Dear Mr. Wood,
Here are the answers to your three questions:
A factor that causes this area to be tundra is that the sun isn't hitting it at a direct angle so it's colder or tundra.
The factors will change with a warmer climate because there will be less carbon for the plants to grow.
There are no large trees in this tundra area because the temperature is too low for the decomposers to live to support the trees.
-Sydney Period: 6