Ofelia Gutiérrez

The continental Uruguayan Cenozoic: an overview

Abstract Although Quaternary study in Uruguay was started in the 1970s, international diffusion of the results has been limited. This contribution is an updating of the continental aeolian and fluvial Cenozoic period, reinterpreted mostly from a geomorphological perspective. We discuss the limitations in the usage of chronostratigraphic generalizations in the Cenozoic based on a lithostratigraphic interpretation. The upper Pleistocene and the Holocene are reinterpreted through available 14 C dates, presenting a comparative preliminary table with the geological formations found in the neighbouring Argentine Provinces of Entre Rios and Corrientes.

The irruption of new agro-industrial technologies in Uruguay and their environmental impacts on soil, water supply and biodiversity: a review

In recent years, economic growth has produced a global change in the demand for food, fibre and energy supply. This has gone together with the globalisation of the agro-industrial production systems, leading to a qualitative change in land use because of intensive use of technological inputs. Uruguay, just as the other countries of the region, is part of this phenomenon. The massive introduction of forest crops has been made over native grassland ecosystems, replacing traditional productive activities of the post-colonial period. Research on eucalyptus afforestation shows depletion of the ecosystem services associated with grassland and loss of the resilience capacity of the system. Impacts on soil organic matter, soil physicochemical properties, the hydrological cycle and on biodiversity are analysed. This review (with emphasis on Uruguay and the River Plata Basin) tries to contribute to an integrated vision of the environmental consequences of current land-use change.

Land use change in a temperate grassland soil: afforestation effects on chemical properties and their ecological and mineralogical implications.

The current change in land use of grassland in the temperate region of South America is a process associated with the worldwide expansion of annual crops and afforestation with fast growing exotic species. This last cultivation has particularly been the subject of numerous studies showing its negative effects on soil (acidification, loss of organic matter and base cations, among others). However its effects on the mineral fraction are not yet known, as it is generally considered as one of the slowest responses to changes. This stimulated the present study in order to assess whether the composition of clay minerals could be altered together with some of the physicochemical parameters affected by afforestation. This study compares the mineralogical composition of clays by X-ray diffraction (XRD) in a grassland soil (Argiudolls) under natural coverage and under Eucalyptus grandis cultivation implanted 25 years ago in a sector of the same grassland. The tendency of some physicochemical parameters, common to other studies was also compared. XRD results showed, as a most noticeable difference in A(11) and A(12) subhorizons (~20 cm) under eucalyptus, the fall of the 10Å spectrum minerals (illite-like minerals), which are the main reservoir of K in the soil. Meanwhile, the physicochemical parameters showed significant changes (p<0.01) to highly significant ones under eucalyptus, particularly in these subhorizons, where on average soil organic matter decreased by 43%; K(+) by 34%; Ca(2+) by 44%, while the pH dropped to this level by half a point. Our results show that the exportation of some nutrients is not compensated due to the turnover of organic forestry debris; the process of soil acidification was not directly associated with the redistribution of cations, but with an incipient podzolization process; the loss of potassium together with soil acidification, leads to a drastic change in clay mineralogy, which would be irreversible.

La vegetación en la evolución de playas arenosas. El caso de la costa uruguaya.

La descomposici??n de materia org??nica (MO) es uno de los procesos claves en el funcionamiento de los todos los ecosistemas, incluidos los acu??ticos. Cada a??o los productores primarios fijan cerca de 100 gigatoneladas de carbono org??nico, y cada a??o, pr??cticamente la misma cantidad de MO es descompuesta completando el ciclo global de carbono. No obstante, aunque la descomposici??n constituye un proceso ecosist??mico, de importancia comparable a la producci??n primaria, se conoce mucho mejor todo lo relacionado con ??sta ??ltima y el papel que desempe??an los organismos aut??trofos en la misma, que lo relativo a los procesos de descomposici??n y, especialmente, al papel que llevan a cabo los microorganismos en ellos. Existen diferentes razones para este desconocimiento. La m??s importante es que la descomposici??n es un proceso muy complejo que se manifiesta a nivel de comunidad, involucrando a m??ltiples organismos a distintas escalas espaciales y temporales, mientras que la producci??n primaria es un proceso que, en ??ltima instancia, se manifiesta a nivel de cada organismo aut??trofo de forma individual e involucra a una fracci??n mucho menor de biodiversidad. Por otro lado, es muy complejo analizar la fracci??n microbiana que desarrolla la mayor parte de los procesos de descomposici??n y s??lo muy recientemente se han empezado a desarrollar t??cnicas para estudiar el funcionamiento in situ de estas comunidades. Por todo ello, los estudios funcionales sobre el papel de la descomposici??n en los ecosistemas son muy escasos, a pesar de las implicaciones que esto puede tener en la comprensi??n del ciclo de carbono y procesos relacionados, como el cambio clim??tico y los mecanismos de intercambio de carbono entre la atm??sfera y los ecosistemas acu??ticos y terrestres. Esto es especialmente importante para los humedales, que constituyen uno de los sistemas m??s productivos del planeta y donde la mayor??a de carbono se acumula en forma de MO que entra en la v??a detr??tica.

Evolução morfológica de longo prazo das praias urbanas de bolso de Montevidéu (Uruguai): impactos das intervenções costeiras e relações com as forçantes climáticas

Two pocket beaches, Ramirez and Pocitos (Montevideo, Uruguay) are analyzed to assessing their evolution (erosion/accretion) associated with human interventions and climatic forcings from 1927-2008. A multitemporal study was conducted using GIS, long series of aerial photos, satellite imagery, survey of historical background, and statistical analysis. Qualitative indicators of the stability of the beach area are proposed. The relevance of this methodology is analyzed on beaches whose fluctuations tend to mask their long-term evolution. Both beaches remain relatively stable but fluctuating since 1927, with slight loss of surface, especially in Ramirez. The influence of the following factors is discussed: i) human interventions; ii) ENSO events; iii) storm surges; iv) changes in beach area according to the Bruun rule and rising sea level in Montevideo. Although the four of them appear to have acted in different periods, the evidence is not conclusive regarding their relative quantitative importance. This article highlights the importance of using long series of remote sensing and historical analysis to interpret processes linked to inertia of the past in environments that have been modified from longstanding. The trend analysis of these two urban pocket beaches allows to infer that their resilience has not been affected yet, which would allow them to face not extreme climatic stressors. For the purpose of better management it is recommended to: i) conduct continuous monitoring; ii) minimize the ac- tions of mechanized cleaning and sand losses by leakage or removal; iii) implement the reconstruction of natural structures such as primary dunes; and iv) apply the methodology explained in this paper in other Montevideo urban beaches to better un- derstand the climate forcings.

Ancient Landscapes of Uruguay

In this chapter, based on the available geological information, a model for the genesis and evolution of the Uruguayan landscape is proposed. A structural framework of the landscape evolution is provided and the record of such evolution in the most representative geological units is considered. A brief summary of the Uruguayan geology and its location in the regional context is performed, from Precambrian to Cenozoic times.

Building capacity on ecosystem-based adaptation strategy to cope with extreme events and sea-level rise on the Uruguayan coast

Purpose This study aims to show a case study of ecosystem-based adaptation (EbA) measures to increase coastal system’s resilience to extreme weather events and sea-level rise (SLR) implemented at Kiyu (Uruguayan coast of the Rio de la Plata river estuary). Design/methodology/approach A participatory process involving the community and institutional stakeholders was carried out to select and prioritise adaptation measures to reduce the erosion of sandy beaches, dunes and bluffs due to extreme wind storm surge and rainfall, SLR and mismanagement practices. The recovery of coastal ecosystems was implemented through soft measures (green infrastructure) such as revegetation with native species, dune regeneration, sustainable drainage systems and the reduction of use pressures. Findings Main achievements of this case study include capacity building of municipal staff and stakeholders, knowledge exchanges with national-level decision makers and scientists and the incorporation of EbA approaches by subnational-level coastal governments. To consolidate EbA, the local government introduced innovations in the coastal management institutional structure. Originality/value The outcomes of the article include, besides the increase in the resilience of social-ecological systems, the strengthening of socio-institutional behaviour, structure and sustainability. This experience provides insights for developing a strategy for both Integrated Coastal Management and climate adaptation at the national scale.