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General Indicator (general + indicator)
Selected AbstractsThe relative importance of latitude matching and propagule pressure in the colonization success of an invasive forbECOGRAPHY, Issue 6 2006John L. Maron Factors that influence the early stages of invasion can be critical to invasion success, yet are seldom studied. In particular, broad pre-adaptation to recipient climate may importantly influence early colonization success, yet few studies have explicitly examined this. I performed an experiment to determine how similarity between seed source and transplant site latitude, as a general indicator of pre-adaptation to climate, interacts with propagule pressure (100, 200 and 400 seeds/pot) to influence early colonization success of the widespread North American weed, St. John's wort Hypericum perforatum. Seeds originating from seven native European source populations were sown in pots buried in the ground in a field in western Montana. Seed source populations were either similar or divergent in latitude to the recipient transplant site. Across seed density treatments, the match between seed source and recipient latitude did not affect the proportion of pots colonized or the number of individual colonists per pot. In contrast, propagule pressure had a significant and positive effect on colonization. These results suggest that propagules from many climatically divergent source populations can be viable invaders. [source] Avian Risk Assessment: Effects of Perching Height and DetectabilityETHOLOGY, Issue 4 2004Daniel T. Blumstein We studied two components of predator risk assessment in birds. While many species are limited to seeking safety under cover or under ground, some birds can fly away from their predators and escape to trees. If birds in fact ,feel' safer (e.g. perceive less risk) in trees, we would expect them to tolerate closer approach by a potential terrestrial predator. Another component of safety is at which point the animal detects an approaching threat, which we expected to increase with eye size, assuming eye size is a surrogate for visual acuity. We used the distance birds moved away from an approaching human [flight initiation distance (FID)] as a metric to determine whether birds associated a lower risk of predation by being in trees, and we used the distance at which birds first displayed alert behaviors from an approaching human (alert distance) to determine if birds with larger eyes had higher detection distances. Although some species were affected by tree height, we found no clear pattern that birds assessed themselves to be at a lower risk of predation when they were ,3 m above the ground compared with being <3 m above ground. In the 10 species for which height had any significant effect on FID, birds ,3 m off the ground had greater FIDs in six species, but the remaining three species had the opposite response. While we found a significant positive relationship between eye size and alert distance in 23 species, the relationship was not present in a phylogenetic analysis using independent contrasts, which suggests that the apparent relationship was influenced strongly by the association between the studied species. Together, these results suggest that birds do not obviously associate being in a tree with safety, and that variations in visual acuity, per se, cannot be used as a general indicator of differences in alert distances, as previously suggested in the literature. [source] Optimization of an industrial afterburnerJOURNAL OF CHEMOMETRICS, Issue 1 2003Tomas Öberg Abstract An industrial afterburner was optimized using statistical experimental design. A computer-generated optimal design was adapted to domain constraints and previous knowledge about the experimental variables. Carbon monoxide was used as a general indicator for the operating conditions, and a reduced response surface model was fitted to the experimental data. In a second phase the initial results were verified and investigated in more detail with regard to chlorinated aromatics. The empirical models obtained were further interpreted using results from laboratory investigations and more fundamental knowledge from combustion theory. Copyright © 2003 John Wiley & Sons, Ltd. [source] Fertility, Education, and Development: Evidence from IndiaPOPULATION AND DEVELOPMENT REVIEW, Issue 1 2001Jean Drčze Fertility has declined significantly in many parts of India since the early 1980s. This article examines the determinants of fertility levels and fertility decline, using data on Indian districts for 1981 and 1991. The authors find that women's education and child mortality are the most important factors explaining fertility differences across the country and over time. Low levels of son preference also contribute to lower fertility. By contrast, general indicators of modernization and development such as urbanization, poverty reduction, and male literacy exhibit no significant association with fertility. En passant, the authors probe a subject of much confusion, the relation between fertility decline and gender bias. [source] | ||||||||||