Light - Agroecology: The Ecology of Sustainable Food Systems - page 48

FIGURE 4.4 Concentrated weed growth on the north-facing side of a furrow. Because this side of the furrow received less light
than the south-facing side, it remained cooler and moister, favoring the development of these particular weeds.

V EGETATION C ANOPY S TRUCTURE

between leaves as wind moves the canopy and as the sun
moves across the sky. Some of this additional light enters
as diffused sidelighting (sky light), and other light enters
directly from the sun and forms sunflecks (small, usually
mobile spots of unobstructed light). From an agricultural
perspective, it is important to understand how light varies
inside of the vegetative canopy, especially when dealing
with diverse intercropped systems, agroforestry systems,
and even the management of noncrop plant species in the
interior of a cropping system.

The average leaf allows the transmission of about 10% of
the light that strikes its surface. Depending on the structure
of the canopy of the vegetation, leaves will overlap one
another to a greater or lesser extent, adding to the density
of the canopy and reducing both the quantity and quality
of light that eventually reaches the soil surface. At the
same time, however, considerable sunlight may pass
between leaves or through the spaces that become available