C,N,P Ecological Stoichiometric Characteristics Of Pure Plantation And Mixed Plantation Of 6 Species In The Ashi River Basin

The 29-year-old planted by the Forest Cultivation Experimental Station of Northeast Forestry University was selected after narrow cutting of natural forests:pure Pinus koraiensis plantation(Pn),pure Larix olgensis plantation(L),pure Picea koraiensis plantation(Pc),pure Fraxinus mandshurica plantation(F),pure Phellodendron amurense plantation(Ph),pure Juglans mandshurica plantation(J)and Juglans mandshurica-Pinus koraiensis mixed plantation(JPn);and secondary forests and natural 31-year-olds after narrow stripping of natural forests:pure Larix olgensis plantation(Lo),Larix olgensis-Fraxinus mandshurica mixed plantation(LF),Larix olgensis-Juglans mandshurica mixed plantation(LJ),Juglans mandshurica-Picea koraiensis mixed plantation(JPc),Juglans mandshurica-Larix olgensis mixed plantation(JL),were used as the research objects.The carbon(C),nitrogen(N),and phosphorus(P)contents of their leaf-litters-soils and their ecological stoichiometry were studied.The results show:(1).In the study of nutrient pattern of 6 tree species,P content in the leaves,C and P content in the soil,C/P in the soil of coniferous plantation was significantly lower than that of broad-leaved plantation.Coniferous plantation leaves have higher utilization rates of P elements than broad-leaved plantations,and coniferous plantations are more conducive to effective P accumulation than broad-leaved plantation soil.The resorption efficiency of coniferous plantation is N>P,and the resorption efficiency of P is significantly lower than that of broadleaf plantation,and the effective P supply and activation of P element in soil are significantly stronger than that of broadleaf plantation.The N content of litter in pure Pinus koraiensis plantation is relatively low,and the supply ability available P to the soil and and activation ability N and P elements are strong.The C content of litter in pure Larix olgensis plantation is relatively low,and the mineralization rate of soil organic matter is faster than that of pure Juglans mandshurica plantation,the available Psupply ability and P element activation ability of the soil are strong.The leaf P content of pure Picea koraiensis plantation was relatively low,and the utilization efficiency of P element was the highest.N content in the leaves,C content,N content and P content in the litter and soil,N resorption efficiency of Fraxinus mandshurica plantation were higher than that of other plantations,and Fraxinus mandshurica plantation leaves have lowest utilization rates of N elements.P resorption efficiency of Phellodendron amurense were higher,the soil activation ability to N of Juglans mandshurica plantation was stronger than that of other plantations.From the point of optimal utilization of nutrients and rational allocation of nutrient resources,conifer tree and broad-leaved tree mixed,such as Pinus koraiensis and Fraxinus mandshurica,Larix olgensis and Fraxinus mandshurica mixed,could make a complementary nutrient allocation and utilization pattern.(2).In the pure and mixed plantation of Larix olgensis,compared with the secondary forest,the soil nutrient C,N,and P contents of the three types of Larix olgensis plantations decreased significantly.Leaf C,N,and P of Larix olgensis in the pure and mixed plantations of Larix olgensis were not significantly affected by the mixing of tree species,but their litter content and decomposition rate were significantly affected.Compared with pure Larix olgensis plantation,the soil C and P contents of Larix olgensis-Fraxinus mandshurica mixed plantation and the soil N of Larix olgensis-Juglans mandshurica mixed plantation increased,however,the soil P availability was the highest among the three Larix olgensis plantations.The soil P content in Larix olgensis-Fraxinus mandshurica mixed plantation of was greater than that in Larix olgensis-Juglans mandshurica mixed plantation.Compared with Larix olgensis-Juglans mandshurica mixed plantation,Larix olgensis-Fraxinus mandshurica mixed plantation can effectively alleviate the attenuation of most nutrients in the soil.Therefore,from the perspective of soil nutrition conservation,mixed species of Larix olgensis may be preferentially selected Fraxinus mandshurica.(3)In the pure and mixed plantation of Juglans mandshurica,compared with the secondary forest,Juglans mandshurica-picea koraiensis mixed plantation the contents of C,N and P in leaves and C and P in litter are similar to those in the secondary forest due to the selection of tree species,but the soil C,N,and P contents of the Juglans mandshurica-picea koraiensis mixed plantation and juglans mandshurica-Larix olgensis mixed plantation also decreased.The N,P content of the litter of the Juglans mandshurica-picea koraiensis mixed plantation is higher,which is favorable for its decomposition;the N,P content of the juglans mandshurica-Larix olgensis mixed plantation is lower,which is the most unfavorable for decomposition.Compared with pure Juglans mandshurica plantation,the content of soil C was lower in the Juglans mandshurica-Pinus koraiensis mixed plantation,while the content of soil N was higher.The content of N in the soil of Juglans mandshurica-pinus koraiensis mixed plantation and Juglans mandshurica-Larix olgensis,the soil P content of juglans mandshurica-pinus koraiensis mixed plantation was more affected by the litter of Juglans mandshurica.The soil P content of the juglans mandshurica-picea koraiensis was more affected by the litter of the picea koraiensis,and juglans mandshurica-larch mixed plantation soil P content was more affected by litter of Larix olgensis.The utilization efficiency of N in Pinus koraiensis,Picea koraiensis,Juglans mandshurica in Juglans mandshurica-Larix olgensis mixed plantation was closely related to soil quality of corresponding mixed plantation.(4)Pure Juglans mandshurica plantation,Juglans mandshurica in Larix olgensis-Juglans mandshurica mixed plantation and Juglans mandshurica-Pinus koraiensis mixed plantation and Juglans mandshurica-Larix olgensis mixed plantation,mixed species in Larix olgensis-Fraxinus mandshurica mixed plantation,Juglans mandshurica-Picea koraiensis are restricted by N elements.Pure Larix olgensis plantation,Larix olgensis in Larix olgensis-Fraxinus mandshurica mixed plantation,Juglans mandshurica in Juglans mandshurica-Picea koraiensis mixed plantation is restricted by P element.Picea koraiensis in Juglans mandshurica-Picea koraiensis mixed plantation,Juglans mandshurica and Larix olgensis,mixed Larix olgensis was restricted by N and P elements.According to the nutrient content and ecological stoichiometry of six tree pure plantation and their mixed plantation in the Ashi River Basin,their characteristics and their correlations in leaf-litter-soil,and comprehensive consideration of the improvement of litter quality and decomposition rate,Nutrient conservation ability,leaf-litter-soil nutrient flow efficiency,nutrient use efficiency.In the study area,Larix olgensis should be preferentially selected mixed with Fraxinus mandshurica when it is cultivated.In mixed plantation,different types of tree species may have different nutrient restrictions.Fertilization should be applied separately for the restricted elements of different tree species.