Mosaic desert pavement influences water infiltration and vegetation distribution on fluvial fan surfaces     

Dejin Wang  Wenzhi Zhao  Hong Zhou  Weicheng Luo  Hu Liu 《水文研究》2021,35(9):e14373

Desert pavements (DPs) are critical for maintaining ecological stability and promoting near-surface hydrological cycling in arid regions. However, few studies have focused on eco-hydrological processes of DPs in the ecological systems of fluvial fans. Although DP surfaces appear to be barren and flat, we found that the surfaces are characterized by surface mosaic patterns of desert pavement (mosaic DP) and bare ground (mosaic BG). We investigated the effects of mosaic DP on water infiltration and vegetation distribution at six sites in fluvial fans (one on a hillside and five within the sectors of fans) along a southwest belt transect in northern Linze County, in the central Hexi Corridor (China). We found significant differences in mosaic DP between the hillside and sector sites in terms of pavement thickness and vesicular horizon thickness (Av thickness), particle composition, and bulk density, although significant differences were absent for mass soil water content, gravel coverage, and surface gravel size. The mosaic DP inhibited water infiltration by the pavement layer, where the sorptivity (S), initial infiltration rate (i_int), steady-state infiltration rate (i_sat) and infiltration time (T) averaged 1.19 cm/min^-0.5, 0.64 cm/min, 0.13 cm/min and 12.76 min, respectively. Where the pavement layer was scalped, the S, i_int, and i_sat increased by 0.27 cm/min^-0.5, 0.52 cm/min, and 0.40 cm/min, respectively, and the T reduced by 7.42 min. Water infiltration was mainly controlled by the pavement layer thickness (+), Av thickness (−), surface gravel coverage (−), fine earth (+) and fine gravel (−) in the pavement layer. The DP surfaces only had a sparse covering of shrubs, but an abundance of herbs. Few shrubs were present on the mosaic DP, but a greater number of shrubs and herbs grew on the mosaic BG. It can be concluded that DPs can maintain vegetation stability for different surface mosaic patterns. This study deepens our understanding of the eco-hydrological cycle of DP landscapes in arid regions.  相似文献   

A conduit-related genesis of the Lengshuiqing intrusive assemblage (Sichuan,SW China)     

Marian Munteanu  Allan H. Wilson  Yong Yao  Shao-Yong Jiang  Gordon Chunnett  Yaonan Luo  Leonard Mafurutu  Rofhiwa Phadagi 《Journal of Volcanology and Geothermal Research》2010,189(1-2):118-130

Lengshuiqing is part of the late Proterozoic igneous province from the western margin of the Yangtze craton. The Lengshuiqing area comprises five ultramafic–mafic intrusions, emplaced in the late Proterozoic Yanbian Group. The intrusions from Lengshuiqing contain cumulate ultramafic zones (peridotite + olivine pyroxenite), with cumulus olivine and Cr-spinel, and intercumulus pyroxenes, hornblende, phlogopite and plagioclase. Ni–Cu ore (pyrrhotite + pentlandite + chalcopyrite) is hosted in the ultramafic zones. Olivine-free diorite–quartz diorite ± gabbro and granite zones commonly occur above the ultramafic rocks. The genesis of the intrusions (conduit-related accumulation or differentiation from stagnant magma) was investigated. The amount of sulphides in the intrusions from Lengshuiqing is one order of magnitude bigger than the sulphides that can be dissolved by a volume of mafic magma similar with the volume of the intrusions. Most intrusions from Lengshuiqing have bulk composition (peridotite ± diorite ± granite) more magnesian (MgO = 21–22%; Mg# > 78) than the deduced composition of their parental magma (MgO = 9–11%; Mg# = 64–67). This indicates the accumulation of sulphide and mafic silicates from a volume of magma much bigger than the volume of the intrusions, which can be explained by the fractionation from magma ascending through the intrusions to shallower depths. A continuous supply and vent of magma is consistent with the lack of chilled margins, the melting of the wall rocks and the generation of high-temperature mineral assemblages (K-feldspar, diopside, and sillimanite) in the Yanbian Group. The intrusions from Lengshuiqing are seen as microchambers on conduits draining olivine-, Cr-spinel-, and sulphide-bearing mafic magma from a larger staging chamber.  相似文献   

ALGEBRAIC ROSSBY SOLITARY WAVE AND BLOCKING IN THE ATMOSPHERE   总被引：2，自引：0，他引：2  

Luo Dehai  Ji Liren 《大气科学进展》1988,5(4):445-454

In this paper, the atmosphere is divided into two regions which are governed by different equations. Furthermore, multiple-scale method is used to obtain the Benjamin-Ono equation satisfied by the nonlinear Rossby wave in weak shear zonal flow. The equation has algebraic solitary wave solution, and the sta-tionary streamfunction fields in the atmosphere are calculated by using numerical method, and the results demonstrate that the stationary solution is antisymmetric dipoles with the anticyclone north of the cyclone, and the structure is similar to the equivalent modon obtained by Mcwilliains (1980), Because the modon obtained here is an algebraic solitary wave, the modon may be called “algebraic modon”, and the stationary algebraic modon is consistent with observations of blocking pattern in the atmosphere.  相似文献   

青藏高原对冷空气爆发影响的个例分析(一)     

罗四维  陈玉春  于学泉 《高原气象》1988,(3)

本文通过对1979年4月10—13日在我国的一次寒潮爆发过程进行了有、无地形及修改地形的数值试验和对比分析,发现高原地形对冷空气活动强度及路径等有明显的影响:(1)由于高原地形的存在使冷空气快速沿地形边缘向南推移,冷锋偏南,给我国平原地区带来较大的降温及较多的降雨。(2)这种冷锋的移动快而达到很偏南的纬度主要是低层冷空气沿高原地形边缘绕流所产生的。(3)如果高原大地形不存在,这时冷空气直侵印度,给印度北方带来强降温。  相似文献   

Rayleigh 阻尼作用下斜拉桥扭转振动     

范家参  罗永康 《地震研究》1988,(4)

在侧向风力或侧向水平地源力作用下,斜拉桥容易发生扭转振动。本文采用非线性Rayleigh阴尼,它能反映在低速振动时有激发而加速振动,至一定高速后又衰减的完整振动过程。对非线性的统辖方程及定解条件,先使之无量纲化,再按非线性项的系数这个小参数展开未知函数,得到线性化的各级近似方程。把待求函数展成梁轴坐标的Fourier级数,其系数为待定的时间函数,应用Fourier级数的正交性,得到求解未知时间函数的二阶常微分方程,完全类似单自由度质点在线性粘滞性阻尼作用下的统辖方程,其解为已知。  相似文献   

中国主要含镍岩体特征及其成因   总被引：8，自引：0，他引：8       下载免费PDF全文

骆华宝  乔德武 《岩石矿物学杂志》1993,12(4):312-324

中国目前已发现7条岩带中18个岩体赋存有工业铜镍矿床。这些含镍岩体的岩石组合有三大类,其中以超基性岩中矿床居多,苏长岩与科马提岩中较少。中国含镍岩浆系列属于科马提岩系列而非拉斑玄武岩系列,含矿岩浆来自上地幔的部分熔融,源区具有U、Th值高而Cr低的特点,深大断裂发育的大陆边缘是镍矿床发育最理想的场所。  相似文献   

游离氧化铁形态转化对红粘土工程性质的影响   总被引：6，自引：5，他引：6  

孔令伟  罗鸿禧 《岩土力学》1993,14(4):25-39

本文通过模拟环境中的有机质使游离氧化铁形态转化对典型红粘土工程性质的影响试验,系统地测试了游离氧化铁的形态分布与物性指标的关系。试验结果表明,在渍水条件下,游离氧化铁的形态转化对红粘土性质的影响不显著,但在渗水条件下,由于游离氧化铁的流失使得胶结作用减弱,它对红粘土工程性质的影响逐渐明显,其潜在的危害仍然是不容忽视的。  相似文献   

耦合海气动力学短期变率的数值研究   总被引：1，自引：1，他引：1  

罗艳  姜达雍  刘屹岷 《热带气象学报》1994,10(2):97-106

为了探索全球性气候变化的年际变率，研制了一个复盖热带太平洋区域的耦合海气模式，并用来模拟ＥＮＳＯ变率的主要特征。数值试验结果与实况比较表明，对１９８２／１９８３年厄尔尼诺事件的主要特征模拟良好。基本结论是要考虑好关键要素和关键过程，即：平均风场和平均海温场；风和海温场的年循环；海洋表面层；三维海温平流；大气（水平方向）水汽辐合效应。  相似文献   

1991年江淮梅雨暴雨与亚洲季风的关系     

乔全明  罗坚  杨信杰  费建芳  陈凤贵 《热带气象学报》1994,10(1):64-68

利用实际大气参数取值进行尺度分析，求得斜压半地转模式中非线性斜压Ｒｏｓｓｂｙ波的非频散周期解的存在条件与解。给出了能够描述非线性特性波动的无量纲拟能效ε，由此推导了非线性特征波动的波速公式及波参数间的一些诊断关系。  相似文献   

滇东黔西晚二叠世早期辫状河三角洲沉积体系及其聚煤特征   总被引：5，自引：2，他引：5  

邵龙义  张鹏飞  陈代钊  罗忠 《沉积学报》1994,(4)

滇东黔西上二叠统底部发育着一套玄武岩质砾岩，本文针对云南富源和贵州盘县一带的底砾岩进行综合研究，认为这套砾岩为辫状河三角洲沉积，并进一步识别出砾质辫状河道、砂质辫状河道、砾质河口坝、砂质河口坝等沉积类型。文中还对该辫状河三角洲的沉积序列、发育背景以及与聚煤作用关系等问题做了一定分析，认为三角洲朵体之间地区以及在衰退的三角洲朵体之上成煤较好。  相似文献