Hydrate dissociation conditions for gas mixtures containing carbon dioxide, hydrogen, hydrogen sulfide, nitrogen, and hydrocarbons using SAFT

A new method, a molecular thermodynamic model based on statistical mechanics, is employed to predict the hydrate dissociation conditions for binary gas mixtures with carbon dioxide, hydrogen, hydrogen sulfide, nitrogen, and hydrocarbons in the presence of aqueous solutions. The statistical associating fluid theory (SAFT) equation of state is employed to characterize the vapor and liquid phases and the statistical model of van der Waals and Platteeuw for the hydrate phase. The predictions of the proposed model were found to be in satisfactory to excellent agreement with the experimental data.

Development of durable carbon black/titanium dioxide supported macrocycle catalysts for oxygen reduction reaction

Carbon black and titanium dioxide supported iron tetraphenylporphyrin (FeTPP/TiO2/C) catalysts for oxygen reduction reaction (ORR) were prepared by sol-gel and precipitation methods followed by a heat-treatment at temperatures of 400-1000 degrees C. The FeTPP/C and TiO2/C were also studied for comparison. The FeTPP/TiO2/C pyrolyzed at 700 degrees C exhibits significantly improved stability while maintaining high activity towards ORR in comparison with the FeTPP/C counterpart. The electrochemical study combined with XRD, XPS, and SEM/EDX analyses revealed that the appropriate dispersion of TiO2 on the surface of FeTPP/TiO2/C catalysts, which depending on heat-treatment temperature, plays a crucial role in determining the activity and stability of catalysts.

Transporting nutrients from sediments: nitrogen and carbon as indicators to measure scavenging ability of a detritivorous fish, Liza haematocheila

The redlip mullet, Liza haematocheila, is a common species in polyculture as a scavenger in China. Feeding on detritus, redlip mullet transports nutrients from sediments up into the water column and converts them into forms that can be utilized by phytoplankton and affects the relative abundance of detritus and dissolved inorganic nutrients to phytoplankton, zooplankton and other fishes. We used nitrogen and carbon as the indicators in this study to measure the scavenging ability, which means intake of nitrogen or carbon by redlip mullet, and the loss of nutrients. Temperature and body weight significantly affected growth nitrogen, faecal nitrogen and faecal carbon. At a certain temperature, the proportion of growth nitrogen or growth carbon increased while the proportion of excretion nitrogen or respiration carbon decreased with increasing body weight.

Effects of nitrogen forms on the production of cyanobacterial toxin microcystin-LR by an isolated Microcystis aeruginosa

A cyanobacterial strain, which produced high content of microcystin-LR (MC-LR) but no rnicrocystin-RR (MC-RR), was isolated from the hypertrophic Dianchi Lake in China and identified as Microcystis aeruginosa DC-1. Effects of nitrogen containing chemicals and trace elements on the growth and the production of MC-LR by this strain were Studied. In the presence of bicine, compared with urea and ammonium, nitrate greatly promoted the growth and the production of MC-LR. However, leucine and arginine, which were the constitutional components in the molecular structure of MC-LR or RR, inhibited the production of MC-LR. Iron and silicon up to 10mg/L had little effects on the growth of M. aeruginosa DC-1, but the production of MC-LR was apparently enhanced. Under all conditions studied here, only MC-LR but no RR was detected within the cells of M. aeruginosa DC-1. Thus, chemical forms of nitrogen, rather than the usually concerned the total nitrogen, Lind trace elements played important roles in the production of MC toxins during cyanobacterial blooms.

Alternate assemblies of polyelectrolyte functionalized carbon nanotubes and platinum nanoparticles as tunable electrocatalysts for dioxygen reduction

A novel method based on electrostatic layer-by-layer self-assembly (LBL) technique for alternate assemblies of polyelectrolyte functionalized multi-walled carbon nanotubes (MWNTs) and platinum nanoparticles (PtNPs) is proposed. The shortened MWNTs can be functionalized with positively charged poly(diallyldimethylammonium chloride) (PDDA) based on electrostatic interaction. Through electrostatic layer-by-layer assembly, the positively charged PDDA functionalized MWNTs (PDWNTs) and negatively charged citrate-stabilized PtNPs were alternately assembled on a 3-mercaptopropanesulfonic sodium (NIPS) modified gold electrode and also on other negatively charged surface, e.g. quartz slide and indium-tin-oxide (ITO) plate, directly forming the three-dimensional (3D) nanostructured materials. This is a very general and powerful technique for the assembling three-dimensional nanostructured materials containing carbon nanotubes (CNTs) and nanoparticles. Thus prepared multilayer films were characterized by ultraviolet-visiblenear-infrared spectroscopy (UV-vis-NIR), scanning electron microscopy (SEM) and cyclic voltammetry (CV). Regular growth of the mutilayer films is monitored by UV-vis-NIR.

Effect of La3+ on structure and electrochemical reaction of microperoxidase-11 in imitated physiological solution

In this paper, the interaction mechanism between La3+ and microperoxidase-11 (MP-11) in the imitated physiological solution was investigated with the electrochemical and spectroscopic methods. It was found that when the molar ratio of La3+, and MP-11 is low, such as 2, La3+ can coordinate with oxygen in the propionic acid group of the heme group in the MP-11 molecule, forming the La-MP-11 complexes and leading to the increase in the non-planarity of the porphyrin cycle in the heme group and then the increase in the extent of exposure of the electrochemically active center, Fe(I I I) in the porphyrin cycle of the heme group. The increase in the extent of exposure of the electrochemically active center, Fe(III) in the porphyrin cycle of the heme group would increase the reversibility of the electrochemical reaction of the La-MP-11 complexes and its electrocatalytic activity for the reduction of H2O2. The results of the chromatographic analysis demonstrated that the average molar ratio of La3+ and MP-11 in the La-MP-11 complexes is 1.62.When the molar ratio of La3+ and MP-11 is high, such as 3, La3+ would shear some amino acid residues of the peptide of MP-11. Therefore, many La3+ ions can bind to the oxygen- and/or nitrogen-containing groups in the sheared amino acid residues except coordinating with the sheared and non-sheared MP-11 molecules.

Preparation and layer-by-layer self-assembly of positively charged multiwall carbon nanotubes

The report described a method of more stably dispersing oxidized carbon nanotubes (CNTs) by forming complex with polycation and the layer-by-layer self-assembly behavior of the complex with polyanion was studied. The properties of the self-assembled multilayer film containing carbon nanotubes were studied. Cyclic voltammetry, UV-vis-NIR spectroscopy, electrochemical impedance spectroscopy and scanning electron microscopy were used for characterization of film assembly. UV-vis-NIR spectroscopy and cyclic voltammetry study indicated the uniform growth of the film. Electrochemical impedance spectroscopy results showed that incorporating of carbon nanotubes in the polyelectrolyte multilayers; decreased in the electron-transfer resistance R, indicating more favorable electrochemical reaction interface. The electrocatalytic property of the multilayer modified electrode to NADH was investigated mainly with different numbers of the bilayers; and the results showed that along with the increase of the assembled bilayers the overpotential of NADH oxidation decreased. The detection lit-nit Could reach 6 mu M at a detection potential of 0.4 V.

改变土壤碳输入对我国北方温带草原土壤碳、氮库和碳、氮循环的影响

土壤是陆地生态系统最重要的碳库和氮库，在陆地生态系统碳氮循环过程中起着举足轻重的作用。植物光合作用产物向地下的分配(根系分泌、细胞凋亡和根系分解)和地上凋落物分解是土壤碳两个最主要的来源，关于这两种碳输入途径和量如何影响陆地生态系统土壤碳氮库和循环的有限理解，限制了我们预测陆地生态系统碳循环对于全球气候变化的响应和反馈。本实验以我国北方广泛分布的温带典型草原生态系统为研究对象，通过添加和去除地面凋落物以及割草改变植物对土壤的碳输入途径和量，观察温带草原土壤有机碳库和氮库各个组分(微生物生物量碳氮、活性碳、可溶性碳、轻重组碳、总有机碳、总有机氮)及碳氮循环(微生物呼吸、土壤呼吸、生态系统气体交换、净氮矿化)的变化，来区分和量化凋落物分解和根系分泌、分解这两种碳输入方式对草原土壤碳库和循环的相对贡献和影响，有助于揭示在全球变化背景下温带典型草原生态系统碳库和碳循环的响应机制，并为预测其未来变化动态以及对全球气候变化的反馈提供参数估计和模型校正和验证。 我们对各处理样方土壤温度、土壤水分以及土壤呼吸进行了一个生长季的测定，结果表明，添加和去除凋落物都使得土壤呼吸与对照相比都有所增加，但是都没有达到显著水平;而无论地上凋落物的量添加、去除还是不变，植物光合作用对土壤呼吸的影响则比较显著，去除植物显著地降低了土壤呼吸。这说明处理一年后，植物对土壤呼吸起主导作用，而凋落物处理对土壤呼吸的影响还需要更长时间的观察。此外，生物量的结果也表明了地上凋落物的改变会影响到植物生长，从而影响到植物对土壤的碳输入，但是都没有达到显著水平，仍然需要我们进行更长时间的处理和观察。 通过在生长季前期、中期、后期进行了三次氮矿化的测定，以及在生长季后期进行了一次微生物生物量测定，我们得出以下结论：添加凋落物加快了净氮矿化速率，但是没有达到显著影响水平;同样，去除凋落物降低了净氮矿化速率，也没有达到显著水平。此外，添加凋落物处理微生物生物量碳、氮都有所增加，与对照相比没有显著差异，但是显著高于另外几个处理。 通过本研究，我们对于根系分泌和地上凋落物分解这两种碳氮输入途径对我国温带草原碳氮循环的影响有了初步的了解。与森林生态系统相比，由于草原生态系统土壤碳氮含量低，土壤碳库和转化对碳输入途径和量的变化更为敏感，在处理第一年，土壤微生物量和土壤呼吸都发生了显著的变化。然而，由于改变土壤碳库是长时间日积月累的结果，草原生态系统某些指标对碳输入途径和量的变化的响应还需要较长时间才能显示出来，例如添加和去除凋落物虽然使得土壤呼吸值有所增加，但是还都没有达到显著的水平;另外碳输入途径和量的变化对草原生态系统氮矿化还没有产生显著的影响。这些都需要更长时间的处理和观测来验证。

氮沉降对长白山森林表层土壤碳氮周转过程的影响

在大气CO2升高和氮(N)沉降增加等全球变化背景下，N元素对生态系统碳(C)、N元素周转过程的影响开始引起越来越多的关注。作为陆地生态系统C库重要组成部分的森林土壤，也逐渐成为研究的重点之一。 本文选择长白山地区典型森林生态系统表层土壤和凋落物，利用人工施N，在实验室控制条件下，模拟N沉降对森林土壤表层C、N元素周转过程影响。旨在从微观上揭示N沉降对凋落物和土壤表层腐殖质分解过程中C、N元素周转过程和土壤C库的影响，主要结论如下: (1) 外源N输入加快了凋落物早期的分解。阔叶树种（岳桦 Betula ermanii、蒙古栎 Quercus mongolica、椴树 Tilia amurensis）的凋落物的分解速度明显快于针叶树种（红松 Pinus koraiensis、鱼鳞云杉 Picea jezoensis）。凋落物的木质素含量是控制其分解速度的主导因子。 (2) N添加对凋落物可溶性有机C（DOC）淋失没有显著影响。DOC淋失主要受凋落物基本性质的控制。阔叶树种的凋落物DOC淋失量明显高于针叶树种。 (3) 不同植被下的土壤性质和C、N周转过程有较大的差异，岳桦林下土壤的微生物生物量和N矿化速率都显著高于暗针叶林，而土壤的C矿化量却低于暗针叶林。岳桦林土壤的DOC和DON淋失量也高于暗针叶林。 (4) N添加显著降低了森林表层土壤的呼吸速率。外加氮对土壤DOC淋失的影响存在一个平衡点，过高的N输入可能加快土壤中DOC的分解速度，降低DOC的淋失量。 研究结果表明，尽管长白山森林生态系统还没有达到“N饱和”，但不断升高的N沉降水平将对长白山典型森林生态系统土壤的C、N元素的周转过程产生较大的影响。但要全面评估N沉降对长白山地区森林土壤C库的影响，还需在野外进行长期定位研究。

氮杂环化合物的绿色合成研究

氮杂环化合物大多数都是具有生理活性的物质，例如喹喔啉化合物与苯二氮卓类化合物，因此研究氮杂环化合物骨架的构建方法具有一定意义。绿色化学的迅速发展迫切要求化学家发展清洁、经济和环境较友好条件下的有机合成方法。其中，水相反应与绿色固体酸催化剂的使用都是实现绿色有机合成的重要途径，它们非常具有潜力，近些年受到了广泛关注。本论文的主要工作是围绕水相及固体酸催化条件下两类具有生物活性的含氮杂环小分子的合成方法而开展的，具体包括以下内容： 1. 研究和探索出了两类绿色固体酸催化剂蒙脱土（Mont. K-10）和杂多酸(H4SiW12O40), 在水相条件下成功合成出喹喔啉化合物的有效方法。两个催化体系都以无毒无公害的水作反应溶剂，实验条件温和，操作安全简便，反应速度快，底物普适性强，产率高，且产物易分离收集。两类固体酸催化剂，对设备腐蚀性小，可回收循环使用，对环境无公害; 蒙脱土催化大部分底物能得到当量产率的产物，硅钨酸催化催化剂负载量小。 2. 实现了无溶剂条件下，以杂多酸（H3PW12O40）作催化剂，高效合成1,5-苯二氮卓衍生物的合成方法。该催化体系具有以下一些优势：实验条件温和，反应速度较快，底物普适性良好，产物易分离收集，反应过程中没有加入其它有机溶剂，绿色环保。 ‘Green Chemistry’ is currently a major issue of modern chemistry. It is widely acknowledged that there is a growing need for more environmentally acceptable processes in the chemical industry. New green catalysts and green reaction media are the important and efficient strategies in green chemistry. New green catalysts include solid acid catalysts, solid base catalysts, metal catalysts not only possess higher activity and selectivity, but also are easily separated from reaction system. Green reaction media include water, supercritical fluids and ionic liquids can not only substitute traditional toxic and harmed organic solvents, but also improve reaction activity and selectivity. Meanwhile water is a promising green reaction medium for use in modern chemistry because it has a number of advantages such as the cheapest solvent available on earth, being non-hazardous and non-toxic to the environment. Solid acids had also attracted much attention for realizing green chemistry due to their unique acidity, high activity and efficiency as organic catalysts. Nitrogen-containing heterocyclic compounds of different ring sizes such as quinoxaline and benzodiazepine are the important pharmacologically active compounds. Due to the wide biological significance of these compounds, the synthesis of these types of compounds have received a great deal of attention. Despite the large availability of methods to construct nitrogen-containing heterocyclic compounds, there is still a strong need to further explore green methods to efficiently and safely synthesize these compounds. Thus, we aim at developing efficient and green methodology for the synthesis of quinoxaline and benzodiazepine carried out under water condition with solid acid catalysts. The contents of this dissertation are listed as the following: 1. We have developed two catalytic systems for the synthesis quinoxaline via the condensation of an aryl 1,2-diamine with a 1,2-diketone compound in the presence of Mont. K-10 or H4SiW12O40 as a catalyst in water solvent. Both of these two methods can be applied to wide range of substrates, tolerating aryl 1,2-diamine/1,2-diketone with the electron donating/drawing substituent. Operational simplicity, the ambient conditions, use of an economically convenient catalyst, use of water as a desirable solvent, high yields and short reaction times are the key features of these two protocols. 2. We developed a convenient and efficient protocol for the synthesis of a variety of 1,5-benzodiazepines in high yields via condensation of aryl o-phenylenediamine derivatives with a variety of ketones using H3PW12O40 as a green recyclable and heterogeneous catalyst under solvent-free condition. The simple experiment procedure combined with ease of recovery and reuse of this catalyst make this procedure quite simple, more convenient and environmentally benign.

不同放牧强度下高山草甸生态系统碳氮分布格局和循环过程研究

本研究针对川西北高山草甸缺乏科学管理，过度放牧导致草场退化，并由此引发的一系列生态环境问题，选取红原县瓦切乡1996 年草地承包后形成的四个放牧强度草场，即不放牧、轻度（1.2 头牦牛hm-1）、中度（2.0 头牦牛hm-1）和重度放牧（2.9 头牦牛hm-1），作为研究对象，研究了不同放牧强度对草地植物-土壤系统中碳、氮这两个最基本物质的分布格局和循环过程的影响，并探讨了放牧干扰下高山草甸生态系统的管理。 1．放牧对草地植物群落物种组成，尤其是优势种，产生了明显的影响。不放牧、轻度、中度和重度放牧草地群落物种数分别为22，23，26，20 种，群落盖度分别是不放牧96.2%＞中度93.6%＞轻度89.7%＞重度73.6%。随放牧强度的增加， 原植物群落中的优势种垂穗鹅冠草（ Roegneria nutans ）、发草（Deschampsia caespitosa）和垂穗披碱草（Elymus nutans）等禾草逐渐被莎草科的川嵩草（Kobresia setchwanensis）和高山嵩草（Kobresia pygmaea）所取代成为优势种。同时，随放牧强度的增加，高原毛茛（Ranunculus brotherusii）、狼毒（Stellera chamaejasme）、鹅绒委陵菜（Potentilla anserina）和车前（Plantagodepressa）等杂类草的数量也随之增加。 2．生长季6～9 月份，草地植物地上和地下生物量（0～30cm）都是从6 月份开始增长，8 月份达到最高值，9 月份开始下降。每个月份，通常地上生物量以不放牧为最高，重度放牧总是显著小于不放牧；地下生物量随放牧强度的增加表现为增加的趋势，通常重度和中度放牧显著高于不放牧和轻度放牧草地。不放牧、轻度、中度和重度放牧草地6～9 月份4 个月的植物总生物量平均值分别是1543、1622、2295 和2449 g m-2，但随放牧强度的增加越来越来多的生物量被分配到了地下部分，地下生物量占总生物量比例的大小顺序分别是重度88%＞中度82%＞轻度76%＞不放牧69%。生物量这种变化主要是由于放牧使得群落优势种发生改变而引起的，其分配比例的变化体现了草地植物对放牧干扰的适应策略。 3．植物碳氮贮量的季节变化类似与生物量的变化。每个月份，不同放牧强度间植物地上碳氮的贮量有所不同，一般重度放牧会显著减少植物地上碳氮贮量。植物根系(0～30cm)碳氮贮量随放牧强度的增加表现为增加的趋势，通常重度和中度放牧显著高于不放牧和轻度放牧草地。不放牧、轻度、中度和重度放牧草地6～9 月份4 个月的植物总碳平均值分别是547、586、847 和909 g m-2，根系碳贮量占植物总碳的比例大小顺序分别是重度88%＞中度82%＞轻度76%＞不放牧69%；放牧、轻度、中度和重度放牧草地6～9 月份4 个月的植物总氮平均值分别是17、17、23 和26 g m-2，根系氮贮量占植物总氮的比例大小顺序分别是重度79%＞轻度71%＞中度70%＞不放牧65%。 4. 土壤有机碳贮量（0～30cm）的季节变化表现为7 月份略有下降，8 月开始增加，9 月份达到的最大值。土壤氮贮量的季节变化表现为随季节的推移逐渐增加的趋势。增加的放牧强度不同程度的增加土壤有机碳氮的贮量。不放牧、轻度、中度和重度放牧6～9 月份4 个月的土壤有机碳贮量的平均值分别是9.72、10.36、10.62 和11.74 kg m-2，土壤氮贮量分别为1.45、1.56、1.66 和1.83 kg m-2。土壤中有机碳（氮）的贮量都占到了植物-土壤系统有机碳（氮）的90%以上，但不同放牧强度之间的差异不明显。 5. 土壤氮的总硝化和反硝化，温室气体N2O 和CO2 的释放率的季节变化表现为从6 月份开始增加，7 月份达到最大值，8 月份开始下降，9 月份降为最小值。增加的放牧强度趋向于增加土壤氮的总硝化和反硝化作用，温室气体N2O和CO2 的释放率，通常情况下，中度放牧和重度放牧显著地加强了这些过程。 6．垂穗鹅冠草（Roegneria nutans）和川嵩草（Kobresia setchwanensis）凋落物在不同放牧强度下经过1 年的分解，两种凋落物的失重率及其碳氮的损失率3都随放牧增加表现为增加的趋势。在同一放牧强度下，川嵩草凋落物的失重率和碳氮的损失率都高于垂穗鹅冠草凋落物。 7. 尽管重度放牧显著增加了土壤碳氮的贮量，但同时也显著降低了植被群落盖度，降低了植物地上生物量，因此，久而久之会减少植物向土壤中的碳氮归还率；与不放牧和轻度放牧相比，重度放牧又显著增加了土壤CO2 和NO2 的排放量，这是草地生态系统碳氮损失的重要途径。由此可见，对于这些地处青藏高原的非常脆弱的高山草甸生态系统，长期重度放牧不仅导致植物生产力降低，而且将导致草地生态系统退化，甚至造成土壤中碳氮含量减少。 Long-term overgrazing has resulted in considerable deterioration in alpine meadowof the northwest Sichan Province. In order to explore management strategies for thesustainability of these alpine meadows, we selected four grasslands with differentgrazing intensity (no grazing-NG: 0, light grazing-LG: 1.2, moderate grazing-MG: 2.0,and heavy grazing-HG: 2.9 yaks ha-1) to evaluate carbon, nitrogen pools and cyclingprocesses within the plant-soil system in Waqie Village, Hongyuan County, Sichuan Province. 1. Grazing obviously changed the plant species composition, especially ondominant plant species. Total number of species is 22, 23, 26, and 20 for NG, LG, MGand HG, respectively. Vegetation coverage under different grazing intensity ranked inthe order of 96.2% for HG＞93.6% for MG＞89.7% for LG＞73.6% for NG. Thedominator of HG community shifted from grasses-Roegneria nutans andDeschampsia caespitosa dominated in the NG and LG sites into sedges-Kobresiapygmaea and K. setchwanensis. At the same time, with the increase of grazingintensity, the numbers of forbs, such as Ranunculus brotherusii, Stellera chamaejasme,Potentilla anserine and Plantago depressa, increased with grazing intensity. 2. Over the growing season, aboveground and belowground biomass showed a 5single peak pattern with the highest biomass in August. For each month, abovegroundbiomass usually was the highest in the NG site and lowest in the HG site.Belowground biomass showed a trend of increase as grazing intensity increased and itwas significantly higher in the HG and MG site than in the NG and LG sites. Totalplant biomass averaged over the growing season is 1543, 1622, 2295 and 2449 g m-2for NG, LG, MG and HG, respectively. The proportion of biomass to total plantbiomass for NG, LG, MG and HG is 88%, 82%, 76% and 69%, respectively. Higherallocation ratio for is an adaptive response of plant to grazing. 3. Carbon and nitrogen storage in plant components followed the similar seasonalpatterns as their biomass under different grazing intensities. Generally, heavy grazingsignificantly decreases aboveground biomass carbon and nitrogen compared to nograzing. Carbon and nitrogen storage in root tended to increase as grazing increasedand they are significantly higher in the HG and MG sites compared to the LG and NGsite. Total Carbon storage in plant system averaged over the growing season is 547,586, 847 and 909 g m-2 for NG, LG, MG and HG, respectively, while 17, 17, 23 and 26g m-2 for nitrogen. The proportion of carbon storage in root to total plant carbon forNG, LG, MG and HG is 88%, 82%, 76%, 69%, respectively, while 65%, 71%, 70%and 79% for nitrogen. 4. Carbon storage in soil (0-30cm) decreased slightly in July, then increased inAugust and peaked in September. Nitrogen storage in soil tended to increase withseason and grazing intensity. Total Carbon storage in soil averaged over the growingseason is 9.72, 10.36, 10.62 and11.74 kg m-2 for NG, LG, MG and HG, respectively,while 1.45, 1.56, 1.66 and 1.83 for nitrogen. The proportion of carbon (nitrogen)storage in soil to plant-soil system carbon (nitrogen) storage for NG, LG, MG and HGis more than 90%, which is not markedly different among different grazing intensities. 5. Gross nitrification, denitrification, CO2 and N2O flux rates in soil increasedfrom June to July and then declined until September, all of which tended to increasewith the increase of grazing intensity. Generally, heavy and moderate grazing intensitysignificantly enhanced these process compared to no and light grazing intensity. 6. After decomposing in situ for a year, relative weight, carbon and nitrogen loss in the litter of Roegneria nutans and Kobresia setchwanensis tended to increase asgrazing intensity increased. Under the same grazing intensity, relative weight, carbonand nitrogen loss in the litter of Kobresia setchwanensis were higher than these in thelitter of Roegneria nutans. 7. Although heavy grazing intensity resulted in higher levels of carbon andnitrogen in plant and soil, it decreased vegetation coverage and aboveground biomass,which are undesirable for livestock production and sustainable grassland development.What is more, heavy grazing could also introduce potential carbon and nitrogen lossvia increasing CO2 and N2O emission into the atmosphere. Grazing at moderateintensity resulted in a plant community dominated by forage grasses with highaboveground biomass productivity and N content. The alpine meadow ecosystems inTibetan Plateau are very fragile and evolve under increasing grazing intensity by largeherbivores; therefore, deterioration of the plant-soil system, and possible declines insoil C and N, are potential without proper management in the future.

瑞香狼毒（Stellera chamaejasme L.）对高寒草甸系统生长和非生长季节碳氮循环的影响及其花粉化感效应

瑞香狼毒（Stellera chamaejasme L.）是瑞香科（Thymelaeaceae）狼毒属的一种多年生野草，有毒。据调查，从20 世纪60 年代开始至今，狼毒在青藏高原东缘的高寒草甸上不断蔓延、密度不断变大，在一些地段甚至成为优势物种。有关狼毒在高寒草甸蔓延的生态系统效应的研究尚未见报道。本文从系统碳、氮循环的角度，分别研究狼毒在生长和非生长季节对高寒草甸生态系统的影响。同时，从花粉化感的角度，深入研究狼毒对当地同花期物种有性繁殖的影响。系统地研究高寒草甸生态系统物质循环过程，特别是非生长季节微生物和土壤碳氮库的动态变化，有助于揭示狼毒在系统物质循环方面的“物种效应”以及这种效应的季节变化，为丰富有关高海拔生态系统，特别是其非生长季的物质循环的科学理论做出贡献。同时，碳氮循环和花粉化感的研究还有助于深刻地理解狼毒作为一种入侵性很强的杂草的特殊的蔓延机制，从而为狼毒的有效防治、高寒草甸的科学管理提供依据。 针对狼毒在青藏高原高寒草甸上蔓延的生态系统碳氮循环方面的影响，开展以下2 方面的研究：（1）在生长季，研究松潘县尕米寺附近（北纬32°53'，东经103°40'，海拔3190 m）的两种地形（平地和阳坡）条件下狼毒对土壤碳氮循环影响及可能的原因。狼毒和其它几个主要物种（圆穗蓼（Polygonummacrophyllum D. Don var. Macrophyllum），草地早熟禾（Poa pretensis L.），四川嵩草（Kobresia setchwanensis Hand.-Maizz.），鹅绒委陵菜（Potentilla anserina L.var. anserine）和鳞叶龙胆（Gentiana squarrosa Ledeb.）的地上凋落物产量以及地上凋落物和根的化学组成被测量。在有-无狼毒斑块下，各种土壤的库（比如，铵态氮、硝态氮、无机磷和微生物生物量）和周转率（包括净矿化、净硝化、总硝化、反硝化和微生物呼吸速率）被测量和比较。（2）在非生长季节，尤其是春季冻融交替期，选取了两个研究地点——尕米寺和卡卡沟（北纬32°59'，东经103°41'，海拔3400 m），分别测定有狼毒和无狼毒斑块下土壤微生物生物量碳和氮、可溶性有机碳和氮以及铵态氮和硝态氮的动态变化。同时，分别在上述两个地点有-无狼毒的样地上，研究6 个主要物种（狼毒、圆穗蓼、草地早熟禾、四川嵩草、鹅绒委陵菜和鳞叶龙胆）从秋季开始、为期1 年的凋落物分解过程。 针对狼毒花粉化感对同花期其它物种可能的花粉化感作用开展以下工作：在实验室中，用一系列浓度的狼毒花粉水浸提液对与它同花期的其它物种以及自身花粉进行测试，测定花粉萌发率；在野外自然条件下的其它物种的柱头上施用上述浓度的狼毒花粉水浸提液，观测种子结实率，同时，观察狼毒花粉的种间花粉散布数量。 生长季节的研究结果表明，狼毒地上凋落物氮含量比其它几个主要物种更高，而木质素-总氮比更低。狼毒显著地增加其斑块下表层土壤中有机质的含量，而有-无狼毒的亚表层土壤在有机碳和总磷方面没有显著差异。狼毒表土中硝态氮含量在平地和阳坡比无狼毒土壤分别高113%和90%。狼毒表土中微生物生物量碳和氮量显著高于无狼毒表土。无论是平地还是阳坡，狼毒土壤的总硝化和微生物呼吸速率显著高于无狼毒土壤；而它们的反硝化速率只在平地有显著的差异。狼毒与其它物种间地上凋落物的产量和质量的差异可能是导致有-无狼毒土壤碳氮循环差异的原因。我们假设，狼毒可能通过增加贫氮生态系统土壤中的有效氮含量提高其入侵能力。 非生长季的研究结果表明，在青藏高原东缘的高寒草甸上，土壤微生物生3物量在11 月的秋-冬过渡期达到第一个峰值；在春季的冻融交替期，微生物生物量达到第二个峰值后又迅速降低。无机氮以及可溶性有机碳氮与微生物生物量有相似的变化过程。微生物碳氮比呈现显著的季节性变化。隆冬季节的微生物生物量碳氮比显著高于生长旺季的微生物碳氮比。这种变化可能暗示冬、夏季微生物的群落组成和对资源的利用有所不同。有-无狼毒斑块下土壤微生物和土壤碳、氮库一般只在秋-冬过渡期有显著差异，有狼毒土壤微生物生物量和土壤碳、氮库显著高于无狼毒土壤；而在之后的冬季和春季没有显著差异。所有6 个物种凋落物在非生长季分解率为24%-50%，均高于生长季的10%到30%。其中在秋-冬过渡期，凋落物开始埋藏的两周时间内，分解最快，达10%-20%。不同物种凋落物全年的分解率和分解过程有显著差异。圆穗蓼在全年的分解都较缓慢（非生长季26%，生长季15%），草地早熟禾和四川嵩草等全年的分解速率比较均匀（非生长季和生长季均为30%，非生长季略高），而狼毒在非生长季分解较快（约50%），而在接下来的生长季分解变得缓慢（约12%）。所有物种的凋落物氮含量在非生长季下降，而在随后的生长季上升。 实验室的花粉萌发试验证明，狼毒花粉对自身花粉萌发没有自毒作用，而其它受试的所有物种（圆穗蓼，秦艽（Gentiana macrophylla Pall. var. fetissowii），湿生扁蕾（Gentianopsis paludosa (Hook. f.) Ma var. paludosa），鳞叶龙胆，椭圆叶花锚（Halenia elliptica D. Don var. elliptica），蓝钟花（Cyananthus hookeri C. B.Cl. var. grandiflorus Marq.），小米草（Euphrasia pectinata Ten.），川西翠雀花（Delphinium tongolense Franch.），高原毛茛（Ranunculus tanguticus (Maxim.)Ovcz. var. tanguticus）和鹅绒委陵菜）的花粉萌发率随着狼毒花粉浸提液浓度的增加呈显著的非线性降低。大约3 个狼毒花粉的浸提液就可以抑制受试的多数物种的50%的花粉萌发。在鳞叶龙胆和小米草柱头上狼毒花粉的数量分别为5.76 个和3.35 个。狼毒花粉散布数量的差异最可能的原因在于是否有共同的传粉昆虫。花的形状（辐射对称VS 左右对称）、植株或花的密度以及花期重叠性可以部分解释这种差异。在野外试验中，我们发现6 个物种（秦艽、湿生扁蕾、鳞叶龙胆、椭圆叶花锚、蓝钟花和小米草）的种子结实率随狼毒花粉浸提液浓度的增加呈显著的非线性降低。鳞叶龙胆和小米草柱头上狼毒花粉的数量（分别是5.76 个和3.35 个）分别达到了抑制它们63%和55%种子结实率的水平。因此，狼毒对鳞叶龙胆和小米草可能存在明显的花粉化感抑制作用。狼毒周围的物种可能通过花期在季节或昼夜上的分异避免受到狼毒花粉化感的影响或者通过无性繁殖来维持种群繁衍，因此狼毒通过花粉化感作用对其周围物种繁殖的影响程度还需要进一步地研究。如果狼毒的花粉化感抑制作用确实存在，那么它可能成为一种自然选择压力，进而影响物种的进化。 Stellera chamaejasme L., a perennial toxic weed, has emerged and quicklydominated and spread in the high-frigid meadow on the eastern Tibetan Plateau ofChina since the 1960s. In the present study, effects of S. chamaejasme on carbon andnitrogen cycles on the high-frigid meadow on the eastern Qinghai-Tibetan Plateau ingrowing and non-growing season, and its pollen allelopathic effects on the sympatricspecies were determined. The present study that focused on carbon and nitrogencycles, especially on microbial biomass and pools of carbon and nitrogen innon-growing season, could profoundly illuminate plant-species effects on carbon andnutrient cycles and its seasonal pattern and help to understand spread mechanism ofS. chamaejasme as an aggressive weed. The present study also contributed to furtherunderstand carbon and nutrient cycles on alpine regions in non-growing season andprovide a basis on weed control of S. chamaejasme and scientific management in thehigh-frigid ecosystem. Effects of S. chamaejasme on carbon and nitrogen cycles on the high-frigidmeadow on the eastern Qinghai-Tibetan Plateau were determined. The study couldbe divided into two parts. (1) In the growing season, we quantified the effects of S.chamaejasme on carbon and nitrogen cycles in two types of topographic habitats, theflat valley and the south-facing slope, where S. chamaejasme was favored to spreadlitter and root were measured to explain the likely effects of S. chamaejasme on soilcarbon and nutrient cycles. The sizes of various soil pools, e.g. nitrite, ammonium,inorganic phosphorus and microbial biomass, and turnover rates including netmineralization, gross nitrification, denitrification and microbial respiration weredetermined. (2) In the non-growing season study, microbial biomass carbon andnitrogen, soluble organic carbon and nitrogen, ammonium and nitrate weredetermined through the non-growing season, especially in the processes offreeze-thaw of spring in two high-frigid sites, i.e. Kaka valley and Gami temple, onthe eastern Qinghai-Tibetan Plateau. Meanwhile, litter decomposition of six commonspecies, including Stellera chamaejasme L., Polygonum macrophyllum D. Don var.Macrophyllum, Poa pretensis L., Kobresia setchwanensis L., Potentilla anserina L.var. anserine and Gentiana squarrosa Ledeb., were also examined under theabove-mentioned experimental design through one whole-year, which began in theautumn in 2006. In the study of pollen allelopathy, several work, including in vitro study oneffects of extract of pollen from S. chamaejasme on sympatric species and pollenfrom itself, field experiments on effects of pollen extract with the same regime ofconcentrations on seed set and field observation on heterospecific pollen transfer ofS. chamaejasme to six of those sympatric species has been done. The results in the growing season showed that aboveground litter of S.chamaejasme had higher tissue nitrogen and lower lignin: nitrogen ratio than thoseco-occurring species. S. chamaejasme significantly increased topsoil organic matter,whereas no significant differences were found for organic C and total P in subsoilbetween under-Stellera and away-Stellera locations. The nitrate in Stellera topsoilwas 113% and 90% higher on the flat valley and on the south-facing slope,respectively. Both microbial biomass C and N were significantly higher in Stelleratopsoil. Gross nitrification and microbial respiration were significantly higher inStellera topsoil both on the flat valley and on the south-facing slope, whereassignificant differences of denitrification were found only on the flat valley. Thedifferences in the quantity and quality of aboveground litter are a likely mechanismresponsible for the changes of soil variables. We assumed that S. chamaejasme couldenhance their spread by increasing nutrient availability in N-deficient ecosystems. The results in the non-growing season showed that microbial biomass achievedthe first summit in late autumn and early winter on the eastern Qinghai-TibetanPlateau. In the stages of freeze-thaw of spring, microbial biomass firstly achieved thesecond summit and subsequently sharply decreased. Inorganic nitrogen, solubleorganic carbon and nitrogen had a similar dynamics with that of microbial biomass.Ratio of microbial biomass carbon and nitrogen had an obviously seasonal pattern.The highest microbial C: N were in the non-growing season, which weresignificantly higher than those in the growing season. The seasonal pattern inmicrobial biomass C: N suggested that large changes in composition of microbialpopulation and in resources those used by microbes between summer and winter.Generally, microbial biomass and pools size of carbon and nitrogen in Stellera soilwere significantly higher than those under adjacent locations in late autumn andearly winter, but there were not significant differences in winter and in spring. Litterof all the focal species (Stellera chamaejasme L., Polygonum macrophyllum D. Donvar. Macrophyllum, Poa pretensis L., Kobresia setchwanensis Hand.-Maizz.,Potentilla anserina L. var. anserine and G. squarrosa Ledeb.) decomposed about24%-50% in the non-growing season, which were higher than those in the growingseason (ranged from 10% to 30%). Litter decomposed 10%-20% within the first twoweeks in late autumn and early winter. Significant differences in the whole-yeardecomposition rate and in the processes of decomposition were found among species.Polygonum macrophyllum decomposed slowly through the whole year (26% and15% in the non-growing season and in the growing season, respectively). Certainspecies, such as P. pretensis L. and K. setchwanensis, decomposed at a similar rate(30% both in the non-growing and in the growing season, slightly higher in the8growing season than those in the growing season), whereas S. chamaejasmedecomposed more rapidly (about 50%) in the non-growing season and subsequentlydecomposition became slow (about 12%) in the growing season. Litter nitrogencontents of all the focal species firstly decreased in the non-growing season and thenincreased in the growing season. In vitro experiments of pollen allelopathy, the results showed that pollen from S.chamaejasme was not autotoxic, whereas pollen germination in all the sympatricspecies (Polygonum macrophyllum D. Don var. Macrophyllum, Gentianamacrophylla Pall. var. fetissowii, Gentianopsis paludosa (Hook. f.) Ma var. paludosa,Gentiana squarrosa Ledeb., Halenia elliptica D. Don var. elliptica, Cyananthushookeri C. B. Cl. var. grandiflorus Marq., Euphrasia pectinata Ten., Delphiniumtongolense Franch., Ranunculus tanguticus (Maxim.) Ovcz. var. tanguticus andPotentilla anserina L. var. anserina) decreased nonlinearly as the increasingconcentrations of extract of pollen from S. chamaejasme. Pollen Extract of threepollens from S. chamaejasme generally inhibited 50% pollen germination of most ofthe focal species. 5.76 and 3.35 pollens from S. chamaejasme were observed in fieldon stigmas of G. squarrosa and E. pectinata, respectively. Differences inheterospecific pollen transfer of S. chamaejasme could be attributed to the primaryreason whether they shared common pollinators. Flower morphology (e.g.zygomorphic or actinomorphic), plant or floral density and concurrence in floweringphonologies could explain, in part, the differences in heterospecific pollen transfer.In field experiments, the results showed that seed set in six sympatric species(Gentiana macrophylla Pall. var. fetissowii, Gentianopsis paludosa (Hook. f.) Mavar. paludosa, Gentiana squarrosa Ledeb., Halenia elliptica D. Don var. elliptica,Cyananthus hookeri C. B. Cl. var. grandiflorus Marq. and Euphrasia pectinata Ten.)decreased nonlinearly as the increasing concentrations of extract of pollen from S.chamaejasme. According to the nonlinear curves, the amounts of pollens from S.chamaejasme on stigmas of G. squarrosa and of E. pectinata (i.e. 5.76 grains and3.35 grains, respectively) could reduce 63% and 55% seed set of G. squarrosa and ofE. pectinata, respectively. Thus, allelopathic effects of S. chamaejasme on G.squarrosa and E. pectinata could be realistic. The sympatric species of S.chamaejasme could avoid pollen allelopathy of S. chamaejasme to sustainthemselves. This highlights the need to study how much pollen allelopathy in S.chamaejasme influences the sympatric species through divergence in seasonal ordiurnal flowering phonologies or through asexual reproduction. If pollen allelopathyin S. chamaejasme was confirmed, it could be as a pressure of natural selection andthus play an important role in species evolution.