长白山北坡草本植物分布与环境关系的典范对应分析

在长白山北坡海拔 70 0～ 2 60 0 m的坡面上 ,海拔每上升 1 0 0 m设立一块样地 ,共计 2 0个样地 ,计测样地中草本层植物的生态重要值和包括气候、土壤、林冠郁闭度等在内的 1 3个环境因子 ,对获得的数据进行典范对应分析 ,作出了种类、样地分布与环境因子关系的二维排序图 ,排序图直观地反映了主要草本植物分布与环境因子间的关系。排序图中环境因子与前两个排序轴的相关系数大小表明 ,海拔高度作为诸多环境因子的综合反映 ,是影响长白山北坡草本植物分布的主导因素 ,除此之外 ,其它环境因子如林冠郁闭度、土壤有机质及有效 N、P、K等因素 ,也对草本植物的分布有较大的影响。高山冻原与 2 0 0 0 m以下森林群落内的草本植物明显不同 ,反映出二种不同类型植被间草本植物组成格局间质的差异

氮沉降对森林生态系统土壤碳库的影响

森林土壤碳库是陆地生态系统碳库的重要组成部分,对维持全球碳平衡具有重要意义。不断加剧的全球氮沉降有可能改变森林生态系统中碳元素的地球化学循环过程,从而引起森林土壤碳储量的变化。本文从森林土壤碳收支的角度,将氮沉降对森林生态系统土壤碳库影响的复杂过程划分为凋落物分解、细根周转、土壤呼吸和土壤可溶性有机碳淋失4个相对独立的过程。综合国内外研究现状,对其进行了简要评述,指出了目前研究的不足,并探讨了这一研究领域的发展方向。

Decomposition of emergent macrophyte roots and rhizomes in a northern prairie marsh

Dry mass, nitrogen and phosphorus content in belowground litter of four emergent macrophytes (Typha glauca Godr., Phragmites australis (Cav.) Trin., Scolochloa festucacea (Willd.) Link and Scirpus lacustris L.) were followed for 1.2 years in a series of experimental marshes, Delta Marsh, Manitoba. Litter bags containing roots and rhizome materials of each species were buried in unflooded soil, or soil flooded at three water depths (1–30, 31–60, > 60 cm). There were few differences in dry mass loss in unflooded or flooded soils, and depth of flooding also had little effect on decomposition rates. In the flooded sites, Scolochloa and Phragmites roots lost more mass (48.9–63.8% and 59.2–85.5%, respectively) after 112 days than Typha and Scirpus (36.3–43.6 and 37.0–47.2%, respectively). These differences continued through to the end of the study, except in the shallow sites where Scirpus roots lost more mass and had comparable mass remaining as Scolochloa and Phragmites. In the unflooded sites, there was little difference between species. All litters lost nitrogen (22.9–90.0%) and phosphorus (46.3–92.7%) during the first 112 days, then levels tended to remain constant. Decay rates for our belowground root and rhizome litters were comparable to published literature values for aboveground shoot litter of the same species, except for Phragmites roots and rhizomes which decomposed at a faster rate (−k = 0.0014−0.0032) than shoots (−k = 0.0003−0.0007, [van der Valk, A.G., Rhymer, J.M., Murkin, H.R., 1991. Flooding and the decomposition of litter of four emergent plant species in a prairie wetland. Wetlands 11, 1–16]).

辽宁山羊绒品质分析

辽宁山羊绒品质分析李文清麻岩＊李亚乔＊王丽霞刘丹张长恩（中国科学院沈阳应用生态研究所，沈阳１１００１５）（＊辽宁省纤维检验所）在制定《山羊原绒》国家标准过程中，先后对全国山羊绒主产区的内蒙古、新疆、辽宁、太行山地区，西北地区进行了调研，采集和索取了全...

三北防护林体系建设面临的机遇和挑战

在总结三北防护林工程(三北工程)30年建设成就和经验的基础上,立足国内外相关领域发展趋势,全面分析了三北工程在应对气候变化、增加农民收入、拉动内需等方面显现的机遇,剖析了立地条件、发展动力、投资水平和改革创新等带来的严峻挑战,总结提出了三北工程未来发展应坚持以建设完备的区域性防护林体系为目标,以防沙治沙、保持水土为主要任务,以服务新农村建设、发展特色产业、推进林权改革为重点的发展思路和具体措施。

图书馆统计·读者心理·潜在信息

<正> 图书馆统计、读者心理、潜在信息,看起来似乎是三个孤立的研究问题,可是在图书馆工作中,若能透过现象看本质,会发现它们常有机地联系在一起,而从中找出一些规律性的东西,将能使我们专业图书馆的工作引向深入。近来,通过工作实践,我在中科院沈阳应用生态所图书馆的图书流通部门做了一些粗略的统计:这个馆库存图书主要有中、日、俄、英4个文种。中文:52856册,西文:19314册:

Impact of carbon dioxide pressurization on liquid phase organic reactions: A case study on Heck and Diels-Alder reactions

Heck coupling reactions of methyl acrylate with various aryl bromides have been investigated using a Pd/TPP catalyst in toluene under pressurized CO2 conditions up to 13 MPa. Although CO2 is not a reactant, the pressurization of the reaction liquid phase with CO2 has positive and negative impacts on the rate of Heck coupling depending on the structures of the substrates examined. In the case of either 2-bromoacetophenone or 2-bromocinnamate, the conversion has a maximum at a CO2 pressure of about 3 MPa; for the former, it is much larger by a factor of 3 compared with that under ambient pressure. For 2-bromobenzene, in contrast, the conversion is minimized at a similar CO2 pressure, being half compared with that at ambient pressure

Synthesis and Upconversion Luminescence Properties of GdF3:Er3+, Yb3+

GdF3:Er3+,Yb-3 with Er3+ ion of 3% and Yb3+ ion concentration of 10%, 20% have been prepared by a hydrothermal method. The results of XRD show that all the samples are of an orthorhombic structure. The average crystallite sizes estimated by Scherrer formula are 28 and 26 nm for Gd0.87Yb0.10Er0.03F3 and Gd0.77Yb0.20Er0.03F3, respectively. The Upconversion luminescence spectra of the samples have been studied under 980 run laser excitation. The results show that the green and red upconversion emission can be attributed to the H-2(11/2),S-4(3/2) -> 4I(15/2) and 4F(9/2) -> 4I(15/2) transitions of Er3+, respectively.