Answer:
climate
Step-by-step explanation:
The main difference between biomes is caused by the climate.
A biome is generally considered to be a community of organisms who share the same climatic characteristics.
Climatic factors are limiting factors that dictate the distribution of species within the environment. These factors include precipitation, temperature, pressure, salinity, etc.
When different species are favored in different environments as a result of varying climatic factors, different communities of species and, hence, biomes result.