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41.
It is well known that arboreal ants, both territorially dominant species and plant ants (e.g., species associated with myrmecophytes or plants housing them in hollow structures), protect their host trees from defoliators. Nevertheless, the presence of an induced defense, suggested by the fact that the workers discovering a leaf wound recruit nestmates, is only known for plant ants. Based on the results from a field study, we show here (1) that colonies of Azteca chartifex, a territorially dominant, neotropical arboreal ant species, mostly selected Goupia glabra (Goupiaceae) trees in which to build their principal carton nests and (2) that plant signals induced workers to recruit nestmates, which patrol the leaves, likely providing the plant with a biotic defense. Furthermore, the number of recruited workers was clearly higher on G. glabra, their most frequently selected host tree species, than on other tree species. These results show that contrary to what was previously believed, induced responses are also found in territorially dominant arboreal ants and so are not limited to the specific associations between myrmecophytes and plant ants. 相似文献
42.
A quarry is a surface mining operated place, which produces enormous quantities of gravel, limestone, and other materials for industrial and construction applications. Restoration and revegetation of deserted quarries are becoming increasingly important. Three areas of a typical quarry in South China: terrace for crushed materials (terrace), spoiled mound, and remaining side slope, were investigated, to compare the existing plant species and to study the relationship between environmental factors and revegetation. The plant species composition of these three areas was found to differ significantly after eight years of natural recovery. The typical plant communities found over them were composed of gramineous herbs, fems, and shrubs. Soil organic matter, soil moisture, and soil bulk density were considered to be the major determining factors for vegetation succession. There existed abiotic and biotic thresholds during quarrying restoration. Suggestions had been presented that could have accelerated the process of natural recovery in quarries. 相似文献
43.
好氧反硝化菌的脱氮特性研究与探讨 总被引:2,自引:0,他引:2
本论文对好氧反硝化菌株FR2,FX5,FW4在好氧条件下的反硝化特性进行了研究。结果表明:反硝化主要发生在菌体的对数生长期,且反硝化过程中NO2^--N有少量的积累。
对不同温度、pH、碳源对好氧反硝化作用的影响进行了研究,结果表明:该三株菌在好氧条件下均具有良好的反硝化效果;温度为25℃~30℃的中性和微碱性条件反硝化效果较好;以乙酸钠为碳源的反硝化效果最好,NO3^-N的去除率最高。以葡萄糖为碳源的反硝化效果最差,NO3^-N的去除率最低。 相似文献
44.
Marion Valeix Hervé Fritz Andrew J. Loveridge Zeke Davidson Jane E. Hunt Felix Murindagomo David W. Macdonald 《Behavioral ecology and sociobiology》2009,63(10):1483-1494
A central question in the study of predator–prey relationships is to what extent prey behaviour is determined by avoidance
of predators. Here, we test whether the long-term risk of encountering lions and the presence of lions in the vicinity influence
the behaviour of large African herbivores at waterholes through avoidance of high-risk areas, increases in group size, changes
in temporal niche or changes in the time spent in waterhole areas. In Hwange National Park, Zimbabwe, we monitored waterholes
to study the behaviour of nine herbivore species under different risks of encountering lions. We radio-collared 26 lions in
the study area which provided the opportunity to monitor whether lions were present during observation sessions and to map
longer-term seasonal landscapes of risk of encountering lions. Our results show that the preferred prey species for lions
(buffalo, kudu and giraffe) avoided risky waterholes. Group size increased as encounter risk increased for only two species
(wildebeest and zebra), but this effect was not strong. Interestingly, buffalo avoided the hours of the day which are dangerous
when the long-term and short-term risks of encountering lions were high, and all species showed avoidance of waterhole use
at night times when lions were in the vicinity. This illustrates well how prey can make temporal adjustments to avoid dangerous
periods coinciding with predator hunting. Additionally, many herbivores spent more time accessing water to drink when the
long- and short-term risks of encountering lions were high, and they showed longer potential drinking time when the long-term
risk of encountering lions was high, suggesting higher levels of vigilance. This study illustrates the diversity of behavioural
adjustments to the risk of encountering a predator and how prey respond differently to temporal variations in this risk. 相似文献
45.
"二重源解析"模型计算结果的误差是采样误差、样品处理误差、化学组分分析误差、数据处理误差以及数学模型误差等所有误差的积累。提出了"二重源解析"解析结果的相对误差和标准偏差表达式,并用之计算了某市利用"二重源解析"模型计算的源贡献值的相对误差和标准偏差,还针对从源排放出来的初始态颗粒物在传输过程中发生的扬尘态变化提出了扬尘转化率的概念和计算方法。 相似文献
46.
The cause-and-effect relationships existing in freshwater biogeocenoses and changing with time are conventionally divided into three groups: direct, directly mediated, and indirect. The possibility of using the indirect relationships for the control over natural systems is exemplified by a new scheme of eutrophication control and water quality improvement. 相似文献
47.
48.
内分泌扰乱化学品对动物的影响和作用机制 总被引:46,自引:5,他引:41
介绍了内分泌扰乱化学品(EDCs)的作用机制及其对野生动物影响的研究进展。内分泌化学品可能与性激素受体、甲状腺素受体和其他受体(如芳烃受体)结合,也可能通过影响动物体内激素的代谢而对动物的生长发育起调控作用。各实验室的重复实验不支持环境雌激素之间存在协同作用的结论。已报道过的人体和野生动物生殖缺陷中具有充分证据的暴露-效应关系的实例为数不多。尽管野生鱼类变性是英国河流中的一个普遍现象,但进一步的实验证明污水处理场出水中的天然和合成雌激素足以引起鱼类的变性反应,而不是先前怀疑的非离子表面活性剂降解产物。目前尚不能对EDCs对人体和野生动物的健康风险作出正确评价,并有待于进一步研究。 相似文献
49.
50.
The horizontal distribution and quantitative characteristics of macrozoobenthos were studied in small lakes of the Darwin Nature Reserve (southern Vologda oblast). The aggregation index varied in the open areas of acid lakes, which indicated that communities of small acid water bodies were unstable. The aggregation was the lowest in the open area of a neutral lake. In acid lakes, the number and biomass of macroinvertebrates were the highest near the coasts. In the neutral lake, conversely, these values were maximum in open areas and low near the coast due to a strong pressure of predatory invertebrates and fish. An aggregating effect of invertebrate predators was observed near the coasts of lakes of different types. 相似文献