Effects of soil in larch plantations on the growth of Picea koraiensis and P. crassifolia seedlings.

In addition to soil fertility decline, larch plantation had difficulty in natural regeneration, which challenges the healthy development and sustainable management. A greenhouse experiment was conducted with two kinds of shade-tolerant conifer species (Picea koraiensis and P. crassifolia) to examine the responses of seedling growth of two spruce species on sterilization treatment of larch plantation soils (except spruce biological characteristics), which would provide scientific basis for the transformation, regeneration and multi-storied forest cultivation of larch. The results showed that soil sterilization did not significantly affect the biomass of P. koraiensis and P. crassifolia seedlings. The biomass of P. koraiensis (75.6 and 72.2 mg, respectively) was significantly higher than that of P. crassifolia (55.6 and 60.0 mg, respectively) in both unsterilized and sterilized soils. The root diameter, cortical thickness, stele diameter and stele to root diameter ratio of the first-order roots of P. koraiensis were not affected by soil sterilization. In contrast, the root diameter, stele diameter and stele to root diameter ratio of the first-order roots except cortical thickness of P. crassifolia in sterilized soil (331.30 μm, 143.23 μm and 43.3%, respectively) were significantly higher than those in unsterilized soil (276.50 μm, 99.35 μm and 36.0%), showing a more positive response to sterilized soil. It indicated that P. koraiensis had better adaptability in larch plantation. Because the microbial community function was dominated by ectomycorrhiza which displayed some antagonisms for soil pathogen, seedlings of two spruce species could escape from soil pathogens accumulated in larch plantation and grow normally, with P. koraiensis having more advantages than the P. crassifolia.