When wuthering winds create fluttering fields: plant canopies under diffuse and fluctuating light

Natural vegetation is exposed to highly dynamic light environments driven by wind-induced canopy motion, cloud cover, and atmospheric aerosols. These processes generate diffuse radiation and rapid irradiance fluctuations, ranging from sub-second windflecks to hour-long cloudflecks. This variability strongly regulates photosynthesis and transpiration, yet most vegetation models still assume static canopies and instantaneous responses.

At the ecosystem scale, we present long-term observations from a boreal Scots pine forest showing that productivity is most strongly related to the absolute amount of diffuse light rather than diffuse fraction alone. Enhanced ecosystem uptake across both shoots and forest-floor vegetation emphasizes that diffuse radiation not only reorganizes light distribution throughout the canopy but may also modify leaf-level photosynthesis through canopy-mediated effects.

Controlled-environment experiments under defined fluctuating or diffuse irradiance regimes reveal that developmental acclimation to light variability represents a physiological compromise. This trade-off between carbon gain and water loss under realistic light dynamics has direct implications for water-use efficiency and drought responses in a warming climate. In parallel, field measurements reveal order-of-magnitude differences in wind-driven canopy motion among wheat cultivars under comparable wind speeds. Light fluctuations are thus not solely imposed by the atmosphere but are co-determined by plant structure and biomechanics.

Finally, we present new analyses of cloudfleck properties derived from multi-year, high-frequency measurements, revealing cloud-driven spectral irradiance fluctuations in temperate and boreal forests. These data stress that diffuse and direct radiation differ fundamentally in both directionality and spectral composition, extending beyond a simple binary and challenging the traditional direct–diffuse dichotomy used in models. Dynamic light is not noise around a mean state but a fundamental driver of ecosystem function. Accounting for its temporal, structural, and spectral complexity is essential for realistic predictions of vegetation responses to climate change.