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51.
Francisco?Santiago-QuesadaEmail author José?A.?Masero Sora?M.?Estrella Juan?M.?Sánchez-Guzmán 《Behavioral ecology and sociobiology》2012,66(3):397-405
There is a large literature dealing with daily foraging routines of wild birds during the non-breeding season. While different
laboratory studies have showed that some bird activity patterns are a persistent property of the circadian system, most of
field studies preclude the potential role of an endogenous circadian rhythm in controlling bird’s foraging routines. In this
study we compared the patterns of diurnal foraging activity and intake rates of migrating black-tailed godwits, Limosa limosa (radio-tagged and non-tagged individuals) at two stopover sites (habitats) with different environmental characteristics,
aiming at identifying proximate factors of bird activity routines. To gain insights into the role of food availability in
control of such foraging routines, we also estimated foraging activity patterns in captive godwits subjected to constant food
availability. Captive and wild black-tailed godwits showed a persistent bimodal activity pattern through daylight period.
Food availability had a significant effect on the intake rates, but had a subtler effect on foraging and intake rate rhythms.
Temperature and wind speed (combined in a weather index) showed non-significant effects on both rhythms. Although we could
not discard a role for natural diurnal changes in light intensity, an important timing cue, our findings support the idea
that an endogenous circadian rhythm could be an important proximate factor regulating foraging activity and food items taken
per unit time of wild black-tailed godwits during migration. 相似文献
52.
Ebensperger LA Sobrero R Quirici V Castro RA Tolhuysen LO Vargas F Burger JR Quispe R Villavicencio CP Vásquez RA Hayes LD 《Behavioral ecology and sociobiology》2012,66(2):261-274
Intraspecific variation in sociality is thought to reflect a trade-off between current fitness benefits and costs that emerge from individuals' decision to join or leave groups. Since those benefits and costs may be influenced by ecological conditions, ecological variation remains a major, ultimate cause of intraspecific variation in sociality. Intraspecific comparisons of mammalian sociality across populations facing different environmental conditions have not provided a consistent relationship between ecological variation and group-living. Thus, we studied two populations of the communally rearing rodent Octodon degus to determine how co-variation between sociality and ecology supports alternative ecological causes of group living. In particular, we examined how variables linked to predation risk, thermal conditions, burrowing costs, and food availability predicted temporal and population variation in sociality. Our study revealed population and temporal variation in total group size and group composition that covaried with population and yearly differences in ecology. In particular, predation risk and burrowing costs are supported as drivers of this social variation in degus. Thermal differences, food quantity and quality were not significant predictors of social group size. In contrast to between populations, social variation within populations was largely uncoupled from ecological differences. 相似文献
53.
The most recent intervention on the coastline of Espinho, located on the Portuguese West Atlantic coast, was part of the General
Plan for Coastal Protection in 1980/81. As a result, two unusually large groins/headlands were built which were reinforced
and enlarged in 1997, slightly changing their geometry and orientation. However, due to the decreased sediment supply from
the north and the impact of energetic sea conditions common to the northwest coast of Portugal the coastal evolution has not
developed as desired, although in general terms the initial expectations were fulfilled. The numerical modelling of the Espinho
coastline using SMC software focused on both hydrodynamic and hydromorphological aspects. The purpose of this study is to
analyse the most vulnerable areas of the Espinho seafront for current velocities and littoral drift, as well as to confirm
the effectiveness of the two groins in terms of coastal protection. To achieve this, various simulations were performed, taking
into account diverse sea conditions. 相似文献
54.
Farjalla VF Srivastava DS Marino NA Azevedo FD Dib V Lopes PM Rosado AS Bozelli RL Esteves FA 《Ecology》2012,93(7):1752-1759
After much debate, there is an emerging consensus that the composition of many ecological communities is determined both by species traits, as proposed by niche theory, as well as by chance events. A critical question for ecology is, therefore, which attributes of species predict the dominance of deterministic or stochastic processes. We outline two hypotheses by which organism size could determine which processes structure ecological communities, and we test these hypotheses by comparing the community structure in bromeliad phytotelmata of three groups of organisms (bacteria, zooplankton, and macroinvertebrates) that encompass a 10 000-fold gradient in body size, but live in the same habitat. Bacteria had no habitat associations, as would be expected from trait-neutral stochastic processes, but still showed exclusion among species pairs, as would be expected from niche-based processes. Macroinvertebrates had strong habitat and species associations, indicating niche-based processes. Zooplankton, with body size between bacteria and macroinvertebrates, showed intermediate habitat associations. We concluded that a key niche process, habitat filtering, strengthened with organism size, possibly because larger organisms are both less plastic in their fundamental niches and more able to be selective in dispersal. These results suggest that the relative importance of deterministic and stochastic processes may be predictable from organism size. 相似文献
55.
Mattia Trabucchi Francisco A. Comín Patrick J. O’Farrell 《Regional Environmental Change》2013,13(4):911-926
Maintaining and enhancing ecosystem services through the restoration of degraded ecosystems have become an important biodiversity conservation strategy. Deciding where to restore ecosystems for the attainment of multiple services is a key issue for future planning, management, and human well-being. Most restoration projects usually entail a small number of actions in a local area and do not consider the potential benefits of planning restoration at broad regional scales. We developed a hierarchical priority setting approach to evaluate the performance of restoration measures in a semiarid basin in NE Spain (the Martín River Basin, 2,112 km2). Our analysis utilized a combination of erosion (a key driver of degradation in this Mediterranean region) and six spatially explicit ecosystem services data layers (five of these maps plotted surrogates for soil retention and accumulation, water supply and regulation, and carbon storage, and one plotted a cultural service, ecotourism). Hierarchical maps were generated using a geographic information system that combined areas important for providing a bundle of ecosystem services, as state variables, with erosion maps, as the disturbance or regulatory variable. This was performed for multiple scales, thereby identifying the most adequate scale of analysis and establishing a spatial hierarchy of restoration actions based on the combination of the evaluation of erosion rates and the provision of ecosystem services. Our approach provides managers with a straightforward method for determining the spatial distribution of values for a set of ecosystem services in relation to ecological degradation thresholds and for allocating efforts and resources for restoration projects in complex landscapes. 相似文献
56.
He J Dougherty M Shaw J Fulton J Arriaga F 《Journal of environmental management》2011,92(10):2479-2485
Rural areas represent approximately 95% of the 14000 km(2) Alabama Black Belt, an area of widespread Vertisols dominated by clayey, smectitic, shrink-swell soils. These soils are unsuitable for conventional onsite wastewater treatment systems (OWTS) which are nevertheless widely used in this region. In order to provide an alternative wastewater dosing system, an experimental field moisture controlled subsurface drip irrigation (SDI) system was designed and installed as a field trial. The experimental system that integrates a seasonal cropping system was evaluated for two years on a 500-m(2) Houston clay site in west central Alabama from August 2006 to June 2008. The SDI system was designed to start hydraulic dosing only when field moisture was below field capacity. Hydraulic dosing rates fluctuated as expected with higher dosing rates during warm seasons with near zero or zero dosing rates during cold seasons. Lower hydraulic dosing in winter creates the need for at least a two-month waste storage structure which is an insurmountable challenge for rural homeowners. An estimated 30% of dosed water percolated below 45-cm depth during the first summer which included a 30-year historic drought. This massive volume of percolation was presumably the result of preferential flow stimulated by dry weather clay soil cracking. Although water percolation is necessary for OWTS, this massive water percolation loss indicated that this experimental system is not able to effective control soil moisture within its monitoring zone as designed. Overall findings of this study indicated that soil moisture controlled SDI wastewater dosing is not suitable as a standalone system in these Vertisols. However, the experimental soil moisture control system functioned as designed, demonstrating that soil moisture controlled SDI wastewater dosing may find application as a supplement to other wastewater disposal methods that can function during cold seasons. 相似文献
57.
Mar??a Jes??s Aira Francisco Javier Rodr??guez-Rajo Mar??a Fern??ndez-Gonz??lez Victoria Jato 《Environmental monitoring and assessment》2011,173(1-4):765-775
This study analyzed airborne pollen counts for the tree taxa most widely used for ornamental purposes in the northwestern Iberian Peninsula (Platanus, Cupressaceae, Olea, Myrtaceae, Cedrus, and Casuarina) at four sites (Vigo, Ourense, Santiago, and Lugo), using aerobiological data recorded over a long period (1993?C2007). The abundance and the temporal and spatial distribution of these pollen types were analyzed, and the influence of weather-related factors on airborne pollen counts was assessed. Platanus (in Ourense) and Olea (in Vigo) were the taxa contributing most to pollen counts. In general terms, the results may be taken as indicators of potential risk for pollen-allergy sufferers and therefore used in planning future green areas. 相似文献
58.
59.
This article sets outs a generalized utility model for the diagnosis and prediction of accidents among the Spanish workforce. Based on observational data classified into a risk–injury contingency table (19 × 19), we have summarized the accident rate of all Spanish companies over an 11-year period (75,19,732 accidents). By using correspondence analysis a structure composed of three axes can be obtained, the combination of which identifies three separate risk and injury groups, which we use as a general Spanish pattern. The relationships of greater affinity or likelihood amongst the risks and injuries identified in the pattern facilitate decision-making at the risk-assessment stage in Spanish companies. Each risk–injury group has its own characteristics, interpretable within the phenomenological framework of the accident.The main advantage of this model is its potential application to any other country and the feasibility of contrasting results from different countries. One limiting factor, however, is that the model currently lacks a common classification frame for risks and injuries which would enhance this contrast. The aim of this model is to automatically manage work-related accidents at a national level. 相似文献
60.
Rosa María Arnaldo Valdés Fernando Gómez Comendador Luis Mijares Gordún Francisco J. Sáez Nieto 《Safety Science》2011,49(5):633-650
The risks of landing overrun (LDOR – LanDing OverRun), Take-off Overrun (TOOR – Take-Off OverRun) and landing undershoot (LDUS – LanDing UnderShoot) are dependent on multiple factors related to operating conditions. These include wind, runway surface conditions, landing or take-off distances required, the presence of obstacles, runway distance available, the existence and dimensions of runway safety areas.In this paper we propose risk models for runway overrun and landing undershoot, using a probabilistic approach. These models are supported by historical data on accidents in the area around the runway and will enable us to determine if the risk level is acceptable or whether action must be taken to mitigate such risks at a given airport. Furthermore, these models permit comparison of the results of different risk mitigation actions in terms of operational risk and safety.The principal advantage of this method is the high quality results obtained for a limited investment in terms of time, computing power and data. As such the method is extremely practical and easy to apply in aerodrome planning, development and operation. 相似文献