Effects Of Nitrogen Deposition And Phosphorus Addition On The Growth Characteristics In Chinese Fir Seedlings

Chinese fir?Cunninghamia lanceolata?Lamb.?Hook.?is widely distributed in the southern region of China,and is also the main plantation tree species of plantation.In order to explore the impact of the increasingly severe nitrogen?N?deposition situation and low phosphorus?P?stress on the growth of southern China.So,this article takes Chinese fir seedlings as the experimental object and sets 9 treatment levels: control treatment?CK: N0-P0?,low N(N30: 30 kg N ha^-1 yr^-1),high N(N60: 60 kg N ha^-1 yr^-1),low P(P20: 20 mg kg^-1),high P(P40: 40 mg kg^-1),interaction treatment?N30-P20,N30-P40,N60-P20,N60-P40?.The response of Chinese fir seedling biomass,non-structural carbon?NSC?content and eco-stoichiometric characteristics of N and P to different degrees of N and P addition were detected.The results showed that:?1?Addition N alone,significantly increased the biomass?belowground biomass,aboveground biomass and total biomass?and root-shoot ratio,the leaf starch content was first decreased and then increased,and significantly increased the soluble sugar and total NSC carbon in the stems,and the N concentration in each organ increased significantly.In the N30 treatment,the branch N: P ratio was significantly reduced.In N60 treatment,the N: P ratio of roots and branches significantly increased.N addition significantly increased the N: P ratio of the stem?P <0.05?.?2?Addition P alone,significantly promoted the aboveground biomass and total biomass,significantly reduced the root-shoot ratio;significantly reduced the starch content of the leaf,and significantly increased the total starch,soluble sugar and NSC content of the root At the same time,addition P significantly increased the P concentration in each organ,and the N:P ratio of leaves,branches and roots was significantly decreased in P40 treatment?P < 0.05?.?3?Compared with N30 treatment,N,P interaction treatment significantly increased aboveground biomass and root NSC content?P < 0.05?;N30-P20 treatment significantly increased belowground biomass,total biomass,branch soluble sugar content,leaf and branch NSC content,N30-P20 treatment significantly reduced stem starch content?P < 0.05?,N30-P40 significantly reduced the belowground biomass,root shoot ratio,NSC content of leaves and branches,significantly increased stem starch content,N: P ratio of leaves and roots?P < 0.05?.?4?Compared with N60 treatment,N,P interaction treatment significantly increasedaboveground biomass,root soluble sugar content and NSC content?P < 0.05?;N60-P40 treatment significantly reduced belowground biomass,root shoot ratio,starch content and stem soluble sugar content,significantly increased branch soluble sugar content and NSC content and N: P ratio of leaves?P < 0.05?.Significantly increased the N:P ratio of the organs,and the N:P ratio of the root system exceeded 16 under the combined treatment of N60 and P.This experiment found that the addition of N and P significantly promoted the growth of Chinese fir seedlings.The principle is that the addition of N and P increases the effective N and P content in the soil and promotes the absorption of plants,thereby increasing the N and P content of Chinese fir seedlings,increasing the photosynthetic level,synthesizing more photosynthetic products,and promoting growth.In this experiment,the N-P utilization efficiency of Chinese fir seedlings treated with N30-P20 was higher,and can maintain the balance of N and P in plants.