This research was conducted at the sand dunes stabilization research s tation in Baiji district, Iraq. Three techniques for sand dunes stabilization ar e selected: the first method is stabilization by clayey block ba...This research was conducted at the sand dunes stabilization research s tation in Baiji district, Iraq. Three techniques for sand dunes stabilization ar e selected: the first method is stabilization by clayey block barriers; the seco nd method is stabilization by dry planting of tamarix (tamarix articulata) cutti ngs and the third is stabilization by using cane branch barriers. Randomized sam ples were taken from the surface and subsurface layers of the stabilized and shi fting sand dunes to evaluate the effect of the three techniques on wind erosion parameters. The results indicate high significant differences between the wind e rosion parameters in the surface and subsurface layers in the stabilized sand du nes, while there are insignificant differences between the subsurface layer of t he stabilized dunes and the surface and subsurface layers in the active sand dun es. The results clarify the fact that there is an increase in the percentage of clay, silt, organic matter, mean weight diameter and the percentage of the dry a ggregates (>0.84 mm). A decrease is found in the rate of disaggregation for the dry aggregates in the samples of the surface layer of stabilized dunes when comp ared with the subsurface layer of stabilized dunes and the surface layer of the shifting sand dunes. There is a positive high significant correlation among the aggregate stability parameters and the percentage of clay and silt, and the cont ent of organic matter in the studied layers.展开更多
Since 1988, the Japan Enoshima Aquarium (JEA) and the Institute of Hydrobiology of Chinese Academy of Sciences(IHCAS) have carried out long-term joint research on the conservation of Baiji dolphins (Lipotes vexillifer...Since 1988, the Japan Enoshima Aquarium (JEA) and the Institute of Hydrobiology of Chinese Academy of Sciences(IHCAS) have carried out long-term joint research on the conservation of Baiji dolphins (Lipotes vexillifer). According to the research, the population of Baiji dolphins has been decreasing rapidly from 300 in 1986 to less than 100 at present due to environmental deterioration of the Yangtze River. Since it is impossible to conserve the species in the river, as many as possible of the dolphins should be collected and transferred展开更多
Lipotes usually occurs in pairs or in small loose groups. The calves are born in March-April.The Finless porpoises are usually seen in groups of five or six individuals.The blowof Lipotes lasts 0.2--0.6 sec and that o...Lipotes usually occurs in pairs or in small loose groups. The calves are born in March-April.The Finless porpoises are usually seen in groups of five or six individuals.The blowof Lipotes lasts 0.2--0.6 sec and that of Neophocaena 0.2--0.5 sec. In Lipotes,a short divewould take 10--20 sec and a long dive up to 1--2 min (average value being 31 sec). InNeophocaena a long dive would reach a maximum of 65 sec with an average of 17.5 sec.Lipotes has a pair of functional eyes. The selective secondary atrophy of a number of eyemuscles and nerves and the position of the eyes in the head correspond with the physical con-ditions of the environments so that the field of vision is directed forwards and upwards. When pursued by motor boat, both species react with a long dive and a change of direc-tion under water. With the Baiji this would occasionally cause fatal injuries by thepropeller of the ship. Such a case seems much less often with Neophocaena. The populationof Lipotes is at present very small.In the stretch of the river (between Nanjing andTaiyangzhou) under exploration, we found scarcely more than one dolphin per 4 km. Thecause for its scarcity is mostly due to accidents or wounds caused by propellers.展开更多
The history of artificially rearing cetacean specieshas been over a hundred in the world. Rearing cetaceanspecies in captivity can supply not only a kind of interesting entertainment, but also good conditions for inte...The history of artificially rearing cetacean specieshas been over a hundred in the world. Rearing cetaceanspecies in captivity can supply not only a kind of interesting entertainment, but also good conditions for intensively researching, breeding and conserving展开更多
AT a conference of the World Whaling Commission in Cambridge, England, in 1981, a special video tape caught the attention of experts at the meeting. It was a tape about the artificial raising of Baiji ill China, broug...AT a conference of the World Whaling Commission in Cambridge, England, in 1981, a special video tape caught the attention of experts at the meeting. It was a tape about the artificial raising of Baiji ill China, brought by Chen Peixun, head of the Baiji Coordinative Group and a research fellow of the Institute of Hydrobiology, the Chinese Academy of Sciences. On the screen was a large mammal with a long, pointed mouth, swimming in the water with its belly up one moment and down the next. It looked like a dolphin,展开更多
文摘This research was conducted at the sand dunes stabilization research s tation in Baiji district, Iraq. Three techniques for sand dunes stabilization ar e selected: the first method is stabilization by clayey block barriers; the seco nd method is stabilization by dry planting of tamarix (tamarix articulata) cutti ngs and the third is stabilization by using cane branch barriers. Randomized sam ples were taken from the surface and subsurface layers of the stabilized and shi fting sand dunes to evaluate the effect of the three techniques on wind erosion parameters. The results indicate high significant differences between the wind e rosion parameters in the surface and subsurface layers in the stabilized sand du nes, while there are insignificant differences between the subsurface layer of t he stabilized dunes and the surface and subsurface layers in the active sand dun es. The results clarify the fact that there is an increase in the percentage of clay, silt, organic matter, mean weight diameter and the percentage of the dry a ggregates (>0.84 mm). A decrease is found in the rate of disaggregation for the dry aggregates in the samples of the surface layer of stabilized dunes when comp ared with the subsurface layer of stabilized dunes and the surface layer of the shifting sand dunes. There is a positive high significant correlation among the aggregate stability parameters and the percentage of clay and silt, and the cont ent of organic matter in the studied layers.
文摘Since 1988, the Japan Enoshima Aquarium (JEA) and the Institute of Hydrobiology of Chinese Academy of Sciences(IHCAS) have carried out long-term joint research on the conservation of Baiji dolphins (Lipotes vexillifer). According to the research, the population of Baiji dolphins has been decreasing rapidly from 300 in 1986 to less than 100 at present due to environmental deterioration of the Yangtze River. Since it is impossible to conserve the species in the river, as many as possible of the dolphins should be collected and transferred
文摘Lipotes usually occurs in pairs or in small loose groups. The calves are born in March-April.The Finless porpoises are usually seen in groups of five or six individuals.The blowof Lipotes lasts 0.2--0.6 sec and that of Neophocaena 0.2--0.5 sec. In Lipotes,a short divewould take 10--20 sec and a long dive up to 1--2 min (average value being 31 sec). InNeophocaena a long dive would reach a maximum of 65 sec with an average of 17.5 sec.Lipotes has a pair of functional eyes. The selective secondary atrophy of a number of eyemuscles and nerves and the position of the eyes in the head correspond with the physical con-ditions of the environments so that the field of vision is directed forwards and upwards. When pursued by motor boat, both species react with a long dive and a change of direc-tion under water. With the Baiji this would occasionally cause fatal injuries by thepropeller of the ship. Such a case seems much less often with Neophocaena. The populationof Lipotes is at present very small.In the stretch of the river (between Nanjing andTaiyangzhou) under exploration, we found scarcely more than one dolphin per 4 km. Thecause for its scarcity is mostly due to accidents or wounds caused by propellers.
文摘The history of artificially rearing cetacean specieshas been over a hundred in the world. Rearing cetaceanspecies in captivity can supply not only a kind of interesting entertainment, but also good conditions for intensively researching, breeding and conserving
文摘AT a conference of the World Whaling Commission in Cambridge, England, in 1981, a special video tape caught the attention of experts at the meeting. It was a tape about the artificial raising of Baiji ill China, brought by Chen Peixun, head of the Baiji Coordinative Group and a research fellow of the Institute of Hydrobiology, the Chinese Academy of Sciences. On the screen was a large mammal with a long, pointed mouth, swimming in the water with its belly up one moment and down the next. It looked like a dolphin,
