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711.
Felix G. Marx Mónica R. Buono R. Ewan Fordyce R. W. Boessenecker 《Die Naturwissenschaften》2013,100(3):257-261
The origin of the pygmy right whale (Caperea marginata) has long been one of the most vexing conundrums of marine mammal evolution. The extremely disparate skeletal structure of Caperea and a patchy fossil record have left morphology and molecules at odds: whereas most morphological analyses ally Caperea with right whales (Balaenidae), most molecular studies instead suggest a close relationship with rorquals (Balaenopteridae) and grey whales (Eschrichtiidae). The morphological evidence supporting a Caperea-balaenid clade consists of several shared features of the skull and mandible, as traditionally observed in adult individuals. Here, we show that at least two of these features, the ascending process of the maxilla and the coronoid process, arise from substantially different precursors early during ontogeny and therefore likely do not represent genuine synapomorphies. Both of these juvenile morphologies have adult counterparts in the fossil record, thus indicating that the ontogenetic variation in the living species may be a genuine reflection of differing ancestral states. This new evidence contradicts previous morphological hypotheses on the origins of Caperea and may help to reconcile morphological and molecular evidence. 相似文献
712.
Mario Martínez-Córcoles Francisco Gracia Inés Tomás José M. Peiró 《Safety Science》2011,49(8-9):1118-1129
Leadership is considered an essential element in guaranteeing the safe running of organizations. The purpose of the present study is to find out how leader behaviours influence employees’ safety behaviours (perceived safety behaviours) in the nuclear field. In an attempt to answer this question, the authors of this research have considered the way this influence is exercised, taking into consideration some important factors like safety culture and safety climate. To achieve this, the empowerment leadership model, based on a behavioural approach to leadership, was used. The sample was made up of 566 employees from a Spanish nuclear power plant. The results indicated that when safety culture was strong, leader behaviour generated a higher safety climate among the members, which predicted their perceived safety behaviours. Support was found for a structural model linking leadership and safety behaviour to safety culture and safety climate. The implications of these findings for the theory of safety and the way they can be put into practice are outlined. 相似文献
713.
New sustainable agriculture techniques are arising in response to the environmental problems caused by intensive agriculture, such as nitrate leaching and surface water eutrophication. Organic fertilization (e.g., with sewage sludge) and agroforestry could be used to reduce nutrient leaching. We assessed the efficiency of establishing trees and pasture species in environmentally sensitive, irrigated Mediterranean grassland soils in controlling nitrate leaching. Four vegetation systems-bare soil, pasture species, cherry trees [ (L.) L.], and pasture-tree mixed plantings-and five fertilization treatments-control, two doses of mineral fertilizer, and two doses of organic fertilizer (sewage sludge)-were tested in a greenhouse experiment over 2 yr. In the experiment, the wet and warm climate characteristics of Mediterranean irrigated croplands and the plant-to-plant and soil-to-plant interactions that occur in open-field agroforestry plantations were simulated. Following a factorial design with six replicates, 120 pots (30-cm radius and 120 cm deep) were filled with a sandy, alluvial soil common in the cultivated fluvial plains of the region. The greatest pasture production and tree growth were obtained with sewage sludge application. Both pasture production and tree growth decreased significantly in the pasture-tree mixed planting. Nitrate leaching was negligible in this latter treatment, except under the highest dose of sewage sludge application. The rapid mineralization of sludge suggested that this organic fertilizer should be used very cautiously in warm, irrigated Mediterranean soils. Mixed planting of pasture species and trees, such as , could be a useful tool for mitigating nitrate leaching from irrigated Mediterranean pastures on sandy soils. 相似文献
714.
Flores-Álvarez JM González I García-de la Rosa LA Mancilla-Peña F Reyes-Gómez J 《Journal of environmental management》2011,92(3):448-456
Carbon paste electrodes (CPEs) modified with a biosolid, two types of soils with different amounts of organic matter (OM), and two biocomposites (soils mixed with a biosolid) were used to assess and compare the Cu(II) ion retention properties of the organic matter contained in the samples. The accumulation of Cu(II) on the surface of the modified carbon paste electrodes (MCPEs) was performed under open-circuit conditions. When comparing the response of the MCPEs while assessing parameters such as pH, preconcentration time, and adsorption/desorption capacity, it was found that the reaction mechanism of the two soils is different between the soils and dissimilar from the biosolid; while the biocomposites show reaction mechanisms that are intermediate between those of the soils and the biosolid. This was proven with the use of infrared spectroscopy, since the FTIR spectra show similarities between the two soils and significant differences between the soils and the biosolid. 相似文献
715.
Eakin H Bojórquez-Tapia LA Monterde Diaz R Castellanos E Haggar J 《Environmental management》2011,47(3):352-367
Communities who rely directly on the natural environment for their survival typically have developed risk management strategies
to enable them to avoid dangerous thresholds of change to their livelihoods. Development policy appropriate for natural resource-based
communities requires an understanding of the primary drivers of social-ecological change, the ways in which affected households
autonomously respond to such drivers, and the appropriate avenues for intervention to reduce vulnerability. Coffee has been,
and still remains, one of the most important commodities of the Mesoamerican region, and hundreds of thousands of smallholder
households in the region are dependent in some way on the coffee industry for their livelihood stability. We used the Analytical
Network Process to synthesize expert knowledge on the primary drivers of livelihood change in the region as well as the most
common household strategies and associated capacities necessary for effective response. The assessment identified both gradual
systemic processes as well as specific environmental and market shocks as significant drivers of livelihood change across
the region. Agronomic adjustments and new forms of social organization were among the more significant responses of farmers
to these changes. The assessment indicates that public interventions in support of adaptation should focus on enhancing farmers’
access to market and technical information and finance, as well as on increasing the viability of farmers’ organizations and
cooperatives. 相似文献
716.
Melania Salazar-Ordóñez Samir Sayadi 《Journal of Agricultural and Environmental Ethics》2011,24(3):243-258
At its beginning, the European Union’s Common Agricultural Policy (CAP) did not include measures to guide farmers in preserving
ecosystems. At the same time, the social context on the 1960s and 1970s did not encourage environmental care to become a priority.
Since the 1980s, new social concern expressed alarm over ecology, recognizing that agriculture can pollute. These social changes
moved the CAP to add measures that linked agriculture and environment. In order to study if the EU decision-makers have designed
a CAP which responds to a new ethic that incorporates environmental care and social demands, two questions rise: whether the
social image of agriculture as a polluting activity has changed; and whether farming performs the environmental functions
demanded by society. To answer the previous questions, we have reviewed the environmental aspects added to the CAP, then a
poll has been conducted and cluster method and classification tree models have been used to group respondents according to
their opinions. The results show that the society ascribes great relevance to the environment for the future sustainability
of the region, but they are not satisfied with the role of agriculture in producing environmental outputs. 相似文献
717.
. Despite the increased complexity of experimental and theoretical studies on the biodiversity-ecosystem functioning (B-EF) relationship, a major challenge is to demonstrate whether the observed importance of biodiversity in controlled experimental systems also persists in nature. Due to their structural simplicity and their low levels of human impacts, extreme species-poor ecosystems may provide new insights into B-EF relationships in natural systems. We address this issue using shredder invertebrate communities and organic matter decomposition rates in 24 high-altitude (3200-3900 m) Neotropical streams as a study model. We first assessed the effects of stream characteristics and shredder diversity and abundance on organic matter decomposition rates in coarse- and fine-mesh bags. We found the interaction term shredder richness x shredder abundance had the most significant impact on decomposition rates in the field, although water discharge may also play a role locally. We also examined the relative contribution of the three most abundant shredders on decomposition rates by manipulating shredder richness and community composition in a field experiment. Transgressive overyielding was detected among the three shredder species, indicating complementary resource use and/or facilitation. By integrating survey and experimental data in surface response analyses we found that observed B-EF patterns fit those predicted by a linear model that described litter decomposition rates as a function of increasing shredder richness and the relative abundance of the most efficient shredders. Finally, the validity of our approach was tested in a broader context by using two independent but comparable data sets from 49 French and Swedish streams showing more complex shredder community structure. Results revealed that richness and identity effects on decomposition rates were lost with increasing shredder community complexity. Our approach of combining experimental and empirical data with modeling in species-poor ecosystems may serve as an impetus for new B-EF studies. If theory can explain B-EF in low-diversity ecosystems, it may also have credibility in more complex ones. 相似文献
718.
Ruth Fernández Susana García-Tiscar M. Begoña Santos Alfredo López Jose A. Martínez-Cedeira Jason Newton Graham J. Pierce 《Marine Biology》2011,158(5):1043-1055
Skin and muscle from 43 bottlenose dolphins (38 juveniles/adults, 5 calves) stranded in NW Spain were analysed to determine
whether stable isotope ratios (δ13C and δ15N) could be used to assess dietary variation, habitat segregation and population substructure. Results were compared with
published stomach contents data. Stable isotope ratios from 17 known prey species were also determined. Isotope ratios of
the main prey (blue whiting, hake) varied significantly in relation to fish body size. Dolphin calves showed significant heavy
isotope enrichments compared to adult females. Excluding calves, δ15N decreased with increasing dolphin body size, probably related to an ontogenetic shift in diet towards species at lower trophic
levels, e.g. on blue whiting as suggested by stomach content results. Bottlenose dolphins were divided into two putative populations
(North, South) based on previous genetic studies, and values of δ13C and δ15N differed significantly between these two groups, confirming the existence of population structuring. 相似文献
719.
Large quantities of floating macroalgae are traveling in coastal waters of the SE Pacific and in other temperate climate zones.
While afloat, these algae are potentially exposed to full solar radiation, including UVA and UVB, which can have profound
effects on their physiological and growth performance. Latitudinal variations in UV-radiation (UVR) are hypothesized to affect
floating algae differently with higher impacts at low latitudes than at high latitudes. In addition, UVR together with grazing
might accelerate the demise of floating kelps. This hypothesis was tested with outdoor laboratory experiments in which sporophytes
of the giant kelp Macrocystis pyrifera (L.) C. Agardh were exposed to a combination of different UVR regimes (PAR only, PAR + UV) and grazing at three sites along
the Chilean coast (20°S, 30°S, and 40°S). A latitudinal trend in irradiance was detected with increasing values from 40°S
to 20°S. Surprisingly, floating M. pyrifera responded with a high acclimation potential within this latitudinal UVR gradient. At 20°S, floating kelps were slightly sensitive
to UVR, which was reflected in reduced blade growth. At 30°S, physiological responses were hardly affected by the prevailing
irradiance but sporophyte growth and thus persistence mainly depended on the presence or absence of amphipod grazers. At high
latitudes, grazing had only minor impacts on algal biomass and blade growth, and kelps thrived well under all tested environmental
conditions. Overall, our results reveal that floating M. pyrifera was only slightly affected by UVR and that sporophytes can efficiently acclimate over a latitudinal UVR gradient that spans
from 20°S to 40°S. Given this high acclimation potential, we suggest that these (and possibly other) positively buoyant algae
are important dispersal agents over a wide range of temperate latitude conditions. 相似文献
720.
The decay of non-native and native seaweed mixing may modify sediment biogeochemistry and organic matter transfers within
benthic food webs according to their composition and biomass. The non-native species Sargassum muticum was deliberately added to the sediment of an intertidal sandflat at different biomass and mixed to the native species Ulva sp. and Fucus vesiculosus. The sediment porewater was then 13C and 15N enriched to test whether both detrital diversity and biomass influenced the transfer of porewater carbon and nitrogen to
the sediment and to the macrofauna consumers. More 15N-nitrogen was mobilized to sediments and macrofauna when the 3-species detrital mixing was buried, probably because this
mixing provided species-specific compounds such as polyphenols due to the presence of S. muticum and F. vesiculosus, as well as large amounts of nitrogen due to the presence of Ulva. Our study revealed the importance of detrital diversity and non-native seaweeds for the nitrogen cycling in the benthic
food web. 相似文献