中文摘要：

近年来大量的氮添加实验表明,持续氮沉降往往会造成植物生长由氮限制转变为磷限制或氮磷共限制,但目前还很少有报道涉及磷添加或氮磷共同添加以研究氮磷元素之间的平衡/失衡的生态后果。本研究依托额尔古纳氮磷添加平台,研究了草甸草原4种优势植物羊草（Leymus chinensis）、贝加尔针茅（Stipa baicalensis）、狭叶柴胡（Bupleurum scorzonerifolium）和披针叶黄华（Thermopsis lanceolata）根系及叶片碳（C）、氮（N）、磷（P）含量与计量特征的变化。结果表明：氮添加或磷添加对4种植物根、叶部的C含量均无显著影响;磷添加对羊草、贝加尔针茅和狭叶柴胡的根、叶部N含量和C∶N无显著影响,对羊草根部、狭叶柴胡叶部的P含量和C∶P也无显著影响,但显著增加了羊草叶、狭叶柴胡根以及贝加尔针茅根和叶部的P含量,降低了其C∶P;氮添加显著提高了羊草、贝加尔针茅和狭叶柴胡根、叶部的N含量,降低了其C∶N,对羊草和狭叶柴胡根、叶部的P含量和C∶P无显著影响,但显著增加贝加尔针茅根、叶部的P含量和降低其C∶P,同时显著提高了羊草、贝加尔针茅和狭叶柴胡根、叶部的N∶P;氮添加和磷添加对豆科植物披针叶黄华根、叶部的养分含量与计量特征均无显著影响;氮磷添加对4种植物根、叶部养分含量与计量特征的影响均不存在显著交互作用。研究结果说明,物种属性在决定植物养分和化学计量特征对养分富集的响应方面发挥着重要作用。不同物种养分含量和计量特征发生的改变对于预测未来养分富集情况下植物群落组成的改变将具有重要参考意义。

英文摘要：

There is increasing evidence showing that the nutrient limitation status of plant growth would shift from nitrogen（ N） limitation to phosphorus（ P） limitation or to N and P co-limitation following long-term N deposition. Yet we know little about the ecological consequences of such changes in the relative availability of N and P. In the present study,we examined the chemistry and stoichiometry of C,N,and P in both leaves and roots of four dominant plant species in a meadow steppe of Hulunbuir,including Leymus chinensis,Stipa baicalensis,Bupleurum scorzonerifolium and Thermopsis lanceolata. Our results showed that both N and P addition had no significant impacts on C concentration in roots and leaves of all the species. Phosphorus addition showed no significant impacts on N concentration and C ∶ N ratios in root and leaves of L. chinen-sis,S. baicalensis and B. scorzonerifolium. In contrast,P addition significantly increased P concentration in leaves of L. chinensis and S. baicalensis and that in roots of B. scorzonerifolium and S. baicalensis. Nitrogen addition significantly enhanced N concentrations and decreased C ∶ N ratio in roots and leaves of L. chinensis,S. baicalensis,and B. scorzonerifolium,but had no significant effects on P concentration and C ∶ P ratio in roots and leaves of L. chinensis and B. scorzonerifolium. Moreover,N addition significantly increased the P concentration and decreased the C ∶ P ratio in roots and leaves of S. baicalensis. We found positive effects of N addition on N ∶ P ratio of plant tissue in three out of the four species. All the examined nutrient characters in T.lanceolata showed no significant responses to both N and P addition. We found no significant interactive effects of N and P additions on the chemistry and stoichiometry of plant tissue. Results from this study highlight the role of species identity in driving the responses of plant stoichiometry to the alteration of nutrient availability,which would help predict the changes of plant community compositi