Abstract: The roots of individual seabuckthorn plant grown in loess remaining plateau and gully region plantation have been studied systematically in this paper. The results show. (1) The age of the main root is the critical factor for the fuzzy cluster among individual plants. The roots at juvanile ages are clustered easily, and it is more difficult to cluster with the increase in the age of main root because of the differences in the roots of the same age individual plants. (2) Changes in root biomass and length of individual seabuckthorn plant have been described and forecasted by the grey Verhaulst model. The roots stop growing when the main roots are about at the age of 17. (3) The vertical distribution laws of root biomass and length in soil are in binary curve function, the goodness of fit between real data and calculated values is perfect. (4) The dense layers of seabackthorn roots increase in deepth with the main root ages and become stable at about 0-50cm finally. The large diameter roots are mostly in this layer. The linear regression equation between root biomass and leaf biomass of seabuckthorn has been established in this paper.

Key words: Fuzzy cluster, Growth model, Distribution law, Dense layer, Roots, Forecast