Relationships between leaf δ¹⁵N and leaf metallic nutrients

Abstract. Metallic nutrients play a vital role in plant physiological and biochemical processes such as nitrogen uptake and assimilation, which cause isotopic fractionation against ¹⁵N. Thus, investigating the relationships between leaf nitrogen isotope ratio (δ¹⁵N) and leaf metallic nutrients could enhance our understanding of nitrogen (N) cycling. However, to our knowledge, these relationships have not been examined as yet. To fill in this research gap, we analyzed leaf δ¹⁵N and leaf potassium (K), Calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn) and zinc (Zn) contents of 624 non-N₂-fixing plant samples and revealed the relationships between leaf δ¹⁵N and these metallic elements. Overall, leaf δ¹⁵N correlated positively with leaf K, Ca, Mg and Zn, and negatively with leaf Fe, whereas not with leaf Mn. The relationships of leaf δ¹⁵N with leaf K, Ca, Mg, Zn and Fe were not affected by both vegetation type and soil type, suggesting that the observed relationships could be universally valid. However, the relationship between leaf δ¹⁵N and leaf Mn depended on vegetation type and soil type, therefore, the observed relationship should not be considered to be universal. These metallic nutrients together accounted for 55.7 % of the variations in leaf δ¹⁵N; this emphasized the significance of metallic nutrients in determining leaf δ¹⁵N.