| 1 | Feeding habitats of blue sheep(Pseudois nayaur)during winter and spring in Helan Mountains,China显示文摘The feeding habitat selection of blue sheep(Pseudois nayaur)was studied by direct observation method in the Helan Mountains,China during winter(from Novembe r to December)and spring(from April to June)from 2003 to 2004.We established 25 line transects to collect information on feeding habitats used by blue sheep.Blue sheep in the study area preferred mountain savanna forests,a habitat dominated by Ulmus glaucescens,with medium tree density(<4 individuals/400 m^(2)),moderate tree height(4-6 m),higher shrub density(>5 individuals/100 m^(2)),higher shrub(>1.3 m),higher food abundance(>50 g),moderate distance to human disturbance(<500 m),and mild distance to bare rock(<2 m).Such habitats characterized by 12 ecological factors were preferred as feeding areas by blue sheep during winter.Similar to habitat selection by the species during winter,blue sheep also showed a preference for mountain savanna with tree dominated by Ulmus glaucescens and medium tree density(<4 individuals/400 m^(2))during spring.Nevertheless,blue sheep preferred medium tree height(<6 m),moderate tree density(5-10 individuals/100 m^(2)),medium shrub height(1.3-1.7 m),higher food abundance(>100 g),moderate altitude(<2000 m),moderate distance to water resource(<500 m),and medium hiding cover(50%-75%)during spring.Selection of the feeding habitats by sheep showed a significant difference in vegetation type,landform feature,dominant tree,tree height,shrub density,distance to the nearest shrub,food abundance,slope direc-tion,slope degree,distance to water resource,and hiding cover between winter and spring.Results of principal com-ponents analysis indicated that the first principal component accounted for 24.493%of the total variance among feeding habitat variance during winter,with higher loadings for vegetation type,dominant tree,tree height,distance to the nearest tree,shrub density,shrub height,altitude,distance to water resource,and distance to human disturbance.In spring,the first principal components explained 28.777%of the vari-ance,with higher loadings for vegetation type,distance to the nearest tree,shrub height,distance to the nearest shrub,food abundance,altitude,and distance to human disturbance. | LIU Zhensheng WANG Xiaoming LI Zhigang CUI Duoying LI Xinqing | 2007 | Frontiers in Biology2007，2，1： | 0 |
| 2 | Arctic sea ice and atmospheric circulation under the abrupt4xCO2 scenario显示文摘We analyze sea ice changes from eight different earth system models that have conducted experiment abrupt4xCO2 of the Coupled Model Intercomparison Project Phase 5(CMIP5). In response to abrupt quadrupling of CO2 from preindustrial levels, Arctic temperatures dramatically rise by about 10°C—16°C in winter and the seasonal sea ice cycle and sea ice concentration are significantly changed compared with the pre-industrial control simulations(pi Control). Changes of Arctic sea ice concentration are spatially correlated with temperature patterns in all seasons and highest in autumn. Changes in sea ice are associated with changes in atmospheric circulation patterns at heights up to the jet stream. While the pattern of sea level pressure changes is generally similar to the surface air temperature change pattern, the wintertime 500 h Pa circulation displays a positive Pacific North America(PNA) anomaly under abrupt4xCO2-pi Control. This large scale teleconnection may contribute to, or feedback on, the simulated sea ice cover change and is associated with an intensification of the jet stream over East Asia and the north Pacific in winter. | YU Xiaoyong Annette Rinke JI Duoying CUI Xuefeng John C.Moore | 2014 | Advances in Polar Science2014，25，4： | 0 |
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