That is commonly referred to as a tree hollow.
The stem of the tree is called the trunk and the outermost part of the trunk is called the bark of the trunk.
The name of the stem of a plant is called a stalk. If it is soft it is a herbaceous Weak ones are called climbers, and swollen or broken ones are called galls.
knar
the base is the place where the leaf joins its stem
Tree rings. Each year, a new ring is formed in the secondary xylem of stem.
That is commonly referred to as a tree hollow.
The stem of the tree is called the trunk and the outermost part of the trunk is called the bark of the trunk.
The trunk of a tree is called a 'bole'.
The outside covering of a tree trunk is called bark.
rain and winds
The name of the stem of a plant is called a stalk. If it is soft it is a herbaceous Weak ones are called climbers, and swollen or broken ones are called galls.
trunk
The bole.
There are several animals that would dig a hole by a rotted tree trunk. Some common ones include mole, badgers, ground hogs and gophers among others.
It is normally called the tree's bark.
branch
knar