Abstract: As a key functional trait affecting many physiological processes, leaf pH is closely related to other leaf traits at the local scale. Nevertheless, whether and how leaf pH is linked with other leaf functional traits across geographic scales remains unclear. A field survey in northern China was conducted to investigate the relationships between leaf pH and some key leaf structural (specific leaf area, SLA; leaf dry matter content, LDMC) and chemical traits (elemental concentrations; total dissolved solids, TDS; practical salinity), as well as the effects of environmental factors on these relationships. Our results showed that the trait coordination may vary in degree or direction across eco-geographic regions (arid vs. non-arid regions) and life-forms (woody vs. herbaceous plants). Generally, leaf pH was negatively related to SLA, but positively related to TDS and salinity. However, leaf pH and LDMC were negatively correlated in arid regions but positively correlated in non-arid regions; leaf pH covaried with N (similarly, with Ca, Mg and Na) in the same direction for both herbaceous and woody plants in arid regions, but not in non-arid regions. Climatic factors mainly influenced the relationships of leaf pH with leaf Ca and Fe concentrations, while soil factors mostly affected those with leaf P, Ca and Mn concentrations. Our findings highlight the divergent coordination between leaf pH and other leaf traits across life-forms and eco-geographic regions and may shed light on the in-depth understanding of the role of acid-base balance in plant eco-physiological processes and ecological adaptation over biogeographic scales.

Key words: arid and humid regions, macro-ecology, herbaceous and woody plants, plant functional traits, plant pH, trait coordination, trait coordinated relationships