Artículos y presentaciones en Congresos
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Embargado Shrub encroachment in semi-arid rangelands of southwestern Buenos Aires, Argentina does not affect plant diversity and composition(2024) Torres, Yanina Alejandra; Ithurrart, Leticia S.; Ambrosino, Mariela L.; Brendel, Andrea S.; Blazquez, Francisco R.; Armando, Lorena V.; Pezzola, AlejandroShrub encroachment in semi-arid rangelands is a phenomenon associated with changes in floristic composition, loss of diversity and ecosystem degradation, enhanced by inappropriate grazing practices. However, the outcome depends on the species’ identity and the management carried out. The objective of this study was to evaluate shrub species dynamics and their effect on plant community composition in a Monte rangeland of Argentina, under conservative grazing management at two different working scales. During two years, ground-based vegetation and soil cover measurements were performed in patches with and without shrubs using Dau-benmire and Canfield’s methods. Herbaceous and woody species recorded were classified according to their functional traits and forage value. Specific richness, Shannon’s diversity index and Pielou’s evenness were calculated. At a larger-scale evaluation, Sentinel-2A satellite images from year 2016–2022 were classified into three cover classes to evaluate the shrub encroachment process. Although an increase in shrub presence was observed over the years at both scales no effect was found on the diversity and specific composition, nor on the occurrence of forage species. Shrub presence promotes the coexistence of species with different functional traits and creates favorable conditions for soil protection and the establishment of desirable species for livestock purposes. - Artículo
Acceso Abierto Morphological traits which contribute to the long-term persistence of Pappophorum vaginatum in rangelands of Argentina(2020) Torres, Yanina Alejandra; Busso, Carlos; Ithurrart, Leticia; Ambrosino, MarielaPappophorum vaginatum is the most abundant C4 perennial grass desirable (i.e., preferred) to livestock in rangelands of northeastern Patagonia, Argentina. Other less abundant, native perennial grasses in the community are Aristida spegazzinii and A. subulata, and the desirable Sporobolus cryptandrus. Aristida spegazzini and A. subulata are only grazed when a better forage is not available. The objective of this study was to determine various above- and belowground morphological traits that might help to explain the greater abundance of P. vaginatum in relation to the other species, in a community where P. vaginatum is the only perennial grass available for livestock grazing since decades ago. Plants of all species were either exposed or not exposed to a severe defoliation twice a year during two growing seasons (i.e., 2007-2008 and 2008-2009). These growing seasons had 42 % (2007-2008) and 30 % (2008-2009) lower precipitation than the annual mean precipitation (i.e., 416.7 mm). This was a desirable water stress to know the response of both species to extreme water levels under field conditions. Plant developmental morphology stages were delayed, on all studied perennial grasses, more in the drier (2008-2009) than in the wetter (2007-2008) study year. Defoliation did reduce the studied morphological characteristics after plants of all species were defoliated twice in 2007-2008 and 2008-2009. The higher values of most of the components of leaf area production in P. vaginatum than in the other species in the study could help to explain its higher abundance in the rangelands of Argentina. Knowledge of the mechanisms involved in grazing tolerance of P. vaginatum will be useful to: (1) increasing its grazing tolerance through a genetic improvement plan, and (2) implementing management guidelines that increase its plant production under grazing conditions. - Artículo
Acceso Abierto Impacts of shrubs on soil quality in the native Monte rangelands of Southwestern Buenos Aires, Argentina(2023) Ambrosino, Mariela Lis; Torres, Yanina Alejandra; Lucero, Cinthia Tamara; Lorda, Graciela Susana; Ithurrart, Leticia Soledad; Martínez, Juan Manuel; Armando, Lorena Vanesa; Garayalde, Antonio; Busso, Carlos AlbertoShrub cover in semiarid rangelands may induce changes in soil resources and ecosystem functioning. However, it is unknown the real influence that shrub vegetation has on soil quality in rangelands used for livestock purposes. We evaluated the shrub cover effect on 12 chemical and biochemical parameters of soil quality. In a semiarid Monte rangeland of Argentina, 6 paddocks were selected and 10 m transects were placed in a patch with (Sh) and without shrubs (WSh). Then, sites with grasses (Sh-G and WSh-G), bare ground-litter (Sh-BL and WSh-BL), and under shrub cover (Sh-S) were selected. In spring 2017 and 2018, a composite soil sample (0–10 cm in depth) was taken at each site (n = 6). Sh-G and Sh-S sites presented high values of soil organic matter, soil organic nitrogen, particulate organic matter (POM), and cellulase activity (CA); WSh-BL and Sh-BL sites were associated with the lowest contents of these variables. For the rest of the soil quality parameters, the soil sampling sites showed similar values. These results show that woody presence should not be directly linked to soil quality loss. Although we did not detect a shrub effect in all parameters studied, in the context of appropriate grazing management, the presence of plant species of different functional groups has a positive effect on organic matter and N content of soil close to them. Moreover, in these sites, high POM values represent an important reservoir of potentially available nutrients, and promote CA necessary for fresh litter decomposition improving the soil quality of semiarid rangelands. - Artículo
Acceso Abierto Comparative study of electrodeposited copper nanoparticles on different substrates for their use in the reduction of nitrate ions(2023) Zurita, Noelia; García, Silvana G.A comparative analysis of the electrodeposition of copper nanoparticles (CuNPs) was studied on highly oriented pyrolytic graphite (HOPG) and vitreous carbon (VC) substrates from solutions containing different supporting electrolytes (Na₂SO₄ and H₂SO₄). Voltammetric results indicated the presence of a single cathodic process, corresponding to the reduction reaction of Cu²⁺ ions to Cu°, for the solutions studied, using the HOPG substrate. The solution containing Na₂SO₄ as supporting electrolyte was found to be more effective because the copper reduction process occurs at more positive potential values, reaching the highest current density. For the VC substrate, two cathodic processes were evidenced, with the formation of Cu⁺ ions as intermediate species. As in the HOPG substrate, the use of the solution containing Na₂SO₄ showed the better behavior for copper electrodeposition, being the most favored process on VC. This behavior could be explained by considering the existence of structural defects in the VC, which would facilitate Cu nucleation. The nucleation and growth kinetics of CuNPs on HOPG electrodes corresponded predominantly to a model including progressive nucleation on active sites, and diffusion controlled growth, presenting a good correlation with the scanning electron microscopy images. For VC substrates, the kinetics analysis did not yield conclusive results. Different morphological features of Cu deposits were observed on HOPG and VC, presenting the former a larger covered area. The HOPG/CuNPs modified electrodes evidenced an enhancement in the catalytic activity towards the nitrate reduction reaction. - Artículo
Acceso Abierto Electrodeposición de nanopartículas de cobre sobre HOPG: influencia del electrolito soporte(2020) Zurita, Noelia; García, Silvana G.Se estudió la influencia del electrolito soporte en las etapas iniciales de la electrodeposición de cobre sobre grafito pirolítico altamente orientado, mediante técnicas electroquímicas convencionales. Las técnicas de microscopía SEM y AFM se emplearon para la caracterización de los depósitos generados. El proceso de electrocristalización se evaluó a partir de soluciones de CuSO4 con distintos electrolitos soportes: Na2SO4, H2SO4, y la combinación de ambos. Los resultados voltamperométricos indicaron la respuesta típica de un proceso de nucleación y crecimiento controlado por difusión. El mayor valor del coeficiente de difusión se encontró para la solución conteniendo Na2SO4. Las imágenes SEM y AFM revelaron que el mecanismo de nucleación del Cu es de tipo progresivo. La densidad de núcleos formados resultó menor para el electrolito combinado. Se evidenció, en el caso de la solución con Na2SO4, la formación de aglomerados de partículas, mientras que para la solución con H2SO4, se observaron, además, estructuras dendríticas. - Artículo
Acceso Abierto Influence of supporting electrolyte on electrochemical formation of copper nanoparticles and their electrocatalytic properties(2022) Zurita, Noelia; García, Silvana G.Comparative analysis of copper nanoparticles (CuNPs) obtained by electrodeposition on highly oriented pyrolytic graphite (HOPG) substrates from different supporting electrolytes containing sulphate anions, was performed. Voltammetric results indicated that Cu electrodeposition follows a diffusion-controlled nucleation and crystal growth model for three solutions studied (Na2SO4, H2SO4 and Na2SO4+H2SO4). Na2SO4 solution was most effective because the copper reduction occurs at the most positive potential value, reaching the highest current density. Analysis of potentiostatic current transients revealed that the process can be described predominantly by a model involving a 3D-progressive nucleation mechanism, which was corroborated by scanning electron microscopy (SEM) analysis. SEM images showed a high density of hemispherical shaped Cu particles of different sizes (mostly between 80-150 nm), randomly distributed on the HOPG surface for Na2SO4 electrolyte solution. In the presence of H2SO4, the size dispersion decreased, resulting in particles with greater diameters (up to 339 nm). The electrolyte solution with Na2SO4+H2SO4 revealed lower particle density with a considerable crystal size dispersion, where very small crystallites are prevailing. Cyclic voltammetry was used to evaluate qualitatively the catalytic activity of CuNPs deposited from three electrolyte solutions towards the nitrate reduction reaction. An enhanced catalytic effect was obtained when copper particles were prepared from either Na2SO4 or H2SO4 supporting electrolyte. - Artículo
Acceso Abierto Reproductive traits in four spontaneous Pappophorum vaginatum populations in arid Argentina(2021) Entío, L.; Mujuca, M. M.; Busso, Carlos; Torres, Yanina AlejandraArid zones, where native rangelands are common, are essentials for millions of people livelihood. These areas support 50% of the world’s livestock and are where 44% of the world’s food is grown. In rangelands of Central Argentina, Pappophorum vaginatum is basically the unique, warm-season perennial grass species palatable to grazing livestock. Our major objective was to determine variability in reproductive characteristics among four spontaneous, overgrazed populations (i.e., P1, P2, P3, P4) of that species to identify promissory materials for domestication. Studies were conducted during three consecutive growing seasons within the southwestern part of the Phytogeographical Province of the Monte, in southwestern Buenos Aires, Argentina. Measured reproductive characteristics were related to flowering initiation, seed production and natural reseeding potential. Significant differences were found for flowering initiation and natural reseeding potential, but not for viable anthecia per plant among the four populations of P. vaginatum. This species fructified from the beginning to the end of the studied growing seasons with a great anthecia production per plant. The light weight of these anthecia and their awns would favor a great wind dispersal and most likely the establishment of new seedlings of P. vaginatum. This suggests that sexual reproduction might have a relatively greater importance than asexual reproduction (i.e., tillering) in the persistence of the overgrazed P. vaginatum in the plant communities of the studied region. Se-lection of plant materials with a late flowering initiation will allow to extend the forage production of a better quality. The variability among and within populations found on this study support the idea that would be promissory to start selection programs to obtain improved germplasm to reincorporate to grasslands of the south of the Phytogeographical Region of the Monte (Argentina) not only to increase livestock production but to recover and maintain biodiversity. - Artículo
Acceso Abierto Limitaciones del test de tetrazolio para determinar viabilidad de yemas y semillas(2021) Torres, Yanina Alejandra; Ithurrart, Leticia S.; Busso, CarlosLa técnica convencional de tinción conocida como test de tetrazo-lio no es la más apropiada para la determinación de la viabilidad de los tejidos vegetales, sino que debería complementarse con el colorante azul de Evans. - Comunicacion
Acceso Abierto Plant Species and Defoliation Efects on Soil Nitrogen Mineralization in a Semiarid Rangeland of Argentina(2021) Ambrosino, Mariela Lis; Martínez, Juan Manue; Busso, Carlos; Minoldo, Gabriela; Torres, Yanina Alejandra; Ithurrart, Leticia Soledad; Cardillo, Daniela SolangeThe objective of this study was to evaluate the efects of moderate defoliation and grass species on soil nitrogen (N) mineralization in a semiarid grassland of northeastern Patagonia, Argentina. Studied species were Poa ligularis and Nassella tenuis (desirable/preferred by cattle) and Amelichloa ambigua (undesirable/non preferred). Two defoliations were made to a 5 cm stubble height during the growing season. Hypotheses were that (1) net N mineralization and N availability in the soil are increased by a moderate defoliation and greater species forage quality, and (2) potential N mineralization is higher in the soil beneath the desirable than undesirable species. In 2013 and 2014, in situ net N mineralization was estimated using the tube incubation technique under feld conditions. Potential N mineralization was estimated by long-term laboratory incubations. Defoliation treatments did not afect the soil inorganic N dynamics. The soil under A. ambigua showed a greater in situ net N mineralization than other species, but only in 2013. Poa ligularis presented the highest initial inorganic N and potentially mineralizable N values. However, the opposite was recorded in this specie for the mineralization constant rate. These results demonstrated that moderate defoliations did not afect soil N availability, and presence of the desirable perennial grasses increased the potential N mineralization pool. Sustainable management practices that promote the persistence of these species in plant community are important to maintain soil fertility on semiarid grasslands. - Artículo
Acceso Abierto Three-Dimensional Reconstruction of Halamphora coffeaeformis Frustule from Scanning Electron Micrographs(2020) Navarro, Francisco Ezequiel; Popovich, Cecilia; Sánchez, Miguel; Costilla, Ignacio; Gutierrez Ayesta, Cecilia; Leonardi, PatriciaThe diatom Halamphora coffeaeformis represents an alternative feedstock of oils for the biodiesel production. In addition, its siliceous cell wall (named frustule) presents possible industrial applications that have not been reported in the literature yet. Thus, the main objective of this study was to perform a three-dimensional reconstruction of H. coffeaeformis´ frustule from scanning electron micrographs, in order to have a study model. For this, the biomass of the species growing in a photobioreactor was harvested and treated as follows: a) some samples were dehydrated and subjected to a critical point; and b) other samples were treated with H2O2 in order to analyse the frustule´s ornamental pattern. All samples were metallized with gold, using an Argon plasma metal evaporator (Pelco model3) and they were observed with a LEO Scanning Electron Microscope, model EVO 40 XVP 2004. The frustules were elliptical to lanceolate with protracted ends. Valves presented convex dorsal margin and straight ventral margin. Dorsal striae were biseriate and radiate; ventral striae were short, uniseriate, radiate at the center and convergent at the ends of the valves. The raphe was straight and close to the ventral margin. The micrographs were analysed and separated into layers with the Adobe Photoshop CS6 software. The layers were vectorised with the Inkscape software and loaded and assembled in the Tinkercad software. The final aspects of the digital model were moulded on the page https://stephaneginier.com/sculptgl/. Finally, 3D printing was done with a CoLiDoTM 3.0 L printer, obtaining a three-dimensional replica representative of the H. coffeaeformis´ morphology . This replica will serve as a model for studies of its frustules related to nanotechnology and /or catalyst support applications. - Artículo
Acceso Abierto Soil microbial structure and activity in a semiarid rangeland of Patagonia, Argentina: Plant species and defoliation effects(2021) Ambrosino, Mariela Lis; Montecchia, Marcela Susana; Torres, Yanina Alejandra; Ithurrart, Leticia Soledad; Lucero, Cinthia Tamara; Busso, Carlos AlbertoNatural grasslands are an important renewable resource for livestock production. Grazing in these areas alters the plant community composition, litter quality, and soil microbial structure and activity. Three cool-season species were studied in a semiarid rangeland area of Argentina: Poa ligularis and Nassella tenuis (desirable/ preferred for livestock) and Amelichloa ambigua (undesirable/non preferred). The objective was to analyze the effect of moderate defoliation and plant species on the structure and activity of soil microbial communities associated with their roots. In winter 2012, soil samples (0–10 cm) were taken underneath marked plant canopies of the three species (n = 8). Immediately thereafter, half of the plants (n = 4) were defoliated (5 cm stubble height) and the other half remained undefoliated (controls). The defoliation treatment was conducted again in the spring. Soil samples were taken 30 days after each defoliation event. The study was repeated in 2013, using a different plant set. Bacterial community structure and soil microbial activity were analyzed using PCR-DGGE analysis and basal soil respiration, respectively. Moderate and early defoliations allowed compensatory growth in the defoliated plants. Variations in the soil genetic profiles of A. ambigua suggest a higher dependence on its rhizospheric bacterial communities. Defoliation treatments did not substantially affect basal soil respiration but showed strong links between desirable species and soil microbial activity. Sustainable management practices that promote the persistence of these species are important for the development of microbial communities that respond quickly to stress conditions, favoring decomposition processes that maintain soil fertility in semiarid grasslands. - Artículo
Acceso Abierto Relevance of silica surface morphology in ampyra adsorption: insights from quantum chemical calculations(2019) Noseda Grau, Emilia; Román, G.; Díaz Compañy, Andrés Carlos Daniel; Brizuela, G.; Juan, A.; Simonetti, S.Theoretical calculations are performed using the Vienna Ab-initio simulation package (VASP) to understand the mechanisms that control the adsorption of Ampyra drug on the different crystallographic planes of bcristobalite: the hydroxylated (111) and (100) surfaces. The Ampyra-silica interaction is most favored on the (100) surface where the entire ring of the molecule interacts with the surface while on the (111) face, lesser exchange and fewer non-polar atoms are involved. Calculations show that the interactions mainly occur at the interface between the Ampyra and the closest silanol groups, according to the formation of the Hbonding interactions. The results indicate that the H-bonds have an important influence on the adsorption of the Ampyra. In consequence, adsorption on the (111) surface is observed to a lesser extent than on the (100) surface according the smaller hydroxyl density. - Artículo
Acceso Abierto A first principles study of pristine and Al doped activated carbon interacting with 5-Fluorouracil anticancer drugs(2018) Román, G.; Noseda Grau, Emilia; Díaz Compañy, Andrés Carlos Daniel; Brizuela, G.; Juan, Alfredo; Simonetti, SandraThe adsorption of the 5-Fluorouracil (5-FU) molecule on the pristine and Al-doped activated carbon (AC) was investigated by using the Vienna Ab-initio Simulation Package. It is found that the 5-FU molecule is only weakly adsorbed on the pristine AC with high adsorption energy and large surface distance. The adsorption of the 5-FU molecule on pristine AC is highly disfavored. In contrast, the molecule shows strong interactions with the Al-doped AC confirmed by the lesser adsorption energy, the charge transfers on the Al-modified zone and the significant changes in the DOS at the Fermi level. The results of our study suggest that the Al dopant increases the adsorption capacity of AC enhancing its interactions with polar atoms of the adsorbate, hence improving its adsorption properties. - Artículo
Acceso Abierto Surface modification vs sorption strength: study of nedaplatin drug supported on silica(2019) Noseda Grau, Emilia; Román, G.; Díaz Compañy, Andrés Carlos Daniel; Brizuela, G.; Juan, Alfredo; Simonetti, SandraThe interaction of nedaplatin drug with modified SiO2 (0 0 1) surfaces has been investigated within the framework of Density Functional Theory. Nedaplatin molecule is adsorbed spontaneously onto silica surfaces. Silica surface prevents drug degradation allowing the chemical attachment without any impact on the drug structure itself. The nedaplatin sorption is mainly governed by H-bonding interactions on hydrated and trimethylsilanefunctionalized surfaces, while the drug is major stabilized by NeO, OeO interactions and H partial dissociation on dehydrated silica. The differences on the adsorption strength could be used in future studies to control the drug release, developing delivery silica systems according therapy requirements. - Artículo
Acceso Abierto Adsorption and removal of phenoxy acetic herbicides from water by using commercial activated carbons: experimental and computational studies(2018) Pila, Matías; Simonetti, Sandra; Álvarez-Torrellas, Silvia; García Rodríguez, Juan; Ruiz, Danila; Díaz Compañy, Andrés Carlos Daniel; Juan, Alfredo; Allegretti, Patricia E.In this study, commercial activated carbons (GAB and CBP) were successfully used for the removal of two phenoxy acetic class-herbicides, 4-chloro-2-methyl phenoxy acetic acid and 2.4-dichlorophenoxy acetic acid (MCPA and 2.4-D) from aqueous solution. The adsorbent materials were characterized, and their equilibrium adsorption capacity was evaluated. The results suggest that the microporous properties of GAB activated carbon enhanced the adsorption capacity, in comparison to CBP carbon. Thus, the increasing in the ionic strength favored the adsorption removal of both pesticides, indicating that electrostatic interactions between the pollutant and the adsorbate surface are governing the adsorption mechanism, but increasing pH values decreased adsorption capacity. Experimental data for equilibrium was analyzed by two models: Langmuir and Freundlich. Finally, computational simulation studies were used to explore both the geometry and energy of the pesticides adsorption. - Artículo
Acceso Abierto 5-fluorouracil adsorption on hydrated silica: density functional theory based-study(2017) Díaz Compañy, Andrés Carlos Daniel; Juan, Alfredo; Brizuela, G.; Simonetti, SandraHydrated SiO2(111) has been projected as a competent support of an anticancer drug, 5-fluorouracil (5-FU). Theoretical calculations using the Vienna Ab-initio Simulation Package (VASP) were performed to study the drug-silica interactions that control the adsorption of 5-fluorouracil (5-FU) on an hydrated SiO2(111) surface. Only dispersive interactions are presented during the drug adsorption on the hydrophobic surface while cooperation exists between directional H-bonds and dispersion forces on hydrated silica. H-bonds become dominant for the hydrophilic surface driven interactions with important energetic consequences on adsorption. The density of states slightly shifted towards lower energy values showing a stabilization of the electron states of the 5-FU molecule on hydrated silica, and the electronic charge transfer mainly happens on the interface between polar groups of 5-FU and the nearest silanol groups, in agreement with the formation of the H-bonding interactions. The results reveal the remarkable influence of H-bonds in the adsorption mechanism on hydrated silica. - Artículo
Acceso Abierto Adequate management of defoliation post-fire would not affect the metabolic activity of axillary buds on grasses(2019) lthurrart, Leticia S.; Busso, Carlos A.; Torres, Yanina Alejandra; Giorgetti, Hugo D.; Rodriguez, Gustavo D.; Ambrosino, Mariela L.Controlled burning is often used to improve plant structure on rangelands adapted to fire. However, possible damage resulting from post-fire grazing to reappearing desirable plant species may be a serious issue hindering usage of this method. Axillary buds are essential for the re-establishment of the photosynthetic leaf area. We studied if post-burn defoliation affects the number of axillary buds and/or their metabolic activity in Poa ligularis, Nassella tenuis (both desirable plant species) and Amelichloa ambigua (undesirable plant species). We found that the treatments limited neither bud production nor their metabolic activity. The greatest number of total and viable buds in the studied plant species was recorded at the vegetative stage. Poa ligularis had the lowest bud number per tiller but the greatest per plant. Our results thus indicate that moderate defoliation after controlled burning does not affect the survival and productivity of the desirable species. - Artículo
Acceso Abierto Photoactive thin films of terphenylene-based amorphous polymers: Synthesis, electrooptical properties, and role of photoquenching and inner filter effects in the chemosensing of nitroaromatics(2019) Garay, Raúl O.; Del Rosso, Pablo G.; Romagnoli, Maria J.; Almassio, Marcela Fabiana; Schvval, Ana BelénNew photoactive segmented conjugated polymers with terphenylene chromophores were synthesized, and the chemosensing abilities to detect nitroaromatics compounds (NACs) of the polymeric thin films were evaluated in aqueous media. The thin films are strongly fluorescent, amorphous with no aggregation of the chromophores in the solid state and sensitive towards NACs in water. Though true quenching occurring after diffusion of the NACs into the amorphous films contributes to the total response of these polymer films, quenching efficiencies of nitroaromatics are strongly influenced by additional inner filter effect contributions that could be used to increase the film response. Thus, to maximize the response of these polymers, it is convenient to use the shortest feasible λexc for trinitritoluene (TNT) and the longest feasible λexc for picric acid (PA). In the micromolar concentration region, the highly absorbing PA frequently has a stronger response than TNT due to the inner filter effects (IFE) contributions. However, we observed that the properties of the material, such as exciton mobility or quencher-polymer compatibilities, become more relevant to define the quenching efficiency at the nanomolar range; though the electrondonor capabilities of the chromophores have no bearing on quenching efficiency. So, the tuning of morphology and photophysical properties of the polymer by structural design should be complemented with a rational selection of experimental conditions, e.g., λexc, in order to enhance the response towards the NAC of interest. - Artículo
Acceso Abierto Plant litter decomposition in a semiarid rangeland of Argentina: species and defoliation effects(2019) Ambrosino, Mariela L.; Busso, Carlos; Torres, Yanina Alejandra; Ithurrart, Leticia S.; Martínez, Juan M.; Minoldo, Gabriela; Cardillo, Daniela S.; Palomo, Iris R.Plant litter decomposition is critical for terrestrial ecosystem productivity. Poa ligularis Nees ex Steud and Nassella tenuis (Phil.) Barkworth are native, desirable perennial grasses in central Argentina’s rangelands. Amelichloa ambigua (Speg.)Arriaga&Barkworth is only consumed when a better forage is unavailable. Litter traps were used to collect aboveground litter during two years. In March 2012, six bags, each one containing either leaf blade (three bags, one per species) or root litter (three bags, one per species) of the three species were located belowthe canopy of each replicate plant of the studied species (hereafter referred to as ‘location’). Blade litter bags were located on the soil surface, and root litter bags buried at 10 cm soil depth. This allowed evaluation of the effects of defoliation, the different species canopies and the microbial community activity around their roots on decomposition of above- and belowground litter. For each species, twenty plants were either defoliated twice (5 cm stubble height) or remained undefoliated during the growing season. Litter bagswere collected after 2, 7, 13 and 24months incubation. The studywas repeated in 2013, with additional bagswere placed forNcontent determination on leaf blade and root litters. Aboveground litter productionwas highest in P. ligularis; however, no differences were observed among species when the effect of plant size was eliminated. Aboveground litter of desirable species had higher N content and decomposed faster than that of A. ambigua. The opposite was recorded for root litter. Defoliation had no effect on litter decomposition, but location effects were detected after one year of incubation. Desirable perennial grasses promoted organicmatter loss fromlitter, a key factor in increasing soil fertility in this semiarid ecosystem. - Artículo
Acceso Abierto Species identity, richness and developmental stage of morphology affect enzymatic activity of the soil microorganisms in arid Patagonia, Argentina(MedCrave, 2019) Cardillo, Daniela S.; Busso, Carlos; Ambrosino, Mariela L.; Torres, Yanina Alejandra; Ithurrart, Leticia S.; Palomo, RosanaMicrobial communities are a key for terrestrial ecosystem functioning. However, their responses to changes in plant species identity and richness, and stages of developmental morphology have been rarely investigated. The objective of this study was to evaluate the impact of the identity, richness and stage of developmental morphology of plant species on soil microbial communities throughout the enzymatic activity of the dehydrogenase. Studies were conducted under wild, field conditions, and on field experimental plots having different species richness. Treatments included a control (intraspecific monocultures) or combinations of 2, 4, or 6 species pertaining to different functional groups (i.e., perennial either grasses or herbaceous dicots or shrubs). The grass Nassella tenuis and the shrub Larrea divaricata showed a lower (p<0.05) activity of the dehydrogenase than most of the other studied species under wild, field conditions. The enzymatic activity of the dehydrogenase was either similar or greater (p<0.05; e.g., Amelichloa ambigua, L. divaricata), but not lower, as species richness increased in the reproductive stage of developmental morphology. Finally, the dehydrogenase activity was in general greater (p<0.05) at the reproductive (late spring) than vegetative (late fall) stage of developmental morphology in all studied species. These results indicate that species identity, richness and stage of developmental morphology might be important determinants of the degree of microbial activity in the soil.