在贺兰山西坡海拔1 848～2 707 m范围内选取典型植物群落的乔木、灌木和草本优势种，对不同生活型植物叶片C、N和P含量及比值进行比较，并对这些化学计量指标与14个环境因子的关系进行分析。结果表明：总体叶片C、N和P含量分别为431.58、15.66和1.79 mg·g^-1，C∶N、C∶P和N∶P分别为28.62、254.87和9.11。其中，乔木叶片C含量显著(P<0.05)高于灌木和草本，灌木叶片C∶N显著低于草本和乔木，其余化学计量指标在3个生活型间无显著(P>0.05)差异。随年均温升高，乔木叶片N∶P显著升高，灌木叶片C∶P和N∶P显著降低，草本叶片N含量和C∶N分别极显著(P<0.01)降低和升高；随年均降水量升高，灌木叶片N∶P显著升高，草本叶片N含量和C∶N分别极显著升高和降低。土壤含水量和土壤有机碳含量是影响乔木叶片化学计量指标变异的主要环境因子，其中，叶片N含量与土壤含水量以及叶片C∶P与土壤有机碳含量在0.05水平呈负相关，叶片P含量与2个环境因子均在0.05水平呈正相关，而叶片N∶P与2个环境因子分别在0.05和0.01水平呈负相关。土壤速效磷含量和土壤pH值是影响灌木叶片化学计量指标变异的主要环境因子，但仅叶片P含量与土壤速效磷含量在0.05水平呈正相关，叶片C∶P与土壤速效磷含量则在0.05水平呈负相关。土壤含水量、土壤硝态氮含量和土壤容重是影响草本叶片化学计量指标变异的主要环境因子，其中，叶片N含量与土壤含水量和土壤容重在0.001水平分别呈正相关和负相关，叶片C∶N与2个环境因子在0.001水平分别呈负相关和正相关，叶片C∶P与2个环境因子在0.05水平分别呈负相关和正相关，而叶片P含量与环境容重在0.05水平呈负相关。综上所述，贺兰山西坡乔木、灌木和草本植物生长均受N限制，灌木植物生长还受P限制。影响不同生活型植物叶片化学计量指标的环境因子不同，因此，在保护与恢复贺兰山西坡植被时，应针对不同生活型植物制定相应的措施。

Dominant species of arbor, shrub, and herb in typical plant community at elevation range of 1 848-2 707 m on the western slope of Helan Mountain were selected, leaf C, N, and P contents and ratios of different life form. plants were compared, and the correlations of these stoichiometric indexes with forteen environmental factors were analyzed. The results show that the overall leaf C, N, and P contents are 431.58, 15.66, and 1.79 mg·g^-1, respectively, and the C∶N, C∶P, and N∶P are 28.62, 254.87, and 9.11, respectively. In which, leaf C content of arbor is significantly (P<0.05) higher than that of shrub and herb, leaf C∶N of shrub is significantly lower than that of herb and arbor, and there is no significant (P>0.05) difference in the other stoichiometric indexes among the three life forms. With the increase of mean annual temperature, leaf N∶P of arbor significantly increases, leaf C∶P and N∶P of shrub significantly decrease, and leaf N content and C∶N of herb extremely significantly (P<0.01) decreases and increases, respectively; with the increase of mean annual precipitation, leaf N∶P of shrub significantly increases, and leaf N content and C∶N of herb extremely significantly increases and decreases, respectively. Soil water content and soil organic carbon content are the main environmental factors affecting variations of leaf stoichiometric indexes of arbor, in which, leaf N content with soil water content and leaf C∶P with soil organic carbon content show negative correlations at 0.05 level, and leaf P content shows positive correlations with the two environmental factors at 0.05 level, while leaf N∶P shows negative correlations with the two environmental factors at 0.05 and 0.01 levels, respectively. Soil available phosphorus content and soil pH value are the main environmental factors affecting variations of leaf stoichiometric indexes of shrub, but only leaf P content shows a positive correlation with soil available phosphorus content at 0.05 level, and leaf C∶P shows a negative correlation with soil available phosphorus content at 0.05 level. Soil water content, soil nitrate nitrogen content, and soil bulk density are the main environmental factors affecting variations of leaf stoichiometric indexes of herb, in which, leaf N content shows positive and negative correlations with soil water content and soil bulk density at 0.001 level, respectively, leaf C∶N shows negative and positive correlations with the two environmental factors at 0.001 level, respectively, leaf C∶P shows negative and positive correlations with the two environmental factors at 0.05 level, respectively, while leaf P content shows a negative correlation with soil bulk density at 0.05 level. In conclusion, the growth of arbor, shrub, and herb plants on the western slope of Helan Mountain is constrained by N, and the growth of shrub plants is also limited by P. The environmental factors affecting leaf stoichiometric indexes of different life form. plants are different, therefore, corresponding measures should be made for different life form. plants during the conservation and restoration of the vegetations on the western slope of Helan Mountain.