The spread of invasive alien species over natural environments has become one of the most serious threats to biodiversity and the functioning of ecosystems worldwide. Understanding the population attributes that allow a given species to become invasive is crucial for improving prevention and control interventions. Pampas grasslands are particularly sensitive to the invasion of exotic woody plants. In particular, the Ventania Mountains undergo the advance of alien woody plants; among which the Aleppo pine (Pinus halepensis) stands out due to the extension of the area it covers and the magnitude of the ecological changes associated to its presence. Using a model that describes the population dynamics of the species in the area, we evaluated the expected behavior of the population under different environmental conditions and different management scenarios. When the effect of stochastic fires was simulated, the growth rate was greater than 1 for all the frequencies considered, peaking under fires every nine years, on average. When evaluating the effect of periodic mechanical control of the adult population, the reduction in growth rate was insufficient, except for cutting intensities that significantly exceeded the current operational capacity of the area. Under prescribed fire scenarios, on the other hand, burning frequencies greater than seven years resulted in population reductions. The results highlight the importance of fire in regulating the population of P. halepensis in the Ventania Mountains, with contrasting effects depending on the frequency with which it occurs, which allows considering it as an effective environmental management option for the control of the species.
Grassland , Introduced Species , Pinus , Population Dynamics , Pinus/growth & development , Argentina , Biodiversity , Ecosystem , Fires
Relations among polycyclic aromatic hydrocarbons (PAHs), biomarkers of oxidative stress (lipid peroxidation, glutathione, and glutathione S-transferase activity), and the possible influence of environmental factors (temperature, pH, and salinity) were assessed in situ for specimens of Ramnogaster arcuata, a native estuarine fish. PAH levels found in the muscular tissue of R. arcuata ranged from 0.7 to 293.4 ng g-1 wet weight with petrogenic and pyrolytic inputs. Lipid peroxidation in the liver showed positive correlations (P < 0.05) with total PAHs (r = 0.66), 3-ring (r = 0.66) and 4-ring PAHs (r = 0.52) and glutathione in muscle (r = 0.58). Significant positive correlations (P < 0.05) were also evidenced between muscular glutathione with total (r = 0.62) and 3-ring PAHs (r = 0.75). Hepatic glutathione S-transferase negatively correlated with 4-ring PAHs (r = -0.58). These correlations suggest that lipid peroxidation and muscular glutathione could be good biomarkers for complex mixtures of PAHs, and hepatic glutathione S-transferase could be a suitable biomarker for 4-ring PAHs. Furthermore, significant correlations (P < 0.05) of environmental factors with PAH levels and biomarkers were observed, especially pH with 3-ring PAHs (r = -0.65), lipid peroxidation (r = -0.6), glutathione in the liver (r = -0.73) and muscle (r = -0.75); and temperature with 2-ring PAHs (r = -0.75) and glutathione in muscle (r = 0.51). The data suggest an influence of physicochemical parameters which could be driving a shift in PAH toxicity in R. arcuata. These results are essential for an integrated understanding of ecotoxicology and could help to predict environmental effects in present and future scenarios of ocean warming and acidification.
Polycyclic Aromatic Hydrocarbons , Water Pollutants, Chemical , Animals , Polycyclic Aromatic Hydrocarbons/analysis , Environmental Monitoring/methods , Fishes/metabolism , Oxidative Stress , Biomarkers/metabolism , Glutathione/pharmacology , Glutathione Transferase/metabolism , Water Pollutants, Chemical/analysis
ABSTRACT The driving forces behind many soil processes are microorganisms and they are able to respond immediately to environmental changes. The soil microbial community impacts on many soil properties. More than one-third of the terrestrial ecosystems are semiarid. However, a limited number of studies have been conducted to characterize soil fungal communities in semiarid grasslands, in particular those of agricultural fields. The aim of this study was to explore changes in the diversity and structure of soil fungal communities in semiarid grasslands, after different doses of glyphosate were applied under field conditions. Changes in soil fungal communities were examined using different approaches including culturing, calcofluor white stain and denaturing gradient gel electrophoresis (DGGE). The different approaches complement each other, revealing different aspects of the effect of glyphosate on soil fungal communities. We demonstrated a negative effect of glyphosate on soil fungal biomass at high doses and an early and transitory stimulatory effect on soil fungal biomass. We also found a negative effect of glyphosate on the species richness of cultivable fungi and changes in the molecular structure of soil fungal communities after double doses or long-term glyphosate application. In summary, our findings demonstrate an overall negative effect of glyphosate on soil fungal communities.
RESUMEN Los microorganismos del suelo son los responsables de llevar a cabo la mayoría de los procesos biológicos que ocurren en el suelo, y son capaces de reaccionar ante el estrés ambiental. Más de un tercio de los ecosistemas terrestres son semiáridos. Sin embargo, son escasos los estudios realizados para caracterizar las comunidades fúngicas en suelos agrícolas en ecosistemas semiáridos. El objetivo del presente trabajo fue estudiar los cambios que se producen en la biomasa, la diversidad y la estructura de las comunidades fúngicas del suelo, luego de la aplicación de distintas dosis de glifosato en condiciones de campo. Se emplearon diferentes técnicas incluidas el cultivo, la tinción directa con blanco de calcoflúor y PCR acoplada a electroforesis en geles de gradiente desnaturalizante (DGGE). Las distintas metodologías empleadas se complementan entre sí al detectar cada una distintos aspectos del efecto del glifosato en las comunidades fúngicas del suelo. Se encontró que el glifosato produce un efecto negativo sobre la biomasa fúngica, también se encontró un efecto transitorio estimulante inmediatamente posterior a la aplicación del herbicida. Además, se vio un efecto negativo sobre la riqueza de hongos cultivables, así como también cambios en la estructura molecular de las comunidades luego de aplicaciones repetidas. En conclusión, se demostró un efecto negativo generalizado sobre las comunidades fúngicas del suelo.
Microbiota , Mycobiome , Soil , Soil Microbiology , Fungi , Glycine/analogs & derivatives
The driving forces behind many soil processes are microorganisms and they are able to respond immediately to environmental changes. The soil microbial community impacts on many soil properties. More than one-third of the terrestrial ecosystems are semiarid. However, a limited number of studies have been conducted to characterize soil fungal communities in semiarid grasslands, in particular those of agricultural fields. The aim of this study was to explore changes in the diversity and structure of soil fungal communities in semiarid grasslands, after different doses of glyphosate were applied under field conditions. Changes in soil fungal communities were examined using different approaches including culturing, calcofluor white stain and denaturing gradient gel electrophoresis (DGGE). The different approaches complement each other, revealing different aspects of the effect of glyphosate on soil fungal communities. We demonstrated a negative effect of glyphosate on soil fungal biomass at high doses and an early and transitory stimulatory effect on soil fungal biomass. We also found a negative effect of glyphosate on the species richness of cultivable fungi and changes in the molecular structure of soil fungal communities after double doses or long-term glyphosate application. In summary, our findings demonstrate an overall negative effect of glyphosate on soil fungal communities.
Microbiota , Mycobiome , Fungi , Glycine/analogs & derivatives , Soil , Soil Microbiology , Glyphosate
Plants with animal-dispersed fruits seem to overcome the barriers that limit their spread into new habitats more easily than other invasive plants and, at the same time, they pose special difficulties for containment, control or eradication. The effects of animals on plant propagules can be very diverse, with positive, neutral or negative consequences for germination and recruitment. Moreover, the environmental conditions where the seeds are deposited and where the post-dispersal processes take place can be crucial for their fate. Prunus mahaleb is a fleshy-fruited tree invading natural grasslands in the Argentine Pampas. In this study, we analyzed the importance of pulp removal, endocarp scarification and the effects of vectors on its germination response, by means of germination experiments both in the laboratory and under semi-natural conditions. Our laboratory results demonstrated that endocarp scarification enhances germination and suggests that vestiges of pulp on the stones have inhibitory effects. Frugivores exert a variety of effects on germination responses and this variation can be explained by their differing influence on pulp removal and endocarp scarification. Most frugivores produced a positive effect on germination under laboratory conditions, in comparison to intact fruits and hand-peeled stones. We observed different degrees of pulp removal from the surface of the stones by the dispersers which was directly correlated to the germination response. On the other hand, all the treatments showed high germination responses under semi-natural conditions suggesting that post-dispersal processes, like seed burial, and the exposure to natural conditions might exert a positive effect on germination response, attenuating the plant's dependence on the dispersers' gut treatment. Our results highlight the need to consider the whole seed dispersal process and the value of combining laboratory and field tests.
Fruit/chemistry , Germination/physiology , Prunus/physiology , Seed Dispersal/physiology , Trees/physiology , Animals , Feeding Behavior , Grassland
Soil microorganisms are vital for ecosystem functioning because of the role they play in soil nutrient cycling. Agricultural practices and the intensification of land use have a negative effect on microbial activities and fungal biomass has been widely used as an indicator of soil health. The aim of this study was to analyze fungal biomass in soils from southwestern Buenos Aires province using direct fluorescent staining and to contribute to its use as an indicator of environmental changes in the ecosystem as well as to define its sensitivity to weather conditions. Soil samples were collected during two consecutive years. Soil smears were prepared and stained with two different concentrations of calcofluor, and the fungal biomass was estimated under an epifluorescence microscope. Soil fungal biomass varied between 2.23 and 26.89µg fungal C/g soil, being these values in the range expected for the studied soil type. The fungal biomass was positively related to temperature and precipitations. The methodology used was reliable, standardized and sensitive to weather conditions. The results of this study contribute information to evaluate fungal biomass in different soil types and support its use as an indicator of soil health for analyzing the impact of different agricultural practices.
Biomass , Fungi/isolation & purification , Microscopy, Fluorescence/methods , Mycology/methods , Soil Microbiology , Staining and Labeling/methods , Agriculture/methods , Argentina , Benzenesulfonates , Dose-Response Relationship, Drug , Fluorescent Dyes , Fungi/ultrastructure , Hyphae/ultrastructure , Meteorological Concepts
Los microorganismos del suelo son vitales para el correcto funcionamiento de los ecosistemas, principalmente por su papel en el ciclado de nutrientes. La intensificación del uso del suelo y las prácticas agrícolas alteran negativamente la actividad microbiana. La biomasa fúngica es uno de los parámetros más utilizados para estudiar el impacto de las actividades agrícolas en la estructura y el funcionamiento del suelo. El objetivo del presente trabajo fue estimar la biomasa fúngica en un suelo del sudoeste bonaerense con el fin de obtener valores de referencia que permitan usar este parámetro como un indicador de cambios en el ecosistema y, por otro lado, demostrar que la metodología empleada es sensible a las variaciones en las condiciones climáticas. Se colectaron muestras de suelos durante 2 años consecutivos. Se prepararon frotis de suelo y se tiñeron con soluciones de distintas concentraciones de blanco de calcoflúor y luego se estimó la biomasa fúngica observando los frotis con microscopio de epifluorescencia. Los valores de biomasa fúngica estimados variaron entre 2,23 y 26,89 μg Cfúngico/g de suelo y estuvieron dentro del rango esperable para el tipo de suelo estudiado. La biomasa fúngica mostró una relación positiva con la temperatura y las precipitaciones. La metodología empleada resultó ser confiable, repetible y sensible a cambios en las condiciones climáticas. Los resultados podrían usarse como valores de referencia para estudiar la biomasa fúngica de suelos bajo distintas condiciones y emplearse como indicadores del impacto de las distintas prácticas agrícolas sobre el ecosistema.
Soil microorganisms are vital for ecosystem functioning because of the role they play in soil nutrient cycling. Agricultural practices and the intensification of land use have a negative effect on microbial activities and fungal biomass has been widely used as an indicator of soil health. The aim of this study was to analyze fungal biomass in soils from southwestern Buenos Aires province using direct fluorescent staining and to contribute to its use as an indicator of environmental changes in the ecosystem as well as to define its sensitivity to weather conditions. Soil samples were collected during two consecutive years. Soil smears were prepared and stained with two different concentrations of calcofluor, and the fungal biomass was estimated under an epifluorescence microscope. Soil fungal biomass varied between 2.23 and 26.89 μg fungal C/g soil, being these values in the range expected for the studied soil type. The fungal biomass was positively related to temperature and precipitations. The methodology used was reliable, standardized and sensitive to weather conditions. The results of this study contribute information to evaluate fungal biomass in different soil types and support its use as an indicator of soil health for analyzing the impact of different agricultural practices.
Soil Analysis , Mycobiome , Indicators and Reagents/analysis , Reference Values , Soil/parasitology , Land Use , Ecosystem , Biomass , Microscopy, Fluorescence/methods
