Linda Burgan, age 9, of Charleston, west Virginia, for her question:

Why do trees shed their leaves in the winter?

In autumn, the woods lose their greenery and dress themselves in flowery garden colors. But the gaudy leaves soon change to withered brown and wearily fall from their branches. When winter Comes, the worn out leaves are piled in rustling carpets on the forest floor. There is, of course, a reason why many trees shed their leaves for the winter.

If you live near the snowy shoulders of a tall mountain, your trees keep their leaves all winter. They are feathery firs and whispering pines, velvety junipers and other Christmassy evergreens. These sturdy trees have tricks to cope with wintry weather. The lacy elms and the papery poplars do not. They must shed their dainty leaves before winter brings its chilly snows and icy frosts.

Leaves, of course, are made of boxy little cells. Living cells are filled with juicy sap. When this liquid sap freezes, it becomes solid ice. And ice Swells. It stretches the delicate little cells. Its dagger sharp edges rip and tear the fragile cell walls beyond repair. Later, when the ice melts, the leaves are withered and ruined.

The leaves of the evergreen firs and pines are protected from the icy attacks of wintry Weather. They are sturdy little needles with tough jackets and overcoats of wax to keep out the cold. Their living, sap filled cells are sealed inside these layers have weatherproof coverings. Evergreen needles can cope with the winter.

A summery oak does not have these protections from the wintry frost. ItsLeaves are wide and flat and papery thin. The living cells are near the surface,

Almost touching the air. When the wintry air blows frosty cold, the liquid sap in these dainty leaves would turn to daggers of cruel ice. The papery leaves would be ruined by the first blizzard.

The leaves of the ash and elm, the tall poplar and the drooping willow are all flat and paper thin. These trees start to break up the chemicals in their leaves at the end of summer. The valuable chemicals are moved inside the twigs and branches and the withered leaves fall from their perches. If these thin, fragile leaves were not shed, they would be ruined by winter's first frosty day.

The oak and the elm are called deciduous trees. They shed their leaves with the changing seasons. Elms and maples and other deciduous trees have flat, thin leaves with no protection from the winter frost. Evergreens also shed their leaves, and the floor of a pine forest is littered with crispy needles. But evergreen needles are Shed a few at a time as they grow old. Pines and firs are not deciduous trees because they do not shed all their leaves at the same time.