【作者】 袁志友；

【导师】 韩兴国； 李凌浩；

【作者基本信息】 中国科学院研究生院（植物研究所） ， 生态学， 2004， 博士

【摘要】 Berendse & Aerts(1987) 认为氮素利用效率(nitrogen rise efficiency，NUE)可以分为两部分的乘积，即：① 氮素生产力(nitrogen productivity，NP)，② 氮素的平均滞留时间(mean residencetime，MRT)。本文利用这一概念对处于我国北方农牧交错带的内蒙古自治区多伦县典型植物的氮素利用策略进行了研究。研究假设：植物在贫瘠生境上所采取的氮素适应策略主要是提高对所吸收氮素的保持能力(较长的MRT)，而不是提高NUE。在不同土壤生境上，属于不同生活型的不同物种其NP和MR7之间存在负相关关系。在不同生境、生活型和物种之间，作为NP与MRI乘积的NUE比NP、MRI的变化相对要小，结果表明植物主要通过延长MRT来适应氮素贫瘠的生境。因为NP与MRT朝相反的方向变化，二者不能同时增加或减少，所以NP与MRT之间存在相互协调(trade-off)的关系。在群落和生态系统水平上，NP与MRT之间也存在相互协调关系，不同水平上的NUE-之间也存在一定的联系。除了在种间存在这种关系外，通过对多伦县和十三里滩两种针茅(大针茅、克氏针茅)的氮素利用特征的研究，发现在种内，NP与MRT之间也存在这种相互协调关系。NUE与土壤供氮能力有关，随着土壤供氮能力的下降，NUE呈上升趋势。植物的NUE不仅与土壤的供氮能力有关，其它因素如土壤水分供应状况也会对植物的NUE产生影响，例如，与生长在河岸上的植物相比，生长在河滩湿地上的植物具有较高的NP，但MRT却较低。在群落中，不同植物个体的NUE及其组成参数NP和MRT也存在较大的差异，较大的植株具有较高的NP和MRT，因而NUE也高于个体较小的植株。本文研究结果表明，植物的NUE与氮素回收转移特性密切相关，植物提高氮素同收效率(nitrogen resorption efficiency，NRE)可以延长MRT，从而提高NUE。更多还原

【Abstract】 Nitrogen (N) use strategies of typical species in the semiarid area, an agro-pastoral ecotone, of northern China were analysed using the concept of nitrogen use efficiency (NUE) proposed by Berendse & Aerts (1987). NUE can be decomposed into (1) the nitrogen productivity (NP) and (2) the mean residence time (MRT). In particular, this thesis addressed the hypothesis that plants adapt to infertile habitats by nitrogen conservation (long MRT) rather than a high NUE.I found a negative relationship between NP and MRT in a field study comparing species of contrasting life-forms. Consequently NUE, i.e. the product of NP and MRT, was relatively constant across species, habitats and life-forms. These results offered support to the hypothesis that adaptation to infertile habitats involves a long MRT rather than a high NUE per se. There appeared to be a trade-off between NP and MRT, since both components of NUE could not be maximised together.This trade-off was also found at community and ecosystem levels from field data. This suggested that there were links among NUE at different levels. Data from variation in N use traits of Stipa species indicated that there was a trade-off within species, as well as among species. The NUE was studied in relation to habitat fertility. Other factor, such as soil water content, also determine N use. Although the species grown in the riverine wetland had larger NP by virtue of adequate water supply, they had lower MRT than the species grown in river bank. This suggested that the environmental factor such as water availability, strongly influenced N use by plants. NUE and its components, NP and MRT, were different among individuals. Both NP and MRT positively related to their plant size. Data from N resorption efficiency and N resorption proficiency suggested that lower N concentration in living tissues and greater N resorption during senescence would have contributed to the higher N use efficiency.更多还原