Extreme drought shifts phosphorus‐related leaf trait relationships without clearly altering pairwise scaling in grasslands

Leaf trait relationships can aid our understanding of plant adaptations and ecosystem functioning. With climate change driving an increase in the frequency and intensity of extreme environmental conditions, these relationships may be altered. However, the sensitivity of these relationships to extreme drought stress remains unclear.

To address this gap, we conducted an extreme drought experiment (66% reduction in growing‐season precipitation) across six grasslands in Inner Mongolia, including desert steppe, typical steppe and meadow steppe. For 32 herbaceous species, we measured specific leaf area (SLA), leaf nitrogen (N _mass ) and leaf phosphorus (P _mass ) under both drought and ambient conditions and explored potential shifts in their pairwise relationships. We also evaluated species‐level pairwise plasticity to uncover mechanisms underlying any changes.

Allometric relationships among N _mass –SLA, P _mass –SLA and P _mass –N _mass persisted under both environmental conditions. While extreme drought did not alter the slopes of these relationships, it significantly lowered the elevations (intercepts) of relationships between P _mass and both SLA and N _mass . The statistically similar slopes were associated with species‐level pairwise plasticity patterns that did not systematically diverge among species, whereas the downward shifts in elevation were associated with reduced species‐level phosphorus concentrations across most sites.

Synthesis . These results suggest that extreme drought primarily shifts phosphorus‐related leaf trait relationships rather than providing strong evidence for altered pairwise scaling among SLA, leaf nitrogen and leaf phosphorus. These findings highlight the importance of phosphorus‐related trait responses and species‐level plasticity for understanding leaf economic trait patterns under severe water stress.