Leaf nitrogen affects photosynthesis and water use efficiency similarly in nitrogen-fixing and non-fixing trees
Journal of Ecology
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Abstract
- Nitrogen (N)-fixing trees are thought to break a basic rule of leaf economics: higher leaf N concentrations do not translate into higher rates of carbon assimilation. Understanding how leaf N affects photosynthesis and water use efficiency (WUE) in this ecologically important group is critical.
- We grew six N-fixing and four non-fixing tree species for 4–5 years at four fertilization treatments in field experiments in temperate and tropical regions to assess how functional type (N fixer vs. non-fixer) and N limitation affected leaf N and how leaf N affected light-saturated photosynthesis (Asat), stomatal conductance (gsw) and WUE (WUEi and δ13C).
- Asat, WUEi and δ13C, but not gsw, increased with higher leaf N. Surprisingly, N-fixing and non-fixing trees displayed similar scaling between leaf N and these physiological variables, and this finding was supported by reanalysis of a global dataset. N fixers generally had higher leaf N than non-fixers, even when non-fixers were not N-limited at the leaf level. Leaf-level N limitation did not alter the relationship of Asat, gsw, WUEi and δ13C with leaf N, although it did affect the photosynthetic N use efficiency. Higher WUE was associated with higher productivity, whereas higher Asat was not.
- Synthesis: The ecological success of N-fixing trees depends on the effect of leaf N on carbon gain and water loss. Using a field fertilization experiment and reanalysis of a global dataset, we show that high leaf-level photosynthesis and WUE in N fixers stems from their higher average leaf N, rather than a difference between N fixers and non-fixers in the scaling of photosynthesis and WUE with leaf N. By clarifying the mechanism by which N fixers achieve and benefit from high WUE, our results further the understanding of global N fixer distributions.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Leaf nitrogen affects photosynthesis and water use efficiency similarly in nitrogen-fixing and non-fixing trees |
| Series title | Journal of Ecology |
| DOI | 10.1111/1365-2745.14194 |
| Volume | 111 |
| Issue | 11 |
| Year Published | 2023 |
| Language | English |
| Publisher | Wiley |
| Contributing office(s) | Forest and Rangeland Ecosystem Science Center |
| Description | 15 p. |
| First page | 2457 |
| Last page | 2471 |
| Google Analytic Metrics | Metrics page |