Why do deciduous treees lose their leaves in fall?

Answer 1

In botany, deciduous plants, principally trees and shrubs, are those that lose all of their foliage for part of the year. This process is called abscission. In some cases, the foliage loss coincides with winter in temperate or polar climates, while others lose their leaves during the dry season in climates with seasonal variation in rainfall. The converse of deciduous is evergreen; plants that are intermediate may be called semi-deciduous.
*Many deciduous plants flower during the period when they are leafless, as this increases the effectiveness of pollination. The absence of leaves improves wind transmission of pollen in the case of wind-pollinated plants, and increases the visibility of the flowers to insects in insect-pollinated plants. This strategy is not without risks, as the flowers can be damaged by frost, or in dry season areas, result in water stress on the plant. Nevertheless, by losing leaves in the cold winter days, plants can reduce water loss since most of the water would appear as ice, and there is much less branch and trunk breakage from glaze ice storms when leafless .
[Deciduous means "temporary" or "tending to fall off" (deriving from the Latin word decidere, to fall off). Generally broad-leaf trees including Maple, Oak, Elm, Aspen and Birch among others.]
please visit:
http://www.uah.edu/admin/Fac/grounds/DECTREES.htm
http://www.cfl.scf.rncan.gc.ca/IMFEC-IDECF/hosttrees/deciduous/index.html
http://www.ag.ndsu.edu/pubs/plantsci/trees/f436-1.htm

Answer 2

There are a couple of answers, but both relate to water. Leaves are photosynthesis factories that use solar energy to build energy-storing molecules out of Carbon dioxide and water. They use a lot of water for this, and must also use water to cool off (transpiration in plants is like sweating in humans - it cools things down).
If there's not much water available (dry season), the leaves will stop functioning and may overheat enough so the photosynthesis machinery breaks. In the cold season, there are two dangers: first, frozen water expands and crystallizes, and may break the container it's in (cells in the leaf); second, if the water is unavailable due to being frozen in the ground, and the wind is strong enough to "force" transpiration to take place (think of it as stripping water out of the leaves), then the leaves dry up and die.
Either way, it's too risky to try to run the leaf factories in low-water or frozen-water season, so deciduous trees basically shut down and hibernate until the seasonal conditions improve.
Evergreens use various methods to reduce water loss and reduce the risk of sap freezing, but they can still be damaged if the conditions are unusually severe. It's a risky strategy to stay active all year!

Answer 3

It is of course an adaptation to the winter. I read that it has mostly to do with the availability of water and the high evaporative losses that occur in the windy low humidity atmospheric conditions that are common in the winter. Evergreens have evolved a different strategy of dealing with this problem, i.e. they have evolved a thick waxy coating to lessen evaporation. Nevertheless, most evergreens drop a percentage of their leaves/needles in the fall, just like the so called deciduous plants.

Answer 4

Because that is nature. When deciduous trees lose their leaves, its because of rain, sun, wind, and stuff like that, that makes the leaves dry and fall off...It is very simple and easy to uunderstand....well once you do understand IT...lol anyways Have a good day...best of luck & wishes!!!

Answer 5

Because of shorter days, lower light levels, & colder weather the amount of energy produced by the leaves drops. It then takes more energy for the tree to keep and repair it's leaves over the Winter than it does just sacrificing them. Also, the fallen leaves insulate the roots from snow & ice.

Answer 6

"by losing leaves in the cold winter days, plants can reduce water loss since most of the water would appear as ice, and there is much less branch and trunk breakage from glaze ice storms when leafless"(Lemon 1961)