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Through the systematic investigation of nitrogen isotope composition (δ15N) in modern plants in Dongling Mountain in Beijing,the characteristics of δ15N in plants,the differences of δ15N among plants with different functional types,and the altitudinal trends of plant δ15N values revealed the environmental effects on δ15N.Our results are:(1) the values of δ15N of plants in Dongling Mountain range between -8.0‰ and 14.0‰,with an average value of -1.03‰;(2) δ15N values are variant among different plant functional types.Generally,the δ15N of shrubs are smaller than that of trees,and larger than that of herbaceous plants.The main reason may be the selective absorption of variant nitrogen resource with different δ15N values in soil;(3) there is a second-order polynomials relationship between the altitudes and the average δ15N values of plants,which shows a negative and positive correlation below and above 1350 m a.s.l.,respectively.This indicates that the precipitation is a main controlling factor of plant 15N fractionation for the former,and the temperature for the latter;(4) three different,i.e.,positive,negative,and no significant,correlations are performed between δ15N of individual species and altitudes.This may be related to different inherited characteristics and the process of nitrogen metabolize;and (5) variant altitudinal trends of plant δ15N are associated with different 15N composition of soil at different altitude,for which the key influencing factors are the changing temperature and precipitation with altitude rather than nitrogen content in leaf.
Through the systematic investigation of nitrogen isotope composition (δ15N) in modern plants in Dongling Mountain in Beijing, the characteristics of δ15N in plants, the differences of δ15N among plants with different functional types, and the altitudinal trends of plant δ15N values revealed the environmental effects on δ15N.Our results are: (1) the values of δ15N of plants in Dongling Mountain range between -8.0 ‰ and 14.0 ‰, with an average value of -1.03 ‰; (2) δ15N values are variant among different plant functional types. Generally, the δ15N of shrubs is smaller than that of trees, and larger than that of herbaceous plants. The main reason may be the selective absorption of variant nitrogen resources with different δ15N values in soil; (3) there is a second-order polynomials relationship between the altitudes and the average δ15N values of plants, which shows a negative and positive correlation below and above 1350 m asl, respectively. This indicates that the precipitation is am ain controlling factor of plant 15N fractionation for the former, and the temperature for the latter; (4) three different, ie, positive, negative, and no significant, correlations are performed between δ15N of individual species and altitudes. This may be related to different inherited characteristics and the process of nitrogen metabolize; and (5) variant altitudinal trends of plant δ15N are associated with different 15N composition of soil at different altitude, for the the key influencing factors are the changing temperature and precipitation with altitude rather than nitrogen content in leaf.