The reading passage is about three hypotheses of the declining population of yellow cedar that is a species of tree in northwestern North America. However, the lecturer rejects these hypotheses and says that these hypotheses are not convening.
Firstly, the reading passage claims that insect parasites especially beetle larvae can be one of the causes that the yellow cedar decline because the beetle larvae eat the wood but the lecturer states that healthy yellow cedars are resistant against insect parasites because they saturated by kind of poison. Thus insects can damage only sick trees.
Secondly, the reading passage says that brown bears maybe damage the yellow cedar tree. The yellow cedar has a high sugar content and brown bears claw the cedars in order to eat the tree bark. While the lecturer rebuts this hypothesis and explains that threes are no bears in some areas like midland but the population of yellow cedar are still declining.
Finally, the reading passage says that because of changes of climate the roots of the yellow cedar are sensitive and they grow in late winter rather than in the early spring. So the cold nights of winter damage them. However, the lecturer says that in high elevation that the weather is colder than other place, population of the yellow cedar have not declined and there are more the yellow cedar trees there. Thus the climate changes is not blame.
The
reading
passage
is about three hypotheses of the declining population of yellow
cedar
that is
a species of
tree
in northwestern North America.
However
, the
lecturer
rejects these hypotheses and
says
that these hypotheses are not convening.
Firstly
, the
reading
passage
claims that insect parasites
especially
beetle larvae can be one of the causes that the yellow
cedar
decline
because
the beetle larvae eat the wood
but
the
lecturer
states that healthy yellow
cedars
are resistant against insect parasites
because
they saturated by kind of poison.
Thus
insects can damage
only
sick trees.
Secondly
, the
reading
passage
says
that brown bears maybe damage the yellow
cedar
tree
. The yellow
cedar
has a high sugar content and brown bears claw the
cedars
in order to eat the
tree
bark. While the
lecturer
rebuts this hypothesis and
explains
that threes are no bears in
some
areas like midland
but
the population of yellow
cedar
are
still
declining.
Finally
, the
reading
passage
says
that
because
of
changes
of climate the roots of the yellow
cedar
are
sensitive and
they grow in late winter
rather
than in the early spring.
So
the
cold
nights of winter damage them.
However
, the
lecturer
says
that in high elevation that the weather is colder than other place, population of the yellow
cedar
have not declined and there are more the yellow
cedar
trees
there.
Thus
the climate
changes
is not blame.