Inferring trophic variation for Antarctic krill(Euphausia superba) in the Antarctic Peninsula from the austral fall to early winter using stable isotope analysis     

ZHU Guoping  ZHANG Haiting  SONG Qi  YANG Yang  WANG Shaoqin  YANG Qingyuan 《海洋学报(英文版)》2018,(6)

The Antarctic krill(Euphausia superba) is a key species in the Southern Ocean ecosystem and an important link in the food web of the Antarctic ecosystem. The trophic information for this species during the transition from the austral fall to the winter is important to understand its poorly known overwintering mechanisms. However, the few studies on the topic differ in their results, in terms of both spatial and temporal variables. We investigated the size dependence and monthly and regional variation in δ~(13) C and δ~(15) N values of adult krill in the Antarctic Peninsula, in the austral fall(April to May) and the early winter(June). We aimed to examine the trophic variations of krill occurred during this period, and the relationship between krill and their feeding environment in the Antarctic marine ecosystem. The following results were obtained:(1) no significant relationship was observed between size and the δ13 C value of krill, but the δ15 N value of krill presented a remarkable association with size;(2)the δ13 C values of krill increased during the austral fall, but no remarkable variation existed at the onset of winter,and the δ15 N values were not significant different during this period;(3) mean δ15 N values of krill differed significantly between the Bransfield Strait and the South Shetland Islands. Our data imply that adult krill present size-, season-, and region-dependent trophic variation during the transition from austral fall to early winter in the Antarctic Peninsula.  相似文献   

西南煤系地层山区采动型崩滑灾害研究关键问题     

李军  褚宏亮  李滨  贺凯  高杨 《中国岩溶》2020,39(4):453-466

文章在分析采矿型崩滑灾害发育特征的基础上，得出西南煤系地层山区地下采动型崩滑灾害常发生在层状碳酸盐岩与碎屑岩地层组成的褶皱翼部和核部的陡崖带上，与地形地貌、地层结构与地下采矿工程活动等因素关系密切，并指出薄矿层开采诱发大型山体崩滑灾害的具体过程:①采空后覆岩顶板塌落—覆岩顶板离层，采空区上覆岩层内部及层间自下而上应力传递；②地下水运移通道形成，并加快更大范围岩体结构破坏及扩展，加速了岩体结构面的松动与破坏；③上覆岩层不均匀沉降导致坡脚压裂，山体大型岩体结构面逐渐拉剪或压剪变形扩展，最终山体发生累积损伤与大规模崩滑灾害。此外，传统经验公式的计算方法对此类采矿型崩滑灾害已不适用，建议开展西南煤系地层山区地质结构与地下采动诱发崩滑灾害的相互作用关系、薄矿层采空区上部山体累积断裂损伤—岩体松动、裂隙扩展-岩溶管道流、裂隙流变化的链式响应机制、地下采动型崩滑灾害评价方法等关键科学问题的研究，以推动采矿型地质灾害防灾减灾工作的发展。   相似文献   

基于斩波轮技术的K波段接收机噪声校准研究          下载免费PDF全文

王凯  王洋  陈卯蒸  段雪峰  闫浩  马军  陈晨雨  曹亮 《天文学报》2020,61(1):1

接收机是射电天文中用于探测微弱射电信号的重要接收设备.接收机的强度校准就是将接收机对射电源的响应转换为天文意义上的流量密度.常规方法就是使用经典的冷热负载法,将接收机自身的强度响应转换为一个等效的温度值,之后再据此对射电源做进一步标定.通过搭建基于斩波轮技术的K波段接收机强度校准平台,使用斩波轮法测试K波段常温接收机的噪声温度,并与传统冷热负载法的测试结果进行比对.结果显示,在晴好天气条件下,斩波轮法在30°、90°仰角下噪声温度的最大测试误差为7.5%和8.4%,可以很好地应用于实际噪声温度测试中;但在5°仰角测试中,由于过低仰角引入了地面噪声,使得斩波轮法的测试误差上升至20%–30%之间而无法使用.希望在此基础上进一步开展K波段天空亮温度的理论计算与实测,从而完善斩波轮技术的应用,使之可以满足在不同气象条件下的噪声校准测试需求.  相似文献   

Rising grain prices in response to phased climatic change during 1736–1850 in the North China Plain     

Wen  Yanjun  Fang  Xiuqi  Liu  Yang  Li  Yikai 《中国科学:地球科学(英文版)》2019,62(11):1832-1844

Grain price volatility during historical periods is regarded as an important indicator of the impact of climate change on economic system, as well as a key link to adjust food security and social stability. The present study used the wheat prices in Baoding Prefecture, China, during 1736–1850 to explore connections between climatic transition and grain price anomalies in the North China Plain. The main findings were as follows:(1) The grain price change showed an apparent correspondence with climatic transition. The period 1781–1820 was a transition phase, with more extremes and decreased precipitations when the climate shifted from a warm phase to a cold one. Corresponding with the climatic transition, the grain price during 1781–1820 was characterized by that the mean of the original grain price series was significantly higher(lower) than the previous(later)phase, and the variance and anomaly amplitude of the detrended grain price series was the highest during 1736–1850.(2) The correspondence between grain price extremes and drought events occurred in phases. Five grain price extremes occurred following drought events during 1781–1810, while extreme droughts were the direct cause of the grain price spike during 1811–1820.(3) Social stability affected by climate change also played an important role in the grain price spike between 1811 and 1820. Paralleling the pathway of "precipitation-grain production-grain price", climate change could have an impact on grain price via the pathway of "precipitation-grain production-grain price-famine-uprising-grain price", as shown during the Tianli Uprising in 1813. These findings could contribute to an improved understanding of the interaction between climate change and human society during the historical period.  相似文献   

X-ray activity from different types of stars     

Lin He  Song Wang  Xiao-Jie Xu  Roberto Soria  Ji-Feng Liu  Xiang-Dong Li  Yu Bai  Zhong-Rui Bai  Jin-Cheng Guo  Yan-Li Qiu  Yong Zhang  Ruo-Chuan Xu  Ke-Cheng Qian 《天文和天体物理学研究(英文版)》2019,(7)

X-ray emission is an important indicator of stellar activity. In this paper, we study stellar Xray activity using the XMM-Newton and LAMOST data for different types of stars. We provide a sample including 1259 X-ray-emitting stars, of which 1090 have accurate stellar parameter estimations. Our sample size is much larger than those used in previous works. We find a bimodal distribution of the X-ray to optical flux ratio(log(fX/fV)) for G and K stars. We interpret that this bimodality is due to two subpopulations with different coronal heating rates. Furthermore, using the full widths at half maxima calculated from Hα and Hβ lines, we show that these stars in the inactive peaks have smaller rotational velocities. This is consistent with the magnetic dynamo theory that presumes stars with low rotational velocities have low levels of stellar activity. We also examine the correlation between log(fX/fV) and luminosity of the excess emission in the Hα line, and find a tight relation between the coronal and chromospheric activity indicators.  相似文献   

基于表层岩土渗透对三峡井网井水位降雨影响的精准分析          下载免费PDF全文

周洋  吴艳霞  罗棋  李查玮 《地震工程学报》2020,42(2):460-467,528

为研究三峡井网表层岩土渗透对井水位降雨的影响,采取井区表层岩土垂向渗透性测试方法试验,测得表层岩土垂向渗透性,并建立数学模型,用于降雨渗入补给分析。在此模型基础上,通过三峡井网8口井水位、气象三要素的对比观测资料对井水位日动态、月动态、年动态的影响进行精准分析与验证。结果表明:这种影响的特征是相当复杂的,同一个降雨过程在不同井上产生的影响特征不同,这一方面可能与各井的水文地质条件不同有关,另一方面可能还与各井点的降雨过程的差异也有关。  相似文献   

三维地理信息网络服务的发展现状及思考     

孙阳  周海龙  徐爽  董莉 《测绘与空间地理信息》2020,(1):160-162

随着信息技术的发展和GIS的实际发展需求的增加,GIS逐渐转向了三维地理信息网络服务方向。在满足GIS服务发展需求的基础上,三维地理信息网络服务为空间信息的高效集成的实现作出了重要贡献。本文综述了三维地理信息网络服务的发展情况,并提出了存在的问题及相应的建议,以供参考。  相似文献   

Stormflow threshold behaviour in a subtropical mountainous headwater catchment during forest recovery period     

Lezhang Wei  Zhijun Qiu  Guangyi Zhou  Tsuyoshi Kinouchi  Yu Liu 《水文研究》2020,34(8):1728-1740

Forest ecohydrological feedbacks complicate the threshold behaviour of stormflow response to precipitation or wetting conditions on a long-term scale (e.g. several years). In this study, the threshold behaviours in an evergreen-deciduous mixed forested headwater catchment in southern China were examined during 2009–2015, when damaged vegetation was recovering after the great 2008 Chinese ice and snowstorm. The non-uniqueness of the thresholds and the slow and rapid responses of stormflow at the outlet of the catchment in different hydro-climate datasets with different maximum values of gross precipitation (P) and sums of precipitation and antecedent soil moisture index (P + ASI) were assessed. The thresholds of P and P + ASI required to trigger stormflows (i.e. ‘generation thresholds’) and the transition from slow to rapid responses of stormflow (i.e. ‘rise thresholds’) were compared both seasonally and annually. The results indicated significant differences in the analysed datasets, highlighting the need to compare thresholds with care to avoid misinterpretation. Seasonal variations in threshold behaviours in the catchment suggested that vegetation canopy interception contributed to higher rise thresholds, and wetter conditions resulted in higher runoff sensitivity to precipitation during the growing and rainy seasons. Furthermore, the generation thresholds were higher in the dormant season, possibly due to drier soil moisture conditions in the near-channel areas. During the vegetation recovery period, the annual generation thresholds increased, however the rise thresholds did not exhibit a similar trend. The rapid stormflow response above the threshold decreased, possibly due to transpiration and interception of the recovered vegetation. However, the slow stormflow response to small rainfall events below the thresholds was higher in wetter years but lower in drier years, suggesting that the total water input dominated the stormflow response during small rainfall events. In conclusion, the seasonal and annual variations in threshold behaviours highlight that vegetation recovery and hydro-climatic conditions had a notable impact on the stormflow response.  相似文献   

南京下蜀土的地球化学特征及其物源指示意义     

綦琳  乔彦松  王燕  彭莎莎  杨帅斌  白文彬 《第四纪研究》2020,(1):190-202

风尘堆积的物源研究对于揭示物源区的环境演化状况、重建古风场强度和古大气环流格局等都具有重要的意义。目前长江下游地区下蜀土的物质来源问题仍然存在争议。为了解决这一争议问题,本文以南京泰山新村下蜀土剖面为研究对象,开展了系统的地球化学研究。通过对南京下蜀土的常量元素、微量元素、Nd同位素进行测试,并与黄土高原同期黄土进行对比分析,探讨其对长江下游下蜀土的物源指示意义。南京下蜀土与北方黄土具有相似的常、微量元素UCC标准化曲线和稀土元素球粒陨石标准化曲线,但是它的Zr、Hf含量较高,Tl、Pb含量较低,且具有较高的SiO2/Al2O3、TiO2/Al2O3、Nb/Ta和GdN/YbN,较低的SiO2/TiO2、Zr/Hf、Y/Ho、Lu/Hf和εNd(0)值,说明南京下蜀土的物质来源明显有别于黄土高原黄土。南京下蜀土与长江中游下蜀土在地球化学特征方面有较多的相似性,指示其物质来源与中游下蜀土的物质来源相似,主要来源于长江中下游地区的松散沉积物。  相似文献   

珊瑚颗粒形状对钙质粗粒土的压缩性能影响     

张斌  柴寿喜  魏厚振  孟庆山  陈杨 《工程地质学报》2020,28(1):85-93

珊瑚颗粒形状不规则是其显著区别于陆源土的一大特征。为揭示珊瑚颗粒形状对钙质粗粒土压缩性能的影响,人工挑选出不同形状(块状、枝状、棒状、片状)的珊瑚颗粒,以块状颗粒为基础,与其他3种不同形状的粗颗粒任意一种混合,控制不同颗粒形状配比制成钙质粗粒土试样,完成室内压缩试验,对比分析试验前后珊瑚颗粒的圆度、长宽比、扁平度和凹凸度等形状参数,评价颗粒形状对压缩性能的影响。结果表明:(1)粒径为10~20 mm钙质粗粒土的压缩模量是4~5. 5 MPa,回弹系数为42~53;(2)随枝状、棒状或片状颗粒掺量的增加(0、10%、20%、30%),试样压缩模量呈小幅波状变化,回弹系数呈持续减小趋势;(3)各加载区间应力-应变曲线包括应力快速增长阶段、应力-应变同步增长阶段、应变增长阶段共3个阶段和1个稳定点;(4)随枝状颗粒掺量的增加,试样的长宽比和凹凸度逐渐增加,圆度和扁平度基本无变化;因颗粒破碎的影响,试验后试样的长宽比及扁平度有所增加,圆度及凹凸度则有所减小。选择钙质粗粒土地基时,应考虑其压缩性能,避免施工初期的快速加载。  相似文献