氮添加对贝加尔针茅草原植物和土壤化学计量特征的影响

以贝加尔针茅草原为研究对象,设置N₀(0 kg N·hm^-2)、N₃₀(30 kg N·hm^-2)、N₅₀(50 kg N·hm^-2)、N₁₀₀(100 kg N·hm^-2)、N₁₅₀(150 kg N·hm^-2)5个氮添加水平,研究不同氮添加水平对6种植物叶C、N、P计量特征和土壤C、N、P计量特征的影响,分析植物计量特征与土壤计量特征的相关性,为深入理解N沉降增加对草原群落结构的影响提供基础数据。结果表明,自然条件下,6种植物叶C、N、P含量和计量特征存在显著的差异,表现为扁蓿豆叶C、N、P含量和叶N∶P最高,贝加尔针茅叶N、P含量最低,线叶菊叶C含量最低。氮添加提高了除扁蓿豆以外其他5种植物叶N含量,叶C∶P和叶N∶P,降低了叶P含量和叶C∶N,而叶C含量无一致变化趋势。氮添加提高了土壤有机碳含量、土壤N∶P,对土壤全氮含量和土壤C∶N无显著性影响。羊草、羽茅、线叶菊和草地麻花头叶N含量与土壤有机碳、土壤N∶P呈显著正相关,贝加尔针茅、羊草、羽茅和草地麻花头叶N∶P与土壤有机碳、土壤C∶P呈显著正相关。综合分析表明,土壤有机碳、土壤N∶P和土壤C∶P是影响6种植物叶C、N、P含量和计量特征的主要影响因素,但不同植物对氮添加的响应不同,意味着长期氮添加可能会改变贝加尔针茅草原生态系统的结构。

Effects of nitrogen addition on the stoichiometric characteristics of plants and soil in the Stipa baicalensis grassland of Inner Mongolia,China

The objective of this study was to investigate the effects of nitrogen addition on soil and plant carbon (C), nitrogen (N), phosphorus (P) and C∶N∶P ecological stoichiometric characteristics in the Stipa baicalensis grassland of Inner Mongolia, China. The plant study focused on six dominant species: S. baicalensis, Leymus chinensis, Achnatherum sibiricum, Filifolium sibiricum, Melissitus ruthenica and Serratula yamatsutanna. A randomized block design experiment was conducted, with six blocks of five treatments each: N₀ (0 kg N·ha^-1), N₃₀ (30 kg N·ha^-1), N₅₀ (50 kg N·ha^-1), N₁₀₀ (100 kg N·ha^-1) and N₁₅₀ (150 kg N·ha^-1). The results showed that there were significant differences in leaf C, N and P contents and in the stoichiometric characteristics of the six species under natural conditions. Pocockia ruthenica had the highest leaf C, N, and P contents and leaf N∶P, while S. baicalensis had the lowest leaf N and P contents and F. sibiricum had the lowest leaf C content. Leaf C contents did not respond to nitrogen addition in all the six plant species. Leaf N contents, leaf C∶P and leaf N∶P significantly increased but leaf P contents and leaf C∶N decreased with nitrogen addition in five of the species, other than M. ruthenica, which did not respond to nitrogen addition. Soil organic carbon and soil N∶P increased significantly, while soil total nitrogen and soil C∶N showed no significant responses to nitrogen addition. The individual leaf N contents of L. chinensis, A. sibiricum, F. sibiricum and S. yamatsutanna were positively correlated with soil organic carbon and soil N∶P. The leaf N∶P of S. baicalensis, L. chinensis, A. sibiricum and S. yamatsutanna were positively correlated with soil organic carbon and soil N∶P. In conclusion, soil organic carbon, soil N∶P and soil C∶P were the main factors that affected leaf C, N, P contents and the C∶N∶P ecological stoichiometric characteristics of the six plant species, but different species had different responses to nitrogen addition, meaning that long-term nitrogen addition may change the structure of the S. baicalensis grassland ecosystem.