Contrasting light demands determine the coordination of plants' non‐structural carbohydrates and economic strategy over the range of solar spectral composition

Non-structural carbohydrates (NSC) are critical mediators of plant adaptation to fluctuating light environments. They are tightly coordinated with plant economic strategy, that is, leaf economics spectrum (LES) and root economics spectrum (RES). However, the role of solar spectral composition in shaping the NSC pool of tree species and their relationships with LES and RES is poorly understood. We examined plant economic traits and NSC of two functional groups, light-demanding versus shade-tolerant tree seedlings, grown under five spectral-attenuation treatments: (1) control, transmitting 95% of solar radiation (CK); (2) attenuating ultraviolet (UV)-B radiation; (3) attenuating all UV radiation; (4) attenuating all UV radiation and blue light; (5) attenuating all UV, blue and green light. Short-wavelength regions (UV) had strong effects on plant economic traits and the NSC dynamic, irrespective of functional groups. Shade-tolerant species exhibited higher trait plasticity than light-demanding species. Coordination of NSC and economic traits differed between the two groups. Across treatments, leaf and root NSC was negatively correlated with LES for both groups, and with RES for light-demanding species, while they were positively correlated with RES for shade-tolerant species. A more tightly coordinated trait-NSC network was evident in light-demanding species, and UV-A radiation promoted the network tightness. These findings highlight the role of spectral composition in regulating the coordination between above-/below-ground functional traits and C dynamics. Different tree species may have employed contrasting strategies to adapt to the solar spectral composition in their habitats.