Study On Belowground Competition In Alley Silvopasture Systems Of Caragana

The alley silvopasture systems of Caragana exist widely in the Northwesten of China, as a common model of biological measures in the Grain for Green, anti-desertification and rangeland shelterbelts projects. The ecological and economic benefits of the alley silvopasture systems of Caragana with different belt distance are not famous, due to without scientific basis. This objectives of this thesis were to investigate the difference of belowground competition between Caragana and local plants in the alley silvopasture systems of Caragana with 4 m,6 m,8 m,10 m and 12 m belt distance, by analysing thevegetable distribution (quadrat sampling method), fine root spatial distribution of Caragana (excavation and auger methods), soil moisture in dry season and nutritious status of soil (soil auger method), and the allelopathy of Caragana aqueous extract from current year branches and leaves (est of seed germination), for improving the ecological and economic benefits, and management level of systems.The results are as follows:(1)The overground biomass of Caragana and vegetable, vegetation coverage, the species of plants and forage plants, Simpson indices and Margalef indices, are increased as belt distance of systems increasing. And the first dominant plants in 8 rn,10 m and 12 m systems are higher quality for feeding than in 4 m and 6 m systems.(2)Caragana fine root in 0-40 cm soil and in central soil, decreased as belt distance of systems increasing. Consequently, belowground competition between Caragana and herbage, and intraspecies competition of Caragana, were more mitigative in 8 m system, than in other systems. The FRSAD of Caragana is not influenced by seasons and it is decreased in central soil and 0-40 cm soil layer as the belt distanceof systems increasing in 4 m,6 m,8 m and 10 m systems. In 12 m system, there are little belowground competition between Caragana and herbage, because of fewer fine roots of Caragana in topsoil and central soil than that in other systems.(3) The soil moisture is extremely low in 0-20 cm soil layer of any systems, and lower significantly in 20 cm-80 cm soil layer of 4 m,6m and 8 m systems than in 10 m and 12 m systems. The soil moisture is varied slightly on the vertical profile of 4 m,6 m and 8 m systems. The soil nutrient content in 10 m and 12 m systems, are higer than 4 m,6 m and 8 m systems, which are directly and indirectly promoting the growth of plants respectively.(4) High concentration (20 g-mL-1) Caragana aqueous extract from current year branches and leaves can suppress the germination rate, germination potentiality and germination index of seeds significantly. The allelochemicals suppress the germination potentiality and germination index of seeds seriouser than germination rate.Consequently, there are lower coverage of shrub, water consumption and allelopathic negative effect in 10m and 12 m systems, than 4m,6m and 8m systems, and still can prevent soil erosion by wind during winter and spring effectively,. It suggests that Caragana alley silvopasture system with 10 m-12 m belt distance is comparatively feasible, in Yanchi county and other areas in the semi-arid areas of the northwestern China.