中文摘要：

为探讨半干旱区树木各器官中养分浓度的分配格局、养分之间的化学计量关系,以及植物器官养分浓度与树种、土壤养分条件之间的关系,选取内蒙古东南缘的两种天然的典型树种（白桦和白杄）,对其叶片、树干、基部最粗根以及根尖中的总非结构性碳水化合物（TNC）、氮（N）和磷（P）浓度进行分析。结果表明：TNC浓度在叶片中最高,在根尖中最低,两者的浓度差异在53%以内;而N和P浓度在叶片和根尖中最高,树干和基部最粗根中最低,不同器官最大差异达98%。这种分配格局与各器官的生理功能（碳水化合物的生产、养分的吸收和储藏）密切相关。此外,白杄的TNC∶N和TNC∶P均大于白桦,这些格局不仅和树种本身的生理特性有关,而且反应了土壤的养分状况。

英文摘要：

To examine patterns of nutrient concentrations in different organs, stoichiometry of various nutrients, and the relation of nutrient concentrations with species and the environment, the concentrations of total non-structural carbohydrate （TNC）, nitrogen （N）, and phosphorus （P） among leaves, stems, tap roots, and first order roots in Asian white birch （Betulaplatyphylla） and Meyer spruce （ Picea meyeri） were studied. The two species were located in the southeastern edge of Inner Mongolia. For TNC, leaves had the highest and first order roots had the lowest concentrations ; the largest difference between them was less than 53%. For N and P, however, there were much higher concentrations in leaves and first order roots than that in stems and the tap roots; the largest difference between them was about 98%. These patterns were determined by the physiological roles （carbohydrate production, nutrient uptake and storage, etc. ） that different organs play. In addition, both TNC ： N and TNC ： P of Meyer spruce were higher than those of Asian whiter birch, reflecting the physiology of different species and variations in soil nutrient conditions.