Background Soil carbon (C), nitrogen (N) and phosphorus (P) play a key role in plant growth regulation and nutrient cycling. Studying forest C, N and P storage is of great significance for in-depth understanding of forest ecosystem functions and sustainable management. Pinus sylvestris var. mongolica is a practical tree species for desertification combating, and soil and water conservation in northern China. Due to the different introduced regions and years, there may be differences in C, N and P storage of P. sylvestris var. mongolica plantations. To reveal the effects of introduced region and stand age on C, N and P storage in P. sylvestris var. mongolica plantations.

Methods Field investigation and sample collection were conducted in different age groups (middle-aged, near-mature and mature) plantations in the Hulunbuir, Horqin and Mu Us Sandy Land. Soil samples from were collected in 0-20 and 20-40 cm layers, and the C, N and P contents and storage were measured. The difference of C, N and P storage in different regions with different ages were analyzed by ANOVA, and their correlations with environmental factors were also clarified by Person correlation analysis.

Results 1) C, N and P storage of P. sylvestris var. mongolica plantations were 1.78-34.38, 0.33-2.09, and 0.48-1.83 kg/m², respectively. 2) The introduced region had a significant impact on C, N and P storages (P < 0.05) and the stand age had a significant impact on C and N storage (P < 0.05) With increasing stand age, C storage first increased and then decreased, N storage increased. 3) C and N storage were positively correlated with soil porosity, invertase and phosphatase activity, and negatively correlated with average precipitation, soil pH and temperature. A significant negative correlation was obtained between N and P storage (P < 0.05), and they both had the strongest correlation with soil porosity. The correlation between P storage and environmental factors was opposite to that of N storage.

Conculsions C and N storage of P. sylvestris var. mongolica plantations are significantly affected by the introduced region and stand age, while P storage is greatly affected by the introduced region and nitrogen storage. P is the important limiting factor for the growth of P. sylvestris var. mongolica plantations on sandy land. It is recommended that the regional environmental differences should be considered in management of P. sylvestris var. mongolica plantation, phosphate fertilizers can be applied appropriately and we should pay attention to the management and protection of mature forests. This improved information provides a theoretical basis for the sustainable management of P. sylvestris plantation.