The soil surface is the habitat where atmosphere enter in contact
with soil determining particular environmental condition.
2.
In
relation to a plant the soil or ground surface ( the soil level) is
the zone where shoot system and root system meet to each other at
the collar.
The soil surface, with its topography and
characteristics (along with soil depth and texture) is one of
the most important abiotic factors determining features of
vegetation, so great is the importance to plants of the texture,
depth, and surface character of the soil that in every area of
adequate size there are differences in the vegetation which are
closely correlated with these conditions.
The soil surface can be both a heat reflecting and absorbing
layer that warms and cools in both seasonal and daily cycles.
During daylight hours, the radiant energy of the sun quick warms
the earth's surface including plants and soil.
In full sunlight, the soil surface can reach 65-75°C . This heat
can be radiated and reflected onto landscape plants causing
tremendous heat lesions that are usually first seen on the
south/south-west side of stems. The soil heating is affected by
surface colour and texture, insulation angle, cloudiness and
canopy coverage, this factors greatly modifies radiation
cooling/heating of the surface.
However, during the night the soil surface lose heat from the
surface by outgoing invisible radiation that escapes to the
space. As the earth's surface cools, it cools the air around it.
This results in a reversal of daytime conditions and is referred
to as a temperature inversion because warmer air is now located
above the cool air at the surface, this heat loss continues
until after sunrise. For this reason, minimum temperatures
usually occur in the early morning. A radiational dew or frost
typically occurs when winds are calm and skies are clear. Under
such conditions, an inversion may form because of rapid
radiational cooling at the surface. If a strong inversion forms,
temperatures aloft may become 10° C or higher than surface
temperatures. The thermic behaviour are, however, greatly
influenced by their location, temperature fluctuation are of
small amount in forest or city habitats and great in open desert
areas where it is normal to have very high day
temperatures along with very low night temperatures with not
infrequent surface frost.
