Current status of bird pest species in agroecosystems of Buenos Aires province, central Argentina

Codesido, M., Bilenca, D

Habitat use by armadillos in agroecosystems of central Argentina: does plot identity matter?

In agroecosystems, the use of cultivated plots by mammals depends on habitat structure as well as on the degree of species specialization. In the Pampas of Argentina, during the last 2-3 decades, there has been a continuing expansion of cropland. The aim of this study was to analyze how the identity and characteristics of agricultural plots may have affected the activity of 2 species of armadillos (Chaetophractus villosus and Dasypus hybridus) in a rural landscape. We carried out 4 sampling sessions between December 2011 and June 2013, surveying 175 plots during spring-summer and 194 during fall at 25 different sites in the Pampas of Buenos Aires province, Argentina. In each plot, we surveyed for signs (burrows and holes) along a 600×6 m transect in order to assess armadillo activity and measured 4 habitat structural variables. As expected, there were structural differences between types of agricultural plots. Across all plots, a total of 6,654 armadillo signs were found (C. villosus = 5,009, D. hybridus = 1,645). Generalized linear mixed models revealed that during both seasons, the type of plot explained much of the variation in armadillo activity, except during spring-summer for D. hybridus. C. villosus had higher use of plots with a longer history of non-tillage (e.g., soybean), while there was more evidence of D. hybridus activity in plots with less human intervention (e.g., grasslands), especially during fall. Overall, D. hybridus and C. villosus were more sensitive to the particular structural features of plots rather than to the kind of land use practiced (crop field or rangeland). These results have important implications for future management decisions in the Pampas region because during the last decades, farming of soybeans has expanded at the expense of grasslands, and this change appears to have differentially affected these 2 species of armadillos.Centro de Estudios Parasitológicos y de VectoresFacultad de Ciencias Naturales y Muse

Habitat use by armadillos in agroecosystems of central Argentina: does plot identity matter?

In agroecosystems, the use of cultivated plots by mammals depends on habitat structure as well as on the degree of species specialization. In the Pampas of Argentina, during the last 2-3 decades, there has been a continuing expansion of cropland. The aim of this study was to analyze how the identity and characteristics of agricultural plots may have affected the activity of 2 species of armadillos (Chaetophractus villosus and Dasypus hybridus) in a rural landscape. We carried out 4 sampling sessions between December 2011 and June 2013, surveying 175 plots during spring-summer and 194 during fall at 25 different sites in the Pampas of Buenos Aires province, Argentina. In each plot, we surveyed for signs (burrows and holes) along a 600×6 m transect in order to assess armadillo activity and measured 4 habitat structural variables. As expected, there were structural differences between types of agricultural plots. Across all plots, a total of 6,654 armadillo signs were found (C. villosus = 5,009, D. hybridus = 1,645). Generalized linear mixed models revealed that during both seasons, the type of plot explained much of the variation in armadillo activity, except during spring-summer for D. hybridus. C. villosus had higher use of plots with a longer history of non-tillage (e.g., soybean), while there was more evidence of D. hybridus activity in plots with less human intervention (e.g., grasslands), especially during fall. Overall, D. hybridus and C. villosus were more sensitive to the particular structural features of plots rather than to the kind of land use practiced (crop field or rangeland). These results have important implications for future management decisions in the Pampas region because during the last decades, farming of soybeans has expanded at the expense of grasslands, and this change appears to have differentially affected these 2 species of armadillos.Centro de Estudios Parasitológicos y de VectoresFacultad de Ciencias Naturales y Muse

InP based lasers and optical amplifiers with wire-/dot-like active regions

Long wavelength lasers and semiconductor optical amplifiers based on InAs quantum wire-/dot-like active regions were developed on InP substrates dedicated to cover the extended telecommunication wavelength range between 1.4 and 1.65 mu m. In a brief overview different technological approaches will be discussed, while in the main part the current status and recent results of quantum-dash lasers are reported. This includes topics like dash formation and material growth, device performance of lasers and optical amplifiers, static and dynamic properties and fundamental material and device modelin

Floristic and vegetation structure of a grassland plant community on shallow basalt in southern Brazil

Few studies have adequately described the floristic and structural features of natural grasslands associated with shallow basalt soils in southern Brazil. This study was carried out on natural grazing land used for livestock production in the municipality of Santana do Livramento, in the Campanha region of the state of Rio Grande do Sul, Brazil. The aim of the study was to describe the floristic and structural diversity of the area. The floristic list obtained comprises 229 plant taxa from 40 botanical families, with a predominance of the families Poaceae (62), Asteraceae (28), Fabaceae (16) and Cyperaceae (12). The estimated diversity and evenness in the community were 3.00 and 0.874, respectively. Bare soil and rock outcrops accounted for 19.3% of the area, resulting in limited forage availability. Multivariate analysis revealed two well-defined groups among the sampling units. One group showed a high degree of internal aggregation, associated with deep soils, and was characterized by the presence of tussocks, whereas the other was less aggregate and was characterized by prostrate species growing on shallow soil. Ordination analysis indicated a gradient of moisture and of soil depth in the study area, resulting in different vegetation patterns. These patterns were analogous to the vegetation physiognomies described for Uruguayan grasslands. Overall, the grassland community studied is similar to others found throughout southern Brazil, although it harbors more winter forage species. In addition, the rare grass Paspalum indecorum Mez is locally dominant in some patches, behaving similarly to P. notatum Fl., a widespread grass that dominates extensive grassland areas in southern Brazil

Nuevos aportes a la historia natural de la mulita pampeana Dasypus hybridus (Mammalia, Dasypodidae)

En este trabajo se presentan nuevos aportes sobre la historia natural de la mulita pampeana Dasypus hybridus (Desmarest, 1804) (Mammalia, Xenarthra, Dasypodidae). Los estudios de campo fueron llevados a cabo en 100 ha de cuatro establecimientos agropecuarios de la provincia de Buenos Aires, Argentina. Durante tres años se realizó un muestreo estacional de armadillos por captura y liberación. Se obtuvieron datos de hábitos alimentarios, uso del espacio y del tiempo, comportamiento, termorregulación, datos poblacionales y morfológicos. Se realizaron 71 capturas. En la dieta el ítem principal registrado fue material vegetal, seguido por hormigas e insectos coleópteros; no se observó una diferencia estacional en los hábitos alimentarios. La actividad de las mulitas se concentra durante el día, existió una baja en la frecuencia de observación durante las estaciones frías (otoño e invierno). La mulita pampeana prefiere suelos húmicos, terrenos altos y pastizales densos y altos; asimismo seleccionan los montes para refugiarse. Son individuos asociales. La temperatura rectal mostró correlaciones positivas con la temperatura ambiente. La proporción de sexos fue cercana a uno y no se observó dimorfismo sexual. Los resultados obtenidos concuerdan parcialmente con lo observado para otras especies del género, destacando las tendencias observadas en los hábitos alimentarios y en la estrategia termorregulatoria. Este trabajo representa un aporte en varios aspectos de una especie poco estudiada en una zona bajo importantes presiones de uso y modificación de hábitat

Microbial quality of soil from the Pampa biome in response to different grazing pressures

The aim of this study was to evaluate the impact of different grazing pressures on the activity and diversity of soil bacteria. We performed a long-term experiment in Eldorado do Sul, southern Brazil, that assessed three levels of grazing pressure: high pressure (HP), with 4% herbage allowance (HA), moderate pressure (MP), with 12% HA, and low pressure (LP), with 16% HA. Two reference areas were also assessed, one of never-grazed native vegetation (NG) and another of regenerated vegetation after two years of grazing (RG). Soil samples were evaluated for microbial biomass and enzymatic (β-glucosidase, arylsulfatase and urease) activities. The structure of the bacterial community and the population of diazotrophic bacteria were evaluated by RFLP of the 16S rRNA and nifH genes, respectively. The diversity of diazotrophic bacteria was assessed by partial sequencing of the 16S rDNA gene. The presence of grazing animals increased soil microbial biomass in MP and HP. The structures of the bacterial community and the populations of diazotrophic bacteria were altered by the different grazing managements, with a greater diversity of diazotrophic bacteria in the LP treatment. Based on the characteristics evaluated, the MP treatment was the most appropriate for animal production and conservation of the Pampa biome