Root distribution characteristics of monoculture and mixture of and plantation.

In this study, we analyzed the vertical distribution characteristics of root biomass density, root length density, root surface area density in monoculture and mixture of and plantations in Caijiachuan small watershed of Jixian County, Shanxi. We examined their relationships with soil physical and chemical properties in different stand types. The results showed that the total root biomass density of and in mixture was more than 75% higher than that in monoculture. Root system of mainly distributed in shallow layer (0-40 cm), while that of was deeper (40-80 cm). Fine roots were predominant in different diameter classes. Length density and surface area density of fine roots were in the order of in mixture > in mixture > stand > stand. Root biomass density of fine roots was in the order of in mixture ＞ in mixture ＞ stand ＞ stand. In vertical profile, the total root and fine root biomass, root length and root surface area density of stand, stand, in mixture and in mixture showed a rule of decreasing with the increases of soil depth. Under different stand types, fine root length density, root biomass density and total root length density were positively correlated with soil total nitrogen, soil organic carbon, and soil water contents. Total root surface area density was significantly positively correlated with soil organic carbon, soil water content, and soil total nitrogen. The distribution of roots in pure and mixed stands of and showed different patterns. Compared with the pure stand, the mixed stand had higher root biomass, soil nutrient contents, and soil water content.