Abstract: We analyzed C, N, and P stoichiometry of different plant organs, needle litter and soils in Pinus sylvestris var. mongolica and Pinus densiflora plantations, aiming to explore their nutrient conservation and use mechanisms. The results showed that C concentrations, C∶N, C∶P and N∶P in needles, N concentrations in branches, and N and P concentrations in roots of P. sylvestris var. mongolicawere significantly higher than those of P. densiflora, while P concentrations in needles, branch C∶N, and C concentrations, C∶N and C∶P in roots of P. sylvestris var. mongolica were significantly lower than those of P. densiflora. Concentrations of N and P decreased with increasing age of needle and branch for P. sylvestris var. mongolica, whereas P concentrations were significantly greater in current-year and two-year-old than one-year-old needles and branches for P. densiflora. Concentrations of C, N and P in needle litter of P. sylvestris var. mongolica were significantly higher than those of P. densiflora, while needle litter C∶P and N∶P of P. sylvestris var. mongolica were significantly lower than those of P. densiflora. P resorption efficiency of P. densiflora was significantly greater than that of P. sylvestris var. mongolica. P resorption efficiency was significantly higher than N resorption efficiency for both species. Soil P concentrations were significantly greater in P. sylvestris var. mongolica plantation than in P. tabuliformis plantation, whereas soil C∶N and C∶P were significantly lower in P. sylvestris var. mongolica plantation than in P. densiflora plantation. These results indicated that P. sylvestris var. mongolica tended to allocate more nutrients to newborn tissues, with declining nutrient conservation ability of old branches and needles. The needle litter was easy to decompose, which was not conducive to soil nutrient conservation, and soil P concentrations were low in P. sylvestris var. mongolica plantation. P. densiflora maintained higher nutrient resorption efficiency, and improved the nutrient use efficiency, which exhibited a stronger ability to conserve nutrients and reduced soil P consumption.

Key words: nutrient limitation, organ diversity, nutrient resorption, tree species selection, Horqin sandy land.