Abstract: We studied the fine root vertical distribution characters of Populus simonii, Ulmus pumila, Pinus tabulaeformis and Pinus sylvestris var. mongolica in Horqin sandy land, and discussed the relationships with soil water and organic matter. The distribution extinction coefficient of fine root was 0.968-0.979 for main afforestation tree species in Horqin sandy land. There was no significant difference in the total fine root biomass between the same age class tree species (P>0.05), while the value of P.sylvestris var. mongolica was significantly higher at 32 years old than that at the other age (P<0.05). The correlation of the fine root biomass was higher with soil water content than with soil organic matter content except 22-ear old P.sylvestris var. mongolica. There were significant positive linear correlations between the fine root biomass and soil water content for 10-, 22- and 42-year P.sylvestris var. mongolica, 44-year P.tabulaeformis, and 42-year U.pumila(P<0.05), but the relationships were significant negatively correlated for 32 years old P.sylvestris var. mongolica and 13 years old P.simonii(P<0.05). The fine root biomass vertical distribution was deeper for main afforestation tree species in Horqin sandy land with significant dependence on the soil water content.

Key words: fine root distribution, soil water content, shelterbelt decline, sandy land