中文摘要：

在关帝山林区8个林场的油松天然林中选取69株优势木进行树干解析，应用XLSTEM和SYSTATE软件进行数据处理和分析，充分考虑达到胸高的年龄在立地指数模型中的意义，确定油松天然林立地指数基准年龄，引入生长截距和可变生长截距的概念，分析林分优势木达到胸高的年龄与立地条件的关系，建立关帝山林区油松天然林立地指数的可变生长截距模型。结果表明：1）研究地区油松天然林立地指数基准年龄可确定为胸高年龄35年，实际总年龄约为42～45年；2）油松天然林达到胸高的年龄与立地条件的关系不密切；3）本研究建立的油松天然林可变生长截距模型准确、可靠，能对胸高年龄为3～35年的油松天然林进行准确地立地质量评价。

英文摘要：

Sixty-nine plus-trees were selected from naturally regenerated Pinus tabulaeformis stands in Guandi Mountain Forest Zone for stem analyses. The collected data were processed and analyzed with XLSTEM and SYSTAT. The reference age of site index for Chinese pine was established integrating the application of a tree＇ s age when reaching breast height in a stand index model. By analyzing relationship between the age reaching breast height and stand conditions, growth intercept and variable growth intercept, were used to construct a variable growth intercept model. The authors conclude that： 1 ） The reference age of site index for naturally regenerated Chinese pine in this area is 35 years when reaching breast height, with actual ages ranging from 42 to 45 years; 2） The age of Chinese pine reaching breast height is not correlated with stand conditions; 3） The variable growth intercept model for naturally regenerated Chinese pine stands can be used to accurately and reliably evaluate the sit qualities of Chinese pine forest, which ages are from 3 to 35 years when reaching breast height.