Abstract: [Objective] The population stability of Hippophae rhamniodes ssp. sinensis depends on clonal growth ability and also on levels of environmental resources. However, the effects of the planting density are not well illustrated. This study aims to determine the optimal planting density according to the clonal growth response to the planting density and the regulation mechanism of the biomass allocation.[Method] Four planting densities, namely 2 500, 4 444, 10 000, and 40 000 plants·hm^-2 were applied. The ramet growth ability was measured for each tally tree. The clonal propagation ability was obtained by counting the daughter ramets. The clonal expansion capability was quantified by tracking the clones. Aboveground biomass was estimated from the average standard trees. The vertical and horizontal root biomasses were determined by weighting all the roots in the grid quadrats and tracked, respectively.[Result] The basal stem diameter and crown growth of the ramets showed logarithmic decreases with increasing planting density, while the height growth was independent of the density. The clonal propagation and expansion abilities showed parabola profiles, with synergistic effect between them. The biomass was allocated more to the belowground and less to the aboveground. The biomass allocation of horizontal roots showed a parabola. The growth ability of the ramets was positively correlated with the aboveground biomass allocation, and the clonal propagation and expansion abilities were positively correlated with the biomass allocation of the horizontal roots.[Conclusion] The population is traded-off in the biomass allocation between the above-and the below-ground and between the vertical and horizontal roots, and between ramet growth and the clonal propagation and expansion, by which forms individual shape and clonal growth configuration to adapt planting dnesity. With the increase of initial planting density, the ramet morphology changes from thick to medium and to slender, and the clonal propagation and expansion abilities did as a low-high-low pattern. That is to say, the clonal growth configuration went as a guerrilla-aggregation-guerrilla pattern, and the population stability exhibit a low-high-low changing process. According to this study, the suitable initial planting density is about 15 000 to 20 000 plants·hm^-2, which is most conducive to the clonal growth and the population stability maintenance.

Key words: clonal propagation, clonal expansion, biomass allocation, initial planting density, Hippophae rhamniodes ssp. sinensis, Mu Us sandy land