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, i.e., 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 vs 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 were 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-/belowground functional traits and C dynamics. Different tree
species may have employed contrasting strategies to adapt to the solar
spectral composition in their habitats.