Seasonal Dynamics Of Energy And Nutrients Of Pinus Koraiensis Seedlings

In this experiment,Changbai Mountain Nature Reserve was taken as the research area,and the natural 1-year-old Pinus koraiensis seedlings were studied.The photosynthetically active radiation(PAR)of the two forests,chlorophyll content,the plant biomass,non-structural carbohydrates(NSC)and total nitrogen and phosphorus concentrations and contents were measured in the primary and secondary forests throughout the growing season.The seasonal dynamics of leaf traits,the distribution characteristics of various organs,the seasonal dynamics of energy and nutrients storage and distribution were studied,and the seasonal dynamics and differences of the light environment in primary and secondary forests,relationship between the energy and nutrients storage of Pinus koraiensis seedlings and light environment,light resource utilization strategy of Pinus koraiensis seedlings,and the influence of light environment on the regeneration of Pinus koraiensis seedlings were analysed systematically.The results show:1.The cumulative PAR under the primary and secondary forests had basically the same seasonal trend throughout the year,and the overall is "double peak".The NSC concentrations and contents of the 1-year-old Pinus koraiensis seedlings in primary and secondary forests were consistent with the seasonal trends of cumulative PAR.The difference between the NSC contents in the two forests is highly consistent with the difference between the light environment in the two forests from April to November.Therefore,it can be considered that the difference in light conditions is one of the main reasons for the difference in the regeneration of Pinus koraiensis seedlings in the primary and secondary forests.2.Although the chlorophyll content and leaf mass per area(LMA)of the Pinus koraiensis seedlings in the primary forest showed a stronger shade-avoidance response than that in the secondary forest to enhance their photosynthesis ability.However,the biomass of Pinus koraiensis seedlings in secondary forests with abundant light resources was higher than that in the primary forests.This difference leads to the selection of the Pinus koraiensis seedlings in the primary forest to allocate more biomass to the leaves for constructing needles,resulting in a lower proportion of biomass of the stems and roots of the Pinus koraiensis seedlings in the primary forest than that in the secondary forest,which may affect the growth and development of these organs.3.The good light conditions under the secondary forest in the early stage of canopy closure enable the Pinus koraiensis seedlings to produce more photosynthetic products during the period,and accumulate starch to store energy,in order to pass the period of canopy closure better,while the total N content in the organs of Pinus koraiensis seedlings in the primary forest was significantly greater than that in the secondary forests in the autumn,this can result in higher relative growth rate of Pinus koraiensis seedlings in the primary forest in autumn,but also means that the resistance of the Pinus koraiensis seedlings in the primary forest is lower,which can hinder the over-wintering of the Pinus koraiensis seedlings better in the primary forest.