“三北”防护林工程的生态环境评估

“三北”防护林工程的生态环境评估ＥｃｏｌｏｇｉｃＥｎｖｉｒｏｎｍｅｎｔｏｆＥｎｇｉｎｅｅｒｉｎｇｏｆＳｈｅｌｔｅｒｂｅｌｔＮｅｔｗｏｒｋｉｎＮｏｒｔｈ，ＮｏｒｔｈｗｅｓｔａｎｄＮｏｒｔｈｅａｓｔＣｈｉｎａ￥肖笃宁（中国科学院沈阳应用生态研究所，沈阳１...

长白山阔叶红松林近22年的气候动态

长白山阔叶红松林作为典型的温带森林生态系统,其长期的气候动态状况对研究全球变化具有重要的意义。本文采用中国科学院长白山森林生态系统定位站气象观测场1982~2003年的地面常规气象观测资料,对长白山阔叶红松林的光能因子(包括年日照时数、年日照百分率)、热量因子(包括年平均气温、1月、7月月平均气温、年极端最高、最低气温、年积温)、水分因子(包括年总降水量、年最大雪深、相对湿度、年总蒸发量)、以及年平均风速与风向等气候因子进行了分析,从而得出这些因子22年的平均值及其动态变化趋势,进而为相关领域的研究提供基础资料。

金银忍冬和榆叶梅春季光合特性的比较

应用LI-6400便携式光合测定系统对金银忍冬(Loniccra maackii)和榆叶梅(Prunus triloba)春季光合作用的日变化规律进行研究,利用SPSS统计分析软件,采用相关分析及回归分析得出净光合速率与光合有效辐射、气温、大气湿度、气孔导度等生理生态因子间的相关关系。结果表明:金银忍冬春季光合速率呈双峰曲线,17∶00出现一个小高峰,影响光合速率的主要因子为气孔导度(Gs)、光合有效辐射(PAR)、大气相对湿度(RH)、胞间CO2浓度(Ci);榆叶梅春季光合速率呈双峰曲线,影响光合速率的主要因子为光合有效辐射(PAR)、气孔导度(Gs);金银忍冬较榆叶梅春季净光合速率大。

林带疏透度数字化测度方法的改进及其应用研究

在大量野外调查基础上 ,用数码相机拍摄林带相片 ,采用CIAS软件测定林带疏透度 ,对已有“数字图像处理法”进行了改进 ,并对疏透度的变化规律进行了深入研究 .结果表明 ,用改进的数字化方法测定林带的疏透度 ,比用光学相机所进行的“数字图像处理法”精度高 ,更经济、简捷 ;林带疏透度 β与相对枝下高x(枝下高 /林带平均高 )的关系无叶期可表达为 β =1.0 6 81x0 .4 3 0 4 (r =0 .976 3,r0 .0 1=0 .40 73) ;有叶期可表达为 β =0 .6 72x0 .4 69(r =0 .985 1,r0 .0 1=0 .40 73) (0≤β≤ 1) ;β随着林龄a呈抛物线式变化 ,β =0 0 0 0 9a2 - 0 .0 36 4a +0 .6 82 8(0≤β≤ 1) ;提出的林带断面疏透度 β0 是定量反映林带断面结构的定量评价指标 ,同时可作为评价林带结构的辅助指标 ;提出混交林带的疏透度计算式 β =(β1n1+β2 n2 ) / (n1+n2 ) ;在相同配置不同树种的纯杨、柳、榆林带结构以杨树林带结构较好 ,柳树林带结构次之 ,疏透度值 βPPP<βSSS<βUUU;在树种相同、配置不同时 ,品字形优于矩形 ;杨柳榆的混交林带中杨榆株间、杨柳对称式行间SPPS混交方式结构防护效果较好

黄土丘陵第Ⅱ副区坝地资源潜力与坝系建造模式

在分析延安市宝塔区、安塞县南部 7乡镇的沟壑密度、布坝密度、现有坝地面积占耕地面积比重的基础上 ,提出了该区今后发展坝地的规模及淤地坝建设模式

香港植物水分生理学和水土保持专家 张建华博士

张建华 ,男 ,1 95 6年出生于江苏省金坛县 ,1 982年毕业于江苏农学院 (现为扬州大学 )农学系农学专业。 1 985年赴英国进修 ,1 988年在英国兰卡斯特大学获博士学位 ,1 988— 1 991年在该校受聘继续做博士后研究员。一直从事植物根土关系及缺水条件下根系感知土壤缺水信号传递研究工作。已在国内、外学术刊物上发表论文 70余篇 ,其中 SCI期刊论文 5 0余篇 ,并被国际上许多同行专家多次引用 ,受邀撰写综述1 0余篇 ,参加各类国际会议 2 0余次 ,特别是受《Annual Review of Plant Physiologyand Molecular Biology》编辑部邀请 ,与导师合作发表综述 (1 991 )文章 ,以自己的系统研究为基础 ,对植物感知土壤干旱信号及其生长发育调节做了详细评述 ,是根源信号理论体系建立的代表性论文 ,构成了目前根信号理论体系的基础 ,被认为是该研究领域最为重要的论文。现已被国内外多种教科书引用和介绍。另外在国际著名植物生理学家 W.J.Davies指导下 ,在英国兰卡斯特大学攻读博士期间于 1 987年在植物学界享有盛誉的《Journal o...

怎样实现退耕还林还草

黄土高原是我国水土流失最为严重的地区 ,也是西部大开发中生态环境建设重点实施区域之一。1 999年朱基总理视察陕北时提出的“退耕还林 (草 ) ,封山绿化 ,个体承包 ,以粮代赈”1 6字政策措施切中了黄土高原水土流失严重地区的要害问题 ,也是这一地区实现山川秀美和可持续发展的必由之路。但如何使这一政策措施得到全面贯彻 ?需要付出艰苦的努力。在建国初期 ,通过数年大规模科学考察就曾经提出 ,滥垦滥牧是造成黄土高原严重水土流失和人民生活贫困的主要原因 ,应将实现“土地合理利用”作为黄土高原综合治理的核心问题。 1 980年 ,中央领导对当时在黄土高原飞机播种“沙打旺”获得成功作了批示 ,认为“很有意义” ,“效果好 ,成本低” ,“在西北各省 ,建立专门机构 ,组织实施”。 1 983年 ,针对延安、榆林等地情况 ,中央领导又作出“种草种树发展畜牧是改变中国干旱地区面貌的根本大计”的指示 ,随后一个时期内在黄土高原掀起了种草种树的高潮。在科学实验方面 ,1 985年至今连续 1 5年时间 ,作为国家科技攻关项目 ,在黄土高原不同类型区建立了 1 1个试区 ,进行综合治理研究与示范 ,在此期间还组织了第 2次对...

Construction of coordination networks with high connectivity: a new 8-connected self-penetrating network based on tetranuclear metal clusters

Two highly connected cobalt(II) and zinc(II) coordination polymers with tetranuclear metal clusters as the nodes of network have been prepared, being the first example of an 8-connected self-penetrating net based on a cross-linked alpha-Po subnet.

The role of molybdenum oxide as anode interfacial modification in the improvement of efficiency and stability in organic light-emitting diodes

It has been experimentally found that molybdenum oxide (MoO3) as the interfacial modification layer on indium-tin-oxide (ITO) in organic light-emitting diodes (OLEDs) significantly improves the efficiency and lifetime. In this paper, the role of MoO3 and MoO3 doped N,N '-di(naphthalene-1-yl)-N,N '-diphenyl-benzidine (NPB) as the interface modification layer on ITO in improvement of the efficiency and stability of OLEDs is investigated in detail by atomic force microscopy (AFM), polarized optical microscopy, transmission spectra, ultraviolet photoemission spectroscopy (UPS) and X-ray photoemission spectroscopy (XPS).

Selective hydrogenation of citral catalyzed with palladium nanoparticles in CO2-in-water emulsion

CO2-in-Water (C/W) emulsion was formed by using a nonionic surfactant of poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (P123), and palladium nanoparticles were synthesized in situ in the present work. The catalytic performance of Pd nanoparticles in the C/W emulsion has been discussed for a selective hydrogenation of citral. Much higher activity with a turnover frequency (TOF) of 6313 h(-1) has been obtained in this unique C/W emulsion compared to that in the W/C microemulsion (TOF, 23 h(-1)), since the reaction was taking place not only in the surfactant shell but also on the inner surface of the CO2 core in the C/W emulsion. Moreover, citronellal was obtained with a higher selectivity for that it was extracted to a supercritical carbon dioxide (scCO(2)) phase as formed and thus its further hydrogenation was prohibited. The Pd nanoparticles could be recycled several times and still retain the same selectivity, but it showed a little aggregation leading to a slight decrease in conversion.

Controllable synthesis of highly luminescent and monodisperse CdS nanocrystals by a two-phase approach under mild conditions

Highly luminescent and monodisperse CdS nanocrystals (see Figure) have been synthesized using a two-phase approach. The synthesis of CdS nanocrystals at the liquid-liquid interface was easy, safe, and highly reproducible, and the reaction conditions were mild and controllable.

老年性白内障晶状体中金属元素的人工神经网分析

由Ｋ、Ｎａ、Ｃａ、Ｍｇ、Ｆｅ、Ｃｕ、Ｚｎ和Ｍｎ在老年性晶状体中的含量，运用人工神经网法成功地将老年性白内障、白内障晶状体核和正常人晶状体划分为３类。同时讨论了神经网的结构（层数及每层的结点数）、初始权重等对神经网性能的影响。随机地将３０个晶状体分为训练集和测试集，其识别率及预测率均达到１００％。

两步激光诱导荧光法测量铀原子高激发态寿命

铀原子的能级寿命在激光分离铀同位素工程中是赖以选择合宜分离路线的不可缺少的数据。但铀的能级众多密集,光谱非常复杂,气化温度很高(≥2500K),又具有放射性,故其能级寿命测量在技术上是复杂的。铀原子高激发态寿命的成功测量标志着原子能级寿命测量的成就。迄今已发表的铀原子能级寿命(百余个)只占其能级数目的极小部分。我们曾用铀空心阴极灯作为蒸气源,以光电流法测量了一些基态跃迁能级的相对振子强度,和以激光诱

Trace element composition of peridotites from the southern Mariana forearc: Insights into the geochemical effects of serpentinization and/or seafloor weathering

Peridotites from the southern Mariana forearc were sampled on the landward trench slope of the Izu-Bonin-Mariana (IBM) subduction zone by dredging. These mantle wedge peridotites underwent hydration by fluid derived from a dehydrated descending slab, and later interacted with seawater after emplacement at or near the seafloor. This study investigates how these two different rock-fluid interaction processes influenced trace element distribution in the southern Mariana forearc peridotites. We measured trace element concentrations of peridotites from the southern Mariana forearc. The southern Mariana forearc peridotites are characterized by a distinct seawater-like REE pattern with an obvious negative Ce anomaly, and La shows good correlation with other REEs (except Ce). In addition, there is a great enrichment of U, Pb, Sr and Li elements, which show a distinct positive anomaly relative to adjacent elements in the multi-element diagram. For the seawater-like REE pattern, we infer that REEs are mainly influenced by seawater during peridotite-seawater interactions after their emplacement at or near the seafloor, by serpentinization or by marine weathering. Furthermore, the anomalous behavior of Ce, compared with other rare earth elements in these samples, may indicate that they have undergone reactions involving Ce (IV) when the peridotites interacted with seawater. Positive U, Pb, Sr and Li anomalies are inferred to be related to seawater and/or fluids released during dehydration of the subducting slab.