Abstract: The spatial distribution of fine roots from different species in a fruit treecrop intercropping system determines their competitive ability to soil moisture and nutrients. The spatial variation of fine roots reflects the adaptive strategy of the components of intercropping systems to belowground resources. The degree of niche overlap of fine roots reflects the competitive relationship due to the overlap of niches. A stratified excavation method was used to examine the spatial distribution variation and belowground competition of fine roots of applecrop intercropping systems in the western Shanxi Province of China. The results showed that the fine root biomass of apple trees was concentrated in the area of 0.5-1.3 m from the apple tree row, while that of soybean increased with increasing distance from the apple tree. The fine roots of apple trees were mostly distributed within the 20-40 cm soil depth, while that of soybean were distributed within the topsoil tillage layer of 0-20 cm. Compared with the monocropping systems, the intercropping system not only inhibited the growth of fine roots of both species, but also promoted the distribution of fine roots of apple trees to deep soil and the fine roots of soybean to the upper soil, respectively. The competitive ability of soybeans was stronger than that of apple trees in the area of 0.5-2.1 m from the apple tree row. The competition effect of soybeans on apple trees was dominant in the 0-20 cm soil depth, while the competition effect of apple trees on soybeans in the 20-100 cm soil depth. With increases of the distance from apple tree row, the competition intensity of applesoybean intercropping system gradually weakened, with the intense competition occurring in the area of 0.5-1.3 m from the apple tree row. Our results provide scientific basis for the regulation of interspecific relationships and sustainable management of the apple soybeanintercropping system.

Key words: Phytoplankton, Species diversity, Cell abundance, Jiaozhou Bay