Simplify the following text for a Grade 6 native English-speaking person.
Original: These do not reach exactly to the same elevation , nor are they often found growing together ; but their upper limit corresponds accurately enough to the change from a temperate to a colder climate that is further proved by a change in the presence of wild herbaceous vegetation .
Simplified: Their upper limit matches the change in climate which comes with increasing height . The change from a temperate to a colder climate is also shown true by a change in the wild flowering plant life .