Relationships between leaf δ¹⁵ N and leaf metallic nutrients

Area of Science:

• Plant Ecology
• Biogeochemistry
• Isotope Geochemistry

Background:

• Plant leaf nitrogen (N) isotopic ratios (δ¹⁵N) are influenced by N sources and metallic nutrients.
• Metallic nutrients impact plant N uptake, affecting leaf δ¹⁵N values, but relationships are not well understood.
• Soil nitrate (NO₃^-) generally has lower δ¹⁵N than ammonium (NH₄⁺) due to isotopic fractionation during nitrification.

Purpose of the Study:

• To investigate the relationships between leaf δ¹⁵N values and leaf metallic nutrient content in non-N-fixing plants.
• To test the hypothesis that leaf δ¹⁵N values correlate negatively with K, Ca, Mg and positively with Fe, Mn, Zn.

Main Methods:

• Plant leaves were collected across a 6000 km transect in China.
• Leaf δ¹⁵N values were determined using elemental analyzer/isotope ratio mass spectrometry.
• Leaf metallic nutrient content was analyzed concurrently.

Main Results:

• Leaf δ¹⁵N values positively correlated with K, Ca, and Mg, contrary to the hypothesis.
• Leaf δ¹⁵N values negatively correlated with Fe, suggesting decreased soil Fe availability linked to denitrification.
• Leaf δ¹⁵N values positively correlated with Zn but showed no correlation with Mn; relationships were largely independent of vegetation or soil types.

Conclusions:

• Plant N uptake and soil N cycling are significantly associated with metallic nutrient status.
• Iron (Fe) plays a role in soil N transformations, while K, Ca, and Mg influence plant N uptake.
• Findings enrich understanding of metallic nutrient roles in plant-soil N cycling.