Types of tree lines There are several types of tree lines defined in ecology and geology : MISC@1 tree line The highest elevation that sustains trees ; higher up , it is too cold or snow cover persists for too much of the year , to sustain trees .

There are several types of tree lines defined in ecology and geology : MISC@2 tree-line The farthest north in the LOCATION@1 that trees can grow ; farther north , it is too cold . Alpine tree-line The highest height where trees grow : higher up , it is too cold , or snow covers the ground for too much of the year .
