What determines what type of biome can exist in a region?

The climate

Explanation:

The development and existence of any type of biome is directly dependent on the climate conditions. The areas that have warm climate throughout the whole year and lot of precipitation are enabling the development of the tropical rainforest biomes. The areas that have hot and dry climates are providing the conditions for the existence of the desert biomes. The places that have changes of seasons are enabling the development of the temperate biomes, and the places that are very cold and dry are suitable for the development of the arctic biomes. The climate is detrimental for the development of each biome as it affects the temperature, humidity, precipitation, which in turn results in the development of certain types of soil, vegetation, and animals that can exist in those conditions. The climate is the defining factor, but it also has to be taken in consideration that the climate depends on other factors that have to be mentioned, like the latitude, elevation, geography of the area, ocean currents, air masses etc.

make   gliitsh plesea   !

yes, because even though a theory has a  lot of evidence to support it, it is not always true