淤泥质潮滩地貌演变中的水动力及生物过程研究进展   总被引：2，自引：0，他引：2  

王宁舸  龚政  张长宽  赵堃  耿亮 《海洋工程》2016,34(1):104-116

淤泥质潮滩对于海岸防护、增加土地资源、保持生物多样性等具有重要作用。从淤泥质潮滩演变的主要驱动因子——潮流、波浪、生物作用及地下过程四个方面回顾和总结了潮滩演变动力地貌过程的相关研究进展,提出应关注潮滩短期演变规律、波浪与浮泥作用机理、生物生长与潮滩演变定量关系,以及地下过程作用机理等。  相似文献   

黔西北普宜地区下三叠统嘉陵江组沉凝灰岩锆石LA-ICP-MS U-Pb年龄、微量元素特征及其地质意义     

缪宇  吴亮  肖长源  李锁明  李致伟  宋文婷  田瑜峰 《地质论评》2021,67(2):289-310

早三叠世时期频繁的火山事件是导致全球性气候和海洋环境异常的主要原因,前人对早三叠世重要界线时期的火山事件地层开展了大量研究,但对典型界线时期以外的其他火山事件地层却鲜有报道。本文以上扬子西南普宜地区嘉陵江组两件沉凝灰岩为研究对象开展了岩石学、岩相学、锆石年代学及微量元素组合特征等方面的研究。沉凝灰岩样品具有典型岩浆锆石的内部结构和微量元素组合特征,两组沉凝灰岩锆石谐和年龄分别为250.6±0.6 Ma和249.1±0.8 Ma,代表了母岩岩浆中新生锆石的结晶年龄。沉凝灰岩母岩主要以酸性花岗岩类为主,次为中性正长岩类和少量基性岩类。嘉陵江组沉凝灰岩与二叠系—三叠系界线(PTB)凝灰岩及Olenekian—Anisian界线(OAB)绿豆岩具有同源性,形成于活动大陆边缘的碰撞造山环境,源区很可能位于中越边境地区长山构造岩浆带—十万大山火山带,且在陆壳碰撞过程中源区地壳处于持续的增厚阶段,下地壳增厚部位的部分熔融形成补给岩浆上涌并使早期结晶矿物发生了部分熔蚀。本文嘉陵江组沉凝灰岩样品250.6±0.6 Ma年龄对应着Smithian—Spathian界线时期的全球性降温及短期生物复苏事件;249.1±0.8 Ma年龄的样品对应Spathian亚阶中期极端高温气候和生物再次灭绝事件,再次证明了早三叠世时期频繁的火山活动是导致气候改变和生物周而复始新生和灭绝的重要因素。其原因可能是阳伞效应和温室效应等因素综合反馈的结果,但具体证据仍需要将来更多学科综合研究成果的约束。  相似文献   

高寒冻土区生物结皮对土壤理化属性的影响   总被引：1，自引：0，他引：1  

明姣  盛煜  金会军  张泽  杜玉霞 《冰川冻土》2021,43(2):601-609

生物结皮是高寒地区地被层的重要组分之一。其作为地表特殊的结构层,能够改变地表结构及土壤理化属性,从而影响冻土环境。迄今为止,关于青藏高原高寒生态系统中生物结皮对土壤理化属性的影响尚不清楚。以青藏高原高寒冻土区生物结皮为研究对象,初步研究了生物结皮的特征及其对土壤理化属性的影响。结果表明：生物结皮在高寒草甸退化过程中广泛发育,主要以藻结皮为主,其盖度可达37.3%~51.7%,结皮层平均厚度为12.6 mm。由于生物结皮的发育,高寒地区5~20 cm土层粉粒含量有所增加,但差异不显著,而结皮层土壤田间持水量相比于裸地表层（2 cm）增加了10%~40%,结皮层容重较裸地降低了30%;两种类型藻结皮均显著增加了结皮层及其下0~20 cm土层土壤有机质,而深色藻结皮增加了结皮层及其下0~20 cm土层土壤全氮含量,浅色藻结皮仅增加了结皮层土壤全氮含量,对其下0~20 cm土层土壤全氮含量没有显著影响;生物结皮对土壤pH没有显著影响;生物结皮是高寒生态系统植被退化过程中的关键环节。研究结果为揭示生物结皮在高寒生态系统中发挥重要生态功能提供依据。  相似文献   

寒武纪生物大爆发之后的底栖生态系统工程建造者:以河南地区为例          下载免费PDF全文

刘炳辰  齐永安  代明月  白万备  樊钰超  庆国帅 《地球科学》2021,46(1):148-161

扰动生物作为生态系统工程建造者,通过对沉积底质的改造直接影响沉积物和水体之间的相互作用（营养物质的循环、迁移和存储）,对底栖生态系统工程有重要的影响.遗迹化石作为底栖生物活动的载体,为研究寒武纪大爆发之后底栖生态系统工程建造者的演化规律,并评价底栖生态系统工程建造者对生态系统工程产生的影响提供了依据.对河南地区8个寒武系剖面的遗迹化石数据进行统计,应用现代生物学中生态系统工程影响值的概念,从功能群、阶层、生物灌溉3个方面对底栖生态系统工程建造者进行研究.研究结果表明,寒武系第三阶至鼓山阶底栖生态系统工程建造者功能群类型由生物扩散型扰动者往向上/下运输者转变,阶层逐渐加深,生物灌溉越来越普及,生态系统工程影响值不断增大.鼓山阶至第十阶,遗迹化石类型及结构变化不大,生态系统工程影响值趋于稳定.这表明从寒武纪生物大爆发至鼓山阶,底栖生态系统工程建造者的行为策略发生着明显的进化与创新,生态系统工程建造者不仅开拓了重要的生态空间,而且为其他底栖生物和微生物创造了新的生境,在寒武纪海洋生态系统中扮演着重要的角色.   相似文献   

Long‐term effects of revegetation on soil hydrological processes in vegetation‐stabilized desert ecosystems     

Zhongbo Yu  Haishen Lü  Yonghua Zhu  Sam Drake  Chuan Liang 《水文研究》2010,24(1):87-95

Planting of sand‐binding vegetation in the Shapotou region on the southeastern edge of the Tengger Desert began in 1956. The revegetation programme successfully stabilized formerly mobile dunes in northern China, permitting the operation of the Baotou‐Lanzhou railway. Long‐term monitoring has shown that the revegetation programme produced various ecological changes, including the formation of biological soil crusts (BSCs). To gain insight into the role of BSCs in both past ecological change and current ecological evolution at the revegetation sites, we used field measurements and HYDRUS‐1D model simulations to investigate the effects of BSCs on soil hydrological processes at revegetated sites planted in 1956 and 1964 and at an unplanted mobile dune site. The results demonstrate that the formation of BSCs has altered patterns of soil water storage, increasing the moisture content near the surface (0–5 cm) while decreasing the moisture content in deeper layers (5–120 cm). Soil evaporation at BSC sites is elevated relative to unplanted sites during periods when canopy coverage is low. Rainfall infiltration was not affected by BSCs during the very dry period that was studied (30 April to 30 September 2005); during periods with higher rainfall intensity, differences in infiltration may be expected due to runoff at BSC sites. The simulated changes in soil moisture storage and hydrological processes are consistent with ongoing plant community succession at the revegetated sites, from deep‐rooted shrubs to more shallow‐rooted herbaceous species. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

南京梁代石刻微侵蚀的研究   总被引：5，自引：0，他引：5  

张捷  陈舒泛 《地理学报》1994,49(5):418-428,T001

从地貌学角度较系统地分析了梁代石灰岩石刻表面自然毁损的微侵蚀机制，本文指出，雨水沿缝合线渗流，经多种地衣及兰藻、绿藻等生物作用而大大加强了溶蚀作用，导致石刻的崩解，并讨论此种特殊微侵蚀形态的形成机制在地貌学理论研究中的意义。  相似文献   

单纯克山病病区与单纯大骨节病病区生态化学环境的对比研究   总被引：6，自引：0，他引：6  

李日邦  谭见安 《地理学报》1995,50(3):272-278

本文对云南省牟定县申平村单纯克山病病区和陕北榆林县蟒坑村单纯大骨节病病区的生态化学环境进行了对比研究，表明两地生态化学环境仍处于低Ｓｅ水平。申平村人群仍有潜在型克山病病例，蟒坑村人群的骨质病变则出现很高的Ｘ线阳性检出率，说明两地的致病因子仍然活跃，从生态系物质含Ｓｅ量看出，蟒坑村的缺Ｓｅ程度较申平村高。此外，单纯克山病病区申平村土壤，粮食，人发中的Ａｓ明显高于蟒坑村和非病区。为此，从Ａｓ与Ｓｅ具有  相似文献   

Biological and physical events involved in the origin,effects, and control of organic matter in solar saltworks     

Joseph S. Davis  Mario Giordano 《International Journal of Salt Lake Research》1995,4(4):335-347

Aspects of communities and events in the concentrating ponds (S.G. 1.130 to 1.214) and salt crystallizing ponds (S.G. 1.215 to 1.264) of solar saltworks pertinent to salt manufacture are described. Communities that aid salt manufacture enable continuous and efficient production of high quality salt at a saltworks' design capacity, and they provide important controls on levels of organic matter in the brine. Fluctuating salinities, high concentrations of nutrients, and petroleum products are disturbances that causeAphanothece halophytica andDunaliella salina to release excessive quantities of organic matter, and that suppress or cause death to nutrient stripping organisms. Disturbances result in decreased quality and quantity of salt and increased costs for salt harvest, washing, and pond upkeep. Organic matter can be controlled by management techniques that keep nutrient stripping communities at proper levels and maintain a narrow and unchanging range of salinities in each pond, by constructing pond dikes able to withstand wind and water erosion, and by preventing spills of petroleum products in the ponds.  相似文献   

Identification and occurrence of novel C₃₆–C₅₄ 3,4-dialkylthiophenes with an unusual carbon skeleton in immature sediments     

M.E.L. Kohnen  T.M. Peakman  J.S.Sinninghe Damste  J.W. de Leeuw 《Organic Geochemistry》1990,16(4-6)

A series of novel long-chain 3,4-dialkylthiophenes (C₃₆–C₅₄) was identified in a number of sediments ranging from Pleistocene to Cretaceous. The identifications were based on mass spectral characterisation, desulphurisation and mass spectral data of synthesised model compounds. These organic sulphur compounds are probably formed by sulphur incorporation into mid-chain dimethylalkadienes with two methylenic double bonds. These putative precursor lipids are unprecedented and may be considered rather unusual. The distribution of 3,4-dialkylthiophenes in sediments varies considerably with the depositional palaeoenvironment, indicating that these compounds have a potential as molecular markers reflecting changes in palaeoenvironment.  相似文献   

Biological marker compounds as indicators of the depositions! history of the Maoming oil shale     

Simon C. Brassell  Geoffrey Eglinton  Fu Jia Mo 《Organic Geochemistry》1986,10(4-6)

The Eocene Maoming oil shale from Guangdong Province occurs as a laterally uniform stratigraphic section, typically 20–25 m thick, from which the aliphatic hydrocarbon constituents of six representative samples were investigated using GC and C-GC-MS. The sediments evaluated included the basal lignite, a vitrinite lens from the overlying claystone, and four intervals from the massive oil shale bed. As expected, the lignite and vitrinite differ markedly from the oil shales. The lignite is dominated by bacterial hopanoids and components of higher plant origin, including C₂₉ steroids and triterpenoids such as oleanenes. Visually, the oil shale samples show corroded and degraded phytoclasts, spores, wispy particles of fluorescent organic material attributable to dinoflagellates and, especially in the uppermost sample, colonial algal bodies. The distributions of biological markers in the oil shales show many features in common, notably a dominance of dinoflagellate-derived 4-methylsteroids, and a significant proportion of higher-plant derived n-alkanes with marked odd-over-even carbon number predominance. Overall, they exhibit several features that resemble characteristics of the Messel shale. The hydrocarbons of the lowest shale horizon suggest that there may have been a gradual transition between deposition of the original peat and the subsequent oil shales. The aliphatic hydrocarbons of the uppermost shale are dominated by a number of C₃₁ and C₃₃ botryococcane homologues and other unusual branched alkanes possibly derived from green algae. All of the samples are immature. Overall, molecular and microscopic examination of the stratigraphic succession of the Maoming oil shale suggests a shallow, lacustrine environment within which peats were deposited. This lake subsequently deepened to support abundant algal populations, especially dinoflagellates, culminating in a dominance of botryococcoid algae.  相似文献