Leaf traits and leaf nitrogen shift photosynthesis adaptive strategies among functional groups and diverse biomes

Leaf functional traits profoundly impact the function of diverse-biomes under different environmental conditions. Thus, it is urgent to deeply understand how leaf traits and leaf nitrogen (N) develop photosynthesis adaptive-strategies across functional groups and biomes. We compiled information from previous studies on six diverse-biomes under different climates to determine the difference in functional groups (forbs, deciduous-shrubs, deciduous-trees, and evergreen-needle) and related traits: photosynthesis (Amass, Aarea), dark respiration (dRmass, dRarea), Nmass, Narea, leaf life-span (LL), specific leaf area (SLA), and diffusive conductance (Gs). Then, we used non-linear modeling to examine the A-dR responses to leaf N. Among the biomes, desert grass-shrubland (Colorado) and warm temperate forest (South Carolina) had lower Amass, Nmass with lower SLA, while humid temperate forest (North Carolina) displayed higher Amass, Nmass with higher SLA, indicating that species in desert grass-shrubland and warm temperate biomes adapt conservative strategies while humid temperate species adapt acquisitive strategies for leaf maintenance against limited N and climate conditions. Among functional groups, forbs had higher Amass, dRmass and Nmass, deciduous-shrubs and trees had intermediate Amass, dRmass, and Nmass, while evergreen-needle had lower Amass, dRmass with lower Nmass. Forbs had minimum storage N (Astore), deciduous-shrubs and trees had intermediate Astore, while evergreen-needle had the highest Astore. We concluded that forbs needed a minimum N-investment for leaf maintenance followed by deciduous and evergreen-needle. These results reveal that leaf N and leaf traits support adaptive-strategies for A-dR that regulate leaf maintenance and photosynthesis capacity under limited resources and environmental conditions.