Abstract:

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.

Key words: site quality evaluation, variable growth intercept model, growth intercept, natural Chinese pine stand, Guandi Mountain forest zone