氮肥添加对青藏高原高寒草甸6个群落优势种生态化学计量学特征的影响

Effects of N addition on ecological stoichiometric characteristics in six dominant plant species of alpine meadow on the Qinghai-Xizang Plateau, China

以青藏高原高寒草甸为研究对象,通过人工氮肥添加试验,研究6个群落优势种在不同施氮(N)水平下叶片碳(C)、N、磷(P)元素含量的变化以及生态化学计量学特征。结果表明:自然条件下,6个物种叶片N、P质量浓度存在显著的差异,表现为:黄花棘豆(Oxytropis ochrocephala)最高,为24.5和2.51 g·kg–1,其叶片N含量低于而P含量高于我国其他草地的豆科植物;其余5个物种叶片N、P质量浓度分别为11.5–18.1和1.49–1.72 g·kg–1,嵩草(Kobresia myosuroides)叶片N含量最低,垂穗披碱草(Elymus nutans)叶片P含量最低,与我国其他区域的研究结果相比,其叶片N和P含量均低于我国其他草地非豆科植物。随氮素添加量的增大,6种群落优势种叶片的C和P含量保持不变;其他5种植物叶片N含量显著增加,黄花棘豆叶片N含量保持不变。未添加氮肥时,6种植物叶片N:P为7.3–11.2,说明该区植物生长更多地受N限制。随N添加量的增加,除黄花棘豆外,其他5种植物叶片N:P大于16,表现为植物生长受P限制。综合研究表明,青藏草原高寒草甸植物叶片N含量较低,植物受N影响显著,但不同物种对N的添加反应不同,豆科植物黄花棘豆叶片对N添加不敏感,其他5个物种叶片全N含量随着N添加量的升高而增加,该研究结果可为高寒草甸科学施肥提供理论依据。

Aims Our purpose was to characterize the effects of nitrogen （N） addition on plant carbon （C）, N, phosphorus （P）, and C：N：P ecological stoichiometric characteristics in six dominant plant species, including Kobresia myosuroides, Elymus nutans, Anemone rivularis, Pedicularis kansuensis, Potentilla fragarioides and Oxytropis ochrocephala, of alpine meadow on the Qinghai-Xizang Plateau, China. Methods N was added at four levels. Concentrations of C, N and P were measured, and C：N：P was estimated in the six plant species following the N addition treatments. lmportantfindings Significant differences in leafN and P concentrations existed among the six species under natural conditions. The N and P concentrations were highest in （9. ochrocephala, at 24.5 and 2.51 g.kg-1, respectively. The leaf N concentration was significantly lower and leaf P concentration was significantly higher in O. ochrocephala than in legume plants of other grasslands in China. Leaf N and P concentrations in the other five species were in the ranges of 11.5-18.1 and 1.49-1.72 g.kg-1, respectively. Kokresia myosuroides had the lowest N concentrations and E. nutans had the lowest P concentrations; they were significantly lower than the non-legume plants in other grasslands in China （p 〈 0.001）. P and C concentrations did not respond to N addition in all the six plant species, but N concentration significantly increased with N addition in five species other than O. ochrocephala, which did not respond to N addition. Values of the N：P varied in the range of 7.3-11.2 in treatment without N addition, indicating that the plant growth was limited by N in the alpine meadow. Values of the N：P increased and were greater than 16 with N addition in five species other than O. ochrocephala, indicating that N addition induced P deficiency in these five species. Our results point to very low leaf N concentration and limitation of N on plant growth in alpine meadow on the Qinghai-Xizang Plateau, China, but different species had different responses to N addition. The legume plant O. ochrocephala was not susceptible to N addition, but learN concentration in other five plant species was increased by N addition. Findings in this study highlight the importance for fertilization and management of alpine meadow.