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81.
Traditionally it has been assumed by ecologists that the dispersion of positions with respect to leks of female capercaillies
during the mating season is superior to the dispersion of positions of male capercaillies. However some recently published
articles suggest the idea that dispersion is not sex-biased, but both sexes show a similar dispersion. This article introduces
a mathematical model to approach the study of the above question by means of an indexed dispersion criterion. This model is
developed in detail thus deriving its main mathematical properties. On this basis, the model is applied to the analysis of
the motivating problem with real data of positions of leks and female and male capercaillies. The results derived by means
of the model put into doubt the traditional assumption of a superior dispersion of females supporting the new theories, that
is, both sexes show a similar dispersion. 相似文献
82.
Aldas Miguel Pavon Cristina De La Rosa-Ramírez Harrison Ferri José Miguel Bertomeu David Samper María Dolores López-Martínez Juan 《Journal of Polymers and the Environment》2021,29(8):2686-2700
Journal of Polymers and the Environment - Since biodegradable materials are unwittingly mixed with synthetic materials, this work aimed to study the feasibility of reliably identifying some... 相似文献
83.
Innovation for sustainable development in artisanal mining: Advances in a cluster of opal mining in Brazil 总被引:1,自引:0,他引:1
The objective of this article is to understand how the promotion of clusters of small economic agents in the gem sector has brought some improvements in the economic, social and environmental conditions in the mining sector and activities related to it. The research provides policy and theoretical contributions to the field of gem production, as well as enhances understanding of the under researched opal production in Brazil. It argues that government funding and technical support dedicated to the development of mining clusters, i.e. working with small economic agents as a whole and not individually, could promote not only more economic development, but also effectively incorporate social and environmental issues, such as workers safety, water management and tailings recycling. The argument is based on an evaluation of environmental, economic, social and institutional aspects of the opal mining cluster in Pedro II municipality, Piauí state. The results suggest that some formalisation of existing practices and adequate policies have triggered innovation with some positive effects on the performance of artisanal mining. Nevertheless, there are indications that if decision-makers plan to make this cluster more sustainable, they will have to include other issues in the debate including developing substituting economic activities. 相似文献
84.
Three different systems of designating protected areas in a Mediterranean region in southeastern Spain were studied, referring
to their effectiveness and efficiency for protecting both the breeding territories and the suitable habitat of a set of ten
raptor species. Taking into consideration the varying degrees of endangerment of these species, a map of multispecies conservation
values was also drawn up and superimposed on the three protected-area systems studied. In order to compare the levels of protection
afforded by the three systems, we considered two indices that measured their relative effectiveness and efficiency. The effectiveness
estimated the proportion of territories or optimal habitat protected by the networks while efficiency implicitly considered
the area of each system (percentage of breeding territories or optimal habitat protected per 1% of land protected). Overall,
our results showed that the most efficient system was that formed by the set of regional parks and reserves (17 protected
breeding territories per 100 km2), although, given its small total area, it was by far the least effective (only protecting the 21% of the breeding territories
of all species and 17% of the area of high conservation value). The systems formed by the Special Protection Areas (designated
under the EU “Birds Directive”) and by the Special Conservation Areas (designated under the EU “Habitats Directive”) notably
increased the percentages of protected territories of all species (61%) and area of high conservation value (57%), but their
efficiency was not as high as expected in most cases. The overall level of protection was high for all species except for
the Lesser Kestrel (Falco naumanni), an endangered falcon that inhabits pseudo-steppe and traditional agricultural habitats, which are clearly underrepresented
in the protected-area network of the study region. 相似文献
85.
Rita JC Gama-Rodrigues EF Gama-Rodrigues AC Polidoro JC Machado RC Baligar VC 《Environmental management》2011,48(1):134-141
Agroforestry systems (AFSs) have an important role in capturing above and below ground soil carbon and play a dominant role
in mitigation of atmospheric CO2. Attempts has been made here to identify soil organic matter fractions in the cacao-AFSs that have different susceptibility
to microbial decomposition and further represent the basis of understanding soil C dynamics. The objective of this study was
to characterize the organic matter density fractions and soil size fractions in soils of two types of cacao agroforestry systems
and to compare with an adjacent natural forest in Bahia, Brazil. The land-use systems studied were: (1) a 30-year-old stand
of natural forest with cacao (cacao cabruca), (2) a 30-year-old stand of cacao with Erythrina glauca as shade trees (cacao + erythrina), and (3) an adjacent natural forest without cacao. Soil samples were collected from 0-10 cm
depth layer in reddish-yellow Oxisols. Soil samples was separated by wet sieving into five fraction-size classes (>2000 μm,
1000–2000 μm, 250–1000 μm, 53–250 μm, and <53 μm). C and N accumulated in to the light (free- and intra-aggregate density
fractions) and heavy fractions of whole soil and soil size fraction were determined. Soil size fraction obtained in cacao
AFS soils consisted mainly (65 %) of mega-aggregates (>2000 μm) mixed with macroaggregates (32–34%), and microaggregates (1–1.3%).
Soil organic carbon (SOC) and total N content increased with increasing soil size fraction in all land-use systems. Organic
C-to-total N ratio was higher in the macroaggregate than in the microaggregate. In general, in natural forest and cacao cabruca
the contribution of C and N in the light and heavy fractions was similar. However, in cacao + erythrina the heavy fraction
was the most common and contributed 67% of C and 63% of N. Finding of this study shows that the majority of C and N in all
three systems studied are found in macroaggregates, particularly in the 250–1000 μm size aggregate class. The heavy fraction
was the most common organic matter fraction in these soils. Thus, in mature cacao AFS on highly weathered soils the main mechanisms
of C stabilization could be the physical protection within macroaggregate structures thereby minimizing the impact of conversion
of forest to cacao AFS. 相似文献
86.
A review of the distribution of particulate trace elements in urban terrestrial environments and its application to considerations of risk 总被引:6,自引:0,他引:6
We review the evolution, state of the art and future lines of research on the sources, transport pathways, and sinks of particulate
trace elements in urban terrestrial environments to include the atmosphere, soils, and street and indoor dusts. Such studies
reveal reductions in the emissions of some elements of historical concern such as Pb, with interest consequently focusing
on other toxic trace elements such as As, Cd, Hg, Zn, and Cu. While establishment of levels of these elements is important
in assessing the potential impacts of human society on the urban environment, it is also necessary to apply this knowledge
in conjunction with information on the toxicity of those trace elements and the degree of exposure of human receptors to an
assessment of whether such contamination represents a real risk to the city’s inhabitants and therefore how this risk can
be addressed. 相似文献
87.
Maria Clara P. Amorim José Miguel Simões Vitor C. Almada Paulo J. Fonseca 《Behavioral ecology and sociobiology》2011,65(4):707-716
Signal attributes should show different degrees of variability depending on the information to be conveyed. Species identity
is usually associated with stereotyped features of a signal, whereas other types of information such as individual quality
and motivation are associated with signal plasticity. Lusitanian toadfish males form aggregations during the breeding season
and emit a tonal advertisement call (the boatwhistle) to attract mates to their nests. We test the hypothesis that the boatwhistle
can convey information both on individual identity and motivation by checking how signal parameters vary with time. We study
how the physical (tide level) and social (calling alone or in a chorus) environments and male calling rate affect this advertisement
signal and how all these external and internal factors (environment, social and male motivation) blend to modulate the Lusitanian
toadfish’s advertisement call. Boatwhistles of each male were very stereotyped in short periods of time (minutes), but intra-male
signal variability greatly increased in a longer time scale (days). Nevertheless, significant differences among males could
still be found even in a long time scale. Pulse period was the acoustic feature that most contributed to discriminate among
males. Tide level and male calling rate modulated boatwhistle characteristics, and there was a differential effect of tide
on call attributes depending on male calling rate. Social acoustic environment only affected calling rate. These results suggest
that inter-individual differences in call characteristics and call plasticity may mediate both male–male assessment and mate
choice. 相似文献
88.
Santos MJ Sousa JP Tiago I Veríssimo A Lemos MF 《Journal of environmental monitoring : JEM》2011,13(8):2102-2104
Changes in saprophytic organism's gut microbial communities may present a threat to organic matter breakdown which can ultimately lead to soil function impairment. In this study, Amplified Ribosomal DNA Restriction Analysis (ARDRA) was evaluated as a potential simple molecular tool to assess shifts in bacterial community structure in hindgut populations of Porcellio dilatatus exposed to contaminated food. This prospective tool can also be used for a variety of purposes and samples prior to the use of more specific and sophisticated methods. 相似文献
89.
Donald H Feener Matthew R Orr Kirt M Wackford Jose M Longo Woodruff W Benson Lawrence E Gilbert 《Ecology》2008,89(7):1824-1836
A predictive framework for the ecology of species invasions requires that we learn what limits successful invaders in their native range. The red imported fire ant (Solenopsis invicta) is invasive in the United States, Puerto Rico, Australia, New Zealand, and China. Solenopsis invicta appears to be a superior competitor in its introduced range, where it can cause the local extirpation of native species, but little is known about its competitive ability in its native range in South America. Here we examine the competitive ability of S. invicta for food resources in three widely separated Brazilian ant communities. Each of these communities contains 20-40 ant species, 8-10 of which were common and frequently interacted with S. invicta. S. invicta at all three sites was attacked by several species-specific phorid parasitoids, and at one site, two other species were attacked by their own specialized parasitoids. We examined interactions in these local communities for evidence that trade-offs among ant species between resource dominance and resource discovery, and between resource dominance and parasitoid vulnerability facilitate local coexistence. The trade-off between resource dominance and resource discovery was strong and significant only at Santa Genebra, where parasitoids had no effect on the outcome of confrontations at resources. At Bonito, parasitoids significantly reduced the ability of S. invicta, which was the top-ranked behavioral dominant, from defending and usurping food resources from subordinate species. In the Pantanal, S. invicta ranked behind three other ant species in a linear hierarchy of behavioral dominance, and lost the majority of its interactions with a fourth more subordinate species, Paratrechina fulva, another invasive species. Parasitoids of S. invicta were uncommon in the Pantanal, and did not affect its low position in the hierarchy relative to the other two sites. Parasitoids, however, did affect the ability of Linepithema angulatum, the top-ranked behavioral dominant in this community, from defending and usurping resources from behavioral subordinates. These results indicate that both interspecific competition and trait-mediated indirect effects of phorid parasitoids affect the ecological success of the red imported fire ant in its native range, but that the relative importance of these factors varies geographically. 相似文献
90.
Francisco Leitão Miguel N. Santos Karim Erzini Carlos Costa Monteiro 《Marine Biology》2008,153(6):1233-1244
There is a concern that artificial reefs (AR) may act purely as fishing aggregation devices. Predators attracted to ARs can
influence the distribution and abundance of prey fish species. Determining the role of predators in AR is important in advancing
the understanding of community interactions. This paper documents the effects of predation on fish assemblages of AR located
near a coastal lagoon fish nursery. The Dicentrarchus labrax is a very opportunistic species preying on juveniles (0+ and 1+ age classes) of several demersal fish species on the ARs. Reef prey and sea bass abundance were negatively correlated. The
mean numbers of prey per sea bass stomach increased with the increase of reef fish prey abundance, suggesting that predation
has a significant influence, resulting in a decrease in prey abundance. Prey mortality (4–48%) of demersal reef fish associated
species depends on bass density. Prey selection was related both with prey abundance and vulnerability. Results showed that
D. labrax predation on AR-fish associated species can increase prey natural mortality. However, the role of bass predation on the ecological
functioning of exploited ARs is not clear. There may be increases in local fishing yields due either to an increase in predator
biomass through aggregation of sea bass attracted to ARs or to greater production. In contrast, predation on juveniles of
economically important reef fish preys, especially the most frequent and abundant (Boops boops), can contribute to a decrease in recruitment to the fishery. Our results indicate that inter-specific interactions (predator–prey)
are important in terms of conservation and management, as well as for the evaluation of the long-term effects of reef deployment.
Thus, it is necessary to consider ecological interactions, such as predation, prior to the development and deployment of artificial
habitats as a tool for rehabilitation. 相似文献