343 resultados para Aço vazado ASTM A148 90-60
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应用光纤列阵耦合方式,对大功率半导体激光器线列阵输出光束的快轴方向用一根柱透镜准直,准直后的光速耦合到光纤列阵中,实现出纤功率为60瓦的大功率半导体激光二极管线列阵光纤耦合效率大于80%,光纤的数值孔径NA为0.11。
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国家自然科学基金
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于2010-11-23批量导入
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目的:分析单侧咀嚼运动中工作侧、非工作侧(牙合)接触面积的变化规律.方法:18例口颌系统功能正常的受试者用右侧咀嚼3 g口香糖.采用虚拟颅颌运动仿真系统模拟咀嚼运动,分析咀嚼循环闭口阶段4个时刻的(牙合)接触面积,即:(牙合)接触初、1/3时刻、2/3时刻、下颌位于牙尖交错位.结果:在工作侧,(牙合)接触总面积从(9.3±0.4)mm2增至(39.2±1.2)mm2,第一磨牙的(牙合)接触面积从(3.7±0.2)mm2增至(14.8±0.7)mm2,第二磨牙的(牙合)接触面积从(3.5±0.2)mm2增至(13.9±0.4)mm2.在非工作侧,(牙合)接触总面积从(2.3±0.5)mm2增至(40.3±1.2)mm2,第一磨牙的(牙合)接触面积从(0.5±0.2)mm2增至(13.6±0.5)mm2,第二磨牙的(牙合)接触面积从(1.2±0.3)mm2增至(12.1±0.5)mm2.此外,在(牙合)接触初,18例受试者中有12例出现了非工作侧(牙合)接触;至2/3时刻,所有受试者均出现了非工作侧(牙合)接触.结论:提供了一种新的(牙合)接触评价方法,可用于分析下颌功能运动中的(牙合)接触;揭示了单侧咀嚼运动闭口阶段的(牙合)接触模式,同时发现咀嚼运动中普遍存在非工作侧(牙合)接触.
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通过对抚顺市温道林场20、53和69年生长白落叶松(Larix olgensis)人工林生物量和营养元素的积累与分配、养分利用效率和养分再吸收效率、养分生物循环的研究,探讨了长白落叶松生长发育不同阶段的养分生态学特征;对东北林业大学帽儿山实验林场17年生兴安落叶松(Larix gmelinii)人工林进行5年的施肥(NH4NO3,15 g•m-2•a-1),研究了施肥对人工林养分生物循环的影响。结果表明: (1)20、53和69年生单株落叶松生物量分别为33.14 kg•tree-1、311.42 kg•tree-1和408.46 kg•tree-1,随林龄的增长而增加。各器官生物量的分配格局为:树干>根>树枝>树皮>针叶。树干生物量的分配比例为50.16%~69.20%,随林龄的增长比例增大,而其他器官生物量的分配比例则逐渐减小。20、53和69年生单株落叶松净生产力分别为3.04 kg•tree-1•a-1、9.68 kg•tree-1•a-1和10.21 kg•tree-1•a-1,随林龄的增长而增大。针叶和树干的净生产力最大,分别占整株林木净生产力的40.07%~47.93%和27.32%~40.97%,并且随林龄的增长而增大。树枝、树皮和根的净生产力则表现出随林龄的增长呈抛物线状。 (2)20、53和69年生单株落叶松N、P、K、Ca、Mg等5种营养元素的总贮量分别为308.14 g•tree-1、2021.01 g•tree-1和2485.24 g•tree-1,随林龄的增长而增加。5种营养元素的贮量大小为:Ca>N>K>Mg>P。树干养分贮量的分配比例为19.74%~34.23%,随林龄的增长呈抛物线状。针叶、树枝和树皮的养分贮量占整株林木养分贮量的比例为35.16%~45.59%,建议在采伐木材时实施去皮、打枝等措施,留下针叶、树枝和树皮在林地中,让其自然分解以使营养元素重新归还利用,对于维持林地的养分平衡和长期生产力具有积极作用。 (3)20、53和69年生单株落叶松年吸收养分量分别为35.31 g•tree-1•a-1、97.83 g•tree-1•a-1和100.08 g•tree-1•a-1,随林龄的增长而增加。5种营养元素的年吸收量大小为:Ca>N>K>Mg>P。落叶松的养分利用效率随林龄的增长而增大,但生长到一定年龄阶段后,其养分利用效率逐渐趋于稳定。落叶松的最佳采伐年龄应为养分利用效率保持稳定时的年龄,此时采伐单位干材所带走的林地养分量较少。不同营养元素的利用效率不同,P的利用效率最高,Mg、K次之,N、Ca最低。不同器官的养分利用效率不同,树干的养分利用效率最高,其次是根、树枝、树皮,针叶最低。随着林龄的增长,树干和根的养分利用效率增大,而树枝和树皮的养分利用效率减小。 (4)落叶松叶片的N再吸收效率为50.76%~55.11%,随林龄的增长表现出增大的趋势;P和K再吸收效率分别为64.38%~68.85%和87.85%~90.62%,随林龄的增长表现出减小的趋势。从养分利用效率和养分再吸收效率综合判断,本研究区落叶松生长可能受土壤N、P、K供应的限制,3种营养元素的限制作用大小为:K>P>N。 (5)落叶松人工林养分的年吸收量、年存留量和年归还量分别为51.94~78.35 kg•hm-2•a-1、17.77~29.43 kg•hm-2•a-1和34.18~48.92 kg•hm-2•a-1,均随林龄的增长而减少,这与林分密度逐渐减小有关。5种营养元素的年吸收量和年存留量大小均为:Ca>N>K>Mg>P,年归还量大小为:Ca>N>Mg>K>P。落叶松人工林的养分循环速率为0.624~0.658,随林龄的增长而增大。5种营养元素的循环速率以Mg、N最快,Ca、P次之,K最慢。K的循环速率较低,可能与研究区土壤K含量较低而表现出的K再吸收效率较高有关。 (6)施肥导致落叶松叶片N再吸收效率显著降低,而凋落叶片的N浓度显著增加,从而使凋落叶片的C/N比由80.29降低到60.29。施肥林地凋落叶片C/N比的降低使其分解速率加快,有利于其养分归还土壤,从而加快了系统的养分循环速率,提高了系统的养分利用率。因此,在人工林经营中,施肥不仅能提高林地生产力,而且对于维持林地养分循环具有积极作用。
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根土生态界面的研究是一个全新的课题,其研究方法和测定技术是进行此项研究首先需要解决的问题。本文以长白山地区阔叶红松林的主要树种:红松(Pinus koraiensis)、核桃楸(Juglans mandshurica)、水曲柳(Fraxinus mandshurica)和紫椴(Tilia amurensis)为研究对象,对其研究方法和技术进行探索和试验,同时对红松幼苗根土生态界面及其过程进行了研究。对四种树种的三年生幼苗进行了根土生态界面环境面一侧一根际的pH值和氧化还原状况的原位显色,结果表明,红松和核桃楸的根际呈酸性(5.2 < pH < 6.0),水曲柳和紫椴的根际呈碱性(pH > 7.5),并由此推断出红松根系分泌质子的部位,主要表现在根尖以上4.5-8cm范围内。四种苗木根际的氧化还原状况均为氧化型。运用电子探针技术对红松幼苗根土生态界面进行定量的点分析,并依据界面中营养元素(N、P、K、Mg)的浓度梯度对根土生态界面进行刻画,结果表明,以N来刻画,其根土生态界面的范围是从根60μm到土40μm(以根表为分界线,分别向根组织方向和土壤方向测点),变动空间是100μm;以P刻画的根土生态界面的范围的从根40μm到土20μm,变动空间是60μm;以K刻画的根土生态界面的范围是从根30μm到土90μm,变动空间是120μm;以Mg来刻画,其根土生态界面的范围是从根20μm到土10μm,变动空间为30μm。应用根垫法的模拟培育装置对根土生态界面环境面一侧一根际的养分状况进行了研究,结果表明;随着培育过程的延续,营养元素的亏缺区增大,界面宽度增加;同一时间,同一处理,亏缺区的范围是N > K > P,表明其在土壤中的扩散的N > K > P,与已有的知识相吻合;红松幼苗对营养元素N、P、K的吸收均为对数型。从以上的试验结果,证明根垫法模拟培育装置在林木根际研究中是可行的,但还有有待改进的地方。根据以上的实验结果,对阔叶红松林的经营提出了几点对策性建议。
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含油浮渣是含油污水处理的末端废弃物,产生于处理工艺中的气浮单元,属于含油固体废弃物。目前国内尚无有效的处理工艺,大部分采用堆储方式处理。本文以辽河油田含油浮渣为研究对象,通过对含油浮渣理化性质的研究提出了以反絮凝为技术核心的处理工艺,并在此基础上进行的浮渣的减量化和无害化处理的技术研究。结果表明:通过反絮凝可完全破坏浮化絮凝团的结构,从根本上改变浮渣的流动性,浮渣的脱水性能也得到了显著改善。含油浮渣减量化小试试验根据传统的压滤工艺,采用反絮凝技术作为前处理工艺,浓缩脱水率达50%~60%,压滤脱水率明显提高,压滤后浮渣体积减量90%以上。研究还通过减量化中试试验完善了工艺流程与参数,实验结果显示,样品压滤后含水率从97.4%降低至60.7%,浮渣体积减量94.4%。含油浮渣无害化小试试验,对含油浮渣进行了反絮凝一水基清洗无害化处理,油总的去除率在50%~60%之间,含油浮渣最终的含水率在94%-95%,含油率在0.8%~1.2%。
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在地处亚热带,酸雨污染严重的重庆地区土壤上,近一年的定位研究表明:1)酸雨促进了马尾松针叶林林内降水的酸化和元素的淋失。在重污染的城区针叶林,其冠流和干流pH分别为3.71和2.75,离子含量分别是郊区冠流、干流的1.2-3.2倍和1.1-2.7倍。2)森林死地被物层对酸性降水有中和、缓冲作用,其中阔叶林死地被物层作用大于针叶林。3)酸雨有助于马尾松针叶林黄壤的酸化和土壤溶液中离子含量的增加。重污染的城区与轻污染的郊区比较,土壤溶液pH低0.2-0.8,而离子含量却普遍增高。4)在重庆地区的土壤溶液中,SO~(2-)_4是优势阴离子,占所测阴离子总量的60-90%,但土壤溶液中Al~(3+)含量却很低。目前土壤溶液中Al~(3+)不可能对树木产生毒害作用。
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由于人类活动所引起的地球大气层中温室气体的富集已导致全球地表平均温度在20 世纪升高了0.6 ¡æ,并预测在本世纪将上升1.4-5.8 ¡æ。气候变暖对陆地植物和生态系统产生深远影响,并已成为全球变化研究的重要议题。位于青藏高原东部的川西亚高山针叶林是研究气候变暖对陆地生态系统影响的重要森林类型。森林采伐迹地和人工云杉林下作为目前该区人工造林和森林更新的两种重要生境,二者截然不同的光环境对亚高山针叶林不同物种更新及森林动态有非常重要的影响。 本文以青藏高原东部亚高山针叶林几种主要森林树种为研究对象,采用开顶式增温法(OTCs)模拟气候变暖来研究增温对生长在两种不同光环境下(全光条件和林下低光环境)的几种幼苗早期生长和生理的影响,旨在从更新角度探讨亚高山针叶林生态系统不同树种对气候变暖在形态或生理上的响应差异,其研究结果可在一定程度上为预测气候变暖对亚高山针叶林物种组成和演替动态提供科学依据,同时也可为未来林业生产管理者提供科学指导。 1、与框外对照相比,OTCs 框内微环境发生了一些变化。OTCs 框内与框外对照气温年平均值分别为5.72 ¡æ和5.21 ¡æ,而地表温度年平均值分别为5.34 ¡æ和5.04 ¡æ,OTCs 使气温和地表年平均温度分别提高了0.51 ¡æ和0.34 ¡æ;OTCs框内空气湿度年平均值约高于框外对照,二者分别为90.4 %和85.3 %。 2、增温促进了三种幼苗生长和生物量的积累,但增温效果与幼苗种类及所处的光环境有关。无论在全光或林下低光条件下,增温条件下云杉幼苗株高、地径、分支数、总生物量及组分生物量(根、茎、叶重)都显著地增加;增温仅在全光条件下使红桦幼苗株高、地径、总生物量及组分生物量(根、茎、叶重)等参数显著地增加,而在林下低光条件下增温对幼苗生长和生物量积累的影响效果不明显;冷杉幼苗生长对增温的响应则与红桦幼苗相反,增温仅在林下低光条件下对冷杉幼苗生长和形态的影响才有明显的促进作用。 增温对三种幼苗的生物量分配模式产生了不同的影响,并且这种影响也与幼苗所处的光环境有关。无论在全光或林下低光环境下,增温都促使云杉幼苗将更多的生物量分配到植物地下部分,从而导致幼苗在增温条件下有更高的R/S 比;增温仅在林下低光条件下促使冷杉幼苗将更多的生物量投入到植物叶部,从而使幼苗R/S 比显著地降低;增温在全光条件下对红桦幼苗生物量分配的影响趋势与冷杉幼苗在低光条件下相似,即增温在全光条件下促使红桦幼苗分配更多的生物量到植物同化部分—叶部。 3、增温对亚高山针叶林生态系统中三种幼苗气体交换和生理表现的影响总体表现为正效应(Positive),即增温促进了几种幼苗的生理活动及其表现:(i)无论在全光或林下低光环境下,增温使三种幼苗的光合色素含量都有所增加;(ii)增温在一定程度上提高了三种使幼苗的PSII 光系统效率(Fv/Fm),从而使幼苗具有更强的光合电子传递活性;增温在一定程度使三种幼苗潜在的热耗散能力(NPQ)都有所增强,从而提高幼苗防御光氧化的能力;(iii)从研究结果来看,增温通过增加光合色素含量和表观量子效率等参数而促进幼苗的光合作用过程。总体来说增温对幼苗生理过程的影响效果与幼苗种类及所处的光环境有关,增温仅在全光条件下对红桦幼苗光合过程的影响才有明显的效果,而冷杉幼苗则相反,增温仅在低光条件下才对幼苗的生理过程有显著的影响。 4、增温对三种幼苗的抗氧化酶系统产生了一定的影响。从总体来说,增温使几种幼苗活性氧含量及膜脂过氧化作用降低,从而在一定程度上减轻了该区低温对植物生长的消极影响;增温倾向表明使三种幼苗体内抗氧化酶活性和非酶促作用有所提高,从而有利于维持活性氧代谢平衡。但增温影响效果与幼苗种类所处的光环境及抗氧化酶种类有关,增温对冷杉幼苗抗氧化酶活性的影响仅在林下低光环境下效果明显,而对红桦幼苗抗氧化酶活性的影响仅在全光条件下才有明显的效果。 总之,增温促进了亚高山针叶林生态系统中三种幼苗的生长和生理表现,但幼苗生长和生理对增温的响应随植物种类及所处的光环境不同而变化,这种响应差可能异赋予了不同植物种类在未来气候变暖背景下面对不同环境条件时具有不同的适应力和竞争优势,从而对亚高山针叶林生态系统物种组成和森林动态产生潜在的影响。 Enrichment of atmospheric greenhouse gases resulted from human activities suchas fossil fuel burning and deforestation has increased global mean temperature by 0.6¡æ in the 20th century and is predicted to increase it by 1.4-5.8 ¡æ. The globalwarming will have profound, long-term impacts on terrestrial plants and ecosystems.The ecoologcial consequences arising from global warming have also become thevery important issuses of global change research. The subalpine coniferous forests inthe eastern Qinghai-Tibet Plateau provide a natural laboratory for the studying theeffects of climate warming on terrestrial ecosystems. The light environment differssignificantly between clear-outs and spruce plantations, which is particularlyimportant for plant regeneration and forest dynamics in the subalpine coniferous forests. In this paper, the short-term effects of two levels of air temperature (ambient andwarmed) and light (full light and ca. 10% of full light regimes) on the early growthand physiology of Picea asperata, Abies faxoniana and Betula albo-sinensis seedlingswas determined using open-top chambers (OTCs). The aim of the present study wasto understand the differences between tree species in their responses to experimentalwarming from the perspective of regeneration. Our results could provide insights intothe effects of climate warming on community composition and regeneration behavior for the subalpine coniferous forest ecosystem processes, and provide scientificdirection for the production and management under future climate change. 1. The OTCs manipulation slightly altered thermal conditions during the growingseason compared with the outside chambers. The annual mean air temperature andsoil surface temperature was 5.72 and 5.34 ¡æ (within the chambers), and 5.21 and5.04 ¡æ (outside the chambers), respectively. The OTCs manipulation increased airtemperature and soil surface temperature by 0.51 and 0.34 ¡æ on average, respectively.Air relative humidity was slightly higher inside the OTCs compared with the controlplots, with 90.4 and 85.3 %, respectively. 2. Warming generally stimulated the growth and biomass accumulation of thethree tree species, but the effects of warming on growth and development variedbetween light conditions and species. Irrespective of light regimes, warmingsignificantly increased plant height, root collar diameter, total biomass, componentbiomass (stem, foliar and root biomass) and the number of branches in P. asperataseedlings; For A. faxoniana seedlings, significant effects of warming on all the tested parameters (plant height, root collar diameter, total biomass, and component biomass) were found only under low light conditions; In contrast, the growth responses of B.albo-sinensis seedlings to warming were found only under full light conditions. Warming had pronounced effects on the pattern of carbon allocation. Irrespectiveof light regimes, the P. asperata seedlings allocated relatively more biomass to rootsin responses to warming, which led to a higher R/S. Significant effects of warming onbiomass allocation were only found for the A. faxoniana seedlings grown under lowlight conditions, with significantly increased in leaf mass ratio (LMR) and decreasedin R/S in responses to warming manipulation. The carbon allocation responses of B.albo-sinensis seedling to warming under full light conditions were similar with theresponse of A. faxoniana seedlings grown under low light conditions. Warmingsignificantly decreased root mass ratio (RMR), and increased leaf mass ratio (LMR)and shoot/root biomass ratio (S/R) for the B. albo-sinensis seedlings grown under full light conditions. 3. Warming generally had a beneficial effect on physiological processes of dominant tree species in subalpine coniferous forest ecosystems: (i) Warming markedincreased the concentrations of photosynthetic pigments in both tree species, but theeffects of warming on photosynthetic pigments were greater under low lightconditions than under full light conditions for the two conifers; (ii) Warming tended toenhance the efficiency of PSII in terms of increase in Fv/Fm, which was related tohigher chloroplast electron transport activity; and enhance non-radiative energydissipation in terms of in increase in NPQ, which may reflect an increased capacity inpreventing photooxidation; (iii) Warming may enhance photosynthesis and advancephysiological activity in plants by increasing photosynthetic pigment concentration,the efficiency of PSII and apparent quantum yield (Φ) etc. From the results, theeffects of warming on seedlings’ physiological performance varied between lightenvironment and species. The effects of warming on photosynthesis performance of B.albo-sinesis seedlings were pronounced only under full light conditions, while thephysiological responses of A. faxoniana seedlings to warming were found only underthe 60-year plantation. These results provided further support for the observationsabove on growth responses of seedlings to warming. 4. Warming had marked effects on antioxidative systems of the three seedlings.Warming generally decreased H2O2 accumulation and the rate of O2- production, andalleviated degree of lipid peroxidation in terms of decreased MDA content, whichalleviated to some extent the negative effects of low temperature on the plant growthand development in this region; Warming tended to increase the activities ofantioxidative enzymes and stimulate the role of non-enzymatic AOS scavenging,which helped to create an balance in maintaining AOS metabolites for the threeseedlings. Nevertheless, the effects of warming on antioxidative defense systems werepronounced only under the 60-year plantation for the A. faxoniana seedlings. Incontrast, the marked effects of warming on antioxidative defense systems for the B.albo-sinesis seedlings were found only under the full light conditions. In sum, warming is considered to be generally positive in terms of growth andphysiological process. However, the responses of growth and physiology performanceto warming manipulation varied between species and light regimes. Competitive and adaptive relationships between tree species may be altered as a result of responsedifferences to warming manipulation, which is one mechanism by which globalwarming will alter species composition and forest dynamics of subalpine coniferousforest ecosystems under future climate change.
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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.