Sunflecks are brief increases in
solar irradiance
Solar irradiance is the power per unit area (surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument.
Solar irradiance is measured in watts per square metre (W/ ...
that occur in
understories of an ecosystem when sunlight is able to directly reach the ground. They are caused by either wind moving branches and/or leaves in the canopy or as the sun moves during the day. Although each sunfleck only last for seconds or minutes at a time, they can be responsible more than 80% of the
photon
A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they always ...
s that reach plants in the understory, and up to 35% of
carbon fixation
Biological carbon fixation or сarbon assimilation is the process by which inorganic carbon (particularly in the form of carbon dioxide) is converted to organic compounds by living organisms. The compounds are then used to store energy and as ...
. This makes them important sources of energy for plants in the understory of forests. The amount of energy that a sunfleck provides depends on their duration, size and shape and the intensity of
photosynthetically active radiation Photosynthetically active radiation (PAR) designates the spectral range (wave band) of solar radiation from 400 to 700 nanometers that photosynthetic organisms are able to use in the process of photosynthesis. This spectral region corresponds more o ...
(PAR), which itself depends on the arrangement of vegetation in the canopy and the position of the sun in the sky.
The abundance of sunflecks varies greatly both within and between ecosystems, generally the frequency and intensity of sunflecks decreases as tree height and the
leaf area index increase.
[
There is no clear distinction between sunflecks and sunpatches, although the latter tend to last for at least an hour and the intensity of PAR reaches the full level of sunlight, whereas the intensity of PAR in sunflecks rarely reaches this. Because the amount of diffuse sunlight reaching the forest floor varies depending on the type of forest, there is no way to quantify an intensity of direct sunlight that qualifies as a sunfleck.][
]
References
Forest ecology
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