Premium
Relationships between leaf δ 15 N and leaf metallic nutrients
Author(s) -
Chen Chongjuan,
Wu Yingjie,
Wang Shuhan,
Liu Zhaotong,
Wang Guoan
Publication year - 2020
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.8970
Subject(s) - chemistry , ammonium , nutrient , nitrification , manganese , fractionation , nitrogen , metal , potassium , environmental chemistry , nitrate , phosphorus , zinc , isotope fractionation , magnesium , organic chemistry
Rationale Nitrogen (N) isotopic ratios (δ 15 N values) of plants are primarily determined by the δ 15 N values of their N sources. Metallic nutrients affect plant N uptake. However, there is little knowledge of the relationships between leaf δ 15 N values and leaf metallic nutrients. The δ 15 N values are often lower in soil nitrate (NO 3 − ) than in ammonium (NH 4 + ) due to large isotopic fractionation during nitrification. Plants acquire more NO 3 − than NH 4 + when accumulating high potassium (K), calcium (Ca) and magnesium (Mg) to maintain charge balance. In addition, plants that absorb more NO 3 − than NH 4 + increase the soil pH and decrease the availability of iron (Fe), manganese (Mn) and zinc (Zn). We therefore hypothesized that leaf δ 15 N values correlate negatively with K, Ca and Mg contents, while positively with Fe, Mn and Zn contents. Methods Leaves of non‐N‐fixing plants were sampled across an approx. 6000 km transect in China and their δ 15 N values and metallic nutrient content were determined using elemental analyzer/isotope ratio mass spectrometry. Results Inconsistent with the hypothesis, leaf δ 15 N values correlated positively with leaf K, Ca and Mg, indicating higher δ 15 N values of soil NO 3 − than NH 4 + . Higher δ 15 N values of soil NO 3 − revealed stronger denitrification than nitrification in the study regions because isotopic fractionation occurs during both processes. Leaf δ 15 N values correlated negatively with Fe, relating to decreases in soil Fe availability, which might be attributed to oxidation of Fe 2+ to Fe 3+ supplying electrons for denitrification, while greater uptake of NO 3 − than NH 4 + of plants increases soil pH. Leaf δ 15 N values correlated positively with Zn and did not correlate with Mn. These observed relationships between leaf δ 15 N values and metallic nutrients, except Mn, were independent of vegetation or soil types. Conclusions This study has enriched our knowledge of associations between metallic nutrients and N cycling in plant–soil systems, especially for the roles of Fe in soil N transformations and K, Ca and Mg in plant N uptake.