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1.
Llano-Sotelo JM Alcaraz-Melendez L Castellanos Villegas AE 《Journal of environmental biology / Academy of Environmental Biology, India》2010,31(4):497-502
In order to evaluate their responses to drought, we determined the photosynthetic activity water potential, stomatal conductance, transpiration, water use efficiency photosynthetic photon flux density and leaf temperature of Paulownia imperialis, P. fortunei and P. elongata in three different soil moisture conditions in the field. Our results showed that P. imperialis had greater photosynthesis (8.86 micromol CO2 m(-2) s(-1)) and instantaneous water use efficiency (0.79 micromol CO2 mmol H2O(-1)) than either P. elongata (8.20 micromol CO2 m(-2) s(-1) and 0.71 micromol CO2 mmol H2O(-1)) or P. fortunei (3.26 micromol CO2 m(-2) s(-1) and 0.07 micromol CO2 mmol H2O(-1)). The rapid growth of Paulownia did not appear to be correlated with photosynthetic rates. Paulownia fortunei showed more transpiration (48.78 mmol H2O m(-2) s(-1)) and stomatal conductance (840 mmol m(-2) s(-1)) than P. imperialis (20 mmol H2O m(-2) s(-1) and 540 mmol m(-2) s(-1)) and P. elongata (20 mmol H2O m(-2) s(-1) and 410 mmol m(-2) s(-1)), which allowed these two Paulownia species to increase their tolerance to low soil moisture, and maintain higher water use efficiency under these conditions. According to our physiological gas exchange field tests, Paulownia imperialis does appear to be capable of successful growth in semiarid zones. 相似文献
2.
Marta I. Sánchez Andy J. Green Francisco Amat Eloy M. Castellanos 《Marine Biology》2007,151(4):1407-1415
Waterbirds are known to disperse invertebrate propagules that survive gut passage, but there is very little information about
how the probability of dispersal changes at different times of the annual cycle when birds move in different directions, or
how it is affected by changes in diet. We studied internal transport of brine shrimp Artemia cysts by migratory waders in the Odiel saltworks in south-west Spain. Viable cysts of parthenogenetic Artemia were abundant in the faeces and regurgitated pellets of redshank Tringa totanus, pellets of spotted redshank T. erythropus, and faeces of black-tailed godwit Limosa limosa during spring and/or autumn migrations in 2001–2002, but were not recorded during winter. Godwits did not produce pellets,
and spotted redshank faeces were not sampled. Significant correlations between the number of cysts in a pellet or faecal sample
and the proportion of that sample constituted by Artemia adults suggested that most cysts were ingested while in the ovisacs of gravid females. The proportion of cysts destroyed
during digestion increased when accompanied by harder food items or grit, and when fewer cysts were ingested. The median number
of intact cysts was higher in redshank faeces than in their pellets, but cysts extracted from pellets were more likely to
hatch. A higher proportion of redshank pellets contained Artemia cysts in spring than in autumn, but more redshank migrated through the area in autumn. Significantly fewer cysts were recorded
in redshank pellets in winter than in spring or autumn. Our results confirm that there is potential for long-distance dispersal
of Artemia cysts via waders during both northwards (spring) and southwards (autumn) migrations. 相似文献
3.
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
4.
Gonzalez-Ocampo H Romero-Schmidt H Serrano-Pinto V Arguelles C Salinas F Rodríguez A Castellanos A Ortega-Rubio A 《Journal of environmental biology / Academy of Environmental Biology, India》2004,25(1):27-38
Aquaculture offers a major opportunity for the economic development of Baja California Sur (BCS), Mexico. The severely limited freshwater supply and the geographic isolation of the state place limits on other productive activities. Despite the aridity, the natural vegetation of BCS is diverse and structurally complex with a high percentage (20%) of endemic species. In this work we compare the environmental impacts produced by two kinds of aquaculture systems: coastal ponds vs. inland ponds. Construction and operation of coastal ponds does not require destruction of the natural vegetation and, as is true for inland ponds. Coastal ponds are also compatible with conservation of mangroves, sea grasses and sensitive habitats for fish and mollusks. To reduce the negative impacts of aquaculture and to protect the vegetation of Baja California Sur, we recommend the use of coastal ponds for shrimp production. 相似文献
5.
The sensitivity of modeled ozone to the temporal distribution of point, area, and mobile source emissions in the eastern United States 总被引:1,自引:0,他引:1
Patricia Castellanos Jeffrey W. Stehr Russell R. Dickerson Sheryl H. Ehrman 《Atmospheric environment (Oxford, England : 1994)》2009,43(30):4603-4611
Ozone remains one of the most recalcitrant air pollution problems in the US. Hourly emissions fields used in air quality models (AQMs) generally show less temporal variability than corresponding measurements from continuous emissions monitors (CEM) and field campaigns would imply. If emissions control scenarios to reduce emissions at peak ozone forming hours are to be assessed with AQMs, the effect of emissions' daily variability on modeled ozone must be understood. We analyzed the effects of altering all anthropogenic emissions' temporal distributions by source group on 2002 summer-long simulations of ozone using the Community Multiscale Air Quality Model (CMAQ) v4.5 and the Carbon Bond IV (CBIV) chemical mechanism with 12 km resolution. We find that when mobile source emissions were made constant over the course of a day, 8-h maximum ozone predictions changed by ±7 parts per billion by volume (ppbv) in many urban areas on days when ozone concentrations greater than 80 ppbv were simulated in the base case. Increasing the temporal variation of point sources resulted in ozone changes of +6 and −6 ppbv, but only for small areas near sources. Changing the daily cycle of mobile source emissions produces substantial changes in simulated ozone, especially in urban areas at night; results suggest that shifting the emissions of NOx from day to night, for example in electric powered vehicles recharged at night, could have beneficial impacts on air quality. 相似文献
6.
This case study details the difficulties of landscape management, highlighting the challenges inherent in managing natural resources when multiple agencies are involved, when the land users have no incentive for conservation, and when government agencies have too few resources for effective management. Pumping of groundwater from the aquifer of La Costa de Hermosillo in the state of Sonora, Mexico, began in 1945 and developed so quickly that by the late 1950s salinity intrusion from the Gulf of California was occurring in the wells. In the 1970s, the irrigatable land in La Costa peaked at 132,516 ha and the extracted volume of water from the aquifer peaked at around 1.14 billion cubic meters annually. By the 1980s, 105 wells of the total of 498 were contaminated with seawater and, therefore, identified for closure. At present La Costa de Hermosillo still represents 15% of the total harvested land, 16% of the total annual production, and 23% of the gross agricultural production of the state of Sonora. However,
there are approximately 80,000 ha of abandoned fields due to salt water intension, lack of water
and/or lack of credit available to individual farmers. This unstable situation resulted from the interplay of water management policies and practices, and farm-land policies and practices. While government agencies have been able to enforce better water use for agricultural production, there remains a significant area that requires restoration from its degraded state. For this piece of the ecosystem management puzzle, government agencies have thus far been unable to affect a solution. 相似文献
7.
Adaptation in a multi-stressor environment: perceptions and responses to climatic and economic risks by coffee growers in Mesoamerica 总被引:2,自引:0,他引:2
Hallie Eakin Catherine M. Tucker Edwin Castellanos Rafael Diaz-Porras Juan F. Barrera Helda Morales 《Environment, Development and Sustainability》2014,16(1):123-139
While climate change adaptation policy has tended to focus on planned adaptation interventions, in many vulnerable communities, adaptation will consist of autonomous, “unplanned” actions by individuals who are responding to multiple simultaneous sources of change. Their actions are likely not only to affect their own future vulnerability, but, through changes in livelihoods and resource use, the vulnerability of their community and resource base. In this paper, we document the autonomous changes to livelihood strategies adopted by smallholder coffee farmers in four Mesoamerican countries (Mexico, Guatemala, Honduras, and Costa Rica). Our aim is to gain insight into the process of autonomous adaptation by proxy: through an assessment of how farmers explain their choices in relation to distinct stressors; and an understanding of the set of choices available to farmers. We find that climatic stress is a feature in decision making, but not the dominant driver. Nevertheless, the farmers in our sample are evidently flexible, adaptive, and experimental in relation to changing circumstances. Whether their autonomous responses to diverse stressors will result in a reduction in risk over time may well depend on the extent to which policy, agricultural research, and rural investments build on the inherent logic of these strategies. 相似文献
8.
Manuel M. Reglero Mark A. Taggart Pilar Castellanos Rafael Mateo 《Environmental pollution (Barking, Essex : 1987)》2009,157(8-9):2209-2215
We studied the effects of elevated heavy metal uptake on the sperm quality and the antioxidant mechanisms of sperm and testis of red deer from a Pb mining area in Spain. Testis, liver and bone of red deer from mining (n = 21) and control (n = 20) areas were obtained from hunters and analyzed for Pb, Zn, Cu, Cd, As and Se. Testes were weighed and measured. Motility, acrosome integrity and viability and functionality of membrane were evaluated in epididymal spermatozoa. Lipid peroxidation, total glutathione, glutathione peroxidase (GPX) and superoxide dismutase (SOD) were studied in testis and spermatozoa. Deer from mined areas showed less Cu in testis, a higher testis mass and size and reduced spermatozoa membrane viability and acrosome integrity. Effects on sperm quality were associated to decreased Cu and increased Se in testis, and to decreases in the activity of SOD and GPX in testis and spermatozoa. 相似文献
9.
J. M. Castillo C. J. Luque E. M. Castellanos M. E. Figueroa 《Journal of Coastal Conservation》2000,6(1):89-96
This study reports on the quantification of horizontal erosion by undermining of slopes in the atlantic mesotidal salt marshes
of Odiel, SW Spain, and analyses its causes and consequences. Horizontal erosion has produced considerable losses of salt
marsh area, including zones of mature salt marsh. Human pressure, such as from water-borne traffic or the exploitation of
the slopes for the capture of bait, increases the natural erosion processes. The role of vegetation in protecting the slopes
against erosion is studied. Channel banks covered with plants, many of which belong to species with long-living, above-ground
creeping stems, were less eroded than those without vegetation cover. The enormous volume of sediments moved (ca. 7000m3 in one year) could contribute to the silting-up of the navigable channels of the estuary, so that continual dredging is necessary
to allow access to shipping. These sediments are highly contaminated, and dredging exposes them more directly to the trophic
network of the estuary. There is a considerable loss of natural resources. Finally, the integrated management of this coastal
ecosystem is discussed. 相似文献
10.
Pilar Castellanos Manuel M. Reglero Milagros C. Esteso María R. Fernández-Santos José J. Garde 《毒物与环境化学》2013,95(6):1163-1175
The sperm quality and several parameters associated with oxidative stress were evaluated in ram (Ovis aries) spermatozoa suspensions incubated with 0, 50 or 500 ng/mL Pb during 0, 1, 3 or 6 h. The presence of Pb during incubation, reduced the integrity of the acrosome, % sperm motility and integrity, and the functionality of membrane. On the contrary, % polyunsaturated fatty acids and the activities of glutathione peroxidase and superoxide dismutase in the spermatozoa suspensions were not affected by Pb. Moreover, glutathione peroxidase activity was decreased and the fatty acid composition changed due to the relative increase in % stearic acid during the incubation time independently on Pb presence. Data showed that several effects of Pb on sperm quality usually observed in vivo also occurred in vitro, but without any relationship with oxidative stress biomarkers. 相似文献