Shrub encroachment is frequent in grazing lands in the Chaco region, Argentina. Fire is used by cattlemen to reduce the dominance of the shrub stands, improve forage standing biomass and quality, and enhance grazing accessibility. In this research, we assessed the combined effect of roller chopping þ fire on the plant canopy of three native shrub species, Acacia gilliessi, Celtis ehrenbergiana, and Schinus bumelioides. We used a randomized design, with three factors, year, burn dates, and fine fuel load. Before the burn, the area received a roller-chopping treatment. Canopy volume reduction was assessed using, DifV ¼ −1*(V i − V a ) and DifS ¼ −1*(S i − S a ), respectively, where V ¼ plant volume and S ¼ sprout number. Suffixes i and a represent measurements taken before the roller-chopping treatment and one growth season after the fire, respectively. Fire intensity, headfire residence time, woody residues, and initial plant volume were evaluated as covariates. Results indicate a negative fire effect on canopy volume and sprouting. A. gilliesi was more susceptible to fire than the other two species. High fine fuel load and high fire intensity generated a severe effect on sprout number. The same trend was observed for coarse fuels. The canopy volume reduction was greater in A. gilliesi than the other species, reaffirming its high susceptibility to fire. Head fires were faster in 2009 than in 2008 and in the late than in the early burn dates. These results suggest that mechanical þ fire treatments can be useful management tools for controlling shrub encroachment in the western Chaco.
BACKGROUND Calcium is a preservative and firming agent largely used in the table olive industry. Foliar applications of calcium (as calcium chloride, CaCl2) before harvest have been proposed in other fruits to increase firmness and reduce physiological disorders or internal damage. However, there is still a shortage of information regarding the source, the concentration, the number, and the period of calcium application onto the canopy to get an effective response of olive quality. In this study, we aimed to investigate the effect of two concentrations of CaCl2 foliar treatments (0.5% and 1.0%), applied at different stages of fruit development (at the end of fruit set, end of pit hardening, and prior to harvesting), on olive quality for two varieties (‘Manzanilla de Sevilla’ and ‘Ascolanta tenera’), cultivated in two different geographical areas (Spain and Italy respectively). RESULTS The calcium concentrations applied enhanced the fruit calcium content and decreased sodium and potassium. They also improved the mechanical properties without modifying fruit morphology or cuticle thickness; nor did they cause phytotoxicity. Foliar treatments increased the oil content in the pulp (dry weight basis) and the amount of hydroxytyrosol, tyrosol, and oleuropein, among other phenols. CONCLUSION Calcium foliar applications during fruit development effectively increase olive quality. © 2020 Society of Chemical Industry
RESUMEN.El rolado selectivo de baja de intensidad (RBI) es una tecnología para habilitar sistemas silvopastoriles de bajo impacto en el Chaco Semiárido. A diferencia de otras formas de habilitar las tierras con fines ganaderos (e.g., desmonte total, rolados intensivos), el RBI conserva bien el suelo y la mayor parte de la vegetación nativa, sin resignar producción. Este estudio aborda a escala local la influencia del RBI sin siembra de pasturas exóticas sobre un ensamble de reptiles de un bosque nativo del Chaco Semiárido, donde el bosque con RBI mantiene conectividad con vastas superficies de vegetación nativa.Los resultados muestran que: a) la diversidad alfa de reptiles no disminuyó en el bosque con RBI debido aque la estructura vertical de la vegetación no fue degradada, y b) el ensamble de reptiles del bosque con RBI fue muy parecido al del bosque testigo dada la gran similitud estructural entre estos hábitats. Los resultados demuestran que la cobertura arbórea y de hojarasca son variables importantes de estructura de la vegetación que influirían sobre la distribución por hábitat de las especies de reptiles, relacionadas con un gradiente ambiental de luz solar. Este estudio sugiere que localmente, el RBI sin siembra de pasturas exóticas tiene potencial para conservar de manera adecuada la diversidad y la composición de los ensambles de reptiles de bosques nativos del Chaco Semiárido.[Palabras clave: diversidad alfa, similitud de ensambles, estructura de la vegetación, similitud estructural de hábitats, sistemas silvopastoriles] ABSTRACT. Low intensity roller chopping (RBI) on forests of Semiarid Chaco: influence on diversity and composition of a reptile assemblage. Low intensity roller chopping (RBI) is a technology that enables low impact silvopastoral systems in the Semiarid Chaco. In contrast to other systems, RBI preserves the soil and most of the native vegetation without sacrificing production. This study addresses the local impact of RBI without implanted exotic pastures on a reptile assemblage in a Semiarid Chaco forest, where the forest with RBI maintains connectivity with large areas of native vegetation. The results show that: a) the alpha diversity of reptiles did not decrease in the forest with RBI, associated with the non-degradation of the vegetation´s vertical structure, and b) reptile assemblages were highly similar between the forest with RBI and the control, due to a high structural similarity between habitats. The results show that tree and litter cover are important variables that influence the distribution of reptile species in the habitats, related to the sunlight gradient. At a local scale, this study suggests that RBI without implanted exotic pastures has the potential to adequately maintain the diversity and composition of reptile assemblages in Semiarid Chaco forests.
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