Abstract: To reveal the main factors limiting the growth of Salix psammophila and provide a scientific basis for the sustainable and efficient development of the Three-North Shelter Forest, we examined the variations of the C, N, P, and K contents and stoichiometric ratios in leaf and new branch under non-stubble, single-row interlaced stubble and full stubble treatments in the declining S. psammophila plantations on alpine sandy land of Gonghe Basin, Qinghai Province, and analyzed their relationships with soil nutrients. The results showed that the C, N, P and K contents in leaf and branch of two stubble plantations were significantly higher than non-stubble plantation (P<0.05). Leaf C∶N in singlerow interlaced stubble plantation was significantly higher than that of other plantations (P<0.05), while the C assimilation capacity and N use efficiency were improved. Compared with nonstubble plantation, the C∶P and C∶K in leaf and new branch of the two stubble plantations were significantly decreased, indicating that the stubble measures enhanced the P and K uptake capacity of S. psammophila. For non-stubble, single-row interlaced stubble and full stubble plantations, leaf N∶P was 19.11, 15.07 and 15.94, leaf N∶K was 1.18, 0.74 and 0.86, and leaf P∶K was 0.06, 0.05 and 0.05, respectively, which indicated that the growth of non-stubble plantation was limited by P, and the growth of two stubble plantations were co-limited by N and P. Soil available phosphorus (AP) content increased in stubble plantations. The soil AP content was the main influencing factor of the C, N, P and K contents and their stoichiometric ratios in leaf and branch, with the explanatory degree of 71% and 50%, respectively. In conclusion, the growth of S. psammophila plantations in this region is mainly limited by P element. P fertilizer should be applied appropriately in plantation management. Single-row interlaced stubble measure should be adopted for the restoration of the declining S. psammophila plantations, and P and N fertilizers should be applied simultaneously.

Key words: alpine sandy land, Salix psammophila plantation, stubble, nutrient element, stoichiometric ratio