Abstract: Trunk is the main organ for storing non-structural carbohydrate (NSC) in trees. NSC allocation patterns in trunk can reflect carbon storage strategy and adaptability of trees. We measured the concentrations of soluble sugar, starch and NSC in trunks of three main afforestation conifer species (Pinus sylvestris var. mongolica, P. densiflora, and P. tabuliformis) in Horqin Sandy Land, the radial and vertical variations in trunks, and compared the interspecific variations in allocation patterns. The results showed that, at the middle and base of crown heights of trunks, concentrations of soluble sugar and NSC of the three species decreased with increasing radial depth. At breast and stump heights of trunks, soluble sugar concentrations and the ratios of sugar to starch gradually decreased, starch concentrations gradually increased, and NSC concentrations remained unchanged with increasing radial depth. NSC concentrations were higher at the middle of crown height than  at crown base, breast and stump heights of P. sylvestris var. mongolica, while they were higher at the middle and base of crown heights than at breast and stump heights of P. densiflora. There were no differences in NSC concentrations at different heights of trunks of P. tabuliformis. NSC concentrations in trunks of P. densiflora were higher than those of P. sylvestris var. mongolica and P. tabuliformis. Therefore, trunk is important pool for starch reserves for all the three conifer species, which is conducive to adapt to the environment of Horqin Sandy Land. The trunks of P. densiflora stored more carbohydrates, which may facilitate its resistance to adverse environments.

Key words: Pinus sylvestris var. mongolica, Pinus densiflora, Pinus tabuliformis, radial variation, vertical variation, carbohydrate reserve, interspecific comparison.