Effects Of Nitrogen And Phosphorus Fertilization On The Growth And Ecological Stoichiometry Of Fraxinus Mandshurica Rupr.

Fertilization is an effective means to improve forest productivity,and reasonable fertilization is the key to improving fertilizer efficiency.To understand the effect of N and P addition on the stand growth,physiological indexes and nutrient stoichiometric characteristics of Fraxinus mandshurica plantation,we conducted the study in Xiaojiu Forest Farm,Shangzhi City,Heilongjiang Province,we selected a 15-year-old ash plantation for two-year nitrogen and phosphorus fertilization test.We set up different N,P,N and P mixed for a total of 12 fertilization treatments to measure growth,physiological,C,N and P concentrations of leaves,fine roots and soils,the results showed that:(1)Each fertilization treatment increased the DBH growth,SLA,photosynthetic pigment and soluble protein content of ash,with the increase of N supply the soluble sugar content of leaves decreased,With the increase of N supply the content of starch and NSC decreased first and then increased;with the increase of P supply the soluble sugar,starch and NSC content of leaves decreased,but the impact is not significant;only N2P1 treatment of N and P mixed fertilization has been improved the NSC content of leaves.(2)With two years of different fertilization treatments,the C and N concentration of soils increased significantly,and the P concentration of soils was not significantly with the all fertilization treatments.the soil nutrient concentration of each fertilization treatment in the second year was higher than that in the first year.N and P mixed fertilization significantly increased N concentration of leaves and fine roots,the P concentration of leaves and fine roots increased significantly with the increase of P fertilization,the C and N concentration of leaves and the P concentration of fine roots decreased first and then increased during May to August,the max concentration appears in June,and the P concentration of leaves and the N concentration of fine roots show the opposite trend.Each fertilization increased resorption efficiency of N and P,and the increments of N resorption efficiency were higher than P resorption efficiency.(3)Each fertilization treatment decreased the C:N and C:P ratios of soil;except N fertilization the N:P ratios of soils decreased with the other fertilization treatments;in the first year,the soil nutrient stoichiometry in each fertilization treatment was higher than that in the second year.Each fertilization treatment decreased the C:N and C:P ratios of leaves;the N:P ratios of leaves decreased first and then increased in the plots of N addition,and the N1P0 significantly higher than NOPO;the N:P ratios of leaves decreased significantly with the P fertilization;the range of N:P radios for the treatment of N and P mixed fertilization was 14.34~17.86.Each fertilization treatment decreased the C:N and C:P ratios of fine roots;the N:P radios increased by the treatments of N fertilization but the difference was not significant,P?N and P mixed fertilization all decreased the N:P radios of fine roots.In short,fertilization increased the photosynthetic site by increasing the specific leaf area of the leaves,increasing the content of chlorophyll and soluble protein to promote photosynthesis,and increasing the accumulation of photosynthetic products,then promoted trees growth.The N element was the main limiting elements for the grow of Fraxinus mandshurica plantation,the N and P mixed fertilization was better than the single N or P fertilization in relieving N restriction and promoting the growth of ash.