Abstract: Root-root interactions were studied in green-house potted Manchurian ash (Fraxinus mandshurica) and Dahurian larch (Larix gmelinii) seedlings. Above and below ground growth of ash mixed was influenced significantly by the interaction with larch in mixture. The root system of ash was more sensitive to soil conditions than that of the larch, and its competitive effectiveness was enhanced by impoved nutrition. Relative to their mass in unmixed pots the fine and coarse root mass was increased by 47% and 46% respectively, and leaf and stem mass was increased about 30% and 48% respectively in mixed pots. Root-root interactions affected the root/shoot ratio, especially the fine root mass/leaf mass ratio, in ash. In contrast, biomass components and root/shoot ratio of larch showed no significant response in mixture. Through morphological adaptations ash altered its root distribution and morphology in mixture: fine root density and specific root length increased by 47 and 34% over pure planted pots. With relatively larger root mass and thinner root diameter, ash is a superior competitor for soil nutrients and moisture. Larch, on the other hand, is capable of improving soil conditions through its growth.

Key words: Fraxinus mandshurica, Larix gmelinii, Seedlings, Root systems, Competition