羌塘高原高寒草地植物地上地下碳氮生态化学计量特征及其影响因素

Carbon:nitrogen ecological stoichiometry of the alpine steppe between the aboveground and belowground parts of plants and relevant impact factors in the Qiangtang Plateau

研究高寒草地的植物生态化学计量特征对认识极端气候背景下的草地生态系统功能与服务具有重要的意义. 选择羌塘高原高寒草地作为研究区，分析东西走向60个样点植物地上、地下部分的碳（C）、氮（N）含量与C：N的分布特征，及其各自的主要驱动因素. 结果表明：高寒草地植物地上部分C、N含量（38.22%、1.82%）均高于地下部分（31.11%、1.15%），但C：N（22.08）却小于地下部分（28.88），且地上部分C含量、C：N与地下部分存在显著性差异（P 〈 0.05）. 干燥指数与植物地上部分C含量（R^2 = 0.072，P 〈 0.05）以及C：N（R^2 = 0.15，P 〈 0.005）呈负相关关系，却与植物地下部分C：N（R^2 = 0.53，P 〈 0.001）呈正相关关系；此外，年均降水量（R^2 = 0.13，P 〈 0.005）与地上部分C含量呈负相关关系，总生物量（R^2 = 0.13，P 〈 0.01）及植被总盖度（R^2 = 0.12， P 〈 0.01）与地下部分C含量呈正相关关系；海拔与地上部分C：N亦呈正相关关系（R 2= 0.15，P 〈 0.005），而年均温却与地下部分C：N呈负相关关系（R^2 = 0.31，P 〈 0.001）. 可见，水热条件是影响羌塘高原植物地上、地下C含量以及C：N差异的主要因素，而干燥指数可以作为较好的度量指标. （图7 表1 参46）

It is critical to explore the functions and services of alpine grassland ecosystems by investigating the aboveground and belowground ecological stoichiometry of plants in the alpine steppe. We thereby conducted an experiment to evaluate the ecological stoichiometry of carbon （C）, nitrogen （N）, and the ratio of C to N （C：N） in the alpine steppe with 60 aboveground and belowground plant samples along the East-West zone in the Qiangtang Plateau. The results showed that the aboveground C and N contents （38.22%, 1.82%） of plants were higher than those belowground （31.11%, 1.15%）. However, the aboveground C：N （22.08） of plants was less than that belowground （28.88）. There was a significant difference in C content aboveground and belowground. Moreover, the C：N also presented a significant difference between the aboveground and belowground parts of plants （P 〈 0.05）. The aridity index exhibited a negative correlation with the C content （R^2 = 0.072, P 〈 0.05） and C：N （R^2 = 0.15, P 〈 0.005） in the aboveground parts of plants. However, there was a positive correlation between the aridity index and C：N （R^2 = 0.53, P〈0.001） in the belowground parts of plants. In addition, the C content negatively correlated with the average annual precipitation （R^2 = 0.13, P 〈 0.005）, but positively with the total biomass （R^2 = 0.13, P 〈 0.01） and total coverage （R^2 = 0.12, P 〈 0.01） in the aboveground parts of plants. The C：N exhibited a positive correlation with altitude （R^2 = 0.15, P 〈 0.005）, but a negative correlation with the average annual temperature （R^2 = 0.31, P 〈 0.001） in the belowground parts of plants. Precipitation and temperature were the two major impact factors, together they can lead to differences in C content and C：N in the aboveground and belowground parts of plants. The aridity index can be an effective indicator to interpret this process and its mechanism.