During the winter, animated incoming and outgoing radiation happens on the ground, day and night, both of deciduous forest and of tillage, but it happens on the crown surface in the cace of needle leaf forest.
The radiation comes to appear on the surface of the crown, as deciduous trees become leafy.
Therefore defoliation means deciduous trees prove apt to be origin of cold current, because of radiation and nonconduction over the ground.
The enclosure of needle leaf trees is much more warmer than that of the grass or the deciduous trees especially in the night-time temperature goes down. The needle leaf trees forest in the course of cold current, which holds cold current in check, brings about the effect of keeping warm to a great extent on the lee of those trees belt.
The investigator reports; within the enclosure it is warmer, by 1°C to 4°C, than the outer, across the lee as far as the length of 12 times the height of a tree.
The efficacious extension of keeping warmth reaches maximum when the wind blows at a right angle against the wood-belt, while the efficacy decreases as the wind shifts to the direction of bevel.
At the piedmont district with high damage from frost, a measure to cut off or mitigate its suffering should be set up, by forming a needle leaf trees belt.