ObjectiveExploring the changes of soil nutrient conditions and the improvement role of broadleaved tree species to the soil nutrients of Picea koraiensis plantations aims to select the suitable mixed species and fertilization elements for the cultivation of Picea koraiensis plantations.

MethodWe collected the sample of leaf, litter and soil from Picea koraiensis plantations and natural forest in the sample plots, and used carbon nitrogen analyzer to determine the C content of the samples, used Kjeldahl instrument to determine the N content of leaves and litter samples, used the continuous flow analyzer to determine the N content of the soil samples, and used sulfuric acid-perchloric acid digestion-molybdenum antimony colorimetry to determine the P content of the samples.

Result(1) The difference of C content, N content and P content in the soil of four plantation types was significant, pure Picea koraiensis plantation was lower than three mixed plantations, and highest in Picea koraiensis-Juglans mandshurica mixed plantations. (2) The difference of C:N and C:P in the soil of four plantation types was significant, pure Picea koraiensis plantation was higher than three mixed plantations, and lowest in Picea koraiensis-Juglans mandshurica mixed plantations. (3) The difference of N content and P content in the leaf and litter of three mixed species was significant, lowest in Phellodendron amurense, and highest in Juglans mandshurica, but all of them were higher than that of Picea koraiensis. (4) The C:N and C:P in the leaf and litter of mixed tree species were highest in Phellodendron amurense and lowest in Juglans mandshurica, but all of them were obvious lower than that of Picea koraiensis. (5) The correlations of C content, N content, P content, C:N and C:P between leaf and soil as well as between litter and soil were higher in the mixed species than that in Picea koraiensis.

ConclusionAccording to the C contents, N contents, P contents, C:N, C:P and N:P in the leaf, litter and soil parts of Picea koraiensis plantations, Juglans mandshurica and Fraxinus mandshurica should be prefer as the mixed tree species, more attention should be paid to the lack of N content and P content during the cultivation of Picea koraiensis plantations.