What factor limits agriculture in the higher mountain zone to only potato and barley crops?

Answer;
The factor that limits agriculture in the higher mountain zone to only potato and barley crops is the Growing season, mostly Frost.

Explanation;
The upper limit of agriculture was represented by hardy crops such as potatoes and barley; extends from tierra fria. These hardy crops were able to survive   the climate of higher mountain zones. 

The answer would be cstep by step explanation: all of the other animals developed their features while the salamander was born with them

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