藏北高寒草地植物群落C、N化学计量特征及其影响因素

Carbon and nitrogen stoichiometry of plant community and its influencing factors in a northern Tibet alpine grassland

碳(C)、氮(N)作为植物必需的养分元素,其二者间的相互作用以及其与生境的关系影响着植物生长发育和营养状况,反映了植物的生长速率。研究藏北高寒草地58个样点植物C、N化学计量特征及植物C、N含量和C∶N与环境因子的关系。结果表明:(1)高寒草地植物的C、N耦合关系存在差异,可分为高碳氮比植物(lg(C)/lg(N)=0.926)和低碳氮比植物(lg(C)/(lg(N)=0.105);(2)藏北地区高寒草地植物C含量为382.24 mg·g-1、N含量为17.76 mg·g-1,植物C∶N平均值为22.24,且N的变异系数>C∶N的变异系数>C的变异系数;(3)高碳氮比情况下,主要环境因子对植物碳、氮及碳比氮分布变化的解释量:土壤有机碳(SOC)(48.91%)>土壤全氮(STN)(30.50%)>温度(27.47%)>降水(16.66%);低碳氮比情况下,环境因子对植物碳、氮及碳氮比分布变化的解释变量:降水(18.78%)>经度(16.32%)>干旱指数(14.35%)>植物物种丰富度(12.58%);(4)对于高碳氮比的植物,植物C、N含量随着SOC含量的增加而降低(P<0.05),植物C∶N受环境因素影响不显著;而对于低碳氮比的植物,植物C含量和C∶N值与降雨、经度、干燥度和植物物种丰富度均呈负相关关系。研究结果对于高寒草地的可持续利用及生态保育与恢复提供了理论依据。

Both carbon （C） and nitrogen （N） are essential nutrients for plants. Their interaction and relationships with habitats influence growth, development, and nutrition status of plants. C∶N ratio of vegetation reflects growth rate of plants. Plant C and N concentrations, C∶N ratios and their relationships with environmental factors were analyzed based on the investigation of 58 sampling sites in a northern Tibet alpine grassland. The results showed that： （1） The coupling relationships between plant C and N varied in the alpine grassland. Plants could be divided into two groups： one with higher C∶N and another with lower C∶N. （2） The mean values of plant C concentration, N concentration and C∶N ratio in northern Tibet were 382.64 mg·g-1, 17.76 mg·g-1 and 22.24, respectively, with coefficients of variation （CV） in order of N concentration 〉 C∶N ratio 〉 C concentration. （3） For the plants with high C∶N ratio, different environmental factors explained by variance to plant C concentration, N concentration and C∶N ratio were in order of soil organic carbon （SOC） （48.91%） 〉 soil total nitrogen （STN） （30.50%） 〉 temperature （27.47%） 〉 precipitation （16.66%）. For plants with low C∶N ratio, the explanation variance was in order of precipitation （18.78%） 〉 longitude （16.32%） 〉 aridity index （AI, 14.35%） 〉 plant species richness （12.58%）. （4） For plants with high C∶N ratio, SOC concentration was negatively correlated with plant C and N concentration, and C∶N ratio was not significantly affected by other environmental factors. In contrast, for plants with low C∶N ratio, precipitation, longitude, AI and richness had significant negative effects on plant C concentration and C∶N ratio. This study provided scientific basis for sustainable utilization and ecological conservation and restoration of alpine grasslands in northern Tibet.