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861.
Masting mediated by summer drought reduces acorn predation in Mediterranean oak forests 总被引:1,自引:0,他引:1
Temporally variable production of seed crops by perennial plants (masting) has been hypothesized to be a valuable mechanism in the reduction of seed predation by satiating and starving seed consumers. To achieve these benefits, coexisting species subjected to the same predator would benefit from a similar pattern of seeding fluctuation over time that could lead to a reduction in predation at the within-species level. We tested for the existence of an environmental factor enforcing synchrony in acorn production in two sympatric Mediterranean oaks (Quercus ilex and Q. humilis) and the consequences on within-species and between-species acorn predation, by monitoring 15 mixed forests (450 trees) over seven years. Acorn production in Q. ilex and Q. humilis was highly variable among years, with high population variability (CVp) values. The two species exhibited a very different pattern across years in their initial acorn crop size (sum of aborted, depredated, and sound acorns). Nevertheless, interannual differences in summer water stress modified the likelihood of abortion during acorn ripening and enforced within- and, particularly, between-species synchrony and population variability in acorn production. The increase in CVp from initial to mature acorn crop (after summer) accounted for 33% in Q. ilex, 59% in Q. humilis, and 60% in the two species together. Mean yearly acorn pre-dispersal predation by invertebrates was considerably higher in Q. humilis than in Q. ilex. Satiation and starvation of predators was recorded for the two oaks, and this effect was increased by the year-to-year variability in the size of the acorn crop of the two species combined. Moreover, at a longer time scale (over seven years), we observed a significant reduction in the mean proportion of acorns depredated for each oak and the variability in both species' acorn production combined. Therefore, our results demonstrate that similar patterns of seeding fluctuation over time in coexisting species mediated by an environmental cue (summer drought) may contribute to the reduction of the impact of seed predation at a within-species level. Future research should be aimed at addressing whether this process could be a factor assisting in the coexistence of Q. ilex and Q. humilis. 相似文献
862.
Gilad Heinisch Aldo Corriero Antonio Medina Francisco J. Abascal Jose-Miguel de la Serna Robert Vassallo-Agius Antonio Belmonte Ríos Antonio García Fernando de la Gándara Christian Fauvel Christopher R. Bridges Constantinos C. Mylonas Saadet F. Karakulak Isik Oray Gregorio De Metrio Hanna Rosenfeld Hillel Gordin 《Marine Biology》2008,154(4):623-630
Atlantic bluefin tuna (BFT; Thunnus thynnus) is a migrating species straddling the North Atlantic Ocean and Mediterranean Sea. It is assumed that this species is divided
into a western and an eastern stock, which spawn in the Gulf of Mexico and the Mediterranean Sea, respectively. To learn more
about the reproductive behavior of the eastern BFT stock, we tracked gonadal development in adult fish that were sampled between
April and July during three consecutive years (2003–2005). Sampling campaigns were carried out using common fishing methods
at selected locations within the Mediterranean Sea, namely Levantine Sea, Malta, and Balearic Islands. An additional sampling
point, Barbate, was situated northwest of the Straits of Gibraltar along the Atlantic coast. Morphometric parameters such
as the total body mass (M
B) and the weights of the gonads (M
G) were recorded, and the respective gonadosomatic index (GSI) values were calculated. The data collected revealed two important
trends: (1) GSI values are higher in fish caught in the eastern rather than the western locations across the Mediterranean
Sea, and (2) the GSI reaches maximum values between late May and early June in Levantine Sea (eastern Mediterranean Sea),
and only 2 and 4 weeks later in the central (Malta) and western (Balearic Islands) locations, respectively. The advanced gonadal
development in BFT correlates well with higher sea surface temperatures. Our findings also distinguish the northern Levantine
Sea BFT population (mean M
B 78.41 ± 4.13 kg), and the Barbate BFT population with the greatest M
B (all fish sampled > 100 kg). These data reflect a situation in which the eastern Mediterranean basin may function as a habitat
for young BFT, until they gain a larger M
B and are able to move to the Atlantic Ocean. However, the existence of genetically discrete BFT populations in the Mediterranean
Sea cannot be ruled out. 相似文献
863.
An important consideration in conservation and biodiversity planning is an appreciation of the condition or integrity of ecosystems. In this study, we have applied various machine learning methods to the problem of predicting the condition or quality of the remnant indigenous vegetation across an extensive area of south-eastern Australia—the state of Victoria. The field data were obtained using the ‘habitat hectares’ approach. This rapid assessment technique produces multiple scores that describe the condition of various attributes of the vegetation at a given site. Multiple sites were assessed and subsequently circumscribed with GIS and remote-sensed data. 相似文献
864.
Pedro Daleo Tomás Luppi Agustina Mendez Casariego Mauricio Escapa Pablo Ribeiro Paola Silva Oscar Iribarne 《Marine Biology》2009,156(3):269-275
Size advantage in male–male competition over mates, combined with male preference over large females, is a common feature
that can drive to size assortative mating and, eventually, sexual selection. In crabs, appendage autotomy can affect assortative
mating and opportunity for sexual selection by affecting size advantage in mating contests. In this work, we evaluate the
effect of size and appendage autotomy in generating assortative mating in the mud crab Cyrtograpsus angulatus. Field observations of guarding pairs in two different populations show a positive correlation between carapace width of
males and females in both the populations. In one of the populations, incidence of appendage autotomy was low and the variability
in the size of reproductive males was lower than the variability in the size of randomly collected males (i.e. only larger
males were successful in getting a female), whereas there was no differences in the other population (i.e. most male sizes
were successful) where the incidence of appendage autotomy was very high, indicating that the importance of size is higher
when the incidence of autotomy is low. In this context, experiments (in both populations) show that, in contests for a female,
larger males outcompete smaller ones only when they had intact appendages. When males had missing chelipeds, winning or loosing
against smaller males was random. This may lead to a decrease in the importance of male size in populations with high incidence
of cheliped autotomy, affecting assortative mating and opportunity for selection and, thus, affecting selective pressures. 相似文献
865.
Marcela González Cristina Dapeña Bibiana Cerne Odon Sánchez-Ccoyllo Saulo Freitas Pedro L. Silva Dias Héctor Panarello 《Environmental Fluid Mechanics》2009,9(4):409-425
The SALLJEX experiment was held during the summer 2002–2003. It consisted of three-dimensional observation of the atmosphere
to study the structure of the low level jet along the eastern slopes of the Andes. Daily precipitation water samples were
collected at two stations (Resistencia and Salta) in northern Argentina and isotope content was analyzed. The isotope data
were used in conjunction with air parcel trajectories obtained from a 3-D kinematic model (3D-MTC) developed by the University
of Sao Paulo, Brazil. Values of deuterium excess were related with air masses of continental origin, whilst low values were
associated with air masses with longer oceanic trajectories. Furthermore, although data are scarce, results show that oxygen-18
and deuterium excess in rainwater are related with the occurrence of the low level jet. 相似文献
866.
Rapant S Cvecková V Dietzová Z Khun M Letkovicová M 《Environmental geochemistry and health》2009,31(1):11-25
This study presents an assessment of the potential impact of geological contamination of the environment on the health of
the population in Spišsko-Gemerské rudohorie Mts. (SGR Mts.). The concentration levels of potentially toxic elements (mainly
As, Cd, Cu, Hg, Pb, Sb, and Zn) were determined in soils, groundwater, surface water, and stream sediments as well as in the
food chain (locally grown vegetables). A medical study included some 30 health indicators for all 98 municipalities of the
study area. The As and Sb contents in human fluids and tissues were analyzed in one municipality identified to be at the highest
risk. Based on element content, environmental and health risks were calculated for respective municipalities. Out of 98 municipalities
14 were characterized with extremely high environmental risk and 10 were characterized with very high carcinogenic risk from
arsenic (groundwater). Extensive statistical analysis of geochemical data (element contents in soils, groundwater, surface
water, and stream sediments) and health indicators was performed. Significant correlations between element contents in the
geological environment and health indicators, mainly cancer and cardiovascular diseases, were identified. Biological monitoring
has confirmed the transfer of elements from the geological environment to human fluids and tissues as well as to the local
food chain. 相似文献
867.
Sales of electrical and electronic equipment are increasing dramatically in developing countries. Usually, there are no reliable data about quantities of the waste generated. A new law for solid waste management was enacted in Brazil in 2010, and the infrastructure to treat this waste must be planned, considering the volumes of the different types of electrical and electronic equipment generated.This paper reviews the literature regarding estimation of waste electrical and electronic equipment (WEEE), focusing on developing countries, particularly in Latin America. It briefly describes the current WEEE system in Brazil and presents an updated estimate of generation of WEEE. Considering the limited available data in Brazil, a model for WEEE generation estimation is proposed in which different methods are used for mature and non-mature market products.The results showed that the most important variable is the equipment lifetime, which requires a thorough understanding of consumer behavior to estimate. Since Brazil is a rapidly expanding market, the “boom” in waste generation is still to come. In the near future, better data will provide more reliable estimation of waste generation and a clearer interpretation of the lifetime variable throughout the years. 相似文献
868.
The use of organic municipal wastes as soil amendments is an increasing practice that can divert significant amounts of waste from landfill, and provides a potential source of nutrients and organic matter to ameliorate degraded soils. Due to the high heterogeneity of organic municipal waste streams, it is difficult to rapidly and cost-effectively establish their suitability as soil amendments using a single method. Thermal analysis has been proposed as an evolving technique to assess the stability and composition of the organic matter present in these wastes. In this study, three different organic municipal waste streams (i.e., a municipal waste compost (MC), a composted sewage sludge (CS) and a thermally dried sewage sludge (TS)) were characterized using conventional and thermal methods. The conventional methods used to test organic matter stability included laboratory incubation with measurement of respired C, and spectroscopic methods to characterize chemical composition. Carbon mineralization was measured during a 90-day incubation, and samples before and after incubation were analyzed by chemical (elemental analysis) and spectroscopic (infrared and nuclear magnetic resonance) methods. Results were compared with those obtained by thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques. Total amounts of CO2 respired indicated that the organic matter in the TS was the least stable, while that in the CS was the most stable. This was confirmed by changes detected with the spectroscopic methods in the composition of the organic wastes due to C mineralization. Differences were especially pronounced for TS, which showed a remarkable loss of aliphatic and proteinaceous compounds during the incubation process. TG, and especially DSC analysis, clearly reflected these differences between the three organic wastes before and after the incubation. Furthermore, the calculated energy density, which represents the energy available per unit of organic matter, showed a strong correlation with cumulative respiration. Results obtained support the hypothesis of a potential link between the thermal and biological stability of the studied organic materials, and consequently the ability of thermal analysis to characterize the maturity of municipal organic wastes and composts. 相似文献
869.
de Guzmán Báez A Villoria Sáez P del Río Merino M García Navarro J 《Waste management (New York, N.Y.)》2012,32(5):920-924
In the last years, the European Union (EU) has been focused on the reduction of construction and demolition (C&D) waste. Specifically, in 2006, Spain generated roughly 47million tons of C&D waste, of which only 13.6% was recycled. This situation has lead to the drawing up of many regulations on C&D waste during the past years forcing EU countries to include new measures for waste prevention and recycling. Among these measures, the mandatory obligation to quantify the C&D waste expected to be originated during a construction project is mandated. However, limited data is available on civil engineering projects. Therefore, the aim of this research study is to improve C&D waste management in railway projects, by developing a model for C&D waste quantification. For this purpose, we develop two equations which estimate in advance the amount, both in weight and volume, of the C&D waste likely to be generated in railway construction projects, including the category of C&D waste generated for the entire project. 相似文献
870.
Estimation of end of life mobile phones generation: the case study of the Czech Republic 总被引:2,自引:0,他引:2
The volume of waste electrical and electronic equipment (WEEE) has been rapidly growing in recent years. In the European Union (EU), legislation promoting the collection and recycling of WEEE has been in force since the year 2003. Yet, both current and recently suggested collection targets for WEEE are completely ineffective when it comes to collection and recycling of small WEEE (s-WEEE), with mobile phones as a typical example. Mobile phones are the most sold EEE and at the same time one of appliances with the lowest collection rate. To improve this situation, it is necessary to assess the amount of generated end of life (EoL) mobile phones as precisely as possible. This paper presents a method of assessment of EoL mobile phones generation based on delay model. Within the scope of this paper, the method has been applied on the Czech Republic data. However, this method can be applied also to other EoL appliances in or outside the Czech Republic. Our results show that the average total lifespan of Czech mobile phones is surprisingly long, exactly 7.99 years. We impute long lifespan particularly to a storage time of EoL mobile phones at households, estimated to be 4.35 years. In the years 1990-2000, only 45 thousands of EoL mobile phones were generated in the Czech Republic, while in the years 2000-2010 the number grew to 6.5 million pieces and it is estimated that in the years 2010-2020 about 26.3 million pieces will be generated. Current European legislation sets targets on collection and recycling of WEEE in general, but no specific collection target for EoL mobile phone exists. In the year 2010 only about 3-6% of Czech EoL mobile phones were collected for recovery and recycling. If we make similar estimation using an estimated average EU value, then within the next 10 years about 1.3 billion of EoL mobile phones would be available for recycling in the EU. This amount contains about 31 tonnes of gold and 325 tonnes of silver. Since Europe is dependent on import of many raw materials, efficient recycling of EoL products could help reduce this dependence. To set a working system of collection, it will be necessary to set new and realistic collection targets. 相似文献