Polymorphic Site Index Cure Model And Variable Growth Intercept Model For Larix Principis-rupperechtii Stands In Guandi Mountain Forest Zones

This research tended to conduct stem analysis data on 150 dominant and co-dominant trees selected from 40 plots of Larix principis-rupperechtii natural and planted stands in Guandi Mountain forest zones. Using the nonlinear regression equation based on site index, a polymorphic site index cure model, a site index prediction model and a variable growth intercept model were constructed together with the polymorphic site index cure and table. We also compared the height growth between planted and natural stands and analyzed the relationship between the age reaching breast height and stand conditions. The results showed:(1) The site index standard age of Larix principis-rupperechtii stands in this zone is breast-height age of 40 years. (2) The pattern of height growth is statistically similar between planted and natural stands once Larix principis-rupperechtii trees have overcome competition from understory plants. (3)The age of Larix principis-rupperechtii reaching breast height was not closely related to stand conditions, we should be used the breast-height age instead of the total age to avoid potential errors associated with early erratic height growth below breast height. (4) The above mentioned models had high accuracy and could be used to evaluate the site quality and predict the height growth of Larix principis-rupperechtii stands in Guandi Mountain forest zone. (5) The variable growth intercept site index model had more accurate evaluating the site quality with breast-height age below the site index standard age.