Ecological Stoichiometric Characteristics Of C,N And P Elements In Picea Koraiensis Plantations

Taking 31 years of Picea koraiensis X Juglans mandshurica mixed plantation,Picea koraiensis X Fraxinus mandshurica mixed plantation,Picea koraiensis X Phellodendroamurense mixed plantation and pure Picea koraiensis plantation which was planted on the natural forest narrow strip clear cutting land in Ashihe-drainage basin as materials,the seasonal dynamics of leaf-litter-soil C,N and P concents and their stoichiometric ratios characteristics were studied in this paper.Results showed that:(1)At early growth season,the growth of leaf of Picea koraiensis were mainly limited by N content,while it turned to be restricted by both N and P contents at growing season.The correlation among C,N,P content were significant in four kinds of leaf of Picea koraiensis(P<0.05).And the C:N and C:P of leaf were affected by the both N and P contents.The N:P in Picea koraiensis X Juglans mandshurica mixed plantation and Picea koraiensis X Fraxinus mandshurica mixed plantation leaf was largely affected by P content,while it becomes to be controlled by N content in Picea koraiensis X Phellodendron amurense mixed plantation mostly in the whole growing season.The leaf N:P in pure Picea koraiensis plantation were both affected by N and P contents throughout the growing season.(2)The possibility and quantity of nutrient returning soil in three mixed plantations were greater than that of pure Picea koraiensis plantation.And the Picea koraiensis mixed with Juglans mandshurica and Fraxinus mandshurica is more likely to increase soil fertility.The turnover rate of nutrients in the mixed plantations of Picea koraiensis was higher than that of pure Picea koraiensis plantation,and the litter decomposition rate of Juglans mandshurica was the fastest,which could improve soil quality.The litter N:P in Picea koraiensis×Juglans mandshurica mixed plantation and pure Picea koraiensis was largely affected by P content,while it becomes to be controlled by by both N and P contents in Picea koraiensis X Fraxinus mandshurica mixed plantation and Picea koraiensis×Phellodendron amurense mixed plantation.The C:N and C:P of the litter of Juglans mandshurica,Fraxinus mandshurica and Phellodendron amurense was affected by the corresponding N and P contents,respectively.And the N:P of litter of Juglans mandshurica was affected by P content,while it becomes to be controlled by both N and P contents in Fraxinus mandshurica and Phellodendron amurense.(3)The mixed plantations of Picea koraiensis can effectively improve the soil fertility compared with the pure Picea koraiensis plantation,but the ability of the three mixed species to improve soil nutrients is different.The Juglans mandshurica is greater and the Phellodendron amurense is weaker.The coupling correlation of C,N and P contents in four plantation soils of Picea koraiensis was significant(P<0.05),and the distribution and variation of soil C and N contents are relatively consistent.The N:P of soil of three mixed plantations were affected by N and P contents.The N content had a greater effect on the N:P of the Picea koraiensis × Juglans mandshurica mixed plantation and Picea koraiensis X Phellodendron amurense mixed plantation.The P content had a greater effect on the N:P of the Picea koraiensis × Fraxinus mandshurica mixed plantation;The N:P of the pure Picea koraiensis plantation was mainly affected by N content.(4)The contents of C and N in each component of the four Picea koraiensis plantations were as follows:leaf>Picea koraiensis litter>soil,and there were significant differences among different components.Except for the Picea koraiensis×Juglans mandshurica mixed plantation,the P content of leaf of the other three plantations were significantly higher than that of soil and litter.The C:N and C:P of the four plantations showed that Picea koraiensis litter>leaf>soil,and there were significant differences among different components.The N:P of leaf and Picea koraiensis litter in the four plantations were not much different,but significantly higher than the soil.To improving soil quality,nutrient utilization efficiency and forest growth,the mixed Picea koraiensis plantations should be cultivated in Ashihe-drainage basin,especially the Picea koraiensis × Juglans mandshurica mixed plantation,which is superior to the cultivation of Picea koraiensis plantation based on the leaf-litter-soil nutrient content and ecological stoichiometry of the Picea koraiensis plantations,and considering the decomposition ratio of litters and the efficiency of nutrient utilization.In addition,the nitrogen fertilizers should be added at the early stage of growth,and nitrogen and phosphate fertilizers should be added during the stage of vigorous growth to meet the requirement of normal growth of Picea koraiensis.