Why does snow melt around trees?: Information Roundup
After a heavy snow there is usually an open place around each tree. This is due to the fact that the trunk of the tree reflects sunlight and melts the snow. As a rule the temperature of snow itself is several degrees higher than the surrounding atmosphere. When the temperature of the air is below freezing the temperature of snow on the ground is generally from three to four degrees warmer than the air over it. Snow is composed of about nine-tenths air and only one-tenth water. A blanket of snow on unfrozen land—often called "the poor man's manure"—protects crops from winter kill by preventing the warmth of the ground from escaping.