摘要:In eastern area of Xiaoxing′an Mountains, Heilongjiang Province (44o′-47o26 N′, 126o33′-131o41′E) the diameter-class structure of Quercus mongolica forest after different closed time was studied in the plots with different slope direction. Six repetitive plots within 5-year, 16-year and 24-year closed Q. mongolica forests were selected in sunny slope and shade slope, respectively. The area of each plot was 20 m×20 m. Diameter at breast height (DBH), tree height and canopy diameter of all the trees were measured. Six classes of diameter were determined as 2, 4, 6, 8, 10, and 12 depending on the range of DBH (0-3, 3-5, 5-7, 7-9, 9-11, and 11-13 cm). The results showed that: 1) After 5-year closed treatment, the population quantities Q. mongolica, Tilia mandshurica and Ulmsis laciniata decreased with the increase in diameter class, which indicated they were healthy populations; 2) After 16- year closed treatment the tree number of Tilia mandshurica and Ulmsis laciniata decreased because of canopy coverage increasing and became the associated species in Q. mongolica population; 3) Q. mongolica, after 24-year closed treatment, became dominant species; 4) Canopy coverage increased more rapidly in sunny slope than that in shade slope. Recession of Tilia mandshurica and Ulmsis laciniata populations in sunny slope was more obviously than that in shade slope.%在黑龙江省小兴安岭东部地区(东经44o4′-47o26 N′,北纬26o33′-131o41′, 海拔400-1000 m), 对不同封育时间、不同坡向的蒙古栎林中的主要乔木树种径级结构进行分析。在阳坡,针对封育5年 16年和24年蒙古栎种群, 分别选择6个重复样地。在阴坡,也同样分别选择6块样地。每块样地的面积为20 m×20 m。在每块样地中, 测量各树的胸高直径,树高和冠幅直径。结果表明:在封育5年样地内,蒙古栎、糠椴和黄榆种群的数量均随着径级的增加而单调下降,表明均为增长型种群;在封育16年以后,由于林内乔木层的盖度较大,糠椴和黄榆种群均呈不同程度的衰退,已经成为蒙古栎种群的伴生种群;封育24年样地中,蒙古栎种群明显成为优势树种。在阳坡随封育时间延长乔木层盖度增长较快,而阴坡乔木层盖度增长较慢;糠椴和黄榆种群随封育时间延长逐步衰退的现象在阳坡比阴坡表现明显。