algunas secciones censales. Luego del 2000, la expansión de la soja también afectó el litoral uruguayo, donde varias secciones censales aumentaron su área de soja a tasas cercanas al 5% anual. En segundo término, presentamos el marco conceptual a los efectos de entender los procesos que determinan estos cambios y examinar su dinámica espacial y temporal. En base a este marco conceptual es posible modelar los cambios en el uso de la tierra a partiendo de la probabilidad de transición entre usos. Los controles de estas transiciones pueden ser ambientales (por ej. tipos de suelos, clima, etc.), económicos (por ej. margen bruto, precios internacionales, etc), sociales (por ej. disponibilidad de mano de obra, tenencia de la tierra, etc.), o políticos (por ej. la ley forestal, política impositiva, líneas de créditos, etc.). Finalmente usando la idea de servicios ecosistémicos presentamos un marco conceptual para la planificación del uso de la tierra considerando sus impactos ambientales, sociales, económicos y políticos