不同营养水平下浮游细菌群落对盐度干扰的响应与稳定性

微生物群落是湖泊生态系统的重要组成部分,其结构和功能的稳定性对于生态系统正常执行功能和服务具有至关重要的作用。以营养富集和盐度增加为特征的全球变化深刻影响湖泊生态系统,揭示这些因素对微生物群落结构及其稳定性的影响机理具有重要意义。本研究以浮游细菌群落为研究对象,开展2个营养水平和3个盐度干扰强度水平(对照组、3‰和9‰)的室内模拟实验;基于同一时间点的实验组和对照组之间细胞密度的差异,计算反应力、抵抗力、恢复力和时间稳定性等多个稳定性指标,尝试揭示群落的稳定性机制;借助细菌16S rRNA基因高通量测序对群落结构进行分析,阐明不同营养水平下浮游细菌群落不同类群对盐度干扰的响应。研究发现,浮游细菌的细胞密度和物种丰富度在盐度干扰后降低,对盐度敏感类群相对丰度减少;盐度干扰后水体中溶解性有机碳增加,促进了适应干扰后环境的浮游细菌生长。更高的干扰强度显著降低了细胞密度,导致了更低的抵抗力;盐度干扰和营养水平在反应力、恢复力和时间稳定性方面存在显著交互作用,在9‰盐度干扰下,高营养水平群落表现出最低的稳定性。多数稳定性指标之间表现出了显著的正相关,可以协同指示浮游细菌群落的稳定性;抵抗力和恢复力之间并不显著相关,但是可以从不同角度反映群落稳定性。未来淡水生态系统的富营养和盐度增加将显著降低浮游细菌群落稳定性,多个稳定性指标的应用和高频次观测有助于了解浮游细菌群落对干扰的响应与稳定性机制。     

基坑施工时下方近距离隧道保护

随着城市建设的高速发展,出现了不少施工项目。在间距很小的情况下,如何采取有效措施控制隧道的变形,是值得摸索和研究的课题。在已经完工的上海东方路下立交工程施工过程中,依靠有针对性的设计和施工措施,使距其基坑底下3m的地铁2号线隧道得到了很好的保护。文章总结了这些工程措施,并将大部分归为基坑开挖“竖向”时空效应的体现。     

浅谈托克托县人工影响天气作业对生态和农业的保障

托克托县深居内陆,远离海洋,处于土默特平原的腹地,南临黄河北靠阴山山脉,经常有冷暖空气交绥,易产生对流天气现象,属北温带大陆性气候,个别地区又有明显的区域性气候特征。冬季漫长而干冷。夏季短暂而暖湿。冷暖变化剧烈,雨量少,气候干燥,年平均降水量为352．4mm,年最少降水量为162mm．处于半干旱地区。     

Geo-hazards risk zonation and warning system based on GIS in Anshan City of Liaoning

Debris flow and Karst collapse are the main parts of geological disasters in Anshan, which have affected on the construction and development of the social economy of Anshan. In order to enhance the studies of rules of disaster and give scientific estimation and alarm ahead of schedule warning, we established the warning system of Anshan and investigated the corresponding software, which are based on the deep discussions about the crisis estimation and methods of prediction of disasters. In this paper, the foundation of model used in estimating the alarm ahead of schedule for disaster and the methods of appraisal for the alarm ahead of schedule are discussed. This system for warning and evaluating is the combination of the models of warning and GIS flat roof, with so many virtues, such as complete functions, convenience, applicability, which has considered the output of data, analyses of space, chooses of model, output of production, report of information for warning and the statements and help of system.     

极端干旱地区绿洲小气候特征及其生态意义

1 Introduction Microclimate is one of the most important environmental factors for plant growth and development. Different plant communities create different microclimatic environments and different microclimatic environments support different biotic comm…     

中国干旱区不同成因碎屑沉积物的吹蚀速率研究

1 Introduction The sand deserts in China are the product of long-term wind erosion from clastic sediments and remodified by wind in the arid environments (Wu, 1987; Gao et al., 1993). The origin of aeolian sand is an elementary issue in studying morpholog…     

戈壁沙砾质地表沉积物全粒径分布模式及其对分选作用的指示意义

戈壁地表沉积物组分呈多峰态分布的特征,研究其全粒径分布模式是认识戈壁成因及形成过程的基础。目前粒度分布模式(对数正态分布、Weibull分布等)难以正确表达呈多峰态的沉积物粒度分布特征,本文利用单调递减函数P(d_i)=Cd_i^-μexp(-d_i/Dc),对戈壁地表沉积物粒度的全粒径分布模式进行解析。结果表明:(1)该函数能够反映出戈壁地表沉积物组分的全粒径分布特征,拟合优度R^2>0.99,参数C值范围为52.64～166.75,μ为-0.083～0.108,Dc为0.103～2.336;(2)在分选作用下,以富沙组分为主的戈壁地表,跃移组分含量高,μ值、Dc值偏小,以富砾组分为主的戈壁地表,蠕移及风蚀残余组分含量高,μ值、Dc值偏大;(3)全粒径分布模式参数值可以揭示洪积扇戈壁的分选沉积特征,为解析戈壁地表的成因以及风蚀风积作用提供新的指标参数。     

中国北方农牧交错带鄂尔多斯高原段土壤表层粒度特征

土壤粒度是描述土壤性质的重要参数,研究农牧交错带土壤表层粒度对土壤质量和沙化程度评价具有科学意义。对不同沉积物类型及土地利用方式土壤表层(0~5 cm深度)粒度进行分析。结果表明:(1)沙黄土、覆沙黄土残积物、风化残积物中粉粒最多,其次为极细砂和细砂,这3个粒级含量之和表现为沙黄土(96.51%)>覆沙黄土残积物(88.29%)>风化残积物(77.58%);风成沙土壤表层以细砂(53.85%)和中砂(26.13%)为主。(2)平均粒径由小到大依次为沙黄土(4.78Φ)、覆沙黄土残积物(4.62Φ)、风化残积物(3.80Φ)、风成沙(2.46Φ);分选性由差到好依次为风化残积物、覆沙黄土残积物、沙黄土、风成沙;偏度呈现为正偏或极正偏;峰值表明风成沙(2.30)粒径分布最为集中。(3)同一地表沉积物中,砾石和极粗砂等粗颗粒在农田较多,粉粒在草地较多,极细砂在林地较多;风成沙中,粉粒在固定沙丘略多,细砂在半固定沙丘较多,砾石、极粗砂等粗颗粒仅在流动沙丘地中分布。(4)土壤颗粒分形维数表现为沙黄土(2.5242)>覆沙黄土残积物(2.4373)>风化残积物(2.3554)>风成沙(2.2815);地表沉积物类型不同,表层土壤分形维数与粒级含量相关性有着明显差异。     

The effects of urban water cycle on energy consumption in Beijing,China

Journal of Geographical Sciences - Energy is consumed at every stage of the cycle of water production, distribution, end use, and recycled water treatment. Understanding the nexus of energy and...     

Influence Analysis on the Floating Underwater Monitoring System Applicable for Very-Low-Frequency Acoustic Measurement

Ocean vector acoustic measurement is feasible affected by the hydrodynamic interference caused by the flow fluctuations and structural vibrations, especially in the very-low-frequency monitoring. Hence, a novel horizontal floating platform including a horizontal floating cable, vertical mooring cable and floating main body is proposed and described in this paper. It has the advantages of good maneuverability along with the current and multi-stage vibration isolation. The main application of this platform is to measure the ocean ambient noise coming from the wave fluctuation and the deterministic acoustic signals such as aquatic organisms, underwater targets and sailing vehicles. The influence of the current fluctuation on the attitude angle and flow induced vibration of cables and main body are analyzed with some previous sea test data. Moreover, the comparison between the vertical type platform used before and the horizontal type platform is also discussed. It is concluded that there is obvious relevance between the attitude angle and ocean current variation. Meanwhile, the abnormal influence on the main body is caused by the vibration transmission from the fluctuation of cables. There will be the influence on the accuracy of the acoustic measurement above 100 Hz, and the inherent vibration characteristic of the main body is the primary reason.