Abstract:

Our objectives were to investigate fine root spatial distribution of Caragana spp. in three alley silvopasture systems which are composed of one shrub belt and two-rows with different belt distance(4, 6, 8 m). The three systems had intact structure and uniform growth status in similar sites. The roots were sampled by the way of excavation from one soil layer to another vertically, on the woodland soil profile. The results showed that root biomass(RB)of Caragana spp. concentrated near the shrubs, Caragana spp. root biomass density(RBD)of 4 m system was markedly greater than that of 6 m and 8 m systems in central soil of woodland. The results also showed that, Caragana spp. fine root length density(FRLD)and fine root surface area density (FRSAD) in whole woodland of 4 m system were greater than that in 6 m and 8 m systems. In the three systems, average FRLD and FRSAD, cumulate percents of fine root length and surface area in 0-40 cm soil, FRLD and FRSAD in central soil, all decreased as belt distance of systems increasing. In 8 m system, root concentrated layers were separated between Caragana spp. and herbaceous, and fewer Caragana spp. roots were superposed in central soil, because of fewer fine roots of Caragana spp. in topsoil and central soil than that in other systems. Consequently, interspecies competition between Caragana spp. and herbage, and intraspecies competition of Caragana spp, were more mitigative in 8 m system, than in other systems. It suggests that Caragana spp. alley silvopasture system with 8 m belt distance is comparatively feasible, in semi-arid areas of northwestern China.

Key words: silvopasture system, Caragana spp., fine root, root spatial distribution, competition