Sunfleck
Encyclopedia
Sunflecks are brief increases in solar irradiance that occur in forest understories
when sunlight is able to directly reach the ground. They are caused by either wind moving branches 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
s that reach plants in the understory, and up to 35% of carbon fixation
. 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
(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 amongst forest types, 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.
Understory
Understory is the term for the area of a forest which grows at the lowest height level below the forest canopy. Plants in the understory consist of a mixture of seedlings and saplings of canopy trees together with understory shrubs and herbs...
when sunlight is able to directly reach the ground. They are caused by either wind moving branches 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
Photon
In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
s that reach plants in the understory, and up to 35% of carbon fixation
Carbon fixation
In biology, carbon fixation is the reduction of carbon dioxide to organic compounds by living organisms. The obvious example is photosynthesis. Carbon fixation requires both a source of energy such as sunlight, and an electron donor such as water. All life depends on fixed carbon. Organisms that...
. 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
Photosynthetically active radiation, often abbreviated PAR, designates the spectral range 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 or less with the range of light visible to...
(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 amongst forest types, generally the frequency and intensity of sunflecks decreases as tree height and the leaf area index
Leaf Area Index
Leaf Area Index The Global Climate Observing System defines LAI as "one half the total green leaf area per unit groundsurface area. On sloping surfaces, the LAI should be projected to the normal to the slope. LAI is expressed in terms of square meters of leaf per square meter of ground...
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.