How does elevation effect a region ecosystem?

The higher in altitude the colder the temperature. Temp. drop 4°F every 1000 feet. That means that 75° at the bottom and 10000 feet up it will be 35°. 
This colder temp does affect plant growth but it also affects the soil which in turn affects plant growth. Mountain vegetation (depending on the elevation) is comparable to the vegetation in areas of high latitude. Areas found up in the northern regions are affected by the colder temp as are the soils - same happens in mountainous areas. 

You tend to see more evergreens and soils are more acidic and less rich (poor nutrients). You will also get your permafrosts. Eventually a treeline occurs - mountain tops become treeless as does the north arctic areas. You find mosses growing in and around the rocks with some shrubs whereever there is enough soil for the roots to take. 

"An increase in altitude, such as climbing a mountain is similar to heading north (in the northern hemisphere) plant and animal species will be similar at a mountain top to those which are further north. "Source(s):http://library.thinkquest.org/C007506/bi..

Ba population changes in response to a change in environment