Enhancing quantitative approaches for assessing community resilience.

Scholars from many different intellectual disciplines have attempted to measure, estimate, or quantify resilience. However, there is growing concern that lack of clarity on the operationalization of the concept will limit its application. In this paper, we discuss the theory, research development and quantitative approaches in ecological and community resilience. Upon noting the lack of methods that quantify the complexities of the linked human and natural aspects of community resilience, we identify several promising approaches within the ecological resilience tradition that may be useful in filling these gaps. Further, we discuss the challenges for consolidating these approaches into a more integrated perspective for managing social-ecological systems.

Export of nitrogen from catchments: a worldwide analysis.

This study reviews nitrogen export rates from 946 rivers of the world to determine the influence of quantitative (runoff, rainfall, inhabitant density, catchment area, percentage of land use cover, airborne deposition, fertilizer input) and qualitative (dominant type of forest, occurrence of stagnant waterbodies, dominant land use, occurrence of point sources, runoff type) environmental factors on nitrogen fluxes. All fractions (total, nitrate, ammonia, dissolved organic and particulate organic) of nitrogen export showed a left-skewed distribution, which suggests a relatively pristine condition for most systems. Total nitrogen export showed the highest variability whereas total organic nitrogen export comprised the dominant fraction of export. Nitrogen export rates were only weakly explained by our qualitative and quantitative environmental variables. Our study suggests that the consideration of spatial and temporal scales is important for predicting nitrogen export rates using simple and easy-to-get environmental variables. Regionally based modelling approaches prove more useful than global-scale analyses.

Phylogenetic analysis of phagotrophic, photomorphic and osmotrophic euglenoids by using the nuclear 18S rDNA sequence.

Phylogenetic analyses of 35 strains including 25 previously published sequences and 10 which have been newly sequenced, representing two species of Euglena, five species of Phacus and three species of Astasia, were carried out using the SSU rDNA. Parsimony, distance and maximum-likelihood inferred phylogenies support (1) monophyly of the euglenoids, (2) kinetoplastids as the sister group, (3) the phagotrophic Petalomonas cantuscygni Cann et Pennick anchoring the base of the euglenoid lineage, (4) evolution of phototrophy within the euglenoids from a single event, (5) multiple origins of osmotrophic euglenoids and (6) polyphyly of the genera Euglena Ehrenberg and Phacus Dujardin. Analyses also indicate that Lepocinclis Perty, Trachelomonas Ehrenberg and Astasia Dujardin are polyphyletic. In addition, the results suggest that neither the Euglenales nor the Eutreptiales form a monophyletic lineage, thus questioning currently available classifications. Concerning the phagotrophic mode of nutrition, the data suggest that the feeding apparatus arose multiple times.