Polymorphic Site Index Model of Casuarinae quisetifolia Fast-growing Plantation A STUDY ON THE ESTABLISHMENT OF POLYMORPHIC SITE INDEX MODEL BY ADOPTING RICHARDS FUNCTION An Application of Linear Model to Testing the Universal Applicability of Site Index Curves for Chinese Fir Provenances The Impact of Chinese Fir Provenances on Site Index Curves Research on the Use of Dummy Variables Method to Calculate the Family of Site Index Curves Sloboda Height Growth Model and Its Application on Chinese Fir Plantation