The inner granulometric density of the tracks in nuclear emulsions and its application to determine the chemical spectrum of primary cosmic ray nuclidi

A method by which inner granulo metric densities of nuclear emulsion tracks can be used to determine the chemical spectrum of primary cosmic ray nuclei is presented

Subtidal macrozoobenthos communities from northern Chile during and post El Niño 1997–1998

Despite a large amount of climatic and oceanographic information dealing with the recurring climate phenomenon El Niño (EN) and its well known impact on diversity of marine benthic communities, most published data are rather descriptive and consequently our understanding of the underlying mechanisms and processes that drive community structure during EN are still very scarce. In this study, we address two questions on the effects of EN on macrozoobenthic communities: (1) how does EN affect species diversity of the communities in northern Chile? and (2) is EN a phenomenon that restarts community assembling processes by affecting species interactions in northern Chile? To answer these questions, we compared species diversity and co-occurrence patterns of soft-bottoms macrozoobenthos communities from the continental shelf off northern Chile during (March 1998) and after (September 1998) the strong EN event 1997–1998. The methods used varied from species diversity and species co-occurrence analyses to multivariate ordination methods. Our results indicate that EN positively affects diversity of macrozoobenthos communities in the study area, increasing the species richness and diversity and decreasing the species dominance. EN represents a strong disturbance that affects species interactions that rule the species assembling processes in shallow-water, sea-bottom environments

Consecuencias de la tala maderera colonial en los bosques de alerce de Chiloé, sur de Chile (Siglos XVI-XIX) Colonial timber felling consequences of the alerce forests in Chiloé, southern Chile (18TH and 19TH centuries)

Durante el proceso de colonización española la madera de alerce se transformó en el principal recurso económico de Chiloé, generándose una importante actividad mercantil sustentada en la tala de dicha especie arbórea. Mediante un análisis histórico documental, que abarca desde el siglo XVI al XIX, se examinó la evolución de la tala y del comercio maderero local, evaluándose sus efectos ambientales sobre la cobertura boscosa original del territorio. Los resultados obtenidos permiten constatar que la tala colonial del alerce habría generado sólo una moderada alteración de los alerzales más accesibles, en comparación a lo ocurrido en los inicios de la República tras la notoria intensificación de la explotación maderera. En consecuencia se descarta la tradicional idea de la desaparición o extinción de alerzales en Chiloé durante el dominio colonial.During the Spanish settlement processes the wood from the Alerce tree was the main economical resource of Chiloé (Southern Chile), generating an important commercial activity in the region. The development of the Alerce timber and trading was studied based on historical-documentary analysis including data from the 16th to 19th century. Special attention on the environmental effect was assessed based on the original Alerce forest conditions. Findings allow concluding that the colonial Alerce removal it would have caused only a minor disturbance to the original forest, and it would have taken place within the most accessible Alerzales (Alerce patches) only, contrary to the situation observed at the beginning of the republic period when an enormous Alerce exploitation was experimented. Therefore, it has been proved that the disappearance and extinction of Alerzalesin Chiloé, during the colonial domain, did not occur