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Higher leaf nitrogen content is linked to tighter stomatal regulation of transpiration and more efficient water use across dryland trees
Author(s) -
Querejeta José Ignacio,
Prieto Iván,
Armas Cristina,
Casanoves Fernando,
Diémé Joseph S.,
Diouf Mayecor,
Yossi Harouna,
Kaya Bocary,
Pugnaire Francisco I.,
Rusch Graciela M.
Publication year - 2022
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.18254
Subject(s) - transpiration , water use efficiency , stomatal conductance , agronomy , photosynthesis , interspecific competition , biology , specific leaf area , water use , dominance (genetics) , environmental science , botany , biochemistry , gene
Summary The least‐cost economic theory of photosynthesis shows that water and nitrogen are mutually substitutable resources to achieve a given carbon gain. However, vegetation in the Sahel has to cope with the dual challenge imposed by drought and nutrient‐poor soils. We addressed how variation in leaf nitrogen per area (N area ) modulates leaf oxygen and carbon isotopic composition (δ 18 O, δ 13 C), as proxies of stomatal conductance and water‐use efficiency, across 34 Sahelian woody species. Dryland species exhibited diverging leaf δ 18 O and δ 13 C values, indicating large interspecific variation in time‐integrated stomatal conductance and water‐use efficiency. Structural equation modeling revealed that leaf N area is a pivotal trait linked to multiple water‐use traits. Leaf N area was positively linked to both δ 18 O and δ 13 C, suggesting higher carboxylation capacity and tighter stomatal regulation of transpiration in N‐rich species, which allows them to achieve higher water‐use efficiency and more conservative water use. These adaptations represent a key physiological advantage of N‐rich species, such as legumes, that could contribute to their dominance across many dryland regions. This is the first report of a robust mechanistic link between leaf N area and δ 18 O in dryland vegetation that is consistent with core principles of plant physiology.