Research On Ecological Stoichiometric Characteristics Of Pinus Koraiensis Plantations

Pinus koraiensis is the unique and precious tree species in northeast China,with excellent wood texture and great economic importance.With the increase of Pinus koraiensis plantation forests,drawbacks,e.g.,lacking structural diversity,poor stability,soil degradation,low productivity,and some other problems.We studied the mixed plantation of Pinus koraiensis and Fraxinus mandschurica,mixed plantation of Pinus koraiensis and Juglans mandshurica,mixed plantation of Pinus koraiensis and Phellodendron amurense,and pure Pinus koraiensis plantation in Maoershan region,Heilongjiang Province,after analyzing dynamics in carbon?C?,nitrogen?N?,phosphorus?P?concentration,and the stoichiometry traits of leaf,litter and soil,then their difference between mixed plantation and pure Pinus koraiensis plantation were evaluated.Furthermore,the limiting elements in Pinus koraiensis plantations were figured out by referring to the average values of leaf stoichiometry traits.Finally,we were expected to supply theoretical foundation for scientific management.The main results in this thesis are as below:?1?The C,N,P and stoichiometry traits of leaf,litter and soil in four Pinus koraiensis plantations significantly changed from May to September,however,there was no consistent trend among four forest types.?2?Organic C and total N concentration in four forest types were same,i.e.,leaf>litter>soil.Except for the mixed forest of Pinus koraiensis and Fraxinus mandschurica,total P concentration in the residual forest types had the same trend,i.e.,leaf>soil>litter.Each stoichiometry trait was controlled by two elements,therefore,no consistent trend were observed among four forest types.?3?Compared with mixed plantations,pure Pinus koraiensis plantation had lower values in N and P concentration of soil,litter and leaf.In pure Pinus koraiensis plantation,leaf C:N was only smaller than mixed plantation of Pinus koraiensis and Phellodendron amurense,leaf C:P was smaller than three mixed plantations,and leaf N:P was larger than three mixed plantations.Litter C:N,C:N and N:P ratio in pure Pinus koraiensis plantation were larger than three mixed plantations.Soil C:P and N:P ratio in pure Pinus koraiensis plantation were smaller than three mixed plantations.?4?To sum up,mixed plantation of Pinus koraiensis and Juglans mandshurica had the most optimum soil fertility.Mixed plantation of Pinus koraiensis and Juglans mandshurica had highest soil organic C and total N concentration of each depth,and a slightly lower value of soil total P concentration than mixed plantation of Pinus koraiensis and Phellodendron amurense.?5?In our study,leaf organic C and P concentration in four forest types were higher than global average(1.46 g·kg^-1)and national average(1.46 g·kg^-1),respectively,however,leaf total N concentration was lower than global average(20.6 g·kg^-1)and national average(20.2 g·kg^-1).Leaf N:P ratio in four forest types was lower than 14,indicating that plant growth in this region was primarily limited by N.Therefore,N fertilization has great meaning in alleviating N limitation,improving nutrient use efficiency,reducing nutrient loss,and enhancing the productivity of Pinus koraiensis plantations.