排序方式: 共有39条查询结果,搜索用时 187 毫秒
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本文研究澳大利亚新英格兰地区开阔林的群落结构特征。结果表明其种类组成较为简单,调查的4.8公顷样地中树木层只有18种。隶属于4属4科,树木个体90%为桉树;灌木层有32种19属13科;草本层有95种20属10科。群落的垂直结构为三层:树层,灌木层和草本层;一些林段只有二层(缺灌木层),或四层(增多小树层)。优势种群的分布格局多为集群分布。非优势种群的分布格局则多为随机分布格局。种间联结现象较弱,除少数种对外,联结系数低或没有联结。种间生态位的重叠值低,反映了诸多种群的独立分布特征。在其组织结构水平上,除草本层外。物种多样性指数、群落均匀度、生态优势度均较低。反映群落的优势种明显,为种多群落类型。 相似文献
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刘艳萍 《广西民族大学学报》2001,(Z1)
作者读了美国小说之父安德生最著名的短篇小说《树林之死》 ,采用第一人称次要人物手法描绘了 2 0世纪 30年代美国中西部农村的悲惨命运。作者别具一格的写作手法在当时是一种伟大的创新 ,受到读者和作家的喜爱到 2 0世纪六七十年代这种写作方法是席卷美国 相似文献
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无 《延安大学学报(自然科学版)》2012,31(2):F0003-F0003
任树林,男,汉族,1957年10月生,陕西米脂县人,中共党员,延安大学教授,硕士研究生导师。1982年7月于西北大学化学系分析专业毕业分配到陕西省黄土高塬综合治理研究所,主要从事土壤、肥料和植物种子等分析化验工作。1983年9月至1984年7月赴西安外国语学院出国留学预备生培训部学习英语。 相似文献
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FORTIN Danielle 《科学通报(英文版)》2009,54(11):1931-1940
An ancient wood layer dated at about 5600 cal. a BP by AMS14C dating was discovered in the intertidal zone, East China Sea. Samples affected by ancient woods, including fresh coast bedrock, weathering bedrock, seepage water from coast, seepage water from ancient wood layer, intertidal seawater, fresh water, beach mud, ancient wood barks and ancient peat, were collected for geochemical analysis. The beach mud and the bacteriogenic iron oxides (BIOS) in coastal seepage water were analyzed by min- eralogical and high-resolution transmission electron microscopy (HRTEM)-selected area electron dif- fraction (SAED) analysis. Inorganic sulfur compositions and b'34S of the ancient peat and the beach mud were determined. The results showed that Fe, Mn, S (SO~-) were enriched in the intertidal area at different levels, very likely caused by fermentation of ancient woods. The presence of abundant iron- oxidizing bacteria (FeOB) and sulfate-reducing bacteria (SRB) in this intertidal zone was confirmed by HRTEM-SAED observation, and these bacteria were involved in Fe-S cycle to induce extracellular biomineralization. The negative ~4Sv.cDT (--2.9%o) likely indicated the biogenic origin of iron-sulfide minerals in the beach mud at high sulfate reduction rate (SRR). These findings are helpful for under- standing the biogeochemical Fe-S cycle and biomineralization process at high organic matter deposition rate and high SRR in the intertidal zone, estuary, or near shoreline. 相似文献
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