Tree islands are unique clusters of trees found in Glacier National Park, Montana, at the alpine treeline. Researchers studied the patterns and dynamics of these tree islands, which differ from the surrounding forest in terms of composition and function. They observed a transition from tall trees to stunted trees and eventually to tundra with sparse krummholz trees. Tree islands come in various sizes and can have different types of conifer growth. The study sheds light on how tree islands contribute to the landscape at the alpine treeline.