Response Of Leaves,Stems And Roots Stoichiometric Characteristics Of Acer Mono And Pinus Tabulaeformis From Different Provenances To Simulated Nitrogen Deposition

The influence of atmospheric nitrogen deposition on ecosystem has been paid much attention all over the world.China is one of the main areas of atmospheric nitrogen deposition.It is of great significance to study the effects of nitrogen deposition on forest in China.In this paper,we set Acer mono and Pinus tabulaeformis of different provenances as research objects,and set five nitrogen treatments,including Control(0 kg·hm^-2·a^-1),Low nitrogen(15 kg·hm^-2·a^-1),Medium nitrogen(25 kg·hm^-2·a^-1),High nitrogen(50 kg·hm^-2·a^-1)and Ultra high nitrogen(150 kg·hm^-2·a^-1).By collecting the leaves,stems and roots of plants and measuring the nitrogen and phosphorus content indexes of each part,the response of the stoichiometric characteristics of each organ of different plants to the simulated nitrogen deposition was discussed,which provided data for the future ecological environment protection and plant selection.The main results were as follows:?1?The N content in each organ showes leaves>stems>roots,the P content showes leaves>stems>roots,and the N/P showes leaves>stems>roots.Leaf N,leaf P and root P of Acer mono are higher than those of Pinus tabulaeformis,and root N of Acer mono is lower than that of Pinus tabulaeformis.Acer mono has higher adaptability to simulated nitrogen deposition than Pinus tabulaeformis,in the same environment,which may aggravate the nitrogen-restricted degree of Pinus tabulaeformis.Continuous nitrogen addition should not exceed three years.Nitrogen addition may aggravate the nitrogen-restricted state of plant growth.?2?The low nitrogen level increases the content of N and P in Acer mono's leaves,stems and roots,the content of P in Pinus tabulaeformis's leaves and roots,and decreases the N and P content in stems of Pinus tabulaeformis.Low nitrogen level decreases stem N content and stem P content of Pinus tabulaeformis.Medium nitrogen level decreases root N content of Acer mono and the N and P content in stem of Pinus tabulaeformis.The high nitrogen deposition level reduces the content of P in Acer mono's stems and Pinus tabulaeformis's stems,and root N and P content of Pinus tabulaeformis.Nitrogen deposition simulating reduces the leaf N content of Pinus tabulaeformis.The effect of low nitrogen deposition level on plants is better than that of high nitrogen deposition level.?3?The N and P contents of the leaves and stems of Acer mono are increased by nitrogen addition.With the nitrogen concentration increasing,the promoting effect gradually reduce.Plants from different provenances respond to nitrogen addition at different levels.?4?The response of each organ of Pinus tabulaeformis to simulated nitrogen deposition is different.The provenance difference of the stoichiometric characteristics of plant organs mainly manifested as the difference in the concentration of nitrogen addition and degree of response,and the characteristics are not uniform among organs.?5?In each plant organ,the N content was positively correlated with the P content,while the P content was negatively correlated with the N/P.The N content of leaves and stems,P content of leaves and stems,and P content of stems and roots were significantly positively correlated.The correlation between leaves and stems was closer than that between leaves and roots.The index of significant correlation between Acer mono and Pinus tabulaeformis was different.