Yes because of the lack of air temperature and lack of daylight
The giant sequoia trees do not stop growing completely but like most trees, they do cease to grow in the winter. This is due to a lack of nutrients needed to support the tree's growth.
to stop other plants growing near it
We could stop it by trying to stop the developing of urban areas, growing more trees and plants, and stop destroying the natural vegetation and forests.
Demeter was the goddess of plants. She would cause the plants to stop growing in winter when Pluto/Hades took her daughter to the Underworld.
timberline
no
It gets colder
never
we are stop the cutting of the trees and we are growth new plants and trees by dugging the trees
tree line
Most trees will grow back except conifers, they usually have a hard time growing back. Fast growing deciduous trees will almost always sprout back when you cut them.
There would be no trees above it. The Timberline is where the trees stop growing.