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采用空间代替时间的方法,连续4年对浑善达克沙地飞播区(1999-2015年)植被进行调查,分析飞播植被演替进程中群落物种组成、多样性以及飞播植物种群盖度的动态变化,以期揭示飞播措施下的植被恢复规律,为飞播区植被稳定性维持提供依据。结果表明:(1)对照与演替初期生活型以一、二年生草本植物为主,随着演替时间的增加,多年生植物种类增加,逐渐取代一、二年生草本植物优势地位;演替9 a时原生植物入侵明显。(2)演替4 a时Pielou均匀度指数最高,演替9 a时Partrick丰富度指数最高,演替10 a时Shannon-Wiener多样性指数最高,在演替进程中,3个指数变化不一致。(3)羊柴种群在演替8 a时达到峰值(68.33%),种群能维持较长时间;白沙蒿种群在演替3 a时达到峰值(10.17%),在演替11 a时退出;沙打旺种群在演替4 a时达到峰值(12.67%),在演替9 a时退出;沙地榆种群盖度呈缓慢增加的线性趋势。飞播措施下浑善达克沙地植被能快速恢复,有利于植被自然演替。在浑善达克沙地生态建设中,应先考虑沙地的恢复力再决定是否飞播。 相似文献
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目的:通过网络药理学及GEO数据库,探讨真武汤治疗特发性膜性肾病(IMN)的作用机制。方法:运用TCMSP检索真武汤有效活性成分及靶点,利用GeneCards等4个数据库获得IMN靶点,采用STRING数据库和Cytoscape软件构建药物-成分-靶点-疾病相互作用网络和蛋白质-蛋白质相互作用(PPI)核心靶点网络,并进行基因本体(GO)功能和京都基因与基因组百科全书(KEGG)通路富集分析,最后进行分子模拟对接,并基于GEO进行核心靶点基因差异表达分析及免疫细胞浸润分析验证。结果:真武汤治疗IMN的关键活性成份是豆甾醇、山柰酚、β-谷甾醇等,其中核心靶点为丝氨酸苏氨酸蛋白激酶-1(AKT1)、转录因子AP-1(JUN)、半胱氨酸天冬氨酸蛋白酶-3(CASP3)等,KEGG富集分析发现主要作用在流体剪切应力等117条信号通路;分子对接显示山柰酚、β-谷甾醇与前列腺素G/H合成酶-2(PTGS2)、CASP3、AKT1等靶点具有较强结合力;GSE115857数据集中AKT1、细胞间黏附分子-1(ICAM1)、CASP3为上调基因,JUN为下调基因,这些可能与未活化的CD4记忆性T细胞、未活化的自然杀伤细胞等免疫细胞有关。结论:真武汤通过多成份、多靶点、多通路等方式治疗IMN,可为后续研究提供参考。 相似文献
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湖泊沉积物粒度分析前处理过程中絮凝现象的消除方法研究 总被引:1,自引:0,他引:1
采用激光粒度仪对湖泊沉积物进行粒度分析时需要进行必要的前处理.在有效去除有机质与碳酸盐颗粒的同时,需要消除细粒泥沙质样品中絮凝现象对粒度分析结果造成的误差或错误.本文以武汉三角湖表层沉积物样品为例,采用X射线粉晶衍射(XRD)对其矿物组成和粘土矿物种属进行鉴定,并采用全自动激光粒度仪对样品进行粒度分析.X射线粉晶衍射结果表明样品中非粘土矿物主要为石英与长石,粘土矿物以伊利石、高岭石、绿泥石为主;粒度分析结果显示样品中小于30μm组分占94.5%.这些特征表明该样品易于在前处理过程中形成絮凝.本次研究采用单因素寻优法探讨了超声震荡、分散剂、洗酸对于以伊利石、高岭石、绿泥石为主、平均粒径较小的样品消除絮凝现象的最佳条件.研究结果表明,针对此类样品消除絮凝现象的最佳条件为:超声震荡时间应选择6~8 min,分散剂浓度为20 g/L左右,同时在粒度分析之前需要对样品进行洗酸. 相似文献
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Zongjie Li Jinzhu Ma Lingling Song Juan Gui Jian Xue Baijuan Zhang Wende Gao Zongxing Li 《水文研究》2020,34(12):2810-2822
Here, we studied the isotope characteristics and source contributions of soil water in the permafrost active layer by collecting soil samples in July 2018 in Yangtze River basin. Soil moisture and temperature showed decreasing trends from 0–80 cm, and an increasing trend from 80–100 cm. The value of δ18O and δD first increased and then decreased in the soil profile of 0–100 cm; however, d-excess increased from 0–100 cm. δ18O values became gradually positive from the southwest to northeast of the study area, while d-excess gradually increased from southeast to northwest. The evaporation water line (EL) was δD = 7.56 δ18O + 1.50 (R2 = 0.90, p < 0.01, n = 96). Due to intense solar radiation and evaporation on the Tibetan Plateau, the elevation did not impact the surface soil. The altitude effect of the soil depths of 0–20 cm was not obvious, but the other soil layers had a significant altitude effect. Soil moisture and temperature were closely related to the stable isotopic composition of soil water. The contribution of precipitation to soil water on the sunny slope was 86%, while the contribution of the shady slope was 84%. However, the contribution of ground ice to soil water on sunny slope was 14% and the shady slope was 16%. The contribution of ground ice to soil water increased with increasing altitude on the sunny slope, but the contribution of ground ice to soil water had no obvious trend on the shady slope. 相似文献
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中国冬半年区域持续性低温事件的前期信号 总被引:8,自引:3,他引:5
大气变量物理分解的方法应用于寻找中国区域持续性低温事件的前期信号。1960~2008年的冬半年期间, 总数115次强的区域持续性低温事件的对流层低层出现了天气尺度温度的负值扰动, 而在对流层中高层至平流层出现了天气尺度位势高度的负值扰动。其中, 112次事件分别在850 hPa和300 hPa上出现了温度扰动负值中心和位势高度扰动负值中心。追踪850 hPa层的温度扰动能够提前5~9天预示中国区域持续性低温事件的出现。 相似文献
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Identifying Regional Prolonged Low Temperature Events in China 总被引:6,自引:0,他引:6
This study examined regional prolonged low temperature (PLT) events in China from the observational station data for the period 1960–2008 using the new criteria. The new definition of a site PLT event is that the daily minimum temperature does not exceed the 10th percentile threshold of the local daily minimum temperature climatology for at least 5 days at a station. The regional PLT event is defined as at least five adjacent stations exhibiting site PLT simultaneously for >5 d. Under the new definition, 552 regional PLT events were identified, and three indices: duration, extent, and intensity, as well as a comprehensive index (CI) were used to quantify the event severity. In addition, geographical patterns and temporal variations of regional PLT events were investigated using three event categories: strong, moderate, and weak. Spatially, strong events were mainly located in the north of Xinjiang and along the Yangtze River to the south of the Yangtze River; moderate events occurred in Xinjiang and south of the Yangtze River; and weak events occurred south of the Yellow River. The variation for the annual frequency of regional PLT events in China in the last 49 years showed a significant decreasing trend with a rate of-1.99 times per decade, and the significant transition decade was the 1980s. 相似文献
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分析气象服务效益的一般特征,阐明气象服务宏观与微观两方面的意义,确立构建气象服务效益评估模型的原则。 相似文献