Why do mountains have tree lines?
Show answer & explanation
Answer: Temperature too cold for trees
Animals prevent tree growth — Wrong. While grazing animals can affect vegetation, tree lines are determined by climate (temperature), not animal activity.
Temperature too cold for trees ✓ — Correct! Tree lines mark the elevation where it's too cold for trees to grow. Above this altitude (~11,000 ft in temperate zones), low temperatures, short growing seasons, and frost prevent tree survival. Only alpine plants (grasses, shrubs) survive. The exact elevation varies by latitude—closer to sea level near poles, higher at equator!
Wind blows away all seeds — Wrong. High winds do stress trees at altitude (causing krummholz—twisted dwarf trees), but temperature is the main limiting factor for tree lines.
More Earth Science questions
- Why can a river turn orange downstream even if the strongest acidic water enters from one tiny spring along the bank?
- Why might two Arctic streams look similarly rusty but need different chemical diagnoses?
- Why can thawing permafrost make a stream more acidic instead of simply adding cold meltwater?
- In folded Appalachians, why can one rock layer become a ridge while its neighbor becomes a valley?
- Loose material moves downhill from a fresh fault scarp, rounding it. What sets the smoothing speed?
- Why can a long active fault affect more river basins than a short one?