[Soil carbon, nitrogen and phosphorus stoichiometry characteristics of Pinus sylvestris var. mongolica belt-mixed forests.]

To provide theoretical basis for management of Pinus sylvestris var. mongolica mixed plantation, the variation of soil carbon, nitrogen and phosphorus stoichiometry in different P. sylvestris var. mongolica belt-mixed plantations were explored. Taking the monoculture plantation as control, soil samples were collected at the distance of 0, 1, 2, 3, and 4 m from the center point in P. sylvestris var. mongolica and Ulmus pumila mixed plantation and P. sylvestris var. mongolica and Maackia amurensis mixed plantation along the two directions of P. sylvestris var. mongolica and its associated species in different soil layers. Contents and stoichiometric ratios of soil organic C, total N, total P, available N, available P were analyzed. The results showed that soil organic C, total N, and available N in P. sylvestris var. mongolica mixed plantations were higher than those in pure plantation. The soil organic C, total N contents, C/N and C/P in deep soil layers were increased under P. sylvestris var. mongolica and U. pumila mixed plantation. The soil N content increased but P content decreased in P. sylvestris var. mongolica and M. amurensis mixed plantation. With the increases of distance from the center of mixed plantation, soil C/N firstly increased and then decreased, while soil total P and available P contents decreased and N/P increased in P. sylvestris var. mongolica belt. Soil C/N decreased and available P contents firstly increased and then decreased with the increases of distance from the center in U. pumila belt of P. sylvestris var. mongolica and U. pumila mixed plantation. Soil total N content firstly decreased and then increased in P. sylvestris var. mongolica belt, but it firstly increased and then decreased in M. amurensis belt of P. sylvestris var. mongolica and M. amurensis mixed plantation. P. sylvestris var. mongolica mixed plantation could improve soil C and N stocks compared with pure plantation. The best mixed mode was P. sylvestris var. mongolica and U. pumila mixed by one row, as well as P. sylvestris var. mongolica and M. amurensis mixed in two rows.