Fields of a thousand shimmers: canopy architecture determines high-frequency light fluctuations

Wind-induced movement in the canopy produces rapid fluctuations in irradiance, called windflecks'. They create a dynamic environment for photosynthesis that bears little resemblance to the stable controlled conditions under which plants are typically measured. We recorded time series of irradiance to assess the diversity of windfleck properties (intensity, duration, frequency, clustering, and spectral composition) in canopies of four crops and five tree species. We also measured traits associated with leaf morphology and canopy architecture, which could be associated with canopy-specific differences in windflecks. Distinct features of windfleck properties were identified both between and among crop and tree canopy. Windflecks in crops were generally more intense and longer, and baseline irradiance was much higher than even the peak irradiance during a windfleck in a forest. The change in spectral composition during a windfleck was species-specific. Overall, irradiance fluctuations were less frequent and less intense in tall canopies and with increased depth from the canopy. Our systematic exploration of how canopy structure dictates light dynamics provides new insight into windfleck creation. Coupled with progress in elucidation of the mechanisms of photosynthetic induction, this knowledge should improve our capacity to model canopy ecophysiology and understand light use efficiency in shade.

Automated summary

Wind-induced movement in the canopy creates dynamic fluctuations in irradiance called windflecks, which significantly differ in intensity, duration, frequency, clustering, and spectral composition among crop and tree canopies. Windflecks in crops are generally more intense and long-lasting compared to those in forests, and the change in spectral composition during a windfleck is species-specific. Irradiance fluctuations are less frequent and less intense in taller canopies and deeper within the canopy. Understanding the influence of canopy structure on light dynamics and windfleck creation is crucial for modeling canopy ecophysiology and light use efficiency in shade.