Condition-specific competition in container mosquitoes: the role of noncompeting life-history stages

Condition-specific competition, wherein competitive superiority varies with the abiotic environment, can determine species' distributions in a spatially heterogeneous environment. We investigated this phenomenon with two competing container-dwelling mosquitoes. We tested the hypothesis that habitat drying alters the outcome of interspecific competition, predicting that the competitive impact of Aedes albopictus on Aedes aegypti would be severe in wetter environments, but greatly reduced in drier environments. We tested these predictions in a laboratory experiment within cages, with aquatic larvae residing in water-filled cups within the cage, and adults emerging within the cage and ovipositing on the cups. We raised each species alone or with the competitor. Environmental treatments were fluctuating (water in cups evaporated to 50% of the original volume and then cups were refilled), and drying (water in cups evaporated completely and cups remained dry for two weeks before refilling). There was a significant interaction between treatment and species combination for adult populations of both species. Interspecific competition was highly asymmetrical. In the wetter fluctuating environment, interspecific competition had a large negative effect on A. aegypti, but in the drying environment, interspecific competition had a large negative effect on A. albopictus, and relatively little impact on A. aegypti. The main cause of the shift in competitive advantage appeared to be a greater increase in egg mortality for A. albopictus under dry conditions, compared to A. aegypti. Thus, mortality impinging on noncompeting life cycle stages can alter the population level impact of interspecific competition. The hypothesis that dry conditions shift competitive advantage away from A. albopictus is supported in this experiment.     

Reproductive Investment of a Lacertid Lizard in Fragmented Habitat

Abstract:  We studied the effect of habitat fragmentation on female reproductive investment in a widespread lacertid lizard (  Psammodromus algirus ) in a mixed-forest archipelago of deciduous and evergreen oak woods in northern Spain. We captured gravid females in fragments (≤10 ha) and forests (≥ 200 ha) and brought them to the laboratory, where they laid their eggs. We incubated the eggs and released the first cohort of juveniles into the wild to monitor their survival. Females from fragments produced a smaller clutch mass and laid fewer eggs (relative to mean egg mass) than females of similar body size from forests. Lizards did not trade larger clutches for larger offspring, however, because females from fragments did not lay larger eggs (relative to their number) than females from forests. Among the first cohort of juveniles, larger egg mass and body size increased the probability of recapture the next year. Thus, fragmentation decreased the relative fecundity of lizards without increasing the quality of their offspring. Reduced energy availability, increased predation risk, and demographic stochasticity could decrease the fitness of lizards in fragmented habitats, which could contribute to the regional scarcity of this species in agricultural areas sprinkled with small patches of otherwise suitable forest. Our results show that predictable reduction of reproductive output with decreasing size of habitat patches can be added to the already known processes that cause inverse density dependence at low population numbers.     

Measurement of radon,thoron and their daughters in the air of marble factories and resulting alpha-radiation doses to the lung of workers

Concentrations of radon (²²²Rn) and thoron (²²⁰Rn) were measured in the air of different marble factories by using a nuclear track technique. The influence of the marble dust nature and ventilation on radon and thoron concentrations was investigated. It was observed that measured radon and thoron concentration ranged from 310 to 903 Bq m⁻³ and 6 to 48 Bq m⁻³, respectively. In addition, alpha-activities due to the unattached and attached fractions of ²¹⁸Po and ²¹⁴Po radon short-lived progeny were evaluated in the marble factories studied. Committed equivalent doses due to the attached and unattached fractions of ²¹⁸Po and ²¹⁴Po nuclei were evaluated in the lung tissues of marble factory workers. The dependence of the resulting committed equivalent dose on the concentration of the attached and unattached fractions of the ²¹⁸Po and ²¹⁴Po radionuclides and mass of the tissue was investigated. The resulting annual committed effective doses to the lung of marble factory workers due to the attached and unattached fractions of the ²¹⁸Po and ²¹⁴Po radionuclides were calculated. The obtained results show that about 80% of the global committed effective doses received by workers in the studied marble factories are due to the attached fraction of the ²¹⁸Po and ²¹⁴Po radon short-lived daughters from the inhalation of polluted air. Male workers spending 8 h per day (2080 h per year) in a marble factory receive a maximum dose of 34.46 mSv y⁻¹ which is higher than the (3–10 mSv y⁻¹) dose limit interval given by the ICRP. Good agreement was found between data obtained for the average effective dose gotten by using this method and the UNSCEAR and ICRP conversion dose coefficients.

     

Effects of law enforcement and community outreach on mammal diversity in a biodiversity hotspot

Management activities such as law enforcement and community outreach are thought to affect conservation outcomes in protected areas, but their importance relative to intrinsic environmental characteristics of the parks and extrinsic human pressures surrounding the parks have not been explored. Furthermore, it is not clear which is more related to conservation outcomes—the management itself or local people's perceptions of the management. We measured objective (reports by park staff) and subjective (reports by local people) levels of community outreach and law enforcement based on responses to 374 questionnaires. We estimated mammal abundance and diversity of 6 protected areas based on data from 115 camera traps in Xishuangbanna, southwest China, a biodiversity hotspot with high hunting and land-conversion pressures. We then examined correlations among them and found that local people's perception of law enforcement was positively related to the local abundance of 2 large, hunted species, wild boar (Sus scrofa) (β = 15.22) and muntjac (Muntiacus vaginalis) (β = 14.82), but not related to the abundance of smaller mammals or to objective levels of enforcement. The subjective frequency of outreach by park staff to local communities (β = 3.42) and park size (β = 3.28) were significantly and positively related to mammal species richness, whereas elevation, human population density, and subjective frequency of law enforcement were not. We could not conclude that community outreach and law enforcement were directly causing increased mammal abundance and diversity. Nevertheless, the patterns we detected are some of the first empirical evidence consistent with the idea that biodiversity in protected areas may be more positively and strongly related to local perceptions of the intensity of park management than to either intrinsic (e.g., elevation, park size) or extrinsic (e.g., human population density) environmental factors.     

火山灰年代学与地层学研究简述

火山灰的研究作为探讨古气候和古环境的一种手段,近十年来引起了国内外学者的广泛关注。气候学和古环境学的研究表明,火山喷发可以导致某一区域内短期的气候变化或者对冰期产生强烈影响。同时,火山灰层的成因机制决定了其空间分布的等时性和广泛性,因此,火山灰的地层学特征和精确定年,具有重要的地层对比意义。目前,全球各地已经开展了许多火山灰年代学与地层学的研究。在中国,尤其是东北地区,虽然有着丰富的火山资源,但是火山灰年代学与地层学的研究工作依然比较匮乏,本文简要回顾了一下中国东北、欧洲、新西兰、日本、俄罗斯等地区的火山灰研究工作,旨在为以后的研究提供一定的参考资料。     

近期和长远时段内北极生态系统功能受到的影响

长期以来,就营养物质和碳循环而言,北极生态系统降低了初级生产力；能量,水和温室气体交换的水平已引起了局部和区域性的小幅度降温.大气CO2中的碳沉积在广袤而寒冷的有机土壤中,冰雪覆盖的低矮植被产生高的反射率,都影响了局部气候.然而,北极生态系统功能的许多方面都对气候变化及其产生的生物多样性影响敏感.当前的北极气候导致了低的有机物质分解速率,因此,尽管有机物和元素输入量较低,但北极生态系统还是趋向于积累有机物和元素,土壤中氮和磷等可利用元素结果成为促进碳固定以及生物量和有机物进一步积累的关键性限制因素.气候变暖可能增加特别是土壤中的碳和元素的周转,起初可能导致元素的丢失,但最后会慢慢的恢复.在北极生态系统中,单个物种和物种多样性已经明显地影响了元素的输入和滞留,另一方面,从长远来看,尽管CO2和紫外线增加对植物组织化学、分解和氮固定的影响可能变得重要,但对整个生态系统来说,影响可能很小.碳循环的示踪气体主要形式是CO2和CH4,大多数碳以CO2的形式损失,这些CO2是由植物和土壤生物产生.来自潮湿苔原生态系统以CH4形式释放的碳大约是CO2形式的5％,而且在没有任何其他变化的情况下,对变暖作出响应.冬天过程和植物类型也影响CH4释放和能量在生物圈和大气之间的交换,因为反射率从冬末到夏天存在很大的变化,在冬末,雪反射了入射的大部分光线,在夏天,生态系统吸收了入射的大部分光线,所以在所有的陆地生态系统中,北极生态系统在能量交换方面表现出巨大的季节性变化.植被深刻地影响北极生态系统水和能量交换.在冰雪覆盖期间,反射率从苔原、森林苔原、落叶林、常绿林依次降低.灌木和树增加了雪的深度,反过来又使冬天的土壤温度增加,因此,由气候变化而引起的未来植被方面的变化很可能深远地改变区域的气候.