青藏高原东缘人工草地群落结构和土壤养分对选择效应的影响

实验以青藏高原高寒草地常见物种垂穗披碱草(Elymus nutans)、中华羊茅(Festuca sinensis)和羊茅(Festuca ovina)为材料, 通过建植单、混播植物群落, 及连续5年对其生产力的测定, 来探索物种组成、丰富度、播种密度和土壤养分对群落选择效应的影响, 以及群落选择效应随时间的变化趋势。结果表明: 凡包含有垂穗披碱草物种的群落均有较高的选择效应, 说明物种组成显著影响群落的选择效应; 实验初期, 群落选择效应随物种丰富度和播种密度的增大而升高; 然而, 随着生长年限的延长, 物种丰富度和密度的效应却呈逐减弱趋势; 施肥对群落选择效应的影响从最初的显著提高转变为影响不显著, 到最后反而减弱了群落的选择效应; 从群落成长过程来看, 群落的选择效应值有逐渐减弱的趋势。     

施肥和刈割对青藏高原东部高寒草甸群落生物量补偿效应的影响

通过对青藏高原东部高寒草甸植物群落在4个施肥处理及7个刈割水平下的群落生物量、物种丰富度和补偿指数的比较,分析了该类草甸群落主要特征对施肥及刈割强度差异的响应.结果表明:施肥显著增加了群落生物量,并降低物种丰富度,而刈割处理虽然增加了物种丰富度,但对群落生物量无显著影响;随着施肥量的增加,高寒草甸由莎草科和杂草类物种占优势的群落构成逐渐向禾本科物种占优势的群落构成转变;施肥可提高群落的补偿能力,在不同施肥梯度中,刈割后植物群落补偿能力也不相同;随着施肥量的增加,增加刈割强度,减少刈割次数,发生超补偿的机率增大;可见,施肥是主效应,刈割对群落主要特征的影响随营养水平的不同而发生变化.     

青藏高原东缘人工草地群落物种丰富度对杂草入侵的影响

物种丰富度和生态系统功能间的关系是近年来生物多样性研究的中心问题,其中群落抗杂草入侵是其功能的重要表现形式。本文利用青藏高原东缘地区3种野生优良牧草：垂穗披碱草(Elymus nutans)、中华羊茅(Festuca sinensis)和羊茅(F. ovina),构建人工草地群落,探讨了物种丰富度与杂草入侵能力间的相互关系及其潜在的作用机理。结果表明：随着群落中物种丰富度的增加,入侵杂草的物种数、秧苗数和生物量均表现为显著下降趋势(P＜0.05);杂草的物种数、秧苗数和生物量间存在极显著的正相关(P＜0.01);群落的物种丰富度与入侵杂草间的负相关关系可能是选择效应和补偿效应共同作用的结果;2004—2007年,群落中入侵杂草的物种数和生物量有增加趋势,而秧苗数的变化趋势不明显。     

土壤肥力和物种属性决定亚高寒草甸实验群落的生产力

生物多样性与生态系统功能之间的关系及其形成的内在机制还存在很多争议。为了揭示植物群落生产力形成的生态学机制, 采用盆栽方法探讨了物种多样性、物种属性以及施肥水平与植物群落生产力之间的关系。研究结果显示: 在不施肥和每盆施5.0 g磷酸二铵的条件下, 随着物种多样性的增加, 地上生物量增加不显著; 在每盆施10.0 g磷酸二铵的条件下, 随着物种多样性的增加, 地上生物量显著增加。相对于中华羊茅(Festuca sinensis)而言, 垂穗披碱草(Elymus nutans)和垂穗鹅观草(Roegneria nutans)对群落生产力的贡献较大, 但在不同施肥水平和播种密度下, 其影响不完全相同。这表明物种多样性对群落生产力的影响随着土壤肥力的变化而变化; 并且植物群落生产力受组成群落的物种属性影响较大, 而物种属性又与特定时间和特定生境下资源的利用方式相联系。在高肥力水平下, 物种多样性之所以对群落生产力具有正效应, 可能是因为高肥力水平增加了可利用的生态位空间, 最终仍体现在物种组合上。因此, 植物群落的生产力与物种多样性之间没有必然的联系, 而与土壤肥力和土壤肥力决定的物种属性有关。     

长期施肥对黄土高原典型草原群落稳定性的影响及机制研究

施肥是当前草地生态系统最常见的人为干扰方式之一,可导致草地生物多样性和生态系统稳定性发生显著变化。该研究以黄土高原典型草原为研究对象,通过连续8年的氮肥(尿素)野外添加试验,分析不同氮肥处理(分别为0、5、10、20、40和80 g·m^-2)对草地群落稳定性的影响,并分析检验可能影响群落稳定性的四个潜在机制(物种多样性、物种同步性、投资组合效应和优势度),以明确施肥对群落稳定性的影响及其潜在机制,为黄土高原恢复草地的合理利用提供理论依据。结果表明:(1)随着施肥水平的增加,群落稳定性(S)降低,并在施肥处理为20 g·m^-2时开始极显著下降(P<0.01)。(2)施肥极显著降低了物种的丰富度(R)和优势度指数(D)(P<0.01),但物种同步性(B)和均值-方差的比例指数(z)并没有发生显著变化(P>0.05)。(3)物种丰富度(R)与群落稳定性(S)之间呈正相关关系,而优势度指数(D)与群落稳定性(S)不相关。研究认为,在人为施肥干扰下,黄土高原典型草原的物种丰富度下降导致群落稳定性下降,表明物种多样性对维持草地群落稳定具有重要作用。     

亚高寒草甸群落结构决定群落生产力实例验证

在植物物种丰富度与生产力之间关系的研究中,多以物种丰富度和生产力作为双变量,常常忽略在同一物种丰富度水平下可能影响群落生产力的其他因素,例如物种组合与组成等。该研究采用盆栽法,以中华羊茅(Festuca sinensis)、垂穗披碱草(Elymus nutans)、鸭茅(Dactylis glomerata)和紫花苜蓿(Medicago sativa)为研究对象,设置4个物种丰富度水平(1、2、3、4),并在最高物种丰富度水平下,保持总种植密度不变,改变各组成物种的相对比例(10%、20%、30%、40%),探讨群落物种组合、组成及物种所属功能群对群落生产力的影响。结果表明:1)在较低物种丰富度下,群落生产力随物种丰富度增加而增加,在较高物种丰富度下,群落生产力随物种丰富度的增加不再显著变化。2)群落物种组合及组成对群落生产力具有显著影响,配置垂穗披碱草的群落及垂穗披碱草占比大的群落具有更高生产力。3)混播物种所属功能群对群落生产力具有显著影响,豆科植物对其他混播物种生产力表现出促进或抑制作用,禾本科物种垂穗披碱草对群落生产力有正效应，中华羊茅和鸭茅对群落生产力影响不明显。由此推测,物...     

氮素添加对科尔沁沙质草地物种多样性和生产力的影响

物种多样性和生产力是生态系统结构和功能的重要指标.以科尔沁沙质草地为对象,通过对其进行不同梯度的氮素添加处理,研究氮素添加对沙质草地生态系统物种组成、物种多样性和生产力的影响.结果表明：氮素添加改变了群落物种组成和群落中的优势种,使植被的高度和盖度增加,植被的透光率减小;随着氮素水平的增加,群落中物种丰富度减小,物种多样性降低;不同水平的氮素添加均显著增加了(P<0.01)群落地上生物量;物种丰富度与植被透光率呈线性正相关(P<0.01),与植被盖度呈线性负相关关系(P<0.01),说明长期的氮沉降与人为氮素输入将影响沙地生态系统的物种组成、物种多样性以及生产力.     

施肥和刈割对垂穗披碱草（Elymus nutans）、中华羊茅（Festuca sinensis）和羊茅（Festuca ovina）种间竞争力的影响

试验选用青藏高原东部高寒草甸普遍存在的3种禾本科牧草垂穗披碱草(Elymus nutans)、中华羊茅(Festuca sinensis)以及羊茅(Festuca ovina)进行种间竞争的野外研究.通过测定3种牧草生物量的干重,对其进行方差分析并计算了相对产量总和(RYT)以及竞争率(CR).结果如下:对实验物种竞争率(CR)的分析表明垂穗披碱草的竞争力最强,中华羊茅次之,羊茅最差.施肥和刈割处理对于原来的竞争格局没有影响,即在施肥、刈割及其交互作用下3种牧草的竞争等级均是一致的.对试验物种混播的相对产量总和(RYT)的分析表明:在中华羊茅与垂穗披碱草的混播中,两种组成物种利用相同的资源,表现出相互竞争的趋势,这种趋势是非密度依赖的;垂穗披碱草和羊茅混播,在低密度时,羊茅和垂穗披硷草可以共享资源,但是随着密度增加,羊茅和垂穗披碱草表现出竞争相同资源的趋势;在中华羊茅和羊茅的混播中,二者在生长过程中能够共享资源,有相互促进的趋势,表现出共生的关系,且是非密度依赖的.     

科尔沁沙地封育恢复过程中植物群落特征变化及影响因素

封育是退化沙地植被恢复与生态重建的重要措施, 理解长期处于封育状态下不同类型沙地植物群落特征变化及其影响因素有利于沙地植被恢复和生态重建。该文基于对科尔沁沙地长期封育的流动沙丘(2005年封育)、固定沙丘(1985年封育)和沙质草地(1997年封育)连续多年(2005-2017年)的植物群落调查, 结合土壤种子库、土壤养分以及气象数据, 分析了植物群落特征变化及其对环境变化的响应。研究结果表明流动沙丘植被盖度显著增加, 群落生物量和物种多样性年际间波动变化, 但无明显趋势; 固定沙丘植物群落存在逆行演替趋势, 具体表现为群落生物量、灌木和半灌木以及豆科优势度显著下降, 而一年生和多年生杂类草优势度显著增加; 沙质草地群落物种丰富度和多年生禾草优势度存在降低趋势, 并且一年生杂类草优势度明显高于其他功能群, 群落存在退化现象。3类沙地土壤种子密度变化不显著, 而种子丰富度在流动沙丘显著增加, 在固定沙丘和沙质草地有下降趋势, 土壤养分仅有有效氮和有效磷含量增加。回归分析结果表明气温和降水是影响年内生物量积累的主要因素, 但对年际间群落生物量和物种丰富度变化影响不大。除趋势对应分析结果显示土壤种子库与植物群落之间存在很高的相似性, 典型相关分析结果表明沙质草地植物群落与土壤养分紧密相关, 而固定沙丘群落主要与土壤水分紧密相关。综合以上结果可知, 封育33年的固定沙丘群落和封育21年的沙质草地群落都存在退化现象, 而封育11年的流动沙丘群落正在缓慢恢复, 因此封育年限的设定对退化沙地植被恢复至关重要, 封育时间过长不仅不利于植物群落恢复, 反而会使群落发生逆行演替, 建议封育年限的设定应综合考虑植被退化程度、土壤养分状况、土壤种子库基础以及气候条件等因素的影响。     

科尔沁沙地封育恢复过程中植物群落特征变化及影响因素

封育是退化沙地植被恢复与生态重建的重要措施,理解长期处于封育状态下不同类型沙地植物群落特征变化及其影响因素有利于沙地植被恢复和生态重建。该文基于对科尔沁沙地长期封育的流动沙丘(2005年封育)、固定沙丘(1985年封育)和沙质草地(1997年封育)连续多年(2005–2017年)的植物群落调查,结合土壤种子库、土壤养分以及气象数据,分析了植物群落特征变化及其对环境变化的响应。研究结果表明流动沙丘植被盖度显著增加,群落生物量和物种多样性年际间波动变化,但无明显趋势;固定沙丘植物群落存在逆行演替趋势,具体表现为群落生物量、灌木和半灌木以及豆科优势度显著下降,而一年生和多年生杂类草优势度显著增加;沙质草地群落物种丰富度和多年生禾草优势度存在降低趋势,并且一年生杂类草优势度明显高于其他功能群,群落存在退化现象。3类沙地土壤种子密度变化不显著,而种子丰富度在流动沙丘显著增加,在固定沙丘和沙质草地有下降趋势,土壤养分仅有有效氮和有效磷含量增加。回归分析结果表明气温和降水是影响年内生物量积累的主要因素,但对年际间群落生物量和物种丰富度变化影响不大。除趋势对应分析结果显示土壤种子库与植物群落之间存在很高的相似性,典型相关分析结果表明沙质草地植物群落与土壤养分紧密相关,而固定沙丘群落主要与土壤水分紧密相关。综合以上结果可知,封育33年的固定沙丘群落和封育21年的沙质草地群落都存在退化现象,而封育11年的流动沙丘群落正在缓慢恢复,因此封育年限的设定对退化沙地植被恢复至关重要,封育时间过长不仅不利于植物群落恢复,反而会使群落发生逆行演替,建议封育年限的设定应综合考虑植被退化程度、土壤养分状况、土壤种子库基础以及气候条件等因素的影响。     

Uniform hypothesis of cell behavior--movement, contact inhibition of movement, adhesion, chemotaxis, phagocytosis, pinocytosis, division, contact inhibition of division, fusion.

The cell has been represented as a charged liquid drop. Contrary to the DLVO-theory, the effect of the surface potential upon the value of the interfacial tension of the cell membrane has also been taken into consideration. The cell membrane has visco-elastic properties and its constituents may move against each other. Cell movement is caused by the appearance of a small number of the electrically charged constituents of the cell membrane on the leading edge of the cell. This produces a local decrease in the surface tension and the cell membrane expansion. At the moment of contact between two cells proton transfers occur between the strongly negatively charged microvilli of one cell and the body of the other, analogous to a condenser breakdown. This, through the effect on the surface tension, causes contact inhibition of movement. The distribution of the proton dissociable groups modifies the interaction between the cells (differentiation) and between the cell and the substratum (adhesion). Adsorption of the charged compounds at the surface of the cell membrane, decreasing the surface potential and increasing the surface tension, causes the phenomena of chemotaxis, phagocytosis and pinocytosis. Cell division, considered in the terms of the surface energy, requires an adequate supply of considerable quantities of energy inversely proportional to the surface potential value. In case of a reduction of the distance between the cells, their surface potential and the energetic barrier of the cell division processes increases, and causes contact inhibition of cell division. Due to their high charge, division of neoplastic cells is inhibited much later than division of normal cells, or is completely ininhibited due to geometric conditions. Fusion of the cell membrane in the intra-cellular and intercellular processes is a reverse process in relation to the cell division.     

The Effect of Age and Gender on Al, B, Ba, Ca, Cu, Fe, K, Li, Mg, Mn, Na, P, S, Sr, V, and Zn Contents in Rib Bone of Healthy Humans

The effect of age and gender on major, minor, and trace element contents in the intact rib bone of 80 relatively healthy 15–55-year-old women and men was investigated. Contents or upper limit of contents of 16 chemical elements in the rib bone were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). Mean values (M?±?SΕΜ) for the mass fraction of Ba, Ca, Cu, Fe, K, Li, Mg, Na, P, S, Sr, and Zn (milligram per kilogram of dry bone) were as follows: 2.54?±?0.16, 171,400?±?4,050, 1.35?±?0.22, 140?±?11, 1,874?±?71, 0.049?±?0.011, 2,139?±?38, 5,378?±?88, 75,140?±?1,660, 1,881?±?51, 291?±?20, and 92.8?±?1.5, respectively. The upper limits of contents of Al, B, Mn, and V were <7.20, <0.65, <0.36, and <0.03, respectively. Statistically significant tendency for the Ca, Mg, and P content to decrease with age was found in the human rib bone, regardless of gender. The mass fraction of Fe in the male rib bone increases with age. It was shown that higher Ca, Mg, Na, P, and Sr mass fractions as well as lower Fe content were typical of female ribs as compared to those in male ribs.     

Distribution of N,P, K,Ca, Mg,S, Zn,Fe, Mn and Cu in groundnut

Summary Concentration of N, P, K, Ca, Mg and S in summer groundnut crop was higher than in kharif while Zn, Fe, Mn and Cu contents were higher in summer crop. Kernel's N, P and Zn; Leaflet's Ca and Mn; Stem's K and Fe; Root's S and Cu and Petiole's Mg contents were highest. Shell's N, P, K, Mg, S, Zn and Cu; Kernel's Ca, Fe and Mn contents were the least. N, P, K, S, Zn and Cu concentrations decreased linearly as the crop grew. Ca, Mg, Fe and Mn concentrations did not display any distinct pattern. Ca concentration was positively correlated with pod yield in both the seasons.     

The effect of malathion,diazinon, and various concentrations of zinc,copper, nickel,lead, iron,and mercury on fish

Acute and chronic toxicity tests for malathion, diazinon, copper (Cu), mercury (Hg), lead (Pb), zinc (Zn), nickel (Ni), and iron (Fe) were conducted. Mortalities ofBarilius vagra andCyprinus carpio (common carp) were variable but LC50-96 hr were similar for pesticides. AdultB. vagra seem to be more sensitive to malathion than juvenile carp. Both juvenile carp and adultB. vagra were extremely sensitive to diazinon. Long-term exposure to pesticides modified morphology and behavior. The LC50-96 values for Cu, Hg, and Pb were 0.3, 0.16, and 0.44, respectively, for smaller fish and 1.0, 0.77, and 1.33, respectively, for larger fish. Replicate LC50 values for Zn, Ni, and Fe were somewhat variable, and for these metals, the size of the fish seemed to affect response because LC50 values increased as fish size increased. Cooper, Pb, Zn, and Fe residues following exposure to sublethal concentrations of these metals for 15 d were significantly greater in whole juvenile common carp than in controls.     

Synthesis,tautomerism, and antimicrobial,anti-HCV,anti-SSPE,antioxidant, and antitumor activities of arylazobenzosuberones

2-Dimethylaminomethylene-1-benzosuberone 1 was coupled with diazotized aniline derivatives to afford a series of the hitherto unreported 2-arylazo-1-benzosuberones 3a–i. The tautomeric structure and the effect of substituents on the tautomeric form (s) of the products 3a–i were discussed. Similar coupling of the enaminone 1 with diazonium salts of heterocyclic amines gave the respective fused azolotriazino-benzosuberones. Some of the newly synthesized compounds showed potent antimicrobial, anti-HCV, antioxidant, antitumor (as topoisomerase I inhibitors), and antimicrobial activities.