Last glacial terrestrial vegetation record of leaf wax n-alkanols in the northern South China Sea: Contrast to scenarios from long-chain n-alkanes

Long-chain n-alkanols and n-alkanes in core sediments from the northern South China Sea (SCS) were measured to make a comparison during terrestrial vegetation reconstruction from ~42 ka to ~7 ka. The results showed that terrestrial vegetation record from long-chain n-alkanes matched well with previous studies in nearby cores, showing that more C₄ plants developed during the Last Glacial Maximum (LGM) and C₃ plants dominated in the interglacial period. However, these scenarios were not revealed by terrestrial vegetation reconstruction using long-chain n-alkanols, which showed C₃ plant expansion during the LGM. The discrepancy during the interglacial period could be attributed to the aerobic degradation of functionalized long-chain n-alkanols in the oxygen-rich bottom water, resulting in poor preservation of terrestrial vegetation signals. On the other hand, the different advantages of functionalized n-alkanols and non-functional n-alkanes to record local and distal vegetation signals, respectively, may offer a potential explanation for the contradiction during the LGM when the SCS was characterized by low-oxygen deep water. Nevertheless, large variations on n-alkyl lipid compositions in C₃/C₄ plants could play a part in modulating sedimentary long-chain n-alkanols and n-alkanes toward different vegetation signals, thereby suggesting that caution must be taken in respect to the terrestrial vegetation reconstruction using long-chain n-alkanes and long-chain n-alkanols.     

Understory and small trees contribute importantly to stemflow of a lower montane cloud forest

Stemflow (Sf) measurements in tropical rain and montane forests dominated by large trees rarely include the understory and small trees. In this study, contributions of lower (1‐ to 2‐m height) and upper (>2‐m height and <5‐cm diameter at breast height [DBH]) woody understory, small trees (5 < DBH < 10 cm), and canopy trees (>10‐cm DBH) to Sf per unit ground area (Sf_a) of a Mexican lower montane cloud forest were quantified for 32 days with rainfall (P) during the 2014 wet season. Rainfall, stemflow yield (Sf_y), vegetation height, density, and basal area were measured. Subsequently, stemflow funneling ratios (SFRs) were calculated, and three common methods to scale up Sf_y from individual trees to the stand level (tree‐Sf_y correlation, P‐Sf_y correlation, and mean‐Sf_y extrapolation) were used to calculate Sf_a. Understory woody plants, small trees, and upper canopy trees represented 96%, 2%, and 2%, respectively, of the total density. Upper canopy trees had the lowest SFRs (1.6 ± 0.5 Standard Error (SE) on average), although the lower understory had the highest (36.1 ± 6.4). Small trees and upper understory presented similar SFRs (22.9 ± 5.4 and 20.2 ± 3.9, respectively). Different Sf scaling methods generally yielded similar results. Overall Sf_a during the study period was 22.7 mm (4.5% of rainfall), to which the understory contributed 70.1% (15.9 mm), small trees 10.6% (2.4 mm), and upper canopy trees 19.3% (4.4 mm). Our results strongly suggest that for humid tropical forests with dense understory of woody plants and small trees, Sf of these groups should be measured to avoid an underestimation of overall Sf at the stand level.     

季节性放牧对黄河源区高寒草甸植被耗水量及水分利用效率的影响

研究季节性放牧对植被耗水量、水分利用效率的影响,是探索如何提高高寒草甸水源涵养能力的重要内容之一。以青藏高原三江源高寒草甸季节性放牧样地与自然放牧样地为研究对象,分析了季节性放牧和自然放牧条件下高寒草甸植被耗水量、水分盈亏量、水分利用效率（WUE）的动态变化及其与环境因素的关系。结果表明：在植被生长季（5-9月）,季节性放牧样地和自然放牧样地植被耗水量在5月开始增加, 7月达最高,分别为160.94 mm和145.96 mm,季节性放牧样地植被总耗水量（395.52 mm）比自然放牧样地（348.14 mm）高13.61%。生长季平均来看,季节性放牧样地和自然放牧样地5-9月水分正盈余,分别为13.58 mm和70.96 mm,但在植物生长旺季（8月）略有亏缺。季节性放牧样地和自然放牧样地植被耗水量均与降水量呈弱的正相关关系。季节性放牧样地植被地上净初级生产量（ANPP）、地下净初级生产量（BNPP）和总的净初级生产量（NPP）比自然放牧样地分别高32.54 g·m^-2、5.96 g·m^-2、38.50 g·m^-2,季节性放牧样地ANPP的水分利用效率（WUE）比自然放牧样地高53.85%,而BNPP、NPP的WUE比自然放牧样地分别低13.06%和9.97%。这表明,季节性放牧可提高植被生产量和耗水量,但对高寒草甸WUE的影响因放牧方式不同导致地上、地下生物量分配格局不同而有所差异。     

角闪石族和辉石族矿物的系统矿物学分类命名

角闪石族和辉石族矿物是链状硅酸盐矿物的重要组成部分,它们中的许多矿物种属于造岩矿物和/或工业矿物,具有重要的成因矿物研究意义和工业应用开发价值。国内学者对它们的分类命名和基本系统认识主要源自于王璞等(1984)编著的《系统矿物学》。随着科学技术发展和矿物学研究的不断深入,原有的矿物基础资料和分类命名都在不断更新与完善,迄今已有专业学术机构和学者在不同年代陆续发表了不同版本对该两类矿物的修订或修改意见,但一直没有统一整合,导致在涉及该两类矿物的应用研究中,在分类命名上与国际标准不统一。根据本课题组在国家公益性行业科研专项项目(新编《系统矿物学》)所承担的研究任务和当前国内外研究进展,本文系统归纳、梳理并综述了角闪石族和辉石族矿物的分类方案和命名原则,使分类命名统一标准、原则和认识并与国际接轨,这有利于该两类矿物的理论研究与开发应用,更好地支撑地质学及相关学科的研究与发展。     

陆源碎屑岩中的古土壤在地层分析中的应用

对各种古土壤的分类标准进行比较之后,重点介绍了Mack的古土壤分类及其土壤的演变序列。Mack的古土壤分类主要依据稳定矿物和保存在土壤中的古地貌属性,将古土壤划分为9种。在地层序列中古土壤的识别标志主要包括颜色、粒度、生物成因构造（植物生长痕迹）、原生沉积构造退化特征、层次化和边界特征、宏观结构特征、矿物及地球化学特征等。可以通过野外观察、室内显微镜观察、实验室化验及地震、测井资料来进行鉴别。陆相盆地具有很强的分隔性,盆地相变又非常复杂,寻找区域性较稳定的层序界面比较困难。越来越多的研究证实用古土壤划分陆相成因地层层序、解决地区及全球对比具有重要的实用价值。     

Mineralogy and heavy metal content in sediments from Rio Gato,Carelmapu and Cucao,Southern Chile

In southern Chile, with a mild and rainy climate, high levels of heavy metals have been detected in many gold placer deposits. Many of the contaminants pose risks to human life, and consequently damage the trofic chain in this environment. The study zones selected correspond to the handicraft gold-bearing sands of Rio Gato (Los Muermos), Carelmapu and Cucao. These are all located in the X Region of “Los Lagos” in Chile. The type of methodology used in the characterization of the associated mineralization consists of testing each representative sample with a grain size distribution, statistical parameter analysis and a mineralogical analysis, using a binocular magnifying glass, a petrographic microscope, XRD and SEM/EDX. The chemical composition was defined by means of X ray fluorescence and micro-chemical analysis. The results of the study about sediments in southern Chile are presented. The major concentrations of heavy minerals are generally located in areas of dynamic river energy. In the samples, more than 70% of the heavy minerals were distributed among grain sizes corresponding to thin sand with good grain selection (meshes of 0.25–0.06 mm). The main mineral phases present in the analysed samples were gold, zircon, olivine, ilmenite, hornblende, hypersthene, hematite, garnet, chromite, chlorite, augite, amphibolitic-epidote, etc. The main heavy metals found as a result of the study were mercury, lead, cadmium, chrome, tellurium, indium, zinc, cobalt, copper, platinum, gold, etc., and as well some less common elements like cerium, praseodymium, gadolinium, neodymium, samarium and lanthanum. This research work is only a starting point for carrying out a risk probability mapping of heavy metals and the mineralogy of the Cucao, Carelmapu and Rio Gato gold-bearing sands.     

高寒植被生态系统变化对土壤物理化学性状的影响

在黄河源区选择典型样地,对土壤有机质(SOM)、全氮(N)等化学性状及土壤机械组成、容重和土壤导水率等物理特性进行分析.结果表明,植被退化导致土壤物理化学性状显著退化.灌丛草甸草地土壤表层有机质(SOM)从179.58 g·kg^-1降到49.48 g·kg^-1,表层碱解N流失率为30%,退化嵩草草甸表层有机质SOM减少53%,碱解N损失率为28.4%.沼泽地有机质SOM减少了15.11 g·kg^-1.退化后的土壤土层厚度变薄,土壤颗粒变粗,土壤水分分布和含量出现变化,土壤出现沙化,土壤容重增大,土壤导水率与植被盖度有很好的相关性.研究表明,高寒植被生态系统的变化引起了土壤理化特性的强烈变化,高寒土壤环境出现退化.     

孤北～桩海地区古近系东营组层序划分及特征研究

以孤北~桩海地区古近系东营组为研究对象,通过大量的地震剖面解释、测井资料分析、钻井岩芯观察,在研究区东营组岩石学特征分析的基础上,详细研究了层序划分及层序特征,共划分出SQ1、SQ2二个长期旋回,Ed1、Ed2、Ed3、Ed4四个中期旋回。同时,还深入讨论了各层序在地震剖面、钻井剖面及测井曲线上的特征;论述了各层序的发育特征。其中,Ed1层序在全区呈对称分布;Ed2层序主要发育下降半旋回;Ed3层序旋回对称明显,全区均有分布;Ed4层序在研究区内主要发育上升半旋回。通过对该地区层序划分的认识,为该地区的层序对比和层序地层格架的建立等,提供了重要的依据。     

古新世-始新世暖期北半球野火演化研究

古近纪是现代气候和植被形成的关键过渡期, 而野火活动与气候、植被和碳循环等存在耦合关系。开展古新世-始新世(66~34 Ma)3个特征暖期, 即古新世-始新世极热事件(PETM, 约55.9 Ma)、早始新世气候适宜期(EECO, 53.3~49.1 Ma)、中始新世气候适宜期(MECO, 约40.5~40.1 Ma)的野火活动研究, 对于揭示气候和植被变化特征及其影响具有重要意义。本研究基于蒙古高原南部二连盆地古新世-始新世野火记录, 并结合北半球该时段其他12个地点的野火研究数据, 从长尺度地质记录视角, 重建北半球野火活动特征与演变, 并探讨其驱动机制。研究结果显示古新世-始新世不同特征暖期野火发生规模和强度存在差异, PETM极端暖期较EECO和MECO暖期野火强度更大, 但不十分显著。古新世-始新世暖期并没有持续的、大规模的野火发生, 呈现"低野火状态", 总体不支持强调燃烧活动影响全球碳循环的"野火假说"。通过野火发生与温度、降水、植被以及CO2浓度等环境因子之间的关系分析, 对"古近纪低火谜题"进行初探, 认为古新世-始新世气候的季节性并不分明, 较短的干季不利于可燃"燃料"和潜在火源的形成, 很可能是新生代早期"低野火"的主因。