开放·边缘·民间——第四届人类学高级论坛之观察员评论

第四届人类学高级论坛所涉及的所有问题都具有人类学的学术价值。学者们认为人类学是一门开放的学科,中国人类学学者应放在开放的田野工作中提升和构建新的人类学理论。     

Response of sagebrush steppe species to elevated CO 2 and soil temperature

Elevated atmospheric CO 2 may cause long-term changes in the productivity and species composition of the sagebrush steppe. Few studies, however, have evaluated the effects of increased CO 2 on growth and physiology of species important to this ecosystem. Since the response of plants to elevated CO 2 may be limited by environmental factors, soil temperature was also examined to determine if low soil temperatures limit CO 2 response. To determine how CO 2 and soil temperature affect the growth of species native to the sagebrush steppe, bottlebrush squirreltail [ Elymus elymoides (Raf.) Swezey], Thurber needlegrass ( Stipa thurberiana Piper), and Wyoming big sagebrush ( Artemisia tridentata ssp. wyomingensis Beetle) were grown in ambient (374 mL L -1 ) or high (567 mL L -1 ) CO 2 and low (13° C) or high (18° C) soil temperature for approximately 4 months. Although soil temperature affected the growth of squirreltail and needlegrass, temperature did not modify their response to elevated CO 2 . Total biomass of sagebrush was consistent across soil temperature and CO 2 treatments, reflecting its slow-growing strategy. All 3 species had higher leaf water-use efficiency at elevated CO 2 due to higher net photosynthesis and lower transpiration rates. We conclude that elevated CO 2 and soil warming may increase the growth of grasses more than shrubs. Field studies in the sagebrush steppe are necessary to determine if differences in biomass, resulting from changes in CO 2 and soil temperature, are exhibited in the field.     

孤岛油田馆(1+2)地层划分对比与沉积模式

孤岛油田馆(1 2)砂层组属于河流相沉积，其纵向、横向相变迅速，砂体难以大面积追踪，本利用河流结构单元分析法、标准层与辅助标志层控制下的“旋回-厚度”对比法，很好地解决了馆(1 2)地层的划分对比问题，其中馆(1 2)砂层组内辅助标志层的发现为地层的划分对比提供了重要的保证．根据结构单元分析、砂体的岩性特征、粒度特征、河流砂体的空间展布形态以及河流曲率的计算，对馆(1 2)河流沉积的垂向旋回性及沉积模式进行了研究。对比Miall的16种河流分类方案，孤岛油田馆(1 2)砂层组属于细粒曲流河沉积．     

Recent decreases in fossil-fuel emissions of ethane and methane derived from firn air

Methane and ethane are the most abundant hydrocarbons in the atmosphere and they affect both atmospheric chemistry and climate. Both gases are emitted from fossil fuels and biomass burning, whereas methane (CH(4)) alone has large sources from wetlands, agriculture, landfills and waste water. Here we use measurements in firn (perennial snowpack) air from Greenland and Antarctica to reconstruct the atmospheric variability of ethane (C(2)H(6)) during the twentieth century. Ethane levels rose from early in the century until the 1980s, when the trend reversed, with a period of decline over the next 20?years. We find that this variability was primarily driven by changes in ethane emissions from fossil fuels; these emissions peaked in the 1960s and 1970s at 14-16 teragrams per year (1?Tg = 10(12)?g) and dropped to 8-10?Tg yr(-1) by the turn of the century. The reduction in fossil-fuel sources is probably related to changes in light hydrocarbon emissions associated with petroleum production and use. The ethane-based fossil-fuel emission history is strikingly different from bottom-up estimates of methane emissions from fossil-fuel use, and implies that the fossil-fuel source of methane started to decline in the 1980s and probably caused the late twentieth century slow-down in the growth rate of atmospheric methane.