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Coarse woody debris (CWD) is a term used in English-speaking countries for fallen dead trees and the remains of large branches on the ground in forests and in rivers or wetlands. Some prefer the term coarse woody habitat (CWH). A dead standing tree is known as a snag and provides many of the same functions as coarse woody debris. The minimum size required for woody debris to be defined as "coarse" varies by author, ranging from 2.5–20 cm (1–8 in) in diameter.
Since the 1970s, forest managers worldwide have been encouraged to allow dead trees and woody debris to remain in woodlands, recycling nutrients trapped in the wood and providing food and habitat for a wide range of organisms, thereby improving biodiversity. The amount of coarse woody debris is considered to be an important criterion for the evaluation and restoration of temperate deciduous forest. Coarse woody debris is also important in wetlands, particularly in deltas where woody debris accumulates.
The Old Dead Tree
The old dead tree stood
gnarled weather torn;
its limbs were now brittle.
What stories could it tell
of the centuries it had lived,
the passing lives it had seen,
and the storms it had weathered
when it was young and strong.
When its foliage was green
and gave shelter from the rain.
Now it stands bare and broken,
a sorry sight to be seen.
It must have been beautiful
when it was young
with its canopy of green,
and a nesting place for little birds
among its evergreen.
Now they only used it
as a resting place whenever they pass by.
The old dead tree,
which had seen so much life.
17 September 2008
David Harris
Source: Wikipedia