Microphytic crusts,shrub patches and water harvesting in the Negev Desert: the Shikim system

Human-made contour banks are a central component of theShikim water harvesting system in Israels Negev Desert.Efficient water capture depends on the presence of a stable microphytic crustwhich directs surplus surface runoff into the banks where it is stored. We usedsimulated rainfall to examine the impact of soil surface disturbance on runoffand sediment transport, and the effect of this on the efficiency of resourcecapture within the Shikim system. Two disturbance regimes:1) removal of the microphytic crust only, and 2) removal of the crust and shrubpatches by cultivation, were compared with an undisturbed control. In theundisturbed state, 32% of rainfall was redistributed as runoff. This runoffpenetrated approximately 27% deeper under the shrub patches compared with themicrophytic crust. When the microphytic crust was destroyed by simulatedtrampling, the runoff coefficient declined to 13%, and there was no significantdifference in water penetration between shrub and crust patches. Completedestruction of the shrub hummocks and crust by cultivation resulted in adeclinein the runoff coefficient to 6%. The result of sustained disturbance in thesepatchy Negev shrublands is a breakdown in spatial heterogeneity, a loss ofecosystem function, a reduction in ecosystem goods and services such as plantdiversity and production, and ultimately a reduction in pastoral productivity.These results reinforce the view that microphytic crusts are critical for theefficient operation of the Shikim water harvesting system.Given that practices such as cultivation and trampling which disturbmicrophyticcrusts result in enhanced infiltration, crusts should be left intact tomaximisethe water harvesting efficiency in these desert landscapes.This revised version was published online in May 2005 with corrections to the Cover Date.     

向海尖底泡沼泽沉积物磁化率特征及其环境意义

以吉林省向海自然保护区尖底泡沼泽湿地为研究对象,通过210Pb,137Cs建立高分辨率年代序列,并结合沉积物粒度指标,分析沉积物粒度与磁化率变化的相关性,对向海近几百年的环境变化进行探讨.结果表明:历史时期内陆沼泽沉积物频率磁化率反映的向海气候变化可划分3个阶段,并与粒度的分析结果基本一致.沼泽沉积物磁化率可以作为恢复历史时期环境变化的指标之一.     

干热河谷冲沟侵蚀劣地坡积区土体性质与裂缝形态发育特征

采用实地调查和室内分析等方法,并结合数字图像处理技术,研究了干热河谷冲沟侵蚀劣地坡脚堆积区(PJ)、坡底沉积区(PD)和平地漫流区(PM)土体性质和裂缝形态发育特征,并探讨了土体性质对裂缝形态特征的影响。结果表明,(1)侵蚀劣地坡积区不同部位土体性质差异显著,其中土壤体积质量及黏粒质量分数均表现为PDPJPM,毛管孔隙度为PMPDPJ,有机质为PMPJPD;不同部位土体性质极值比:黏粒质量分数最大(1.94),有机质(0.65)次之,再次是毛管孔隙度(0.27),土壤体积质量(0.09)最小;PJ、PD土体性质变化主要受物源特性和沉积方式的影响,而PM土体性质主要与植被分布以及漫流有关。(2)干热河谷侵蚀劣地不同部位土体裂缝形态特征差异也十分显著,其中裂缝长度密度(Lc)及连通性指数(K)均表现为PDPJ≤PM,面积率(Rc)、面积周长比(APc)及加权平均分形维数(AWMFRAC)则整体上表现为PD≥PJPM(Ⅲ号坡积区的Rc除外);表明裂缝发育强度(Rc)及复杂程度(APc、AWMFRAC)PD最高,其次为PJ,再次是PM。(3)相关分析表明,长度密度与土壤体积质量(p=-0.782)、黏粒质量分数(p=-0.626)均呈显著负相关,连通性指数与黏粒质量分数呈显著负相关(p=-0.618),这表明土壤体积质量及黏粒质量分数对裂缝发育产生了重要影响。     

不同水平的亚硒酸钠对鸡心肌组织硒沉积及组织结构的影响

通过在公鸡日粮中添加不同水平的亚硒酸钠,研究硒在公鸡心肌组织中的沉积量和对其组织结构功能的影响,以期为亚硒酸钠在禽类生产中的应用提供参考依据。试验选取80只体重接近、健康无疾病的海兰白成年公鸡,随机分成4组,每组20只,分别在日粮中添加0、0.3、0.6和1.0 mg/kg的亚硒酸钠。试验结束时,采集心组织样本,测定硒含量,并通过HE染色观察组织细胞结构。结果表明,公鸡心肌组织中硒含量随日粮硒含量的增加而升高。由此得出,公鸡心肌组织的硒含量随着日粮硒水平的增加而逐渐升高,高硒日粮对心肌组织的结构有一定影响,但由于硒在心肌组织中的沉积能力与其他组织相比较差,因此影响并不明显。     

Evaluating Sediment Accretion on a Relic Oyster Reef in Mobile Bay,Alabama

Abstract

Sediment traps were deployed at Fish River Reef (FRR), a relic oyster reef on the eastern side of Mobile Bay, and at Cedar Point Reef (CPR), a productive oyster reef on the western side of Mobile Bay, Alabama, from July through October 1999. Sediment accretion at FRR was two to three times greater than sediment accretion at CPR. The proportions of particulate organic matter and ash in the sediment at the two sites were similar. The proportion of coarse to fine sediment at CPR was greater than at FRR. Also, the sediment at FRR was black and had a sulfide odor suggesting anoxia, while the sediment at CPR was brown and odorless. Various fishes and invertebrates colonized the sediment traps at CPR, while those at FRR were devoid of live organisms. Oyster spat had settled on the shells in the traps at CPR but not on those at FRR. Results suggest that in order to restore oysters at FRR, cultch material should be dispersed during periods of peak larval settlement to prevent inhibitory levels of siltation on cultch before spat settle.     

Tracing Sediment Sources Using Mid‐infrared Spectroscopy in Arvorezinha Catchment,Southern Brazil

The widespread adoption of the sediment fingerprinting approach to guide catchment management has been limited by the cost and the difficulty to prepare and process samples for geochemical and radionuclide analyses. Spectral properties have recently been shown to provide a rapid and cost‐efficient alternative for this purpose. The current research objective was (i) to quantify the sediment source contributions in a 1∙19‐km² rural catchment of Southern Brazil by using mid‐infrared (MIR) spectroscopy and (ii) to compare these results with those obtained with geochemical approach and near‐infrared and ultraviolet–visible spectroscopy methods. The sediment sources to discriminate were cropland surface (n  = 20), unpaved roads (n  = 10) and stream channel banks (n  = 10). Twenty‐nine suspended sediment samples were collected at the catchment outlet during nine significant flood events. The sources could be distinguished by MIR spectroscopy. Cropland and channel bank sources mainly differed in their clay mineral contents, but their similar organic matter content complicated the MIR‐model predictions. Unpaved road contributions were discriminated from the other sources by their lower organic carbon content. When the results of the current research based on MIR spectroscopy are compared with those obtained using other sediment fingerprinting approaches, based on geochemistry and near‐infrared and ultraviolet–visible spectroscopy, an overestimation of channel banks contribution and an underestimation of cropland and unpaved road contributions is found. These results suggest that MIR spectroscopy can provide a useful tool that is non‐destructive, rapid and cheap for tracing sediment sources in rural catchments and for guiding the implementation of soil and water conservation measures. Copyright © 2016 John Wiley & Sons, Ltd.     

辽东湾北部近海海域表层沉积物类型及分布特征

对2004年采自辽东湾北部近海海域的16个表层沉积物样品作了粒度分析和粒度参数计算,并进行了沉积物分类和分布特征的研究,结果表明,辽东湾北部近海的表层沉积物粒度主要由粉砂组成,平均含量65.15%,平均粒径5.031。总的特征是在5~10 m等深线,沉积物粒度的平均粒径由东部的4.530、中部的5.050逐渐增大到西部的6.236。沉积物粒度的组成类型由东向西按粉砂质砂→砂质粉砂→粉砂→砂-粉砂-黏土→黏土质粉砂由粗至细排列。     

水力旋流器在多泥沙河流中应用的研究

利用水力旋流器，对水力机械的润滑、轴封用水进行净化，降低泥沙含量，使之达到技术供水标准。本文研究和分析了水力旋流器的结构、各部构件尺寸与净化泥沙性能的关系；指明了水经过旋流器的压力降的确定，使之既满足泥沙沉降的要求，又要保证供水系统的所需的压力值。     

小型自排沉沙池沉沙工况的水力学特性试验研究

首先介绍了小型自排沉沙池的工作原理与工作过程,然后以物理模型对小型自排沉沙的水力学特性进行试验研究,通过试验资料深入分析了小型自排沉沙池内水流的流态特征,流速分布等水力特性。试验研究旨在为进一步研究小型自排沉沙池沉沙工况提供依据。     

太行山石质山地植被结构优化评价

以太行山石质砂岩区山地植被为研究对象,在对典型植被类型综合调查的基础上,提出了评价山地植被水土保持效益的10项指标,并通过不同植被类型的水源涵养效能指标测定和径流小区泥沙对比分析,认为人工-天然复合植被类型的水土保持效果最好,乔木林最适郁闭度为0．6～0．7。阐述了突出水土保持、水源涵养功能的植被优化结构建设是太行山石质山地植被恢复的根本途径和防护林体系建设的重要内容。