Ecohydrological change mechanism of a rainfed revegetation ecosystem at southeastern edge of Tengger desert,Northwest China     

Xiao  Honglang  Cheng  Guodong  Li  Xinrong  Song  Yaoxuan  Wang  Xinping 《中国科学:地球科学(英文版)》2004,47(1):71-77

Study is made on a 45 km-long artificial ecosystem without irrigation in Tengger desert on the basis of long-term ecological monitoring and ecohydrological fundamentals. Changes in water allocation, utilization, cycle and balance patterns in more than 40-year evolution of the soil-plant system are analyzed. The formation of a drought horizon in shrub rhizosphere and its effect, ecohydrological function of the crust and its effect on the soil-plant system change are discussed. Driven by water self-regulation and water stress, the soil-plant system is going to develop towards the steppe desert to ensure more effective use and optimum collocation of water resource.

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Free radical scavenging abilities of polypeptide from Chlamys farreri   总被引：1，自引：0，他引：1  

韩志武  初晓  刘成娟  王跃军  孙谧  王春波 《中国海洋湖沼学报》2006,24(3):325-328

1 INTRODUCTION Active oxygen free radicals can damage cell structure, even kill the cells, causing aging and cer- tain serious diseases (Bors et al., 1989). Usually, the production and scavenging of active oxygen free radicals are in balance in healthy hu…  相似文献   

Zircon U–Pb and Hf isotopic study of gneissic rocks from the Chinese Altai: Progressive accretionary history in the early to middle Palaeozoic     

Min Sun  Chao Yuan  Wenjiao Xiao  Xiaoping Long  Xiaoping Xia  Guochun Zhao  Shoufa Lin  Fuyuan Wu  A. Kröner 《Chemical Geology》2008,247(3-4):352-383

Gneissic rocks in the Chinese Altai Mountains have been interpreted as either Paleozoic metasedimentary rocks or Precambrian basement. This study reports geochemical and geochronological data for banded paragneisses and associated gneissic granitoids collected along a NE–SW traverse in the northwestern Chinese Altai. Petrological and geochemical data suggest that the protoliths of the banded gneisses were possibly immature sediments with significant volcanic input and that the gneissic granitoids were derived from I-type granites formed in a subduction environment. Three types of morphological features can be recognized in zircons from the banded gneisses and are interpreted to correlate with different sources. Zircons from five samples of banded paragneiss cluster predominantly between 466 and 528 Ma, some give Neoproterozoic ages, and a few yield discordant Paleoproterozoic to Archean ages. Zircon Hf isotopic compositions indicate that both juvenile/mantle and crust materials were involved in the generation of the source rocks from which these zircons were derived. In contrast, zircons occur ubiquitously as elongated euhedral prismatic crystals in the four samples of the gneissic granitoids, and define single populations for each sample with mean ages between 380 and 453 Ma. The general absence of Precambrian inheritance and positive zircon ?Hf values for these granitoids suggest insignificant crustal contribution to the generation of the precursor magmas. Our data can be interpreted in terms of a progressive accretionary history in early to middle Palaeozoic times, and the Chinese Altai may possibly represent a magmatic arc built on a continental margin dominated by Neoproterozoic rocks.  相似文献   

山东小清河的原生动物   总被引：1，自引：1，他引：1  

田家怡 《海洋湖沼通报》1995,(1):33-37

本文根据对山东小清河多年的污染生态调整研究，报导了淡水原生动物１４种。  相似文献   

海洋石油管道单点提升分析   总被引：3，自引：0，他引：3  

邢静忠  柳春图等 《海洋工程》2002,20(3):29-33

基于管道微单元体平衡建立了海管单点提升的非线性力学模型的控制微分方程组 ,使用变弧长的无量纲代换将动边界问题化为固定边界的两点边值问题 ,利用Maple环境下编制的两点边值问题的打靶法程序得到了该问题在各个提升阶段的数值解答和在单点提升过程中管道的极限弯矩约为 0 .71q1 3(EI) 2 3。  相似文献   

东海冲绳海槽深海鱼类报告   总被引：1，自引：0，他引：1  

田明诚  孙宝龄 《海洋科学集刊》1982,(19):115-128

冲绳海槽位于东海大陆架浅水区的外缘,是一北东一南西向延伸,在东南方向呈弧形突出的海槽。其北部水深在500-1000米间,南部最深达2000余米。1978年6,7月间我所“金星”号调查船在这一深水区及其附近进行了海洋综合考查。在进行底栖生物拖网时,获得一些深海鱼类标本。本文共报道深海鱼类14种,隶14属,12科,9目。  相似文献   

厦门港潮汐水流及浑水悬沙整体模型设计     

徐啸 《台湾海峡》1995,(2)

厦门港潮汐水流及浑水悬沙整体物理模型于1989年建成后，已进行了不少有意义的试验研究工作，取得较好效果。本文主要介绍模型的设计思想、相似准则、浑水悬沙相似理论的探讨、模型设计方法以及模型沙的选择等。  相似文献   

海藻糖类的气相色谱分析 Ⅱ.红藻及红藻多糖中D-半乳糖和3, 6-内醚半乳糖的测定     

张燕霞  范晓 《海洋科学集刊》1985,(25):73-80

红藻中的糖类主要以多糖形式存在(琼胶、卡拉胶等)，其中主要的单糖组分是D-半乳糖和3, 6-内醚半乳糖，除此之外还含有少晕的木糖、葡萄糖及甘露糖等成分。由于各单糖的相互干扰，难以用比色等着通化学分析方法对每一种单糖准确地定性定量。作者曾研究过褐藻中单糖的气相色谱测定法, 但该法不能测定3, 6-内醚半乳糖，囚为这种内醚糖对酸水解不稳定。据Dutton和Nozawa等人报道, 将多糖经甲醇分解后进行气相色谱分析，结果令人满意。本文用琼胶(Difco bacto-agar)作代表，研究探讨了红藻胶甲醇-HCI分解的条件，确定了红藻胶中D-半乳糖和3, 6-内醚半乳糖的气相色谱分析方法，并将其应用于红藻中D-半乳糖和3, 6-内醚半乳糖的分析。  相似文献   

Simulations of Annual Cycle of Phytoplankton Production and the Utilization of Nitrogen in the Yellow Sea     

Tian?TianEmail author  Hao?Wei  Jian?Su  Changsoo?Chung 《Journal of Oceanography》2005,61(2):343-357

A nutrient dynamic model coupled with a 3D physical model has been developed to study the annual cycle of phytoplankton production in the Yellow Sea. The biological model involves interactions between inorganic nitrogen (nitrate and ammonium), phosphate and phytoplankton biomass. The model successfully reproduces the main features of phytoplankton-nutrient variation and dynamics of production. 1. The well-mixed coastal water is characterized by high primary production, as well as high new production. 2. In summer, the convergence of tidal front is an important hydrodynamic process, which contributes to high biomass at frontal areas. 3. The evolution of phytoplankton blooms and thermocline in the central region demonstrate that mixing is a dominant factor to the production in the Yellow Sea. In this simulation, nitrate- and ammonium-based productions are estimated regionally and temporally. The northern Yellow Sea is one of the highly ranked regions in the Yellow Sea for the capability of fixing carbon and nitrogen. The annual averaged f-ratio of 0.37 indicates that regenerated production prevails over the Yellow Sea. The result also shows that phosphate is the major nutrient, limiting phytoplankton growth throughout the year and it can be an indicator to predict the bloom magnitude. Finally, the relative roles of external nutrient sources have been evaluated, and benthic fluxes might play a significant role in compensating 54.6% of new nitrogen for new production consumption.  相似文献   

几种养殖鲍同工酶生化遗传的比较研究   总被引：8，自引：0，他引：8  

柯才焕  陈晓佳  周时强  王志勇  王艺磊 《台湾海峡》2003,22(2):173-179,T002

运用聚丙烯酰胺凝胶电泳对我国主要养殖鲍(皱纹盘鲍、盘鲍及九孔鲍)12种同工酶(LDH、ME、MDH、GPI、PGM、IDH、IDDH、SOD、EST、ODH、ADH、AAT)26个基因座位进行了分析．结果表明：EST、PGM可以作为区分三种(亚种)鲍的生化遗传标记；在所分析的位点中，未发现多态现象，表明三种养殖鲍杂合子缺失严重，其主要原因可能在于哑基因、近交与自然选择。  相似文献