Arsenic and boron contamination in the Loa basin (northern Chile)

This paper presents the first results of a hidrogeochemical investigation in the Loa River basin (33.400 km2) in the Antofagasta Region, Northern Chile. The Loa River (440 km long) is the only permanent stream in this deserted region (Atacama Desert), with a flow of water ranging between 0.5 and 3 m3/s. High salinity and high levels of dissolved arsenic and boron made waters from Loa River not directly suitable for drinking water supply. The irrigation use is limited. In order to evaluate the present situation, water samples were taken at 13 strategic points along the Loa River and its mayor tributaries

Patch-level facilitation fosters high-Andean plant diversity at regional scales

Aim: Local effects of ecosystem engineers on biodiversity can scale up to the landscape level, stressing the importance of ecological processes as determinants of species richness at larger spatial scales. In harsh environments, cushion plants often act as ecosystem engineers given their ability to buffer extreme abiotic conditions, thus providing unique and more favorable niches for the establishment of less stress-tolerant plant species. We assessed if facilitation by cushion plants influences patterns of plant diversity at increasing spatial scales. Location: Northern Patagonian Andes, Argentina. Methods: Based on plant species records within and outside cushions, we compared plant diversity in the presence and absence of cushions at the community, mountain and regional scale. Specifically, observed and estimated numbers of species occurring in either cushion plants or in the surrounding open areas were compared with the species numbers of the open areas. Results: The presence of cushion plants significantly increased species richness at all spatial levels analyzed. At the patch level, a higher number of species was recorded growing within cushion plants than in open area plots of similar size. Consistently, hypothetical communities lacking cushion plants showed significantly lower species richness than observed communities with cushion plants. These differences in species richness at patch and community scales increased with altitude, hence facilitation by cushion plants became more important at higher elevations. Moreover, according to asymptotic non-parametric estimators, cushion plants could increase overall regional species richness up to 40%. Conclusions: Our findings suggest that about one third of the high-Andean flora of the region owes its presence to the existence of nursing plants, defying the view that abiotic factors alone are enough to fully determine species occurrences at large spatial scales. This study provides evidence that local-scale ecological processes can be crucial in promoting and maintaining biodiversity at any spatial scale.Fil: Gavini, Sabrina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Ezcurra, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Aizen, Marcelo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentin

Produção e qualidade da videira 'Superior Seedless' sob restrição hídrica na fase de maturação Production and quality of 'Superior Seedless' grapes under irrigation restrictions during berry maturation

O objetivo deste trabalho foi avaliar o efeito das condições de deficit hídrico, na fase de maturação da uva, sobre a produção e qualidade da uva 'Superior Seedless' entre julho e novembro de 2007. O experimento foi realizado em delineamento de blocos ao acaso, com quatro repetições, em arranjo fatorial (3x3) + 1: três épocas de alteração da aplicação das lâminas de irrigação (21, 13 e 5 dias antes da colheita); três lâminas de irrigação (100, 50 e 0% da evapotranspiração da cultura); e um tratamento controle (manejo de irrigação adotado pelo produtor). As épocas de irrigação e as lâminas de irrigação utilizadas influenciaram a firmeza das bagas e a acidez titulável. A interrupção da irrigação, aos 13 ou 21 dias antes da colheita, resultou em produtividade, qualidade de frutos e eficiência do uso da água semelhante às obtidas pelo produtor, assim, pode ser adotada para economia da água de irrigação na Região do Submédio do Vale do São Francisco.<br>The objective this work was to evaluate the effect of water deficit conditions, during the maturation phase of grapes, on the production and quality of the 'Superior Seedless', between July and November of 2007. The experiment was carried out in a randomized block design, with four replicates, in a (3x 3) + 1 factorial arrangement: three times of alteration of the irrigation depths (21, 13 e 5 days before harvest); three irrigation depths (100, 50 e 0% of crop evapotranspiration); and a control treatment, which was the producer's irrigation management scheme. Irrigation timing and depth influenced berry firmness and titrable acidity. The management with cut-off irrigation depths at 13 or 21 days before harvesting and the control had the same yield, grape quality and water use efficiency, and may be adopted to save water for irrigation in the São Francisco Valley region