Objective Understanding the allocation and cycling characteristics of the main nutrients in the process of artificial vegetation restoration on sandy land will help us fully understand the strategies of plant adaptation to the desert ecosystems, and provide theory for the vegetation management.

Method This study was conducted in the shrub plantations of Caragana intermedia with different stand age of 6-, 9-, 11-, 17- and 31-year-old on alpine sandy land. The whole plant of average shrubs was completely harvested for analysing the main nutrients N, P and K concentration, accumulation, allocation and cycling characteristics.

Result (1) In components, leaves and stem bark with the highest nutrient content, and stem wood with the lowest nutrient content. As the plantation age increased, N content in three root-diameter (coarse root: diameter > 5 mm, medium root: 2 mm < diameter ≤ 5 mm, fine root: diameter ≤ 2 mm) and P content in leaves increased significantly, whereas P and K contents in fine root, K contents in branches and medium root decreased significantly. The N contents of three root-diameters had a significant negative correlation with the P and K contents of fine root, and the N contents of medium and fine root had a significant negative correlation with the K contents of branches and medium root. (2) The nutrient accumulation of root was higher than aboveground components. The percentage of the nutrient accumulation of the root to the aboveground components firstly increased and then decreased as the plantation age increased. It peaked in 17-year-old plantation, and the percentage of N, P and K were 70%, 66% and 63%, respectively. (3) As the plantation age increased, the utilization coefficient of the nutrients decreased, while the recycling period and cycling coefficient increased. Utilization coefficient and cycling coefficient of K were higher and recycling period was shorter than N and P in all plantations.

Conclusion With the development of C. intermediate plantation on alpine sandy land, more nutrients were allocated to the root system to adapt to the harsh environment. The nitrogen fixation process of C. intermediate will consume its own K and P, of which K with fast circulation rate and high mobility. Therefore, we suggested that K and P fertilizer should be added in the management and protection of C. intermedia shrub plantation.