A STANDARD VOLUME YIELDING MODEL OF CHINESE FIR USED FOR SITE QUALITY EVALUATION

A standard volume yielding model was established on the basis of an analysis of the data of growth process of 25 Chinese Fir stands in 5 forest farms in Nanling Mountain Area, Hunan and Guangdong Provinces. The model was used to prove that the rule of stem number changing with the mean diameter of the stand in original growth process table is reliable. Based on this, through adopting the method of standardizing the stem numbers, all the volume data of different plots in the growth process table, after eliminating the influence brought by thinning, were changed into standard level (canopy density=1.0). Then, analyzed by an improved 8 parameters Richards function and Marquardt iteration, a polymorphic standard yielding model, which took site index and age as the interpreting variables, was established. All the related properties of the model were discussed and the result was satisfactory. It supplies a foundation for site quality evaluation using index of volume