Radiation and thermal microclimate in tree shelter

Single-tree shelters are used to protect trees, but they greatly affect tree growth, largely because of their internal microclimate. The shelter walls have a PAR transmissivity from 35% to 60%, depending on the beam angle. Far infrared radiation is trapped in the shelter creating various temperature gradients. During the night, the internal air temperature is colder than outside air. During the day the internal temperature is much warmer than the outside air. Leaf temperature is warmer than the air temperature only when the sun's beam is directed to the leaf. The wall temperature is usually lower than inside air temperature. Therefore, leaves are not able to transpire and condensation appears on the inner wall of the shelter. This increases the energy surplus within the shelter. (c) 2008 Elsevier B.V. All rights reserved.