Abstract: This paper, taking Chinese Fir & Masson's pine as examples (objects), studied the site quality evaluation by the substitution of tree species in the same site types. The result showed that directly adopting site index to establish substitution equation pairs, because different species make different responses to the site types and its comprehensive functions, can't get correct result. However, through the way of quantification and multi-variate analysis, we can develop site index substitution model on the basis of site factors and transform the index value into standard growing stock. Thereby, it is on the basis of ecology that the question of site quality evaluation through multi-species substitution has been solved with satisfaction.

Key words: Site quality evaluation, Species substitution evaluation, Rechards function, Marquardt iteration