are determined by temperature
On the wet end, tropical rain forest
requires high precipitation (more than a year) and temperatures and is dominated by trees.
Moderate rain characterizes mediterranean scrub
high temperatures during dry spells allow grasses to compete with trees.
Moderate moisture and temperature yields temperate forest and temperate grassland.
As moisture and temperature drop further, boreal forest
covers the landscape, dominated by conifers.
Very dry and very cold conditions support tundra
with low-growing vegetation and no trees.