【作者】 刘俊英；

【导师】 王文颖；

【作者基本信息】 青海师范大学 ， 植物学， 2010， 硕士

【摘要】 本论文试图以青藏高原高寒草甸生态系统为研究背景,利用植物营养生态学的理论知识,定量研究高寒优势植物种在无竞争环境中对土壤氨基酸和无机氮的吸收、野外原位研究嵩草草甸优势物种在土壤氮素的吸收形态上发生生态位分化的程度,检验群落中主要植物种在土壤氮资源吸收过程中产生生态位分化的程度,揭示高寒植物有机营养特征,加深对陆地高寒草甸生态系统氮循环的理解,为青藏高原高寒草甸生态系统的可持续发展模式提供科学依据。研究结果如下:（1）高寒矮嵩草草甸、藏嵩草草甸和退化矮嵩草草甸土壤中的优势个体游离氨基酸分别是:苯丙氨酸、天冬氨酸、亮氨酸、精氨酸、脯氨酸、谷氨酸和甘氨酸,它们占总游离氨基酸含量的70-90%,且这种趋势随草地类型与时间的变化不明显。藏嵩草草甸整个生长季总游离氨基酸态氮平均浓度为6.90mg mg/kg干土,在5.47-8.29 mg/kg范围内变化,最高值出现在6月30日左右。矮嵩草草甸平均浓度为7.44mg N/kg干土,在4.50-10.82 mg/kg范围内变化,最高值出现在5月31日左右。退化矮嵩草草甸土壤总氨基酸氮季节变化不显著,平均浓度为5.04 mg/kg.（2）燕麦、垂穗披碱草、老芒麦和中华羊茅对不同形态和浓度的氮素（无机和有机氮）处理的表现不同。燕麦根茎比对不同形态氮处理表现总体不是十分明显。不同浓度硝酸钾、硝酸铵和苯丙氨酸处理对垂穗披碱草根茎比影响显著,均表现为随浓度升高根茎比显著降低。老芒麦除了对不同浓度甘氨酸表现不显著外,对其他几种无机氮、有机氮浓度变化表现出显著的差异,均随着浓度增加根茎比显著下降。而中华羊茅仅对不同浓度的氯化铵和硝酸铵表现出明显的差异,随浓度升高根茎比显著降低。垂穗披碱草在各类氮素培养液中随着氮素浓度的升高,植物体内氮积累量逐渐升高。但燕麦在各类氮形态培养液中植株氮素积累量表现不一致。但可以说明两种植物在无菌氮素培养条件下均可以吸收有机氮。（3）在高寒矮嵩草草甸和藏嵩草草甸野外原位注射¹⁵N标记的¹⁵NH₄Cl、K¹⁵NO₃、¹⁵N甘氨酸和¹⁵N天冬氨酸溶液,结果证明:高寒草甸除豆科植物共生固氮外,还有藏嵩草沼泽草甸藏嵩草、华扁穗草、黑褐苔草,矮嵩草草甸麻花艽具有特殊的吸收氮素营养的方式,应该属于非豆科固氮植物。这可能是首次在高寒草甸生态系统发现多种具特殊方式获取氮源的植物,对高寒湿地生态系统氮循环有重要的理论指导意义;从高寒草甸主要植物利用土壤有机氮的能力看:矮嵩草草甸的矮嵩草、藏嵩草草甸的毛茛、草地早熟禾、针叶苔草、冷地早熟禾吸收甘氨酸的能力比其他植物种强,从土壤吸收的氮中25-35%是由甘氨酸贡献的。这些数据证实:高寒草甸有多种植物尤其是湿、中生植物可以有效利用可溶性有机氮源,特别是氨基酸,而且不同的植物种之间在氮素吸收上存在多样化特点。借此可以解释在速效氮为限制因子的生境中,为什么能形成丰富的物种多样性,植物又是如何高效利用限制性氮资源的。更多还原

【Abstract】 This research is conducted at the alpine meadow ecosystem on Qinghai-Tibet Plateau. By theoretical knowwledge in plant nutrition ecology , we want to determine the uptake kinetics of NH₄⁺、NO₃^-,a variety of amino acids by alpine dominant spieces in rivalless circumstance and to examine extent of niche separation in N source uptake of diffeerent plant species in alpine communties.Through above research ,we may improve our understandings of the nutrition characteristics of alpine plant species,N cycle of and alpine meadowecosystem and provide scientific basis tor sustainable development of alpine meadow ecosystem on Qinghai-Tibet plateau.（1）There are some advantage respective free amino acid in Alpine Kobresia humilis meadow、K. tibetica meadow、and degenerative Kobresia humilis meadow soil.They are phenylalanine, aspartic acid、leucine, arginine, proline、glutamic acid and qlycocoll. They accounted 70-90 percent in total free amino acid.The trend is not remarkable with the type of meadow and the change of time. Throughout the growing season the average concentration of total free amino acid N is 6.90mg N/kg in dry soil in K. tibetica meadow.The highest value happens about in June 30th between 5.47 to 8.29mg/kg.In Kobresia humilis meadow the average concentration is 7.44N/kg in dry soil. It changes between 4.50 to 10.82 mg/kg in degenerative Kobresia humilis meadow soil total amino nitrogen is not significant with season change, the average density is 5.04 mg/kg.（2）Helictotrichon、Festuca sinensis、E. nutan and Elymus has different performances to management in different forms and concentration nitrogen（inorganic and organic nitroge ） Helictotrichon,s rootstalk proportion performance is not very obvious to different nitrogen treatment. Different concentrations , E. nutans ,s rootstalk proportion is significant in nitrate、ammonium nitrate and benzedrine .Their rootstalk proportion significantly reduced.with nitrogen accumulation. Elymus has no significant performance in glycine of different concentrations but in other kinds of inorganic nitrogen, organic nitrogen it has significant performance.Its rootstalk proportion is depressed with increased concentration.But Festuca sinensis rootstalk proportion showed obvious differences in defferent concentration ammonium and ammonium nitrate Its rootstalk proportion significantly reduced.with nitrogen accumulation.E. nutans nitrogen concentration increases with nitrogen accumulation in all kinds of nitrogen forms treatment .But Helictotrichon ,s nitrogen accumulation is not consistent in all kinds of nitrogen forms treatment.But it can explain the two plants can absorb organic nitrogen in sterile training conditions （3）We injece 5NH₄Cl、K¹⁵NO₃、¹⁵N-Glycine and ¹⁵N-Asp in alpine Kobresia humilis meadow and K. tibetica meadow the results showed: except Leguminosae plants is symbiotic nitrogen fixation, we found that Kobresia tibetica, Blysmus sinocompressus, Carex atro-fusca, Gentiana straminea can uptake nitrogen by special way, maybe they belong to non-leguminous nitrogen-fixing plants. To our knowledge, this is the first documentation that there are many plant species uptake nitrogen by special way in alpine meadow; As far as plant uptake of organic N was concerned, Kobresia humilis, Ranunculus brotherusii, Poa pratensis, Carex duriuscala, Poa crymophila can effective uptake organic nitrogen. 25-35% of plant nitrogen comes from soil glycine. These data showed many plant species in alpine meadow may effective utilize dissolve organic nitrogen such as amino acids, and there are diversity ways of uptake nitrogen of different species in alpine meadow.更多还原