Effects Of Stand Age On The Ecological Stoichiometric Characteristics Of Pinus Koraiensis Plantation

As one of the main afforestation tree species in Northeast China,Pinus koraiensis plays an important role in promoting regional economic development and maintaining ecological environment stability.However,due to the long-term afforestation model of artificial pure forest and the reasons of coniferous tree species themselves,P.koraiensis artificial pure forest is facing a more common problem of soil fertility decline in operation.Therefore,it is of great significance to clarify the changes of C,N and P contents in leaf,litter and soil during the growth of P.koraiensis plantations of different ages,and to explore the relationship between nutrients in leaf,litter and soil.In this paper,four kinds of P.koraiensis plantations（26 a,37 a,48 a and 54 a）in Yimianpo Forest Farm of Shangzhi City were taken as the research objects.Based on the theory of ecological stoichiometry,the contents of carbon（C）,nitrogen（N）,phosphorus（P）and stoichiometric ratio of leaf,litter and soil were analyzed by combining field sampling and indoor analysis,in order to provide theoretical basis for the precise improvement of management quality and soil fertility management level of P.koraiensis plantations.The main results are as follows:（1）The contents of C,N and P in the leaves of P.koraiensis plantation increased first and then decreased with the increase of forest age,while the changes of C:N,C:P and N:P with the increase of forest age were not consistent.The mean values of C:N,C:P and N:P in the leaves of the four forest stands ranged from 28.63 to 35.05,311.34 to 378.13 and 10.52 to 12.85,respectively.Among them,C:N and C:P were the highest in the 26 a stand and the lowest in the48 a stand,N:P was the highest in 54 a forest stand and the lowest in 37 a forest stand.（2）The contents of C,N and P in the litter of the four P.koraiensis plantations ranged from 450.75 to 486.91,5.52 to 9.89 and 0.34 to 0.59 g·kg^-1,respectively,and the overall element pattern was high C,low N and P.With the increase of forest age,the content of litter C showed a trend of’increase-decrease-increase’,and there was no significant difference among different age stands.The N content,C:P and N:P generally decreased first and then increased.The P content and C:N showed a trend of increasing first and then decreasing,and the C:N of litter in 26 a and 37 a forest stands was significantly higher than that in 48 a and 54 a forest stands.（3）With the increase of forest age,the soil C,N content and N:P in 0～20 cm soil layer of P.koraiensis plantation increased gradually.C:N and C:P showed a trend of decreasing first and then increasing.The P content showed a trend of increasing first and then decreasing.The soil P content of the four forest stands was low(0.23 to 0.71 g·kg^-1),and the soil P content of the 54 a forest stand was 20.36%lower than that of the 48 a forest stand.（4）Among the different components of the four aged P.koraiensis plantations,the contents of C and N were leaf,litter and soil from high to low,and the contents of C:N,C:P,N:P were litter,leaf and soil from high to low.The order of P content in different components of 26 a forest stand from high to low was leaf,litter and soil,and that in different components of other three-year-old forest stands from high to low was leaf,soil and litter.The contents of N,P and C:N were positively correlated with each other among leaf,litter and soil.The nutrient interaction effect was significant during the growth of P.koraiensis plantation.（5）Based on the research results of leaf,litter and soil ecological stoichiometric characteristics of P.koraiensis plantation,the 26 a and 37 a forest stands in the study area should be cut and pruned in time to adjust the canopy density,reduce the influence of insufficient light,and promote the decomposition and release of nutrients in the litter layer.Compared with the 48 a forest stand,soil P content of the 54 a forest stand decreased to a certain extent.Therefore,the diversity of understory plants should be appropriately increased to improve the chemical quality of litter and promote the improvement of soil quality.