【作者】 赵君；

【导师】 王刚；

【作者基本信息】 兰州大学 ， 生态学， 2011， 博士

【摘要】 生态化学计量学从化学计量学的角度出发,结合生物学、化学和物理的基本理论,研究生命物质不同结构层次(分子、细胞、器官、机体、种群、群落、生态系统等)相互之间以及生态学过程中的元素之间的关系,是研究生物系统多重化学元素平衡和动态变化的科学,它将生态实体的各个层次(从基因,分子,细胞到个体,种群,生态系统以至生物圈)在元素水平统一起来,目前越来越广泛地应用于生态学各个领域的研究。化学计量内稳性是指环境或者食物中的养分组成发生变化而生物体维持相应的元素相对不变的能力,是生理和生化调节的反映。内稳态机制是生物在长期的进化过程中适应环境变化的结果,是生态化学计量学的基础理论。然而生态化学计量在不同的层次,不同领域的研究中表现为不同程度上的趋同和分异。氮(N)和磷(P)是植物的基本营养元素,也是生物系统和生物地球化学循环中的重要元素,在各级生命层次系统的结构和功能中占有重要地位,因此N、P的生态化学计量学受到生态学家们的普遍关注。有机体水平的生态化学计量学研究连接了生命系统的三个尺度：分子水平、有机体水平和大尺度的生态系统过程,因此有机体水平的N、P的生态化学计量学研究具有重要的生态学意义。环境(包括光、大气温度、土壤温度和土壤含水量等)和内部生理因素(包括生长、发育、繁殖、衰老等)共同影响N、P的化学计量的动态变化,但不同的内外因素下有机体的氮磷化学计量的动态及其理论机制的全面综合研究还鲜有报导。针对这一问题现状,本论文研究内容为在各种内外因素下植物有机体水平的N、P化学计量的动态及其理论机制。金露梅是甘南亚高寒草甸的优势灌木种,对生态系统的功能和稳定有重要作用。本论文选取甘南亚高寒草甸的金露梅为研究对象,从引起金露梅N、P元素变化的各种环境因素和内部因素入手,研究各种因素下金露梅N、P元素计量的动态,并且探讨其生态化学计量学机制。本研究包括四个实验：1.野外施肥实验模拟自然界不同的氮磷环境,研究施肥梯度下金露梅N、P计量的动态。2.除花实验研究繁殖对于金露梅N、P计量动态的影响。3.野外采集不同年龄的金露梅,探究随着年龄变化金露梅叶片氮磷计量的动态。4.研究不同坡向金露梅氮磷计量动态,探讨其与不同坡向的环境因子的关系。本研究主要结果和结论为：(1)施肥显著影响了叶片氮含量和叶片磷含量,施肥不同处理(0,40,80,120g/m2NH4H2PO4)的的叶片氮含量和磷含量依次提高；但施肥对氮磷比影响不显著(N：P比值范围[8.81,9.36],P>0.05)。植物叶片氮含量、磷含量的变异系数大于土壤氮含量、磷含量的变异系数。表明叶片氮磷比值比叶片的氮含量、磷含量具有更强的内稳性,在外部养分组成发生变化时,内稳态机制的动态平衡调节主要体现在植物的氮磷比值上,而氮含量、磷含量具有比较大的变化空间。(2)比较对照的繁殖金露梅植株叶片和花的N、P含量,表明了花中的磷含量显著大于叶片中的磷含量,而氮含量在花和叶片之间却没有显著差异。这是由于花比叶片需要更多的磷以合成DNA、RNA等完成繁殖过程。比较除花金露梅植株和对照繁殖植株的叶片N、P计量显示：繁殖显著降低了叶片的氮含量(P<0.01)和氮磷比(P<0.01),对叶片磷含量的影响不显著(P>0.05)。表明繁殖过程导致了叶片的氮的消耗和N：P的降低。其生理机制可能是由于繁殖导致的营养元素在花和叶片的重新分配。花中的磷含量大于叶片的磷含量,而叶片中的磷含量并没有显著降低,这是由于植物可以吸收足够的磷元素保证繁殖的进行。金露梅在内外因素的影响下分别表现了N：P比值的趋同和分异。在施肥引起的外界环境(这里是指土壤的养分组成)发生变化下,植物保持N：P比值的相对稳定性,这是内稳性机制的体现。繁殖个体花的氮磷比低于叶的氮磷比,繁殖个体叶的氮磷比低于非繁殖个体叶的氮磷比,表明了在繁殖这一植物内部重要的生活史阶段中,植物的N：P比值下降。相对于内稳态机制和生长速率机制(前者主要对应于外界环境的变化,后者主要对应于生长中),繁殖对植物氮磷的动态影响应该具有相对独立的机制,即繁殖降低叶片氮磷比值,繁殖对植物氮磷计量的影响不仅表现在叶片上,还表现在叶片与繁殖器官(花)的不同上。(3)金露梅叶片的磷含量在1-6年的不同年龄的植株中差异不显著(P>0.05),表明了磷含量在植株年生长中保持相对稳定的水平。叶片氮含量在1-6年的不同年龄的植株中变化较大。叶片氮磷比值与氮含量的动态基本一致。而每年繁殖导致的氮磷动态可以很好的解释年龄间氮磷的这种变化。相关分析显示：金露梅1-6年各年分别的年材积生长率与对应年龄的叶片氮含量、磷含量和氮磷比值均没有显著的相关性(P>0.05)。不同年龄的实验表明,金露梅叶片的N、P和N：P比值的在年龄间的动态更多受到繁殖的影响而非生长的影响。(4)不同坡向的环境因子影响金露梅的分布以及金露梅的氮磷化学计量动态。阳坡、半阴半阳坡、阴坡的土壤温度依次降低,并且差异具有显著性(P<0.05)。阴坡的土壤含水量显著大于阳坡和半阴半阳坡(P<0.05)。阳坡的光照度显著大于阴坡和半阴半阳坡(P<0.05)。阴坡的金露梅叶片的氮含量显著大于半阴半阳坡的叶片氮含量(P<0.05)。半阴半阳坡与阴坡的叶片磷含量没有显著性差异(P>0.05)。半阴半阳坡叶片的氮磷比值显著大于阴坡(P<0.05)。半阴半阳坡的金露梅叶片氮含量、磷含量和氮磷比值均比阴坡有更高的离散程度。相关分析表明了金露梅叶片氮含量与土壤温度和光照度都是显著的负相关。不同坡向的实验表明,光照度、土壤温度和土壤含水量均影响金露梅在不同坡向上的分布。土壤温度影响金露梅叶片的氮含量,趋势是温度越高金露梅叶片的氮含量越低,其生理机制低温对光合作用(即有机质的积累)的限制超过对植物吸收氮的抑制。随着光照度的增加,叶片的氮含量与氮磷比值均降低。更多还原

【Abstract】 Ecological stoichiometry is a new tool to study ecological process from genes to the biosphere. It has been successfully applied in many ecological studies in recent years. Stoichiometric homeostasis, the degree to which an organism maintains its elements ratios despite variation in the relative availabilities of elements in its resource supplies, is a key parameter in ecological stoichiometry. However, the ecology stoichiometry dynamics showed convergence and variation in studies at different levels. Nitrogen (N) and phosphorus (P) are essential for plant growth and their cyclings and play a key role in ecosystem processes. Organism level of ecological stoichiometry can connect to the three dimensions of the living system:the molecular level, the organism level and large scale ecosystem processes. Therefore, the studies in this area are very important for ecological development. Environment (including light, temperature, soil temperature and soil water content, etc) and internal factors (including growth, reproduction, aging, etc) interact to produce the observed patterns of internal plant nutrient stoichiometry, but we do not know much about such interactions. We studied the dynamics of nutrient stoichiometry in Potentilla fruticosa L. in relation to both two environmental (fertilization, slope) and two internal factors (reproduction, age)in a field experiment.We studied the effect of (a) four levels fertilization, (b) with and without flower removal, (c) 6 plant ages, (d) different slopes, on the N and P stoichiometry of naturally-occurring Potentilla fruticosa L. individuals.The main results and conclusions:1, Fertilization significantly increased the leaf N and P concentration; however N:P ratio was not significant affected by fertilization(range [8.81,9.36], P>0.05). CVs of leaf N and P were bigger than that of soil N and P. The results of fertilization experiments suggested that P. fruticosa L. showed a higher degree of homeostasis in N:P than N and P, maintaining internal nutrient stoichiometry under variation in external nutrient levels.Flower P was significantly higher than leaf P; there was no significant difference between flower N and leaf N. Flowers need more phosphorus to synthesize DNA, RNA etc for reproduction.2, Reproduction decreased leaf N and N:P significantly, whereas there was no significant effect on plant leaf P. It suggested that reproduction leads to lower leaf N and N:P. The physiological mechanism may be the re-allocation of N and P between flowers and leaves by caused by reproduction. Leaves to the reproductive organs of the transport of phosphorus, and phosphorus content of the flower than leaf phosphorus content. Flower P was more than leaf P which did not significantly decrease. That may be due to plants can absorb enough phosphorus to ensure the reproduction.N:P showed convergence and variation under internal(reproduction) and external (fertilization)factor respectively. The mechanisms may be Homeostatic mechanism and Reproduction mechanism respectively. Reproduction should have a relatively independent mechanism with the effects of nitrogen and phosphorus in plants: reproduction lead to reduce leaf N:P.3, Plant leaf P was generally stable through 1-6 ages. Plant leaf N appeared to fluctuate later in development when plants were reproducing. The dynamics of N:P are basically the same with leaf N, which can explained by Reproduction mechanism but can not explained by Growth rate hypothesis. The low N:P can also predict that the limited element is N not P.4, The research on the environmental factors from South-facing slope to North-facing slope showed that:The average value of soil temperature was that: South-facing slope>West-facing slope>North-facing slope (P＜0.05); Soil water content increased from South-facing slope to North-facing slope(P<0.05); Daily light intensity decreased from South-facing slope to North-facing slope (P＜0.05).The results of slopes experiments suggested that Daily light intensity, soil temperature and soil water content should be the key factors that affect the distribution of Potentilla fruticosa L. upward slope. Leaf N was significantly negative correlated in soil temperature. With the increase of light intensity, leaf N and N:P ratios decreased. The physiological mechanism of leaf nitrogen content decreases with soil temperature increases may be the adaptation of physiological and temperature in plant.更多还原